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Changes in the levels of integrin and focal adhesion kinase (FAK) in human melanoma cells following 532 nm laser treatment

Despite the increase in laser therapy, concern remains that sublethal treatment of pre‐malignant lesions may adversely affect the biological behaviour of surviving cells. Integrin receptors mediate interaction of cells with the extracellular matrix and their occupation leads to focal adhesion kinase (FAK) activation. Using our previously established model we have now investigated subcellular changes and compared integrin and FAK concentrations, the degree of FAK phosphorylation and its association with the β1 integrin in laser vs. non‐laser treated cells. We treated cells with laser generated from a frequency doubled Q‐switched (Nd:YAG) laser system (532 nm) at 0.4 J/cm2 twice per week for 4 weeks. Using cell lysates we performed Western immunoblotting 24 hr later to detect integrin subunits and FAK proteins and immunoprecipitation to investigate FAK phosphorylation and its association with β1. Cell morphology was examined using electron microscopy. SK23 and G361 cells exhibited an 3.4‐ and 11.2‐fold increase, respectively, in FAK protein following laser treatment. FAK phosphorylation in SK23 cells was increased by 82%, whereas FAK phosphorylation in G361 cells was reduced slightly (2%). Furthermore, both α3 and 4 integrins were up‐regulated, by approximately 4‐fold and 7‐ to 9‐fold, respectively. In addition, the β1 integrin was proteolysed in both cell lines and the levels of FAK associated with β1 was increased (2.1‐ and 2.7‐fold, respectively). Finally, laser treatment of SK23 cells caused an increased number of cell processes. Sublethal 532 nm laser light thus induces changes in integrin and FAK concentrations and subsequently influences cellular attachment and morphology. Int. J. Cancer 82:353–358, 1999. © 1999 Wiley‐Liss, Inc.