Amaryllidaceae-Type Alkaloids from Pancratium maritimum: Apoptosis-Inducing Effect and Cell Cycle Arrest on Triple-Negative Breast Cancer Cells

Aiming to find Amaryllidaceae alkaloids against breast cancer, including the highly aggressive triple-negative breast cancer, the phytochemical study of Pancratium maritimum was carried out. Several Amaryllidaceae-type alkaloids, bearing scaffolds of the haemanthamine-, homolycorine-, lycorine-, galanthamine-, and tazettine-type were isolated (3-11), along with one alkamide (2) and a phenolic compound (1). The antiproliferative effect of compounds (1-11) was evaluated by the sulforhodamine B assay against triple-negative breast cancer cell lines MDA-MB-231 and MDA-MB-468, breast cancer cells MCF-7, and the non-malignant fibroblast (HFF-1) and breast (MCF12A) cell lines. The alkaloids 3, 5, 7, and 11 showed significant growth inhibitory effects against all breast cancer cell lines, with IC50 (half-maximal inhibitory concentration) values ranging from 0.73 to 16.3 mu M. The homolycorine-type alkaloid 7 was selected for further investigation in MDA-MB-231 cells. In the annexin-V assay, compound 7 increased cell death by apoptosis, which was substantiated, in western blot analyses, by the increased expression of the pro-apoptotic protein Bax, and the decreased expression of the anti-apoptotic protein Bcl-xL. Consistently, it further stimulated mitochondrial reactive oxygen species (ROS) generation. The antiproliferative effect of compound 7 was also associated with G2/M cell cycle arrest, which was supported by an increase in the p21 protein expression levels. In MDA-MB-231 cells, compound 7 also exhibited synergistic effects with conventional chemotherapeutic drugs such as etoposide.

Automated summary

In this study, phytochemical analysis of Pancratium maritimum revealed the presence of various Amaryllidaceae alkaloids, which exhibited significant growth inhibitory effects against breast cancer cell lines, including triple-negative breast cancer. Among the isolated compounds, the homolycorine-type alkaloid 7 showed promising anti-proliferative activity through induction of apoptosis, modulation of mitochondrial reactive oxygen species, and G2/M cell cycle arrest. Furthermore, compound 7 exhibited synergistic effects when combined with conventional chemotherapeutic drugs.