Abstract 861: Nuclear translocation of Axl during early breast cancer progression

Abstract

Axl is a receptor tyrosine kinase (RTK) that is activated by its ligand Gas6 and regulates proliferation, cell survival, and clearance of apoptotic cells in both normal physiology and a number of disease states. In breast cancer, Axl is overexpressed in Her2+ and triple-negative breast cancers and is associated with resistance to RTK targeted therapies. Recent studies have shown that upon kinase inhibition, the Axl intracellular domain (ICD) can translocate to the nucleus, however, the biological significance and functions for nuclear Axl are poorly understood. Furthermore, a functional role for Axl during ductal carcinoma in situ (DCIS) progression, a requisite step for invasive breast cancer, has not been established. To address whether Axl mediates localized invasion during DCIS progression, Axl was deleted in a DCIS cell line (MCF10A-DCIS.com) using a CRISPR-Cas9 approach. Deletion of Axl shows a significant decrease in progression to invasive cancer in vivo, which is accompanied by decreased proliferation, however microinvasion is unchanged as compared to wildtype. Analysis of patient samples of pure DCIS, DCIS with microinvasion, and DCIS with invasive cancer shows a significant increase in Axl expression in patients with evidence of invasion. Interestingly, there is a significant increase in nuclear Axl in all patient samples with evidence of invasion as compared to normal breast or pure DCIS, suggesting an important role for Axl-ICD in progression to invasive cancer. Soft agar assays using normal cells (MCF10A) shows that while full length Axl (Axl-FL) is sufficient to induce colonies, Axl-ICD-transduced cells do not form colonies, suggesting that Axl-ICD alone does not have oncogenic activity. However, Axl-ICD significantly increases colonies in DCIS cells, suggesting that the ICD is important in the progression of transformed cells. Ongoing studies are aimed at identifying transcriptional targets of Axl-ICD in DCIS cells. These studies will advance our understanding of how Axl mediates breast cancer progression and will have critical implications for ongoing therapeutic strategies aimed at targeting Axl. This work is supported by NIH R01CA212518 (H.L.M.) and Susan G. Komen CCR1637765 (H.L.M.). Citation Format: Darby R. Graham, Kelly D. Hebert, Emma E. Newton, Angelica M. Gomes, Fariba Behbod, Heather L. Machado. Nuclear translocation of Axl during early breast cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 861.