Conofolidine, a Natural Plant Alkaloid Causes Apoptosis and Senescence in Cancer Cells

Al-Hayali, Mohammed Zuhair; Nge, Choy-Eng; Lim, Kuan Hon; Collins, Hilary M.; Kam, Toh Seok; Bradshaw, Tracey Dawn

Abstract

Natural products contribute substantially to anticancer therapy; the plant kingdom provides an important source of molecules. Conofolidine is a novel Aspidosperma-Aspidosperma bisindole alkaloid isolated from the Malayan plant Tabernaemontana corymbosa. Herein, we report conofolidine’s anticancer activity together with that of three other bisindoles - conophylline, leucophyllidine and bipleiophylline against human-derived carcinoma cell lines. Remarkably, conofolidine was able to induce apoptosis (as observed in MDA-MB-468 breast cancer cells) or senescence (as detected in HT-29 colorectal carcinoma cells). Annexin V-FITC/PI, caspase activation and PARP cleavage confirmed the former while positive β-gal staining corroborated the latter. Evident cell cycle perturbations were observed comprising S-phase depletion, accompanied by downregulated CDK2, and cyclins (A2, D1) with p21 upregulation. Confocal imaging of HCT-116 cells revealed induction of aberrant mitotic phenotypes - multi-nucleation, membrane blebbing and DNA-fragmentation. The DNA integrity assessment of HCT-116 and MDA-MB-468 showed irreparable damage identified by increased fluorescent γ-H2AX during the G1 cell cycle phase. Furthermore, γ-H2AX foci were visually validated in HCT-116 and MDA-MB-468 cells using confocal microscopy. Conofolidine increased oxidative stress, preceding apoptosis- and senescence-induction in most carcinoma cell lines as seen by enhanced ROS levels accompanied by NQO1 expression. Collectively, we present conofolidine as a potential anticancer candidate capable of inducing heterogeneous modes of cancer cell death in vitro, encouraging further preclinical evaluation of this natural product.

Citation

Al-Hayali, M. Z., Nge, C.-E., Lim, K. H., Collins, H. M., Kam, T. S., & Bradshaw, T. D. Conofolidine, a Natural Plant Alkaloid Causes Apoptosis and Senescence in Cancer Cells

• Working Paper Type: Working Paper
• Deposit Date: Jan 15, 2024
• Publicly Available Date: Jan 16, 2024
• Keywords: conofolidine; bisindole alkaloids; carcinoma cell lines; cytotoxicity; apoptosis; senescence; ROS generation; γ-H2AX
• Public URL: https://nottingham-repository.worktribe.com/output/29557036
• Publisher URL: https://www.preprints.org/manuscript/202401.0602/v1