Apoptotic priming in senescence predicts specific senolysis by quantitative analysis of mitochondrial dependencies.

Cellular senescence contributes to a variety of pathologies associated with aging and is implicated as a cellular state in which cancer cells can survive treatment. Reported senolytic drug treatments act through varying molecular mechanisms, but heterogeneous efficacy across the diverse contexts of cellular senescence indicates a need for predictive biomarkers of senolytic activity. Using multi-parametric analyses of commonly reported molecular features of the senescent phenotype, we assayed a variety of models, including malignant and nonmalignant cells, using several triggers of senescence induction and found little univariate predictive power of these traditional senescence markers to identify senolytic drug sensitivity.

Senolysis by ABT-263 is associated with inherent apoptotic dependence of cancer cells derived from the non-senescent state.

Cellular senescence is a stress response that cells can employ to resist cell death. Senescent cells rely on anti-apoptotic signaling for their survival, which can be targeted by senolytic agents, like the BCL-XL, BCL-2, BCL-W inhibitor ABT-263. However, the response to ABT-263 of senescent cancer cells ranges from highly sensitive to refractory.

Conventional chemotherapy: millions of cures, unresolved therapeutic index.

In recent decades, millions of patients with cancer have been cured by chemotherapy alone. By 'cure', we mean that patients with cancers that would be fatal if left untreated receive a time-limited course of chemotherapy and their cancer disappears, never to return. In an era when hundreds of thousands of cancer genomes have been sequenced, a remarkable fact persists: in most patients who have been cured, we still do not fully understand the mechanisms underlying the therapeutic index by which the tumour cells are killed, but normal cells are somehow spared.

Comparative analysis of Bcl-2 family protein overexpression in CAR T cells alone and in combination with BH3 mimetics.

Approximately 50% of patients with hematologic malignancies relapse after chimeric antigen receptor (CAR) T cell treatment; mechanisms of failure include loss of CAR T persistence and tumor resistance to apoptosis. We hypothesized that both of these challenges could potentially be overcome by overexpressing one or more of the Bcl-2 family proteins in CAR T cells to reduce their susceptibility to apoptosis, both alone and in the presence of BH3 mimetics, which can be used to activate apoptotic machinery in malignant cells. We comprehensively investigated overexpression of different Bcl-2 family proteins in CAR T cells with different signaling domains as well as in different tumor types.

The Siren Song of Synergy.

In ancient Greek mythology, sirens were creatures of stunning beauty whose mystical songs led sailors to sail their boats onto hidden rocks and into total destruction. In this issue, Mason-Osann and colleagues present data in the context of acute myelogenous leukemia to suggest that while synergy may show initial attractions in drug combinations, it may carry with it hazards previously unforeseen. See related article by Mason-Osann et al.

Prophylactic maintenance with venetoclax/azacitidine after reduced-intensity conditioning allogeneic transplant for high-risk MDS and AML.

We conducted a phase 1 trial assessing safety and efficacy of prophylactic maintenance therapy with venetoclax and azacitidine (Ven/Aza) for patients with high-risk myelodysplastic syndromes (MDS)/acute myeloid leukemia (AML) undergoing reduced intensity allogeneic stem cell transplantation (allo-SCT) after Ven and fludarabine/busulfan conditioning (Ven/FluBu2 allo-SCT) with tacrolimus and methotrexate as graft-versus-host disease (GVHD) prophylaxis. Among 27 patients who underwent Ven/FluBu2 allo-SCT (55.6% with prior Ven exposure, and 96% with positive molecular measurable residual disease), 22 received maintenance therapy with Aza 36 mg/m2 intravenously on days 1 to 5, and Ven 400 mg by mouth on days 1 to 14 per assigned dose schedule/level (42-day cycles × 8, or 28-day cycles × 12).

Heterogeneity and transcriptional drivers of triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is a heterogeneous disease with limited treatment options. To characterize TNBC heterogeneity, we defined transcriptional, epigenetic, and metabolic subtypes and subtype-driving super-enhancers and transcription factors by combining functional and molecular profiling with computational analyses. Single-cell RNA sequencing revealed relative homogeneity of the major transcriptional subtypes (luminal, basal, and mesenchymal) within samples.

Targeting conditioned media dependencies and FLT-3 in chronic lymphocytic leukemia.

The importance of the stromal microenvironment in chronic lymphocytic leukemia (CLL) pathogenesis and drug resistance is well established. Despite recent advances in CLL therapy, identifying novel ways to disrupt interactions between CLL and its microenvironment may identify new combination partners for the drugs currently in use. To understand the role of microenvironmental factors on primary CLL cells, we took advantage of an observation that conditioned media (CM) collected from stroma was protective of CLL cells from spontaneous cell death ex vivo.

Sequential apoptotic and multiplexed proteomic evaluation of single cancer cells.

A potential cause of cancer relapse is pretreatment chemoresistant subpopulations. Identifying targetable features of subpopulations that are poorly primed for therapy-induced cell death may improve cancer therapy. Here, we develop and validate real-time BH3 profiling, a live and functional single-cell measurement of pretreatment apoptotic sensitivity that occurs upstream of apoptotic protease activation.

Dynamic BH3 profiling identifies pro-apoptotic drug combinations for the treatment of malignant pleural mesothelioma.

Malignant pleural mesothelioma (MPM) has relatively ineffective first/second-line therapy for advanced disease and only 18% five-year survival for early disease. Drug-induced mitochondrial priming measured by dynamic BH3 profiling identifies efficacious drugs in multiple disease settings. We use high throughput dynamic BH3 profiling (HTDBP) to identify drug combinations that prime primary MPM cells derived from patient tumors, which also prime patient derived xenograft (PDX) models.

Quantifying requirements for mitochondrial apoptosis in CAR T killing of cancer cells.

Chimeric antigen receptor (CAR) T cell therapy is an FDA-approved treatment for several hematologic malignancies, yet not all patients respond to this treatment. While some resistance mechanisms have been identified, cell death pathways in target cancer cells remain underexplored. Impairing mitochondrial apoptosis via knockout of Bak and Bax, forced Bcl-2 and Bcl-XL expression, or caspase inhibition protected several tumor models from CAR T killing.

Collateral deletion of the mitochondrial AAA+ ATPase ATAD1 sensitizes cancer cells to proteasome dysfunction.

The tumor suppressor gene is the second most commonly deleted gene in cancer. Such deletions often include portions of the chromosome 10q23 locus beyond the bounds of itself, which frequently disrupts adjacent genes. Coincidental loss of -adjacent genes might impose vulnerabilities that could either affect patient outcome basally or be exploited therapeutically.

Lisaftoclax (APG-2575) Is a Novel BCL-2 Inhibitor with Robust Antitumor Activity in Preclinical Models of Hematologic Malignancy.

Purpose: Development of B-cell lymphoma 2 (BCL-2)-specific inhibitors poses unique challenges in drug design because of BCL-2 homology domain 3 (BH3) shared homology between BCL-2 family members and the shallow surface of their protein-protein interactions. We report herein discovery and extensive preclinical investigation of lisaftoclax (APG-2575).

Experimental Design: Computational modeling was used to design "lead" compounds.

Precision medicine in AML: Function plus -omics is better than either alone.

Morphology, immunophenotype, cytogenetics, and genomics have long dominated diagnostics in acute myelogenous leukemia (AML). In this issue of Cancer Cell, Bottomly et al. demonstrate that combining the above with transcriptomics and ex vivo drug testing of patient myeloblasts yields novel diagnostic and therapeutic insights with the potential for clinical translation.

IKAROS and MENIN coordinate therapeutically actionable leukemogenic gene expression in MLL-r acute myeloid leukemia.

Acute myeloid leukemia (AML) remains difficult to treat and requires new therapeutic approaches. Potent inhibitors of the chromatin-associated protein MENIN have recently entered human clinical trials, opening new therapeutic opportunities for some genetic subtypes of this disease. Using genome-scale functional genetic screens, we identified IKAROS (encoded by IKZF1) as an essential transcription factor in KMT2A (MLL1)-rearranged (MLL-r) AML that maintains leukemogenic gene expression while also repressing pathways for tumor suppression, immune regulation and cellular differentiation.

Augmenting NK cell-based immunotherapy by targeting mitochondrial apoptosis.

Interest in harnessing natural killer (NK) cells for cancer immunotherapy is rapidly growing. However, efficacy of NK cell-based immunotherapy remains limited in most trials. Strategies to augment the killing efficacy of NK cells are thus much needed.

JAK3 mutations and mitochondrial apoptosis resistance in T-cell acute lymphoblastic leukemia.

Resistance to mitochondrial apoptosis predicts inferior treatment outcomes in patients with diverse tumor types, including T-cell acute lymphoblastic leukemia (T-ALL). However, the genetic basis for variability in this mitochondrial apoptotic phenotype is poorly understood, preventing its rational therapeutic targeting. Using BH3 profiling and exon sequencing analysis of childhood T-ALL clinical specimens, we found that mitochondrial apoptosis resistance was most strongly associated with activating mutations of JAK3.

Preclinical Modeling of Leiomyosarcoma Identifies Susceptibility to Transcriptional CDK Inhibitors through Antagonism of E2F-Driven Oncogenic Gene Expression.

Purpose: Leiomyosarcoma (LMS) is a neoplasm characterized by smooth muscle differentiation, complex copy-number alterations, tumor suppressor loss, and the absence of recurrent driver mutations. Clinical management for advanced disease relies on the use of empiric cytotoxic chemotherapy with limited activity, and novel targeted therapies supported by preclinical research on LMS biology are urgently needed. A lack of fidelity of established LMS cell lines to their mesenchymal neoplasm of origin has limited translational understanding of this disease, and few other preclinical models have been established.