Cytosolic HMGB1 Expression in Human Renal Clear Cell Cancer Indicates Higher Pathological T Classifications and Tumor Grades

Purpose: High mobility group box (HMGB) proteins are nuclear nonhistone chromosomalproteins that bend DNA, bind preferentially to distorted DNA structures, and promote the assemblyof site-specific DNA binding proteins. Recent reports indicate that HMGB1 functionsas a proinflammatory cytokine. Here, we studied expressions of HMGB1 and HMGB2 in humanrenal cancer.Material and Methods: Immunohistological expressions of HMGB1 and HMGB2 were assessedin 39 surgically resected human renal cancer specimens.Results: HMGB1 was expressed in the nucleus in 37 out of 39 (94.9%) renal clear cell cancers,while its expression in the cytosol was noted in 19 cases (48.7%). Cytosolic HMGB1 isexpressed more frequently in cancers beyond the pT1b classification than in those at the pT1aclassification. Higher tumor grades (≥ G2) were also significantly linked with the cytosolicexpression of HMGB1. HMGB2 was expressed in the nucleus in 35 of 39 (89.7%) renal clearcell cancers, while its expression in the cytosol was observed in only 7 case (17.9%). Linkagebetween cytosolic expression of HMGB2 and T classifications was weakly observed, while thatbetween nuclear expression and T classifications was not.Conclusion: HMGB1 expressed in the cytoplasm may be an effective marker indicating higherT classifications and tumor grades