Combinations of Bevacizumab and Erlotinib Show Activity in Colorectal Cancer Independent of RAS Status

Purpose: There is extensive cross-talk between VEGF- and EGFR-pathway signaling in colorectal cancer. However, combinations of VEGF- and EGFR-targeted monoclonal antibodies (mAb) show disappointing activity, in particular for patients with mutant RAS Previous results show that tyrosine kinase inhibitors (TKI) can be active in colorectal cancer models resistant to mAbs. This prompted us to examine whether the activity of bevacizumab can be increased by combination with erlotinib.Experimental Design: The antitumor activity of bevacizumab, erlotinib, and their combination was determined in colorectal cancer models with different RAS status and bevacizumab sensitivity. EGFR/VEGF pathway activation was characterized by immunohistochemistry, Western blot, and ELISA assays. The influence of cetuximab and erlotinib on EGF-mediated migration and the EGFR-EGF ligand feedback loop was established in colorectal cancer cell lines with different RAS status.Results: The addition of erlotinib increased bevacizumab activity in all models independent of RAS status. Bevacizumab exposure was accompanied by marked EGFR activation in tumor cells as well as in tumor-associated endothelial cells (TECs) and resulted in strong accumulation of intracellular EGFR, which could be attenuated by erlotinib. In cellular models, erlotinib was able to attenuate EGF-mediated functions in all cell lines independent of RAS status while cetuximab only showed activity in RAS wild-type cells.Conclusions: These results should provide a molecular framework to better understand the increased activity of the bevacizumab-erlotinib combination, compared with bevacizumab alone, in the GERCOR DREAM phase III clinical trial. Differential activity of mAbs and TKIs targeting the same signaling pathway is likely applicable for other tumor types. Clin Cancer Res; 24(11); 2548-58. ©2018 AACR.

Intrinsic bevacizumab resistance is associated with prolonged activation of autocrine VEGF signaling and hypoxia tolerance in colorectal cancer cells and can be overcome by nintedanib, a small molecule angiokinase inhibitor

Colorectal cancer (CRC) is a common tumor type with a high mortality rate, in part due to intrinsic drug resistance. Although bevacizumab, a VEGF-directed neutralizing antibody, is particularly active in this pathology, some patients never respond for reasons not well understood. We here wish to clarify the role of autocrine VEGF signaling in the response of CRC cells to angiogenesis inhibition. Our results show that CRC cells with intrinsic bevacizumab-resistance displayed pronounced upregulation of autocrine HIF-VEGF-VEGFR signaling in response to prolonged bevacizumab exposure whereas the same signaling pathway was downregulated in bevacizumab-sensitive xenografts. Importantly, both bevacizumab-sensitive and -resistant CRC xenografts were sensitive to nintedanib, a small molecule angiokinase inhibitor, which was associated with inhibition of mTORC1. In vitro studies revealed that bevacizumab-resistant cells displayed intrinsically higher HIF-VEGF signaling intensity and hypoxia tolerance compared to their bevacizumab-sensitive counterparts. Interestingly, although nintedanib showed comparable activity toward bevacizumab-sensitive cells under normoxia and hypoxia, the drug was three-fold more toxic to the resistant cells under hypoxia, suggesting that nintedanib attenuated the survival signaling that usually protects these cells from hypoxia-mediated cell death. In conclusion, our findings support a role for autocrine VEGF signaling in the survival of CRC cells to hypoxia and thus to angiogenesis inhibition. We further show that nintedanib, a small molecule angiokinase inhibitor, is active toward CRC models with intrinsic bevacizumab resistance supporting clinical trials of nintedanib in patients that do not respond to bevacizumab, alone or in combination with bevacizumab to increase angiogenesis inhibition.

Prolonged bevacizumab exposure accompanied by EGFR activation in colorectal cancer (CRC) models to provide a rational for combinations of bevacizumab and erlotinib in the GERCOR DREAM phase III trial

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Background: Combinations of EGFR and VEGF(R)-targeted agents have consistently shown at least additive activity in preclinical CRC models when the targeted agents were administered alone (Larsen et al., Pharmacol Therap. 131:80, 2011; Poindessous et al., Clin Cancer Res. 17:6522, 2011) paving the way for the GERCOR DREAM-OPTIMOX3 phase III trial in metastatic CRC. Although use of EGFR-directed mAbs are counter-indicated in CRC patients with mutant KRAS, the situation is less clear for EGFR-targeted TKIs like erlotinib. Methods: Three human CRC xenograft models expressing wt KRAS/BRAF, mutant KRAS or mutant BRAF were established in nude mice. Animals were treated with bevacizumab and erlotinib, alone or in combination, and the influence on tumor growth, viability and the presence of phosphorylated ErbB/HER family members was determined. Treatment-related toxicity was estimated by weight loss. Results: Combinations of bevacizumab and erlotinib were significantly more active than either agent alone for all three xenograft models although the advantage of combining the two agents was particularly striking for the KRAS/BRAF wt xenograft model. Unexpectedly, erlotinib alone showed strong antitumor activity in the BRAF mutant HT-29 xenograft model. The bevacizumab plus erlotinib combination was less toxic, as determined by weight loss, compared to erlotinib alone. Interestingly, IHC analysis showed that bevacizumab activates EGFR in all three xenograft models. Conclusions: We here report that bevacizumab and erlotinib combinations are significantly more active than either agent alone in CRC models with different KRAS and BRAF status. We further demonstrate that bevacizumab activates EGFR signaling similar to what has been described for irinotecan and ionizing radiation. Taken together, our findings suggest that mutant KRAS and BRAF have lesser influence on the sensitivity to EGFR-targeted TKIs than is the case for the EGFR directed mAbs and provide a mechanistic basis for the increased activity of the bevacizumab and erlotinib combination.

Effect of nintedanib, a triple angiokinase inhibitor, on EGFR and HER2 in colorectal cancer (CRC) models, and rational for its combinations with the ErbB family blocker afatinib

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Background: We have recently shown that combinations of afatinib, a pan-HER/ErbB blocker, and nintedanib, a triple angiokinase (VEGFR, FGFR, PDGFR) inhibitor show synergistic activity in CRC models (Poindessous et al., Clin Cancer Res. 17:6522, 2011). However, the mechanistic basis for the synergistic effects of the combination is incompletely understood. EGFR is activated following exposure to a wide variety of therapeutic modalities including ionizing irradiation and irinotecan. We speculated that nintedanib exposure could also activate EGFR signaling which might explain the synergistic activity of the combination. Methods: Mice with human CRC xenografts were treated with nintedanib and afatinib alone or in combination and the influence on tumor growth, viability and the presence of phosphorylated HER family members was determined. Different scheduling regimens were explored to identify an administration schedule which combined optimal antitumor activity with minimal toxic side effects. Results: We here show that nintedanib treatment results in activation of EGFR and HER2 in multiple CRC xenograft models in a dose-dependent manner. Among the different regimens tested, continuous nintedanib with administration of afatinib every second week proved almost as efficient as continuous administration of the two agents together and was less toxic. Finally, nintedanib plus afatinib was superior to nintedanib alone in three different tumor xenografts with mutant KRAS. Conclusions: We here report that prolonged exposure to nintedanib, a small molecule angiogenesis inhibitor, is accompanied by activation of EGFR and HER2. Accordingly, afatinib, an ErbB family blocker, was synergistic with nintedanib. We subsequently identified a novel regimen for optimizing the antitumor effects of the combination with limited toxic side effects and showed that this regimen is active in four different CRC tumor models including three with mutant KRAS. These findings provide a rationale for clinical trials of the two small molecules, even in patients with mutant KRAS.