bluuebunny/crossref_metadata_2025 huggingface dataset:
Intensity discrimination in the presence of random-frequency, multicomponent maskers and broadband noise
Authors: Neff Donna L. , Jesteadt Walt
Published: October 2005

This study examined the effects of multicomponent, random-frequency maskers and broadband-noise maskers on intensity discrimination at 1000 Hz. Maskers and signals were 200 ms, presented simultaneously. In the first set of conditions, thresholds were measured for the detection of a 1000-Hz tone in the presence of 40 or 60 dB SPL random-frequency or noise maskers, with extensive training of listeners with the random-frequency masker to assure stable effects of masker-frequency uncertainty. The random-frequency maskers had two, six, or ten components chosen at random from a large frequency range (300–3000 Hz, excluding a 160-Hz band around 1000 Hz). For these maskers, performance across the four listeners was very similar, showing large effects of masker-frequency uncertainty. For noise maskers, performance matched predictions for energy-based masking. In the second and third sets of conditions, intensity discrimination was measured at 1000 Hz for pedestals ranging from 40 to 80 dB SPL, first in isolation and then in the presence of the maskers. The pattern of results for intensity discrimination in quiet showed the expected near miss to Weber’s Law, but poorer performance than typically observed. The addition of broadband-noise maskers had little effect on performance. However, random-frequency maskers degraded performance in nearly all conditions, with the size of the effect dependent on the level of the pedestal relative to the masker. Considering the pedestal as a tonal masker, the data were fitted with various models of combined masking. A simple power-law model provided excellent fits, with exponents ranging from 0.24 to 0.35 for the multicomponent maskers, but 1.0 (linear) for the noise. The results support models positing that the effects of individual maskers undergo nonlinear transformation before they are added, independent of the mechanisms which produce these effects. Because random-frequency maskers presumably produce informational (uncertainty-based) masking, the nonlinearity in this case appears central rather than peripheral.
Across-channel processes in frequency modulation detection
Authors: Furukawa Shigeto , Moore Brian C. J.
Published: October 2005

This study investigated how well listeners combine information about frequency changes imposed on different carrier frequencies. The pattern of frequency change over time was either identical or different across carriers; this is referred to as ‘‘coherence.’’ Psychometric functions were measured for the detection of frequency modulation (FM) imposed on two sinusoidal carriers, with frequencies 1100 and 2000 Hz. The modulation of each carrier was equally detectable, as determined in preliminary experiments. A continuous pink noise background was used to mask the outputs of auditory filters tuned between the two carrier frequencies. In experiment 1, the carriers were gated synchronously with 1-s steady-state duration and 50-ms raised-cosine ramps. One cycle of 5-Hz sinusoidal FM was used, the carrier having unmodulated ‘‘fringes’’ on either side of this. The FM on the two carriers was symmetrically located about the temporal center of the stimulus. The relative timing of the onset of FM (lag) between the two carriers was systematically varied. When the FM overlapped partially or completely in time across carriers, detectability for coherent FM was often better than for incoherent FM, especially for lag=0, and was also often better than predicted on the assumption that information about the FM on the two carriers was extracted independently and combined optimally. When the FM did not overlap in time across the carriers, the detectability of the combined FM was generally equal to or lower than the value predicted on this assumption. In experiment 2, the long steady-state fringes before and after the modulation were removed, and the modulation always started at the same time for the two carriers. The modulation rate was either 2.5, 5, or 10 Hz. Again, performance for coherent FM was generally better than for incoherent FM. The effect of FM coherence was greater at the lowest modulation rate but did not vary markedly with the number of modulation cycles. The detectability of coherent FM was well above the value predicted on the assumption that information from the two carrier frequencies was processed independently and combined optimally. These results indicate the auditory system has higher sensitivity to FM when the FM is coherent across carriers. Possible models to account for the results are discussed.
Effects of stimulus duration on the amplitude difference limen for vibrotaction
Authors: Gescheider G. A. , Zwislocki J. J. , Rasmussen A.
Published: October 2005

Vibrotactile amplitude difference limens (DLs) were measured by the continuous pedestal and gated pedestal methods. In both cases, the relative DL decreased as a function of the intensity of the stimulus and the results, in most cases, could be described as a near miss to Weber’s law. DLs measured by the continuous pedestal method were found to decrease substantially as a function of increases in stimulus duration over a range of 12 to 1000 ms. In contrast, DLs measured by the gated pedestal method were only slightly affected by changes in stimulus duration. It was concluded that the process of temporal summation can manifest itself in reducing the size of the DL in the continuous pedestal, but not the gated pedestal, paradigm.
Detection of frequency modulation at low modulation rates: Evidence for a mechanism based on phase locking
Authors: Moore Brian C. J. , Sek Aleksander
Published: October 2005

These experiments tested the hypothesis that detection of frequency modulation (FM) at very low rates depends mainly on temporal information (phase locking to the carrier) for carriers below about 5 kHz, whereas FM detection at higher rates (10 Hz and above) depends mainly on changes in the excitation pattern (a ‘‘place’’ mechanism). In experiment 1, thresholds for detecting FM were measured for a wide range of carrier frequencies (0.25–6 kHz) for modulation rates, fm, of 2, 5, 10, and 20 Hz. Thresholds were determined when FM only was present and when the carriers in both intervals of a forced-choice trial were amplitude modulated at the same rate as the FM with a modulation index of 0.333. The phase of the amplitude modulation (AM) relative to the FM was randomly selected on each trial, in order to disrupt cues for FM detection based on changes in the excitation pattern. For carrier frequencies up to 4 kHz, the deleterious effect of the added AM increased with increasing fm. For the 6-kHz carrier, the deleterious effect was independent of fm. In experiment 2, psychometric functions were measured for detecting combined FM and AM of a 1-kHz carrier, with fm=2 Hz, as a function of the relative phase of the modulators. The modulation depths for AM and FM were chosen so that each would be equally detectable if presented alone. This was done both in quiet and in the presence of noise designed to mask either the lower or the upper side of the excitation pattern. In contrast to earlier results obtained with fm=10 Hz [Moore and Sek, J. Acoust. Soc. Am. 96, 741–751 (1994)], only small effects of relative modulator phase were found. Experiment 3, was similar to experiment 2, except that all measurements were done in quiet, and carrier frequencies of 0.25, 1.0, and 6.0 kHz were used. There were no effects of relative modulator phase for the 0.25-kHz carrier, small effects for the 1-kHz carrier, and large effects for the 6-kHz carrier. The pattern of results is consistent with the hypothesis that both temporal and place mechanisms are involved in FM detection. The temporal mechanism dominates for carriers below about 4 kHz, and for very low modulation rates. The place mechanism dominates for high carrier frequencies, and for lower carrier frequencies when stimuli are frequency modulated at high rates.
Detection of auditory ‘‘events’’ based on amplitude and frequency modulation
Authors: Sek Aleksander , Moore Brian C. J.
Published: October 2005

These experiments examined the ability of subjects to detect auditory ‘‘events’’ composed of a brief modulation in the temporal center of an otherwise steady sinusoid. In experiment 1, psychometric fluctuations were measured for detecting either amplitude modulation (AM) or frequency modulation (FM) composed of a single cycle of a raised-cosine function (either positive going or negative going); the modulation frequency was 10 Hz, so the event lasted for 100 ms. Then, psychometric functions were measured for stimuli with both AM and FM, using pairs of values of AM and FM that were equally detectable; pairs were always modulated in the same direction, so a positive amplitude excursion went together with a positive frequency excursion. Performance was compared with the ‘‘reference’’ detectability that would be predicted from the optimal combination of independent sources of information. When the AM and FM were synchronous, detectability was better than the reference detectability. When the FM was delayed by 100 ms relative to the AM, detectability was mostly equal to or less than the reference detectability. The better performance with synchronous AM and FM is consistent with an explanation based on an excitation-pattern model. Experiment 2 was similar to experiment 1, except that the event was a single cycle of sinusoidal modulation starting at 0° phase or 180° phase. When the AM and FM were synchronous and in phase, detectability was better than the reference detectability. When the AM was delayed by 200 ms relative to the FM or had opposite starting phase, detectability was close to or below the reference detectability. However, for the case where the delay was 100 ms and the modulation had the same starting phase for AM and FM, detectability was better than the reference detectability. A control experiment using two successive cycles of either AM or FM showed a similar, but slightly smaller, effect. It appears that detectability can be enhanced when two successive events form a regular temporal pattern.
Spectral cues for sound localization in cats: Effects of frequency domain on minimum audible angles in the median and horizontal planes
Authors: Huang Aileen Y. , May Bradford J.
Published: October 2005

Rice et al. [Hear. Res. 58, 132–152 (1992)] classified directional properties of the cat’s head-related transfer function (HRTF) into three frequency domains. Low frequencies (<5 kHz) display a broad azimuth-sensitive spectral peak that establishes interaural level differences, mid frequencies (5–18 kHz) are marked with a single deep spectral notch that changes in frequency as a function of both azimuth and elevation, and high frequencies (18–50 kHz) exhibit a complex pattern of peaks and notches that shows extensive but less systematic changes with sound location. Spectral cues conveyed by the mid frequencies of broadband sounds are important in tasks that require cats to identify the actual location of acoustic stimuli [Huang and May, J. Acoust. Soc. Am. (in press)]. The present study investigates how directional cues conveyed by the mid- and high-frequency spectrum of the HRTF influence the cat’s ability to discriminate between sound locations. Thresholds for spatial acuity were measured as minimum audible angles (MAAs) [Mills, J. Acoust. Soc. Am. 30, 237–246 (1958)] at positive azimuths in the interaural horizontal plane and at positive and negative elevations in the median vertical plane. The frequency domain of the noise burst had little effect on MAAs in the horizontal plane, but removal of high-frequency spectral information significantly increased thresholds at positive and negative elevations in the median plane. These results suggest that cats are sensitive to directional properties of the HRTF at frequencies above 18 kHz and may use this information to detect small changes in sound source elevation.
Phase independence of pitch produced by narrow-band sounds
Authors: Dai Huanping , Nguyen Quang , Kidd Gerald , Feth Lawrence L. , Green David M.
Published: October 2005

Three listeners matched the pitch of a simple tone to that of narrow-band complex signals having different phases. The pitch matches were independent of the phases; the frequency of the simple tone approximately equaled the center of gravity of the power spectrum of each complex signal. This result is inconsistent with a model that calculates the pitch of a waveform as the average of instantaneous frequency weighted by the envelope of the waveform.
Lateralization of a perturbed harmonic: Effects of onset asynchrony and mistuning
Authors: Hill Nicholas I. , Darwin C. J.
Published: October 2005

The lateralization paradigm of Trahiotis and Stern [C. Trahiotis and R. M. Stern, J. Acoust. Soc. Am. 86, 1285–1293 (1989)] was extended to investigate the influence of a spectrally flanking complex on the lateral position of a perturbed harmonic. When a complex tone consisting of harmonics 2 through 8 of 100 Hz was presented with an interaural time difference (ITD) of 1.5 ms, the complex was heard on the leading side (experiment 1). However, when the 500-Hz component had a later onset time than the other components (experiments 1 and 2) or was mistuned (experiment 3), it was perceived to be in a different lateral position to the complex. The complex still maintained a residual influence on the lateralization of the pure tone even for the largest asynchrony used (experiment 4). Experiment 5 confirmed that the lateralization of the tonal complex was consistent with the aggregation of binaural information across frequency. The results suggest that across-frequency integration of interaural-timing information is influenced by onset-asynchrony and harmonicity.
Intensity discrimination as a function of stimulus level with electric stimulation
Authors: Nelson David A. , Schmitz Jennifer L. , Donaldson Gail S. , Viemeister Neal F. , Javel Eric
Published: October 2005

Difference limens (DLs) for changes in electric current were measured from multiple electrodes in each of eight cochlear-implanted subjects. Stimuli were 200-μs/phase biphasic pulse trains delivered at 125 Hz in 300-ms bursts. DLs were measured with an adaptive three-alternative forced-choice procedure. Fixed-level psychometric functions were also obtained in four subjects to validate the adaptive DLs. Relative intensity DLs, specified as Weber fractions in decibels {10 log(ΔI/I)} for standards above absolute threshold, decreased as a power function of stimulus intensity relative to absolute threshold {ΔI/I=β(I/I0)α} in the same manner as Weber fractions for normal acoustic stimulation reported in previous studies. Exponents (α) of the power function for electric stimulation ranged from −0.4 to −3.2, on average, an order of magnitude larger than exponents for acoustic stimulation, which range from −0.07 to −0.11. Normalization of stimulus intensity to the dynamic range of hearing resulted in Weber functions with similar negative slopes for electric and acoustic stimulation, corresponding to an 8-dB average improvement in Weber fractions across the dynamic range. Sensitivity to intensity change {10 log β} varied from −0.42 to −13.5 dB compared to +0.60 to −3.34 dB for acoustic stimulation, but on average was better with electric stimulation than with acoustic stimulation. Psychometric functions for intensity discrimination yielded Weber fractions consistent with adaptive procedures and d′ was a linear function of ΔI. Variability among repeated Weber-fraction estimates was constant across dynamic range. Relatively constant Weber fractions across all or part of the dynamic range, observed in some subjects, were traced to the intensity resolution limits of individual implanted receiver/stimulators. DLs could not be accurately described by constant amplitude changes, expressed as a percentage of dynamic range {ΔA(%DR)}. Weber fractions from prelingually deafened subjects were no better or worse than those from postlingually deafened subjects. The cumulative number of discriminable intensity steps across the dynamic range of electric hearing ranged from as few as 6.6 to as many as 45.2. Physiologic factors that may determine important features of electric intensity discrimination are discussed in the context of a simple, qualitative, rate-based model. These factors include the lack of compressive cochlear preprocessing, the relative steepness of neural rate-intensity functions, and individual differences in patterns of neural survival.
The vowel-sequence illusion: Intrasubject stability and intersubject agreement of syllabic forms
Authors: Warren Richard M. , Healy Eric W. , Chalikia Magdalene H.
Published: October 2005

Earlier studies have found that listeners presented with a loud and clear repeating sequence of brief steady-state vowels typically report hearing two voices with distinctly different timbres repeating different syllables that either are English words or occur in English words. One of the simultaneous voices is generally based upon frequencies below, and the other above, the ‘‘crossover frequency’’ at approximately 1500 Hz that divides normal speech into regions contributing equally to intelligibility. It has been hypothesized that the lack of linguistic content halts the processing of vowel sequences at the syllabic level, and that the spectral splitting corresponding to the concurrent voices reflects a mechanism for independent processing of different frequency regions that can lead to increased intelligibility under difficult listening conditions. The present study employed twelve randomly selected arrangements of the same six 70-ms vowels, and it was determined that: (1) individuals reported the same perceptual organizations the following week; (2) insertion of a brief silent gap between restatements of a sequence resulted in reports of similar (and occasionally identical) syllables by different listeners hearing the same sequence; and (3) when two listeners’ responses differed, they could nevertheless identify the particular vowel sequences corresponding to each other’s verbal forms. Spectrograms of vowel sequences were compared with time-aligned spectrograms of a speaker’s synchronous production of the forms as they were being heard, and some common features of the acoustic patterns were noted. It is suggested that vowel sequences provide a reliable and useful tool for probing aspects of the perceptual organization of speech sounds that are normally obscured by additional linguistic processing.
Fundamental frequency effects on thresholds for vowel formant discrimination
Authors: Kewley-Port Diane , Li Xiaofeng , Zheng Yijian , Neel Amy T.
Published: October 2005

The present experiments examined the effect of fundamental frequency (F0) on thresholds for the discrimination of formant frequency for male vowels. Thresholds for formant-frequency discrimination were obtained for six vowels with two fundamental frequencies: normal F0 (126 Hz) and low F0 (101 Hz). Four well-trained subjects performed an adaptive tracking task under low stimulus uncertainty. Comparisons between the normal-F0 and the low-F0 conditions showed that formants were resolved more accurately for low F0. These thresholds for male vowels were compared to thresholds for female vowels previously reported by Kewley-Port and Watson [J. Acoust. Soc. Am. 95, 485–496 (1994)]. Analyses of the three F0 sets demonstrated that formant thresholds were significantly degraded for increases both in formant frequency and in F0. A piece-wise linear function was fit to each of the three sets of ΔF thresholds as a function of formant frequency. The shape of the three parallel functions was similar such that ΔF was constant in the F1 region and increased with formant frequency in the F2 region. The capability for humans to discriminate formant frequency may therefore be described as uniform in the F1 region (<800 Hz) when represented as ΔF and also uniform in the F2 region when represented as a ratio of ΔF/F. A model of formant discrimination is proposed in which the effects of formant frequency are represented by the shape of an underlying piece-wise linear function. Increases in F0 significantly degrade overall discrimination independently from formant frequency.
Genetic and Epigenetic Modeling of the Origins of Multidrug-Resistant Cells in a Human Sarcoma Cell Line
Authors: Chen Kevin G. , Wang Yan C. , Schaner Marci E. , Francisco Brian , Durán George E. , Juric Dejan , Huff Lyn M. , Padilla-Nash Hesed , Ried Thomas , Fojo Tito , Sikic Branimir I.
Published: October 2005

The origin of drug-resistant cells in human cancers has been a fundamental problem of cancer pharmacology. Two major contrasting hypotheses (genetics versus epigenetics) have been proposed to elucidate the mechanisms of acquired drug resistance. In this study, we answer these fundamental questions through investigation of the genetic and epigenetic pathways that control the origin of ABCB1 (MDR1) gene activation with acquired multidrug resistance in drug-sensitive human sarcoma (MES-SA cells). The genetic and epigenetic bases of this selected activation involve the initiation of transcription at a site 112 kb upstream of the ABCB1 proximal promoter (P1) in the drug-resistant cells. This activation was associated with a chromatin-remodeling process characterized by an increase in acetylated histone H3 within a 968-bp region 5′ of the ABCB1 upstream promoter. These alterations provide both genetic and epigenetic susceptibility for ABCB1 expression in drug-resistant cells. Complete activation of the ABCB1 gene through the coding region was proposed by interactions of selected trans-alterations or epigenetic changes on the ABCB1 proximal promoter, which occurred during initial drug exposure. Thus, our data provide evidence for a major genomic alteration that changes the chromatin structure of the ABCB1 upstream promoter via acetylation of histone H3 initiating ABCB1 activation, further elucidating the genetic and epigenetic bases that determine chemotherapeutic response in drug-resistant derivatives of MES-SA cells.
A Gene Expression Signature of Genetic Instability in Colon Cancer
Authors: Giacomini Craig P. , Leung Suet Yi , Chen Xin , Yuen Siu Tsan , Kim Young H. , Bair Eric , Pollack Jonathan R.
Published: October 2005

Genetic instability plays a central role in the development and progression of human cancer. Two major classes of genetic instability, microsatellite instability (MSI) and chromosome instability (microsatellite stable; MSS), are best understood in the context of colon cancer, where MSI tumors represent ∼15% of cases, and compared with MSS tumors, more often arise in the proximal colon and display favorable clinical outcome. To further explore molecular differences, we profiled gene expression in a set of 18 colon cancer cell lines using cDNA microarrays representing ∼21,000 different genes. Supervised analysis identified a robust expression signature distinguishing MSI and MSS samples. As few as eight genes predicted with high accuracy the underlying genetic instability in the original and in three independent sample sets, comprising 13 colon cancer cell lines, 61 colorectal tumors, and 87 gastric tumors. Notably, the MSI signature was retained despite genetically correcting the underlying instability, suggesting the signature reflects a legacy of the tumor having arisen from MSI, rather than sensing the ongoing state of MSI. Our findings support a model in which MSI and MSS preferentially target different genes and pathways in cancer. Further, among the MSI signature genes, our findings implicate a role of elevated metallothionein expression in the clinical behavior of MSI cancers.
β-Tubulin Mutations Are Associated with Resistance to 2-Methoxyestradiol in MDA-MB-435 Cancer Cells
Authors: Gökmen-Polar Yesim , Escuin Daniel , Walls Chad D. , Soule Sharon E. , Wang Yuefang , Sanders Kerry L. , LaVallee Theresa M. , Wang Mu , Guenther Brian D. , Giannakakou Paraskevi , Sledge George W.
Published: October 2005

2-Methoxyestradiol is an estradiol metabolite with significant antiproliferative and antiangiogenic activity independent of estrogen receptor status. To identify a molecular basis for acquired 2-methoxyestradiol resistance, we generated a stable 2-methoxyestradiol-resistant (2ME2R) MDA-MB-435 human cancer cell line by stepwise exposure to increasing 2-methoxyestradiol concentrations. 2ME2R cells maintained in the presence of the drug and W435 cells maintained in the absence of the drug showed 32.34- to 40.07-fold resistance to 2-methoxyestradiol. Cross-resistance was observed to Vinca alkaloids, including vincristine, vinorelbine, and vinblastine (4.29- to 6.40-fold), but minimal resistance was seen to colchicine-binding agents including colchicine, colcemid, and AVE8062A (1.72- to 2.86-fold). No resistance was observed to paclitaxel and epothilone B, polymerizing agents (0.89- to 1.14-fold). Genomic sequencing identified two different heterozygous point mutations in the class I (M40) isotype of β-tubulin at amino acids 197 (Dβ197N) and 350 (Kβ350N) in 2ME2R cells. Tandem mass spectrometry confirmed the presence of both wild-type and the mutant β-tubulin in 2ME2R cells at the protein level. Consistently, treatment of parental P435 cells with 2-methoxyestradiol resulted in a dose-dependent depolymerization of microtubules, whereas 2ME2R cells remained unaffected. In contrast, paclitaxel affected both cell lines. In the absence of 2-methoxyestradiol, 2ME2R cells were characterized by an elevated level of detyrosination. Upon 2-methoxyestradiol treatment, levels of acetylated and detyrosinated tubulins decreased in P435 cells, while remaining constant in 2ME2R cells. These results, together with our structure-based modeling, show a tight correlation between the antitubulin and antiproliferative effects of 2-methoxyestradiol, consistent with acquired tubulin mutations contributing to 2-methoxyestradiol resistance.
Radiosensitivity Enhancement by Celecoxib, a Cyclooxygenase (COX)-2 Selective Inhibitor, via COX-2–Dependent Cell Cycle Regulation on Human Cancer Cells Expressing Differential COX-2 Levels
Authors: Shin You Keun , Park Ji Sun , Kim Hyun Seok , Jun Hyun Jung , Kim Gwi Eon , Suh Chang Ok , Yun Yeon Sook , Pyo Hongryull
Published: October 2005

To characterize the radiation-enhancing effects on human cancer cells and underlying mechanisms of celecoxib, a cyclooxygenase (COX)-2 selective inhibitor, and to ascertain whether its effects are COX-2 dependent. Clonogenic cytotoxicity assays and radiation survival assays after treatment with celecoxib ± radiation were done on four human cancer cell lines that expressed differential COX-2 levels. Stably COX-2 knocked down or overexpressed cell lines were developed, and clonogenic assays, apoptosis assays, or cell cycle change measurements were conducted after treatment with celecoxib ± radiation. Prostaglandin E2 (PGE2) was applied to medium after treatment with celecoxib ± radiation to determine whether the radiation-enhancing effect associated with celecoxib results from reduced generation of prostaglandin. Celecoxib's radiation-enhancing effect was observed in COX-2–expressing A549 and NCI-H460 cells but was not observed in the COX-2 nonexpressing MCF-7 and HCT-116 cells. Celecoxib's radiation-enhancing effects in A549 cells were shown to disappear after the administration of COX-2 knocked down. In contrast, the HCT-116 cells were radiosensitized by celecoxib after being transfected with COX-2 expression vector. The addition of PGE2 after treatment with celecoxib ± radiation had no significant effects on celecoxib's radiation-enhancing effects in A549 and COX-2 transfected HCT-116 cells. Radiation-induced G2-M arrest was enhanced and sustained in the COX-2–overexpressing cells compared with that seen in COX-2 low-expressing cells. Celecoxib or NS-398 effected no changes or attenuated radiation-induced G2-M arrest in the COX-2–overexpressing cells but further enhanced the radiation-induced G2-M arrest in the COX-2 low-expressing cells. Celecoxib's radiation-enhancing effects seem to occur in a COX-2 expression-dependent manner in the cancer cells. This effect does not seem to be the result of reduced PGE2 generation. Celecoxib may exert an inhibitory effect on enhanced radiation-induced G2-M arrest in the COX-2–overexpressing cells, which may allow the arrested cells to enter mitosis and die after radiation, but may also further enhance radiation-induced G2-M arrest in the COX-2 low-expressing cells, by virtue of another mechanism.
Down-regulation of Integrin α2 Surface Expression by Mutant Epidermal Growth Factor Receptor (EGFRvIII) Induces Aberrant Cell Spreading and Focal Adhesion Formation
Authors: Ning Yan , Zeineldin Reema , Liu Yueying , Rosenberg Martina , Stack M. Sharon , Hudson Laurie G.
Published: October 2005

Elevated expression or activity of the epidermal growth factor receptor (EGFR) is common in ovarian cancer and is associated with poor patient prognosis. A naturally occurring EGFR mutation termed variant III (EGFRvIII) has been detected in many human tumors, including those of the ovary. This mutant receptor does not bind EGF; however, it is constitutively active as detected by receptor dimerization, autophosphorylation, and stimulation of signal transduction cascades. To identify the consequences of EGFRvIII expression in ovarian tumor cells, we introduced EGFRvIII into the epithelial ovarian cancer cell line OVCA 433. The EGFRvIII-transfected cells displayed a motile phenotype, defects in cell spreading, and decreased integrin α2 protein expression as detected by Western blot analysis and flow cytometry. Inhibition of EGFRvIII catalytic activity using the EGFR-selective tyrphostin AG1478 restored integrin α2 expression within 4 to 8 hours after treatment. The modulation of integrin α2 expression corresponded to marked changes in the actin cytoskeleton as detected by redistribution of filamentous-actin. Furthermore, focal adhesions were evident only when EGFRvIII activity was inhibited. Together, these findings suggest that expression of the constitutively active mutant EGFRvIII promotes changes in cell shape and focal adhesion formation, mediated in part through specific modulation of integrin α2 expression and function. We conclude that EGFR-activating mutations, such as EGFRvIII, in ovarian cancer may contribute to a more aggressive disease.
Lysophosphatidic Acid Acyltransferase-β Is a Prognostic Marker and Therapeutic Target in Gynecologic Malignancies
Authors: Springett Gregory M. , Bonham Lynn , Hummer Amanda , Linkov Irina , Misra Dipika , Ma Chia , Pezzoni Gabriella , Di Giovine Stefano , Singer Jack , Kawasaki Hiroaki , Spriggs David , Soslow Robert , Dupont Jakob
Published: October 2005

Lysophosphatidic acid, the substrate for lysophosphatidic acid acyltransferase β (LPAAT-β), is a well-studied autocrine/paracrine signaling molecule that is secreted by ovarian cancer cells and is found at elevated levels in the blood and ascites fluid of women with ovarian cancer. LPAAT-β converts lysophosphatidic acid to phosphatidic acid, which functions as a cofactor in Akt/mTOR and Ras/Raf/Erk pathways. We report that elevated expression of LPAAT-β was associated with reduced survival in ovarian cancer and earlier progression of disease in ovarian and endometrial cancer. Inhibition of LPAAT-β using small interfering RNA or selective inhibitors, CT32521 and CT32228, two small-molecule noncompetitive antagonists representing two different classes of chemical structures, induces apoptosis in human ovarian and endometrial cancer cell lines in vitro at pharmacologically tenable nanomolar concentrations. Inhibition of LPAAT-β also enhanced the survival of mice bearing ovarian tumor xenografts. Cytotoxicity was modulated by diacylglycerol effectors including protein kinase C and CalDAG-GEF1. LPAAT-β was localized to the endoplasmic reticulum and overexpression was associated with redistribution of protein kinase C-α. These findings identify LPAAT-β as a potential prognostic and therapeutic target in ovarian and endometrial cancer.
Fusokine Interleukin-2/Interleukin-18, a Novel Potent Innate and Adaptive Immune Stimulator with Decreased Toxicity
Authors: Acres Bruce , Gantzer Murielle , Remy Christelle , Futin Nicolas , Accart Nathalie , Chaloin Olivier , Hoebeke Johan , Balloul Jean-Marc , Paul Stéphane
Published: October 2005

To redress the immune imbalances created by pathologies such as cancer, it would be beneficial to create novel cytokine molecules, which combine desired cytokine activities with reduced toxicities. Due to their divergent but complementary activities, it is of interest to combine interleukin-2 (IL-2) and IL-18 into one recombinant molecule for immunotherapy. Evaluation of a fusokine protein that combines murine IL-2/IL-18 shows that it is stable, maintains IL-2 and IL-18 bioactivities, has notably reduced IL-2 associated toxicities, and has a novel lymphocyte-stimulating activity. An adeno-viral expression system was used to explore the biology of this “fusokine”. Inclusion of the IL-18 prosequence (proIL-18) increases the expression, secretion, and potency of this fusokine. In vivo gene transfer experiments show that Ad-IL-2/proIL-18 dramatically outdoes Ad-IL-2, Ad-proIL-18, or the combination of both, by inducing high rates of tumor rejection in several murine models. Both innate and adaptive effector mechanisms are required for this antitumor activity.
A Blocking Antibody to Nerve Growth Factor Attenuates Skeletal Pain Induced by Prostate Tumor Cells Growing in Bone
Authors: Halvorson Kyle G. , Kubota Kazufumi , Sevcik Molly A. , Lindsay Theodore H. , Sotillo Julio E. , Ghilardi Joseph R. , Rosol Thomas J. , Boustany Leila , Shelton David L. , Mantyh Patrick W.
Published: October 2005

Prostate cancer is unique in that bone is often the only clinically detectable site of metastasis. Prostate tumors that have metastasized to bone frequently induce bone pain which can be difficult to fully control as it seems to be driven simultaneously by inflammatory, neuropathic, and tumorigenic mechanisms. As nerve growth factor (NGF) has been shown to modulate inflammatory and some neuropathic pain states in animal models, an NGF-sequestering antibody was administered in a prostate model of bone cancer where significant bone formation and bone destruction occur simultaneously in the mouse femur. Administration of a blocking antibody to NGF produced a significant reduction in both early and late stage bone cancer pain–related behaviors that was greater than or equivalent to that achieved with acute administration of 10 or 30 mg/kg of morphine sulfate. In contrast, this therapy did not influence tumor-induced bone remodeling, osteoblast proliferation, osteoclastogenesis, tumor growth, or markers of sensory or sympathetic innervation in the skin or bone. One rather unique aspect of the sensory innervation of bone, that may partially explain the analgesic efficacy of anti-NGF therapy in relieving prostate cancer–induced bone pain, is that nearly all nerve fibers that innervate the bone express trkA and p75, and these are the receptors through which NGF sensitizes and/or activates nociceptors. The present results suggest that anti-NGF therapy may be effective in reducing pain and enhancing the quality of life in patients with prostate tumor–induced bone cancer pain.
Enhancement of Cancer Radiation Therapy by Use of Adenovirus-Mediated Secretable Glucose-Regulated Protein 94/gp96 Expression
Authors: Liu Shanling , Wang He , Yang Zhonghui , Kon Takashi , Zhu Jiangao , Cao Yiting , Li Fang , Kirkpatrick John , Nicchitta Christopher V. , Li Chuan-Yuan
Published: October 2005

Tumor-derived glucose-regulated protein 94 (GRP94/gp96) has shown great promise as a tumor vaccine. However, current protein-based approaches require the availability of large quantities of tumor tissue, which are often not possible. In addition, the efficacy of immunotherapy is often not ideal when used alone. In this study, we explored the therapeutic efficacy of a combined GRP94/gp96-based genetic immunotherapy and radiation therapy strategy in the weakly immunogenic and highly metastatic 4T1 murine mammary cancer model. An adenovirus encoding a modified, secretable form of GRP94 gene (AdsGRP94) was constructed and evaluated in various antitumor experiments. Lethally irradiated, virus-infected cells were used as vaccines. Adenoviral vectors were also injected directly into tumors in conjunction with tumor irradiation. Vaccination with lethally irradiated, AdsGRP94-infected 4T1 cells completely prevented subsequent tumor growth from challenge inoculations of as many as 107 cells per mouse. In established tumor models, vaccinations alone had minimal effect on local and metastatic tumor growth. However, when vaccination was combined with radiation therapy and i.t. AdsGRP94 injections, local tumor growth and pulmonary metastasis were markedly inhibited. In some cases, complete tumor regression was observed. In these cases, the mice were resistant to subsequent tumor challenge and remain tumor free up to 10 months after initial therapy. Our results indicate that combined AdsGRP94-based immunotherapy and radiation therapy may be a potentially effective strategy for cancer treatment.
Less Efficient G2-M Checkpoint Is Associated with an Increased Risk of Lung Cancer in African Americans
Authors: Zheng Yun-Ling , Loffredo Christopher A. , Alberg Anthony J. , Yu Zhipeng , Jones Raymond T. , Perlmutter Donna , Enewold Lindsey , Krasna Mark J. , Yung Rex , Shields Peter G. , Harris Curtis C.
Published: October 2005

Cell cycle checkpoints play critical roles in the maintenance of genomic integrity. The inactivation of checkpoint genes by genetic and epigenetic mechanisms is frequent in all cancer types, as a less-efficient cell cycle control can lead to genetic instability and tumorigenesis. In an on-going case-control study consisting of 216 patients with non–small cell lung cancer, 226 population-based controls, and 114 hospital-based controls, we investigated the relationship of γ-radiation-induced G2-M arrest and lung cancer risk. Peripheral blood lymphocytes were cultured for 90 hours, exposed to 1.0 Gy γ-radiation, and harvested at 3 hours after γ-radiation treatment. γ-Radiation-induced G2-M arrest was measured as the percentage of mitotic cells in untreated cultures minus the percentage of mitotic cells in γ-radiation-treated cultures from the same subject. The mean percentage of γ-radiation-induced G2-M arrest was significantly lower in cases than in population controls (1.18 versus 1.44, P < 0.01) and hospital controls (1.18 versus 1.40, P = 0.01). When dichotomized at the 50th percentile value in combined controls (population and hospital controls), a lower level of γ-radiation-induced G2-M arrest was associated with an increased risk of lung cancer among African Americans after adjusting for baseline mitotic index, age, gender, and pack-years of smoking [adjusted odd ratio (OR), 2.25; 95% confidence interval (95% CI), 0.97-5.20]. A significant trend of an increased risk of lung cancer with a decreased level of G2-M arrest was observed (Ptrend = 0.02) among African Americans, with a lowest-versus-highest quartile adjusted OR of 3.74 (95% CI, 0.98-14.3). This trend was most apparent among African American females (Ptrend < 0.01), with a lowest-versus-highest quartile adjusted OR of 11.75 (95% CI, 1.47-94.04). The results suggest that a less-efficient DNA damage–induced G2-M checkpoint is associated with an increased risk of lung cancer among African Americans. Interestingly, we observed a stronger association of DNA damage–induced G2-M arrest and lung cancer among African Americans when compared with Caucasians. If replicated, these results may provide clues to the exceedingly high lung cancer incidence experienced by African Americans.
Misregulated Wnt/β-Catenin Signaling Leads to Ovarian Granulosa Cell Tumor Development
Authors: Boerboom Derek , Paquet Marilene , Hsieh Minnie , Liu Jinsong , Jamin Soazik P. , Behringer Richard R. , Sirois Jean , Taketo Makoto M. , Richards JoAnne S.
Published: October 2005

Misregulation of the Wnt/β-catenin signaling pathway is a hallmark of several forms of cancer. Components of the Wnt/β-catenin pathway are expressed in ovarian granulosa cells; nevertheless, its potential involvement in granulosa cell tumorigenesis has not been examined. To this end, human (n = 6) and equine (n = 18) granulosa cell tumors (GCT) were analyzed for β-catenin expression by immunohistochemistry. Unlike granulosa cells of normal ovaries, most (15 of 24) GCT samples showed nuclear localization of β-catenin, suggesting that activation of the Wnt/β-catenin pathway plays a role in the etiology of GCT. To confirm this hypothesis, Catnbflox(ex3)/+; Amhr2cre/+ mice that express a dominant stable β-catenin mutant in their granulosa cells were generated. These mice developed follicle-like structures containing disorganized, pleiomorphic granulosa by 6 weeks of age. Even in older mice, these follicle-like lesions grew no larger than the size of antral follicles and contained very few proliferating cells. Similar to corpora lutea, the lesions were highly vascularized, although they did not express the luteinization marker Cyp11a1. Catnbflox(ex3)/+; Amhr2cre/+ females were also found to be severely subfertile, and fewer corpora lutea were found to form in response to exogenous gonadotropin compared with control mice. In older mice, the ovarian lesions often evolved into GCT, indicating that they represent a pretumoral intermediate stage. The GCT in Catnbflox(ex3)/+; Amhr2cre/+ mice featured many histopathologic similarities to the human disease, and prevalence of tumor development attained 57% at 7.5 months of age. Together, these studies show a causal link between misregulated Wnt/β-catenin signaling and GCT development and provide a novel model system for the study of GCT biology.
Epithelial to Mesenchymal Transition Is a Determinant of Sensitivity of Non–Small-Cell Lung Carcinoma Cell Lines and Xenografts to Epidermal Growth Factor Receptor Inhibition
Authors: Thomson Stuart , Buck Elizabeth , Petti Filippo , Griffin Graeme , Brown Eric , Ramnarine Nishal , Iwata Kenneth K. , Gibson Neil , Haley John D.
Published: October 2005

Treatment of second- and third-line patients with non–small-cell lung carcinoma (NSCLC) with the epidermal growth factor receptor (EGFR) kinase inhibitor erlotinib significantly increased survival relative to placebo. Whereas patient tumors with EGFR mutations have shown responses to EGFR inhibitors, an exclusive role for mutations in patient survival benefit from EGFR inhibition is unclear. Here we show that wild-type EGFR–containing human NSCLC lines grown both in culture and as xenografts show a range of sensitivities to EGFR inhibition dependent on the degree to which they have undergone an epithelial to mesenchymal transition (EMT). NSCLC lines which express the epithelial cell junction protein E-cadherin showed greater sensitivity to EGFR inhibition in vitro and in xenografts. In contrast, NSCLC lines having undergone EMT, expressing vimentin and/or fibronectin, were insensitive to the growth inhibitory effects of EGFR kinase inhibition in vitro and in xenografts. The differential sensitivity of NSCLC cells with epithelial or mesenchymal phenotypes to EGFR inhibition did not correlate with cell cycle status in vitro or with xenograft growth rates in vivo, or with total EGFR protein levels. Cells sensitive to EGFR inhibition, with an epithelial cell phenotype, did exhibit increased phosphorylation of EGFR and ErbB3 and a marked increase in total ErbB3. The loss of E-cadherin and deregulation of β-catenin associated with EMT have been shown to correlate with poor prognosis in multiple solid tumor types. These data suggest that EMT may be a general biological switch rendering non–small cell lung tumors sensitive or insensitive to EGFR inhibition.
Critical Function for ADAM9 in Mouse Prostate Cancer
Authors: Peduto Lucie , Reuter Victor E. , Shaffer David R. , Scher Howard I. , Blobel Carl P.
Published: October 2005

ADAM9 is a membrane-anchored metalloprotease that is markedly up-regulated in several human carcinomas. Here, we show that ADAM9 is similarly up-regulated in mouse models for prostate, breast, and intestinal carcinoma. To assess whether ADAM9 is critical for the pathogenesis of prostate carcinoma, one of the most common cancers in men, we evaluated how loss of ADAM9 affects tumorigenesis in W10 mice, a mouse model for this disease. In the absence of ADAM9, most tumors in 50-week-old W10 mice were well differentiated, whereas littermate controls expressing wild-type ADAM9 had predominantly poorly differentiated, and in some cases significantly larger, tumors. Moreover, gain-of-function experiments in which ADAM9 was overexpressed in mouse prostate epithelium resulted in significant abnormalities, including epithelial hyperplasia at 4 to 6 months of age, and prostatic intraepithelial neoplasia after 1 year. A potential underlying mechanism for the role of ADAM9 in prostate cancer emerged from cell-based assays: ADAM9 can cleave and release epidermal growth factor and FGFR2iiib from cells, both of which have pivotal functions in the pathogenesis of this disease. Taken together, these results suggest that ADAM9 contributes to the pathogenesis of prostate cancer and potentially also other carcinomas, raising the possibility that ADAM9 might be a good target for antitumor drugs.
Bovine Herpesvirus 4 Induces Apoptosis of Human Carcinoma Cell Lines In vitro and In vivo
Authors: Gillet Laurent , Dewals Benjamin , Farnir Frédéric , de Leval Laurence , Vanderplasschen Alain
Published: October 2005

The idea of using oncolytic viruses for the treatment of cancers was proposed a century ago. During the last two decades, viruses able to replicate specifically in cancer cells and to induce their lysis were identified and were genetically modified to improve their viro-oncolytic properties. More recently, a new approach consisting of inducing selective apoptosis in cancer cells through viral infection has been proposed; this approach has been called viro-oncoapoptosis. In the present study, we report the property of bovine herpesvirus-4 (BoHV-4) to induce, in vitro and in vivo, apoptosis of some human carcinomas. This conclusion relies on the following observations: (a) In vitro, BoHV-4 infection induced apoptosis of A549 and OVCAR carcinoma cell lines in a time- and dose-dependent manner. (b) Apoptosis was induced by the expression of an immediate-early or an early BoHV-4 gene, but did not require viral replication. (c) Cell treatment with caspase inhibitors showed that apoptosis induced by BoHV-4 relied mainly on caspase-10 activation. (d) Infection of cocultures of A549 or OVCAR cells mixed with human 293 cells (in which BoHV-4 does not induce apoptosis) showed that BoHV-4 specifically eradicated A549 or OVCAR cancer cells from the cocultures. (e) Finally, in vivo experiments done with nude mice showed that BoHV-4 intratumoral injections reduced drastically the growth of preestablished A549 xenografts. Taken together, these results suggest that BoHV-4 may have potential as a viro-oncoapoptotic agent for the treatment of some human carcinomas. Moreover, further identification of BoHV-4 proapoptotic gene(s) and the cellular pathways targeted by this or these gene(s) could lead to the design of new cancer therapeutic strategies.