Differential anti-proliferative and apoptotic effects of lichen species on human prostate carcinoma cells

Lichens are stable symbiotic associations between fungus and algae and/or cyanobacteria that have different biological activities. Around 60% of anti-cancer drugs are derived from natural resources including plants, fungi, sea creatures, and lichens. This project aims to identify the apoptotic effects and proliferative properties of extracts of Bryoria capillaris (Ach.) Brodo & D.Hawksw, Cladonia fimbriata (L.) Fr., Evernia divaricata (L.) Ach., Hypogymnia tubulosa (Schaer.) Hav., Lobaria pulmonaria (L.) Hoffm., and Usnea florida (L.) Weber ex Wigg. lichen species on prostate cancer cells. Lichen extracts were performed by ethanol, methanol, and acetone separately by using the Soxhlet apparatus and the effects of the extracts on cell viability, proliferation, and apoptosis were measured with the utilization of MTT, LDH assay, Annexin V assay, and Western Blot. Findings of our study revealed a positive correlation between the elevation of cell sensitivity and the increase in the treatment doses of the extract in that higher doses applied reverberate to higher cell sensitivity. A similar correlation was also identified between cell sensitivity elevation and the duration of the treatment. Evidence in our study have shown the existence of an anti-proliferative effect in the extracts of Bryoria capillaris, Evernia divaricata (L.) Ach., Hypogymnia tubulosa (Schaer.) Hav., Lobaria pulmonaria (L.) Hoffm., and Usnea florida (L.) Weber ex Wigg., while a similar effect was not observed in the extracts of Cladonia fimbriata. Evernia divaricata induced anti-proliferative and apoptotic effects in PC-3 cells, which induced apoptotic cell death by both extrinsic and intrinsic pathways. Hypogymnia tubulosa has been shown to have anti-proliferative and apoptotic effects in all extractions methods and our findings identified that both the percentage of the apoptotic cells and apoptotic protein expressions recorded an increase at lower treatment concentrations. Although Lobaria pulmonaria is known to have significant cytotoxic effects, we did not observe a decrease in cell proliferation. Indeed, proliferation marker proliferating cell nuclear antigen (PCNA) protein expression levels have shown an increase in all extracts, while Usnea florida exhibited apoptosis induction and slight proliferation reduction in extract treatments with lower concentrations. We tested 18 extracts of six lichen species during our study. Of these, Evernia divaricata and Hypogymnia tubulosa demonstrated significant apoptotic activity on prostate cancer cells including at low concentrations, which implies that it is worth pursuing the biologically active lead compounds of these extracts on prostate cancer in vitro. Further corroboratory studies are needed to validate the relative potential of these extracts as anti-metastatic and anti-tumorigenic agents.