Regulation of Fibulin-2 Gene Expression by Integrin α3β1 Contributes to the Invasive Phenotype of Transformed Keratinocytes

The laminin-binding integrin alpha 3 beta 1 is highly expressed in epidermal keratinocytes, where it regulates both cell-autonomous and paracrine functions that promote wound healing and skin tumorigenesis. However, the roles for alpha 3 beta 1 in regulating gene expression programs that control the behaviors of immortalized or transformed keratinocytes remain underexplored. In the current study, we used a microarray approach to identify genes that are regulated by alpha 3 beta 1 in immortalized keratinocytes. alpha 3 beta 1-Responsive genes included several genes that are involved in extracellular matrix proteolysis or remodeling, including fibulin-2 and secreted protein acidic and rich in cysteine. However, alpha 3 beta 1-dependent induction of specific target genes was influenced by the genetic lesion that triggered immortalization, as alpha 3 beta 1-dependent fibulin-2 expression occurred in cells immortalized by either SV40 large T antigen or p53-null mutation, whereas alpha 3 beta 1-dependent expression of secreted protein acidic and rich in cysteine occurred only in the former cells. Interestingly, quantitative PCR arrays did not reveal strong patterns of alpha 3 beta 1-dependent gene expression in freshly isolated primary keratinocytes, suggesting that this regulation is acquired during immortalization, p53-null keratinocytes transformed with oncogenic RasV12 retained alpha 3 beta 1-dependent fibulin-2 expression, and RNAi-mediated knockdown of fibulin-2 in these cells reduced invasion, although not their tumorigenic potential. These findings demonstrate a prominent role for alpha 3 beta 1 in immortalized/transformed keratinocytes in regulating fibulin-2 and other genes that promote matrix remodeling and invasion.