Title: Abstract 3394: Bevacizumab enhances the antitumor effect of BRAFV600E inhibition in colorectal and melanoma xenograft models
Abstract: Abstract BRAF inhibitors (BRAFi) have shown improved response rate and overall survival (OS) compared to standard chemotherapy in metastatic melanoma. Combinations of BRAF and MEK targeted agents further improve progression-free survival (PFS) and OS when compared with single-agent BRAFi, but the development of resistance remains a major obstacle to long-term disease control. Thus, additional strategies must be exploited to increase the efficacy of BRAF-MEK blockade in metastatic melanoma and circumvent or delay the onset of resistance. We have previously demonstrated in murine xenograft models of BRAF mutant melanomas and colorectal cancers (CRC) that the vemurafenib analog, PLX4720, has cytostatic activity and induces vascular normalization by changing the pro-angiogenic program triggered by the oncogenic mutation (Bottos A et al., 2012;109(6):E353-9). We hypothesized that BRAF-targeted inhibitors could cooperate with anti-angiogenic regimens in the treatment of BRAF-mutant melanoma and colorectal tumors. Here, we demonstrated that when associated with the VEGFA neutralizing antibody bevacizumab (COMBO), PLX4720 shows enhanced anti-cancer effects and induces a de novo transcriptional signature in BRAF mutant melanoma and colorectal xenografts. Interestingly, in the COMBO, bevacizumab does not alter the improvement in blood perfusion and tumor vessel normalization observed with PLX4720 alone. Although targeted inhibition of either BRAF or VEGFA initially suppresses the tumor growth, only combined inhibition of both pathways results in an evident apoptotic effect. Furthermore, bevacizumab delays the onset of resistance to PLX4720 by recruiting macrophages with a M1-like phenotype and inducing a remodeling of the extracellular matrix. The latter is characterized by a reduction in collagen deposition and of cancer-associated fibroblasts (CAFs), known to sustain cancer progression. The effect of bevacizumab on acquired resistance to PLX4720 is transient and depends on the presence of M1 macrophages. Indeed, 3/6 xenografts treated with COMBO start re-growing after 6 weeks with a dramatic reduction of infiltrating macrophages and an increase of CAFs. Collectively, our findings offer a new perspective for the management of clinical resistance to BRAF inhibitors and offer a rationale to combine BRAFV600E inhibitors with anti-angiogenic regimens. Citation Format: Valentina Comunanza, Davide Corà, Emanuele Middonti, Federica Di Nicolantonio, Enzo Medico, Dario Sangiolo, Federico Bussolino. Bevacizumab enhances the antitumor effect of BRAFV600E inhibition in colorectal and melanoma xenograft models. [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 3394.
Publication Year: 2016
Publication Date: 2016-07-15
Language: en
Type: article
Indexed In: ['crossref']
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