Prostate cancer (PCa) is the most diagnosed invasive cancer and a leading cause of death in men in western countries. Most patients initially respond to androgen deprivation but finally develop hormone-refractory disease, which results in advanced clinical failure and death. Since hormone-refractory disease is highly radiotherapy and chemotherapy resistant, increasing interest has been placed on finding novel therapies for this advanced type of Pca.

The potential cytotoxic effects of the crude extract and fractions obtained from the leaves of Cecropia pachystachya Trécul on different human cancer cell lines were investigated. Additionally, the mechanism of cell death induction of the most active sample (triterpene-enriched fraction, TEF) on the human hormone-refractory prostate PC3 cell line was examined.

Sulforhodamine B assay was used to measure the viability of human tumor and non-tumor cell lines. To elucidate the mechanism of PC3 cells death induced by TEF, different methodological approaches were used: cell cycle analysis and annexin V/PI staining, nuclear morphological analysis, and senescence-associated-β-galactosidase assay. Moreover, the mitochondrial membrane potential was measured, and the long-term effects of TEF on PC3 cells were evaluated.

TEF exerted cytotoxic effects on PC3 cells but not on human non-tumor cells. The analysis of nuclear morphology of PC3 cells treated with TEF increased the number of cells with large and regular nuclei suggesting senescence induction, which was supported by β-galactosidase overexpression. Regarding PC3 cells cycle, TEF reduced the number of cells in G1 phase and increased that in sub G0/G1. Apoptosis was not involved in PC3 cell death. However, there was a decrease in mitochondrial membrane potential without the participation of reactive oxygen species (ROS) in the cytotoxic effects detected. Furthermore, there was a decrease in the number of viable cells able to duplicate after long-term TEF treatment.

The results showed the in vitro cytotoxic potential of the triterpene-enriched fraction obtained from the leaves of C. pachystachya on human prostate cancer PC3 cell line.