Regulatory function of fyn in oral SCC invasion

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DESCRIPTION: Oral squamous cell carcinoma (SCC) is characterized by invasion and metastasis, and integrin receptors participate in these processes. This application is a continuation of our previously funded work, which focused on the role of the alpha-v-beta6 integrin and tenascin-C (TN-C) as potential modulators of oral SCC invasion. The alpha-v-beta6 fibronectin/TN-C integrin is not found in normal oral keratinocytes but is highly expressed in oral SCC. We expressed beta6 in poorly invasive SCC9 cells and established the highly invasive SCC9beta6 cell line. When SCC9beta6 cells were plated on fibronectin (FN), autophosphorylation of the Src family kinase Fyn and focal adhesion kinase at Tyr 397 and Tyr 925 was increased as compared with SCC9 cells. Autophosphorylation at Tyr 925 but not Tyr 397 depended upon Fyn activation. Activation of the MAP kinase pathway (ERK1/2) was also increased in SCC9beta6 cells. SCC cells and peri-tumor fibroblasts (PTF) were used to simulate in vivo conditions. SCC9/PTF co-cultures organized a rich FN matrix, which was decreased in SCC9beta6/PTF co-cultures. Gelatin zymographs indicated SCC9 and SCC9beta6 cells expressed equivalent levels of matrix metalloproteinases MMP2 and MMP9. In contrast, casein zymography indicated increased MMP3 activation in the SCC9beta6 cells. Adding anti-alpha-v-beta6 antibodies (10D5) or the general MMP inhibitor GM6001 restored FN assembly and suppressed invasion through a reconstituted basement membrane. These results suggest that expression ofalpha-v-beta6 and activation of Fyn and MMP3 modulate oral SCC invasion and FN matrix organization. To evaluate Fyn and MMP3 activation in vivo, this application addresses these questions: 1) Does suppression of Fyn activity affect oral SCC growth, invasion, and metastasis? 2) Does expression of a constitutively active Fyn modulate oral SCC growth, invasion and metastasis? 3) Does expression of a constitutively active MMP3 modulate oral SCC invasion and metastasis? Understanding how Fyn and MMP3 may modulate oral SCC behavior may potentially lead to targets for future therapeutic intervention.