Immunohistochemical evaluation of glutaminase-1 enzyme in oral squamous cell carcinoma

Background and objectives Malignant cells reprogram their metabolism. Glutamine is a major biosynthetic precursor apart from glucose in various cancers. Glutaminase 1 (kidney type) is the rate limiting enzyme in glutamine metabolism, which is increased in cancers of prostate, breast, colorectum, ovary and oral squamous cell. We aimed to evaluate the intensity and extent of immunohistochemical expression of glutaminase1 in various grades of oral squamous cell carcinoma (OSCC) and investigate whether any association exists between the glutaminase 1expression with staging, grading and tumour infiltrating lymphocytes. Methods This retrospective analysis included 98 formalin-fixed, paraffin-embedded tissue blocks of clinically and histopathologically confirmed cases of OSCC. One section was stained with haematoxylin and eosin and the other, immunohistochemically for glutaminase 1(GLS1). Staging, grading, tumour infiltrating lymphocytes were evaluated for their relation with GLS1 immunoscore. Results Statistically significant association was noted between GLS1 immunointensity ( P <0.001) immunoextent ( P <0.001) and the immunoscore ( P= 0.007) with the worsening grades of OSCC. There was no significant association between TNM staging P <0.61) and tumour infiltrating lymphocytes with GLS1 immunoscore ( P =0.30). Interpretation and conclusions Glutaminase 1 expression increases with worsening grade of OSCC signifying an altered metabolic phenotype as the cancer cells lose differentiation.