Study The Methylation And Function Of Tumor Suppressor PLCD1in Breast Cancer

Objective: To detect the expression and epigenetic alterations ofPLCD1and its tumor suppressor function in breast cancer, and to analyzethe correlation between PLCD1methylation and clinicopathologic featuresin breast cancer patients.Methods: We used the RT-PCR and immunohistochemistry stainingto detect the expression of PLCD1in breast cancer cell lines and tissues.The GOBO database was used to analyze the correlation between PLCD1expression and histological grade in breast cancer. The epigeneticalterations of PLCD1in breast cancers were studied by MSP and BGS. Thepharmacological demethylation Aza and TSA were used to treat breastcancer cell lines for determining whether promoter methylation directlymediates PLCD1silencing. We then investigated the reationship betweenPLCD1methylation and clinical parameters in96primary breast cancerpatients by chi-square test. Colony formation assay, wound healing assayand cell cycle assay were used to evaluate the tumor suppressor function ofPLCD1. Further to evaluate the tumor-suppressive function of PLCD1invivo, tumorigenicity of MB231cells expressing PLCD1was evaluated in nude mice.Results：PLCD1was frequently expressed in human normal cell linesand tissues, but it was mostly silenced or underexpressed in breast cancercell lines and tissues. Furthermore, GSA-tumor assay showed that PLCD1expression was significantly higher in primary breast cancers characterizedwith a normal-like subtype, ER positive and early histologic gradeⅠ. Themethylation status of PLCD1was not detected in normal breast tissues, butdetected in6of9cancer cell lines and55of96primary tumors. PLCD1could significantly reduce cancer cell proliferation, migration ability,induce cell cycle G2/M arrest in vitro and inhibit tumor growth in vivo.However there was no significant correlation between the clinical featuresand methylation status of PLCD1in breast cancer.Conclusion：PLCD1is frequently methylated in breast cancer. As anovel candidate functional tumor suppressor in breast cancer, PLCD1couldinhibit tumor growth in vitro and in vivo, provide a promising biomarkerfor the diagnosis and treatment of breast cancer in early stage.