KMT2A-Rearranged Infant Acute Lymphoblastic Leukemia Cells Undergo ER-Stress-Induced Apoptosis Following Exposure to Proteasome Inhibitors

• Published in: Blood 2019-11, Vol.134 (Supplement_1), p.1283-1283
• Main Authors: Kim, Wonil, Koss, Cary S., Gruber, Tanja A.
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2019-127699

Infants diagnosed with KMT2A-rearranged (KMT2Ar) acute lymphoblastic leukemia (ALL) have a poor prognosis with an event free survival of 23-44%. To identify new treatment approaches we previously performed in vitro and in vivo assays to evaluate the activity of FDA approved compounds in 15 primary KMT2Ar infant leukemia samples. Three classes of agents were found to be active in these assays: proteasome inhibitors, anthracyclines, and histone deacetylase inhibitors (HDACi). KMT2Ar infant leukemia samples were exquisitely sensitive to the proteasome inhibitor bortezomib, requiring 10-100 fold less drug to achieve 50% toxicity when compared to non-KMT2Ar childhood ALL. Bortezomib is FDA approved for multiple myeloma and laboratory studies using this model system have previously demonstrated responses to be mediated through several mechanisms including NFKB inhibition, stabilization of cell cycle regulatory proteins, and perhaps most importantly the induction of an unfolded protein response (UPR) and endoplasmic reticulum (ER)-stress-induced apoptosis. To evaluate global protein dynamics in KMT2Ar ALL cells treated with bortezomib, we performed tandem mass tag (TMT) quantitative mass spectrometry on synchronized SEM cells exposed to either 50nM of bortezomib or DMSO at 0 hours (hr), 6hr, 12hr, 16hr, and 20hr. Applying pairwise comparison for 9232 unique proteins measured over the time course compared to untreated controls, we identified 1593 proteins with a log2 fold change >1.5 in bortezomib treated cells compared to 101 proteins in the DMSO control (FDR