| BackgroundBreast cancer is one of the most common cancers among women worldwide and a leading cause of cancer death. Currently, the strategy for breast cancer management is primarily based on the traditional prognostic and predictive factors. However, in addition to traditional prognostic factors (tumor size, lymph node stage, histological grade, histological type, and lymphovascular invasion) and predictive factors (such as estrogen receptor (ER), progesterone receptor (PR), and HER2/neu), other new reliable biomarkers are required as for designing treatment strategies and prognosis evaluation.Mammalian sterile20-like kinase1(Mst1), a serine-threonine kinase, was first identified in yeast. Mst1is wellknown to be a potent inducer of apoptosis in diverse cell types and identified as a caspase target and an amplifier of apoptotic signals. Activation of Mst1can induce cellular apoptosis via a P53-mediated pathway. PH domain and leucine rich repeat protein phosphatases (PHLPP)-Mst1pathway also plays an important role in cancer development and progression. Mst1is an interacting protein that mediates PHLPPs’ induced apoptosis. PHLPP, Akt, and Mst1constitute an auto inhibitory triangle that controls the fine balance of apoptosis and proliferation that is cell type and context dependent. PHLPP and Mst1synergize to promote a much greater increase in apoptosis compared to either protein alone. Phosphoinositide3-kinase/Akt inhibits Mst1-mediated proapoptotic signaling through phosphorylation of threonine120. Mst1is closely related to Drosophila Hippo, amajor regulator of cell proliferation and survival during development. Its ortholog Hippo pathway in Drosophila has tumor suppressor activity. Subsequent studies showed that Mst1was involved in promotion of caspase-dependent and independent apoptosis. Additionally, loss of cytoplasmic Mstl expression has been demonstrated as a marker of tumor progression, suggesting a tumor suppressor role for Mstl in human colorectal cancer. Kim et al. provided evidence that the expression levels of Mstl were significantly reduced in various lymphoma/leukemia patient samples, which implied that the loss of Mstl could contribute to tumorigenesis in hematopoietic lineages.So far, there has been no study on the significance of Mstl expression in breast cancer patients. In this study, the expression of Mstl in breast cancer and its association with clinicopathological parameters and prognosis were evaluated.Objective1. To detect the expression of Mstl in breast cancer with immunohistochemical staining.2. To observe the expression of Mstl in breast cancer and analysis its association with different clinicopathological parameters.3. To evaluate the clinical prognostic value of Mstl in breast cancer.Methods1.110patients with primary breast cancer and received surgical treatment were selected from January1997to December1998in department of Breast Surgery, Qilu Hospital, Shandong University. All patients received standard treatment following the guidelines.2. All110patients were females and aged from25to75years old, with a median age of46.9years old. There were63patients younger than40years old,63patients older than40years old.3. According to pathological tumor size,71patients had tumors larger than or equal to2cm,30patients had tumors less than2cm.4. According to Estrogen receptor status of tumor tissues,62cases were ER negative,40cases were ER positive.5. According to Progesterone receptor status of tumor tissues,63cases were ER negative,41cases were ER positive.6. According to HER-2status of tumor tissues,61cases were ER negative,20cases were ER positive.7. According to P53status of tumor tissues,78cases were ER negative,26cases were ER positive.8. All patients were Chinese females and were followed until death or the end of the follow-up period. The median follow-up time were90months.9. All the paraffin-embedded specimens were obtained and were histopathologically diagnosed by at least two pathologists independently.10. The procedures of this study were approved by ethics committees of Qilu hospital, Shandong University.11. To detect the expression of Mstl in breast cancer with immunohistochemistry staining. Immunohistochemical staining was performed by a labeled streptavidin-biotin method according to the manufacturer’s protocol (DAKO corporation, Carpinteria, CA, USA). In brief, paraffin embedded specimens were baked at60℃for60mins. The sections were deparaffinized with xylenes and rehydrated. Sections were submerged into EDTA antigenic retrieval buffer and microwaved for antigenic retrieval. The sections were treated with3%hydrogen peroxide followed by incubation with normal serum to block nonspecific binding. The primary antibody was incubated with the sections for2h at37℃. Next, the tissue sections were incubated with the secondary antibody. Finally, the staining was visualized with diaminobenzidine.12. The evaluation of specimens was obtained and scored by two independent investigators. The scores were determined by combining the percentage of positively stained tumor cells and the intensity of staining. The results were considered to be positive, when the percentage of mild staining cells was over10%of total tumor cells.13. Statistical analysis The statistical analyses were performed using SPSS18.0(Chicago, IL, USA). The association between Mstl expression and clinicopathological-variables of breast cancer was evaluated by chi-square test. Survival analysis was performed using Kaplan-Meier method (the logrank test was used to compare the curves). In univariate and multivariate analysis, the Cox proportional hazards model was applied to determine whether a factor had a significant prognostic role in the overall survival. All P values were two tailed, and the0.05level was considered statistically significant.Results1. The expression of Mstl in breast cancer with immunostainingresultsMstl staining was found mainly on the cytoplasm of breast cancer tissue. Both negative staining and positive staining could be detected in these breast cancer tissues. Among the110breast cancer patients,30(27.3%) were Mstl negative, and the remaining80(72.7%) were Mstl positive.2. Correlation of Mstl expression with clinicopathologic featuresAfter stratifying these110breast cancer patients on the basis of Mstl expression, we observed that the differences in age, tumor size, nodal status, ER, PR, HER-2, and P53status in the two groups had no correlation with Mstl expression.3. Mstl expression and survivalUntill the end of follow-up, there were9cases with Mstl positive died,10with Mstl negative died. Local recurrence occurred in10cases with Mstl positive,5cases with Mstl negative.15patients with Mstl positive had distant metastasis,5patients with Mstl negative had distant metastasis. Kaplan-Meier method was used to evaluate the clinical prognostic value of Mstl in breast cancer. Patients with negative expression of Mstl had poor overall survival, comparing with those with positive expression using Kaplan-Meier method (P=0.009).However, Mstl expression failed to be a predictive marker for the breast relapse-free survival and the distant metastasis-free survival (P=0.112and P=0.762, respectively). Univariate Cox analysis indicated that Mstl expression had significant difference in survival for breast cancer (P=0.027). Moreover, multivariate Cox analysis showed that Mstl expression retained significance as an independent prognostic factor in breast cancer (P=0.030).ConclusionsIn this research, the Mstl expression of110breast cancer patients with a median followed-up of90months were analyzed. We found that Mstl expression was significantly associated with overall survival. Multivariate analysis also indicated that Mstl expression was an independent prognostic factor for breast cancer.However, we did not find prognostic significance for ER/PR status and other clinicopathologic features in univariate or multivariate survival analysis, which may be caused by the limitation by classification of patients and also maybe due to the difference in therapy methods.Taken together, we found that Mstl expression has prognostic significance in breast cancer patients after our long term follow-up study and may present potential opportunities in breast cancer therapy. |
PDF Full Text Request