Antitumor- and apoptosis-inducing effects of pomolic acid against SK-MEL-2 human malignant melanoma cells are mediated via inhibition of cell migration and sub-Gl cell cycle arrest

Abstract

Malignant melanoma is the leading cause of mortality among the skin-associated diseases because of its highly metastatic nature and lethality. The aim of the present study was to evaluate antitumor and apoptosis effects of pomolic acid, a pentacyclic triterpene, against SK-MEL-2 human malignant melanoma cells. Its effect on cell migration and cell cycle arrest were also studied. An MTT assay was used to assess the cell cytotoxicity effects induced by pomolic acid. Fluorescence microscopy using acridine orange/propidium iodide and Hoechst 33342 staining, along with transmission electron microscopy (TEM), was used to study the effects of pomolic acid on apoptosis induction in these cells. The effects of pomolic acid on cell migration were studied using an in vitro wound healing assay. The effects of pomolic acid on cell cycle phase distribution were evaluated by flow cytometry using propidium iodide as fluorescent probe. The results revealed that pomolic acid induced significant dose- and time-dependent antiproliferative effects in SK-MEL-2 human malignant melanoma cells, with IC50 values of 110.3, 88.1 and 79.3 μM after 24, 48 and 72 h, respectively. Pomolic acid-treated cells exhibited red fluorescence, and the intensity of this fluorescence increased in a dose-dependent manner, indicating apoptosis induction. After the cells were treated with 25, 75 and 150 μM pomolic acid, significant morphological alterations characteristic of apoptosis were observed by TEM, including loss of microvilli, a damaged plasma membrane, damaged cellular organelles and enlarged lysosomes. Pomolic acid also led to sub-G1 cell cycle arrest, and inhibited cancer cell migration in a dose-dependent manner. These results implicate pomolic acid as a potential therapeutic agent for the treatment of malignant melanoma.