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FRNK blocks v-Src-stimulated invasion and experimental metastases without effects on cell motility or growth
Christof R Hauck1, Datsun A Hsia, Xose S Puente
1Department of Immunology, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA.
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.
Insights
Focal adhesion kinase (FAK) inhibition by FRNK blocks cancer cell invasion and metastasis. This study reveals FAK
Area of Science:
- Cell Biology
- Molecular Oncology
- Signal Transduction
Background:
- Focal adhesion kinase (FAK) is a substrate of viral Src (v-Src).
- The specific role of FAK in v-Src-mediated cellular transformation is not fully understood.
- Investigating FAK's function in v-Src signaling is crucial for understanding cancer progression.
Purpose of the Study:
- To elucidate the role of FAK in v-Src-induced cell invasion and metastasis.
- To determine the molecular mechanisms by which FAK contributes to Src transformation.
- To assess the potential of FAK inhibition as a therapeutic strategy against metastasis.
Main Methods:
- Stable expression of FAK C-terminal domain (FRNK) in v-Src-transformed NIH 3T3 fibroblasts.
- Assays for cell invasion through Matrigel and experimental metastasis in nude mice.
- Analysis of v-Src-FAK signaling complex formation, p130Cas phosphorylation, and downstream kinase activation (ERK, JNK, Akt).
- Measurement of matrix metalloproteinase-2 (MMP-2) mRNA levels and secretion.
- MMP-2 promoter activity assays and rescue experiments with MMP-2 overexpression.
Main Results:
- FRNK expression inhibited cell invasion and experimental metastasis without affecting cell motility.
- FRNK disrupted v-Src-FAK complex formation, reduced p130Cas phosphorylation, and attenuated ERK/JNK activation.
- FRNK did not impact v-Src-stimulated Akt activation, anchorage-independent growth, or subcutaneous tumor formation.
- FRNK decreased MMP-2 mRNA levels and secretion, and inhibited MMP-2 promoter activity.
- Overexpression of wild-type MMP-2, but not a catalytically inactive mutant, rescued v-Src-stimulated invasion in FRNK-expressing cells.
Conclusions:
- FAK plays a critical role in Src-stimulated cell invasion and metastasis.
- The Src-FAK signaling pathway, particularly its effects on MMP-2, is important for tumor cell metastasis.
- FRNK's inhibitory activity on invasion is dependent on its localization to focal contacts.
- Targeting the Src-FAK pathway may offer a strategy to inhibit cancer cell invasion and metastasis.