Natural isoflavones and flavones are important dietary factors for prostate cancer prevention. We investigated the molecular mechanism of these compounds (genistein, biochanin-A and apigenin) in PC-3 (hormone-independent/p53 mutant type) and LNCaP (hormone-dependent/p53 wild type) prostate cancer cells. A cell growth rate and apoptotic activities were analyzed in different concentrations and exposure time to evaluate the antitumor activities of genistein, biochanin-A and apigenin. The real time PCR and Western blot analysis were performed to investigate whether the molecular mechanism of these compounds are involving the p21 and PLK-1 pathway. Apoptosis of prostate cancer cells was associated with p21 up-regulation and PLK-1 suppression. Exposure of genistein, biochanin-A and apigenin on LNCaP and PC-3 prostate cancer cells resulted in same pattern of cell cycle arrest and apoptosis. The inhibition effect for cell proliferation was slightly greater in LNCaP than PC-3 cells. In conclusion, flavonoids treatment induces up-regulation of p21 expression, and p21 inhibits transcription of PLK-1, which promotes apoptosis of cancer cells.
Acute spinal cord injury (SCI) is two-step process that first involves the primary mechanical injury and then the secondary injury is induced by various biochemical reactions. Apoptosis is one of secondary SCI mechanisms and it is thought to play an important role for the delayed neuronal injury. The enhanced formation of nitric oxide (NO) via inducible nitric oxide synthase (iNOS) has been implicated in the pathogenesis of apoptosis in SCI. The level of .iNOS mRNA peaked at 6 hr after SCI and it declined until 72 hr after SCI in a rat model. Double-immunofluorescence staining revealed that iNOS positive cells were stained for ED-1, synaptophysin, GFAP, and oligodendrocyte marker. The terminal deoxynucleotidyl-transferase-mediated dUDP-biotin nick end-labeling (TUNEL) positive cell count was higher for the 72 hr post-SCI group than for the 24 hr post-SCI group. This cell count was also higher going in the caudal direction than in the rostral direction from the epicenter, and especially for the 72 hr group. Treatment with a selective iNOS inhibitor resulted in the reduction of TUNEL-positive cells at the lesion site. These findings suggest that nitric oxide generated by the iNOS of macrophages, neurons, oligodentrocytes, and astrocytes plays an important role for the acute secondary SCI that results from apoptotic cell death.
Purpose:To analyze the effect of the growth control on human breast cancer cells with genistein treatment and to investigate the mechanism of genistein-induced G2/M arrest in T47D and MDA-MB231 breast carcinoma cells by Cdc25C expression. Methods: We analysed the proliferartion of the two cell lines by using MTT proliferation assay, flow cytometric analysis, real-time quantitative RT-PCR and western blotting and investigated the effect of genistein on cell survival, cellular toxicity, cell cycle progression-related genes and their mRNA and protein alterations. Results: The DNA flow cytometric analysis of both cell lines treated with genistein showed a dose-dependent growth inhibition and accumulation in the G2/M phase of cell cycle. The expression of p21 mRNA and protein increased in both cell lines following genistein treatment but p27 expression was unchanged. Furthermore, decreased Cdc25C expression with decreased polo-like kinase (PLK) 1 expression and increased PLK3 expression were observed after genistein treatment. The decreased level of Cdc25C in the nucleus was associated with decreased phosphorylation of Cdc25C by PLK1. The expression of PLK3 was increased with a dose-dependent and a time-dependent manner and was associated with decreased Cdc25C expression. Check point kinase (CHK) 1 and CHK2 revealed different expression patterns each other. The CHK1 expression was independent of the presence of genestein. CHK2 expression increased in MDA-MB231 cells associated with decreased Cdc25C expression but not in T47D. Conclusion: These results suggest that genistein induces a G2/M arrest in human breast cancer cells, the mechanism of which is due, in part, to decreased in Cdc25C phosphatase by a regulatory effect of PLK1, PLK3, and CHK2 as well as increased expression of the cyclin dependent kinase inhibitor p21(WAF1/CIP1).
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