Retinoic acid modulates RARα and RARβ receptors in human glioma cell lines

To identify retinoic acid (RA) signalling pathways involved in growth and differentiation in cells of the glial lineage, two human glioma cell lines were studied. The three RA receptors (RARs) mRNAs,were constitutively expressed, and of the three RXRs, RXR beta appeared predominant. Western blotting analysis confirmed the constitutive expression of RAR alpha and RAR beta. Treatment with all-trans-PA induced morphological changes in the two cell lines, which progressed from their normal pattern of randomly oriented spindle-shaped cells to fibroblast-like glial cells. RA up-regulated RAR alpha and RAR beta mRNAs in both cell lines. Interestingly, RA treatment up-regulated RAR beta proteins but not RAR alpha proteins, suggesting post-transcriptional regulations of RAR transcripts in glioma cells.