The AMBRA1 E3 ligase adaptor regulates the stability of cyclin D.

The initiation of cell division integrates a large number of intra- and extracellular inputs. D-type cyclins (hereafter, cyclin D) couple these inputs to the initiation of DNA replication1. Increased levels of cyclin D promote cell division by activating cyclin-dependent kinases 4 and 6 (hereafter, CDK4/6), which in turn phosphorylate and inactivate the retinoblastoma tumour suppressor. Accordingly, increased levels and activity of cyclin D-CDK4/6 complexes are strongly linked to unchecked cell proliferation and cancer2,3. However, the mechanisms that regulate levels of cyclin D are incompletely understood4,5. Here we show that autophagy and beclin 1 regulator 1 (AMBRA1) is the main regulator of the degradation of cyclin D. We identified AMBRA1 in a genome-wide screen to investigate the genetic basis of  the response to CDK4/6 inhibition. Loss of AMBRA1 results in high levels of cyclin D in cells and in mice, which promotes proliferation and decreases sensitivity to CDK4/6 inhibition. Mechanistically, AMBRA1 mediates ubiquitylation and proteasomal degradation of cyclin D as a substrate receptor for the cullin 4 E3 ligase complex. Loss of AMBRA1 enhances the growth of lung adenocarcinoma in a mouse model, and low levels of AMBRA1 correlate with worse survival in patients with lung adenocarcinoma. Thus, AMBRA1 regulates cellular levels of cyclin D, and contributes to cancer development and the response of cancer cells to CDK4/6 inhibitors.

Author Correction: Tumour lineage shapes BRCA-mediated phenotypes.

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

Serine starvation silences estrogen receptor signaling through histone hypoacetylation.

Loss of estrogen receptor (ER) pathway activity promotes breast cancer progression, yet how this occurs remains poorly understood. Here, we show that serine starvation, a metabolic stress often found in breast cancer, represses estrogen receptor alpha (ERα) signaling by reprogramming glucose metabolism and epigenetics. Using isotope tracing and time-resolved metabolomic analyses, we demonstrate that serine is required to maintain glucose flux through glycolysis and the TCA cycle to support acetyl-CoA generation for histone acetylation. Consequently, limiting serine depletes histone H3 lysine 27 acetylation (H3K27ac), particularly at the promoter region of ER pathway genes including the gene encoding ERα, ESR1. Mechanistically, serine starvation impairs acetyl-CoA-dependent gene expression by inhibiting the entry of glycolytic carbon into the TCA cycle and down-regulating the mitochondrial citrate exporter SLC25A1, a critical enzyme in the production of nucleocytosolic acetyl-CoA from glucose. Consistent with this model, total H3K27ac and ERα expression are suppressed by SLC25A1 inhibition and restored by acetate, an alternate source of acetyl-CoA, in serine-free conditions. We thus uncover an unexpected role for serine in sustaining ER signaling through the regulation of acetyl-CoA metabolism.

Tumour lineage shapes BRCA-mediated phenotypes.

Mutations in BRCA1 and BRCA2 predispose individuals to certain cancers1-3, and disease-specific screening and preventative strategies have reduced cancer mortality in affected patients4,5. These classical tumour-suppressor genes have tumorigenic effects associated with somatic biallelic inactivation, although haploinsufficiency may also promote the formation and progression of tumours6,7. Moreover, BRCA1/2-mutant tumours are often deficient in the repair of double-stranded DNA breaks by homologous recombination8-13, and consequently exhibit increased therapeutic sensitivity to platinum-containing therapy and inhibitors of poly-(ADP-ribose)-polymerase (PARP)14,15. However, the phenotypic and therapeutic relevance of mutations in BRCA1 or BRCA2 remains poorly defined in most cancer types. Here we show that in the 2.7% and 1.8% of patients with advanced-stage cancer and germline pathogenic or somatic loss-of-function alterations in BRCA1/2, respectively, selective pressure for biallelic inactivation, zygosity-dependent phenotype penetrance, and sensitivity to PARP inhibition were observed only in tumour types associated with increased heritable cancer risk in BRCA1/2 carriers (BRCA-associated cancer types). Conversely, among patients with non-BRCA-associated cancer types, most carriers of these BRCA1/2 mutation types had evidence for tumour pathogenesis that was independent of mutant BRCA1/2. Overall, mutant BRCA is an indispensable founding event for some tumours, but in a considerable proportion of other cancers, it appears to be biologically neutral-a difference predominantly conditioned by tumour lineage-with implications for disease pathogenesis, screening, design of clinical trials and therapeutic decision-making.

Ampullary cancer: Evaluation of somatic and germline genetic alterations and association with clinical outcomes.

BACKGROUND: Ampullary carcinoma (AC) is a rare gastrointestinal cancer. Pathogenic germline alterations (PGAs) in BRCA2 and potentially targetable somatic alterations (SAs) in ERBB2 and ELF3 have been previously described in AC. Memorial Sloan Kettering Cancer Center has implemented an opt-in strategy for germline testing (GT) and somatic testing (ST) for patients with AC to further evaluate the spectrum of PGAs and SAs. METHODS: Forty-five patients with pathologically confirmed AC prospectively consented with the Memorial Sloan Kettering Integrated Mutation Profiling of Actionable Cancer Targets (MSK-IMPACT) test (410-468 genes). A subset of the cohort (23 of the 45 patients) also consented to GT with MSK-IMPACT (76-88 genes). Germline data for 21 of the remaining 22 patients who had not consented to GT were obtained in a de-identified fashion without clinical correlation. Clinicopathologic features, treatment histories, and survival data for consenting patients were collected and analyzed. RESULTS: Pancreaticobiliary, intestinal, and mixed features of the 2 types were the primary pathologic subtypes of AC identified in this cohort. No difference in median overall survival was found between pathologic subtypes. Eight of 44 patients (18%) were identified as harboring pathogenic mutations in BRCA2, ATM, RAD50, and MUTYH. In addition, this study found a wide spectrum of SAs in genes such as KRAS, MDM2, ERBB2, ELF3, and PIK3CA. Two patients in the cohort underwent SA-targeted therapy, and 1 had a partial radiographic response. CONCLUSIONS: Mutations in multiple somatic and germline genes were identified in this cohort. Significantly, actionable targets were identified in the tumors, and broader testing for PGAs and SAs should be considered for all patients with AC.

Multiplex picoliter-droplet digital PCR for quantitative assessment of DNA integrity in clinical samples.

BACKGROUND: Assessment of DNA integrity and quantity remains a bottleneck for high-throughput molecular genotyping technologies, including next-generation sequencing. In particular, DNA extracted from paraffin-embedded tissues, a major potential source of tumor DNA, varies widely in quality, leading to unpredictable sequencing data. We describe a picoliter droplet-based digital PCR method that enables simultaneous detection of DNA integrity and the quantity of amplifiable DNA. METHODS: Using a multiplex assay, we detected 4 different target lengths (78, 159, 197, and 550 bp). Assays were validated with human genomic DNA fragmented to sizes of 170 bp to 3000 bp. The technique was validated with DNA quantities as low as 1 ng. We evaluated 12 DNA samples extracted from paraffin-embedded lung adenocarcinoma tissues. RESULTS: One sample contained no amplifiable DNA. The fractions of amplifiable DNA for the 11 other samples were between 0.05% and 10.1% for 78-bp fragments and ≤1% for longer fragments. Four samples were chosen for enrichment and next-generation sequencing. The quality of the sequencing data was in agreement with the results of the DNA-integrity test. Specifically, DNA with low integrity yielded sequencing results with lower levels of coverage and uniformity and had higher levels of false-positive variants. CONCLUSIONS: The development of DNA-quality assays will enable researchers to downselect samples or process more DNA to achieve reliable genome sequencing with the highest possible efficiency of cost and effort, as well as minimize the waste of precious samples.

Associations Between Cancer Predisposition Mutations and Clonal Hematopoiesis in Patients With Solid Tumors.

PURPOSE: Clonal hematopoiesis (CH), the expansion of clones in the hematopoietic system, has been linked to different internal and external features such as aging, genetic ancestry, smoking, and oncologic treatment. However, the interplay between mutations in known cancer predisposition genes and CH has not been thoroughly examined in patients with solid tumors. METHODS: We used prospective tumor-blood paired sequencing data from 46,906 patients who underwent Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets (MSK-IMPACT) testing to interrogate the associations between CH and rare pathogenic or likely pathogenic (P/LP) germline variants. RESULTS: We observed an enrichment of CH-positive patients among those carrying P/LP germline mutations and identified a significant association between P/LP germline variants in ATM and CH. Germline and CH comutation patterns in ATM, TP53, and CHEK2 suggested biallelic inactivation as a potential mediator of clonal expansion. Moreover, we observed that CH-PPM1D mutations, similar to somatic tumor-associated PPM1D mutations, were depleted in patients with P/LP germline mutations in the DNA damage response (DDR) genes ATM, CHEK2, and TP53. Patients with solid tumors and harboring P/LP germline mutations, CH mutations, and mosaicism chromosomal alterations might be at an increased risk of developing secondary leukemia while germline variants in TP53 were identified as an independent risk factor (hazard ratio, 36; P < .001) for secondary leukemias. CONCLUSION: Our results suggest a close relationship between inherited variants and CH mutations within the DDR genes in patients with solid tumors. Associations identified in this study might translate into enhanced clinical surveillance for CH and associated comorbidities in patients with cancer harboring these germline mutations.

Propagation of uncertainty in Bayesian diagnostic test interpretation.

OBJECTIVES: Bayesian interpretation of diagnostic test results usually involves point estimates of the pretest probability and the likelihood ratio corresponding to the test result; however, it may be more appropriate in clinical situations to consider instead a range of possible values to express uncertainty in the estimates of these parameters. We thus sought to demonstrate how uncertainty in sensitivity, specificity, and disease pretest probability can be accommodated in Bayesian interpretation of diagnostic testing. METHODS: We investigated three questions: How does uncertainty in the likelihood ratio propagate to the posttest probability range, assuming a point estimate of pretest probability? How does uncertainty in the sensitivity and specificity of a test affect uncertainty in the likelihood ratio? How does uncertainty propagate when present in both the pretest probability and the likelihood ratio? RESULTS: Propagation of likelihood ratio uncertainty depends on the pretest probability and is more prominent for unexpected test results. Uncertainty in sensitivity and specificity propagates into the calculation of likelihood ratio prominently as these parameters approach 100%; even modest errors of ± 10% caused dramatic propagation. Combining errors of ± 20% in the pretest probability and in the likelihood ratio exhibited modest propagation to posttest probability, suggesting a realistic target range for clinical estimations. CONCLUSIONS: The results provide a framework for incorporating ranges of uncertainty into Bayesian reasoning. Although point estimates simplify the implementation of Bayesian reasoning, it is important to recognize the implications of error propagation when ranges are considered in this multistep process.

Inherited Germline Cancer Susceptibility Gene Variants in Individuals with Non-Muscle-Invasive Bladder Cancer.

PURPOSE: Identification of inherited germline variants can guide personalized cancer screening, prevention, and treatment. Pathogenic and likely pathogenic (P/LP) germline variants in cancer predisposition genes are frequent among patients with locally advanced or metastatic urothelial carcinoma, but their prevalence and significance in patients with non-muscle-invasive bladder cancer (NMIBC), the most common form of urothelial carcinoma, is understudied. EXPERIMENTAL DESIGN: Germline analysis was conducted on paired tumor/normal sequencing results from two distinct cohorts of patients initially diagnosed with NMIBC. Associations between clinicopathologic features and clinical outcomes with the presence of P/LP germline variants in ≥76 hereditary cancer predisposition genes were analyzed. RESULTS: A similar frequency of P/LP germline variants were seen in our two NMIBC cohorts [12% (12/99) vs. 8.7% (10/115), P = 0.4]. In the combined analysis, P/LP germline variants were found only in patients with high-grade NMIBC (22/163), but none of the 46 patients with low-grade NMIBC (13.5% vs. 0%, P = 0.005). Fifteen (9.2%) patients with high-grade NMIBC had P/LP variants in DNA damage response genes, most within the nucleotide excision repair (ERCC2/3) and homologous recombination repair (BRCA1, NBN, RAD50) pathways. Contrary to prior reports in patients with NMIBC not receiving Bacillus Calmette-Guerin (BCG), P/LP germline variants were not associated with worse recurrence-free or progression-free survival in patients treated with BCG or with risk of developing upper tract urothelial carcinoma. CONCLUSIONS: Our results support offering germline counseling and testing for all patients with high-grade bladder cancer, regardless of initial tumor stage. Therapeutic strategies that target impaired DNA repair may benefit patients with high-grade NMIBC.

Germline Pathogenic Variants Impact Clinicopathology of Advanced Lung Cancer.

BACKGROUND: The genetic factors that modulate risk for developing lung cancer have not been fully defined. Here, we sought to determine the prevalence and clinical significance of germline pathogenic/likely pathogenic variants (PV) in patients with advanced lung cancer. METHODS: We studied clinical and tumor characteristics of germline PV in 5,118 patients who underwent prospective genomic profiling using paired tumor-normal tissue samples in 468 cancer genes. RESULTS: Germline PV in high/moderate-penetrance genes were observed in 222 (4.3%) patients; of these, 193 patients had PV in DNA damage repair (DDR) pathway genes including BRCA2 (n = 54), CHEK2 (n = 30), and ATM (n = 26) that showed high rate of biallelic inactivation in tumors. BRCA2 heterozygotes with lung adenocarcinoma were more likely to be never smokers and had improved survival compared with noncarriers. Fourteen patients with germline PV in lung cancer predisposing genes (TP53, EGFR, BAP1, and MEN1) were diagnosed at younger age compared with noncarriers, and of tumor suppressors, 75% demonstrated biallelic inactivation in tumors. A significantly higher proportion of germline PV in high/moderate-penetrance genes were detected in high-risk patients who had either a family history of any cancer, multiple primary tumors, or early age at diagnosis compared with unselected patients (10.5% vs. 4.1%; P = 1.7e-04). CONCLUSIONS: These data underscore the biological and clinical importance of germline mutations in highly penetrant DDR genes as a risk factor for lung cancer. IMPACT: The family members of lung cancer patients harboring PV in cancer predisposing genes should be referred for genetic counseling and may benefit from proactive surveillance.

Tumor fraction-guided cell-free DNA profiling in metastatic solid tumor patients.

BACKGROUND: Cell-free DNA (cfDNA) profiling is increasingly used to guide cancer care, yet mutations are not always identified. The ability to detect somatic mutations in plasma depends on both assay sensitivity and the fraction of circulating DNA in plasma that is tumor-derived (i.e., cfDNA tumor fraction). We hypothesized that cfDNA tumor fraction could inform the interpretation of negative cfDNA results and guide the choice of subsequent assays of greater genomic breadth or depth. METHODS: Plasma samples collected from 118 metastatic cancer patients were analyzed with cf-IMPACT, a modified version of the FDA-authorized MSK-IMPACT tumor test that can detect genomic alterations in 410 cancer-associated genes. Shallow whole genome sequencing (sWGS) was also performed in the same samples to estimate cfDNA tumor fraction based on genome-wide copy number alterations using z-score statistics. Plasma samples with no somatic alterations detected by cf-IMPACT were triaged based on sWGS-estimated tumor fraction for analysis with either a less comprehensive but more sensitive assay (MSK-ACCESS) or broader whole exome sequencing (WES). RESULTS: cfDNA profiling using cf-IMPACT identified somatic mutations in 55/76 (72%) patients for whom MSK-IMPACT tumor profiling data were available. A significantly higher concordance of mutational profiles and tumor mutational burden (TMB) was observed between plasma and tumor profiling for plasma samples with a high tumor fraction (z-score≥5). In the 42 patients from whom tumor data was not available, cf-IMPACT identified mutations in 16/42 (38%). In total, cf-IMPACT analysis of plasma revealed mutations in 71/118 (60%) patients, with clinically actionable alterations identified in 30 (25%), including therapeutic targets of FDA-approved drugs. Of the 47 samples without alterations detected and low tumor fraction (z-score<5), 29 had sufficient material to be re-analyzed using a less comprehensive but more sensitive assay, MSK-ACCESS, which revealed somatic mutations in 14/29 (48%). Conversely, 5 patients without alterations detected by cf-IMPACT and with high tumor fraction (z-score≥5) were analyzed by WES, which identified mutational signatures and alterations in potential oncogenic drivers not covered by the cf-IMPACT panel. Overall, we identified mutations in 90/118 (76%) patients in the entire cohort using the three complementary plasma profiling approaches. CONCLUSIONS: cfDNA tumor fraction can inform the interpretation of negative cfDNA results and guide the selection of subsequent sequencing platforms that are most likely to identify clinically-relevant genomic alterations.

Prevalence and Characterization of Biallelic and Monoallelic NTHL1 and MSH3 Variant Carriers From a Pan-Cancer Patient Population.

NTHL1 and MSH3 have been implicated as autosomal recessive cancer predisposition genes. Although individuals with biallelic NTHL1 and MSH3 pathogenic variants (PVs) have increased cancer and polyposis risk, risks for monoallelic carriers are uncertain. We sought to assess the prevalence and characterize NTHL1 and MSH3 from a large pan-cancer patient population. MATERIALS AND METHODS: Patients with pan-cancer (n = 11,081) underwent matched tumor-normal sequencing with consent for germline analysis. Medical records and tumors were reviewed and analyzed. Prevalence of PVs was compared with reference controls (Genome Aggregation Database). RESULTS: NTHL1-PVs were identified in 40 patients including 39 monoallelic carriers (39/11,081 = 0.35%) and one with biallelic variants (1/11,081 = 0.009%) and a diagnosis of isolated early-onset breast cancer. NTHL1-associated mutational signature 30 was identified in the tumors of the biallelic patient and two carriers. Colonic polyposis was not identified in any NTHL1 patient. MSH3-PVs were identified in 13 patients, including 12 monoallelic carriers (12/11,081 = 0.11%) and one with biallelic MSH3 variants (1/11,081 = 0.009%) and diagnoses of later-onset cancers, attenuated polyposis, and abnormal MSH3-protein expression. Of the 12 MSH3 carriers, two had early-onset cancer diagnoses with tumor loss of heterozygosity of the wild-type MSH3 allele. Ancestry-specific burden tests demonstrated that NTHL1 and MSH3 prevalence was not significantly different in this pan-cancer population versus controls. CONCLUSION: NTHL1 and MSH3 germline alterations were not enriched in this pan-cancer patient population. However, tumor-specific findings, such as mutational signature 30 and loss of heterozygosity of the wild-type allele, suggest the potential contribution of monoallelic variants to tumorigenesis in a subset of patients.

A Comprehensive Comparison of Early-Onset and Average-Onset Colorectal Cancers.

BACKGROUND: The causative factors for the recent increase in early-onset colorectal cancer (EO-CRC) incidence are unknown. We sought to determine if early-onset disease is clinically or genomically distinct from average-onset colorectal cancer (AO-CRC). METHODS: Clinical, histopathologic, and genomic characteristics of EO-CRC patients (2014-2019), divided into age 35 years and younger and 36-49 years at diagnosis, were compared with AO-CRC (50 years and older). Patients with mismatch repair deficient tumors, CRC-related hereditary syndromes, and inflammatory bowel disease were excluded from all but the germline analysis. All statistical tests were 2-sided. RESULTS: In total, 759 patients with EO-CRC (35 years, n = 151; 36-49 years, n = 608) and AO-CRC (n = 687) were included. Left-sided tumors (35 years and younger = 80.8%; 36-49 years = 83.7%; AO = 63.9%; P < .001 for both comparisons), rectal bleeding (35 years and younger = 41.1%; 36-49 years = 41.0%; AO = 25.9%; P = .001 and P < .001, respectively), and abdominal pain (35 years and younger = 37.1%; 36-49 years = 34.0%; AO = 26.8%; P = .01 and P = .005, respectively) were more common in EO-CRC. Among microsatellite stable tumors, we found no differences in histopathologic tumor characteristics. Initially, differences in TP53 and Receptor Tyrosine Kinase signaling pathway (RTK-RAS)alterations were noted by age. However, on multivariate analysis including somatic gene analysis and tumor sidedness, no statistically significant differences at the gene or pathway level were demonstrated. Among advanced microsatellite stable CRCs, chemotherapy response and survival were equivalent by age cohorts. Pathogenic germline variants were identified in 23.3% of patients 35 years and younger vs 14.1% of AO-CRC (P = .01). CONCLUSIONS: EO-CRCs are more commonly left-sided and present with rectal bleeding and abdominal pain but are otherwise clinically and genomically indistinguishable from AO-CRCs. Aggressive treatment regimens based solely on the age at CRC diagnosis are not warranted.

The context-specific role of germline pathogenicity in tumorigenesis.

Human cancers arise from environmental, heritable and somatic factors, but how these mechanisms interact in tumorigenesis is poorly understood. Studying 17,152 prospectively sequenced patients with cancer, we identified pathogenic germline variants in cancer predisposition genes, and assessed their zygosity and co-occurring somatic alterations in the concomitant tumors. Two major routes to tumorigenesis were apparent. In carriers of pathogenic germline variants in high-penetrance genes (5.1% overall), lineage-dependent patterns of biallelic inactivation led to tumors exhibiting mechanism-specific somatic phenotypes and fewer additional somatic oncogenic drivers. Nevertheless, 27% of cancers in these patients, and most tumors in patients with pathogenic germline variants in lower-penetrance genes, lacked particular hallmarks of tumorigenesis associated with the germline allele. The dependence of tumors on pathogenic germline variants is variable and often dictated by both penetrance and lineage, a finding with implications for clinical management.

Enhanced specificity of clinical high-sensitivity tumor mutation profiling in cell-free DNA via paired normal sequencing using MSK-ACCESS.

Circulating cell-free DNA from blood plasma of cancer patients can be used to non-invasively interrogate somatic tumor alterations. Here we develop MSK-ACCESS (Memorial Sloan Kettering - Analysis of Circulating cfDNA to Examine Somatic Status), an NGS assay for detection of very low frequency somatic alterations in 129 genes. Analytical validation demonstrated 92% sensitivity in de-novo mutation calling down to 0.5% allele frequency and 99% for a priori mutation profiling. To evaluate the performance of MSK-ACCESS, we report results from 681 prospective blood samples that underwent clinical analysis to guide patient management. Somatic alterations are detected in 73% of the samples, 56% of which have clinically actionable alterations. The utilization of matched normal sequencing allows retention of somatic alterations while removing over 10,000 germline and clonal hematopoiesis variants. Our experience illustrates the importance of analyzing matched normal samples when interpreting cfDNA results and highlights the importance of cfDNA as a genomic profiling source for cancer patients.

Genomic Landscape of Uterine Sarcomas Defined Through Prospective Clinical Sequencing.

PURPOSE: We examined whether prospective molecular characterization of advanced metastatic disease can reveal grade and/or histology-specific differences to inform diagnosis and facilitate enrollment onto clinical trials. EXPERIMENTAL DESIGN: Patients with uterine sarcoma consented to a prospective study of next-generation sequencing (NGS). Clinical annotations were extracted from their medical record. Tumor and matched normal DNA were subjected to NGS, and the genomic landscape was explored for survival correlations and therapeutic targetability. RESULTS: Tumors from 107 women were sequenced and included leiomyosarcoma (n = 80), high-grade non-leiomyosarcoma (n = 22), low-grade endometrial stromal sarcoma (LG-ESS, n = 4), and smooth muscle tumor of uncertain malignant potential (STUMP, n = 2). Genomic profiling influenced histologic diagnosis in three cases. Common uterine leiomyosarcoma alterations were loss-of-function mutations in TP53 (56%), RB1 (51%), and ATRX (31%). Homozygous deletions of BRCA2 were present in 5% of these patients. PTEN alteration frequency was higher in the metastases samples as compared with the primary samples. Genomes of low-grade tumors were largely silent, while 50.5% of high-grade tumors had whole-genome duplication. Two metastatic uterine leiomyosarcoma cases were hypermutated. Both had prolonged disease-free survival. Potentially actionable mutations were identified in 48 patients (45%), 8 (17%) of whom received matched therapy with 2 achieving clinical responses. Among patients with uterine leiomyosarcoma with somatic BRCA2 alterations, sustained partial responses were observed with PARP inhibitor-containing therapy. DISCUSSION: Prospective genomic profiling can contribute to diagnostic precision and inform treatment selection in patients with uterine sarcomas. There was evidence of clinical benefit in patients with uterine leiomyosarcoma with somatic BRCA2 alterations treated with PARP inhibitors.

Understanding inherited risk in unselected newly diagnosed patients with endometrial cancer.

PURPOSE: Mutations in DNA mismatch repair (MMR) genes and PTEN, diagnostic of Lynch and Cowden syndromes, respectively, represent the only established inherited predisposition genes in endometrial cancer to date. The prevalence of other cancer predisposition genes remains unclear. We sought the prevalence of pathogenic germline variants in unselected patients with endometrial cancer attending for surgical consultation. PATIENTS AND METHODS: Patients were prospectively consented (4/2016-5/2017) to an IRB-approved protocol of tumor-normal sequencing via a custom next-generation sequencing panel (MSK-IMPACT) with return of germline results for >75 cancer predisposition genes. Tumors were assessed for microsatellite instability (MSI). Per institutional standards, all tumors underwent Lynch syndrome screening via IHC for MMR proteins. RESULTS: Of 156 patients who consented to germline genetic testing, 118 (76%) had stage I disease. Tumors were endometrioid in 104 (67%), of which 60 (58%) were grade 1. Twenty-four pathogenic germline variants were identified in 22 patients (14%)-7 (4.5%) with highly penetrant cancer syndromes and 15 (9.6%) with variants in moderate-, low-penetrance, or recessive genes. Of these, 5 (21%) were in Lynch syndrome genes (2 MSH6, 2 PMS2, and 1 MLH1). All 5 tumors had concordant IHC staining; 2 (40%) were definitively MSI-high by next-generation sequencing. One patient had a known BRCA1 mutation; 1 had SMARCA4 deletion. The remaining 17 variants (71%) were incremental findings in moderate- and low-penetrance variants or genes associated with recessive disease. CONCLUSION: In unselected patients with predominantly low-risk, early-stage endometrial cancer, germline multi-gene panel testing identifies cancer predisposition gene variants in 14%. This finding may have implications for future cancer screening and risk-reduction recommendations. Universal IHC screening for Lynch syndrome successfully identifies the majority (71%) of high-penetrance germline mutations.

Analysis of the Prevalence of Microsatellite Instability in Prostate Cancer and Response to Immune Checkpoint Blockade.

IMPORTANCE: The anti-programmed cell death protein 1 (PD-1) antibody pembrolizumab is approved by the US Food and Drug Administration for the treatment of microsatellite instability-high (MSI-H) or mismatch repair-deficient (dMMR) solid tumors, but the prevalence of MSI-H/dMMR prostate cancer and the clinical utility of immune checkpoint blockade in this disease subset are unknown. OBJECTIVE: To define the prevalence of MSI-H/dMMR prostate cancer and the clinical benefit of anti-PD-1/programmed cell death 1 ligand 1 (PD-L1) therapy in this molecularly defined population. DESIGN, SETTING, AND PARTICIPANTS: In this case series, 1551 tumors from 1346 patients with prostate cancer undergoing treatment at Memorial Sloan Kettering Cancer Center were prospectively analyzed using a targeted sequencing assay from January 1, 2015, through January 31, 2018. Patients had a diagnosis of prostate cancer and consented to tumor molecular profiling when a tumor biopsy was planned or archival tissue was available. For each patient, clinical outcomes were reported, with follow-up until May 31, 2018. MAIN OUTCOMES AND MEASURES: Tumor mutation burden and MSIsensor score, a quantitative measure of MSI, were calculated. Mutational signature analysis and immunohistochemistry for MMR protein expression were performed in select cases. RESULTS: Among the 1033 patients who had adequate tumor quality for MSIsensor analysis (mean [SD] age, 65.6 [9.3] years), 32 (3.1%) had MSI-H/dMMR prostate cancer. Twenty-three of 1033 patients (2.2%) had tumors with high MSIsensor scores, and an additional 9 had indeterminate scores with evidence of dMMR. Seven of the 32 MSI-H/dMMR patients (21.9%) had a pathogenic germline mutation in a Lynch syndrome-associated gene. Six patients had more than 1 tumor analyzed, 2 of whom displayed an acquired MSI-H phenotype later in their disease course. Eleven patients with MSI-H/dMMR castration-resistant prostate cancer received anti-PD-1/PD-L1 therapy. Six of these (54.5%) had a greater than 50% decline in prostate-specific antigen levels, 4 of whom had radiographic responses. As of May 2018, 5 of the 6 responders (5 of 11 total [45.5%]) were still on therapy for as long as 89 weeks. CONCLUSIONS AND RELEVANCE: The MSI-H/dMMR molecular phenotype is uncommon yet therapeutically meaningful in prostate cancer and can be somatically acquired during disease evolution. Given the potential for durable responses to anti-PD-1/PD-L1 therapy, these findings support the use of prospective tumor sequencing to screen all patients with advanced prostate cancer for MSI-H/dMMR. Because not all patients with the MSI-H/dMMR phenotype respond, further studies should explore mechanisms of resistance.

Microsatellite Instability Is Associated With the Presence of Lynch Syndrome Pan-Cancer.

PURPOSE: Microsatellite instability (MSI) and/or mismatch repair deficiency (MMR-D) testing has traditionally been performed in patients with colorectal (CRC) and endometrial cancer (EC) to screen for Lynch syndrome (LS)-associated cancer predisposition. The recent success of immunotherapy in high-frequency MSI (MSI-H) and/or MMR-D tumors now supports testing for MSI in all advanced solid tumors. The extent to which LS accounts for MSI-H across heterogeneous tumor types is unknown. Here, we establish the prevalence of LS across solid tumors according to MSI status. METHODS: MSI status was determined using targeted next-generation sequencing, with tumors classified as MSI-H, MSI-indeterminate, or microsatellite-stable. Matched germline DNA was analyzed for mutations in LS-associated mismatch repair genes ( MLH1, MSH2, MSH6, PMS2, EPCAM). In patients with LS with MSI-H/I tumors, immunohistochemical staining for MMR-D was assessed. RESULTS: Among 15,045 unique patients (more than 50 cancer types), LS was identified in 16.3% (53 of 326), 1.9% (13 of 699), and 0.3% (37 of 14,020) of patients with MSI-H, MSI-indeterminate, and microsatellite-stable tumors, respectively ( P < .001). Among patients with LS with MSI-H/I tumors, 50% (33 of 66) had tumors other than CRC/EC, including urothelial, prostate, pancreas, adrenocortical, small bowel, sarcoma, mesothelioma, melanoma, gastric, and germ cell tumors. In these patients with non-CRC/EC tumors, 45% (15 of 33) did not meet LS genetic testing criteria on the basis of personal/family history. Immunohistochemical staining of LS-positive MSI-H/I tumors demonstrated MMR-D in 98.2% (56 of 57) of available cases. CONCLUSION: MSI-H/MMR-D is predictive of LS across a much broader tumor spectrum than currently appreciated. Given implications for cancer surveillance and prevention measures in affected families, these data support germline genetic assessment for LS for patients with an MSI-H/MMR-D tumor, regardless of cancer type or family cancer history.

Clinical Utility of Prospective Molecular Characterization in Advanced Endometrial Cancer.

PURPOSE: Advanced-stage endometrial cancers have limited treatment options and poor prognosis, highlighting the need to understand genetic drivers of therapeutic vulnerabilities and/or prognostic predictors. We examined whether prospective molecular characterization of recurrent and metastatic disease can reveal grade and histology-specific differences, facilitating enrollment onto clinical trials. EXPERIMENTAL DESIGN: We integrated prospective clinical sequencing and IHC data with detailed clinical and treatment histories for 197 tumors, profiled by MSK-IMPACT from 189 patients treated at Memorial Sloan Kettering Cancer Center. RESULTS: Patients had advanced disease and high-grade histologies, with poor progression-free survival on first-line therapy (PFS1). When matched for histology and grade, the genomic landscape was similar to that of primary untreated disease profiled by TCGA. Using multiple complementary genomic and mutational signature-based methods, we identified patients with microsatellite instability (MSI), even when standard MMR protein IHC staining failed. Tumor and matched normal DNA sequencing identified rare pathogenic germline mutations in BRCA2 and MLH1. Clustering the pattern of DNA copy-number alterations revealed a novel subset characterized by heterozygous losses across the genome and significantly worse outcomes compared with other clusters (median PFS1 9.6 months vs. 17.0 and 17.4 months; P = 0.006). Of the 68% of patients harboring potentially actionable mutations, 27% were enrolled to matched clinical trials, of which 47% of these achieved clinical benefit. CONCLUSIONS: Prospective clinical sequencing of advanced endometrial cancer can help refine prognosis and aid treatment decision making by simultaneously detecting microsatellite status, germline predisposition syndromes, and potentially actionable mutations. A small overall proportion of all patients tested received investigational, genomically matched therapy as part of clinical trials.