Purpose: 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 α-crystallins, in human retinoblastoma with and without preoperative chemotherapy.
Methods: 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 hematoxylin-eosin staining and examined by immunohistochemistry using anti-HSP27 and α-crystallins antibodies.
Results: 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 αA and αB-crystallin, respectively. In the six cases with a history of chemotherapy, several viable retinoblastoma cells remained. Immunoreactivity for HSP27 and αB-crystallin was strongly detected in the cytoplasm of viable retinoblastoma cells, while αA-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 αA-crystallin was significantly lower in cases with chemotherapy than in cases without chemotherapy (P<0.01).
Conclusions: HSP27 and αB-crystallin, but not αA-crystallin, were highly expressed in viable tumour cells after chemotherapy, suggesting that HSP27 and αB-crystallin may protect tumour cells from apoptotic signals produced by anticancer drugs in retinoblastoma.