Docking Protein p130Cas Regulates Acinar to Ductal Metaplasia During Pancreatic Adenocarcinoma Development and Pancreatitis.

BACKGROUND & AIMS: Acinar to ductal metaplasia is the prerequisite for the initiation of Kras-driven pancreatic ductal adenocarcinoma (PDAC), and candidate genes regulating this process are emerging from genome-wide association studies. The adaptor protein p130Cas emerged as a potential PDAC susceptibility gene and a Kras-synthetic lethal interactor in pancreatic cell lines; however, its role in PDAC development has remained largely unknown. METHODS: Human PDAC samples and murine KrasG12D-dependent pancreatic cancer models of increasing aggressiveness were used. p130Cas was conditionally ablated in pancreatic cancer models to investigate its role during Kras-induced tumorigenesis. RESULTS: We found that high expression of p130Cas is frequently detected in PDAC and correlates with higher histologic grade and poor prognosis. In a model of Kras-driven PDAC, loss of p130Cas inhibits tumor development and potently extends median survival. Deletion of p130Cas suppresses acinar-derived tumorigenesis and progression by means of repressing PI3K-AKT signaling, even in the presence of a worsening condition like pancreatitis. CONCLUSIONS: Our observations finally demonstrated that p130Cas acts downstream of Kras to boost the PI3K activity required for acinar to ductal metaplasia and subsequent tumor initiation. This demonstrates an unexpected driving role of p130Cas downstream of Kras through PI3K/AKT, thus indicating a rational therapeutic strategy of targeting the PI3K pathway in tumors with high expression of p130Cas.

Conditional ablation of p130Cas/BCAR1 adaptor protein impairs epidermal homeostasis by altering cell adhesion and differentiation.

BACKGROUND: p130 Crk-associated substrate (p130CAS; also known as BCAR1) is a scaffold protein that modulates many essential cellular processes such as cell adhesion, proliferation, survival, cell migration, and intracellular signaling. p130Cas has been shown to be highly expressed in a variety of human cancers of epithelial origin. However, few data are available regarding the role of p130Cas during normal epithelial development and homeostasis. METHODS: To this end, we have generated a genetically modified mouse in which p130Cas protein was specifically ablated in the epidermal tissue. RESULTS: By using this murine model, we show that p130Cas loss results in increased cell proliferation and reduction of cell adhesion to extracellular matrix. In addition, epidermal deletion of p130Cas protein leads to premature expression of "late" epidermal differentiation markers, altered membrane E-cadherin/catenin proteins localization and aberrant tyrosine phosphorylation of E-cadherin/catenin complexes. Interestingly, these alterations in adhesive properties in absence of p130Cas correlate with abnormalities in progenitor cells balance resulting in the amplification of a more committed cell population. CONCLUSION: Altogether, these results provide evidence that p130Cas is an important regulator of epidermal cell fate and homeostasis.

Dysregulation of Blimp1 transcriptional repressor unleashes p130Cas/ErbB2 breast cancer invasion.

ErbB2 overexpression is detected in approximately 20% of breast cancers and is correlated with poor survival. It was previously shown that the adaptor protein p130Cas/BCAR1 is a crucial mediator of ErbB2 transformation and that its overexpression confers invasive properties to ErbB2-positive human mammary epithelial cells. We herein prove, for the first time, that the transcriptional repressor Blimp1 is a novel mediator of p130Cas/ErbB2-mediated invasiveness. Indeed, high Blimp1 expression levels are detected in invasive p130Cas/ErbB2 cells and correlate with metastatic status in human breast cancer patients. The present study, by using 2D and 3D breast cancer models, shows that the increased Blimp1 expression depends on both MAPK activation and miR-23b downmodulation. Moreover, we demonstrate that Blimp1 triggers cell invasion and metastasis formation via its effects on focal adhesion and survival signaling. These findings unravel the previously unidentified role that transcriptional repressor Blimp1 plays in the control of breast cancer invasiveness.

p130Cas/BCAR1 scaffold protein in tissue homeostasis and pathogenesis.

BCAR1 (also known as p130Cas/BCAR1) is an adaptor protein that belongs to the CAS family of scaffold proteins. In the past years, increasing evidence has demonstrated the ability of p130Cas/BCAR1 to activate signaling originating from mechanical stimuli, cell-extracellular matrix (ECM) adhesion and growth factor stimulation cascades during normal development and disease in various biological models. In this review we will specifically discuss the more recent data on the contribution of p130Cas/BCAR1 in the regulation of tissue homeostasis and its potential implications in pathological conditions.

p130Cas alters the differentiation potential of mammary luminal progenitors by deregulating c-Kit activity.

It has recently been proposed that defective differentiation of mammary luminal progenitors predisposes to basal-like breast cancer. However, the molecular and cellular mechanisms involved are still unclear. Here, we describe that the adaptor protein p130Cas is a crucial regulator of mouse mammary epithelial cell (MMEC) differentiation. Using a transgenic mouse model, we show that forced p130Cas overexpression in the luminal progenitor cell compartment results in the expansion of luminal cells, which aberrantly display basal cell features and reduced differentiation in response to lactogenic stimuli. Interestingly, MMECs overexpressing p130Cas exhibit hyperactivation of the tyrosine kinase receptor c-Kit. In addition, we demonstrate that the constitutive c-Kit activation alone mimics p130Cas overexpression, whereas c-Kit downregulation is sufficient to re-establish proper differentiation of p130Cas overexpressing cells. Overall, our data indicate that high levels of p130Cas, via abnormal c-Kit activation, promote mammary luminal cell plasticity, thus providing the conditions for the development of basal-like breast cancer. Consistently, p130Cas is overexpressed in human triple-negative breast cancer, further suggesting that p130Cas upregulation may be a priming event for the onset of basal-like breast cancer.

p130Cas over-expression impairs mammary branching morphogenesis in response to estrogen and EGF.

p130Cas adaptor protein regulates basic processes such as cell cycle control, survival and migration. p130Cas over-expression has been related to mammary gland transformation, however the in vivo consequences of p130Cas over-expression during mammary gland morphogenesis are not known. In ex vivo mammary explants from MMTV-p130Cas transgenic mice, we show that p130Cas impairs the functional interplay between Epidermal Growth Factor Receptor (EGFR) and Estrogen Receptor (ER) during mammary gland development. Indeed, we demonstrate that p130Cas over-expression upon the concomitant stimulation with EGF and estrogen (E2) severely impairs mammary morphogenesis giving rise to enlarged multicellular spherical structures with altered architecture and absence of the central lumen. These filled acinar structures are characterized by increased cell survival and proliferation and by a strong activation of Erk1/2 MAPKs and Akt. Interestingly, antagonizing the ER activity is sufficient to re-establish branching morphogenesis and normal Erk1/2 MAPK activity. Overall, these results indicate that high levels of p130Cas expression profoundly affect mammary morphogenesis by altering epithelial architecture, survival and unbalancing Erk1/2 MAPKs activation in response to growth factors and hormones. These results suggest that alteration of morphogenetic pathways due to p130Cas over-expression might prime mammary epithelium to tumorigenesis.

p130Cas promotes invasiveness of three-dimensional ErbB2-transformed mammary acinar structures by enhanced activation of mTOR/p70S6K and Rac1.

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.