Abstract
Testing the roots of Wild yam (Dioscorea villosa extract (WYE) in vitroconsistently induced cell death at low IC50 concentrations in many types of cancers, including glioblastoma, melanoma, colon cancer, neuroblastoma, and breast cancer. However, reports also demonstrate that WYE contains detergent steroidal saponin surfactants, which act on contact to reduce oil-water interfacial tensions causing disintegration of the bio-lipid membranes. In the current investigation we separated cell death from saponins from its biological effects that occur at sub-lethal doses, where lytic cell death is not an interfering variable in MDA-MB-231 triple-negative breast cancer cells. Moreover, we confirmed the inverse relationship between rising saponin content with destruction to plasma and mitochondrial membranes, concurrent to toxicity in 2D and 3D cell cultures. Once appropriate sub-lethal concentrations were established, we monitored the changes in whole transcriptomic (WT) mRNA miRNA. Also, the intergenic non-coding RNAs concurrent to the biological cell proliferation studies, spot test of antibody-protein arrays, and an ELISA were documented. The results indicate that at sub-lethal concentrations of WYE, the microarray data show 346 differentially expressed genes (DEGs) of 48,226 transcripts tested; 166 upregulated and 180 downregulated. Upregulated DEGS reflected immune-stimulating effects on TNF signaling, COX2, cytokine release, and elevated cholesterol/steroid biosynthesis. Downregulated DEGs reveal extensive damage to cell cycle processes, including loss of transcripts for cell division cycle (CDC) genes (25A,45,6,7, A2, A7, A7L,8) cyclins (CCN) (A2, B1, B2, E2, F), cyclin-dependent kinases (CDKs), centromere proteins (CENP), kinesin family members (KIFs), and polo-like kinases (PLKs) with exception to a corresponding up-regulated DEG for p21 gene CDKN1A. The transcriptome data matches cytostatic effects observed in a 6-day proliferation study. It was concluded that WYE mediates a saponin lytic effect by direct contact and this breast cancer cell model has two different biological consequences at lower concentrations and independent of cell death, including pro-inflammatory and collapse of the cell cycle effects.