Expression of heat shock protein 27 and alpha-crystallins in human retinoblastoma after chemoreduction.

Abstract

Small heat shock proteins (sHSP) play an important role in the resistance to anticancer drugs. We examined the expression of the sHSP family, HSP27 and alpha-crystallins, in human retinoblastoma with and without preoperative chemotherapy. Eighteen enucleated eyes from patients with retinoblastoma were used. Six patients had undergone chemotherapy before enucleation. Formalin-fixed, paraffin-embedded tissue sections were processed for H&E staining and examined by immunohistochemistry using anti-HSP27 and alpha-crystallins antibodies. Eleven of 12 cases with no history of preoperative chemotherapy showed weakly positive or negative staining for HSP27, whereas six and five cases were strongly positive for alphaA and alphaB-crystallin, respectively. In the six cases with a history of chemotherapy, several viable retinoblastoma cells remained. Immunoreactivity for HSP27 and alphaB-crystallin was strongly detected in the cytoplasm of viable retinoblastoma cells, while alphaA-crystallin immunoreactivity was less marked. Immunoreactivity for HSP27 was significantly higher in retinoblastoma cases with preoperative chemotherapy than in those without chemotherapy (p<0.0001). In contrast, immunoreactivity for alphaA-crystallin was significantly lower in cases with chemotherapy than in cases without chemotherapy (p<0.01). HSP27 and alphaB-crystallin, but not alphaA-crystallin, were highly expressed in viable tumour cells after chemotherapy, suggesting that HSP27 and alphaB-crystallin may protect tumour cells from apoptotic signals produced by anticancer drugs in retinoblastoma.