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Key Points Therapy-related myeloid neoplasms (t-MN) arise as a late effect of chemotherapy and/or radiation administered for a primary condition, often a malignant disease, solid organ transplant or autoimmune disease. The majority of t-MN have high-risk cytogenetic features, and the prognosis for patients with t-MN is poor, with a 5-year survival of 10%. Germline mutations in genes associated with an inherited predisposition to cancer have been identified in approximately 20% of patients with t-MN. Chemotherapy and/or radiotherapy promotes clonal selection of pre-existing, mutant haematopoietic stem cells in addition to directly inducing leukaemogenic mutations. The somatic mutations in t-MN are indistinguishable from those occurring in de novo acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS). Large chromosomal deletions, such as del(5q) and del(7q), that occur in t-MN do not harbour a single, recessive tumour suppressor gene but instead are part of a contiguous gene syndrome (CGS). Moreover, the genes involved in CGSs on these chromosomes act by haploinsufficiency. An aberrant bone marrow microenvironment directly contributes to the pathogenesis of t-MN. Therapy-related myeloid neoplasms occur as a late complication following chemotherapy and/or radiotherapy administered for a primary condition. In this Review, McNerney et al . discuss recent studies that have improved our understanding of the aetiology of this disease. Therapy-related myeloid neoplasms (t-MN) arise as a late effect of chemotherapy and/or radiation administered for a primary condition, typically a malignant disease, solid organ transplant or autoimmune disease. Survival is measured in months, not years, making t-MN one of the most aggressive and lethal cancers. In this Review, we discuss recent developments that reframe our understanding of the genetic and environmental aetiology of t-MN. Emerging data are illuminating who is at highest risk of developing t-MN, why t-MN are chemoresistant and how we may use this information to treat and ultimately prevent this lethal disease.

-7/del(7q) is prevalent across subtypes of myeloid neoplasms. CUX1 , located on 7q22, encodes a homeodomain-containing transcription factor, and, like -7/del(7q), CUX1 inactivating mutations independently carry a poor prognosis. As with loss of 7q, CUX1 mutations often occur early in disease pathogenesis. We reported that CUX1 deficiency causes myelodysplastic syndrome in mice but was insufficient to drive acute myeloid leukemia (AML). Given the known association between -7/del(7q) and RAS pathway mutations, we mined cancer genome databases and explicitly linked CUX1 mutations with oncogenic RAS mutations. To determine if activated RAS and CUX1 deficiency promote leukemogenesis, we generated mice bearing Nras G12D and CUX1-knockdown which developed AML, not seen in mice with either mutation alone. Oncogenic RAS imparts increased self-renewal on CUX1-deficient hematopoietic stem/progenitor cells (HSPCs). Reciprocally, CUX1 knockdown amplifies RAS signaling through reduction of negative regulators of RAS/PI3K signaling. Double mutant HSPCs were responsive to PIK3 or MEK inhibition. Similarly, low expression of CUX1 in primary AML samples correlates with sensitivity to the same inhibitors, suggesting a potential therapy for malignancies with CUX1 inactivation. This work demonstrates an unexpected convergence of an oncogene and tumor suppressor gene on the same pathway.

Quantitative genetic epistasis has been hypothesized to be an important factor in the development and progression of complex diseases. Cancers in particular are driven by the accumulation of mutations that may act epistatically during the course of the disease. However, as cancer mutations are uncovered at an unprecedented rate, determining which combinations of genetic alterations interact to produce cancer phenotypes remains a challenge. Here we show that by using combinatorial RNAi screening in cell culture, dense and often previously undetermined interactions among cancer genes were revealed by assessing gene pairs that are frequently co-altered in primary breast cancers. These interacting gene pairs are significantly associated with survival time when co-altered in patients, indicating that genetic interaction mapping may be leveraged to improve risk assessment. As many of these interacting gene pairs involve known drug targets, personalized treatment regimens may be improved by overlaying genetic interactions with mutational profiling. Cancer can result from mutations in more than one gene and these multiple mutated genes are often functionally dependent on each other; this interaction is known as epistasis. Here, the authors use a combinatorial RNAi screen to identify epistatic genes that are mutated in breast cancer and reveal large numbers of previously unreported gene interactions.

The RNA N6-methyladenosine (m6A) reader YTHDF1 is implicated in cancer etiology and progression. We discovered that radiotherapy (RT) increased YTHDF1 expression in dendritic cells (DCs) of PBMCs from patients with cancer, but not in other immune cells tested. Elevated YTHDF1 expression in DCs was associated with poor outcomes for patients receiving RT. We found that loss of Ythdf1 in DCs enhanced the antitumor effects of ionizing radiation (IR) by increasing the cross-priming capacity of DCs across multiple murine cancer models. Mechanistically, IR upregulated YTHDF1 expression in DCs through stimulator of IFN genes/type I IFN (STING/IFN-I) signaling. YTHDF1 in turn triggered STING degradation by increasing lysosomal cathepsins, thereby reducing IFN-I production. We created a YTHDF1 deletion/inhibition prototype DC vaccine that significantly improved the therapeutic effect of RT and radioimmunotherapy in a murine melanoma model. Our findings reveal a layer of regulation between YTHDF1/m6A and STING in response to IR, which opens new paths for the development of YTHDF1-targeting therapies.

Monosomy 7 and del(7q) are among the most common cytogenetic abnormalities in myeloid malignancies, yet their underlying pathogenesis remains unclear. Using an array-based CRISPR screen and orthogonal machine learning approach, we identify potential chromosome 7 tumor suppressor genes (TSGs). We selected candidate TSGs via datamining of genome-scale studies, individually CRISPR-edited 108 candidates, and measured the subsequent impact on the proliferation and erythroid differentiation of primary, human CD34+ hematopoietic stem and progenitor cells (HSPCs). An unexpected 39% of genes increased proliferation when edited and were significantly enriched in commonly deleted regions. The only two genes that both increased proliferation and decreased erythroid differentiation when edited were the CUX1 transcription factor and ACHE, encoding acetylcholinesterase, both located in the 7q22.1 commonly deleted region. We demonstrate a novel role for ACHE in regulating erythropoiesis through acetylcholine receptor signaling. The defects stemming from loss of ACHE were corrected by a muscarinic receptor inhibitor, implicating muscarinic antagonists as potential treatments for −7/del(7q)-associated anemia. While chromosome-level deletions were historically thought to harbor a single TSG, the significant enrichment of TSGs within commonly deleted regions suggests a contiguous gene syndrome, wherein combinatorial loss of multiple neighboring genes drives disease.

Key Points Natural killer (NK) cell cytotoxicity is regulated by inhibitory receptors that bind self-MHC class I molecules. The absence of MHC class I expression causes lysis of cells, as described by the 'missing-self' hypothesis. Some aspects of NK-cell biology cannot be explained by the regulation of self-tolerance through MHC class I molecules alone, implying the existence of non-MHC-binding inhibitory receptors. 2B4 is a prototypical MHC-independent inhibitory receptor. It inhibits NK-cell responses to CD48-expressing cells in mice, as well as in the absence of SAP (signalling lymphocytic activation molecule (SLAM)-associated protein) in humans. This inhibition protects against NK-cell autoreactivity. Carcinoembryonic-antigen-related cell-adhesion molecule 1 (CEACAM1) ensures NK-cell tolerance in MHC-class-I-deficient humans. Several other NK-cell inhibitory receptors recognize diverse ligands that are markers of 'self'. These receptors include some NK-cell receptor protein 1 (NKR-P1)-family members, sialic-acid-binding immunoglobulin-like lectins (SIGLECs) and glycoprotein 49 B1 (gp49B1). Non-MHC-binding inhibitory receptors regulate NK-cell responses in disease states, including infection, cancer and autoimmunity. These receptors might provide new targets for improving NK-cell responses, possibly leading to better treatments for such diseases. A fundamental tenet of the immune system is the requirement for lymphocytes to respond to transformed or infected cells while remaining tolerant of normal cells. Natural killer (NK) cells discriminate between self and non-self by monitoring the expression of MHC class I molecules. According to the 'missing-self' hypothesis, cells that express self-MHC class I molecules are protected from NK cells, but those that lack this self-marker are eliminated by NK cells. Recent work has revealed that there is another system of NK-cell inhibition, which is independent of MHC class I molecules. Newly discovered NK-cell inhibitory receptors that have non-MHC-molecule ligands broaden the definition of self as seen by NK cells.

BH3 mimetics are increasingly used as anti-cancer therapeutics either alone or in conjunction with other chemotherapies. However, mounting evidence has also demonstrated that BH3 mimetics modulate varied amounts of apoptotic signaling in healthy immune populations. In order to maximize their clinical potential, it will be essential to understand how BH3 mimetics affect discrete immune populations and to determine how BH3 mimetic pressure causes immune system adaptation. Here we focus on the BCL-2 specific inhibitor venetoclax (ABT-199) and its effects following short-term and long-term BCL-2 blockade on T cell subsets. Seven day “short-term” ex vivo and in vivo BCL-2 inhibition led to divergent cell death sensitivity patterns in CD8 + T cells, CD4 + T cells, and Tregs resulting in shifting of global T cell populations towards a more memory T cell state with increased expression of BCL-2, BCL-X L , and MCL-1. However, twenty-eight day “long-term” BCL-2 blockade following T cell-depleted bone marrow transplantation did not lead to changes in the global T cell landscape. Despite the lack of changes in T cell proportions, animals treated with venetoclax developed CD8 + and CD4 + T cells with high levels of BCL-2 and were more resistant to apoptotic stimuli following expansion post-transplant. Further, we demonstrate through RNA profiling that T cells adapt while under BCL-2 blockade post-transplant and develop a more activated genotype. Taken together, these data emphasize the importance of evaluating how BH3 mimetics affect the immune system in different treatment modalities and disease contexts and suggest that venetoclax should be further explored as an immunomodulatory compound.

CUX1 , encoding a homeodomain-containing transcription factor, is recurrently deleted or mutated in multiple tumor types. In myeloid neoplasms, CUX1 deletion or mutation carries a poor prognosis. We have previously established that CUX1 functions as a tumor suppressor in hematopoietic cells across multiple organisms. Others, however, have described oncogenic functions of CUX1 in solid tumors, often attributed to truncated CUX1 isoforms, p75 and p110, generated by an alternative transcriptional start site or post-translational cleavage, respectively. Given the clinical relevance, it is imperative to clarify these discrepant activities. Herein, we sought to determine the CUX1 isoforms expressed in hematopoietic cells and find that they express the full-length p200 isoform. Through the course of this analysis, we found no evidence of the p75 alternative transcript in any cell type examined. Using an array of orthogonal approaches, including biochemistry, proteomics, CRISPR/Cas9 genomic editing, and analysis of functional genomics datasets across a spectrum of normal and malignant tissue types, we found no data to support the existence of the CUX1 p75 isoform as previously described. Based on these results, prior studies of p75 require reevaluation, including the interpretation of oncogenic roles attributed to CUX1.

Breast cancer, the second leading cause of cancer death of women worldwide, is a heterogenous disease with multiple different subtypes. These subtypes carry important implications for prognosis and therapy. Interestingly, it is known that these different subtypes not only have different biological behaviors, but also have distinct gene expression profiles. However, it has not been rigorously explored whether particular transcriptional isoforms are also differentially expressed among breast cancer subtypes, or whether transcript isoforms from the same sets of genes can be used to differentiate subtypes. To address these questions, we analyzed the patterns of transcript isoform expression using a small set of RNA-sequencing data for eleven Estrogen Receptor positive (ER+) subtype and fourteen triple negative (TN) subtype tumors. We identified specific sets of isoforms that distinguish these tumor subtypes with higher fidelity than standard mRNA expression profiles. We found that alternate promoter usage, alternative splicing, and alternate 3'UTR usage are differentially regulated in breast cancer subtypes. Profiling of isoform expression in a second, independent cohort of 68 tumors confirmed that expression of splice isoforms differentiates breast cancer subtypes. Furthermore, analysis of RNAseq data from 594 cases from the TCGA cohort confirmed the ability of isoform usage to distinguish breast cancer subtypes. Also using our expression data, we identified several RNA processing factors that were differentially expressed between tumor subtypes and/or regulated by estrogen receptor, including YBX1, YBX2, MAGOH, MAGOHB, and PCBP2. RNAi knock-down of these RNA processing factors in MCF7 cells altered isoform expression. These results indicate that global dysregulation of splicing in breast cancer occurs in a subtype-specific and reproducible manner and is driven by specific differentially expressed RNA processing factors.

Current therapies for high-grade TP53 -mutated myeloid neoplasms (≥10% blasts) do not offer a meaningful survival benefit except allogeneic stem cell transplantation in the minority who achieve a complete response to first line therapy (CR1). To identify reliable pre-therapy predictors of complete response to first-line therapy (CR1) and outcomes, we assembled a cohort of 242 individuals with TP53 -mutated myeloid neoplasms and ≥10% blasts with well-annotated clinical, molecular and pathology data. Key outcomes examined were CR1 & 24-month survival (OS24). In this elderly cohort (median age 68.2 years) with 74.0% receiving frontline non-intensive regimens (hypomethylating agents +/- venetoclax), the overall cohort CR1 rate was 25.6% (50/195). We additionally identified several pre-therapy factors predictive of inferior CR1 including male gender ( P  = 0.026), ≥2 autosomal monosomies ( P  < 0.001), −17/17p ( P  = 0.011), multi-hit TP53 allelic state ( P  < 0.001) and CUX1 co-alterations ( P  = 0.010). In univariable analysis of the entire cohort, inferior OS24 was predicated by ≥2 monosomies ( P  = 0.004), TP53 VAF > 25% ( P  = 0.002), TP53 splice junction mutations ( P  = 0.007) and antecedent treated myeloid neoplasm ( P  = 0.001). In addition, mutations/deletions in CUX1 , U2AF1 , EZH2 , TET2 , CBL , or KRAS (‘ EPI6 ’ signature) predicted inferior OS24 (HR = 2.0 [1.5–2.8]; P  < 0.0001). In a subgroup analysis of HMA +/-Ven treated individuals ( N  = 144), TP53 VAF and monosomies did not impact OS24. A risk score for HMA +/-Ven treated individuals incorporating three pre-therapy predictors including TP53 splice junction mutations, EPI6 and antecedent treated myeloid neoplasm stratified 3 prognostic distinct groups: intermediate, intermediate-poor, and poor with significantly different median (12.8, 6.0, 4.3 months) and 24-month (20.9%, 5.7%, 0.5%) survival ( P  < 0.0001). For the first time, in a seemingly monolithic high-risk cohort, our data identifies several baseline factors that predict response and 24-month survival.