The Growth Inhibition Of PTEN Low Expressed Breast Cancer Cells Induced By Combinational Therapy With Lapatinib And Scr Inhibitor-AZD0530

Background:The biological targeted therapy for producing and molecular mechanisms of breast cancer is of high specificity and relatively low toxicity, and is currently one hotspot in the field of treatment for the breast cancer. Lapatintib is in the role of type 1 and type 2 Epidermal Growth Factor Receptor (EGFR/ErbB, a kind of tyrosine kinase receptor) blocker by inhibiting PI3K signal transmission, and induce tumor cell apoptosis. It has been proved by clinical trials that lapatinib can better inhibit tumor cell growth and bring a new way for breast cancer treatment by using independently or combination chemotherapy. However some patients with ErbB2 overexpessing tumors fail to respond to initial ErbB2-targeting treatment (primary resistance), or develop resistance to ErbB2 inhibitor after continuous treatment even with initial responses (acquired resistance). Thus, it is imperative to understand the mechanisms of resistance and rationally design clinically applicable approaches to overcome it.Aithough the mechanistic understanding of resistance is still under study, the genetic alterations of the key signaling molecules and pre-existed or developed other compensatory to the targeted signaling pathways maybe the two major categories of resistance mechanisms. PTEN (Phosphatase and Tensinhology Deleted from Chromosome 10), also a variety of adanced cancer gene mutated in multiple lesions (Mutated in Multiple Advanced Cancers,MMAC1) is the first known tumor supressor genes with dual phosphatase activities. Loss of PTEN contribute to the cell survival and multiple oncogenesis. However, the role of PTEN on the effect of target therapy is yet unclear.Objective:To investigate the cross talking between the PTEN lower expression and tumor sensitivity to ErbB-targeted reagent. and try to increase the sensitivity with combined therapy.Methods:PTEN-shRNA was introduced into the PTEN expressed cell line (MDA-MB-231, M231) in order to constructe PTEN knockdown cell (M231-PTEN-shRNA). After treated by Lapatinib and AZD0530, cell growth inhibition is measured by MTT, cell cloned formation ability is determined by cloning formation experiment, p-Akt-473 and p-Src-416 protein is detected by Western-blotResults:Compared to the control group, the M231-PTEN-shRNA cells were more resistant to Lapatinib; Compared to single reagent, combined treatment with Lapatinib and AZD0530 could obviously inhibit the growth and cloning information in both groups; In PTEN-deficient cell, Lapatinib and AZD0530 could inhibit the phosphorylation of Akt-S473 and Src-Y416 respectively; Both phosphorylation of Akt-S473 and Src-Y416 were dramatically inhibited by combinational therapy.Conclusion:The lower expression of tumor-suppressor genes PTEN in breast cancer can confer Lapatinib resistance; Src inhibitor can sensitize the Lapatinib-resistant cell to Lapatinib. The sensitization maybe mediated through synergetic decreasing the activation of Akt-S473 and Src-Y416.