Present studies demonstrate that treatment with arsenic trioxide (AT) lowered ectopically expressed or endogenous levels of Bcr-Abl protein, as well as induced apoptosis of Bcr-Abl-expressing cultured and primary chronic myeloid leukemia cells, including those refractory to imatinib mesylate. Treatment with AT neither affected bcr-abl mRNA transcript levels nor promoted the proteasomal degradation of Bcr-Abl. Importantly, in [35S]methionine-labeled leukemia cells, exposure to AT rapidly lowered the levels of the newly synthesized Bcr-Abl, indicating inhibition of bcr-abl mRNA translation. Treatment with AT rapidly inhibited the activity of 3-phosphoinositide-dependent protein kinase-1, as well as of p70 S6 kinase-1. p70 S6 kinase-1 is known to be a positive regulator of the translation of a group of mRNAs that possesses a long and highly structured 5′ -untranslated region (UTR) containing a tract of oligopyrimidines (TOP). Because bcr-abl mRNA was discovered to possess a long and highly structured 5′-UTR containing a 12-pyrimidine TOP sequence in its 5′-UTR, we determined the effect of AT in Jurkat cells with ectopic expression of a 5′-UTR-deleted mutant of the bcr-abl gene, i.e., Jurkat/Bcr-Abl (5′UTR-) cells. Treatment with AT neither lowered the levels of the 5′-UTR-deleted mutant of Bcr-Abl nor induced apoptosis of Jurkat/Bcr-Abl (5′UTR-) cells. Taken together, these findings demonstrate a novel mechanism by which AT down-regulates Bcr-Abl levels and induces apoptosis of Bcr-Abl-positive chronic myelogenous leukemia cells.
|Original language||English (US)|
|Number of pages||9|
|State||Published - Nov 15 2003|
ASJC Scopus subject areas
- Cancer Research