Involvement Of RACK1in Regulation Of Growth And Proliferation In Cervical Carcinoma And Its Associated Mechanism

PartⅠ Positive role of RACK1in cervical carcinoma progression and itsclinical significanceObjective To investigate the expression of receptor for activated C-kinase1(RACK1)in cervical carcinoma tissues and trying to clarify its correlation to the growth, invasionand metastasis of cervical cancer.Methods Immunohistochemistry and western blot assay were used to detect theexpression of cervical cancer tissues, normal tumor-adjacent tissues as well as cervicitis.Results The expression of RACK1in cancer tissues was higher than their matchedtumor-adjacent tissues, and its level gradually increased in cervicitis, CINⅠand CIN Ⅱ-Ⅲ.The RACK1protein was higher expressed in cancers with lymphonodus metastasiscompared with those without metastasis, furthermore, the positive percentage of activeRACK1expression was significantly higher in pathological staging G3than that in G1andG2stage, besides, as expected, it was also higher in deeper higher invasion leisions, andgradually increased with the rise of surgical staging, all of the above variables werestatistically significant; and statistical significance was observed between tumor tissueswith diameter>4cm and those with>4cm.Conclusion: RACK1expression levels in cervical carcinoma carried a highcorrelation with its pathological and clinical staging along with metastasis in the currentstudy, thus, we supposed that RACK1protein may be involved in the occurrence anddevelopment of cervical cancer; it may be used as a novel target for early diagnosis and therapeutic intervention in cervical carcinoma. PartⅡ Promotive effect of RACK1over-expression on the growth ofcervical carcinomaObjective：To investigate the effect of RACK1over-expression on cervical carcinomacells proliferation and its potential role in the prognosis of cervical cancer.Methods: Constructed plasmid of RACK1was transfected into cervical cancer celllines Hela, SiHa and Caski, the stable-transfected cells were screened, examined by FlowCytometry (FCM) assay to observe their proliferative ability, and then injected into theboth flank of nude mice. In the model of tumor formation in mice, non-treatment cancercells and PBS were separately established as normal control group and negative controlgroup. Five weeks after tumor formation, tumors were taken out for preparation of paraffinsections in which Ki67expression were detected by immunohistochemistry. Proteinextracts of stable RACK1transfectants were used to detect the expression of cell cyclerelated proteins using western blotting assay. A Kaplan-Meier survival curve of patientswith different scores of RACK1expression was illustrated.Results: FCM date showed that the over-expression of RACK1significantlyenhanced the progression of G1-S phase compared with control groups. The tumorxenografts occurred at4day in over-expressed RACK1cells while at6day innon-treatment cells, and cells with RACK1over-expression also presented increasedclonogenicity with larger and faster tumor formation. Furthermore, Immunohistochemistryassay suggested that Ki67was higher expressed in cells with RACK1over-expressioncompared with control group. And in accordance with the results above, the expression ofcell cycle related proteins also changes exhibited as increased cyclin D1and decreased p21in RACK1-overexpressed cervical cancer cells, with the involvement of Akt signalingpathway. In addition, results from Kaplan-Meier survival curve showed a negative relationbetween RACK1expression and survival rate. Conclusion: Over-expression of RACK1gene can enhance the proliferation ofcervical cancer cells vitro and also increase the tumor formation in nude mice in vivo, thepotential mechanism herein may be attributed to the regulation of cell cycle relatedproteins with the involvement of Akt signaling pathway. The results above suggested apositive role of RACK1in the progression of cervical cancer. Treatment targeting RACK1may emerge as a novel strategy for cervical cancer.