Objective: To examine the expression of alpha-crystallin, a small heat-shock protein family, and apoptosis in retinal neoplastic cells.
Methods: Thirteen enucleated globes were included in this study, 1 with retinocytoma and 12 with retinoblastoma. Formalin-fixed paraffin-embedded tissue sections were processed for immunohistochemistry with alpha-crystallin antibodies. Apoptotic cells were detected using the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) method.
Results: In the retinocytoma, alphaA-crystallin was expressed in the cytoplasm of all tumor cells, whereas alphaB-crystallin immunoreactivity was only weakly positive. Apoptotic cells were rarely noted in retinocytoma cells; the apoptotic index was 0.29. Examination of the retinoblastoma globes revealed 6 cases (50%) that were strongly positive for alphaA-crystallin. The mean (SD) apoptotic indices in the strongly and weakly positive cases were 3.55 (2.61) and 7.50 (2.61), respectively. The apoptotic index was significantly higher in those cases that were weakly positive for alphaA-crystallin than in those that were strongly positive (P < .05). No correlation was observed between apoptotic index and alphaB-crystallin immunoreactivity, although 50% of retinoblastomas were strongly positive for alphaB-crystallin.
Conclusions: The alphaA- and alphaB-crystallins are expressed in retinoblastomas, and alphaA-crystallin expression may prevent apoptosis of neoplastic cells. Clinical Relevance Suppression of alphaA-crystallin may be useful in controlling tumor growth.