The Expression Of Tumor Suppressor PDCD4 In Endometrioid Endometrial Carcinomas And Clinico-pathological Significance

Objective:Endometrial cancer(EC)is the fourth most common cancers in females behind breast,colorectal and lung cancer.EC can be classified into type ? and type ? based on etiology,clinical behavior and pathological characteristics.Type I is estrogen-dependent endometrioid endometrial carcinomas(EEC),while type ? is non-endometrioid endometrial carcinomas(NEEC).Endometrioid endometrial carcinomas accounts for 70-80%of new sporadic cases,and are related to unopposed estrogen stimulation.EC is often diagnosed in its early stages due to early clinical signs such as abnormal uterine bleeding and vaginal discharge.For the women in early stage,surgery is the best choice of treatment and the 5-year survival rate is around 96%.However,some EC women in advanced stage develop abdominal or pelvic pain,abdominal distension,early satiety,or change in bowel or bladder function,the survival rate dramatically decreases.Although these patients in advanced stage are traditionally treated using chemotherapy,radiotherapy and hormonal therapy,there are still many patients who are less sensitive to present therapy.Therefore,the finding of novel molecular biomarkers will be helpful for the early diagnosis and treatment of EC patients.Programmed cell death 4(PDCD4)was first discovered as a gene up-regulated after initiation of apoptosis.Subsequently,it has been identified as a novel tumor suppressor gene that plays an important role in inhibiting tumorigenesis and tumor progression at both transcriptional and translational levels.Several studies have shown that PDCD4 affects the transcription of specific genes by modulating the activities of certain transcription factors,such as c-Jun,Spl and p53.PDCD4 suppresses protein ranslation in two different ways:eIF4A-dependent mechanism(PDCD4 interacts with the eukaryotic translation initiation factor eIF4A to inhibit the RNA helicase activity of eIF4A),and eIF4A-independent mechanism(PDCD4 directly interacts the poly(A)-binding protein(PABP)through the RNA binding domains and regulates protein translation).PDCD4 is expressed ubiquitously in normal tissues including liver,kidney and brain,but down-regulated or lost in various human tumors,such as lung,colorectal,breast and ovarian cancers.However,the expression of PDCD4 in EEC patients and clinico-pathological significance remain unclear.In the present study,we aim to detect the expression status of PDCD4 in endometrioid endometrial carcinoma(the most common type of EC),control endometrium,KLE(endometrial cancer cell line)and control endometrial glandular epithelial cells,and analyze the correlations between PDCD4 expression and clinico-pathological parameters of EEC patients.Methods:1.qRT-PCR was used to detect the expression levels of PDCD4 mRNA in control endometrium and EEC tissues.2.Western blot was used to detect the expression levels of PDCD4 in control endometrium and EEC tissues.3.Immunohistochemistry technique was used to detect the expression levels of PDCD4 in control endometrium(including proliferative and secretary phase of endometrium)and EEC tissues.4.Immunocytochemistry technique was used to detect the expression levels of PDCD4 in control endometrial glandular epithelial cells and EC cell line KLE.5.GraphPadPrism 5(GraphPad Software,Inc.,La Jolla,CA,USA)was used for statistical analysis.p<0.05 was considered to indicate a statistically significant difference.Results:1.The expression levels of PDCD4 mRNA in control endometrium and endometrioid endometrial carcinoma tissues detected by qRT-PCRqRT-PCR was used to detect expression of PDCD4 mRNA in 15 cases of fresh frozen EEC tissue and 18 cases of endometrium as control.Our results showed that there was no difference between expression of PDCD4 mRNA in EEC tissue and control endometrium(p=0.88).2.The expression levels of PDCD4 protein in control endometrium and endometrioid endometrial carcinoma tissues detected by western blotWestern blot was used to detect expression of PDCD4 protein in 15 cases of fresh frozen EEC tissue and 18 cases of endometrium as control.Our results showed that there was no difference between expression of PDCD4 protein in EEC tissue and control endometrium(p=0.10).3.The expression levels of PDCD4 protein and cell location in control endometrium(including proliferative and secretary phase of endometrium)and EEC tissues detected by IHC(1)We collected 70 formalin-fixed,paraffin-embedded control specimens(including 36 proliferative and 34 secretary phase of endometrium)and 52 EEC samples,and we found that PDCD4 staining was mainly existed in the cytoplasm of control endometrial glandular epithelial cells and EEC cells.(2)According to the statistical analysis,there was significantlyincreased PDCD4 expression in the proliferative phase of control endometrium tissues compared with the secretory phase of control endometrium(p<0.001).(3)There was significantly decreased PDCD4 expression in moderately or poorly differentiated EEC tissues compared with the proliferative phase of control endometrium(p<0.001),and the PDCD4 expression in well differentiated EEC samples was higher than that in the secretory phase of control endometrium(p<0.001).However,no statistically significant difference in PDCD4 staining was observed between the proliferative phase of control endometrium and well differentiated EEC tissues,as well as between the secretory phase of control endometrium and moderately or poorly differentiated EEC tissues.4.The expression of PDCD4 in human endometrial cancer KLE cells and control endometrial glandular epithelial cells detected by ICC(1)The results from PDCD4 staining showed that PDCD4 immunostaining in control endometrial glandular epithelial and human endometrial cancer KLE cells was mostly localized in the cytoplasm.(2)Poorly differentiated human endometrial cancer KLE cells showed weak PDCD4 staining,which is similar with the control endometrial glandular epithelial cells.5.The associations of PDCD4 protein expression in endometrioid endometrial carcinoma tissues with clinicopathologic parameters of patientsThere were no significant correlations of PDCD4 expression with age,the depth of myometrial invasion,FIGO stage,ER and PR.However,PDCD4 expression was significantly associated with the degree of tumor differentiation.The PDCD4 level in well differentiated EEC tissues was higher than that in moderately or poorly differentiated EEC group(p<0.01),which suggests that PDCD4 expression may correlate with the malignant progression of EEC patient.Conclusion:1.PDCD4 positive staining was mainly located in the cytoplasm of endometrial glandular epithelial cells,and the staining index of PDCD4 in the proliferative phase was significantly higher than that in the secretory phase of control endometrium.2.There was significantly decreased PDCD4 expression in moderately or poorly differentiated EEC tissues compared with the proliferative phase of control endometrium.3.The expression of PDCD4 was significantly correlated with the degree of differentiation of tumor,and the expression of PDCD4 in the well differentiated endometrial carcinoma was significantly higher than that in the moderately or poorly differentiated group.It indicates that PDCD4 plays an important role in the differentiation of endometrial carcinoma,suggesting that PDCD4 can be used as a potential indicator for evaluating tumor malignancy in patients with endometrial carcinoma.Originality:1.We found that expression of PDCD4 in ECC tissue with moderate and poor differentiation was significantly decreasedcompared with the proliferative phase of control endometrium,and expression of PDCD4 was associated with differentiation of ECC.Our study reveals that PDCD4 may be one target in the therapy of ECC and lays a foundation for investigating the role and mechanism of PDCD4 in ECC.2.We also found that the expression of PDCD4 in proliferative and secretoryphase of control endometrium was significantly different,suggesting that the expression of PDCD4 in the endometrium was regulated by the ovary hormones.Limitation:In the present study,the number of fresh specimens collected is small,in vitro and in vivo experiments have not been conducted.We will continue to explore in our ·future research.