Breast cancer-related deaths are predominantly associated to complications arising from metastases. Hypoxia is an important biological process that fuels metastasis and contributes to deregulate the tumor microenvironment (TME) of solid tumors. Hypoxia also promotes resistance to therapies by a plethora of mechanisms including enhancing tumoral angiogenesis, metabolic reprogramming, epithelial-to-mesenchymal transition (EMT) and immune evasion. The expression of the receptor tyrosine kinase AXL, a hypoxia-induced gene, is associated with poor clinical prognosis and metastasis in various cancers, including breast cancer. Here, we hypothesize that genetic or pharmacological interference of AXL may alter hypoxic responses and associated modulation of the TME offering an ideal setting for immunotherapy. In a HER2 mouse model of breast cancer (MMTV-NIC), we found that the mammary gland epithelial cells specific deletion of AXL led to a reduction of lung metastases and improved the TME by reducing the hypoxic response in tumor cells. When breast cancer cells were subjected to hypoxic conditions, we found that AXL inhibition reduced the levels of the hypoxia transcription factor HIF-1a which resulted in an altered hypoxic response. Specifically, AXL deletion led to a reduction of hypoxia-induced EMT and invasion, and a reduction of the secretion of key cytokines for macrophages recruitment and polarization. We demonstrate in vivo that AXL pharmacological inhibition in the MMTV-NIC breast cancer model generated an anti-inflammatory TME that enhanced an anti-PD-1 immune checkpoint blockade response and decreased the metastatic burden. Collectively, these results suggest that targeting AXL could be a powerful approach to improve immunotherapy response by generating an anti-tumoral microenvironment therefore limiting the metastatic burden of breast cancer.

Citation Format: Marie-Anne Goyette, Jean-Philippe Gratton, Jean-François Côté. Targeting AXL favors an anti-tumorigenic tumor microenvironment that enhances immunotherapy responses by decreasing HIF-1a levels in cancer cells [abstract]. In: Proceedings of the AACR Virtual Special Conference on the Evolving Tumor Microenvironment in Cancer Progression: Mechanisms and Emerging Therapeutic Opportunities; in association with the Tumor Microenvironment (TME) Working Group; 2021 Jan 11-12. Philadelphia (PA): AACR; Cancer Res 2021;81(5 Suppl):Abstract nr LT021.