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BRCA1 deficiencies cause breast, ovarian, prostate and other cancers, and render tumours hypersensitive to poly(ADP-ribose) polymerase (PARP) inhibitors. To understand the resistance mechanisms, we conducted whole-genome CRISPR–Cas9 synthetic-viability/resistance screens in BRCA1-deficient breast cancer cells treated with PARP inhibitors. We identified two previously uncharacterized proteins, C20orf196 and FAM35A, whose inactivation confers strong PARP-inhibitor resistance. Mechanistically, we show that C20orf196 and FAM35A form a complex, ‘Shieldin’ (SHLD1/2), with FAM35A interacting with single-stranded DNA through its C-terminal oligonucleotide/oligosaccharide-binding fold region. We establish that Shieldin acts as the downstream effector of 53BP1/RIF1/MAD2L2 to promote DNA double-strand break (DSB) end-joining by restricting DSB resection and to counteract homologous recombination by antagonizing BRCA2/RAD51 loading in BRCA1-deficient cells. Notably, Shieldin inactivation further sensitizes BRCA1-deficient cells to cisplatin, suggesting how defining the SHLD1/2 status of BRCA1-deficient tumours might aid patient stratification and yield new treatment opportunities. Highlighting this potential, we document reduced SHLD1/2 expression in human breast cancers displaying intrinsic or acquired PARP-inhibitor resistance. Through CRISPR–Cas9 screen, Dev et al. identified that SHLD1/2 inhibition contributes to PARP-inhibitor resistance. Mechanistically, SHLDs promote non-homologous end-joining and antagonize homologous recombination.

Rubin and colleagues discuss the origin and evolution of poorly differentiated neuroendocrine tumors, and highlight potential new therapeutic strategies. Neuroendocrine (NE) cancers are a diverse group of neoplasms typically diagnosed and treated on the basis of their site of origin. This Perspective focuses on advances in our understanding of the tumorigenesis and treatment of poorly differentiated neuroendocrine tumors. Recent evidence from sequencing indicates that, although neuroendocrine tumors can arise de novo , they can also develop as a result of lineage plasticity in response to pressure from targeted therapies. We discuss the shared genomic alterations of these tumors independently of their site of origin, and we explore potential therapeutic strategies on the basis of recent biological findings.

Key Points Development of vaccines for the treatment of cancer has posed many challenges, but results from some recent studies have confirmed the potential for clinical benefit Progress has been driven by advances in our understanding of cancer immunology and, in particular, the nature and dynamics of the tumour microenvironment Many clinical trials may have failed to adequately account for how vaccines differ from other cancer therapies, and for immunosuppressive mechanisms that operate in the tumour microenvironment Predictive biomarkers that can identify subpopulations of patients most likely to benefit from active immunotherapy are needed Evidence from clinical trials suggest that clinical benefit might be greatest in patients with less advanced-stage malignancies Future strategies should include steps to modify the tumour microenvironment to optimize tumour-specific immune responses Active immunotherapy is emerging as an important addition to conventional cancer treatments, but many important questions remain. Optimal combinations of antigens, adjuvants and delivery vehicles need to be determined and effective strategies for overcoming tumour-associated immunosuppression ought to be developed. This Review provides an overview of new results from clinical studies of therapeutic cancer vaccines directed against tumour-associated antigens and discusses their implications for the use of active immunotherapy. The therapeutic potential of host-specific and tumour-specific immune responses is well recognized and, after many years, active immunotherapies directed at inducing or augmenting these responses are entering clinical practice. Antitumour immunization is a complex, multi-component task, and the optimal combinations of antigens, adjuvants, delivery vehicles and routes of administration are not yet identified. Active immunotherapy must also address the immunosuppressive and tolerogenic mechanisms deployed by tumours. This Review provides an overview of new results from clinical studies of therapeutic cancer vaccines directed against tumour-associated antigens and discusses their implications for the use of active immunotherapy.

Epithelial‐mesenchymal transition (EMT) is a reversible and dynamic process hypothesized to be co‐opted by carcinoma during invasion and metastasis. Yet, there is still no quantitative measure to assess the interplay between EMT and cancer progression. Here, we derived a method for universal EMT scoring from cancer‐specific transcriptomic EMT signatures of ovarian, breast, bladder, lung, colorectal and gastric cancers. We show that EMT scoring exhibits good correlation with previously published, cancer‐specific EMT signatures. This universal and quantitative EMT scoring was used to establish an EMT spectrum across various cancers, with good correlation noted between cell lines and tumours. We show correlations between EMT and poorer disease‐free survival in ovarian and colorectal, but not breast, carcinomas, despite previous notions. Importantly, we found distinct responses between epithelial‐ and mesenchymal‐like ovarian cancers to therapeutic regimes administered with or without paclitaxel in vivo and demonstrated that mesenchymal‐like tumours do not always show resistance to chemotherapy. EMT scoring is thus a promising, versatile tool for the objective and systematic investigation of EMT roles and dynamics in cancer progression, treatment response and survival. Synopsis A novel EMT scoring method reveals that EMT status does not unanimously correlate with poorer overall and disease‐free survival. Different EMTed tumours show distinct responses to certain chemotherapeutics, with the potential to stratify patients by EMT status. A novel scoring method was developed based on transcriptomics to universally estimate and compare the Epithelial‐Mesenchymal Transition (EMT) phenotype across cancer types. A spectrum of EMT was established across more than 15 cancers using this EMT scoring method. Correlations of EMT status with poorer overall‐ and disease‐free survival were not unanimously observed in all cancers. Differential and preferential responses of EMTed tumours to certain chemotherapeutics were observed, suggesting the potential to stratify patients by EMT status. Graphical Abstract A novel EMT scoring method reveals that EMT status does not unanimously correlate with poorer overall and disease‐free survival. Different EMTed tumours show distinct responses to certain chemotherapeutics, with the potential to stratify patients by EMT status.

The authors implement a collection of patient-derived xenograft tumors to test cancer drug responses. Profiling candidate therapeutics with limited cancer models during preclinical development hinders predictions of clinical efficacy and identifying factors that underlie heterogeneous patient responses for patient-selection strategies. We established ∼1,000 patient-derived tumor xenograft models (PDXs) with a diverse set of driver mutations. With these PDXs, we performed in vivo compound screens using a 1 × 1 × 1 experimental design (PDX clinical trial or PCT) to assess the population responses to 62 treatments across six indications. We demonstrate both the reproducibility and the clinical translatability of this approach by identifying associations between a genotype and drug response, and established mechanisms of resistance. In addition, our results suggest that PCTs may represent a more accurate approach than cell line models for assessing the clinical potential of some therapeutic modalities. We therefore propose that this experimental paradigm could potentially improve preclinical evaluation of treatment modalities and enhance our ability to predict clinical trial responses.

Poly(ADP-ribose) polymerase (PARP) inhibitors have activity in ovarian carcinomas with homologous recombination deficiency. Along with BRCA1 and BRCA2 (BRCA) mutations genomic loss of heterozygosity (LOH) might also represent homologous recombination deficiency. In ARIEL2, we assessed the ability of tumour genomic LOH, quantified with a next-generation sequencing assay, to predict response to rucaparib, an oral PARP inhibitor. ARIEL2 is an international, multicentre, two-part, phase 2, open-label study done at 49 hospitals and cancer centres in Australia, Canada, France, Spain, the UK, and the USA. In ARIEL2 Part 1, patients with recurrent, platinum-sensitive, high-grade ovarian carcinoma were classified into one of three predefined homologous recombination deficiency subgroups on the basis of tumour mutational analysis: BRCA mutant (deleterious germline or somatic), BRCA wild-type and LOH high (LOH high group), or BRCA wild-type and LOH low (LOH low group). We prespecified a cutoff of 14% or more genomic LOH for LOH high. Patients began treatment with oral rucaparib at 600 mg twice per day for continuous 28 day cycles until disease progression or any other reason for discontinuation. The primary endpoint was progression-free survival. All patients treated with at least one dose of rucaparib were included in the safety analyses and all treated patients who were classified were included in the primary endpoint analysis. This trial is registered with ClinicalTrials.gov, number NCT01891344. Enrolment into ARIEL2 Part 1 is complete, although an extension (Part 2) is ongoing. 256 patients were screened and 206 were enrolled between Oct 30, 2013, and Dec 19, 2014. At the data cutoff date (Jan 18, 2016), 204 patients had received rucaparib, with 28 patients remaining in the study. 192 patients could be classified into one of the three predefined homologous recombination deficiency subgroups: BRCA mutant (n=40), LOH high (n=82), or LOH low (n=70). Tumours from 12 patients were established as BRCA wild-type, but could not be classified for LOH, because of insufficient neoplastic nuclei in the sample. The median duration of treatment for the 204 patients was 5·7 months (IQR 2·8–10·1). 24 patients in the BRCA mutant subgroup, 56 patients in the LOH high subgroup, and 59 patients in the LOH low subgroup had disease progression or died. Median progression-free survival after rucaparib treatment was 12·8 months (95% CI 9·0–14·7) in the BRCA mutant subgroup, 5·7 months (5·3–7·6) in the LOH high subgroup, and 5·2 months (3·6–5·5) in the LOH low subgroup. Progression-free survival was significantly longer in the BRCA mutant (hazard ratio 0·27, 95% CI 0·16–0·44, p<0·0001) and LOH high (0·62, 0·42–0·90, p=0·011) subgroups compared with the LOH low subgroup. The most common grade 3 or worse treatment-emergent adverse events were anaemia or decreased haemoglobin (45 [22%] patients), and elevations in alanine aminotransferase or aspartate aminotransferase (25 [12%]). Common serious adverse events included small intestinal obstruction (10 [5%] of 204 patients), malignant neoplasm progression (10 [5%]), and anaemia (nine [4%]). Three patients died during the study (two because of disease progression and one because of sepsis and disease progression). No treatment-related deaths occurred. In patients with BRCA mutant or BRCA wild-type and LOH high platinum-sensitive ovarian carcinomas treated with rucaparib, progression-free survival was longer than in patients with BRCA wild-type LOH low carcinomas. Our results suggest that assessment of tumour LOH can be used to identify patients with BRCA wild-type platinum-sensitive ovarian cancers who might benefit from rucaparib. These results extend the potential usefulness of PARP inhibitors in the treatment setting beyond BRCA mutant tumours. Clovis Oncology, US Department of Defense Ovarian Cancer Research Program, Stand Up To Cancer—Ovarian Cancer Research Fund Alliance—National Ovarian Cancer Coalition Dream Team Translational Research Grant, and V Foundation Translational Award.

Angiogenesis is a target in the treatment of ovarian cancer. Nintedanib, an oral triple angiokinase inhibitor of VEGF receptor, platelet-derived growth factor receptor, and fibroblast growth factor receptor, has shown activity in phase 2 trials in this setting. We investigated the combination of nintedanib with standard carboplatin and paclitaxel chemotherapy in patients with newly diagnosed advanced ovarian cancer. In this double-blind phase 3 trial, chemotherapy-naive patients (aged 18 years or older) with International Federation of Gynecology and Obstetrics (FIGO) IIB–IV ovarian cancer and upfront debulking surgery were stratified by postoperative resection status, FIGO stage, and planned carboplatin dose. Patients were randomly assigned (2:1) via an interactive voice or web-based response system to receive six cycles of carboplatin (AUC 5 mg/mL per min or 6 mg/mL per min) and paclitaxel (175 mg/m2) in addition to either 200 mg of nintedanib (nintedanib group) or placebo (placebo group) twice daily on days 2–21 of every 3-week cycle for up to 120 weeks. Patients, investigators, and independent radiological reviewers were masked to treatment allocation. The primary endpoint was investigator-assessed progression-free survival analysed in the intention-to-treat population. This trial is registered with ClinicalTrials.gov, number NCT01015118. Between Dec 9, 2009, and July 27, 2011, 1503 patients were screened and 1366 randomly assigned by nine study groups in 22 countries: 911 to the nintedanib group and 455 to the placebo group. 486 (53%) of 911 patients in the nintedanib group experienced disease progression or death compared with 266 (58%) of 455 in the placebo group. Median progression-free survival was significantly longer in the nintedanib group than in the placebo group (17·2 months [95% CI 16·6–19·9] vs 16·6 months [13·9–19·1]; hazard ratio 0·84 [95% CI 0·72–0·98]; p=0·024). The most common adverse events were gastrointestinal (diarrhoea: nintedanib group 191 [21%] of 902 grade 3 and three [<1%] grade 4 vs placebo group nine [2%] of 450 grade 3 only) and haematological (neutropenia: nintedanib group 180 [20%] grade 3 and 200 (22%) grade 4 vs placebo group 90 [20%] grade 3 and 72 [16%] grade 4; thrombocytopenia: 105 [12%] and 55 [6%] vs 21 [5%] and eight [2%]; anaemia: 108 [12%] and 13 [1%] vs 26 [6%] and five [1%]). Serious adverse events were reported in 376 (42%) of 902 patients in the nintedanib group and 155 (34%) of 450 in the placebo group. 29 (3%) of 902 patients in the nintedanib group experienced serious adverse events associated with death compared with 16 (4%) of 450 in the placebo group, including 12 (1%) in the nintedanib group and six (1%) in the placebo group with a malignant neoplasm progression classified as an adverse event by the investigator. Drug-related adverse events leading to death occurred in three patients in the nintedanib group (one without diagnosis of cause; one due to non-drug-related sepsis associated with drug-related diarrhoea and renal failure; and one due to peritonitis) and in one patient in the placebo group (cause unknown). Nintedanib in combination with carboplatin and paclitaxel is an active first-line treatment that significantly increases progression-free survival for women with advanced ovarian cancer, but is associated with more gastrointestinal adverse events. Future studies should focus on improving patient selection and optimisation of tolerability. Boehringer Ingelheim.

Programmed cell death 1 (PD-1) inhibitors have limited effect in pancreatic ductal adenocarcinoma (PDAC), underscoring the need to co-target alternative pathways. CXC chemokine receptor 4 (CXCR4) blockade promotes T cell tumor infiltration and is synergistic with anti-PD-1 therapy in PDAC mouse models. We conducted a phase IIa, open-label, two-cohort study to assess the safety, efficacy and immunobiological effects of the CXCR4 antagonist BL-8040 (motixafortide) with pembrolizumab and chemotherapy in metastatic PDAC ( NCT02826486 ). The primary outcome was objective response rate (ORR). Secondary outcomes were overall survival (OS), disease control rate (DCR) and safety. In cohort 1, 37 patients with chemotherapy-resistant disease received BL-8040 and pembrolizumab. The DCR was 34.5% in the evaluable population (modified intention to treat, mITT; N  = 29), including nine patients (31%) with stable disease and one patient (3.4%) with partial response. Median OS (mOS) was 3.3 months in the ITT population. Notably, in patients receiving study drugs as second-line therapy, the mOS was 7.5 months. BL-8040 increased CD8 + effector T cell tumor infiltration, decreased myeloid-derived suppressor cells (MDSCs) and further decreased circulating regulatory T cells. In cohort 2, 22 patients received BL-8040 and pembrolizumab with chemotherapy, with an ORR, DCR and median duration of response of 32%, 77% and 7.8 months, respectively. These data suggest that combined CXCR4 and PD-1 blockade may expand the benefit of chemotherapy in PDAC and warrants confirmation in subsequent randomized trials. Results from the phase IIa COMBAT trial combining CXCR4 and PD-1 inhibition in patients with metastatic cancer show encouraging clinical responses in association with enhanced antitumor immune activation.

In May 2017, the FDA approved pembrolizumab, a programmed death 1 inhibitor, for adult and pediatric patients with unresectable or metastatic, microsatellite-instability–high or mismatch-repair–deficient solid tumors, regardless of tumor site or histology.

Antibodies to PD-1 protein and to one of its ligands, PD-L1, have shown antitumor activity. Unleashing T cells from inhibitory signals may be a strategy to treat cancers. Autoimmune side effects from anti–PD-L1 antibody seem less severe than those from anti–CTLA-4 antibody. Passive cancer immunotherapy that uses tumor-targeted monoclonal antibodies has achieved broad therapeutic efficacy. 1 However, T-cell directed immunotherapy has been less successful. 2 Despite the large number of tumor antigens induced by genetic and epigenetic changes found in all cancers, tumors resist immune attack by inducing tolerance among tumor-specific T cells and by expressing ligands that engage inhibitory receptors and dampen T-cell functions within the tumor microenvironment. 3 Preclinical and clinical data show that antibody blockade of these immune checkpoints can significantly enhance antitumor immunity. 4 Cytotoxic T-lymphocyte–associated antigen 4 (CTLA-4), an inhibitory receptor that down-modulates the initial stages of T-cell activation, was the . . .