| Introduction and ObjectiveOvarian cancer is commonly encountered in clinic that is a serious danger to women's life and health, its fatality rate is the hightest among gynecological malignancies. During recent ten years, with the popularity of surgical cytoreduc-tion, constant advent of new anticancer agents, and increasingly improved program for chemotherapy strategies, the curative effect on ovarian cancer has been greatly changed and the life quality of patients evidently improved, but five -year survival rate is still 30% to 50% or so and there has been no obvious improvement made by chemotherapy in overall survival rate. One of the main reasons is that primary or secondary chemoresistance may develope in the course of chemotherapy. Many studys have shown that many kinds of mechanism such as activation of oncogene, inactivation of anti - oncogene, reduced intracellular drug concentration, altered target proteins, drug metabolism and detoxification enhanced, altered DNA repair, and inhibited apoptosis of tumor cells are involved in drug resistance of tumor which results from combined action of multiple gene, multiple factor, and multiple procedure.PTEN gene is a tumor suppressor gene, encoding a dual - specificity phos-phatase, is located on chromosome arm 10q ( 10q23. 3) and consists of 9 exons. PTEN gene abnormalities have been commonly identified in many tumor cell lines and primary tumors. PTEN protein participates in adjusting many kinds of cell signal - transduction pathway and is closely related to cellular growth, differentiation, and carcinogenesis. Mitogen -activated protein kinase (MAPK) is one of the most important membrane - to - nucleus signalling mechanisms and extracellular signal - regulated Kinase (ERK) pathway including ERK1 andERK2 is a key and classic pathway of the system, and mainly participates in adjusting cell - cycle and promotes cell proliferation and differentiation. It has been indicated that MAPK activation is closely related to carcinogenesis and development and malignancy potential of ovarian cancer. Most of scholars considered that PTEN protein could inversely regulate and control the activation of ERK/MAPK signal pathway in many ways. Recent researches have shown that the inactivation of PTEN gene and abnormal activation of ERK/MAPK signal -transduction pathway might be related to drug sensitivity and resistance of tumor.Starting from DNA, mRNA and protein level, the aim of this research was to investigate the mechanisms of PTEN gene inactivation and the correlation between PTEN gene inactivation and drug resistance in ovarian cancer. We also were to determine if ERKl/2 signal - transduction pathway was the dowmstream target of PTEN gene, and if abnormal activation of the pathway was related to drug resistance in tumor samples derived from patients with ovarian cancer. This study will provide new clews and theoretical basis for researches on new antican-cer agents, guidance to selection of clinical chemotherapy strategies, improvement of curative effect, and prevention from recurrence of ovarian cancer.MethodsFresh tumour material was obtained from 48 patients with primary epithelial ovarian cancer. Using four polymorphic markers ( D10s541, D10s583, D10sl687 and D10s2491) within and flanking the PTEN gene located in chromosome 10q 23. 3, polymerase chain reaction ( PCR) and the analysis of loss of heterozygosity (LOH) were introduced to examine LOH of PTEN gene; poly-merase chain reaction - single strand conformation polymorphism (PCR - SSCP) was introduced to examine mutation of the fifth, sixth, seventh, and eighth ex-ons where mutation of PTEN gene was frequent; reverse transcriptase polymerase chain reaction ( RT - PCR) and immunohistochemistry were applied to detection of PTENmRNA and PTEN protein expression; Western blot was introduced todetect ERK1/2 protein expression; and in the meanwhile the change of ERK1/2 activity was examined to measure its efficiency of phosphate transferase; MTT colorimetric assay was applied to measure...
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