N-Acetyl-L-Cysteine Upregulates TIMP-1 And TIMP-2 Expression In Squamous Cell Carcinoma

Matrix Metalloproteinase (MMP) expression and activation is important in the progression of oral dysplasia to squamous cell carcinoma (SCC) (Jordan, 2004). Elevated MMP-1, -2, and -9 expression is commonly observed in early stage SCC (Sheu, 2004; Samantaray, 2004), and is predictive of SCC tumor cell aggressiveness and metastatic potential (Xu, 2003; Katayama, 2004). N-Acetyl-L-Cysteine (NAC) is a prototypic chemopreventative agent, representing a class of thiol containing macromolecules capable of inhibiting MMP activation and potentially SSC progression. As a potent antioxidant, NAC has the ability to alter cellular redox status, thereby affecting the activity of redox sensitive transcription factor that regulate expression of MMPs and their endogenous inhibitors - tissue inhibitors of metalloproteinases (TIMP). Objective: To determine if local delivery of NAC affects the expression of MMP-1, -2, -9, and -13, and their endogenous inhibitors TIMP-1 and TIMP-2, in SCC cells in vitro. Methods: ATCC SCC cell lines (n=5) were stimulated with TNF-α, SIN-1, or H₂O₂ to upregulate MMP expression. Concurrently, cells were treated with NAC or placebo control. Cells were harvested, total RNA isolated, and cDNA synthesized. Relative expression of MMP-1, -2, -9, –13, and TIMP-1 and –2 mRNA was analyzed by Real-time PCR. Results: Treatment of SCC cells with NAC did not significantly alter the expression of MMP-1, -2, -9, or -13 mRNA(p=NS, Kruskal-Wallis, Z-test). Conversely, expression of TIMP-1 and TIMP-2 was upregulated >2fold (p<0.05, Kruskal-Wallis, Z-test). Conclusions: These data suggest that NAC may be capable of inhibiting MMP activation by increasing expression of their endogenous inhibitors, TIMP-1 and TIMP-2. These experiments provide a basis for the continued development of NAC as an antioxidant-based, chemopreventative agent in the treatment of SCC. Supported by NIDCR-F30-DEO5755,NCI-R01-CA95901.