Tumor-informed ctDNA assessment as a valuable prognostic and predictive biomarker in diffuse large B-cell lymphoma.

Background: A novel approach for molecular residual disease (MRD) detection and treatment monitoring is needed in diffuse large B-cell lymphoma (DLBCL) to identify patients with a poor prognosis. We performed a retrospective evaluation of commercial ctDNA testing in patients with stage I-IV DLBCL to evaluate the prognostic and predictive role of tumor-informed ctDNA assessment. Methods: A personalized and tumor-informed multiplex PCR assay (Signatera™ bespoke mPCR NGS assay) was used for ctDNA detection and quantification. Results: In total, 50 patients (median age: 59 years; median follow-up: 12.68 months) were analyzed, of which 41 had pretreatment time points with ctDNA detected in 95% (39/41). Baseline ctDNA levels correlated with R-IPI scores and stage. ctDNA clearance during first-line therapy was predictive of improved therapy responses and outcomes (EFS, HR: 6.5, 95% CI: 1.9-22, p=0.003 and OS, HR: 22, 95% CI: 2.5-191, p=0.005). Furthermore, 48% (13/27) of patients cleared their ctDNA following the first cycle of treatment. Patients who cleared their ctDNA, irrespective of their R-IPI score, had superior outcomes compared to ctDNA-positive patients. ctDNA clearance outperformed other factors associated with EFS in multivariate analysis (HR: 49.76, 95% CI:1.1-2225.6, p=0.044). Finally, ctDNA clearance predicted complete response (CR)/no evidence of disease (NED) on average 97 days (range: 0-14.7 months) ahead of imaging/biopsy. Conclusion: ctDNA testing in patients with DLBCL is predictive of patient outcomes and may enable personalized surveillance, intervention, and/or trial options.

l-2-Hydroxyglutarate remodeling of the epigenome and epitranscriptome creates a metabolic vulnerability in kidney cancer models.

Tumor cells are known to undergo considerable metabolic reprogramming to meet their unique demands and drive tumor growth. At the same time, this reprogramming may come at a cost with resultant metabolic vulnerabilities. The small molecule l-2-hydroxyglutarate (l-2HG) is elevated in the most common histology of renal cancer. Similarly to other oncometabolites, l-2HG has the potential to profoundly impact gene expression. Here, we demonstrate that l-2HG remodels amino acid metabolism in renal cancer cells through combined effects on histone methylation and RNA N6-methyladenosine. The combined effects of l-2HG result in a metabolic liability that renders tumors cells reliant on exogenous serine to support proliferation, redox homeostasis, and tumor growth. In concert with these data, high-l-2HG kidney cancers demonstrate reduced expression of multiple serine biosynthetic enzymes. Collectively, our data indicate that high-l-2HG renal tumors could be specifically targeted by strategies that limit serine availability to tumors.

The multiple mechanisms of MCL1 in the regulation of cell fate.

MCL1 (myeloid cell leukemia-1) is a widely recognized pro-survival member of the Bcl-2 (B-cell lymphoma protein 2) family and a promising target for cancer therapy. While the role MCL1 plays in apoptosis is well defined, its participation in emerging non-apoptotic signaling pathways is only beginning to be appreciated. Here, we synthesize studies characterizing MCL1s influence on cell proliferation, DNA damage response, autophagy, calcium handling, and mitochondrial quality control to highlight the broader scope that MCL1 plays in cellular homeostasis regulation. Throughout this review, we discuss which pathways are likely to be impacted by emerging MCL1 inhibitors, as well as highlight non-cancerous disease states that could deploy Bcl-2 homology 3 (BH3)-mimetics in the future.

MCL1 binds and negatively regulates the transcriptional function of tumor suppressor p73.

MCL1, an anti-apoptotic protein that controls chemosensitivity and cell fate through its regulation of intrinsic apoptosis, has been identified as a high-impact target in anti-cancer therapeutic development. With MCL1-specific inhibitors currently in clinical trials, it is imperative that we understand the roles that MCL1 plays in cells, especially when targeting the Bcl-2 homology 3 (BH3) pocket, the central region of MCL1 that mediates apoptotic regulation. Here, we establish that MCL1 has a direct role in controlling p73 transcriptional activity, which modulates target genes associated with DNA damage response, apoptosis, and cell cycle progression. This interaction is mediated through the reverse BH3 (rBH3) motif in the p73 tetramerization domain, which restricts p73 assembly on DNA. Here, we provide a novel mechanism for protein-level regulation of p73 transcriptional activity by MCL1, while also framing a foundation for studying MCL1 inhibitors in combination with platinum-based chemotherapeutics. More broadly, this work expands the role of Bcl-2 family signaling beyond cell fate regulation.

A cell-penetrating MARCKS mimetic selectively triggers cytolytic death in glioblastoma.

Glioblastoma (GBM) is an aggressive malignancy with limited effectiveness of standard of care therapies including surgery, radiation, and temozolomide chemotherapy necessitating novel therapeutics. Unfortunately, GBMs also harbor several signaling alterations that protect them from traditional therapies that rely on apoptotic programmed cell death. Because almost all GBM tumors have dysregulated phosphoinositide signaling as part of that process, we hypothesized that peptide mimetics derived from the phospholipid binding domain of Myristoylated alanine-rich C-kinase substrate (MARCKS) could serve as a novel GBM therapeutic. Using molecularly classified patient-derived xenograft (PDX) lines, cultured in stem-cell conditions, we demonstrate that cell permeable MARCKS effector domain (ED) peptides potently target all GBM molecular classes while sparing normal human astrocytes. Cell death mechanistic testing revealed that these peptides produce rapid cytotoxicity in GBM that overcomes caspase inhibition. Moreover, we identify a GBM-selective cytolytic death mechanism involving plasma membrane targeting and intracellular calcium accumulation. Despite limited relative partitioning to the brain, tail-vein peptide injection revealed tumor targeting in intracranially implanted GBM PDX. These results indicate that MARCKS ED peptide therapeutics may overcome traditional GBM resistance mechanisms, supporting further development of similar agents.