l-Mimosine blocks cell proliferation via upregulation of B-cell translocation gene 2 and N-myc downstream regulated gene 1 in prostate carcinoma cells

Abstract

L-Mimosine, an iron chelator and a prolyl 4-hydroxylase inhibitor, blocks many cancer cells at the late G1 phase. B-cell translocation gene 2 (Btg2) regulates the G1/S transition phases of the cell cycle. N-myc downstream regulated gene 1 (Ndrg1) is a differentiation-inducing gene upregulated by hypoxia. We evaluated the molecular mechanisms of L-mimosine on cell cycle modulation in PC-3 and LNCaP prostate carcinoma cells. The effect of L-mimosine on cell proliferation of prostate carcinoma cells was determined by the [3H]thymidine incorporation and flow cytometry assays. L-Mimosine arrested the cell cycle at the G1 phase in PC-3 cells and at the S phase in LNCaP cells, thus attenuating cell proliferation. Immunoblot assays indicated that hypoxia and L-mimosine stabilized hypoxia-inducible factor-1α (HIF-1α) and induced Btg2 and Ndrg1 protein expression, but downregulated protein levels of cyclin A in both PC-3 and LNCaP cells. L-Mimosine treatment decreased cyclin D1 protein in PC-3 cells, but not in LNCaP cells. Dimethyloxalylglycine, a pan-prolyl hydroxylase inhibitor, also induced Btg2 and Ndrg1 protein expression in LNCaP cells. The transient gene expression assay revealed that L-mimosine treatment or cotransfection with HIF-1α expression vector enhanced the promoter activities of Btg2 and Ndrg1 genes. Knockdown of HIF-1α attenuated the increasing protein levels of both Btg2 and Ndrg1 by hypoxia or L-mimosine in LNCaP cells. Our results indicated that hypoxia and L-mimosine modulated Btg2 and Ndrg1 at the transcriptional level, which is dependent on HIF-1α. L-Mimosine enhanced expression of Btg2 and Ndrg1, which attenuated cell proliferation of the PC-3 and LNCaP prostate carcinoma cells.

High mobility group protein-mediated transcription requires DNA damage marker γ-H2AX

“…Induction of TGFβ1 signaling was monitored by immunodetection of phosphorylated SMAD2 (pSMAD2). As expected, L-mimosine and TGFβ1 treatment decreased the levels of cyclin A2 (CCNA2) indicating cell cycle arrest [15,20,21]. Hmga2 transfection minimally reduced CCNA2 levels.…”

“…In addition, several reports suggest an increase of H2AX-S139ph during cell cycle progression due to DNA replication stress [18,19]. Thus, to discriminate between transcription-related H2AXS139ph and DNA replication stress-induced H2AXS139ph, we used L-mimosine, a cell cycle inhibitor that is known to increase DNA replication stress [20,21]. Protein extracts of MLE-12 cells that were either transfected with Hmga2 or treated with L-mimosine or TGFβ1 were analyzed by WB (Supplementary information, Figure S3C).…”

The role of NDRG1 in the pathology and potential treatment of human cancers

“…A range of prostate cancer specimens analysed by immunohistochemistry have shown that NDRG1 expression is lower in neoplastic when compared with adjacent normal tissues 19. This finding was further substantiated by the discovery of an inverse relationship between the Gleason grade of the cancer with NDRG1 expression levels, where a higher grade corresponds to poorly differentiated tumours with low NDRG1 protein expression 58 59. This finding is also observed in colon cancer where the expression of NDRG1 declines as normal colonic epithelium progresses to carcinoma 60.…”

Expression of B-cell translocation gene 2 is associated with favorable prognosis in hepatocellular carcinoma patients and sensitizes irradiation-induced hepatocellular carcinoma cell apoptosis in vitro and in nude mice

“…Future studies would confirm BTG2 as a prognostic marker for HCC patients, and further investigate the usefulness of BTG2 as a therapeutic target for HCC patients. BTG2 is a member of the anti-proliferative family of proteins (25), and plays an essential role in regulating cell proliferation, apoptosis and DNA repair (13,26,27). Several previous studies have reported that BTG2 expression was reduced in various human cancers including renal cell carcinoma, prostate cancer, gastric cancer, melanoma, breast cancer and lung cancer (8,(16)(17)(18)(19)(20).…”