Abstract 1926: Antitumor and antiangiogenic effects of OTX-008, a novel calyx[4]arene, are mediated by galectin-1 inhibition in human tumor xenograft models

Abstract

Abstract Background. Galectin-1 binds neuropilin-1, enhances VEGFR2 signalling, and contributes to membrane anchorage of H-RAS in cancer cells. Those effects may modulate cancer cell proliferation, apoptosis, and tumor angiogenesis. OTX-008 is a non-peptide chemical antagonist designed to bind galectin-1. We previously showed that OTX-008 displays direct antiproliferative effects and inhibits galectin-1 expression in cancer cell lines (AACR 2011, Abstract n°685). In this study we focused on the antitumor and antiangiogenic effects of galectin-1 inhibition by OTX-008 or shRNA in xenograft models. Material and Methods. A2780-1A9 (1A9) ovarian cells, head and neck SQ20B and SQ-shGAL-1 (SQ20B transfected with shGalectin-1 RNA) cells were injected s.c. into female nu/nu athymic mice. When tumors became palpable, 1A9- and SQ20B- mice were treated with vehicle (PBS) or 5-10 mg/kg OTX008 i.p. q.d for 3 weeks. At the end of treatment, mice were sacrificed and tumors collected. Immunohistochemistry was performed on OCT-embedded tumor stained with H&E, galectin-1, MIB1 (Ki67), VEGFR2 or CD31. Image quantification was done with Histolab software (Microvision, France) subtracting the background. Results. OTX-008 inhibited tumor growth in both 1A9 and SQ20B xenografts after 21 days of treatment. A major decrease in the number of secondary tumors development was observed in SQ20B xenografts. A decrease in galectin-1 expression was seen in treated tumors respect to control tumors (1A9: 11.103 +/− 2.103 µm2 vs 26.103 +/− 6.103 µm2, p<0.05; SQ20B: 3.103 µm2 +/− 0,6.103 vs 28.103 +/− 7.103 µm2, p<0.01; respectively). OTX-008 treated tumors also expressed significantly lower MIB1 and VEGFR2. Furthermore, a decreased in vessels number (p<0.01 for SQ20B) and diameter were observed using CD31 staining (1A9 treated vs control: 0,5.103 +/− 0,1.103 µm2 vs 6.103 +/− 2.103 µm2, p<0.01; SQ20B treated vs control: 10.103 +/− 1.103 µm2 vs 28.103 +/− 4.103 µm2, p<0.005), suggesting OTX-008 antiangiogenic effects. In order to confirm our findings, SQ-shGAL1 cells were injected into nude mice. Galectin-1 inhibition by shRNA recapitulated the effects of OTX-008 in SQ20B xenografts. Tumor growth reduction, downregulation of MIB1 (p<0.005) and VEGFR2 (p<0.05) expression in cancer cells, as well as a reduction of vessels number (p<0.05) and diameter (p<0.005) were detected in SQ-shGAL1 tumors. Conclusion. Our findings show that antitumor and antiangiogenic activities of OTX-008 in xenograft models are associated with galectin-1 expression inhibition. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1926. doi:1538-7445.AM2012-1926