Abstract 1151: IL-8, VEGF and IGF-1 play the important role in ARHI mediated-tumor dormancy in ovarian cancer

Ovarian cancer is the most lethal gynecologic malignancy. One of the most important factors contributing to poor outcomes is the ability of drug resistant ovarian cancer cells to remain dormant for years after treatment, only to grow progressively and kill their host. Judging from sites of recurrence, most dormant ovarian cancer cells are found on the surface of the peritoneal cavity, often in small, poorly vascularized collagenous scars observed at “second look” operations. Previously, we reported that more than 80% of persistent, dormant drug resistant ovarian cancers express ARHI and are undergoing autophagy. Autophagy can protect or kill tumor cells depending upon the context. Our group has found that autophagy and tumor dormancy can be regulated by an imprinted tumor suppressor gene, ARHI (DIRAS3), which is downregulated in 60% of ovarian cancers. Re-expression of ARHI in cell culture produces cell death within 72 hours, whereas re-expression of ARHI in xenografts produces cell growth arrest and tumor dormancy. When ARHI levels are reduced after 6 weeks of induction, xenografts grow promptly. Our current experiments were designed to determine whether survival of autophagic cells in vivo requires permissive levels of VEGF, IL-8 and IGF-1 in the tumor microenvironment. In cell culture, co-incubation of VEGF, IGF-1 and IL-8 with SKOv3-ARHI cells, increased AKT activity, reduced ARHI-mediated autophagy formation and decreased autophagic cell death. SKOv3-ARHI cells grown subcutaneously in nude mice exhibited higher levels of AKT activity and lower levels of autophagy than cells grown in cell culture. When cytoplasmic and nuclear fractions were obtained from xenografts, the nuclear fractions showed increased phospho-AKT, and decreased levels of a transcription factor EB (TFEB) and low mRNA expression of LC3, suggesting survival factors in tumor environment may stimulate AKT, downregulate expression of TFEB and inhibit formation of autophagy. Treatment with anti-VEGF, anti-IL-8 and anti-IGF-1 antibodies, individually and in combination, inhibited survival factors-mediated AKT activation and slowed the outgrowth of dormant autophagic ovarian cancer cells. Treatment of dormant xenografts with the same monoclonal antibodies against VEGF, IL-8 and IGFR not only delayed outgrowth when DOX is withdrawn, but cured a fraction of mice. Re-expression of ARHI reduced expression of IGF-1 receptor, but not VEGF and IL8 receptors. Treatment ovarian cancer cells with VEGF, IL-8 and IGF-1 reduced ARHI9s ability to induce autophagy and to inhibit AKT. These preclinical studies support that the possibility that treatment with a combination of anti-VEGF, anti-IL8 and anti-IGF-1 antibodies could prevent outgrowth of dormant cells in patients with ovarian cancer. Furthermore, these results suggest that survival factors are required to limit autophagic death. Citation Format: Zhen Lu, Aaron Orozco, Weiqun Mao, Yan Wang, Margie Nicole Sutton, Hailing Yang, Douglas A. Levine, Robert C. Bast Jr.. IL-8, VEGF and IGF-1 play the important role in ARHI mediated-tumor dormancy in ovarian cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1151.