Estrogen receptor positive (ER+) breast cancer patients exhibit poorer responsiveness to nab-paclitaxel compared to ER negative (ER-) patients, with the underlying mechanisms remaining unknown. Caveolin 1 (CAV1) is a membrane invagination protein critical for the endocytosis of macromolecules including albumin-bound chemotherapeutic agents. Here, we demonstrate that ERα limits the efficacy of nab-paclitaxel in breast cancer cells while genetic or pharmacological inhibition of ERα increased the sensitivity of ER+ breast cancer cells to nab-paclitaxel. Notably, CAV1 expression inversely correlates with ERα and relates to improved clinical outcomes from nab-paclitaxel treatment. Importantly, ERα stimulates m6A dependent maturation of miR199a-5p, which is elevated in ER+ breast cancer, to inhibit CAV1 translation by antagonizing m6A modification of CAV1 mRNA. Together, our findings reveal a novel role of ERα in promoting m6A modification and subsequent maturation of miR199a-5p, which is upregulated in ER+ breast cancer, leading to the suppression of m6A modification of CAV1 and its mRNA translation, thereby contributing to nab-paclitaxel resistance. Thus, combining an ER antagonist with nab-paclitaxel could offer a promising strategy for treating ER+ breast cancer patients.
Keywords: Caveolin 1 (CAV1); Estrogen receptor α (ERα); N6-methyladenosine (m6A); miR199a-5p; nab-paclitaxel; translation.
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