Depside and depsidone-rich hydroalcoholic extract, resourced from the lichen Parmelinella wallichiana (Taylor) Elix & Hale selectively restricts Non-Small Cell Lung Cancer by modulating p53, FOXO1 and PALLADIN genes

The non-specificity of contemporary cancer therapeutics has enticed us to develop safer, anticancer alternatives from natural resources. Lichens are unique natural entities which have long been neglected for explorations in cancer therapy, despite their vast potential. Our present study aims to investigate the anti-cancer potential of a wild lichen Parmelinella wallichiana. The anti-proliferative efficacy of the lichen extracts were screened through MTT assay against a panel of cell lines and the potent hydroalcoholic extract was selected for further evaluation against the most sensitive lung-cancer cell line A549 by implementing a wide range of microscopic and flow cytometric applications. The observations suggest that the extract could selectively induce apoptosis by augmenting ROS and disrupting the mitochondrial membrane potentiality. It was also found that the lichen-induced apoptosis was regulated by two crucial tumor suppressor genes, FOXO1, and p53, along with cell cycle inhibitor p21 which ultimately resulted in robust apoptosis through the up-regulation of pro-apoptotic BAX expression. Moreover, the extract also restricted the cancer progression by down-regulating the PALLADIN expression. Further, an LC-MS-based metabolomic profile highlighted a number of depsides, depsidones and dibenzofurans, which included atranorin, physodalic acid, salazinic acid, constictic acid and usnic acid. Then, an in silico docking with these lichen-derived metabolites against the PI3Kα receptor predicted these compounds has a binding affinity close to a standard PI3Kα inhibitor copanlisib. The study concludes that the extract restricts lung cancer possibly through the PI3Kα/FOXO1 axis and thus Parmelinella wallichiana represents a potential resource for anti-lung cancer drug development in future.