ABSTRACT
Integrin expression and activity are altered in tumors, and aberrant integrin signaling promotes malignancy. However, how integrins become altered in tumors remains poorly understood. We discovered that oncogenic activation of MEK signaling induces cell growth and survival, and promotes the malignant phenotype of mammary epithelial cells (MECs) by increasing α5 integrin expression. We determined that MEK activates c-Myc to reduce the transcription of the SWI/SNF chromatin remodeling enzyme Brahma (BRM). Our studies revealed that reduced BRM expression and/or activity drives the malignant behavior of MECs by epigenetically promoting C/EBPß expression to directly induce α5 integrin transcription. Consistently, we could show that restoring BRM levels normalized the malignant behavior of transformed MECs in culture and in vivo by preventing C/EBPß-dependent α5 integrin transcription. Our findings identify a novel mechanism whereby oncogenic signaling promotes malignant transformation by regulating transcription of a key chromatin remodeling molecule that regulates integrin-dependent stromal-epithelial interactions.
Subject(s)
Breast Neoplasms/genetics , CCAAT-Enhancer-Binding Protein-beta/genetics , Cell Transformation, Neoplastic/genetics , Gene Expression Regulation, Neoplastic/genetics , Integrin alpha5/biosynthesis , Transcription Factors/genetics , Breast Neoplasms/metabolism , CCAAT-Enhancer-Binding Protein-beta/metabolism , Cell Adhesion , Cell Line, Tumor , Cell Transformation, Neoplastic/metabolism , Chromatin Immunoprecipitation , Epithelial Cells/metabolism , Flow Cytometry , Fluorescent Antibody Technique , Humans , Immunoblotting , Integrin alpha5/genetics , RNA, Small Interfering , Real-Time Polymerase Chain Reaction , Transcription Factors/metabolism , TransfectionABSTRACT
The Monro-Kellie doctrine states that the interior of the cranium is formed of three main components: blood, fluid and cerebral parenchyma. An increase in the volume of one or more components may increase the intracranial pressure (ICP). This doctrine also affirms that the skull cannot be expanded after the closure of the fontanels. Monro and Kellie's theory has been perfected during the last two centuries. This study leads to a new contribution that proves that even adults' consolidated skulls present volumetric changes as a consequence of ICP variations.
Subject(s)
Cerebrovascular Circulation/physiology , Intracranial Hypotension/physiopathology , Intracranial Pressure , Models, Biological , Humans , In Vitro Techniques , Posture , Transducers, PressureABSTRACT
We have recently shown that the adaptor protein p140Cap regulates tumor properties in terms of cell motility and growth. Here, by using the highly metastatic rat adenocarcinoma cell line MTLn3-epidermal growth factor receptor (EGFR), we assess the role of p140Cap in metastasis formation. Orthotopic transplantation of MTLn3-EGFR cells over-expressing p140Cap in Rag2(-/-)γ(c)(-/-) mice resulted in normal primary tumor growth compared with the controls. Strikingly, p140Cap over-expression causes an 80% inhibition in the number of lung metastases. p140Cap over-expressing cells display a 50% reduction in directional cell migration, an increased number and size of focal adhesions, and a strong impairment in the ability to invade in a 3D matrix. p140Cap over-expression affects EGFR signaling and tyrosine phosphorylation of cortactin in response to EGF stimulation. Intriguingly, p140Cap associates with cortactin via interaction with its second proline-rich domain to the cortactin SH3 domain. The phosphomimetic cortactin tyrosine 421 mutant rescues migration and invasive properties in p140Cap over-expressing cells. Taken together, these data demonstrate that p140Cap suppresses the invasive properties of highly metastatic breast carcinoma cells by inhibiting cortactin-dependent cell motility.
Subject(s)
Adaptor Proteins, Vesicular Transport/metabolism , Cortactin/metabolism , Mammary Neoplasms, Experimental/metabolism , Adaptor Proteins, Vesicular Transport/genetics , Adenocarcinoma/genetics , Adenocarcinoma/metabolism , Adenocarcinoma/pathology , Animals , Cell Line, Tumor , Cell Movement , Cortactin/genetics , Epidermal Growth Factor/pharmacology , ErbB Receptors/genetics , ErbB Receptors/metabolism , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , HEK293 Cells , Humans , Immunohistochemistry , Lung Neoplasms/genetics , Lung Neoplasms/metabolism , Lung Neoplasms/secondary , Mammary Neoplasms, Experimental/genetics , Mammary Neoplasms, Experimental/pathology , Mice , Mice, Knockout , Microscopy, Fluorescence, Multiphoton , Neoplasm Invasiveness , Neoplasm Metastasis , Neoplasm Transplantation , Phosphorylation/drug effects , Protein Binding , RNA Interference , Rats , Transplantation, HeterologousABSTRACT
The adaptor protein p140Cap/SNIP is a novel Src-binding protein that regulates Src activation through C-terminal Src kinase (Csk). Here, by gain and loss of function approaches in breast and colon cancer cells, we report that p140Cap immobilizes E-cadherin at the cell membrane and inhibits EGFR and Erk1/2 signalling, blocking scatter and proliferation of cancer cells. p140Cap-dependent regulation of E-cadherin/EGFR cross-talk and cell motility is due to the inhibition of Src kinase. However, rescue of Src activity is not sufficient to restore Erk1/2 phosphorylation and proliferation. Indeed, p140Cap also impairs Erk1/2 phosphorylation by affecting Ras activity, downstream to the EGFR. In conclusion, p140Cap stabilizes adherens junctions and inhibits EGFR and Ras signalling through the dual control of both Src and Ras activities, thus affecting crucial cancer properties such as invasion and growth. Interestingly, p140Cap expression is lost in more aggressive human breast cancers, showing an inverse correlation with EGFR expression. Therefore, p140Cap mechanistically behaves as a tumour suppressor that inhibits signalling pathways leading to aggressive phenotypes.
