Tissue transglutaminase 2 (TG2) is overexpressed in epithelial ovarian cancer (EOC) and promotes intraperitoneal metastasis. How TG2 facilitates the spread of EOC is unknown. Here, we show that TG2 regulates the expression and function of matrix metalloproteinase-2 (MMP-2), a critical mediator of tissue invasiveness. TG2 knockdown down-regulates MMP-2 protein and mRNA expression in SKOV3, IGROV-1, MDA-MB-436, and PC-3 cancer cells. TG2 knockdown or inhibition of TG2 activity using KCC009 decreases MMP-2 gelatinase activity in cancer cells. MMP-2 expression and function are regulated by TG2 at transcriptional level, as demonstrated by quantitative PCR and reporter assays. We used bioinformatics and chromatin immunoprecipitation to identify a CREB binding site in the MMP-2 promoter. Binding of CREB to the MMP-2 promoter was diminished in cells that expressed decreased TG2 levels. TG2 knockdown decreased CREB phosphorylation, and CREB knockdown decreased MMP-2 expression. The effect of TG2 on CREB activity and MMP-2 transcription is mediated by TG2-dependent degradation of protein phosphatase 2 (PP2A-␣). We show that PP2A-␣ complexes with and is targeted for degradation by TG2. In addition to their related in vitro expression levels, TG2 and MMP-2 expression were significantly correlated in vivo, as shown by concordant immunostaining in peritoneal xenografts and in human ovarian tumors. The capacity of TG2 to regulate MMP-2 expression in vitro and in vivo identifies a mechanism that may facilitate tissue invasion and the spread of EOC. The demonstration that TG2 induced degradation of PP2A-␣ activates CREB, and thereby increases MMP-2 transcription, provides novel mechanistic insight into the prometastatic function of TG2.Transglutaminase 2 (TG2), 2 an enzyme overexpressed in epithelial malignancies (1, 2), cross-links proteins by acyltransfer between glutamine and lysine residues and participates in Ca 2ϩ -dependent post-translational protein modification by incorporating polyamines into peptide chains (3). We recently reported that TG2 is up-regulated in transformed ovarian epithelial cells and tumors compared with normal cells, and facilitates peritoneal dissemination of EOC cells (1, 4). TG2 has multiple functions. It strengthens integrin-dependent cell adhesion, modulates intracellular signaling, and remodels the extracellular matrix through protein cross-linking (5). To understand the involvement of TG2 in the process of intraperitoneal metastasis, we investigated its involvement in the regulation of proteins known to facilitate tumor invasion and spread.Matrix metalloproteinases (MMPs) are a family of secreted proteins that remodel and digest the extracellular matrix. In the context of malignancy, MMPs play a prominent role in metastasis and angiogenesis (6), because degradation of the extracellular matrix in the immediate vicinity of a tumor niche facilitates cancer cell invasion and escape from the primary tumor site (7,8). Regulation of MMP activity occurs at different levels (9). MMPs are secreted as pro...