Suppression Of Proliferation And Metastasis Of Prostate Cancer Cells By Overexpression Of NDRG2 Gene

Prostate cancer is the most common cancer and the second leading cause of cancer-related deaths in the male population of the United States. Meanwhile, with the entering into old-age society, it is becoming more common in China. Prostate cancer metastasis has obvious characteristics, which bone is the most frequent target organ. Bone metastasis significantly decreases the patients'quality of life, and causes tremendous morbidity, including pain, impaired mobility, pathologic fractures, spinal cord compression, which are mostly caused by bone destruction. In spite of androgen deprivation therapy, radiation and chemotherapy, disease progression and metastasis occur in most cases.N-myc Downstream Regulated Gene 2 (NDRG2), is a member of the NDRG family. And it has been investigated in human nervous system disorders and cancers. Furthermore, it is reported that NDRG2 expression is down-regulated in a variety of carcinomas, including liver cancer, pancreatic cancer, thyroid cancer and meningioma, suggesting a possible role for NDRG2 in tumor suppression. In recent studies, it is reported that loss of NDRG2 expression in hepatocellular carcinomas was significantly correlated with aggressive clinicopathologic features of hepatocellular carcinomas patients, and up-regulation of NDRG2 contributes to the suppression of liver cancer metastasis. Meanwhile NDRG2 has an amino acid sequence highly related to that of its homologue NDRG1 (57% homology), which has been identified as a candidate suppressor of metastasis in colon and prostate cancers.Our previous study showed that there were significant different expression rates of NDRG2 between benign prostatic hyperplasia tissues and prostate cancer(P <0.05). Furthermore, we investigated the expression of protein of NDRG2 protein in prostate cancer cells by respectively Western-blot. The results showed that NDRG2 protein was significantly reduced in prostate cancer cells compared with normal prostate epithelial cells. The results suggested that NDRG2 may associate closely with initiation and progress of prostate cancer. To investigate the functions of NDRG2 in proliferation and metastasis of prostate, especially in bone metastasis of prostate cancer, we chose PC-3 cells for our experiments, which were origin from bone metastasis of prostate cancer.This research observed the effects on the proliferation and metastasis of prostate cancer by elevating NDRG2 expression. It would help us understand the functions of NDRG2 in prostate cancer. The researches what we did included two parts.1. The effect of adenovirus-mediated NDRG2 gene overexpression on the proliferation and apoptosis in prostate cancer cellsRecombinant adenovirus vector were infected into prostate cancer cells in vitro. The NDRG2 protein expressions in the cells infected with Ad-NDRG2 and Ad-LacZ were determined by Western-blot respectively. Plate colony formation and MTT assay were used to determine the effect of proliferation of the cells. The variation of cell apoptosis was detected by flow cytometry. The changes of cells morphology were observed under light microscope. After infected by adenovirus, the NDRG2 protein expression in the cells was verified. With the MTT assay and Colony formation, NDRG2 exhibited significant inhibition of prostate cancer cells(P <0.05). The apoptosis rate of the cells infected with Ad-NDRG2 was significantly higher than control group and Ad-LacZ group (P <0.05). Under light microscope, the Ad-NDRG2 group cells became round and sicker than other two group cells. These data suggested that NDRG2 inhibited the growth and proliferation of prostate cancer cells. Furthermore, it promoted apoptosis of prostate cancer cells in vitro.2. The impact of NDRG2 overexpression on the invasion and metastasis of prostate cancer cells in vitro or vivoPC-3 cells were infected with recombinant adenovirus vector in vitro. Furthermore, the protein expressions of NDRG2, MMP-2, MMP-9 in the cells infected with Ad-NDRG2 and Ad-LacZ were determined by Western-blot respectively. Invasion and migration of PC-3 cells were measured by transwell chamber assay and erasion trace test. Immunohistochemistry methods were used to determine expressions of NDRG2 in vivo. HE staining and X-ray tests could help us survey the bone metastasis and bone destruction. After the overexpression of NDRG2, it had been verified that the expression of MMP-2 and MMP-9 became low. The numbers of PC-3 cells that invaded or migrated the inferior chamber in the Ad-NDRG2 group were significantly decreased as compared with the control group and the Ad-LacZ group (P <0.01). Erasion trace tests showed that the migration distances of the cells in Ad-NDRG2 group were shorter than the control group and the Ad-LacZ group ( P < 0.05 ) . Immunohistochemistry, HE staining and X-ray tests showed that NDRG2 overexpression inhibits bone destruction and metastasis by prostate cancer cells. These data suggested that NDRG2 gene could significantly inhibit invasion of the PC-3 cells, which might play an important role in metastasis of prostate cancer, especially in bone metastasis.In conclusion, NDRG2 may play an important part in prostate cancer. Its functions may include many aspects such as inhibition of proliferation and metastasis, promoting apoptosis of prostate cancer cells, etc. Especially, NDRG2 may inhibit bone metastasis of prostate cancer. Further exploration on the molecular mechanism of NDRG2 modulation may offer a novel approach for treating human prostate cancer. Especially, targeting NDRG2 in tumors may be an effective means of treating bone metastasis in prostate cancer patients.