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Activated Src increases adhesion, survival and alpha2-integrin expression in human breast cancer cells.

ABSTRACT: Focal adhesion kinase (FAK) is an intracellular kinase that localizes to focal adhesions. FAK is overexpressed in human tumours, and FAK regulates both cellular adhesion and anti-apoptotic survival signalling. Disruption of FAK function by overexpression of the FAK C-terminal domain [FAK-CD, analogous to the FRNK (FAK-related non-kinase) protein] leads to loss of adhesion and apoptosis in tumour cells. We have shown that overexpression of an activated form of the Src tyrosine kinase suppressed the loss of adhesion induced by dominant-negative; adenoviral FAK-CD and decreased the apoptotic response in BT474 and MCF-7 breast cancer cell lines. This adhesion-dependent apoptosis was increased by the Src-family kinase inhibitor PP2 [4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine]. We have also shown that expression of activated Src in breast cancer cells increased the expression of alpha2-integrin and that overexpression of alpha2-integrin suppressed FAK-CD-mediated loss of adhesion. Our results suggest a model in which Src regulates adhesion and survival through enhanced expression of the alpha2-integrin. This provides a mechanism through which Src promotes cellular adhesion and alters the adhesive function of FAK.

SUBMITTER: Park HB

PROVIDER: S-EPMC1223979 | biostudies-other | 2004 Mar

REPOSITORIES: biostudies-other

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Project description:Previous reports demonstrate that the Î±2-integrin (Î±2) mediates pancreatic ductal adenocarcinoma (PDAC) cell interaction with collagens. We found that untransformed pancreatic ductal epithelial cells and well-differentiated PDAC cells use Î±2 exclusively to adhere and migrate on collagenI. In contrast, poorly-differentiated PT45P1 and MIAPaCa2 cells demonstrate reduced reliance on, or complete loss of Î±2, respectively. Further, well-differentiated PDAC lines exhibit reduced in vitro invasion compared to poorly-differentiated lines, and Î±2-blockade suppressed invasion of well-differentiated lines exclusively. Based on these data and the demonstrated role of Î±2 in maintaining tissue architecture in other organs, we hypothesized that Î±2 may actually suppress the malignant phenotype in PDAC. Accordingly, stable ectopic expression of Î±2 in MIAPaCa2 cells (MP2-Î±2) retarded in vitro invasion. MP2-Î±2 cells maintained on collagenI were more invasion-retarded than MP2-Î±2 cells maintained in standard tissue culture, and demonstrated higher Î±2Î²1 expression that was reflected in faster and more complete adhesion/migration on collagenI. Affymetrix gene expression profiling of Î±2-expressing and mock-transfected cells revealed that kallikrein-related peptidases (KLK)-5, 6 and 7 were specifically upregulated by Î±2. Accordingly, well-differentiated PDAC lines express KLK-5, 6 and 7 and KLK blockade increased invasion as well as collagenI-migration in KLK-positive lines. Importantly, an Î±2 cytoplasmic deletion mutant promoted KLK expression and retarded invasion, while an Î±9Î±2 chimera retarded invasion less efficiently, and did not impact KLK expression. These data demonstrate for the first time that the Î±2-ectodomain and KLKâ??s coordinately regulate a less invasive phenotype in PDAC cells. Experiment Overall Design: Affymetrix global gene arrays were used to analyse differences in gene expression patterns in MIAPaCa2 cells stably reexpressing the alpha2 integrin, a cytoplasmic deletion of the alpha2 integrin (dCYTO) or an alpha9 ectodomain and transmembrane domain/alpha2 cytoplasmic domain chimera, versus vector-only mock controls. RNA was harvested from cells passaged identically and maitained under standard tissue culture conditions or on collagenI- or tenascin FNIII-coated plates.. Experiment Overall Design: Genetic manipulation (stable transgene expression)

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Activated Src increases adhesion, survival and alpha2-integrin expression in human breast cancer cells.

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