Elevated Expression of MAPK Phosphatase 3 in Breast Tumors—A Mechanism of Tamoxifen Resistance

Antiestrogen resistance is a major clinical problem in the treatment of breast cancer. Altered growth factor signaling with estrogen receptor (ER) α has been shown to be associated with the development of resistance. Gene expression profiling was utilized to identify MAPK phosphatase 3 (MKP3) whose expression was correlated with response to the antiestrogen tamoxifen in both patients and in vitro derived cell line models. Overexpression of MKP3 rendered ERα-positive breast cancer cells resistant to the growth inhibitory effects of tamoxifen, and enhanced tamoxifen agonist activity in endometrial cells. MKP3 overexpression was associated with lower levels of activated ERK1,2 phosphorylation in the presence of estrogen, but that estrogen deprivation and tamoxifen treatment decreased MKP3 phosphatase activity, leading to an up-regulation of pERK1,2 MAPK, phosphoserine 118 of ERα, and cyclin D1. The MEK inhibitor PD98059 blocked tamoxifen-resistant growth. Accumulation of reactive oxygen species was observed with tamoxifen treatment of MKP3 overexpressing cells, and antioxidant treatment increased MKP3 phosphatase activity, thereby blocking resistance. Furthermore, PD98059 increased the levels of phospho-JNK in tamoxifen-treated MKP3 overexpressing cells, suggesting an interaction between MKP3 levels, activation of ERK1,2 MAPK, and JNK signaling in human breast cancer cells. MKP3 represents a novel mechanism of resistance which may be a potential biomarker for the use of ERK1,2 and/or JNK inhibitors in combination with tamoxifen treatment

Prevention of Hypovolemic Circulatory Collapse by IL-6 Activated Stat3

Half of trauma deaths are attributable to hypovolemic circulatory collapse (HCC). We established a model of HCC in rats involving minor trauma plus severe hemorrhagic shock (HS). HCC in this model was accompanied by a 50% reduction in peak acceleration of aortic blood flow and cardiomyocyte apoptosis. HCC and apoptosis increased with increasing duration of hypotension. Apoptosis required resuscitation, which provided an opportunity to intervene therapeutically. Administration of IL-6 completely reversed HCC, prevented cardiac dysfunction and cardiomyocyte apoptosis, reduced mortality 5-fold and activated intracardiac signal transducer and activator of transcription (STAT) 3. Pre-treatment of rats with a selective inhibitor of Stat3, T40214, reduced the IL-6-mediated increase in cardiac Stat3 activity, blocked successful resuscitation by IL-6 and reversed IL-6-mediated protection from cardiac apoptosis. The hearts of mice deficient in the naturally occurring dominant negative isoform of Stat3, Stat3β, were completely resistant to HS-induced apoptosis. Microarray analysis of hearts focusing on apoptosis related genes revealed that expression of 29% of apoptosis related genes was altered in HS vs. sham rats. IL-6 treatment normalized the expression of these genes, while T40214 pretreatment prevented IL-6-mediated normalization. Thus, cardiac dysfunction, cardiomyocyte apoptosis and induction of apoptosis pathway genes are important components of HCC; IL-6 administration prevented HCC by blocking cardiomyocyte apoptosis and induction of apoptosis pathway genes via Stat3 and warrants further study as a resuscitation adjuvant for prevention of HCC and death in trauma patients

Comprehensive Genomic Analysis Identifies Novel Subtypes and Targets of Triple-Negative Breast Cancer

PURPOSE: Genomic profiling studies suggest triple-negative breast cancer (TNBC) is a heterogeneous disease. In this study we sought to define TNBC subtypes and identify subtype-specific markers and targets. PATIENTS AND METHODS: RNA and DNA profiling analyses were conducted on 198 TNBC tumors (ER-negativity defined as Allred Scale value ≤2) with >50% cellularity (discovery set: n=84; validation set: n=114) collected at Baylor College of Medicine. An external data set of 7 publically-accessible TNBC studies was used to confirm results. DNA copy number, disease-free survival (DFS) and disease-specific survival (DSS) were analyzed independently using these datasets. RESULTS: We identified and confirmed four distinct TNBC subtypes: (1) Luminal-AR (LAR); 2) Mesenchymal (MES); 3) Basal-Like Immune-Suppressed (BLIS), and 4) Basal-Like Immune-Activated (BLIA). Of these, prognosis is worst for BLIS tumors and best for BLIA tumors for both DFS (logrank test p=0.042 and 0.041, respectively) and DSS (logrank test p=0.039 and 0.029, respectively). DNA copy number analysis produced two major groups (LAR and MES/BLIS/BLIA), and suggested gene amplification drives gene expression in some cases (FGFR2 (BLIS)). Putative subtype-specific targets were identified: 1) LAR: androgen receptor and the cell surface mucin MUC1; 2) MES: growth factor receptors (PDGF receptor A; c-Kit); 3) BLIS: an immune suppressing molecule (VTCN1); and 4) BLIA: Stat signal transduction molecules and cytokines. CONCLUSION: There are four stable TNBC subtypes characterized by the expression of distinct molecular profiles that have distinct prognoses. These studies identify novel subtype-specific targets that can be targeted in the future for effective treatment of TNBCs