| Background:Hypopharyngeal squamous cell carcinoma(HSCC)is a type of Head and Neck Squamous Cell Carcinomas(HNSCC).However HSCC is not very common for just constituting approximately 5-15%of HNSCC.The HSCC patients diagnosed with advanced-stage are far more than those diagnosed due to the nonspecific nature of the early symptoms.Despite several therapeutic methods have been applied for HSCC treatment such as surgery,radiotherapy and chemoradiotherapy,the prognosis is still far from optimistic.In view of the characteristics of advanced diagnosis,poor prognosis and traditional therapies of HSCC,the identification of novel and effective prognostic biomarkers is particularly important.However,due to the low morbidity of HSCC,the collection of clinicopathological materials of HSCC patients is relatively difficult comparing with the common human malignant tumors,and the researches about the biomarkers associated with HSCC are relatively rare.PDCD4(programmed cell death 4)is a well-known tumor suppresser gene,which was first cloned from the cDNAs of the human in 1997.PDCD4 is identified to inhibit translation by binding to eukaryotic translation initiation factor(EIF)4A by the MA-3 domains or combining directly with target gene(MYB/c-MYB)coding region to exert its tumor suppressive function.PDCD4 inhibits tumor progression,infiltration and metastasis by regulating the expression of various genes.It is observed that PDCD4 expression is lost or reduced in multiple types of tumors such as lung tumor,colorectal tumor,liver tumor,glioma and varian which having important effects on the neoplastic transformation and tumor progression of the human tumor.PDCD4 suppresses proliferation and invasion of tumor cells in vitro as well as enhances the chemosensitivity of tumors;furthermore,it is also involved in some inflammatory diseases.The recent study told that PDCD4 is a functionally significant target gene of microRNA-21,and the observed inverse correlation between the expression of PDCD4 and microRNA-21 seems to be a useful prognostic marker.Overall,PDCD4 is an important tumor suppressor and a potential target for novel cancer prevention or anti-cancer treatment.Currantly,there has not been no reports about the role of PDCD4 inHSCC.PDCD4 might participate in the tumorigenesis and development of HSCC,and whether it could act as a prognostic biomarker is worthy study.Objective:In the currant research,we aimed to study the expression degree of PDCD4 protein in HSCC,the biological function of PDCD4 in HSCC cells in vivo,the correlations between PDCD4 expression and several clinicopathological parameters as well as the prognosis of HSCC patients in order to explore the role of PDCD4 in the tumorigenesis and development of HSCC and whether pdcd4 has effect on the prognosis of HSCC to identify the potential clinical value of PDCD4 in HSCC prevention and therapies.Methods:IHC(Immunohistochemistry)were used to explore the expression of PDCD4 protein in 66 HSCC tumor tissues and 35 adjacent noncancerous tissues in paraffin specimens,and the difference of PDCD4 expression between tumor tissues and adjacent noncancerous tissues was statistically detected by χ2 test according to the IHC scores.Then ten fresh HSCC tumor tissues as well as the corresponding adjacent tissue were detected by western blot.The relative IntDen(integrated density)were detected by paired t-test to explore the expression of PDCD4 protein in HSCC tumor tissues and adjacent noncancerous tissues in fresh tissues.In vitro,PDCD4 overexpression cells FaDu-PDCD4 and control cells FaDu-MOCK were obtained by transfecting FaDu cells with pEGFP-C1-PDCD4 or pEGFP-C1 plasmid.Viable cell count and CCK8(Cell Counting Kit-8)growth curve assay were conducted to study the effect of PDCD4 on the proliferation of FaDu cells;Transwell assay was performed to study whether PDCD4 had effect on the migration and invasion of FaDu cells.Unpaired t-test was used to examine the statistical differences between the compared two groups.The correlations between PDCD4 expression and several clinicopathological parameters of HSCC patients were analyzed,including age,pathological grade(differentiation degree),clinical stage and lymph node metastasis by χ2 test or Fisher test.Kaplan-Meier survival function was used to study the association of PDCD4 expression with the survival of HSCC patients.All statistical significance was carried out using SPSS 19.0 software.And all data was evaluated from at least three independent experiments.Statistical significance was established at p<0.05 in all statistical analyses.Results:Both IHC and western blot results represented that PDCD4 expression is downregulated or even lost in HSCC tumor tissue relative to adjacent noncancerous tissues.By analyzing the correlations between PDCD4 expression and several clinicopathological parameters of HSCC,the result displayed that PDCD4 expression was significantly associated with the pathological grade which is considered as the differentiation degree.In vitro,over expression of PDCD4 inhibited the growth and proliferation of FaDu cells(HSCC cell line)according to the results of viable cell count assay and CCK8(Cell Counting Kit-8)growth curve assay.As shown in transwell assay,over expression of PDCD4 also inhibited the migration and invasion of the FaDu cells.At last,bases on the survival analysis,we found the association between PDCD4 expression levels and survival in HSCC:low PDCD4 expression associated with poor prognosis of HSCC patients.Conclusions:In conclusion,the currant study represents that the expression of PDCD4 is downregulated in HSCC tumor tissue associating with differentiation and prognosis of HSCC patients and PDCD4 inhibits the proliferation,migration and invasion of the HSCC cells in vitro.All the results suggest that PDCD4 serves as a tumor suppressor as well as a prognostic marker in HSCC and may provide novel inspiration of HSCC therapies. |
