A64
The role of retinoic acid receptors in differentiation, gene expression and apoptosis of neuroblastoma
Danielle Lindley, Frida Ponthan, Bojidar Goranov, Chris Redfern
Newcastle University, Newcastle upon Tyne, UK
Background
Retinoic acid induces neuroblastoma cell differentiation and 13-cis retinoic acid is used to treat patients with high-risk neuroblastoma. Previous work suggests that increased expression of Retinoic-acid-receptor (RAR)γalters responses to all-trans retinoic acid (ATRA) by inducing apoptosis rather than differentiation. Therefore, RAR-specific activation may promote differentiation or apoptosis and RAR-specific analogues may improve neuroblastoma therapy by targeting more-favourable cellular responses. The aim of this study was to test the hypothesis that increased expression of RARαwould increase differentiation and decrease apoptotic responses to retinoids.
Method
RARαcDNA was cloned into the tetracycline-inducible pcDNA4/TO vector and stably-transfected into neuroblastoma cells expressing the tetracycline repressor. Responses to ATRA and other retinoids were studied by assessing cell morphology and measuring cell viability and apoptosis. Real-time quantitative PCR was used to measure the induction of retinoid-responsive genes.
Results
RARαwas expressed in a tightly-regulated manner by varying the dose and time of tetracycline treatment. Increased expression of RARαresulted in different morphological and cell attachment properties compared to cells over-expressing RARγbut had no effect on cell proliferation in response to retinoids. Morphological responses to retinoids were altered. Increased expression of RARαor RARγdid not increase RARβ induction but markedly increased the induction of CYP26 in response to ATRA.
Conclusion
These results suggest that increased expression of RARαor RARγ produce different retinoid-dependent responses and suggest that RAR-specific analogues may be used to target specific cellular responses. The results also raise important questions about the the mechanisms of induction of retinoid-responsive genes.
