Brain metastases are the most common cause of death in patients with metastatic melanoma, and the RAF-MEK-ERK and PI3K-AKT signaling pathways are key players in melanoma progression and drug resistance. The BRAF inhibitor vemurafenib significantly improved overall survival. However, brain metastases still limit the effectiveness of this therapy. In a series of patients, we observed that treatment with vemurafenib resulted in substantial regression of extracerebral metastases, but brain metastases developed. This study aimed to identify factors that contribute to treatment resistance in brain metastases. Matched brain and extracerebral metastases from melanoma patients had identical ERK, p-ERK, and AKT immunohistochemistry staining patterns, but there was hyperactivation of AKT (p-AKT) and loss of PTEN expression in the brain metastases. Mutation analysis revealed no differences in BRAF, NRAS, or KIT mutation status in matched brain and extracerebral metastases. In contrast, AKT, p-AKT, and PTEN expression was identical in monolayer cultures derived from melanoma brain and extracerebral metastases. Furthermore, melanoma cells stimulated by astrocyte-conditioned medium showed higher AKT activation and invasiveness than melanoma cells stimulated by fibroblast-conditioned medium. Inhibition of PI3K-AKT signaling resensitized melanoma cells isolated from a vemurafenib-resistant brain metastasis to vemurafenib. Brain-derived factors appear to induce hyperactivation of the AKT survival pathway and to promote the survival and drug resistance of melanoma cells in the brain. Thus, inhibition of PI3K-AKT signaling shows potential for enhancing and/or prolonging the antitumor effect of BRAF inhibitors or other anticancer agents in melanoma brain metastases.
SEC that exhibit morphological and immunophenotypical features of the SEC seen in certain other liver diseases are found in cirrhosis. These findings further support the hypothesis that a bipotent hepatic stem cell that may give rise to biliary epithelial cells and hepatocytes exists in the human liver.
To examine the impact of photodynamic therapy (PDT) on angiogenesis in human choroidal neovascular membranes with respect to vascular endothelial growth factor (VEGF) expression, proliferation, and vascularization. Methods: Retrospective review of an interventional case series of 50 patients (50 eyes) who underwent removal of choroidal neovascular membranes. Choroidal neovascularization was secondary to age-related macular degeneration. Twenty patients were treated with PDT 3 to 655 days before surgery. Choroidal neovascular membranes were stained for CD34, CD105, Ki-67, cytokeratin 18, and VEGF. Thirty choroidal neovascular membranes secondary to age-related macular degeneration without previous treatment were used as controls. Results: Specimens without pretreatment disclosed varying degrees of vascularization, proliferative activity, and
The transcription factor SOX2 has been extensively studied for its role in embryonic stem cell self-renewal and pluripotency. More recent data suggest oncogenic functions of SOX2 and demonstrate expression in several carcinoma types, predominantly of squamous cell origin. The gene SOX2 is located at chromosome 3q26, a region that is frequently amplified in ovarian high-grade serous carcinoma. In this study, we correlate SOX2 protein expression and gene-amplification status in ovarian carcinomas with histopathologic criteria and disease outcome. A total of 215 cases of ovarian carcinomas (154 serous, 39 endometrioid, 11 clear cell, 5 mucinous, and 6 transitional cell carcinomas) were analyzed by immunohistochemistry in a tissue microarray for nuclear expression of SOX2. A total of 60.5% of all carcinomas showed SOX2 expression with no significant difference between the major histologic types. Interestingly, SOX2 expression was predominantly a feature of high-grade tumors (G1: 36.4%, G2: 55.6%, G3: 64.0%, P=0.040). In 21.2% of these cases, fluorescence in situ hybridization analysis detected low-level SOX2 gene amplification which was not significantly associated with SOX2 protein expression. However, survival analysis of Stage II to IV high-grade serous carcinomas revealed a favorable effect of SOX2 expression (median disease-free survival 27 vs. 21 mo, P=0.041; median overall survival 39 vs. 25 mo, P=0.062). Further studies are needed to explore whether expression of SOX2 has a specific role in prognosis and therapy response.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.