| Objective: To investigate the changes of chemosensitivity in ER-positive breast cancer after tamoxifen(TAM)resistance,and to look for sensitive chemotherapeutic drugs and corresponding molecular markers for clinical treatment of TAM-resistant patients.Methods: TAM-resistant cell lines were established in ER-positive breast cancer cell lines by low-concentration continuous TAM induction.CCK-8 method was used to verified their resistance to TAM,flow cytometry was used to detect cell cycle,transwell migration test was used to detect cell migration ability,and Western blot was used to detect the expression of relevant protein levels.Target genes involved in TAM resistance were identified by gene chip and bioinformatics,and their functions were validated in established drug resistance models.TAM-resistant and sensitive cell lines were treated with Adriamycin(ADR),paclitaxel(PTX)and cisplatin(CP)at different concentrations,and its sensitivity to different chemotherapeutic drugs was evaluated.Small interfering RNA(siRNA)was used to change the expression of target genes in drug-resistant cells and the changes of cell sensitivity to chemotherapeutic drugs were detected.The clinical information and detailed treatment plan of ER-positive breast cancer patients with recurrence and metastasis after TAM treatment were collected.The follow-up chemotherapy effect was tracked and its remission to variouschemotherapy schemes was also evaluated.At the same time,tissue samples of patients before and after treatment were collected to verify the results of in vitro experiments.Results: TAM-resistant MCF-7R and T47 DR cells were successfully induced by low concentration continuous induction in MCF-7 and T47 D cells.Morphologically,TAM-resistant cells were flatter than wild-type cells,mainly pointed and polygonal,arranged irregularly and dispersedly,closer to mesenchymal cells.Flow cytometry showed that cells decreased in G0/G1 phase and increased in S phase after TAM resistance,suggesting that cell proliferation was enhanced.Transwell assay showed that TAM-resistant cells were more invasive than TAM-sensitive cells.Western blot results showed that the levels of P21 and E-cadherin protein decreased and ER,HER2,cyclinD1 and vimentin protein increased in cells after TAM resistance,which was consistent with the results of cell function test and clinical characteristics.Bioinformatics and database analysis showed that oncogene c-MYC might be involved in TAM resistance in ER-positive breast cancer.Similar to the above results,Western blotting results showed that c-MYC and its upstream pathways p-AKT and beta-catenin were significantly elevated in TAM-resistant cells than in wild-type cells,and silencing c-MYC by siRNA reversed the resistance to tamoxifen.Furthermore,in 28 patients with TAM-resistant recurrent metastatic breast cancer,immunohistochemical(IHC)results showed that c-MYC expression was low in the primary tumors before TAM treatment,but significantly increased in the recurrent metastatic tumors after TAM treatment.Compared with wild-type ER-positive breast cancer cells,TAM-resistant cells were less susceptible to ADR and PTX,but more susceptible to CP.Western blotting showed that the expression of c-MYC in MCF-7R cells treated with CP was significantly decreased,and the sensitivity of cells toCP can be significantly reduced by Using siRNA to knock out c-MYC expression in MCF-7R cells.Furthermore,the clinical remission rate of cisplatin-based chemotherapy was significantly higher than other chemotherapy regimens in TAM resistant patients.Conclusions: ER-positive breast cancer showed increased proliferation and invasiveness after TAM resistance,and showed higher sensitivity to CP.c-MYC is involved in TAM resistance but improving the sensitivity of cisplatin in ER-positive breast cancers.Thus,cisplatin may be a preferred chemotherapeutic agent for TAM-resistant patients with high c-MYC expression.Objective: To assess the predictive role of pretreatment ki67 and Ki67 changes in breast cancer patients treated with neoadjuvant chemotherapy(NAC)in various molecular subtypes.Methods: 1010 breast cancer patients who had undergone anthracycline and taxane-based NAC from January 2012 to July 2017 were retrospectively analyzed.Clinical and pathological parameters of the patients were retrieved and the predictive factors for NAC response were evaluated.Results: 705 patients showed clinical remission(c Res),and 131 patients acquired pathologic complete response(p CR).Patients with higher pretreatment Ki67(? 14%)(P < 0.001),tumor size ? 4 cm(P < 0.001),and positive clinical nodal(P = 0.03)had better clinical therapy response,while patients with negative ER and PR(P < 0.001),higher pretreatment Ki67(? 14%)(P < 0.001),and tumor size < 4 cm(P = 0.038)were more probable to attain p CR.The pretreatment Ki67 could be used as a predictor of NAC only in luminal subtypes,and 25.5% were identified as an ideal cut-off point to differentiate the c Res from non-c Res cases(P < 0.001).Although a decrease in Ki67 had been found in almost all molecular subtypes after NAC,no statistically significant differences were found in the decrease of Ki67 were validated between the c Res and non-c Res group in HER2-rich and triple-negative subtypes(P = 0.488 and P = 0.111,respectively).Conclusions: The best cut-off for pretreatment Ki67 in predicting the connection with the tumor size lessening was 25.5% in luminal subtype.Aggressive adjuvant systemic treatments should be considered for patients with HER2-rich and triple negative subtype who exhibit tumor shrinkage in NAC but still have high levels of Ki67. |
PDF Full Text Request