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 chromosomal proteins that bend DNA, bind preferentially to distorted DNA structures, and promote the assembly of site-specific DNA binding proteins. Recent reports indicate that HMGB1 functions as a proinflammatory cytokine. Here, we studied expressions of HMGB1 and HMGB2 in human renal cancer. Material and Methods: Immunohistological expressions of HMGB1 and HMGB2 were assessed in 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 is expressed more frequently in cancers beyond the pT1b classification than in those at the pT1a classification. Higher tumor grades (? G2) were also significantly linked with the cytosolic expression of HMGB1. HMGB2 was expressed in the nucleus in 35 of 39 (89.7%) renal clear cell cancers, while its expression in the cytosol was observed in only 7 case (17.9%). Linkage between cytosolic expression of HMGB2 and T classifications was weakly observed, while that between nuclear expression and T classifications was not. Conclusion: HMGB1 expressed in the cytoplasm may be an effective marker indicating higher T classifications and tumor grades.