Roles of autophagy in relation to mitochondrial stress responses of HeLa cells to lamellarin cytotoxicity.

As a promising class of bioactive marine pyrrole alkaloids, lamellarins reportedly act on multiple targets to suppress the vitality of various cancer cell lines. Nevertheless, an in-depth understanding of the molecular mechanisms governing their cytotoxicity is still in demand. Here we report that while activating intrinsic apoptosis, up to 5 μM of lamellarins and their lactam-containing analogs, azalamellarins, also induced mitochondrial stress responses and autophagy in HeLa cervical cancer cells. Detailed characterization of the mitochondria in the treated cells revealed shifted abundance of the two optic atrophy protein 1 (Opa1) isoforms, disturbed morphology, and dissipated membrane potential, leading to PTEN-induced kinase-1 (PINK1) and microtubule-associated protein 1 light chain 3-II (LC3-II) accumulation as a molecular signature of mitophagy. Furthermore, an acute treatment with lamellarins also modulated cellular autophagy flux as evidenced by elevated LC3-II levels, LC3 puncta formation, and p62 degradation. Surprisingly, clustered regularly interspaced short palindromic repeats (CRISPR)-based suppression of autophagy transiently affected the number of apoptotic cells induced by these compounds. Our findings illustrate the potential of these alkaloids for further development into prospective anti-cancer agents.