Microtubule acetylation and PERK activation facilitate eribulin-induced mitochondrial calcium accumulation and cell death.

Over the past few decades, microtubules have been targeted by various anticancer drugs, including paclitaxel and eribulin. Despite their promising effects, the development of drug resistance remains a challenge. We aimed to define a novel cell death mechanism that targets microtubules using eribulin and to assess its potential in overcoming eribulin resistance. Notably, treating non-resistant breast cancer cells with eribulin led to increased microtubule acetylation around the nucleus and cell death. Conversely, eribulin-resistant (EriR) cells did not exhibit a similar increase in acetylation, even at half-maximal inhibitory concentrations. Interestingly, silencing the ATAT1 gene, which encodes the α-tubulin N-acetyltransferase 1 (the enzyme responsible for microtubule acetylation), induces eribulin resistance, mirroring the phenotype of EriR cells. Moreover, eribulin-induced acetylation of microtubules facilitates the transport of Ca²⁺ from the ER to the mitochondria, releasing cytochrome c and subsequent cell death. Transcriptome analysis of EriR cells revealed a significant downregulation of ER stress-induced apoptotic signals, particularly the activity of protein kinase RNA-like ER kinase (PERK), within the unfolded protein response signaling system. Pharmacological induction of microtubule acetylation through a histone deacetylase 6 inhibitor combined with the activation of PERK signaling using the PERK activator CCT020312 in EriR cells enhanced mitochondrial Ca²⁺ accumulation and subsequent cell death. These findings reveal a novel mechanism by which eribulin-induced microtubule acetylation and increased PERK activity lead to Ca²⁺ overload from the ER to the mitochondria, ultimately triggering cell death. This study offers new insights into strategies for overcoming resistance to microtubule-targeting agents.