Abstract 1161: COX-2 blockade improves efficacy of VEGF-targeting drugs
Authors: Batalla Isabel Ben , Cubas-Cordova Miguel , Udonta Florian , Wroblewski Mark , Sawall Stefanie , Gensch Victoria , Pantel Klaus , Bokemeyer Carsten , Loges Sonja 
Published: May 2015

Abstract
Efficacy of anti-angiogenic drugs is hampered by hypoxia-induced resistance. Because cyclooxygenase-2 (Cox-2) is upregulated in hypoxic conditions we analyzed mRNA expression levels of cyclooxygenase-1 (Cox-1) and Cox-2 in GFP+ FACS-sorted tumor cells from 4T1 tumors after treatment with anti-VEGFR2 antibodies (DC101) or with sunitinib. Cox-2 but not Cox-1 mRNA was upregulated by 2.3-fold upon anti-angiogenic treatment. In addition we found 5.2-fold increased prostaglandin E2 levels in 4T1 tumors after anti-angiogenic therapy. We hypothesized that concomitant blockade of Cox-2 could increase efficacy of anti-angiogenic agents. Therefore we treated 4T1 tumor-bearing mice with sunitinib or DC101 alone and in combination with acetylsalicyclic acid (ASA). We found that single treatment with ASA or angiogenesis inhibitors inhibited tumor growth and that combined inhibition of Cox-2 and VEGF(R) signaling exerted additive therapeutic efficacy (n=5; 1142±84 (ASS); 1148±78 (Sunitnib) vs. 63±5 mg (combination); p&lt;0.0001). Similar effects were achieved upon combining the specific Cox2 inhibitor SC-236 with anti-angiogenic therapy (n=6; 985±147 (SC-326); 1123±61 (Sunitnib) vs. 680±76 mg (combination); p&lt;0.05) and in the 6CCL4 orthotopic breast cancer model (data not shown). We carried out an extensive profiling of the tumor cells and their microenvironment upon concomitant blockade of Cox-2 and VEGF signaling in order to elucidate the underlying mechanism. We found no changes in tumor cell proliferation or upon combined Cox-2 inhibition and anti-angiogenic therapies. Also combined Cox-2 and VEGF-signaling inhibition did not change the quantitative composition of the inflammatory tumor infiltrate. However, upon analyzing polarization of FACS-sorted TAMs we found that mRNA of the M1 markers iNOS, MHCII, IL1β and TNFα were upregulated upon treatment with ASA alone and/or in combination with anti-angiogenic agents compared to controls or monotherapy with anti-angiogenic agents. In contrast, the M2 markers Arg1 and YM1 were downregulated upon treatment with Cox2-inhibitors and anti-angiogenic agents. Therefore, Cox-2 inhibitors skew TAMs towards an anti-tumoral M1 phenotype while the pro-angiogenic, tumor promoting M2-phenotype is suppressed.
In addition, Cox-2 and PGE2 can promote tumor angiogenesis. This alternative pro-angiogenic pathway would be enhanced by increased Cox-2 expression and PGE2 levels and could contribute to resistance against anti-angiogenic treatments. In line with this hypothesis the MVD was decreased 4T1 tumors treated with combined Cox-2 and VEGF blockade compared to the respective monotherapy (n=7; 31±2.4 (Sunitinib); 28.58±0.83 (ASS) vs. 9.67±1.71 (combination); p&lt;0.001). In conclusion concomitant Cox2 inhibition and anti-angiogenic therapies exert pronounced additive effects, which are at least partially due to increased M1 polarization and additive anti-angiogenic effects.
Citation Format: Isabel Ben Batalla, Miguel Cubas-Cordova, Florian Udonta, Mark Wroblewski, Stefanie Sawall, Victoria Gensch, Klaus Pantel, Carsten Bokemeyer, Sonja Loges. COX-2 blockade improves efficacy of VEGF-targeting drugs. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1161. doi:10.1158/1538-7445.AM2014-1161