Nuclear Medicine and Biology 42 (2015) 475–481

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Nuclear Medicine and Biology
journal homepage: www.elsevier.com/locate/nucmedbio

A strategy for improving FDG accumulation for early detection ofmetastasis from primary pancreatic cancer: Stimulation of the Warburg
effect in AsPC-1 cells
Masato Ogura a,b, Naoto Shikano b,⁎, Syuichi Nakajima b, Junichi Sagara c, Naoto Yamaguchi c,
Kentaro Kusanagi b, Yuya Okui a, Asuka Mizutani a, Masato Kobayashi a,d, Keiichi Kawai a,daDivision of Health Science, Graduate School of Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, Ishikawa 920-0942, Japan
Department of Radiological Sciences, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-machi, Inashiki-gun, Ibaraki 300-0394, Japanc
Center for Medical Sciences, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-machi, Inashiki-gun, Ibaraki 300-0394, Japand
Biomedical Imaging Research Center, University of Fukui, 23-3 Matsuokashimoaizuki, Eiheiji-cho, Yoshida-gun, Fukui 910-1193, Japanba r t i c l e

i n f oArticle history:
Received 12 December 2014
Received in revised form 25 December 2014
Accepted 29 December 2014
Keywords:
FDG
Ascites tumor cells
Glycolysis
6-Phosphofructo-1-kinase
Hexosea b s t r a c t
Introduction: Early detection and/or prediction of metastasis provide more prognostic relevance than local recurrence. Direct spread into the peritoneum is frequently found in pancreatic cancer patients, but positron emission
tomography (PET) with 2-deoxy-2-ﬂuoro-D-glucose (FDG) is not useful for identifying such metastasis. We investigated a method to enhance FDG accumulation using AsPC-1 human ascites tumor cells.
Methods: 14C-FDG accumulation was assessed under the following conditions: 1) characteristics of 14C-FDG
transport were examined using phloridzin, a Na +-free buffer, and various hexoses, and 2) accumulation of
14
C-FDG was measured in cells that were pretreated with hexose for various time periods, and activity of
6-phosphofructo-1-kinase (PFK-1) was assayed.
Results: 14C-FDG transport into AsPC-1 cells was mediated primarily by a Na+-independent transport mechanism. Aldohexoses such as D-glucose, D-mannose, and D-galactose inhibited 14C-FDG transport. Cells pretreatedwith D-glucose, D-mannose, or D-fructose exhibited augmented 14C-FDG accumulation. Pretreatment with higher
concentrations of D-glucose or D-fructose tended to increase PFK-1 activity.
Conclusions: Very little information has been published about the association between PFK-1 and FDG accumulation, and we conﬁrmed the impacts of various hexoses on the activity of PFK-1 and FDG accumulation in AsPC-1
cells. Clarifying the relevance of PFK-1 in FDG accumulation will contribute to developing new features of FDGPET, because PFK-1 is the main regulator of glycolysis.
© 2015 Elsevier Inc. All rights reserved.

1. Introduction
Pancreatic cancer (PC) is highly aggressive, and its mortality rates
have been approximately stable in many European countries, the USA,
Japan, and Australia over the last few years [1]. Retrospective analysis
has demonstrated that a dramatic change in surgical resectability andpatient survival occurs as the size of the PC tumor increases from20 mm to 30 mm [2,3]. Moreover, PC patient survival is dependent on
distant metastasis rather than local recurrence, and therefore, early detection and/or prediction of metastasis provide more prognostic relevance than local recurrence [4].
Direct spread into the peritoneum is not uncommon in PC patients,
but positron emission tomography (PET) with 2-deoxy-2-ﬂuoro-Dglucose (FDG) is not useful for identifying such metastasis, especially
microscopic peritoneal dissemination (b 10 mm) and intraperitoneal
seeding, because of the low concentration of cancer cells [5–7].
⁎ Corresponding author. Tel.: +81 29 888 4000x6574.
E-mail address: sikano@ipu.ac.jp (N. Shikano).
http://dx.doi.org/10.1016/j.nucmedbio.2014.12.017
0969-8051/© 2015 Elsevier Inc. All rights reserved.

In acute hyperglycemia, FDG transport may decrease because ofcompetition between FDG and D-glucose [8]. Numerous reports examining the relationship between FDG accumulation and D-glucose havebeen published [9–13]. In contrast, whether other hexoses are involvedin FDG accumulation has yet to be determined, either in vivo or in vitro.
A future objective of ours is to be able to assess peritoneal metastasiswith FDG-PET. Thus, in the present study, we investigated a method toenhance FDG accumulation using AsPC-1 human ascites tumor cells
from a PC patient.
2. Materials and methods
2.1. Materials
Reagent grade D-glucose, L-glucose, and D-allose were purchasedfrom Wako Pure Chemical Industries, Ltd. (Osaka, Japan), and D-altrose,
D-gulose, D-sorbose, and D-tagatose were purchased from Kanto ChemicalCo., Inc. (Tokyo, Japan). D-mannose, D-galactose, D-fructose, L-fructose,
D-fructose 6-phosphate (D-Fru-6-P), aldolase, α-glycerophosphate

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M. Ogura et al. / Nuclear Medicine and Biology 42 (2015) 475–481

dehydrogenase-triosephosphate isomerase, and the other chemicals
were purchased from Sigma-Aldrich Japan (Tokyo, Japan). The radiolabeled
compounds 14C-FDG, 14C-maltose, and 14C-inulin were purchased from
American Radiolabeled Chemicals Co. (St. Louis, MO, USA).
2.2. Cell culture
AsPC-1 human ascites tumor cells were obtained from the American
Type Culture Collection (Rockville, MD, USA). Cells were incubated in
Dulbecco’s Modiﬁed Eagle’s Medium (Sigma-Aldrich Japan) supplemented with L-glutamine (2 mM ﬁnal concentration) and fetal bovine
serum (10% ﬁnal concentration; Nichirei Biosciences Inc., Tokyo,
Japan) at 37 °C in a 10% CO2 atmosphere. Cells were maintained in
25-cm 2 cell culture ﬂasks (Nalge Nunc International, Roskilde,
Denmark) and were passaged every 4 days using 0.1% trypsin and
0.04% EDTA. AsPC-1 cells (5 × 105 cells per dish) were seeded in a plastic
culture dish (60-mm diameter; Nalge Nunc International) and wereused in the experiments described below 4 days after seeding. At thetime experiments were initiated, the cell density was approximately
2.5 × 10 6 cells/dish. Before experiments, the culture medium was removed from the dish, and the cells were rinsed once with Dulbecco’s
phosphate-buffered saline (D-PBS; Sigma-Aldrich Japan).
2.3. Characteristics of 14C-FDG transport into AsPC-1 cells
14

C-FDG accumulation experiments were performed according topreviously reported methods, with modiﬁcations [14,15]. For timecourse experiments, AsPC-1 cells were rinsed with D-PBS and then incubated with 2 ml D-PBS containing 14C-FDG (14C-FDG D-PBS; 9.25 kBq/dish) at 37 °C for a speciﬁc period (15 to 180 min). The 14C-FDG DPBS was then removed by aspiration, and the cells were immediately
rinsed twice with 5 ml ice-cold D-PBS. Next, the cells were lysed overnight in 2 ml 0.2 M NaOH, and the radioactivity in the NaOH extract
was assayed using a Tri-carb 2910TR liquid scintillation analyzer(PerkinElmer Japan Co., Ltd., Kanagawa, Japan). Similar experiments
using radiolabeled 14C-maltose D-PBS (9.25 kBq/dish) or 14C-inuline
D-PBS (9.25 kBq/dish) were performed as described above.
To examine the characteristics of 14C-FDG transport into AsPC-1
cells, we carried out experiments using 14C-FDG D-PBS in 1 mM
phloridzin or Na +-free buffer. Phloridzin is a speciﬁc inhibitor of the
Na +-dependent glucose transporter family [16]. In experiments with
the Na +-free buffer, NaCl and Na2HPO4 in the D-PBS were replacedwith the same concentrations of choline chloride and K2HPO4,
respectively. Cells were incubated in phloridzin-containing buffer or
Na +-free buffer for 60 min, and then the radioactivity present in thecell extract was measured as described above. To suppress 14C-FDG
entry via transporters, cells were kept on ice during all incubations.
2.4. Competitive inhibition of 14C-FDG transport
To conﬁrm the competitive effects of hexoses on 14C-FDG transport into AsPC-1 cells, the following modiﬁcations were incorporated into competitive inhibition experiments: 1) 14 C-FDG D-PBS
contained one of the following 11 hexoses (D-/L-glucose, D-mannose,
D-allose, D-galactose, D-altrose, D-gulose, D-/L-fructose, D-sorbose, or
14
D -tagatose) at a concentration of 1 mM, and 2)
C-FDG D-PBS
contained an indicated concentration (0.01 to 100 mM) of one selecthexose (D-/L-glucose, D-mannose, D-galactose, or D-fructose). Afterincubation in 14C-FDG D-PBS for 60 min, the radioactivity present
in the cell extract was measured as described above.
2.5. 14C-FDG accumulation in pretreated AsCP-1 cells
To examine the effect of pretreating AsPC-1 cells with hexoses on
C-FDG accumulation, the following modiﬁcations were incorporated
into the pretreatment experiments: 1) D-PBS contained one of the14

following 11 hexoses (D-/L-glucose, D-mannose, D-allose, D-galactose,or D-tagatose) at aconcentration of 1 mM, and 2) D-PBS contained an indicated concentration (0.01 to 100 mM) of one select hexose (D-/L-glucose, D-mannose,
D-galactose, or D-fructose). Cells were incubated in one of the above
D-PBS solutions for 60 min, and then immediately rinsed twice with
D-PBS and incubated with 14C-FDG D-PBS for 60 min. Following cell
lysis, the radioactivity present in the cell extract was measured as described above. A pretreatment time of 60 min was chosen because incubations less than 60 min produced no augmentation of FDG
accumulation in our preliminary experiments.
D-altrose, D-gulose, D-/L-fructose, D-sorbose,

2.6. 6-Phosphofructo-1-kinase activity in pretreated AsPC-1 cells
For the time-course experiments, AsPC-1 cells were exposed to 1 or
100 mM D-glucose or D-fructose for a speciﬁc period (15 to 60 min),after which the cells were immediately rinsed twice with D-PBS and removed from the culture dish with a rubber policeman.
To measure the 6-phosphofructo-1-kinase (PFK-1) activity in cells
pretreated with various hexoses, cells were incubated at 37 °C for
60 min in D-PBS containing D-/L-glucose, D-mannose, D-galactose, or
D-/L-fructose at concentrations ranging from 1 to 100 mM, and then removed from the culture dish with a rubber policeman.
The collected cells were homogenized on ice in extraction buffer
comprised of 50 mM Tris-phosphate (pH 8.0), 0.2 mM ethylenediamine
tetraacetic acid (EDTA), 90 mM potassium ﬂuoride, 10 mM dithiothreitol (DTT), and 1 mM phenylmethylsulfonyl ﬂuoride [17]. The homogenates were centrifuged at 29,000 × g for 30 min at 4 °C using a himac
CS100FX ultracentrifuge (Hitachi Koki Co. Ltd., Tokyo, Japan).
PFK-1 activity in the supernatants was measured as previously described [14]. The reaction mixture contained 50 mM Tris–HCl(pH 8.0), 1 mM EDTA, 2 mM MgCl2, 2 mM DTT, 5 mM (NH4)2SO4,
1 mM D-Fru-6-P, 1.2 mM adenosine 5′-triphosphate, 0.2 mM
reduced nicotinamide adenine dinucleotide (NADH), 0.8 U/ml aldolase,
0.8 U/ml α-glycerophosphate dehydrogenase, and 8.7 U/ml
triosephosphate isomerase in a ﬁnal volume of 1 ml. The reaction was
initiated by addition of the extract (30 μl), and the absorbance at
340 nm was measured at 37 °C using a UV-2200 spectrophotometer(Shimadzu Corp., Kyoto, Japan). PFK-1 activity was calculated as follows: 1 mol D-fructose 1,6-bisphosphate (D-Fru-1,6-P2) = 2 mol
NADH consumed. The NADH content in the homogenates was calculated using the absorption coefﬁcient of NADH (6220 M−1•cm−1) [18].
2.7. Statistical analysis
Values obtained in each experiment are presented as the mean ±SD. Groups were compared using ANOVA followed by Dunnett’s posthoc analysis. Differences were considered statistically signiﬁcant at
P b 0.05.
3. Results
3.1. Characterization of 14C-FDG accumulation in non-pretreated
AsPC-1 cells
14
C-FDG transport into AsPC-1 cells was time dependent during theinitial 60 min, and was saturated at approximately 35% of the administered dose by 120 min (Fig. 1a). No 14C-inulin was detected in the cells,
indicating that no error was present in the methodology thatwould have resulted in accumulation of radioactivity not associatedwith 14C-FDG. In addition, radiolabeled 14C-maltose did not accumulate
in cells. Maltose must be enzymatically metabolized (e.g., maltase in thesmall intestine) before entry into cells.
The accumulation of 14C-FDG after 60 min in various conditions isshown in Fig. 1b. Low temperature suppressed total 14C-FDG accumulation to 35% of the control, suggesting that FDG transport isM. Ogura et al. / Nuclear Medicine and Biology 42 (2015) 475–481

477

Fig. 1. Characteristics of 14C-FDG accumulation in AsPC-1 cells. (a) Time course of 14C-FDG (♦), 14C-maltose (▲), and 14C-inulin (○) accumulation. Accumulation (% of administered dose) is
plotted against time after administration. (b) 14C-FDG transport in AsPC-1 cells under various conditions. Black columns and white columns represent 14C-FDG accumulation in cells incubated in D-PBS and in Na+-free buffer, respectively. Values represent the mean ± SD. n = 4–8. *P b 0.05; n.s., not signiﬁcant.

carrier mediated. Transport of 14 C-FDG via Na +-independent andNa +-dependent mechanisms was approximately 40% and 25%, respectively. In the presence of phloridzin, a Na +-dependent glucose
transporter inhibitor, 14C-FDG accumulation was reduced by approximately 25% relative to the control. 14C-FDG transport into
AsPC-1 cells is thus mediated primarily by a Na +-independent transport mechanism.

3.2. Competitive inhibition of 14C-FDG transport
The results of competitive inhibition experiments of 14C-FDG transport by D-/L-hexoses (1 mM) are shown in Fig. 2a. Three aldohexoses including D-glucose, D-mannose, and D-galactose inhibited 14C-FDG
accumulation. As L-glucose is not transported via glucose transporter
proteins and does not inhibit 2-deoxyglucose transport [19,20],

Fig. 2. Competitive inhibition of 14C-FDG transport by various hexoses. The effect of 1 mM aldohexose (a) or ketohexose (b). 14C-FDG accumulation was normalized to that of the control.
(c) Effect of 0.01 to 100 mM D-glucose (♦), D-mannose (●), D-galactose (▲), D-fructose (■), or L-glucose (×) in 14C-FDG D-PBS. Values represent the mean ± SD. n = 4–8. *P b 0.05 vs.
corresponding control.

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M. Ogura et al. / Nuclear Medicine and Biology 42 (2015) 475–481

14

C-FDG transport was not inhibited by L-glucose in AsPC-1 cells. Noneof the D-/L-ketohexoses we examined had any signiﬁcant inhibitory
effect (Fig. 2b). As shown in Fig. 2c, D-glucose and D-mannose
strongly inhibited 14C-FDG transport at all concentrations tested, andD-galactose had an inhibitory effect at concentrations above 1 mM.
Lower concentrations (0.01 and 0.1 mM) of D-fructose augmented
14
C-FDG accumulation (121.4 ± 1.1% and 117.1 ± 0.5% of control,
respectively), and 100 mM D-fructose had an inhibitory effect (45.7 ±
1.4% of control).
3.3. 14C-FDG accumulation in AsPC-1 cells pretreated with hexoses
As shown in Fig. 3a and b, 14C-FDG accumulation was augmented in
AsPC-1 cells pretreated with 1 mM D-glucose, D-mannose, or D-fructose(147.8 ± 18.6%, 129.0 ± 4.3%, or 125.0 ± 15.6% of control, respectively).
In contrast, pretreating cells with 1 mM D-galactose, D-altrose, D-gulose,or L-glucose had no signiﬁcant effect on 14C-FDG accumulation. Pretreatment with D-allose resulted in a slight decrease in 14C-FDG accumulation. Ketohexoses other than D-fructose (D-sorbose, D-tagatose,
and L-fructose) did not have any effect on 14C-FDG accumulation.
The effect of pretreating cells with D-glucose, D-mannose, D-galactose,or D-fructose at concentrations ranging from 0.01 to 100 mM is shownin Fig. 3c. We chose to also include D-galactose because Miller demonstrated that D-galactose increased the velocity of hexose transport[21]. Signiﬁcant effects were observed in cells pretreated with D-glucose(0.01 to 100 mM), D-mannose (1 to 100 mM), D-galactose (10 and

100 mM), and D-fructose (1 to 100 mM). Pretreating cells with
100 mM D-mannose led to a decrease in 14C-FDG accumulation. Pretreatment with L-glucose had no effect on 14C-FDG accumulation at
any concentration tested.
3.4. PFK-1 activity in AsPC-1 cells pretreated with hexoses
Longer pretreatments resulted in greater enhancement of PFK-1
activity in control cells or in cells pretreated with D-glucose (1 mM) or
D-fructose (1, 100 mM) (Table 1). An increase in PFK-1 activity relative
to the control in cells pretreated with 100 mM D-glucose or D-fructose
was observed at all time points examined.
To examine the effect of pretreatment with various concentrationsof hexoses, we chose D-glucose, D-mannose, D-galactose, and D-fructose,which augmented 14C-FDG accumulation. As shown in Fig. 4a and b,
pretreatment with higher concentrations of D-glucose or D-fructose
tended to increase PFK-1 activity. We found no difference in PFK-1
activity relative to the control in cells pretreated with L-glucose(1 mM), L-fructose (1 mM), D-mannose (1 to 100 mM), or D-galactose(1 to 100 mM).
4. Discussion
In this study, 14C-FDG accumulation was augmented signiﬁcantly
compared to controls in AsPC-1 cells pretreated with 1 mM D-glucose,
D-mannose, or D-fructose for 60 min. We previously reported that L-

Fig. 3. 14C-FDG accumulation in AsPC-1 cells pretreated with one hexose. Pretreatment with 1 mM (a) aldohexose or (b) ketohexose. 14C-FDG accumulation was normalized to that of thecontrol (black columns). *P b 0.05 vs. corresponding control. (c) Pretreatment with 0.01 to 100 mM D-glucose (♦), D-mannose (●), D-galactose (▲), D-fructose (■), or L-glucose (×). Values
represent the mean ± SD. n = 4–8. Signiﬁcant effects were observed with all of the hexoses we examined.

M. Ogura et al. / Nuclear Medicine and Biology 42 (2015) 475–481
Table 1
PFK-1 activity in AsPC-1 cells pretreated with 1 or 100 mM D-glucose or D-fructose.
Pretreatment

Concentration(mM)

Pretreatment
span (min)PFK-1 activity(nmol NADH/
min/mgprotein)% of PFK-1
activity(Pretreatment/each Control)

Control

0
1
100
1
100
0
1
100
1
100
0
1
100
1
100

15
15
15
15
15
30
30
30
30
30
60
60
60
60
60

20.88 ± 0.16
22.78 ± 0.34
24.39 ± 0.20
23.71 ± 0.34
23.85 ± 0.48
24.90 ± 0.87
26.21 ± 0.17
27.63 ± 0.51
25.86 ± 0.40
27.70 ± 0.04
25.66 ± 3.92
23.99 ± 0.35
32.02 ± 0.16
28.32 ± 0.27
37.11 ± 0.94

–
109 ⁎
117 ⁎
114 ⁎
114 ⁎
–
105
111 ⁎
104
111 ⁎

D-glucose
D-fructose

Control
D-glucose
D-fructose

Control
D-glucose
D-fructose

94 ⁎
125 ⁎
110
145 ⁎

The activity of PFK-1 was expressed as the amount of NADH consumed (nmol/min/mg
protein). Values represent the mean ± SD. n = 3–6.
⁎ P b 0.05 vs. corresponding control.

tyrosine esters effectively enhance transfer of a radiolabeled L-tyrosine
analog, which prompted us to examine effects on FDG accumulationin cells pretreated with hexoses [15]. Similar induction of sugar transport was reported by Miller, who observed accelerated sugar out-ﬂow[21]. Such an acceleration of substrate transport is an obligatoryexchange mechanism in amino acid transport [15,22]. Our preliminary
experiments, however, did not show acceleration of the out-ﬂow of
14
C-FDG when hexose was present outside the cell, and we hypothesized that augmentation of FDG accumulation is due to elevation in
the levels of intracellular glycolytic enzymes, not acceleration in the
obligatory exchange.
Control of glycolysis is usually explained in terms of the allostericproperties of three enzymes: hexokinase, PFK-1, and pyruvate kinase.
Many (or all) of the glycolytic enzymes in cancer cells have been suggested to be overexpressed [23,24]. Although numerous studies investigating the association between FDG accumulation and glucose
transporters or hexokinase have been published, the effects of themain regulator of glycolysis, PFK-1, on FDG accumulation have notbeen thoroughly explored [25–28].

479

We focused our investigation on PFK-1, because its phosphorylation
step is considered the major rate-limiting reaction and surmounts theregulatory roles of hexokinase and pyruvate kinase [29]. Consistent
with the results obtained from Malaisse et al. [30] and Colomer et al.
[31], our results demonstrated elevation of PFK-1 activity in AsPC-1
cells pretreated with D-glucose or D-fructose. The roles of these hexoses
in the metabolism of cancer cells have been thoroughly investigated. In
the early 20th century, D-fructose was shown to be converted into lactic
acid more rapidly than D-glucose, and cancer cells were shown to rely
on aerobic glycolysis, a phenomenon known as “the Warburg effect”[32,33]. PFK-1 mediates the phosphorylation of D-Fru-6-P to D-Fru1,6-P2 using ATP, and is regulated allosterically by the level of D-fructose
2,6-bisphosphate (D-Fru-2,6-P2) [34]. The level of the allosteric
regulator D-Fru-2,6-P2 is controlled by a bifunctional enzyme,
6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase (PFK-2/
FBPase). PFK-1 and PFK-2/FBPase share the same substrate, and PFK2/FBPase is capable of phosphorylating D-Fru-6-P to D-Fru-2,6-P2 or dephosphorylating D-Fru-2,6-P2 to D-Fru-6-P [35].
Human PFK-1 is expressed as three isozymes, type-M, -L, and -P,
which undergo random tetramerization to produce various homoand heterotetrameric isozymes, each of which shows different kinetic
properties [36]. Active investigations continue to elucidate alterations
in gene expression and enzymatic activity of these isozymes regarding
high energy production in cancer [29,35,37]. Colomer et al. have reported that PFK-1 from cancer cell extracts is more sensitive to an activation
effect by D-Fru-2,6-P2 than normal cells, although the intracellular levelsof D-Fru-2,6-P2 are equal in both normal and cancer cells [31]. SanchezMartinez et al. demonstrated that ascites tumor cells mainly express
PFK-1 type-P, whereas type-L is the more abundant isozyme in normal
mammary glands [38]. Wang et al. recently reported that enhancementof glycolytic activity depends on the conversion of PFK-1 isozyme fromtype-L to type-P during the development of cancer [39]. Consequently,
PFK-1 type-P may contribute to maintaining a high glycolytic status incancer cells [40]. Another report, however, showed that PFK-1 activity
is negligible for glycolytic ﬂux control in hepatoma cells [41]. The characteristics of PFK-1 should be further clariﬁed in future studies.
Because of the inhibitory effects of PFK-2/FBPase, which regulates
the D-Fru-2,6-P2 level and leads to a reduction in PFK-1 activity, antimetabolic agents have been investigated [29,42,43]. Expression of thePFK-2/FBPase gene is markedly elevated in cancer cells, resulting instimulation of glycolysis [44]. Clem et al. concluded that their novel
class of antimetabolic agents selectively suppresses glucose uptake by

Fig. 4. PFK-1 activity in homogenates of AsPC-1 cells pretreated with one hexose. Pretreatment with 1 mM (white columns), 10 mM (hatched columns), or 100 mM (gray columns)
aldohexose (a) or ketohexose (b). PFK-1 activities were normalized to the activity of the control (black columns). Values represent the mean ± SD. n = 3–6. *P b 0.05 vs.
corresponding control.

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M. Ogura et al. / Nuclear Medicine and Biology 42 (2015) 475–481

cancer in vivo and that glucose uptake measurements by FDG scans canbe used as pharmacodynamic endpoints in clinical trials [42]. We expectthat FDG-PET will play a role as a predictive modality for the therapeutic
effects of PFK-1 inhibitors.
Because the only curative treatment for PC patients is surgical resection, detection and/or assessment of dissemination or seeding in theperitoneum by FDG-PET are important for selecting patients who will
beneﬁt from PC resection and for avoiding unnecessary surgery(surgical resection beneﬁts only patients with localized disease) [45].
In this study, we demonstrated that pretreating cells with hexoses augments FDG accumulation, and D-fructose was the most effective at stimulating an increase in FDG accumulation among the hexoses we
examined. Nutrient treatment before injection of metabolic imaging
agents may effectively enhance tracer accumulation by cancer cells[22]. Oral administration of D-fructose leads to transient elevation of
the level of D-fructose in the blood [46].
Very little has been published in the literature about the association
between PFK-1 and FDG accumulation, and we conﬁrmed the impact ofvarious hexoses on the activity of PFK-1 and FDG accumulation in AsPC1 cells. Although PFK-1 in cancer cells has been thoroughly investigated,further studies are needed to clarify the PFK-1 characteristics that are
relevant to FDG accumulation. Such investigations will identify new features of FDG-PET; e.g., the detection of microscopic ascites tumor cells
and prediction of the effect of novel metabolic agents. In future work,
we will use in vivo studies to investigate how each treatment witheach hexose impacts FDG accumulation in various cancer cells.
Acknowledgements
We wish to thank Akihiro Imura, Takahiro Nadamura, Tomohiro
Kurosawa, Misa Kozaka, Tomoki Miyazaki, and Kazuaki Arai of Ibaraki
Prefectural University for their valuable technical assistance. This work
was supported by Grants-in-Aid for Scientiﬁc Research (#10770451,#14770498, #13557075, #15659283, #16659322, #17390336,#22591372, and #26461801) from the Ministry of Education, Science,Sports and Culture of Japan and the Japan Society for the Promotion of
Science. Financial support was also provided by Ibaraki Prefectural
University Grants-in-Aid for the Encouragement of Young Scientists in
2001, 2002, 2004, 2005, 2006, 2008, 2009, 2010, 2012 and 2014 andby a Japan Atherosclerosis Research Foundation Grant in 2014.
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