Effect Of Tumor Suppressor Gene ING4 On Proliferation Of Human Breast Cancer Line MCF-7

The process of tumor development is multiplicity and very complicated, one of the major reasons is anti-oncogene inactivation or oncogene activation. Detection of the expression and function of tumor suppressor gene is very important for revealing tumor development regularity, anticipating consequence and making the therapeutic regimen. The inhibitor of growth family is a tumor suppressor family. ING4 was identified recently through the research of the homologous series , The N-terminal and C-terminal of ING4 proteins share high homology structure with other proteins of the ING family. The C-terminal includes nuclear localization signal(NLS) with zinc fingers and highly conserved plant homeodomain(PHD) which can reconstruct chromatin structure.Early study confirmed that with the malignancy of neurogliocytoma increased, the expression of ING4 depressed in neurogliocytoma. Study used comparative genomic hybridization to detect deletion of the ING4 revealed that the detection of ING4 in human breast cancer cell lines and primary breast cancer is between 10% and 20% . It hint that the expression of the ING4 may correlate with the development of breast cancer,but the mechanism is still not clear.To confirm down regulation of the ING4 protien in breast tumours,we carried out immunohistochemical analysis;construct the plsmid pcDNA3.1/ING4,over expression the ING4 to measured the proliferative activity and discuss its mechanism.Objective: To investigate the relationship between ING4 protein expression and breast cancer; Observe the effects of ING4 gene expression on the proliferation of MCF-7.Methods: Using SABC immunohistochemistry method to investigate the protein expression of specimens from 27 breast cancer tissues and 28 benign breast tumors;Plasmid pcDNA3.1/ING4 was constructed and transfected into MCF-7 cells via liposome mediation;cell growth curves were analyzed by MTT assay; cell cycles were analyzed by flow cytometry;the stabilization cell line with ING4 was screened and verificated protein expresstion by western bolt; Colony formation assay and serum starvation experiment were performed to confirm the effect of ING4; p21, p53, bax mRNA expression was analyzed after transfecting pcDNA3.1 /ING4 by Real-time PCR.Results: 28 benign breast tumors all showed ING4 protein expressi-on,but there are 6 cases did not show ING4 protein expression in 27 breast cancer tissues , the miss rate is 22.2%. There was significant difference between breast cancer and benign breast tumors (P<0.05). Plasmid pcDNA3.1/ING4 was constructed successfully: after transfecting pcDNA3.1/ING4, compared with control group, MCF-7 cell proliferation was inhibited obviously, cells in S phase were reduced with some of thecells arrested in G1 phase, the capability of clone was decre- ased and therate of apoptosis induced by serum starvation was increa- sed;Real timePCR revealed that p21 and box mRNA expression was increased(P<0.05)but p53 has no change(P>0.05).Conclusion: The expression of the ING4 may correlate with thedevelopment of breast cancer. Over expression of ING4 can inhibitMCF-7 cell proliferation and accelerat its apoptosis by up-regulatingp21 and bax gene expression.