MicroRNA Expression Profiling of Cutaneous Squamous Cell Carcinomas Arising in Different Sites

Objective To examine the microRNA (miRNA) expression profile of cutaneous squamous cell carcinoma (cSCC) tumors from aggressive head and neck locations compared with nonaggressive anatomic sites and normal controls. Study Design Retrospective analysis of miRNA expression. Setting Tertiary care center. Subjects and Methods Tissue samples were collected from 3 anatomic regions: aggressive head and neck sites (ie, ears/lip), nonaggressive locations (ie, extremities/trunk), and adjacent normal skin. RNA was isolated from tissue cores of 45 samples (18 aggressive sites, 15 nonaggressive sites, and 12 normal‐adjacent skin). miRNA expression analysis was completed for approximately 800 miRNAs using the NanoString nCounter panel. Five candidate miRNAs were selected for validation. Quantitative real‐time polymerase chain reaction (qRT‐PCR) was performed on the original samples plus 30 additional tissue samples (7 aggressive sites, 14 nonaggressive sites, and 9 normal‐adjacent skin). Results Five candidate miRNAs with significant differences in miRNA expression ( P < 0 ≤. 001) from discovery samples were selected: miR‐21, miR‐31, let‐7g, miR‐93 , and miR‐22 . Relative expression for these miRNAs using qRT‐PCR in the new sample set did not reveal any significant differences using 1‐way analysis of variance. When sets were combined, miR‐21 showed increased expression in aggressive tumors relative to nonaggressive tumors ( P =. 009), but no others reached statistical significance. Conclusion cSCC behaves more aggressively when originating from specific anatomical subsites of the head and neck. Of 5 miRNAs evaluated, only miR‐21 showed significantly higher expression in tumors from aggressive sites relative to nonaggressive sites. Larger sample sizes are needed to evaluate other miRNAs.