Abstract 4039: Harnessing the tumor adaptive response to hypoxia to identify novel combinations of the vascular disrupting agent BNC105 with targeted therapeutics.
Authors: Lavranos Tina C. , Inglis Daniel J. , Beaumont Donna M. , Leske Annabell F. , Brown Chloe K. , Kremmidiotis Gabriel 
Published: August 2014

BNC105 is a small molecule Vascular Disrupting Agent (VDA) that exerts anti-cancer activity through selective shut-down of tumor blood vessels. A single dose of BNC105 causes a very high degree of hypoxia resulting in &gt;95% necrosis 24hrs post treatment in rodent tumor models. Tumor recovery from the hypoxic stress caused by BNC105 occurs by day 2 post-treatment. We have conducted immunohistochemical analysis to identify the molecular basis driving this tumor recovery. Using the mouse renal cancer orthotopic tumor model RENCA, we demonstrated that BNC105 causes significant vascular shutdown within the tumor mass and is followed by activation of a number of proteins that have been previously shown to be involved in tumor adaptive responses to hypoxia. These responses included: upregulation of GLUT1, a potential reflection of increased cancer cell dependency on glucose metabolism, increased expression of the angiogenic drivers HIFα and VEGFA and increased phosphorylation of mTOR and 4EBP1. Furthermore, there was upregulation of PERK and phosphorylation of eIF2α, reflecting activation of the Unfolded Protein Response (UPR). Similar observations were recorded when these proteins were studied in BNC105 treated mice bearing tumors of the human renal cancer cell lines Caki-1 (VHL wild type) and A-498 (VHL mutant), suggesting that these changes are likely to be generic to renal tumors being exposed to BNC105 induced hypoxia. These observations led us to investigate the potential therapeutic benefit of combining BNC105 with agents inhibiting the function of proteins being upregulated as a result of BNC105 induced hypoxia. Rapamycin was used to inhibit mTOR signalling. Treatment of mice bearing A498 tumors with BNC105, Rapamycin or the combination demonstrated greater tumor inhibition when the combination was used. Tumor growth inhibition with Rapamycin alone was 18% and BNC105 alone 12%. The Rapamycin + BNC105 combination treatment resulted in 47% tumor growth inhibition and was statistically significant compared to the inhibition seen with the monotherapies (p&gt;0.05). The potential benefit of combining BNC105 with the proteasome inhibitor Bortezomib was also investigated. Upregulation of PERK has been shown to be associated with ER stress caused by accumulation of unfolded proteins. We hypothesised that concurrent inhibition of the proteasome with Bortezomib will increase cell stress resulting in increased tumor necrosis. Treatment of RENCA tumors with BNC105 + Bortezomib resulted in increased tumor necrosis compared to animals treated with Bortezomib or BNC105 alone. This suggests that the tumor is more susceptible to these agents when in combination. These data demonstrate that BNC105 can be combined with therapies targeting tumor adaptive responses to hypoxia to yield greater anti-tumor efficacy.

Citation Format: Tina C. Lavranos, Daniel J. Inglis, Donna M. Beaumont, Annabell F. Leske, Chloe K. Brown, Gabriel Kremmidiotis. Harnessing the tumor adaptive response to hypoxia to identify novel combinations of the vascular disrupting agent BNC105 with targeted therapeutics. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4039. doi:10.1158/1538-7445.AM2013-4039