Ovarian cancer is one of the commonest gynecologic malignancies, which has a poor prognosis for patients at the advanced stage. Isoliquiritigenin (ISL), an active flavonoid component of the licorice plant, previously demonstrated antioxidant, anti-inflammatory, and tumor suppressive effects. In this study, we investigated the antitumor effect of ISL on human ovarian cancer in vitro using the human ovarian cancer cell lines, OVCAR5 and ES-2, as model systems. Our results show that ISL significantly inhibited the viability of cancer cells in a concentration- and time-dependent manner. Flow cytometry analysis indicated that ISL induced G2/M phase arrest. Furthermore, the expression of cleaved PARP, cleaved caspase-3, Bax/Bcl-2 ratio, LC3B-II, and Beclin-1 levels were increased in western blot analysis. To clarify the role of autophagy and apoptosis in the effect of ISL, we used the autophagy inhibitor—3-methyladenine (3-MA) to attenuate the punctate fluorescence staining pattern of the p62/sequestosome 1 (SQSTM1, red fluorescence) and LC3 (green fluorescence) proteins after ISL treatment, and 3-MA inhibited the cytotoxicity of ISL. These findings provide new information about the link between ISL-induced autophagy and apoptosis and suggest that ISL is a candidate agent for the treatment of human ovarian cancer.

Marine sponges are known to produce numerous bioactive secondary metabolites as defense strategies to avoid predation. Manzamine A is a sponge-derived β-carboline-fused pentacyclic alkaloid with various bioactivities, including recently reported anticancer activity on pancreatic cancer. However, its cytotoxicity and mode of action against other tumors remain unclear. In this study, we exhibit that manzamine A reduced cell proliferation in several colorectal cancer (CRC) cell lines. To further investigate the manzamine A triggered molecular regulation, we analyzed the gene expression with microarray and revealed that pathways including cell cycle, DNA repair, mRNA metabolism, and apoptosis were dysregulated. We verified that manzamine A induced cell cycle arrest at G₀/G₁ phase via inhibition of cyclin-dependent kinases by p53/p21/p27 and triggered a caspase-dependent apoptotic cell death through mitochondrial membrane potential depletion. Additionally, we performed bioinformatics analysis and demonstrated that manzamine A abolished epithelial–mesenchymal transition process. Several mesenchymal transcriptional factors, such as Snail, Slug, and Twist were suppressed and epithelial marker E-cadherin was induced simultaneously in HCT116 cells by manzamine A, leading to the epithelial-like phenotype and suppression of migration. These findings suggest that manzamine A may serve as a starting point for the development of an anticancer drug for the treatment of metastatic CRC.