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BackgroundPALB2is the most important contributor to familial breast cancer afterBRCA1andBRCA2. Large genomic rearrangements (LGRs) inBRCA1andBRCA2are routinely assessed in clinical testing and are a significant contributor to the yield of actionable findings. In contrast, the contribution of LGRs inPALB2has not been systematically studied.MethodsWe performed targeted sequencing and real-time qPCR validation to identify LGRs inPALB2in 5770 unrelated patients with familial breast cancer and 5741 cancer-free control women from the same Australian population.ResultsSeven large deletions ranging in size from 0.96 kbp to 18.07 kbp involvingPALB2were identified in seven cases, while no LGRs were identified in any of the controls. Six LGRs were considered pathogenic as they included one or more exons ofPALB2and disrupted the WD40 domain at the C terminal end of the PALB2 protein while one LGR only involved a partial region of intron 10 and was considered a variant of unknown significance. Altogether, pathogenic LGRs identified in this study accounted for 10.3% (6 of 58) of the pathogenicPALB2variants detected among the 5770 families with familial breast cancer.ConclusionsOur data show that a clinically important proportion ofPALB2pathogenic mutations in Australian patients with familial breast cancer are LGRs. Such observations have provided strong support for inclusion ofPALB2LGRs in routine clinical genetic testing.

Metazoans inherited genes from unicellular ancestors that perform essential biological processes such as cell division, metabolism and protein translation. Functioning multicellularity requires careful control and coordination of these unicellular genes to maintain tissue integrity and homeostasis. Gene regulatory networks (GRNs) formed during metazoan evolution to regulate conserved biological processes are frequently altered in cancer, resulting in over-expression of unicellular genes. We propose an imbalance in co-expression of unicellular (UC) and multicellular (MC) genes is a driving force in cancer. To investigate, we combined gene co-expression analysis to infer changes to GRNs in cancer with protein sequence conservation data to distinguish genes with UC and MC origins. Co-expression networks created using RNA sequencing data from 31 tumour types and normal tissue samples were divided into modules enriched for UC genes, MC genes or a mix of both (Mixed UC-MC modules). The greatest differences between tumour and normal tissue co-expression networks occurred within Mixed UC-MC modules. In particular, MC and UC genes not commonly co-expressed in normal tissues formed distinct co-expression modules seen only in tumours. The degree of rewiring of genes within Mixed UC-MC modules increased with both tumour grade and stage. Mixed UC-MC modules were enriched for somatic mutations in cancer genes, particularly copy-number amplifications, suggesting an important driver of the rewiring observed in tumours are copy-number changes. Overall, our study shows the greatest changes to gene co-expression patterns during tumour progression occur between genes of MC and UC origins, implicating the breakdown and rewiring of metazoan gene regulatory networks in cancer development and progression.Author summaryMulticellular organism cells follow certain rules that control and coordinate their growth and behavior. This happens because gene regulatory networks formed during the evolution of multicellularity to control the activity of genes inherited from unicellular ancestors. Cancer cells disobey these rules, growing and dividing in a competitive fashion analogous to that of colonial unicellular organisms. Here, we test the hypothesis that breakdown of gene regulatory networks enforcing multicellularity drives cancer progression by investigating 31 tumour types. Based on sequence similarity, genes were categorized as having origins in either unicellular or multicellular species. We found that the balance of expression unicellular and multicellular genes changes dramatically in cancer. Genes expressed together in normal tissues stop being co-expressed in tumors, while unicellular and multicellular genes that would not normally be expressed together in normal tissues become highly co-expressed. This phenomenon is more pronounced in cancers at more advanced stages, and sometimes occurs in association with gain or loss of parts of certain chromosomes. Our work indicates disruption and rewiring of gene regulatory networks that evolved to enforce multicellularity drives cancer progression by upsetting the carefully coordinated balance in the activity of unicellular and multicellular genes.

Combined inhibition of BRAF, MEK, and CDK4/6 is currently under evaluation in clinical trials for patients with melanoma harboring a BRAFV600 mutation. While this triple therapy has potent tumor-intrinsic effects, the impact of this combination on antitumor immunity remains unexplored. Here, using a syngeneic BrafV600ECdkn2a−/−Pten−/− melanoma model, we demonstrated that triple therapy promoted durable tumor control through tumor-intrinsic mechanisms and promoted immunogenic cell death and T-cell infiltration. Despite this, tumors treated with triple therapy were unresponsive to immune checkpoint blockade (ICB). Flow cytometric and single-cell RNA sequencing analyses of tumor-infiltrating immune populations revealed that triple therapy markedly depleted proinflammatory macrophages and cross-priming CD103+ dendritic cells, the absence of which correlated with poor overall survival and clinical responses to ICB in patients with melanoma. Indeed, immune populations isolated from tumors of mice treated with triple therapy failed to stimulate T-cell responses ex vivo. While combined BRAF, MEK, and CDK4/6 inhibition demonstrates favorable tumor-intrinsic activity, these data suggest that collateral effects on tumor-infiltrating myeloid populations may impact antitumor immunity. These findings have important implications for the design of combination strategies and clinical trials that incorporate BRAF, MEK, and CDK4/6 inhibition with immunotherapy for the treatment of patients with melanoma.

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Supplementary Table from Epigenetic Activation of Plasmacytoid DCs Drives IFNAR-Dependent Therapeutic Differentiation of AML

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Supplementary Figure from Epigenetic Activation of Plasmacytoid DCs Drives IFNAR-Dependent Therapeutic Differentiation of AML

RNA-seq and scRNA-seq count data and TCR contigs

Merkel cell carcinomas (MCC) are immunogenic skin cancers associated with viral infection or UV mutagenesis. To study T-cell infiltrates in MCC, we analyzed 58 MCC lesions from 39 patients using multiplex-IHC/immunofluorescence (m-IHC/IF). CD4+ or CD8+ T cells comprised the majority of infiltrating T lymphocytes in most tumors. However, almost half of the tumors harbored prominent CD4/CD8 double-negative (DN) T-cell infiltrates (>20% DN T cells), and in 12% of cases, DN T cells represented the majority of T cells. Flow cytometric analysis of single-cell suspensions from fresh tumors identified DN T cells as predominantly Vδ2− γδ T cells. In the context of γδ T–cell inflammation, these cells expressed PD-1 and LAG3, which is consistent with a suppressed or exhausted phenotype, and CD103, which indicates tissue residency. Furthermore, single-cell RNA sequencing (scRNA-seq) identified a transcriptional profile of γδ T cells suggestive of proinflammatory potential. T-cell receptor (TCR) analysis confirmed clonal expansion of Vδ1 and Vδ3 clonotypes, and functional studies using cloned γδ TCRs demonstrated restriction of these for CD1c and MR1 antigen-presenting molecules. On the basis of a 13-gene γδ T–cell signature derived from scRNA-seq analysis, gene-set enrichment on bulk RNA-seq data showed a positive correlation between enrichment scores and DN T-cell infiltrates. An improved disease-specific survival was evident for patients with high enrichment scores, and complete responses to anti–PD-1/PD-L1 treatment were observed in three of four cases with high enrichment scores. Thus, γδ T–cell infiltration may serve as a prognostic biomarker and should be explored for therapeutic interventions.See related Spotlight on p. 600

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New treatments for triple-negative breast cancer (TNBC) are urgently needed. Despite there being little evidence of clinical activity as single-agent therapies, we show that dual blockade of PI3Kα and CDK4/6 is synergistically effective against multiple RB1-wild-type TNBC models. Combined PI3Kα and CDK4/6 inhibition significantly increased apoptosis, cell-cycle arrest, and tumor immunogenicity and generated immunogenic cell death in human TNBC cell lines. Combination treatment also significantly improved disease control in human xenograft models compared with either monotherapy. Combined PI3Kα and CDK4/6 inhibition significantly increased tumor-infiltrating T-cell activation and cytotoxicity and decreased the frequency of immunosuppressive myeloid-derived suppressor cells in a syngeneic TNBC mouse model. Notably, combined PI3Kα and CDK4/6 inhibition, along with inhibition of immune checkpoints PD-1 and CTLA-4, induced complete and durable regressions (>1 year) of established TNBC tumors in vivo. Overall, our results illustrate convergent mechanisms of PI3Kα and CDK4/6 blockade on cell-cycle progression, DNA damage response, and immune-modulation and may provide a novel therapeutic approach for TNBC. Cancer Res; 77(22); 6340–52. ©2017 AACR.

Supplementary Table S1 and Supplementary Figures S1-S3 - Supplementary Table S1: Characteristics of human triple-negative breast cancer cell lines. Supplementary Figure S1: Quantitation of protein expression in HC1806 and MDAMB231 cells following 72 hours of treatment in vitro. Supplementary Figure S2: Combined BYL719 and LEE011 induces anti-tumor immunity in AT3OVA mouse model of triple-negative breast cancer in vivo. Supplementary Figure S3: Immune checkpoint blockade in combination with BYL719 and LEE011 results in durable tumor regression in vivo.

Background: While protein truncating variants in RAD51C have been shown to predispose to triple negative breast cancer (TNBC) and ovarian cancer, little is known about the pathogenicity of missense (MS) variants. Methods: The frequency of rare RAD51C MS variants were assessed in the BEACCON study of 5,734 familial breast cancer cases and 14,382 population controls, and integrated with tumour sequencing data from 21 cases carrying a candidate variant to assess bi-allelic inactivation. Results: Collectively, a significant enrichment of rare missense variants was detected in cases (MAF < 0.001, OR 1.57, 95%CI 1.00 - 2.44, p = 0.05), particularly for variants with a REVEL score > 0.5 (OR 3.95, 95%CI 1.40 - 12.01, p = 0.006). Despite the large sample size, the majority of variants detected were very rare, precluding definitive conclusions about pathogenicity based solely on the case-control data. Sequencing of 21 tumours from carriers of one of eight candidate MS variants, identified four cases with bi-allelic inactivation through loss of the wild-type allele, while six lost the variant allele and ten remained heterozygous. Loss of the wild-type alleles corresponded strongly with ER- and triple-negative breast tumours and a high homologous recombination deficiency score. Conclusions: Using this approach, the p.Gly264Ser variant, which was previously suspected to be pathogenic based on small case-control analyses and loss of activity in in vitro functional assays, was shown to be benign with similar prevalence in cases and controls, and eight out of nine tumours showing loss of the variant allele or retention of heterozygosity. Conversely, the combined case-control and tumour sequencing data identified p.Ile144Thr, p.Arg212His, p.Gln143Arg and p.Gly114Arg as variants warranting further investigation.

Pharmacologic inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6) are an approved treatment for hormone receptor–positive breast cancer and are currently under evaluation across hundreds of clinical trials for other cancer types. The clinical success of these inhibitors is largely attributed to well-defined tumor-intrinsic cytostatic mechanisms, whereas their emerging role as immunomodulatory agents is less understood. Using integrated epigenomic, transcriptomic, and proteomic analyses, we demonstrated a novel action of CDK4/6 inhibitors in promoting the phenotypic and functional acquisition of immunologic T-cell memory. Short-term priming with a CDK4/6 inhibitor promoted long-term endogenous antitumor T-cell immunity in mice, enhanced the persistence and therapeutic efficacy of chimeric antigen receptor T cells, and induced a retinoblastoma-dependent T-cell phenotype supportive of favorable responses to immune checkpoint blockade in patients with melanoma. Together, these mechanistic insights significantly broaden the prospective utility of CDK4/6 inhibitors as clinical tools to boost antitumor T-cell immunity. Significance: Immunologic memory is critical for sustained antitumor immunity. Our discovery that CDK4/6 inhibitors drive T-cell memory fate commitment sheds new light on their clinical activity, which is essential for the design of clinical trial protocols incorporating these agents, particularly in combination with immunotherapy, for the treatment of cancer. This article is highlighted in the In This Issue feature, p. 2355

Background Interferon gamma (IFNγ) is a pro-inflammatory cytokine that directly activates the JAK/STAT pathway. However, the temporal dynamics of chromatin remodeling and transcriptional activation initiated by IFNγ have not been systematically profiled in an unbiased manner. Herein, we integrated transcriptomic and epigenomic profiling to characterize the acute epigenetic changes induced by IFNγ stimulation in a murine breast cancer model. Results We identified de novo activation of cis-regulatory elements bound by Irf1 that were characterized by increased chromatin accessibility, differential usage of pro-inflammatory enhancers, and downstream recruitment of BET proteins and RNA polymerase II. To functionally validate this hierarchical model of IFNγ-driven transcription, we applied selective antagonists of histone acetyltransferases P300/CBP or acetyl-lysine readers of the BET family. This highlighted that histone acetylation is an antecedent event in IFNγ-driven transcription, whereby targeting of P300/CBP acetyltransferase activity but not BET inhibition could curtail the epigenetic remodeling induced by IFNγ through suppression of Irf1 transactivation. Conclusions These data highlight the ability for epigenetic therapies to reprogram pro-inflammatory gene expression, which may have therapeutic implications for anti-tumor immunity and inflammatory diseases. Graphical Abstract

Low-grade serous ovarian carcinoma (LGSOC) is associated with a poor response to existing chemotherapy, highlighting the need to perform comprehensive genomic analysis and identify new therapeutic vulnerabilities. The data presented here represent the largest genetic study of LGSOCs to date (n = 71), analysing 127 candidate genes derived from whole exome sequencing cohorts to generate mutation and copy-number variation data. Additionally, immunohistochemistry was performed on our LGSOC cohort assessing oestrogen receptor, progesterone receptor, TP53, and CDKN2A status. Targeted sequencing identified 47% of cases with mutations in key RAS/RAF pathway genes (KRAS, BRAF, and NRAS), as well as mutations in putative novel driver genes including USP9X (27%), MACF1 (11%), ARID1A (9%), NF2 (4%), DOT1L (6%), and ASH1L (4%). Immunohistochemistry evaluation revealed frequent oestrogen/progesterone receptor positivity (85%), along with CDKN2A protein loss (10%) and CDKN2A protein overexpression (6%), which were linked to shorter disease outcomes. Indeed, 90% of LGSOC samples harboured at least one potentially actionable alteration, which in 19/71 (27%) cases were predictive of clinical benefit from a standard treatment, either in another cancer's indication or in LGSOC specifically. In addition, we validated ubiquitin-specific protease 9X (USP9X), which is a chromosome X-linked substrate-specific deubiquitinase and tumour suppressor, as a relevant therapeutic target for LGSOC. Our comprehensive genomic study highlighted that there is an addiction to a limited number of unique 'driver' aberrations that could be translated into improved therapeutic paths. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Intraductal papillomas (IDP) are challenging breast findings because of their variable risk of progression to malignancy. The molecular events driving IDP development and genomic features of malignant progression are poorly understood. In this study, genome-wide CNA and/or targeted mutation analysis was performed on 44 cases of IDP, of which 20 cases had coexisting ductal carcinoma in situ (DCIS), papillary DCIS or invasive ductal carcinoma (IDC). CNA were rare in pure IDP, but 69% carried an activating PIK3CA mutation. Among the synchronous IDP cases, 55% (11/20) were clonally related to the synchronous DCIS and/or IDC, only one of which had papillary histology. In contrast to pure IDP, PIK3CA mutations were absent from clonal cases. CNAs in any of chromosomes 1, 16 or 11 were significantly enriched in clonal IDP lesions compared to pure and non-clonal IDP. The observation that 55% of IDP are clonal to DCIS/IDC indicates that IDP can be a direct precursor for breast carcinoma, not limited to the papillary type. The absence of PIK3CA mutations and presence of CNAs in IDP could be used clinically to identify patients at high risk of progression to carcinoma.

Therapeutic targeting of dysregulated transcriptional programs has arisen as a promising strategy for the treatment of leukaemias. The therapeutic response to small molecule inhibitors of Bromodomain-Containing Proteins (BRD), such as BRD2 and BRD4, P300/cAMP-response element binding protein (CBP) and Cyclin Dependent Kinases (CDKs), is generally attributed to the selective disruption of oncogenic gene expression networks driven by enhancers, super-enhancers (SEs) and lineage-specific transcription factors (TFs), including thec-MYConcogene. Using technologies such as thiol (SH)-linked alkylation for the metabolic sequencing of RNA sequencing (SLAM-seq) to profile messenger RNA (mRNA) decay and production rates, we demonstrate that gene intrinsic properties largely govern the selectivity associated with transcriptional inhibition, where total mRNA response signatures are dominated with genes that have short transcript half-lives, including those regulated by SEs and oncogenic TFs. Further highlighting that gene sensitivities only occur in the context of short transcript half-lives, stabilisation of thec-MYCtranscript through changes in the 3’ UTR rendered it insensitive to transcriptional targeting. However, this was not sufficient to rescuec-MYCtarget gene transcription and anti-leukaemia effects following transcriptional inhibition. Importantly, long-lived mRNAs encoding essential genes that evade transcriptional targeting can be rendered sensitive via modulation of mRNA decay kinetics through inhibition of the RNA Binding Protein (RBP), ELAV Like RNA binding protein 1 (ELAVL1)/ Human Antigen R (HuR). Taken together, these data demonstrate that mRNA decay shapes the therapeutic response to transcriptional perturbation and can be modulated for novel therapeutic outcomes using transcriptional agents in leukaemia.

Background Breast cancers (BCs) that arise in individuals heterozygous for a germline pathogenic variant in a susceptibility gene, such as BRCA1 and BRCA2, PALB2, and RAD51C, have been shown to exhibit biallelic loss in the respective genes and be associated with triple-negative breast cancer (TNBC) and distinctive somatic mutational signatures. Tumor sequencing thus presents an orthogonal approach to assess the role of candidate genes in BC development. Methods Exome sequencing was performed on paired normal-breast tumor DNA from 124 carriers of germline loss-of-function (LoF) or missense variant carriers in 15 known and candidate BC predisposition genes identified in the BEACCON case-control study. Biallelic inactivation and association with tumor genome features including mutational signatures and homologous recombination deficiency (HRD) score were investigated. Results BARD1-carrying TNBC (4 of 5) displayed biallelic loss and associated high HRD scores and mutational signature 3, as did a RAD51D-carrying TNBC and ovarian cancer. Biallelic loss was less frequent in BRIP1 BCs (4 of 13) and had low HRD scores. In contrast to other established BC genes, BCs from carriers of CHEK2 LoF (6 of 17) or missense (2 of 20) variant had low rates of biallelic loss. Exploratory analysis of BC from carriers of LoF variants in candidate genes such as BLM, FANCM, PARP2, and RAD50 found little evidence of biallelic inactivation. Conclusions BARD1 and RAD51D behave as classic BRCA-like predisposition genes with biallelic inactivation, but this was not observed for any of the candidate genes. However, as demonstrated for CHEK2, the absence of biallelic inactivation does not provide definitive evidence against the gene’s involvement in BC predisposition.

We performed targeted sequencing and real-time qPCR validation to identify LGRs inSeven large deletions ranging in size from 0.96 kbp to 18.07 kbp involvingOur data show that a clinically important proportion of

Pheochromocytomas (PC) and paragangliomas (PG) are rare neuroendocrine tumors associated with autonomic nerves. Here we use single-nuclei RNA-seq and bulk-tissue gene-expression data to characterize the cellular composition of PCPG and normal adrenal tissues, refine tumor gene-expression subtypes and make clinical and genotypic associations. We confirm seven PCPG gene-expression subtypes with significant genotype and clinical associations. Tumors with mutations in VHL, SDH-encoding genes (SDHx) or MAML3-fusions are characterized by hypoxia-inducible factor signaling and neoangiogenesis. PCPG have few infiltrating lymphocytes but abundant macrophages. While neoplastic cells transcriptionally resemble mature chromaffin cells, early chromaffin and neuroblast markers are also features of some PCPG subtypes. The gene-expression profile of metastatic SDHx-related PCPG indicates these tumors have elevated cellular proliferation and a lower number of non-neoplastic Schwann-cell-like cells, while GPR139 is a potential theranostic target. Our findings therefore clarify the diverse transcriptional programs and cellular composition of PCPG and identify biomarkers of potential clinical significance.

Objective Mucinous ovarian carcinoma (MOC) is an uncommon ovarian cancer histotype that responds poorly to conventional chemotherapy regimens. Although long overall survival outcomes can occur with early detection and optimal surgical resection, recurrent and advanced disease are associated with extremely poor survival. There are no current guidelines specifically for the systemic management of recurrent MOC. We analyzed data from a large cohort of women with MOC to evaluate the potential for clinical utility from a range of systemic agents. Methods We analyzed gene copy number (n = 191) and DNA sequencing data (n = 184) from primary MOC to evaluate signatures of mismatch repair deficiency and homologous recombination deficiency, and other genetic events. Immunohistochemistry data were collated for ER, CK7, CK20, CDX2, HER2, PAX8 and p16 (n = 117–166). Results Molecular aberrations noted in MOC that suggest a match with current targeted therapies include amplification of ERBB2 (26.7%) and BRAF mutation (9%). Observed genetic events that suggest potential efficacy for agents currently in clinical trials include: KRAS/NRAS mutations (66%), TP53 missense mutation (49%), RNF43 mutation (11%), ARID1A mutation (10%), and PIK3CA/PTEN mutation (9%). Therapies exploiting homologous recombination deficiency (HRD) may not be effective in MOC, as only 1/191 had a high HRD score. Mismatch repair deficiency was similarly rare (1/184). Conclusions Although genetically diverse, MOC has several potential therapeutic targets. Importantly, the lack of response to platinum-based therapy observed clinically corresponds to the lack of a genomic signature associated with HRD, and MOC are thus also unlikely to respond to PARP inhibition.

Background Loss-of-function variants in RAD51C are associated with familial ovarian cancer, but its role in hereditary breast cancer remains unclear. The aim of this study was to couple breast tumor sequencing with case-control data to clarify the contribution of RAD51C to hereditary breast cancer. Methods RAD51C was sequenced in 3080 breast cancer index cases that were negative in BRCA1/2 clinical tests and 4840 population-matched cancer-free controls. Pedigree and pathology data were analyzed. Nine breast cancers and one ovarian cancer from RAD51C variant carriers were sequenced to identify biallelic inactivation of RAD51C, copy number variation, mutational signatures, and the spectrum of somatic mutations in breast cancer driver genes. The promoter of RAD51C was analyzed for DNA methylation. Results A statistically significant excess of loss-of-function variants was identified in 3080 cases (0.4%) compared with 2 among 4840 controls (0.04%; odds ratio = 8.67, 95% confidence interval = 1.89 to 80.52, P< .001), with more than half of the carriers having no personal or family history of ovarian cancer. In addition, the association was highly statistically significant among cases with estrogen-negative (P Conclusions This study provides evidence that germline loss-of-function variants of RAD51C are associated with hereditary breast cancer, particularly triple-negative type. RAD51C-null breast cancers possess similar genomic and clinical features to BRCA1-null cancers and may also be vulnerable to DNA double-strand break inducing chemotherapies and poly ADP-ribose polymerase inhibitors.

Context von Hippel-Lindau (VHL) disease, comprising renal cancer, hemangioblastoma, and/or pheochromocytoma (PHEO), is caused by missense or truncating variants of the VHL tumor-suppressor gene, which is involved in degradation of hypoxia-inducible factors (HIFs). However, the role of synonymous VHL variants in the disease is unclear. Objective We evaluated a synonymous VHL variant in patients with familial PHEO or VHL disease without a detectable pathogenic VHL mutation. Design We performed genetic and transcriptional analyses of leukocytes and/or tumors from affected and unaffected individuals and evaluated VHL splicing in existing cancer databases. Results We identified a synonymous VHL variant (c.414A>G, p.Pro138Pro) as the driver event in five independent individuals/families with PHEOs or VHL syndrome. This variant promotes exon 2 skipping and hence, abolishes expression of the full-length VHL transcript. Exon 2 spans the HIF-binding domain required for HIF degradation by VHL. Accordingly, PHEOs carrying this variant display HIF hyperactivation typical of VHL loss. Moreover, other exon 2 VHL variants from the The Cancer Genome Atlas pan-cancer datasets are biased toward expression of a VHL transcript that excludes this exon, supporting a broader impact of this spliced variant. Conclusion A recurrent synonymous VHL variant (c.414A>G, p.Pro138Pro) confers susceptibility to PHEO and VHL disease through splice disruption, leading to VHL dysfunction. This finding indicates that certain synonymous VHL variants may be clinically relevant and should be considered in genetic testing and surveillance settings. The observation that other coding VHL variants can exclude exon 2 suggests that dysregulated splicing may be an underappreciated mechanism in VHL-mediated tumorigenesis.

Breast cancer (BC) diagnosed after a negative mammogram but prior to the next screening episode is termed an 'interval BC' (IBC). Understanding the molecular differences between IBC and screen-detected BCs (SDBC) could improve mammographic screening and management options. Therefore, we assessed both germline and somatic genomic aberrations in a prospective cohort. Utilising the Lifepool cohort of >54 000 women attending mammographic screening programs, 930 BC cases with screening status were identified (726 SDBC and 204 IBC). Clinico-pathological and family history information were recorded. Germline and tumour DNA were collected where available and sequenced for BC predisposition and driver gene mutations. Compared to SDBC, IBCs were significantly associated with a younger age at diagnosis and tumour characteristics associated with worse prognosis. Germline DNA assessment of BC cases that developed post-enrolment (276 SDBCs and 77 IBCs) for pathogenic mutations in 12 hereditary BC predisposition genes identified 8 carriers (2.27%). The germline mutation frequency was higher in IBC versus SDBC, although not statistically significant (3.90% versus 1.81%, p = 0.174). Comparing somatic genetic features of IBC and SDBC matched for grade, histological subtype and hormone receptor revealed no significant differences, with the exception of higher homologous recombination deficiency scores in IBC, and copy number changes on chromosome Xq in triple negative SDBCs. Our data demonstrates that while IBCs are clinically more aggressive than SDBC, when matched for confounding clinico-pathological features they do not represent a unique molecular class of invasive BC, but could be a consequence of timing of tumour initiation and mammographic screening. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Acute myeloid leukemia (AML) is a heterogeneous disease with poor prognosis and limited treatment strategies. Determining the role of cell-extrinsic regulators of leukemic cells is vital to gain clinical insights into the biology of AML. Iron is a key extrinsic regulator of cancer, but its systemic regulation remains poorly explored in AML. To address this question, we studied iron metabolism in patients with AML at diagnosis and explored the mechanisms involved using the syngeneic MLL-AF9–induced AML mouse model. We found that AML is a disorder with a unique iron profile, not associated with inflammation or transfusion, characterized by high ferritin, low transferrin, high transferrin saturation (TSAT), and high hepcidin. The increased TSAT in particular, contrasts with observations in other cancer types and in anemia of inflammation. Using the MLL-AF9 mouse model of AML, we demonstrated that the AML-induced loss of erythroblasts is responsible for iron redistribution and increased TSAT. We also show that AML progression is delayed in mouse models of systemic iron overload and that elevated TSAT at diagnosis is independently associated with increased overall survival in AML. We suggest that TSAT may be a relevant prognostic marker in AML.

Gene expression by RNA polymerase II (RNAPII) is tightly controlled by cyclin-dependent kinases (CDKs) at discrete checkpoints during the transcription cycle. The pausing checkpoint following transcription initiation is primarily controlled by CDK9. We discovered that CDK9-mediated, RNAPII-driven transcription is functionally opposed by a protein phosphatase 2A (PP2A) complex that is recruited to transcription sites by the Integrator complex subunit INTS6. PP2A dynamically antagonizes phosphorylation of key CDK9 substrates including DSIF and RNAPII-CTD. Loss of INTS6 results in resistance to tumor cell death mediated by CDK9 inhibition, decreased turnover of CDK9 phospho-substrates, and amplification of acute oncogenic transcriptional responses. Pharmacological PP2A activation synergizes with CDK9 inhibition to kill both leukemic and solid tumor cells, providing therapeutic benefit in vivo. These data demonstrate that fine control of gene expression relies on the balance between kinase and phosphatase activity throughout the transcription cycle, a process dysregulated in cancer that can be exploited therapeutically.

Bi-allelic loss-of-function (LoF) variants in the base excision repair (BER) gene NTHL1 cause a high-risk hereditary multi-tumor syndrome that includes breast cancer, but the contribution of heterozygous variants to hereditary breast cancer is unknown. An analysis of 4985 women with breast cancer, enriched for familial features, and 4786 cancer-free women revealed significant enrichment for NTHL1 LoF variants. Immunohistochemistry confirmed reduced NTHL1 expression in tumors from heterozygous carriers but the NTHL1 bi-allelic loss characteristic mutational signature (SBS 30) was not present. The analysis was extended to 27,421 breast cancer cases and 19,759 controls from 10 international studies revealing 138 cases and 93 controls with a heterozygous LoF variant (OR 1.06, 95% CI: 0.82–1.39) and 316 cases and 179 controls with a missense variant (OR 1.31, 95% CI: 1.09–1.57). Missense variants selected for deleterious features by a number of in silico bioinformatic prediction tools or located within the endonuclease III functional domain showed a stronger association with breast cancer. Somatic sequencing of breast cancers from carriers indicated that the risk associated with NTHL1 appears to operate through haploinsufficiency, consistent with other described low-penetrance breast cancer genes. Data from this very large international multicenter study suggests that heterozygous pathogenic germline coding variants in NTHL1 may be associated with low- to moderate- increased risk of breast cancer.

Introduction: Up to 25% of cases of ductal carcinoma in situ (DCIS) recur, and half of these recur as invasive breast cancer (IBC). There is no biomarker to predict which DCIS cases will recur but it has been suggested that a biomarker would allow de-escalation of the current paradigm of treating most patients with surgery and/or radiotherapy. However, we hypothesize that not all recurrences are genetically similar to the primary DCIS (i.e. non-clonal) and therefore arise de novo. To test this we assembled a large recurrence cohort to explore the clonal relatedness of primary-recurrence tumor pairs prior to proposing a predictive biomarker (Gorringe et al Mod Pathol 2015). Method: We microdissected and extracted DNA from 65 pairs of primary DCIS and recurrences. Half of these recurrences were IBC. We analyzed 21 pairs by targeted sequencing or low-coverage whole-genome sequencing (LCWGS, 2x depth) and 44 pairs with Whole Exome Sequencing (WES, average depth 95x). We similarly analyzed a set of non-recurrent DCIS cases (n=29) treated with wide local excision and with a minimum of 7 years follow-up. No matched normal samples were available. Several approaches were utilized to investigate clonal relatedness using copy number alterations and mutations (when detected), including the Clonality package (Mauguen et al Biometrics 2018), manual breakpoint inspection (Bollet et al JNCI 2008), and clonality indexes (Schultheis et al JNCI 2016). Phylogenetic analyses were carried out by MEDICC2 (Petkovic et al bioRxiv 2021) on WES samples. Results: 62% of cases were clonal (40/65), 28% were non-clonal. There were 7/65 that were equivocal, although further validation will be performed. There was no significant difference in clonal relatedness whether the recurrence was IBC or DCIS. IBC recurrent cases showed a significantly higher ploidy than the DCIS recurrences. The final phylogenetic analysis with MEDICC2 will be presented, which will take into account any subclonal whole-genome doubling events. Furthermore, clonal primary DCIS showed a significantly higher number of TP53 mutations compared to non-recurrent and non-clonal primaries (p Conclusion: Detailed molecular analysis of a large cohort of matched DCIS primary and their recurrences using high sequencing resolution showed a substantial proportion of recurrences were not genetically related to the primary DCIS. Our observations raise the question of whether a tumor intrinsic biomarker alone would be sufficient to predict DCIS recurrences. Citation Format: Tanjina Kader, Sakshi Mahale, Magnus Zethoven, Hugo Saunders, Dorothea Lesche, David Byrne, Siqi Lai, Lauren Tjoeka, Claire Candido, Maree Pechlevanis, Olivia Craig, Jia-Min Pang, Lisa Devereux, Shona Hendry, Eloise House, Sureshni Jayasinghe, Michael Toss, Islam M. Miligy, Emad Rakha, Stephen Fox, Bruce Mann, Ian Campbell, Kylie Gorringe. Predictive biomarkers of recurrence may not be useful for deescalating treatment of breast ductal carcinoma in situ due to de novo ipsilateral breast carcinoma development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 43.

A new technology, SUGAR-seq, enables simultaneous detection of surface glycans, epitopes, transcripts, and TCR repertoire., Multimodal single-cell RNA sequencing enables the precise mapping of transcriptional and phenotypic features of cellular differentiation states but does not allow for simultaneous integration of critical posttranslational modification data. Here, we describe SUrface-protein Glycan And RNA-seq (SUGAR-seq), a method that enables detection and analysis of N-linked glycosylation, extracellular epitopes, and the transcriptome at the single-cell level. Integrated SUGAR-seq and glycoproteome analysis identified tumor-infiltrating T cells with unique surface glycan properties that report their epigenetic and functional state.

Merkel cell carcinomas (MCC) are immunogenic skin cancers associated with viral infection or UV mutagenesis. To study T-cell infiltrates in MCC, we analyzed 58 MCC lesions from 39 patients using multiplex-IHC/immunofluorescence (m-IHC/IF). CD4+ or CD8+ T cells comprised the majority of infiltrating T lymphocytes in most tumors. However, almost half of the tumors harbored prominent CD4/CD8 double-negative (DN) T-cell infiltrates (>20% DN T cells), and in 12% of cases, DN T cells represented the majority of T cells. Flow cytometric analysis of single-cell suspensions from fresh tumors identified DN T cells as predominantly Vδ2− γδ T cells. In the context of γδ T–cell inflammation, these cells expressed PD-1 and LAG3, which is consistent with a suppressed or exhausted phenotype, and CD103, which indicates tissue residency. Furthermore, single-cell RNA sequencing (scRNA-seq) identified a transcriptional profile of γδ T cells suggestive of proinflammatory potential. T-cell receptor (TCR) analysis confirmed clonal expansion of Vδ1 and Vδ3 clonotypes, and functional studies using cloned γδ TCRs demonstrated restriction of these for CD1c and MR1 antigen-presenting molecules. On the basis of a 13-gene γδ T–cell signature derived from scRNA-seq analysis, gene-set enrichment on bulk RNA-seq data showed a positive correlation between enrichment scores and DN T-cell infiltrates. An improved disease-specific survival was evident for patients with high enrichment scores, and complete responses to anti–PD-1/PD-L1 treatment were observed in three of four cases with high enrichment scores. Thus, γδ T–cell infiltration may serve as a prognostic biomarker and should be explored for therapeutic interventions. See related Spotlight on p. 600

Pharmacological inhibition of epigenetic enzymes can have therapeutic benefit, particularly against hematological malignancies. While these agents can affect tumor cell growth and proliferation, recent studies have demonstrated that pharmacological de-regulation of epigenetic modifiers may additionally mediate anti-tumor immune responses. Here we discovered a novel mechanism of immune regulation through the inhibition of histone deacetylases (HDACs). In a genetically engineered model of t(8;21) AML, leukemia cell differentiation and therapeutic benefit mediated by the HDAC inhibitor panobinostat required activation of the type I interferon (IFN) signaling pathway. Plasmacytoid dendritic cells (pDCs) were identified as the cells producing type I IFN in response to panobinostat, through transcriptional activation of IFN genes concomitant with increased H3K27 acetylation at these loci. Depletion of pDCs abrogated panobinostat-mediated activation of type I IFN signaling in leukemia cells and impaired therapeutic efficacy, while combined treatment of panobinostat and recombinant IFNα improved therapeutic outcomes. These discoveries offer a new therapeutic approach for t(8;21) AML and demonstrate that epigenetic rewiring of pDCs enhances anti-tumor immunity, opening the possibility of exploiting this cell type as a new target for immunotherapy.

MR1-restricted mucosal-associated invariant T (MAIT) cells recognize microbial metabolites and play an important role in immunity to infection, however, the role they play in tumor immunity is unclear. Here we show that MAIT cell-deficient mice are more resistant to subcutaneous and lung metastasis B16F10 tumor growth compared to control mice, an effect that was associated with enhanced NK cell numbers and was NK cell-dependent. Analysis of this interplay in cancer patients also revealed that a high expression of a novel MAIT gene signature negatively impacted the prognostic significance of NK cells. Paradoxically, pre-pulsing tumors with MAIT cell antigens, or antigen-mediated MAIT cell activation in vivo, enhanced immunity against B16F10 and E0771 lung tumor metastasis. Furthermore, MAIT cell activation effectively reduced metastatic burden in a more stringent model of established lung metastases in mice. These effects were associated with enhanced NK cell responses and increased expression of both IFNγ-dependent and inflammatory genes in NK cells, which was neutralized by IFNγ blockade. Importantly, activated human MAIT cells also enhanced the function of NK cells isolated from patient tumor samples. These findings provide insight into the contrasting roles that MAIT cells can play in controlling anti-tumor immune responses depending on their activation status, in both mice and humans, and suggest potential therapeutic avenues for exploiting their potential anti-tumor properties for cancer treatment.

Pharmacologic inhibition of epigenetic enzymes can have therapeutic benefit against hematologic malignancies. In addition to affecting tumor cell growth and proliferation, these epigenetic agents may induce antitumor immunity. Here, we discovered a novel immunoregulatory mechanism through inhibition of histone deacetylases (HDAC). In models of acute myeloid leukemia (AML), leukemia cell differentiation and therapeutic benefit mediated by the HDAC inhibitor (HDACi) panobinostat required activation of the type I interferon (IFN) pathway. Plasmacytoid dendritic cells (pDC) produced type I IFN after panobinostat treatment, through transcriptional activation of IFN genes concomitant with increased H3K27 acetylation at these loci. Depletion of pDCs abrogated panobinostat-mediated induction of type I IFN signaling in leukemia cells and impaired therapeutic efficacy, whereas combined treatment with panobinostat and IFNα improved outcomes in preclinical models. These discoveries offer a new therapeutic approach for AML and demonstrate that epigenetic rewiring of pDCs enhances antitumor immunity, opening the possibility of exploiting this approach for immunotherapies. Significance: We demonstrate that HDACis induce terminal differentiation of AML through epigenetic remodeling of pDCs, resulting in production of type I IFN that is important for the therapeutic effects of HDACis. The study demonstrates the important functional interplay between the immune system and leukemias in response to HDAC inhibition. This article is highlighted in the In This Issue feature, p. 1397