A pilot clinical trial of oral tetrahydrouridine/decitabine for noncytotoxic epigenetic therapy of chemoresistant lymphoid malignancies

Neuroendocrine lineage commitment of small cell lung cancers can be leveraged into p53-independent non-cytotoxic therapy

Small cell lung cancers (SCLCs) rapidly resist cytotoxic chemotherapy and immune checkpoint inhibitor (ICI) treatments. New, non-cross-resistant therapies are thus needed. SCLC cells are committed into neuroendocrine lineage then maturation arrested. Implicating DNA methyltransferase 1 (DNMT1) in the maturation arrests, we find (1) the repression mark methylated CpG, written by DNMT1, is retained at suppressed neuroendocrine-lineage genes, even as other repression marks are erased; (2) DNMT1 is recurrently amplified, whereas Ten-Eleven-Translocation 2 (TET2), which functionally opposes DNMT1, is deleted; (3) DNMT1 is recruited into neuroendocrine-lineage master transcription factor (ASCL1, NEUROD1) hubs in SCLC cells; and (4) DNMT1 knockdown activated ASCL1-target genes and released SCLC cell-cycling exits by terminal lineage maturation, which are cycling exits that do not require the p53/apoptosis pathway used by cytotoxic chemotherapy. Inhibiting DNMT1/corepressors with clinical compounds accordingly extended survival of mice with chemorefractory and ICI-refractory, p53-null, disseminated SCLC. Lineage commitment of SCLC cells can hence be leveraged into non-cytotoxic therapy able to treat chemo/ICI-refractory SCLC.

Epigenetic targets in B- and T-cell lymphomas: latest developments

Non-Hodgkin's lymphomas (NHLs) comprise a diverse group of diseases, either of mature B-cell or of T-cell derivation, characterized by heterogeneous molecular features and clinical manifestations. While most of the patients are responsive to standard chemotherapy, immunotherapy, radiation and/or stem cell transplantation, relapsed and/or refractory cases still have a dismal outcome. Deep sequencing analysis have pointed out that epigenetic dysregulations, including mutations in epigenetic enzymes, such as chromatin modifiers and DNA methyltransferases (DNMTs), are prevalent in both B- cell and T-cell lymphomas. Accordingly, over the past decade, a large number of epigenetic-modifying agents have been developed and introduced into the clinical management of these entities, and a few specific inhibitors have already been approved for clinical use. Here we summarize the main epigenetic alterations described in B- and T-NHL, that further supported the clinical development of a selected set of epidrugs in determined diseases, including inhibitors of DNMTs, histone deacetylases (HDACs), and extra-terminal domain proteins (bromodomain and extra-terminal motif; BETs). Finally, we highlight the most promising future directions of research in this area, explaining how bioinformatics approaches can help to identify new epigenetic targets in B- and T-cell lymphoid neoplasms.

Ascertaining QUAZARs: slow-motion and light-speed development of oral azacitidine and decitabine

Myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) are devastating diseases that frequently rely on the use of parenteral hypomethylating agents (HMAs), either as monotherapy or in combination, as first-line treatment for many patients. Two new oral HMAs, decitabine/cedazuridine (DC) for use in place of azacitidine or decitabine in MDS, and azacitidine (CC-486) for use as maintenance treatment in AML, were recently approved by the FDA. We will discuss the development of these oral HMAs, including the advantages/disadvantages in transitioning to oral HMAs and an in depth look at the pivotal phase III trials that led to their FDA approval - ASCERTAIN for DC and QUAZAR-AML-001 for CC-486. We also review how these agents have been and are being studied in other malignancies, and examine the future role that these exciting novel agents will play in both MDS and AML.

Changing paradigms in oncology: Toward noncytotoxic treatments for advanced gliomas

Glial-lineage malignancies (gliomas) recurrently mutate and/or delete the master regulators of apoptosis p53 and/or p16/CDKN2A, undermining apoptosis-intending (cytotoxic) treatments. By contrast to disrupted p53/p16, glioma cells are live-wired with the master transcription factor circuits that specify and drive glial lineage fates: these transcription factors activate early-glial and replication programs as expected, but fail in their other usual function of forcing onward glial lineage-maturation-late-glial genes have constitutively "closed" chromatin requiring chromatin-remodeling for activation-glioma-genesis disrupts several epigenetic components needed to perform this work, and simultaneously amplifies repressing epigenetic machinery instead. Pharmacologic inhibition of repressing epigenetic enzymes thus allows activation of late-glial genes and terminates glioma self-replication (self-replication = replication without lineage-maturation), independent of p53/p16/apoptosis. Lineage-specifying master transcription factors therefore contrast with p53/p16 in being enriched in self-replicating glioma cells, reveal a cause-effect relationship between aberrant epigenetic repression of late-lineage programs and malignant self-replication, and point to specific epigenetic targets for noncytotoxic glioma-therapy.

Cancer Evo-Dev: A Theory of Inflammation-Induced Oncogenesis

Chronic inflammation is a prerequisite for the development of cancers. Here, we present the framework of a novel theory termed as Cancer Evolution-Development (Cancer Evo-Dev) based on the current understanding of inflammation-related carcinogenesis, especially hepatocarcinogenesis induced by chronic infection with hepatitis B virus. The interaction between genetic predispositions and environmental exposures, such as viral infection, maintains chronic non-resolving inflammation. Pollution, metabolic syndrome, physical inactivity, ageing, and adverse psychosocial exposure also increase the risk of cancer via inducing chronic low-grade smoldering inflammation. Under the microenvironment of non-resolving inflammation, pro-inflammatory factors facilitate the generation of somatic mutations and viral mutations by inducing the imbalance between the mutagenic forces such as cytidine deaminases and mutation-correcting forces including uracil-DNA glycosylase. Most cells with somatic mutations and mutated viruses are eliminated in survival competition. Only a small percentage of mutated cells survive, adapt to the hostile environment, retro-differentiate, and function as cancer-initiating cells via altering signaling pathways. These cancer-initiating cells acquire stem-ness, reprogram metabolic patterns, and affect the microenvironment. The carcinogenic process follows the law of "mutation-selection-adaptation". Chronic physical activity reduces the levels of inflammation via upregulating the activity and numbers of NK cells and lymphocytes and lengthening leukocyte telomere; downregulating proinflammatory cytokines including interleukin-6 and senescent lymphocytes especially in aged population. Anti-inflammation medication reduces the occurrence and recurrence of cancers. Targeting cancer stemness signaling pathways might lead to cancer eradication. Cancer Evo-Dev not only helps understand the mechanisms by which inflammation promotes the development of cancers, but also lays the foundation for effective prophylaxis and targeted therapy of various cancers.

Clinical Trials Assessing Hypomethylating Agents Combined with Other Therapies: Causes for Failure and Potential Solutions

PURPOSE

Azacitidine and decitabine are hypomethylating agents (HMA), that is, both inhibit and deplete DNA methyltransferase 1 (DNMT1). HMAs are standard single-agent therapies for myelodysplastic syndromes and acute myelogenous leukemias. Several attempts to improve outcomes by combining HMAs with investigational agents, excepting with the BCL2-inhibitor venetoclax, have failed in randomized clinical trial (RCT) evaluations. We extract lessons from decades of clinical trials to thereby inform future work.

EXPERIMENTAL DESIGN

Serial single-agent clinical trials were analyzed for mechanism and pathway properties of HMAs underpinning their success, and for rules for dose and schedule selection. RCTs were studied for principles, dos and don'ts for productive combination therapy.

RESULTS

Single-agent HMA trial results encourage dose and schedule selection to increase S-phase-dependent DNMT1 targeting, and discourage doses that cause indiscriminate antimetabolite effects/cytotoxicity, because these attrit myelopoiesis reserves needed for clinical response. Treatment-related myelosuppression should prompt dose/frequency reductions of less active investigational agents rather than more active HMA. Administering cytostatic agents concurrently with HMA can antagonize S-phase-dependent DNMT1 targeting. Supportive care that enables on-time administration of S-phase (exposure-time)-dependent HMA could be useful. Agents that manipulate pyrimidine metabolism to increase HMA pro-drug processing into DNMT1-depleting nucleotide, and/or inhibit other epigenetic enzymes implicated in oncogenic silencing of lineage differentiation, could be productive, but doses and schedules should adhere to therapeutic index/molecular-targeted principles already learned.

CONCLUSIONS

More than 40 years of clinical trial history indicates mechanism, pathway, and therapeutic index properties of HMAs that underpin their almost exclusive success and teaches lessons for selection and design of combinations aiming to build on this treatment foundation.