However, the response of APL with <i>RARB</i> translocation to retinoids was attenuated compared with that of <i>PML-RARA</i>, an observation in line with the clinical resistance of <i>RARB</i>-positive APL to ATRA.
Two APL relapsed patients with clinical resistance to ATRA therapy were evaluated for the presence of nucleotide mutations in the LBD of PML/RARa gene and then treated with arsenic trioxide (As2O3).
These findings suggest that mutations in the RARalpha /E-domain of the PML/RARalpha chimeric gene may confer clinical resistance to ATRA therapy in patients with APL.