EXPRESSION OF THE SMALL HEAT-SHOCK PROTEIN (HSP) 27 IN HUMAN ASTROCYTOMAS CORRELATES WITH HISTOLOGIC GRADES AND TUMOR-GROWTH FRACTIONS

1. Cellular expression and distribution of the stress response small h eat shock protein 27 (hsp27) in 39 high-grade astrocytomas (27 gliobla stoma multiformes, 12 anaplastic astrocytomas) and in 27 low-grade ast rocytomas (grade I-II) were analyzed immunohistochemically. 2. The cor relation between hsp27 expression and tumor growth fractions of the as trocytomas was examined following Ki-67 immunostaining. 3. The hsp27 s taining was cell cytoplasmic. The hsp27 immunopositive rate was signif icantly higher in high-grade astrocytomas; the rates were 74% for glio blastomas, 58% for anaplastic astrocytomas, and 37% for low-grade astr ocytomas, The small and large tumor cells, especially in glioblastomas , multinucleated tumor giant cells, tumor cells in the pseudopalisadin g and necrotic areas, cells of the microvascular endothelial prolifera tions, and tumor vascular smooth muscles were usually hsp27 positive, The mean percentage of hsp27-positive cells was significantly higher i n the glioblastomas alone and in the combined high-grade astrocytomas, compared to the low-grade, and in recurrent rather than in primary hi gh-grade astrocytomas. 4. The high-grade astrocytomas had a highly sta tistical significant Ki-67 labeling index. The Ki-67 labeling indices were significantly higher in the hsp27-positive than the hsp27-negativ e astrocytomas, irrespective of the histological grade. In the high-gr ade astrocytomas with a Ki-67 labeling index of five and above, 81% of those tumors were hsp27 positive. 5. Thus, a large number of human as trocytomas express hsp27, and hsp27 expression correlates with histolo gical grades of astrocytoma and with tumor growth fractions. This bein g the case, hsp27 is likely to have a role in the growth of human astr ocytomas.