BCAR3

Abstract: Purpose We have previously identified a set of breast cancer antiestrogen resistance (BCAR) genes causing estrogen independence and tamoxifen resistance in vitro using a functional genetic screen. Here, we explored whether these BCAR genes provide predictive value for tamoxifen resistance and prognostic information for tumor aggressiveness in breast cancer patients. Patients and Methods mRNA levels of 10 BCAR genes (AKT1, AKT2, BCAR1, BCAR3, EGFR, ERBB2, GRB7, SRC, TLE3, and TRERF1) were measured in estrogen receptor–positive breast tumors using quantitative reverse-transcriptase polymerase chain reaction. Normalized mRNA levels were evaluated for association with progression-free survival (PFS) in 242 patients receiving tamoxifen as first-line monotherapy for recurrent disease, and with distant metastasis-free survival (MFS) in 413 lymph node-negative (LNN) primary breast cancer patients who did not receive systemic adjuvant therapy. Results Concerning tamoxifen resistance, BCAR3, ERBB2, GRB7, and TLE3 m...

Abstract: We have characterized a novel cDNA whose steady state mRNA levels rise in the thymus 2 to 6 h following the induction of CD4+CD8+ thymocyte apoptosis by in vivo cross-linking of CD3 epsilon. This cDNA, AND-34-1, contains an open reading frame (ORF) encoding a protein with an amino-terminal Src homology 2 (SH2) domain and a carboxyl-terminal domain homologous to GDP-exchange factors (GEFs). Northern analysis demonstrates widespread expression of the AND-34 gene. Anti-CD3 epsilon treatment induces up-regulation of the AND-34 mRNA levels in total thymic RNA but not in RNA from purified thymocytes, suggesting that this transcript is derived from a thymic stromal cell population. IL-1 and TNF increase AND-34 transcript levels in thymic cortical reticular, thymic nurse, and fibroblast cell lines. In the thymic cortical reticular cell line, IL-1 and TNF induce a protein of the predicted 93-kDa size reactive with anti-AND-34 peptide antisera. Fifteen minutes of serum stimulation of vanadate-pretreated AND-34-1-transfected NIH3T3 fibroblasts induces tyrosine phosphorylation of AND-34 as well as coprecipitating 95-, 125-, and 130-kDa proteins. One of these tyrosine phosphorylated proteins is identified as p130Cas (Crk-associated substrate), a signaling molecule previously known to bind to a GDP-exchange factor (C3G) and inducibly associate with the focal adhesion complex. Consistent with such an association, AND-34 tyrosine phosphorylation is induced following adherence of trypsinized fibroblasts to fibronectin or poly-L -lysine-coated surfaces.

Abstract: Therapeutic interventions based on metabolic inhibitor-based therapies are expected to be less prone to acquired resistance. However, there has not been any study assessing the possibility that the targeting of the tumor cell metabolism may result in unforeseeable resistance. We recently established a pre-clinical model of estrogen-dependent MCF-7 breast cancer cells that were chronically adapted to grow (> 10 months) in the presence of graded, millimolar concentrations of the anti-diabetic biguanide metformin, an AMPK agonist/mTOR inhibitor that has been evaluated in multiple in vitro and in vivo cancer studies and is now being tested in clinical trials. To assess what impact the phenomenon of resistance might have on the metformin-like “dirty” drugs that are able to simultaneously hit several metabolic pathways, we employed the ingenuity pathway analysis (IPA) software to functionally interpret the data from Agilent whole-human genome arrays in the context of biological processes, networks, and pathways. Our findings establish, for the first time, that a “global” targeting of metabolic reprogramming using metformin certainly imposes a great selective pressure for the emergence of new breast cancer cellular states. Intriguingly, acquired resistance to metformin appears to trigger a transcriptome reprogramming toward a metastatic stem-like profile, as many genes encoding the components of the degradome (KLK11, CTSF, FREM1, BACE-2, CASP, TMPRSS4, MMP16, HTRA1), cancer cell migration and invasion factors (TP63, WISP2, GAS3, DKK1, BCAR3, PABPC1, MUC1, SPARCL1, SEMA3B, SEMA6A), stem cell markers (DCLK1, FAK), and key pro-metastatic lipases (MAGL and Cpla2) were included in the signature. Because this convergent activation of pathways underlying tumor microenvironment interactions occurred in low-proliferative cancer cells exhibiting a notable downregulation of the G2/M DNA damage checkpoint regulators that maintain genome stability (CCNB1, CCNB2, CDC20, CDC25C, AURKA, AURKB, BUB1, CENP-A, CENP-M) and pro-autophagic features (i.e., TRAIL upregulation and BCL-2 downregulation), it appears that the unique mechanism of acquired resistance to metformin has opposing roles in growth and metastatic dissemination. While refractoriness to metformin limits breast cancer cell growth, likely due to aberrant mitotic/cytokinetic machinery and accelerated autophagy, it notably increases the potential of metastatic dissemination by amplifying the number of pro-migratory and stemness inputs via the activation of a significant number of proteases and EMT regulators. Future studies should elucidate whether our findings using supra-physiological concentrations of metformin mechanistically mimic the ultimate processes that could paradoxically occur in a polyploid, senescent-autophagic scenario triggered by the chronic metabolic stresses that occur during cancer development and after treatment with cancer drugs.