Targeting FAcilitates Chromatin Transcription complex inhibits pleural mesothelioma and enhances immunotherapy

BACKGROUND

Diffuse pleural mesothelioma (DPM) is an aggressive therapy-resistant cancer with unique molecular features. Numerous agents have been tested, but clinically effective ones remain elusive. Herein, we propose to use a small molecule CBL0137 (curaxin) that simultaneously suppresses nuclear factor-κB (NF-κB) and activates tumor suppressor p53 via targeting FAcilitates Chromatin Transcription (FACT) complex, a histone chaperone critical for DNA repair.

METHODS

We used DPM cell lines, murine models (xeno- and allo-grafts), plus DPM patient samples to characterize anti-tumor effects of CBL0137 and to delineate specific molecular mechanisms.

RESULTS

We verified that CBL0137 induced cell cycle arrest and apoptosis. We also discovered that DPM is a FACT-dependent cancer with overexpression of both subunits structure-specific recognition protein 1 (SSRP1), a poor prognosis indicator, and suppressor of Ty 16 (SUPT16H). We defined several novel uses of CBL0137 in DPM therapy. In combination with cisplatin, CBL0137 exhibited additive anti-tumor activity compared to monotherapy. Similarly, CBL0137 (systemic) could be combined with other novel agents like microRNA-215 (intrapleural) as a more effective regimen. Importantly, we established that CBL0137 induces immunogenic cell death that contributes to activating immune response pathways in DPM. Therefore, when CBL0137 is combined with dual immune checkpoint inhibitors DPM tumor growth is significantly suppressed.

CONCLUSIONS

We identified an unrecognized molecular vulnerability of DPM based on FACT dependency. CBL0137 alone and in several combinations with different therapeutics showed promising efficacy, including that of improved anti-tumor immunity. Overall, these preclinical findings suggest that CBL0137 could be ideally suited for use in DPM clinical trials.

Z-DNA enhances immunotherapy by triggering death of inflammatory cancer-associated fibroblasts

Cancer-associated fibroblasts (CAFs) are a heterogeneous population of cells. At one end of the spectrum are alpha-smooth muscle actin expressing myoCAFs (myofibroblast CAFs) and at the other end are the interferon (IFN) and Janus Kinase/Signal Transducer and Activator of Transcription responsive iCAFs (inflammatory CAFs). Both types of CAFs promote tumor growth. While myoCAFs foster immune exclusion and limit tumor spread, iCAFs create a highly immunosuppressive environment and foster the seeding of distant metastases. However, iCAFs also represent a tumor vulnerability. They are competent to undergo necroptosis, a highly immunogenic form of cell death that is triggered when Z-DNA or Z-RNA (collectively called ZNA) is sensed by the IFN-induced ZNA binding protein 1 (ZBP1). The sequestering of ZNA ligands by the p150 isoform of the double-stranded RNA-specific deaminase ADAR1 protects iCAFs from cell death. ZBP1-dependent necroptosis in iCAFs can be triggered by administering an orally available small molecule that generates sufficient amounts of ZNA to bypass ADAR1 inhibition. The therapeutic approach of targeting Z-prone sequences (called flipons) is agnostic to the mutations driving cancer progression. By exploiting the tumor vulnerability posed by expression of ZBP1-dependent immunogenic cell death pathways in iCAFs, flipon therapeutics offer new hope for improved clinical outcomes.

TP53 loss‑of‑function mutations reduce sensitivity of acute leukaemia to the curaxin CBL0137

The presence of a TP53 mutation is a predictor of poor outcome in leukaemia, and efficacious targeted therapies for these patients are lacking. The curaxin CBL0137 has demonstrated promising antitumour activities in multiple cancers such as glioblastoma, acting through p53 activation, NF‑κB inhibition and chromatin remodelling. In the present study, it was revealed using Annexin‑V/7‑AAD apoptosis assays that CBL0137 has efficacy across several human acute leukaemia cell lines with wild‑type TP53, but sensitivity is reduced in TP53‑mutated subtypes. A heterozygous TP53 loss‑of‑function mutation in the KMT2A‑AFF1 human RS4;11 cell line was generated, and it was demonstrated that heterozygous TP53 loss‑of‑function is sufficient to cause a significant reduction in CBL0137 sensitivity. To the best of our knowledge, this is the first evidence to suggest a clinically significant role for functional p53 in the efficacy of CBL0137 in acute leukaemia. Future CBL0137 clinical trials should include TP53 mutation screening, to establish the clinical relevance of TP53 mutations in CBL0137 efficacy.

MYC overexpression leads to increased chromatin interactions at superenhancers and MYC binding sites

The MYC oncogene encodes for the MYC protein and is frequently dysregulated across multiple cancer cell types, making it an attractive target for cancer therapy. MYC overexpression leads to MYC binding at active enhancers, resulting in a global transcriptional amplification of active genes. Because super-enhancers are frequently dysregulated in cancer, we hypothesized that MYC preferentially invades into super-enhancers and alters the cancer genome organization. To that end, we performed ChIP-seq, RNA-seq, circular chromosome conformation capture (4C-seq), and Spike-in Quantitative Hi-C (SIQHiC) on the U2OS osteosarcoma cell line with tetracycline-inducible MYC. MYC overexpression in U2OS cells modulated histone acetylation and increased MYC binding at super-enhancers. SIQHiC analysis revealed increased global chromatin contact frequency, particularly at chromatin interactions connecting MYC binding sites at promoters and enhancers. Immunofluorescence staining showed that MYC molecules formed punctate foci at these transcriptionally active domains after MYC overexpression. These results demonstrate the accumulation of overexpressed MYC at promoter–enhancer hubs and suggest that MYC invades into enhancers through spatial proximity. At the same time, the increased protein–protein interactions may strengthen these chromatin interactions to increase chromatin contact frequency. CTCF siRNA knockdown in MYC-overexpressed U2OS cells demonstrated that removal of architectural proteins can disperse MYC and abrogate the increase in chromatin contacts. By elucidating the chromatin landscape of MYC-driven cancers, we can potentially target MYC-associated chromatin interactions for cancer therapy.

Therapeutic Targets in Diffuse Midline Gliomas-An Emerging Landscape

Simple Summary

Diffuse midline gliomas (DMGs) remain one of the most devastating childhood brain tumour types, for which there is currently no known cure. In this review we provide a summary of the existing knowledge of the molecular mechanisms underlying the pathogenesis of this disease, highlighting current analyses and novel treatment propositions. Together, the accumulation of these data will aid in the understanding and development of more effective therapeutic options for the treatment of DMGs.

Abstract

Diffuse midline gliomas (DMGs) are invariably fatal pediatric brain tumours that are inherently resistant to conventional therapy. In recent years our understanding of the underlying molecular mechanisms of DMG tumorigenicity has resulted in the identification of novel targets and the development of a range of potential therapies, with multiple agents now being progressed to clinical translation to test their therapeutic efficacy. Here, we provide an overview of the current therapies aimed at epigenetic and mutational drivers, cellular pathway aberrations and tumor microenvironment mechanisms in DMGs in order to aid therapy development and facilitate a holistic approach to patient treatment.

Kidney cancer biomarkers and targets for therapeutics: survivin (BIRC5), XIAP, MCL-1, HIF1α, HIF2α, NRF2, MDM2, MDM4, p53, KRAS and AKT in renal cell carcinoma

The incidence of renal cell carcinoma (RCC) is increasing worldwide with an approximate 20% mortality rate. The challenge in RCC is the therapy-resistance. Cancer resistance to treatment employs multiple mechanisms due to cancer heterogeneity with multiple genetic and epigenetic alterations. These changes include aberrant overexpression of (1) anticancer cell death proteins (e.g., survivin/BIRC5), (2) DNA repair regulators (e.g., ERCC6) and (3) efflux pump proteins (e.g., ABCG2/BCRP); mutations and/or deregulation of key (4) oncogenes (e.g., MDM2, KRAS) and/or (5) tumor suppressor genes (e.g., TP5/p53); and (6) deregulation of redox-sensitive regulators (e.g., HIF, NRF2). Foci of tumor cells that have these genetic alterations and/or deregulation possess survival advantages and are selected for survival during treatment. We will review the significance of survivin (BIRC5), XIAP, MCL-1, HIF1α, HIF2α, NRF2, MDM2, MDM4, TP5/p53, KRAS and AKT in treatment resistance as the potential therapeutic biomarkers and/or targets in RCC in parallel with our analized RCC-relevant TCGA genetic results from each of these gene/protein molecules. We then present our data to show the anticancer drug FL118 modulation of these protein targets and RCC cell/tumor growth. Finally, we include additional data to show a promising FL118 analogue (FL496) for treating the specialized type 2 papillary RCC.