Silymarin inhibits Toll-like receptor 8 gene expression and apoptosis in Ramos cancer cell line.

Silymarin is a herbal extract containing flavonolignans, and it has inhibitory effects against the growth of different cancer cell lines by inducing apoptosis. Toll-like receptors are suggested as a novel and attractive target to treat cancer. The current study aimed at examining the mechanism of silymarin-induced apoptosis in Ramos cells and investigating its effects on TLR8 expression.

The half maximal inhibitory concentration (IC₅₀) of silymarin in Ramos cells was determined via MTT viability test while the type of cell death was tested by annexin V/propidium iodide (PI) double staining method. The activity of caspase-3 and expression of TLR8 were measured in a time-dependent manner (in IC₅₀) by colorimetric assay and real-time polymerase chain reaction (RT-PCR), respectively.

The results of MTT showed that IC₅₀ of silymarin in Ramos cells was 100 μg/ml after 48 hr treatment (p<0.01). Flow cytometry by annexin V/PI, showed that silymarin induced early/late apoptosis in this cell line (p<0.05 to p<0.01). In addition, the caspase-3 colorimetric method showed that caspase-3 increased in the Ramos cell line after treatment (p<0.01). This treatment led to a reduction in TLR8 mRNA expression in a time-dependent manner (p<0.01).

The results indicated a new mechanism in the anticancer activity of Toll-like receptor (TLR) signaling after silymarin treatment in Ramos cancer cell line. This plant could be used to develop anticancer agents inhibiting TLRs.