title: Harmine induces cell cycle arrest and mitochondrial pathway-mediated cellular apoptosis in SW620 cells via inhibition of the Akt and ERK signaling pathways.
abstract: Harmine, a β-carboline alkaloid isolated from the seeds of Peganum harmala, possesses both antitumor and anti‑nociceptive effects and inhibits human DNA topoisomerase. However, no detailed data are available concerning the mechanisms of harmine in human colorectal carcinoma SW620 cells. In the present study, we demonstrated that harmine inhibited the proliferation of SW620 cells in a dose-dependent manner using MTT and clone formation assays, and the IC50 value of harmine on the growth inhibition of SW620 cells for 48 h was 5.13 µg/ml. PI staining showed that harmine altered the cell cycle distribution by decreasing the proportion of cells in the G0-G1 phase and increasing the proportion in the S and G2-M phase. The expression level of cyclin D1 was decreased, while the expression of cyclin A, E2 and B1, CDK1/cdc2, Myt-1 and p-cdc2 (Tyr15) were increased, which was in accordance with the S and G2/M phase arrest. Hoechst 33258 staining revealed nuclear fragmentation, chromosomal condensation and cell shrinkage in the SW620 cells treated with harmine. Flow cytometry revealed that the percentage of apoptotic sub-G1 cells increased from 7.19 to 26.58%, while in the control group, sub-G1 cells only increased from 1.53 to 1.60%. Furthermore, early and late apoptotic cells were increased from 11.96 to 26.38% when incubated with the indicated concentration of harmine for 48 h, while in the control group, <8% of cells underwent apoptosis. JC-1 staining revealed that harmine decreased mitochondrial transmembrane potential (ΔΨm). The apoptosis of SW620 cells was also detected by western blot analysis, showing caspase-3 and -9, and PARP activation; the downregulation of Bcl-2, Mcl-1, Bcl-xL; and the upregulation of Bax. The expression of p-ERK, p-Akt (Ser473) and p-Akt (Thr308) was inhibited, and phosphorylation of downstream targets of Akt, such as p-FoxO3a and p-GSK‑3β were also attenuated. In conclusion, harmine induces cell cycle arrest and mitochondrial pathway-mediated cellular apoptosis in SW620 cells via inhibition of the Akt and ERK signaling pathways.
authors.affiliation: Department of General Surgery, First Affiliated Hospital, Jinan University, Guangzhou, Guangdong 510630, P.R. China.
authors.forename: Jiming
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of General Surgery, First Affiliated Hospital, Jinan University, Guangzhou, Guangdong 510630, P.R. China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Li
authors.affiliation: Department of General Surgery, First Affiliated Hospital, Jinan University, Guangzhou, Guangdong 510630, P.R. China.
authors.forename: Zhilong
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of General Surgery, First Affiliated Hospital, Jinan University, Guangzhou, Guangdong 510630, P.R. China.
authors.forename: Liuming
authors.initials: L
authors.lastname: Lin
authors.affiliation: Department of Biochemistry, Medical College, Jinan University, Guangzhou, Guangdong 510630, P.R. China.
authors.forename: Xiangqiang
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of General Surgery, First Affiliated Hospital, Jinan University, Guangzhou, Guangdong 510630, P.R. China.
authors.forename: Mingrong
authors.initials: M
authors.lastname: Cao
authors.affiliation: Department of Biochemistry, Medical College, Jinan University, Guangzhou, Guangdong 510630, P.R. China.
authors.forename: Jianwei
authors.initials: J
authors.lastname: Jiang
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000473:pathology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors*; D006247:Harmine / Q000494:pharmacology*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D006247:Harmine; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases