Trastuzumab Synergized The Inhibition Of Histone Deacetylase Inhibitor Sodium Butyrate On Breast Cancer Cell Line With Different HER2-expression.

Background:Cancer is a leading cause of death worldwide. Incidence rates of overall cancer are rising as soon as the situations become more serious among the contamination, the pressure and the rhythm. Breast cancer is the most common in women. According to the latest report of CA CANCER J CLIN, the rates of estimated new cases and estimated deaths were up to 28% and 15% in 2010, respectively. In the cities of China, the incidence of breast cancer is increasing at the rate of 20-30% in women. The mainstream therapeutic strategies of breast cancer include surgical resection, traditional chemotherapy, endocrinotherapy, which benefit the majority of breast cancer patients. However, the incidence of relapse or mortality in breast cancer paients is still high.Trasutuzumab, a recombinant humanized monoclonal antibody, is directly against the extracellular domain of HER2 to block the form of homodimers or heterodimers and the intracellular signaling ways in downstream and to inhibit the growth of the tumor. Clincal trials indicate that the objective response rates (ORR) ranges from 12% to 34% when treated with single Trastuzumab monotherapy in breast cancer patients. Regretfully, as the majority of breast cancer patients, which initially respond to Trastuzumab, begin to progress again within 1-year. further, diease-free survival(DFS) could be up to 50% when combined with cytotoxic drugs, such as paclitaxel, anthracyclin, et al. Previous study indicated that Trastuzuamab inhibited the proliferation of over-expressing HER-2 breast cancer cells by up-regulating p27Kip1.Clinical studies have found that the application of HDACis treatment is effective to hematopoietic malignancies and certain solid tumors, such as epithelial ovarian cancer, non-small cell lung cancer (NSCLC). NaB (Sodium Butyrate) belongs to the Histone Deacetylase Inhibitor (HDACi) family. Targeting at the zinc-dependent Histone Deacetylases, it may induce accumulation of acetylated histones, leading to the relaxation of chromatin structure and better access for transcriptional machinery proteins. Previous study indicated that NaB up-regulated p27Kip1 protein of MCF-7 cells to inhibit the cell proliferation, induce cell cycle arrest and apoptosis.In this study, we detected the anti-tumor effect of NaB and Trastuzumab on proliferation, cell cycle and apoptosis of breast cancer cell lines, and explored the mechanism of potential anti-tumor effect of NaB and Trastuzumab.Methods:Breast cancer cell lines were treated with different concentration of NaB and Trastuzumab by MTT assay, respectively. As the apoptotic features, apoptotic rates and the changes of cell cycle of breast cancer cells were detected by flow cytometry. The mRNA levels of HER-2 and p27Kip1 were analyzed by RT-PCR. The expression of HER-2 and p27Kip1 protein was described in immunofluorescence.Results:NaB treatment significantly inhibited the cell proliferation, induced cell cycle arrest at G0/1 and apoptosis (P<0.05), and up-regulated the expression of p27Kip1 of breast cancer cells (P<0.05). However, Trastuzumab single-drug exhibited the proliferative inhibition, cell cycle arrest effect and up-regulated p27Kip1 expression only at the concentration of 20μg/mL to SKBR3 cells, but had little influence on apoptosis (P>0.05); the similar effects were not in MCF-7 cells and HCC1937 cells. NaB plus Trastuzumab could enhance the inhibitory effect of NaB and up-regulate p27Kip1 expression in SKBR3 cells (P<0.05), however, had little effect on MCF-7 cells and HCC1937 cells.Conclusion:Trastuzumab could synergize the inhibitory effect of NaB on the proliferation of HER-2 over-expression SKBR3 breast cancer cell line, induce cell cycle arrest and apoptosis, which might be associated with the evaluated expression of p27Kip1.