Change in gene expression subsequent to induction of Pnn/DRS/memA: increase in p21(cip1/waf1)

Pnn (PNN) is a nuclear and cell adhesion-related protein. Previous work has suggested that Pnn/DRS/memA is a potential tumor suppressor involved in th e regulation of cell adhesion and cell migration. Using the ecdysone-induci ble mammalian expression system, a stable inducible GFP-tagged human Pnn ge ne (PNNGFP) expressing 293 cell line was created (EcR293-PNNGFP), Cells ind uced to express PNNGFP not only exhibited increased cell-cell adhesion but also exhibited changes in cell growth and cell cycle progression. cDNA arra y analyses, together with real time PCR, revealed that the effects of exoge nously expressed Pnn on cellular behavior may be linked to the regulation o f the expression of specific subset genes. This subset includes cell cycle- related genes such as p21(cip1/waf1), CDK4, CPR2; cell migration and invasi on regulatory genes such as RhoA, CDK5, TIMP-1, MMP-7, and EMMPRIN; and MIC -1, Concordant with previous observations of Pnn-induced phenotype changes, genes coding for epithelial associated processes and cell division control s were elevated, while those coding for increased cell motility and cellula r reorganizations were downregulated. We utilized p21 promoter-luciferase r eporter constructs and demonstrated that a marked stimulation of p21 promot er activity in 293 cells correlated with increased Pnn expression, Taken to gether, these data indicate that Pnn may participate in the regulation of g ene expression, thereby, positively promoting cell-cell adhesion, and negat ively affecting cell migration and cell proliferation.