The MAPK/ERK signaling pathway involved in Raddeanin A induces apoptosis via the mitochondrial pathway and G2 phase arrest in multiple myeloma

Multiple myeloma (MM) is a hematological malignancy characterized by the unrestricted proliferation of plasma cells that secrete immunoglobulin in the bone marrow. Extracted primarily from Anemone raddeana regel, Raddeanin A (RA) is a natural triterpenoid saponin compound with anti-inflammatory and anti-tumor activities. However, most research on the anti-tumor effects of RA has concentrated on solid tumors, with little exploration into non-solid tumors like MM. Furthermore, there is a dearth of research investigating the interplay between RA and MM, encompassing their interaction targets and mechanisms. This study aims to delve into the biological activity and molecular mechanism of RA's anti-MM properties through the lens of network pharmacology and experimental validation. The findings from GO enrichment analysis, KEGG enrichment analysis, and molecular docking prediction suggested a potential correlation between the MAPK signaling pathway, including the MAPK1 gene (also known as ERK2), and the impact of RA on MM. Results from the CCK-8 assay revealed a time-dependent and concentration-dependent inhibition of proliferation in MM cell lines treated with RA. Notably, in the cell lines used for the test, the IC50 values for MM.1 S cells were 1.616 µM at 24 H and 1.058 µM at 48 H, for MM.1R cells were 3.905 µM at 24 H and 2.18 µM at 48 H, while for RPMI 8226 cells, they were 6.091 µM at 24 H and 3.438 µM at 48 H. The PI, Annexin V-FITC/PI, and JC-1 staining showed that RA could arrest the cell cycle in the G2 phase, cause apoptosis, and induce the change of mitochondrial membrane potential (MMP) in MM cells. Treated with RA, the Western blot analysis showed that the expression levels of Bim, Cleaved Caspase 3/9, and Cleaved PARP were increased, and the expression level of Mcl-1 was decreased in MM cells. Concurrently, the phosphorylated protein expression levels of p-ERK1/2, p-MSK1, p-P90RSK, and p-MEK1/2 were diminished following RA treatment. These results suggest that RA has the activity of anti-MM, and the MAPK/ERK signaling pathway is involved in the growth inhibition effect of RA on MM cells via cycle arrest and mitochondrial-pathway-dependent apoptosis.