Evaluation of superoxide dismutase, an antioxidant enzyme, in oral squamous cell carcinoma: A systematic review and meta-analysis

Objective: The objective is to qualitatively and quantitatively review the published literature on superoxide dismutase (SOD) levels in oral squamous cell carcinoma (OSCC). Materials and Methods: MEDLINE (via PubMed), SCOPUS, Science Direct, Cochrane Library, ProQuest, Google Scholar, and gray literature were comprehensively searched. Human clinical studies published between 2000 and 2021 were included. The Newcastle–Ottawa Scale was used to evaluate the risk of bias in the studies. Results: Of the 873 articles screened, six studies were included, evaluating 640 patients (554 OSCC cases and 113 controls). SOD levels in OSCC subjects were significantly lesser (P < 0.01) compared to healthy controls in spectrophotometry analysis, whereas its immuno-expression was significantly higher in the OSCC tissue samples in immunohistochemistry. In the meta-analyses related to SOD analysis by spectrophotometry, the overall effect size of tissue SOD in OSCC and control group were 8.51 and 11.62 U/mg protein, respectively. In the meta-analyses related to SOD analysis by immunohistochemistry, the overall effect size of tissue SOD in OSCC was 55.55% and 3.61% for cell staining, respectively. Conclusion: Decreased SOD levels in OSCC tissue samples in spectrophotometry and high immunoexpression in immunohistochemistry accurately reflect increased oxidative stress (OS) levels. Further studies are required to understand the increase in SOD levels in OSCC tissue. Correlation analysis between SOD levels and established clinicopathological prognostic markers could aid in formulation of OS-based prognostication and treatment planning.