FRNK blocks v-Src-stimulated invasion and experimental metastases without effects on cell motility or growth

Abstract

Focal adhesion kinase (FAK) was first identified as a viral Src (v-Src) substrate, but the role of FAK in Src transformation events remains undefined. We show that stable expression of the FAK C-terminal domain (termed FRNK) in v-Src-transformed NIH 3T3 fibroblasts inhibited cell invasion through Matrigel and blocked experimental metastases in nude mice without effects on cell motility. FRNK inhibitory activity was dependent upon its focal contact localization. FRNK expression disrupted the formation of a v-Src-FAK signaling complex, inhibited p130Cas tyrosine phosphorylation, and attenuated v-Src-stimulated ERK and JNK kinase activation. However, FRNK did not affect v-Src-stimulated Akt activation, cell growth in soft agar, or subcutaneous tumor formation in nude mice. FRNK-expressing cells exhibited decreased matrix metalloproteinase-2 (MMP-2) mRNA levels and MMP-2 secretion. Transient FRNK expression in human 293 cells inhibited exogenous MMP-2 promoter activity and overexpression of wild-type but not catalytically-inactive (Ala-404) MMP-2 rescued v-Src-stimulated Matrigel invasion in the presence of FRNK. Our findings show the importance of FAK in Src-stimulated cell invasion and support a role for Src-FAK signaling associated with elevated tumor cell metastases.

Intrinsic focal adhesion kinase activity controls orthotopic breast carcinoma metastasis via the regulation of urokinase plasminogen activator expression in a syngeneic tumor model

“…In experimental metastasis assays after tail vein injection, FRNK expression in v-Src-transformed fibroblasts (Hauck et al, 2002b), B16-F10 (AbdelGhany et al, 2002) and MTLn3 breast carcinoma cells (van Nimwegen et al, 2005) blocked tumor cell colonization of lungs. In various tumor cells, exogenous FRNK expression is correlated with reduced levels of protease secretion (Hauck et al, 2002b;Hess et al, 2005) or slower growth (van Nimwegen et al, 2005). Although FRNK acts to inhibit FAK activity, it also encompasses multiple protein binding sites and may act to sequester signaling proteins away from FAK.…”

“…Images captured at different wavelengths were merged using OpenLabs acquisition software (Improvision). Lung sections were also processed for standard hematoxylin-eosin staining as described (Hauck et al, 2002b). For subcutaneous tumor growth assays, 10 6 4T1 cells were injected subcutaneously on the backs of shaved BALB/c mice.…”

“…Whereas high levels of FRNK can promote cell apoptosis (Xu et al, 2000;Golubovskaya et al, 2002), FRNK expression can also reduce tumor growth by promoting tumor dormancy and by inhibiting cell proliferation (Aguirre Ghiso, 2002;van Nimwegen et al, 2005). Low levels of FRNK expression have revealed the importance of FAK activity in promoting tumor cell migration (Slack et al, 2001) and in generating an invasive cell phenotype (Hauck et al, 2001(Hauck et al, , 2002bHsia et al, 2003;.…”

Tetraspanin KAI1/CD82 suppresses invasion by inhibiting integrin-dependent crosstalk with c-Met receptor and Src kinases

“…Signaling through Src has been proposed to be involved in regulating cell migration and invasion by integrins (Sieg et al, 2000;Hauck et al, 2002;Hsia et al, 2003;Frame, 2004;Westhoff et al, 2004;Brunton et al, 2005). Two downstream targets of Src, FAK and p130Cas, have been proposed to be required for integrin-mediated migration (Vuori et al, 1996;Klemke et al, 1998;Hauck et al, 2002).…”

“…Furthermore, reexpression of CD82 did not alter signaling to Erk or to Akt ( Figure S3B). Both integrins and c-Met have been shown to be effective in activating Src (Rahimi et al, Hauck et al, 2002;Hsia et al, 2003;Frame, 2004;Westhoff et al, 2004;Brunton et al, 2005). To determine if CD82 is involved in signaling to Src, we investigated Src activation following integrin engagement in CD82-expressing cells.…”