MiR-21 and MiR-155 Expressions in Oral Squamous Cell Carcinoma: A Retrospective Study in Mexican Patients using FFPE...

Oral squamous cell carcinoma (OSCC) is a prevalent malignancy with poor survival outcomes, particularly in regions with high tobacco use and less early detection. MicroRNAs (miRNAs) such as miR-21 and miR-155 have been implicated in tumor progression and viral oncogenesis. This study aimed to evaluate the expressions of miR-21 and miR-155 in OSCC tissues and their association with histological differentiation and HPV infection in a Mexican population.

This retrospective cross-sectional study included 30 OSCC cases and 30 age- and sex-matched healthy oral tissue controls. Total RNA was extracted from formalin-fixed paraffin-embedded tissue samples, and miR-21 and miR-155 levels were quantified using RT-qPCR. HPV genotyping (types 16 and 18) was performed via endpoint PCR. Statistical analysis included Mann-Whitney U test, Kruskal-Wallis test, and Fisher's exact test. Effect sizes were calculated using Glass's delta, and a significance level of P < 0.05 was applied.

MiR-21 and miR-155 were significantly upregulated in OSCC tissues compared to controls (P < 0.001 for both), with large effect sizes (Glass's δ = 3.78 and 2.63, respectively). No significant association was found between miRNA expression levels and tumor differentiation grade (P > 0.05). HPV was detected in 26.6% of OSCC samples, with HPV-16 being the most frequent subtype. A significant association was observed between HPV positivity and tobacco use (P = 0.002), but not with miRNA expression levels.

The overexpression of miR-21 and miR-155 in OSCC supports their potential as diagnostic biomarkers in oral cancer. While their levels were not significantly associated with tumor grade or HPV status, their consistent elevation in malignant tissues warrants further investigation into their mechanistic role in OSCC pathogenesis and their applicability in biomarker panels for early detection, especially in Latin American populations.