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Requirement for focal adhesion kinase in tumor cell adhesion
1Department of Anatomy & Developmental Biology, St. George's Hospital Medical School, London, UK.
Abstract:
Focal adhesion kinase (FAK) is a nonreceptor protein tyrosine kinase and a major phosphotyrosine-containing protein. FAK is found in cell-matrix attachment sites (focal adhesions), and is activated on integrin-ligand binding and by other signaling pathways. Several roles have been proposed for FAK; here we report a novel function. We observed abundant FAK protein in all human melanoma cell lines tested except COLO839, a line that grows predominantly in suspension and was derived from peripheral blood. Five adherent lines, isolated from solid metastases in the same patient as COLO839, did express FAK. We derived four adherent sublines from COLO839. These did express FAK, even when plated on bacteriological plastic, to which they did not adhere. Thus, substrate attachment was not required for FAK expression. Three of the adherent sublines were then grown in the presence of antisense oligonucleotides to the initial FAK coding sequence. All showed substantially reduced FAK expression and, interestingly, the cells largely detached from the substrate while continuing to grow. Similar results were obtained with an independent melanoma line, DX3. Thus, FAK expression appears to be required by melanoma cells for substrate adhesion.
Insights
Focal adhesion kinase (FAK) is crucial for melanoma cell adhesion to substrates. Reduced FAK expression in melanoma cells leads to detachment while maintaining growth, revealing a novel role in substrate attachment.
Area of Science:
- Oncology
- Cell Biology
- Biochemistry
Background:
- Focal adhesion kinase (FAK) is a key protein tyrosine kinase involved in cell signaling.
- FAK localizes to focal adhesions and is activated by integrin-ligand binding.
- Its roles in cell adhesion and cancer progression are under investigation.
Purpose of the Study:
- To investigate the role of FAK in human melanoma cell adhesion.
- To determine if FAK expression is necessary for melanoma cells to attach to substrates.
Main Methods:
- Analysis of FAK protein expression in various human melanoma cell lines.
- Derivation of adherent sublines from a non-adherent melanoma line.
- Treatment with antisense oligonucleotides to reduce FAK expression.
- Observation of cell adhesion and growth characteristics.
Main Results:
- FAK protein was abundant in adherent melanoma lines but absent in a suspension line (COLO839).
- Sublines derived from COLO839 expressed FAK even without substrate attachment.
- Antisense-mediated reduction of FAK expression caused melanoma cells to detach from substrates while continuing to grow.
- Similar results were observed in the DX3 melanoma line.
Conclusions:
- FAK expression is essential for melanoma cell adhesion to substrates.
- FAK plays a critical role in mediating melanoma cell attachment, independent of substrate adherence.
- Targeting FAK could potentially disrupt melanoma metastasis by affecting cell adhesion.