Abstract AS14: Contrast enhanced interleukin 16 targeted imaging detects ovarian tumor at early stage

Background: The high rate of death of ovarian cancer (OVCA) patients can be reduced if it is detected at early stage. Neither suggested serum markers nor the currently available traditional transvaginal ultrasound (TVUS) imaging or their combinations can detect OVCA at early stage. No imaging target in the ovary for TVUS imaging corresponding to the suggested serum markers has been defined. Moreover, due to the limited resolution, TVUS imaging cannot detect OVCA at early stage. Thus, new imaging target(s) together with improvement in resolution is necessary for early OVCA detection by TVUS imaging. Interleukin 16 (IL-16), a proinflammatory cytokine, associated with longstanding unresolved inflammation due to frequent ovulation, has been reported to be increased during OVCA development. IL-16 is expressed by the ovarian malignant cells and tumor associated neoangiogenic (TAN) microvessels. Thus IL-16 represents a potential marker of early OVCA which can be detected in vivo by TVUS imaging provided a molecular targeted contrast enhanced imaging agent can be developed. Objective: The goal of this study was to develop and test the efficacy of molecular (IL-16)-targeted ultrasound imaging probe for the detection of early OVCA. Materials and Methods: 3-years old (n=150) White Leghorn laying hens with normal or low egg laying rates or stopped-egg laying were scanned by TVUS before and after intravenous injection with IL-16-targeted microbubbles. IL-16-targeted imaging agents were prepared by conjugating anti-chicken IL-16 antibodies with Targetster® containing microbubbles (Targeson Inc, San Diego). All images were archived and analyzed offline. Serum samples were collected, hens were euthanized, ovarian tissues were processed for paraffin or frozen sections and nuclear matrix protein (NMP) extraction. Ovarian tumors were confirmed by gross morphology and routine histology. Sera were tested for anti-NMP antibodies (a marker of malignant nuclear transformation) and IL-16 levels by immunoassay and 1- & 2D-Western blot (WB). The frequencies of IL-16 expressing cells were determined by immunohistochemistry (IHC). Results: IL-16-targeted microbubbles bounded with ovarian tumors and appeared as shining mass of irregular-shape. Compared with non-targeted, IL-16-targeted imaging increased the visualization of ovarian tumors remarkably. All hens with suspected tumor mass (n=23, 7 early and 16 late stages) were detected by IL-16-targeted imaging and confirmed by gross examination. The frequency of IL-16 expressing cells detected by IHC confirmed the prediction of targeted ultrasound imaging. Serum levels of IL-16 were higher in OVCA hens than in normal hens and correlated with the frequencies of IL-16 expressing cells and ovarian TAN vessels. Prevalence of anti-NMP antibodies were not detected in normal hens while all hens with OVCA were positive. Immunoreactive tumor antigens (NMPs) of 50-80kDa were detected by 2D-WB. Conclusion: IL-16-targeted ultrasound imaging enhanced the visualization of ovarian tumors remarkably. The enhanced intensity of IL-16-targeted imaging was correlated with serum IL-16 levels and the prevalence of anti-NMP antibodies. Thus, IL-16-targeted imaging in association with serum anti-NMP antibodies may improve OVCA detection at early stage. These results will form a foundation for a clinical study. Support: Dept. of Defense award # W81XWH-12-1-0460. Citation Format: Animesh Barua, Aparna Yellapa, Pincas Bitterman, Janice M Bahr, Sanjib Basu, Sameer Sharma, Jacques S. Abramowicz. Contrast enhanced interleukin 16 targeted imaging detects ovarian tumor at early stage [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr AS14.