Potential anti-ovarian cancer agent: Isoaaptamine interference epithelial-mesenchymal transition, induces intrinsic apoptosis, and suppresses angiogenesis.

Ovarian cancer (OC) often metastasizes to the peritoneal cavity, causing late-stage diagnosis with high mortality. Aaptamine and isoaaptamine, sponge-derived isomeric alkaloids, were investigated for the anti-tumor potential of isoaaptamine in OC cells. Isoaaptamine outperforms aaptamine, significantly reducing the viability of PA-1 and SKOV-3 cells with half maximal inhibitory concentration (IC50) values of ∼5 μM and 15 μM, respectively. It induced apoptosis, increasing apoptotic cells by ∼3.5-fold (p < 0.01), elevated reactive oxygen species (ROS) by ∼3-fold, and decreased mitochondrial membrane potential (ΔΨm). Western blotting showed increased cleaved caspases, cleaved PARP, and Bax, while Bcl-2, oxidative phosphorylation (OXPHOS), and superoxide dismutase 2 (SOD2) were downregulated. Seahorse analysis demonstrated ∼50 % reductions in basal respiration, adenosine triphosphate (ATP) production, and maximal respiration (p < 0.01). Isoaaptamine suppressed adhesion, migration, invasion, and colony formation by ∼50 % (p < 0.01). Epithelial-mesenchymal transition (EMT) marker analysis revealed increased E-cadherin (2.5-fold) and decreased vimentin (>80 %) in PA-1 cells. Pretreatment with the mitochondrial-targeted antioxidant MitoTEMPO attenuated ROS accumulation and apoptosis. In angiogenesis assays, isoaaptamine reduced human umbilical vein endothelial cell (HUVEC) tube length and branch points by ∼70 % and inhibited rat aortic ring sprouting (p < 0.01). Isoaaptamine impaired angiogenic potential by inhibiting endothelial wound healing and migration, while reducing mitochondrial respiration by ∼50 %. Vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS) protein levels decreased by approximately 80 % and matrix metalloproteinase (MMP)-2/-9 activity was suppressed. Together, these results provide mechanistic insights into isoaaptamine's anti-cancer effects and support further preclinical investigation in ovarian cancer.