Investigation Of The Inhibitory Activities Of Cucurbitacin B And Gracillin Against Cancer Cells

Cancer is a serious threat to human health,and thus the research of finding new anticancer drugs is becoming more and more important.In this study,from 21 compounds extracted from plants,we discovered cucurbitacin B and gracillin that could significantly inhibit the proliferation of human liver cancer HepG2 cells.With the CCK-8 assay,we found the viability of HepG2 cells decreased in response to the increasing concentrations of cucurbitacin B or gracillin.In the treatment concentration range of 20 nM to 10 μM,the inhibition rate of cucurbitacin B on the growth of human normal liver cells HL-7702 is significantly lower than that on HepG2 cells.We also found that gracillin can effectively inhibit the proliferation of human breast cancer MDA-MB-231 cells.Fluorescence staining and flow cytometry revealed that these two compounds can induce apoptosis in HepG2 cells.Western blot analysis of the changes of apoptosis-related proteins in cancer cells treated with cucurbitacin B or gracillin showed that the treatment of cucurbitacin B or gracillin could cause PARP cleavage and caspase 3 activation,further indicating that these two compounds could induce cancer cell apoptosis.Through wound healing assays,we found that cucurbitacin B could effectively inhibit the migration ability of HepG2 cells,and gracillin can effectively inhibit the migration ability of MDA-MB-231 cells.In order to explore the molecular mechanism of the anticancer activity of the triterpenoid cucurbitacin B,we performed miRNA sequencing on HepG2 cells treated with cucurbitacin B,we observed the changes of miRNA expression profile in HepG2 cells before and after cucurbitacin B treatment.For several miRNAs with obvious changes in the sequencing study,we used qPCR to confirm their expression alterations,and found that miR-423-5p,miR-1307-5p and miR-3529-3p showed changes consistent with the microRNA sequencing study results.Moreover,these miRNAs have the potential to target and regulate some oncogenes in human liver cancer,which indicates that these miRNAs may play a role as tumor suppressor in cells.This indicated that cucurbitacin B could exhibit anti-tumor activity by regulating the expression of these miRNAs in HepG2 cells.In summary,we discovered that cucurbitacin B and gracillin could inhibit the proliferation,promote the apoptosis,and reduce the migration of cancer cells.We also revealed that cucurbitacin B treatment could alter the expression of miR-423-5p,miR-1307-5p and miR-3529-3p in HepG2 cells.This study built the primary base for dissecting the cancer suppressive mechanisms of plant active compounds and exploring anticancer therapeutics with high efficacies and low side effects.