Distinctive immunohistochemical profiles of small heat shock proteins (heat shock protein 27 and αb-crystallin) in human brain tumors

BACKGROUND. Recent studies have described αβ-crystallin as a member of the small heat shock (HSP) family, and the expressions of α-crystallin- related small heat shock proteins, namely HSP27 and αB-crystallin, in the brain appear to be regulated in a similar way by various stress conditions. METHODS. A comparative immunohistochemical analysis was performed on 198 human brain tumors to examine the expressions of HSP27 and αβ-crystallin. RESULTS. Positive staining with HSP27 was frequently observed in schwannomas, craniopharyngiomas, epidermoid cysts, and metastatic tumors to the brain. The immunopositivity of HSP27 was relatively low in tumors originating from neuroepithelium as well as in meningiomas; however, a statistically significantly higher percentage of HSP27-positive cells was noted in their anaplastic counterparts, such as glioblastomas, anaplastic oligodendrogliomas, anaplastic ependymomas, and anaplastic meningioma (P < 0.005). Conversely, a positive immunoexpression of αB-crystallin was frequently observed among astrocytic tumors, schwannomas, hemangioblastomas, and chordomas. CONCLUSIONS. The immunohistochemical expression of HSP27 and αB-crystallin differed among histologic types of tumors. Furthermore, the immunopositivity of HSP27, which was considered to play a role not only in drug resistance but also in the regulation of cell proliferation, increased in proportion to the anaplasia of the tumors.