HUMAN RETINOBLASTOMA - IN-VITRO DIFFERENTIATION AND IMMUNOGLOBULIN SUPERFAMILY ANTIGEN MODULATION BY RETINOIC ACID

Suspension and attachment cultures of Y79 human retinoblastoma cells w ere treated with all-trans retinoic acid (RA) for up to 10 days to ass ess its effect on growth and cell-surface expression of immunoglobulin superfamily antigens MHC class I and class II, ICAM-1, NCAM and Thy1. RA up to 10 mu M induced growth inhibition, and marked morphological differentiation with extension of prominent processes resembling neuri tes was seen in attachment cultures. However, above 10 mu M RA produce d extensive cell death. We also observed increased cell-surface expres sion of MHC class I, ICAM-1, NCAM and Thy1 on Y79 cells treated with 1 0 mu M over 10 days; constitutive MHC class II expression was not appa rent, nor did RA treatment appear to induce Y79 cells to express MHC c lass immunoreactivity. The up-modulation of cell-adhesion molecules (N CAM, ICAM-1 and Thy1) and immune recognition molecules (NCAM, ICAM-1 a nd MHC class I), associated with reduced growth and tumour cell differ entiation, suggests that RA may have a potential role in regulating th e growth and development of retinoblastoma tumours.