| Background: Breast cancer is a kind of female malignant tumor which has higer morbidity and mortality in the world.Nowadays surgery therapy,radiotherapy,chemotherapy and endocrine therapy have become routine methods for breast cancer.But the therapeutic effectiveness is affected because of the limitations of the above methods.So it is very important to study intensively the biological behavior of breast cancer,find new therapeutic targets and then research new targeted therapy drugs.P16 is an important cyclin dependent kinase inhibitor inhibiting cell cycle progression.The abnormality of P16-cyclin Ds-CDK4/6-Rb-E2 Fs pathway is the most common events in the process of tumor.The cyclin Ds can combine with and activate CDK4/6,then the Rb protein is phosphorylated.The result is that E2 F is released,cells are drived from G1 phase to S phase and then cell proliferation is promoted.P16 could inhibit the phosphorylation of CDK4/6 on Rb protein and block the proliferation of cells.Expressing loss of p16 protein has been found in many human tumors.But p16 was up-regulated in other tumors such as breast cancer,ovarian cancer and HPV related squamous cell carcinoma.We found in previous study that p16 protein up-regulated in breast cancer,accompanied with translocation of p16 from nucleus to cytoplasm.However,the mechanism of p16 cytoplasmic translocation was still not clear.Studies showed thatD84 of p16 protein could interact with CDK4 R24 by electrostatic attraction.On this basis,we suppose that p16 cytoplasmic translocation closely relate with CDK4 in breast cancer.In this study,we will firstly detect the expressions of p16 and CDK4 proteins in breast cancer and analyze their subcellular localizations by immunohistochemistry and immunofluorescence and then explore preliminarily the relationship of p16 cytoplasmic translocation with CDK4 protein.Purposes: This study aims to explore preliminarily the relationship of p16 cytoplasmic translocation with CDK4 protein in breast cancer.Methods: The expressions and subcellular localizations of p16 and CDK4 proteins from 93 cases of breast cancers were detected by immunohistochemistry.Then relationship of p16 cytoplasmic translocation with CDK4 protein was analyzed and verified by immunofluorescence.Results: The positive rate of p16 in breast cancers(invasive ductal carcinomas)was 66.67%(62/93)with a diffused staining in both the nuclei and cytoplasm.On the contrary,it only showed a nuclear staining of occasional cells in normal breast tissues.Further analysis showed that the positive rates of p16 protein expressions in nucleus/cytoplasm,cytoplasm and nucleus were 70.97%(44/62),17.74%(11/62)and 11.29%(7/62),respectively,in the cases with p16 positive staining.The positive rate of CDK4 in breast cancers(invasive ductal carcinomas)was 84.95%(79/93)with a diffused staining in both the nuclei and cytoplasm.On the contrary,it only showed a nuclear staining of occasional cells in normal breast tissues.Further analysis showed that the positive rates of CDK4 protein expressions innucleus/cytoplasm,cytoplasm and nucleus were 56.96%(45/79),26.58%(21/79),and 16.46%(13/79),respectively,in the cases with CDK4 positive staining.The co-positive rate of p16 and CDK4 proteins in breast cancer was 64.52%(60/93).And the rates of the two proteins expressions in nucleus/cytoplasm,cytoplasm and nucleus were 18.33%(11/60),11.67%(7/60)and 8.3%(5/60),respectively,in the 60 cases with co-expression of p16 and CDK4.The results of immunofluorescence showed that both p16 and CDK4 proteins mainly located in nucleus/cytoplasm,and they were co-located with each other.Conclusions: 1.P16 protein up-regulated in breast cancers and located mainly in nucleus/ cytoplasm.2.CDK4 protein up-regulated in breast cancers and located mainly in nucleus/ cytoplasm.3.P16 cytoplasm translocation maybe related with CDK4 in breast cancers.. |
