9564

BCAR1

breast cancer anti-estrogen resistance 1;BCAR1;breast cancer anti-estrogen resistance 1

Cas scaffolding protein family member 1|Crk-associated substrate p130Cas|breast cancer anti-estrogen resistance protein 1

16q23.1

protein-coding

During breast cancer progression, transforming growth factor-beta (TGF-beta) switches from a tumor suppressor to a pro-metastatic molecule. Several recent studies suggest that this conversion in TGF-beta function depends upon fundamental changes in the TGF-beta signaling system. We show here that these changes in TGF-beta signaling are concomitant with aberrant expression of the focal adhesion protein, p130Cas. Indeed, elevating expression of either the full-length (FL) or just the carboxyl terminus (CT) of p130Cas in mammary epithelial cells (MECs) diminished the ability of TGF-beta1 to activate Smad2/3, but increased its coupling to p38 MAPK. This shift in TGF-beta signaling evoked (i) resistance to TGF-beta-induced growth arrest, and (ii) acinar filling upon three-dimensional organotypic cultures of p130Cas-FL or -CT expressing MECs. Furthermore, rendering metastatic MECs deficient in p130Cas enhanced TGF-beta-stimulated Smad2/3 activity, which restored TGF-beta-induced growth inhibition both in vitro and in mammary tumors produced in mice. Additionally, whereas elevating TbetaR-II expression in metastatic MECs had no affect on their phosphorylation of Smad2/3, this event markedly enhanced their activation of p38 MAPK, leading to increased MEC invasion and metastasis. Importantly, depleting p130Cas expression in TbetaR-II-expressing metastatic MECs significantly increased their activation of Smad2/3, which (i) reestablished the physiologic balance between canonical and noncanonical TGF-beta signaling, and (ii) reversed cellular invasion and early mammary tumor cell dissemination stimulated by TGF-beta. Collectively, our findings identify p130Cas as a molecular rheostat that regulates the delicate balance between canonical and noncanonical TGF-beta signaling, a balance that is critical to maintaining the tumor suppressor function of TGF-beta during breast cancer progression.

ErbB2 over-expression is detected in approximately 25% of invasive breast cancers and is strongly associated with poor patient survival. We have previously demonstrated that p130Cas adaptor is a crucial mediator of ErbB2 transformation. Here, we analysed the molecular mechanisms through which p130Cas controls ErbB2-dependent invasion in three-dimensional cultures of mammary epithelial cells. Concomitant p130Cas over-expression and ErbB2 activation enhance PI3K/Akt and Erk1/2 MAPK signalling pathways and promote invasion of mammary acini. By using pharmacological inhibitors, we demonstrate that both signalling cascades are required for the invasive behaviour of p130Cas over-expressing and ErbB2 activated acini. Erk1/2 MAPK and PI3K/Akt signalling triggers invasion through distinct downstream effectors involving mTOR/p70S6K and Rac1 activation, respectively. Moreover, in silico analyses indicate that p130Cas expression in ErbB2 positive human breast cancers significantly correlates with higher risk to develop distant metastasis, thus underlying the value of the p130Cas/ErbB2 synergism in regulating breast cancer invasion. In conclusion, high levels of p130Cas favour progression of ErbB2-transformed cells towards an invasive phenotype.

BACKGROUND: p130Cas (p130Crk-associated substance) is a junction protein that is important to the adhesion between cytoskeleton and extracellular matrix. Also, the adhesion molecules E-cadherin and beta-catenin play important roles in the invasiveness of carcinoma. This study was undertaken to investigate the effects of p130Cas, E-cadherin and beta-catenin on the invasion, metastasis and prognosis of hepatocellular carcinoma (HCC). METHODS: Immunohistochemistry was used to evaluate the expression of p130Cas, E-cadherin, and beta-catenin in 40 patients with HCC. All patients were followed up postoperatively, and the relationship between expression and clinicopathological prognostic parameters was analyzed. RESULTS: The positive expression rates of p130Cas and E-cadherin in HCC tissue (n=40) were 62.50% and 55.00%, but in normal liver tissue 10%, and 100%, respectively (P<0.05). The abnormal expression rate of beta-catenin in HCC tissue was 70%, while in normal liver tissue it was 13.33% (P<0.05). The positive rate of p130Cas was correlated with lymph node invasion, pathological stage, TNM stage, and a worse prognosis, but not with gender, age, HBV infection, hepatic cirrhosis, alpha-fetoprotein (AFP) level before operation, and tumor diameter. Similarly, the expression of E-cadherin and beta-catenin was correlated with lymph node invasion, pathological stage, TNM stage, and worse prognosis, but not with gender, age, HBV infection, hepatic cirrhosis, AFP level before operation, and tumor size. Correlations were found between p130Cas and abnormal E-cadherin/beta-catenin expression (P<0.001 and <0.05, respectively). CONCLUSIONS: In HCC, there is a negative correlation between the positive expression of p130Cas and the normal expression of the adhesion molecules E-cadherin/beta-catenin, and p130Cas plays important roles in the invasion, metastasis and prognosis of HCC. p130Cas may be involved in alterating the structure and function of E-cadherin/beta-catenin, by regulating tyrosine phosphorylation via the p130Cas-Src signal pathway.

The regulation and function of the signaling adaptor protein p130(Cas) in tumor cell anchorage-independent survival, or anoikis resistance, were investigated in human lung adenocarcinoma cells. The tyrosine phosphorylation and function of p130(Cas) during cell detachment were analyzed in tumor cells and compared with that of normal epithelial cells. Cell detachment trigged rapid dephosphorylation of p130(Cas) in the nontumorigenic and anoikis-sensitive normal epithelial cells, but had no effect on the tyrosine phosphorylation of p130(Cas) in the anoikis-resistant lung adenocarcinoma cells. Further analysis revealed that the total tyrosine kinase activities associated with p130(Cas) in the lung tumor cells are anchorage-independent and are significantly higher than that in the normal cells, in which the p130(Cas)-associated tyrosine kinase activities are anchorage-dependent. Analysis of two known p130(Cas)-associated tyrosine kinases FAK and Src indicated that the regulation of tyrosine phosphorylation of FAK and Src are altered in the tumor cells. Inhibition of Src specifically abolished phosphorylation of p130(Cas) and induced anoikis. Furthermore, overexpression of dominant-negative forms of p130(Cas) also induced apoptosis. Taken together, these data suggest that p130(Cas) mediates a cell survival signal from cell-matrix interaction. Alterations in tumor cells that lead to constitutive phosphorylation of p130(Cas) can prevent cells from anoikis, hence contribute to tumor cell anchorage independence and metastasis.

During breast cancer progression, transforming growth factor-beta (TGF-beta) switches from a tumor suppressor to a pro-metastatic molecule. Several recent studies suggest that this conversion in TGF-beta function depends upon fundamental changes in the TGF-beta signaling system. We show here that these changes in TGF-beta signaling are concomitant with aberrant expression of the focal adhesion protein, p130Cas. Indeed, elevating expression of either the full-length (FL) or just the carboxyl terminus (CT) of p130Cas in mammary epithelial cells (MECs) diminished the ability of TGF-beta1 to activate Smad2/3, but increased its coupling to p38 MAPK. This shift in TGF-beta signaling evoked (i) resistance to TGF-beta-induced growth arrest, and (ii) acinar filling upon three-dimensional organotypic cultures of p130Cas-FL or -CT expressing MECs. Furthermore, rendering metastatic MECs deficient in p130Cas enhanced TGF-beta-stimulated Smad2/3 activity, which restored TGF-beta-induced growth inhibition both in vitro and in mammary tumors produced in mice. Additionally, whereas elevating TbetaR-II expression in metastatic MECs had no affect on their phosphorylation of Smad2/3, this event markedly enhanced their activation of p38 MAPK, leading to increased MEC invasion and metastasis. Importantly, depleting p130Cas expression in TbetaR-II-expressing metastatic MECs significantly increased their activation of Smad2/3, which (i) reestablished the physiologic balance between canonical and noncanonical TGF-beta signaling, and (ii) reversed cellular invasion and early mammary tumor cell dissemination stimulated by TGF-beta. Collectively, our findings identify p130Cas as a molecular rheostat that regulates the delicate balance between canonical and noncanonical TGF-beta signaling, a balance that is critical to maintaining the tumor suppressor function of TGF-beta during breast cancer progression.

Reactive oxygen species (ROS) have emerged as cellular signaling molecules and are implicated in metastatic disease by their ability to drive invasion and migration. Here, we define the signaling adaptor protein p130Cas (Crk-associated substrate) as a key redox-responsive molecular trigger that is engaged in highly invasive metastatic bladder tumor cell lines. Endogenous shifts in steady-state hydrogen peroxide (H2O2) that accompany the metastatic phenotype increase p130Cas phosphorylation, membrane recruitment and association with the scaffolding protein Crk, and subsequent Rac1 activation and actin reorganization. Both enzymatic and nonenzymatic scavenging of H2O2 abrogates p130Cas-dependent signaling and the migratory and invasive activity of the metastatic bladder tumor cells. Disruption of p130Cas attenuates both invasion and migration of the metastatic variant (253J-BV). 253J-BV cells displayed an increase in global thiol oxidation and a concomitant decrease in total phosphatase activity, common target proteins of active-site cysteine oxidation. The dependence of phosphatases on regulation of p130Cas was highlighted when depletion of PTPN12 enhanced p130cas phosphorylation and the migratory behavior of a noninvasive parental bladder tumor control (253J). These data show that the metastatic phenotype is accompanied by increases in steady-state H2O2 production that drive promigratory signaling and suggest that antioxidant-based therapeutics may prove useful in limiting bladder tumor invasiveness.