Genetic predisposition is reportedly involved in early-onset oral cancer, although the genetic basis of this cancer remains unclear. The major histocompatibility complex class I-related chain A (MICA) plays a crucial role in eliminating malignant tumors by activating NKG2D, the natural killer (NK) receptor. MICA polymorphism might affect its binding to NKG2D. We aimed to find whether MICA gene microsatellite polymorphism is involved in the risk of oral squamous cell carcinoma (OSCC) development in a Japanese population.
We recruited 386 patients with OSCC and 103 healthy controls. Genomic DNA was analyzed by PCR for microsatellite repeat polymorphism in the transmembrane region of the MICA gene. The groups were compared for the prevalence of various alleles and their association with disease prognosis and survival.
We found that adolescents and young adults (AYA) with OSCC were more likely to have the MICA A5.1 homozygous genotype than healthy controls (P = 0.0001), but their survival rate was higher than with other MICA genotypes (P = 0.0185).
These results suggest that cancer’s immune escape is facilitated by MICA’s failure to activate the NK cells. MICA A5.1 homozygosity plays a role in individual susceptibility to OSCC, increasing the risk of early-onset oral cancer. However, such patients have a better prognosis than those with other MICA genotypes.

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