HSP90AB1 and cancer: In malignant tumors, the proliferation index (PI), which was marked by proliferating cell nuclear antigen (PCNA; PCNA-PI) was 49.95±14.569, which was significantly higher compared with that in benign tumors (P<0.001), which was in accordance with the upregulation of HSP70, HSP86 or HSP84; however, an adverse correlation was found between HSP27 expression and PCNA (each P<0.05).