Abstract 2453: Resistance of triple-negative breast cancer cells to EGFR-targeted tyrosine kinase inhibitors is associated with Annexin A6-dependent metabolic reprogramming
Authors: Williams Stephen D. , Widatalla Sarrah E. , Sakwe Amos M. 
Published: July 2021

Abstract
The ability of cancer cells to alter their metabolism is one of the major mechanisms underlying therapeutic resistance in multiple tumor types, including triple-negative breast cancer (TNBC). Triple-negative breast cancer (TNBC) remains a hard-to-treat breast cancer subtype. Significant effort has thus far been devoted to epidermal growth factor receptor (EGFR) targeted therapies as 70% of TNBC tumors overexpress EGFR. However, clinical trials utilizing anti-EGFR therapies have shown great success in various cancer types including non-small cell lung cancer but have been largely unsuccessful in TNBC due to the lack of understanding of TKI-acquired resistance. We have shown that the expression status of annexin-A6 (AnxA6), a calcium-dependent membrane binding tumor suppressor, stabilizes activated EGFR on the cell surface. We have also shown that chronic treatment of AnxA6-low TNBC cells with Lapatinib induces AnxA6 expression and accumulation of cholesterol in late endosomes suggesting a novel mechanism for resistance of TNBC to EGFR-TKIs. Other studies have revealed that AnxA6 expression contributes to impaired fat storage and adiponectin release in adipose tissues, and that lack of AnxA6 compromises alanine-dependent gluconeogenesis and liver regeneration in mice. However, whether the EGFR-TKI induced upregulation of AnxA6 is associated with metabolic reprogramming in TNBC cells remains unclear. Using the Seahorse XF Analyzer, we assessed the live-cell oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) of TNBC cells. We demonstrate that the basal mitochondrial respiration and glycolytic rates classified TNBC cells into two distinct metabolic phenotypes. Those with higher OCR/ECAR ratios and cellular ATP production capacity were mostly AnxA6 high cells (energetic phenotype), while those with lower OCR/ECAR ratios and cellular ATP production capacity were mostly AnxA6 low cells (quiescentphenotype). Induction of AnxA6 expression following chronic treatment of AnxA6-low TNBC cells with Lapatinib (LapR) reverted these otherwise quiescent metabolic phenotypes to the energetic phenotype associated with higher OCR/ECAR ratios and cellular ATP production capacity. However, downregulation of AnxA6 in AnxA6 high TNBC cells attenuated the mitochondrial and glycolytic function with reduced OCR/ECAR ratios and decreased cellular ATP production capacity. NMR-based metabolomics revealed that AnxA6 depleted and/or lapatinib-resistant TNBC cells have a greater dependency on gluconeogenic amino acids including alanine, cysteine, glycine, and proline. These data suggest that altered expression of AnxA6 is accompanied by significant bioenergetic adaptations and provide novel insights into the failure of EGFR-targeted therapies as therapeutic options for TNBC.
Citation Format: Stephen D. Williams, Sarrah E. Widatalla, Amos M. Sakwe. Resistance of triple-negative breast cancer cells to EGFR-targeted tyrosine kinase inhibitors is associated with Annexin A6-dependent metabolic reprogramming [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2453.