Targeting oncogenic MAGEA6 sensitizes triple negative breast cancer to doxorubicin through its autophagy and ferroptosis by stabling AMPKα1

Melanoma-associated antigen A6 (MAGEA6) is well known to have oncogenic activity, but the underlying mechanisms by which it regulates tumor progression and chemo-resistance, especially in triple-negative breast cancer (TNBC), have been unknown. In the study, the differential expression genes (DEGs) in TNBC tumor tissues and TNBC-resistant tumor tissues were analyzed based on TCGA and GEO datasets. MAGEA6, as the most significantly expressed gene, was analyzed by RT-qPCR, western blotting and immunohistochemistry assay in TNBC cell lines and tumor tissues. The potential mechanisms that influence chemo-resistance were also evaluated. Results displayed that MAGEA6 was highly expressed in TNBC and involved in drug resistance. MAGEA6 silencing enhanced the chemo-sensitivity of TNBC to doxorubicin (DOX) in vitro and in vivo, as determined by decreasing IC₅₀ value, proliferation and invasion capacity, and triggering apoptosis. Mechanistically, it was shown that MAGEA6 depletion sensitized TNBC to DOX via regulating autophagy. Ubiquitination assay displayed that knockdown of MAGEA6 decreased the AMPKα1 ubiquitination, thereby elevating the levels of AMPKα1 and p-AMPKα in TNBC cells. Importantly, AMPK inhibitor (Compound C) can reduce the LC3II/I level induced by sh-MAGEA6, indicating that sh-MAGEA6 activated AMPK signaling through suppressing AMPKα1 ubiquitination and then facilitated autophagy in TNBC. Furthermore, we also observed that AMPK is required for SLC7A11 to regulate ferroptosis, and supported the crux roles of MAGEA6/AMPK/SLC7A11-mediated ferroptosis on modulating DOX sensitivity in TNBC cells. These findings indicated that targeting MAGEA6 can enhance the chemo-sensitivity in TNBC via activation of autophagy and ferroptosis; its mechanism involves AMPKα1-dependent autophagy and AMPKα1/SLC7A11-induced ferroptosis.