Anti-leukemia activity of NSC-743380 in SULT1A1-expressing acute myeloid leukemia cells is associated with inhibitions of cFLIP expression and PI3K/AKT/mTOR activities

Epstein Barr virus-positive B-cell lymphoma is highly vulnerable to MDM2 inhibitors in vivo

MDM2 inhibitors have potent in vivo activity against and could be a novel therapy for EBV-positive B-cell lymphoma.

EBV positivity or loss of BCL6 expression can be a potential predictive biomarker for response to MDM2 inhibitors in patients with lymphoma

Epstein-Barr virus–positive (EBV-positive) B-cell lymphomas are common in immunocompromised patients and remain an unmet medical need. Here we report that MDM2 inhibitors (MDM2is) navtemadlin and idasanutlin have potent in vivo activity in EBV-positive B-cell lymphoma established in immunocompromised mice. Tumor regression was observed in all 5 EBV-positive xenograft–associated B-cell lymphomas treated with navtemadlin or idasanutlin. Molecular characterization showed that treatment with MDM2is resulted in activation of p53 pathways and downregulation of cell cycle effectors in human lymphoma cell lines that were either EBV-positive or had undetectable expression of BCL6, a transcriptional inhibitor of the TP53 gene. Moreover, treatment with navtemadlin resulted in tumor regression and prevented systemic dissemination of EBV-positive lymphoma derived from 2 juvenile patients with posttransplant lymphoproliferative diseases, including 1 whose tumor was resistant to virus-specific T-cell therapy. These results provide proof-of-concept for targeted therapy of EBV-positive lymphoma with MDM2is and the feasibility of using EBV infection or loss of BCL6 expression to identify responders to MDM2is.

Current Methods of Post-Translational Modification Analysis and Their Applications in Blood Cancers

Post-translational modifications (PTMs) add a layer of complexity to the proteome through the addition of biochemical moieties to specific residues of proteins, altering their structure, function and/or localization. Mass spectrometry (MS)-based techniques are at the forefront of PTM analysis due to their ability to detect large numbers of modified proteins with a high level of sensitivity and specificity. The low stoichiometry of modified peptides means fractionation and enrichment techniques are often performed prior to MS to improve detection yields. Immuno-based techniques remain popular, with improvements in the quality of commercially available modification-specific antibodies facilitating the detection of modified proteins with high affinity. PTM-focused studies on blood cancers have provided information on altered cellular processes, including cell signaling, apoptosis and transcriptional regulation, that contribute to the malignant phenotype. Furthermore, the mechanism of action of many blood cancer therapies, such as kinase inhibitors, involves inhibiting or modulating protein modifications. Continued optimization of protocols and techniques for PTM analysis in blood cancer will undoubtedly lead to novel insights into mechanisms of malignant transformation, proliferation, and survival, in addition to the identification of novel biomarkers and therapeutic targets. This review discusses techniques used for PTM analysis and their applications in blood cancer research.

KRT-232 and navitoclax enhance trametinib's anti-Cancer activity in non-small cell lung cancer patient-derived xenografts with KRAS mutations

Activating mutations of the KRAS gene are one of the major genomic alterations associated with tumorigenesis of non-small cell lung cancer (NSCLC). Thus far, treatment of KRAS-mutant NSCLC remains an unmet medical need. We determined the in vivo treatment responses of 13 KRAS mutant and 14 KRAS wild type NSCLC patient-derived xenografts (PDXs) to agents that target known NSCLC vulnerabilities: the MEK inhibitor trametinib, the MDM2 inhibitor KRT-232, and the BCL-X_L/BCL-2 inhibitor navitoclax. The results showed that the tumor regression rate after single agent therapy with KRT-232, trametinib and navitoclax was 11%, 10% and 0%, respectively. Combination therapies of trametinib plus KRT-232 and trametinib plus navitoclax led to improved partial response rates over single-agent activity in a subset of PDX models. Tumor regression was observed in 23% and 50% of PDXs after treatment with trametinib plus KRT-232 and trametinib plus navitoclax, respectively. The disease control rates in KRAS-mutant PDXs tested were 90%-100% after treatment with trametinib plus KRT-232 or plus navitoclax. A correlation analysis of treatment responses and genomic and proteomic biomarkers revealed that sensitivity to KRT-232 was significantly associated with TP53 wild-type or STK11 mutant genotypes (P<0.05). The levels of several proteins, including GSK3b, Nrf2, LKB1/pS334, and SMYD3, were significantly associated with sensitivity to trametinib plus navitoclax. Thus, the combination of trametinib plus KRT-232 or navitoclax resulted in improved efficacy compared with the agents alone in a subgroup of NSCLC PDX model with KRAS mutations. Expanded clinical trials of these targeted drug combinations in NSCLC are warranted.