Concentration-dependent effects of 9-cis retinoic acid on neuroblastoma differentiation and proliferation in vitro

The observation that neuroblastoma cells differentiate in response to retinoic acid (RA) in vitro has led to clinical trials using either 13-cis or all-trans RA. Since 9-cis RA may also have important biological functions, we have compared the potential of RA isomers to induce differentiation and inhibit cell proliferation of SH SY 5Y neuroblastoma cells. 9-cis RA at high concentrations is better at inducing morphological differentiation than either all-trans or 13-cis RA and as effective at inhibiting proliferation. Hence, 9-cis RA or stable analogues may have important therapeutic potential in the treatment of neuroblastoma.