Loss of TRIM29 Alters Keratin Distribution to Promote Cell Invasion in Squamous Cell Carcinoma

TRIM29 (tripartite motif-containing protein 29) is a TRIM family protein that has been implicated in breast, colorectal, and pancreatic cancers. However, its role in stratified squamous epithelial cells and tumors has not been elucidated. Here, we investigate the expression of TRIM29 in cutaneous head and neck squamous cell carcinomas (SCC) and its functions in the tumorigenesis of such cancers. TRIM29 expression was lower in malignant SCC lesions than in adjacent normal epithelial tissue or benign tumors. Lower expression of TRIM29 was associated with higher SCC invasiveness. Primary tumors of cutaneous SCC showed aberrant hypermethylation of TRIM29. Depletion of TRIM29 increased cancer cell migration and invasion; conversely, overexpression of TRIM29 suppressed these. Comprehensive proteomics and immuno-precipitation analyses identified keratins and keratin-interacting protein FAM83H as TRIM29 interactors. Knockdown of TRIM29 led to ectopic keratin localization of keratinocytes. In primary tumors, lower TRIM29 expression correlated with the altered expression of keratins. Our findings reveal an unexpected role for TRIM29 in regulating the distribution of keratins, as well as in the migration and invasion of SCC. They also suggest that the TRIM29-keratin axis could serve as a diagnostic and prognostic marker in stratified epithelial tumors and may provide a target for SCC therapeutics. Significance: These findings identify TRIM29 as a novel diagnostic and prognostic marker in stratified epithelial tissues. (C) 2018 AACR.