Using genome and transcriptome data from African-ancestry female participants to identify putative breast cancer susceptibility genes

African-ancestry (AA) participants are underrepresented in genetics research. Here, we conducted a transcriptome-wide association study (TWAS) in AA female participants to identify putative breast cancer susceptibility genes. We built genetic models to predict levels of gene expression, exon junction, and 3' UTR alternative polyadenylation using genomic and transcriptomic data generated in normal breast tissues from 150 AA participants and then used these models to perform association analyses using genomic data from 18,034 cases and 22,104 controls. At Bonferroni-corrected P < 0.05, we identified six genes associated with breast cancer risk, including four genes not previously reported (CTD-3080P12.3, EN1, LINC01956 and NUP210L). Most of these genes showed a stronger association with risk of estrogen-receptor (ER) negative or triple-negative than ER-positive breast cancer. We also replicated the associations with 29 genes reported in previous TWAS at P < 0.05 (one-sided), providing further support for an association of these genes with breast cancer risk. Our study sheds new light on the genetic basis of breast cancer and highlights the value of conducting research in AA populations.

The Clinical Implications of Reversions in Patients with Advanced Pancreatic Cancer and Pathogenic Variants in BRCA1, BRCA2, or PALB2 after Progression on Rucaparib

PURPOSE

PARP inhibitors (PARPi) provide an effective maintenance option for patients with BRCA- or PALB2-mutated pancreatic cancer. However, mechanisms of PARPi resistance and optimal post-PARPi therapeutic strategies are poorly characterized.

EXPERIMENTAL DESIGN

We collected paired cell-free DNA samples and post-PARPi clinical data on 42 patients with advanced, platinum-sensitive pancreatic cancer who were treated with maintenance rucaparib on NCT03140670, of whom 32 developed progressive disease.

RESULTS

Peripherally detected, acquired BRCA or PALB2 reversion variants were uncommon (5/30; 16.6%) in patients who progressed on rucaparib. Reversions were significantly associated with rapid resistance to PARPi treatment (median PFS, 3.7 vs. 12.5 months; P = 0.001) and poor overall survival (median OS, 6.2 vs. 23.0 months; P < 0.0001). All patients with reversions received rechallenge with platinum-based chemotherapy following PARPi progression and experienced faster progression on this therapy than those without reversion variants (real-world time-to-treatment discontinuation, 2.4 vs. 5.8 months; P = 0.004). Of the patients who progressed on PARPi and received further chemotherapy, the OS from initiation of second-line therapy was significantly lower in those with reversion variants than in those without (5.5 vs. 12.0 months, P = 0.002). Finally, high levels of tumor shedding were independently associated with poor outcomes in patients who received rucaparib.

CONCLUSIONS

Acquired reversion variants were uncommon but detrimental in a population of patients with advanced BRCA- or PALB2-related pancreatic ductal adenocarcinoma who received maintenance rucaparib. Reversion variants led to rapid progression on PARPi, rapid failure of subsequent platinum-based treatment, and poor OS of patients. The identification of such variants in the blood may have both predictive and prognostic value. See related commentary by Tsang and Gallinger, p. 5005.

ENIGMA CHEK2gether Project: A Comprehensive Study Identifies Functionally Impaired CHEK2 Germline Missense Variants Associated with Increased Breast Cancer Risk

PURPOSE

Germline pathogenic variants in CHEK2 confer moderately elevated breast cancer risk (odds ratio, OR ∼ 2.5), qualifying carriers for enhanced breast cancer screening. Besides pathogenic variants, dozens of missense CHEK2 variants of uncertain significance (VUS) have been identified, hampering the clinical utility of germline genetic testing (GGT).

EXPERIMENTAL DESIGN

We collected 460 CHEK2 missense VUS identified by the ENIGMA consortium in 15 countries. Their functional characterization was performed using CHEK2-complementation assays quantifying KAP1 phosphorylation and CHK2 autophosphorylation in human RPE1-CHEK2-knockout cells. Concordant results in both functional assays were used to categorize CHEK2 VUS from 12 ENIGMA case-control datasets, including 73,048 female patients with breast cancer and 88,658 ethnicity-matched controls.

RESULTS

A total of 430/460 VUS were successfully analyzed, of which 340 (79.1%) were concordant in both functional assays and categorized as functionally impaired (N = 102), functionally intermediate (N = 12), or functionally wild-type (WT)-like (N = 226). We then examined their association with breast cancer risk in the case-control analysis. The OR and 95% CI (confidence intervals) for carriers of functionally impaired, intermediate, and WT-like variants were 2.83 (95% CI, 2.35-3.41), 1.57 (95% CI, 1.41-1.75), and 1.19 (95% CI, 1.08-1.31), respectively. The meta-analysis of population-specific datasets showed similar results.

CONCLUSIONS

We determined the functional consequences for the majority of CHEK2 missense VUS found in patients with breast cancer (3,660/4,436; 82.5%). Carriers of functionally impaired missense variants accounted for 0.5% of patients with breast cancer and were associated with a moderate risk similar to that of truncating CHEK2 variants. In contrast, 2.2% of all patients with breast cancer carried functionally wild-type/intermediate missense variants with no clinically relevant breast cancer risk in heterozygous carriers.

ERK Hyperactivation Serves as a Unified Mechanism of Escape in Intrinsic and Acquired CDK4/6 Inhibitor Resistance in Acral Lentiginous Melanoma

Patients with metastatic acral lentiginous melanoma (ALM) suffer worse outcomes relative to patients with other forms of cutaneous melanoma (CM), and do not benefit as well to approved melanoma therapies. Identification of cyclin-dependent kinase 4 and 6 (CDK4/6) pathway gene alterations in > 60% of ALMs has led to clinical trials of the CDK4/6 inhibitor (CDK4i/6i) palbociclib for ALM; however, median progression free survival with CDK4i/6i treatment was only 2.2 months, suggesting existence of resistance mechanisms. Therapy resistance in ALM remains poorly understood; here we report hyperactivation of MAPK signaling and elevated cyclin D1 expression are a unified mechanism of both intrinsic and acquired CDK4i/6i resistance. MEK and/or ERK inhibition increases CDK4i/6i efficacy in a patient-derived xenograft (PDX) model of ALM and promotes a defective DNA repair, cell cycle arrested and apoptotic program. Notably, gene alterations poorly correlate with protein expression of cell cycle proteins in ALM or efficacy of CDK4i/6i, urging additional strategies when stratifying patients for CDK4i/6i trial inclusion. Concurrent targeting of the MAPK pathway and CDK4/6 represents a new approach to improve outcomes for patients with advanced ALM.

The identification of reversion mutations in patients with advanced pancreatic cancer and germline or somatic BRCA or PALB2 variants who were treated with maintenance rucaparib

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Background: Maintenance PARP inhibition (PARPi) extends progression-free survival and improves quality of life for patients (pts) with advanced, platinum-sensitive pancreatic cancer (PC) and BRCA or PALB2 variants. However, most will experience progression. PARPi resistance mechanisms are poorly defined in PC. Cell-free (cf)DNA analysis can detect some known classes of resistance mechanisms, like reversion mutations, and other potentially prognostic and predictive genomic features. Methods: Pts with advanced, platinum-sensitive pancreatic cancer and pathogenic germline or somatic BRCA1, BRCA2, or PALB2 variants were treated with maintenance rucaparib on clinical trial. cfDNA was collected at baseline and progression and analyzed with the GuardantOMNI 500-gene liquid biopsy. Time to event analysis was performed from index date of enrollment until endpoint (PFS, OS, and PFS2). Associations were tested by the log-rank test with adjustment. Results: The trial enrolled 42 pts, of whom 31 have progressed. cfDNA was available for 41 pts at baseline and 30 pts at progression; 88% had baseline detectable cfDNA. Two pts had baseline reversion mutations, 5 had new reversion mutations at progression. Of 21 pts who had tissue NGS, 17 pts had a KRAS variant in the tumor, 12 of whom had detectable cfDNA at either baseline or progression. Of the 41 patients with cfDNA samples, 10 pts had baseline KRAS mutations detected in plasma; an additional 10 pts had a detectable plasma KRAS mutation at progression. Outcomes are shown. Of those who had progressed, pts with acquired reversion mutations had shorter OS (p<0.001) and PFS (p = 0.018) on rucaparib than those without reversion mutations. Of those who received chemo after progression (n=23), PFS2 was shorter for pts with acquired reversions compared to those with no reversions (p = 0.038). KRAS mutation detection at baseline was observed with higher overall somatic allele fraction in cfDNA and a trend toward shorter PFS and OS. Conclusions: Acquired reversion mutations were infrequent but associated with worse outcomes. Other causes of resistance may be dominant. Detection of KRAS mutation in the peripheral blood may be associated with disease burden and clinical outcome. [Table: see text]

Dasatinib Resensitizes MAPK Inhibitor Efficacy in Standard-of-Care Relapsed Melanomas

Resistance to combination BRAF/MEK inhibitor (BRAFi/MEKi) therapy arises in nearly every patient with BRAFV600E/K melanoma, despite promising initial responses. Achieving cures in this expanding BRAFi/MEKi-resistant cohort represents one of the greatest challenges to the field; few experience additional durable benefit from immunotherapy and no alternative therapies exist. To better personalize therapy in cancer patients to address therapy relapse, umbrella trials have been initiated whereby genomic sequencing of a panel of potentially actionable targets guide therapy selection for patients; however, the superior efficacy of such approaches remains to be seen. We here test the robustness of the umbrella trial rationale by analyzing relationships between genomic status of a gene and the downstream consequences at the protein level of related pathway, which find poor relationships between mutations, copy number amplification, and protein level. To profile candidate therapeutic strategies that may offer clinical benefit in the context of acquired BRAFi/MEKi resistance, we established a repository of patient-derived xenograft models from heavily pretreated patients with resistance to BRAFi/MEKi and/or immunotherapy (R-PDX). With these R-PDXs, we executed in vivo compound repurposing screens using 11 FDA-approved agents from an NCI-portfolio with pan-RTK, non-RTK and/or PI3K-mTOR specificity. We identify dasatinib as capable of restoring BRAFi/MEKi antitumor efficacy in ~70% of R-PDX tested. A systems-biology analysis indicates elevated baseline protein expression of canonical drivers of therapy resistance (e.g., AXL, YAP, HSP70, phospho-AKT) as predictive of MAPKi/dasatinib sensitivity. We therefore propose that dasatinib-based MAPKi therapy may restore antitumor efficacy in patients that have relapsed to standard-of-care therapy by broadly targeting proteins critical in melanoma therapy escape. Further, we submit that this experimental PDX paradigm could potentially improve preclinical evaluation of therapeutic modalities and augment our ability to identify biomarker-defined patient subsets that may respond to a given clinical trial.

Challenges and Opportunities in Engaging Primary Care Providers in BRCA Testing: Results from the BFOR Study

PURPOSE

Engaging primary care providers (PCPs) in BRCA1/2 testing and results disclosure would increase testing access. The BRCA Founder OutReach (BFOR) study is a prospective study of BRCA1/2 founder mutation screening among individuals of Ashkenazi Jewish descent that sought to involve participants' PCPs in results disclosure. We used quantitative and qualitative methods to evaluate PCPs' perspectives, knowledge, and experience disclosing results in BFOR.

METHODS

Among PCPs nominated by BFOR participants to disclose BRCA1/2 results, we assessed the proportion agreeing to disclose. To examine PCP's perspectives, knowledge, and willingness to disclose results, we surveyed 501 nominated PCPs. To examine PCPs' experiences disclosing results in BFOR, we surveyed 101 PCPs and conducted 10 semi-structured interviews.

RESULTS

In the BFOR study overall, PCPs agreed to disclose their patient's results 40.5% of the time. Two hundred thirty-four PCPs (46.7%) responded to the initial survey. Responding PCPs were more likely to agree to disclose patients' results than non-responders (57.3% vs. 28.6%, p<0.001). Among all respondents, most felt very (19.7%) or somewhat (39.1%) qualified to share results. Among PCPs declining to disclose, insufficient knowledge was the most common reason. In multivariable logistic regression, feeling qualified was the only variable significantly associated with agreeing to disclose results (OR 6.53, 95% CI 3.31, 12.88). In post-disclosure surveys (response rate=55%), PCPs reported largely positive experiences. Interview findings suggested that although PCPs valued the study-provided educational materials, they desired better integration of results and decision support into workflows.

CONCLUSION

Barriers exist to incorporating BRCA1/2 testing into primary care. Most PCPs declined to disclose their patients' BFOR results, although survey respondents were motivated and had positive disclosure experiences. PCP training and integrated decision support could be beneficial.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT03351803), November 24, 2017.

Abstract 1352: Genetic susceptibility to immune-related adverse events among melanoma patients treated with ipilimumab

Background: Ipilimumab is an immune checkpoint inhibitor used to treat melanoma. Although the development of immune-related adverse events (irAEs) among patients treated with ipilimumab is well documented, little is known about factors that may increase risk of irAEs. We conducted a genome-wide association study (GWAS) to examine the genetic susceptibility to irAEs in response to ipilimumab monotherapy.

Methods: In partnership with Bristol Myers Squibb BMS, extant genotype data and clinical information were obtained on melanoma patients treated with ipilimumab monotherapy from three clinical trials. Only patients who were treatment naïve were included in our analyses. We defined our outcome as the occurrence of a serious irAE, grade 3 or higher. We first analyzed data from 294 subjects, 79 with severe irAE, enrolled on CA184-169 for whom genotyping was completed using the Affymetrix 6 array. After appropriate quality control, SNP associations were determined using logistic regression models that were adjusted for ancestry, ECOG status, ipilimumab dosage (3 mg/kg vs 10 mg/kg), and number of doses (&lt;4 vs 4+). Next, we analyzed data from 175 subjects, 63 with severe irAE, enrolled on CA209-067 or CA209-069 for whom genotyping was completed using the Illumina MegaEX array; and SNP associations were similarly determined after adjustment for ancestry, trial, and number of doses (&lt;4 vs 4+). Summary statistics from the two analyses were combined using a fixed-effect meta-analysis. Because of the small sample size, we used a sub-genome-wide significance level of 1 × 10-5 to indicate potentially important findings.

Results: The most statistically significant marker (rs55981606, p=1.39 × 10-7) and a second independent marker (rs72712605, p=6.33 × 10-6) mapped to a non-coding region on chromosome 9. We identified a marker (rs65949485, p = 9.38 × 10-6) intragenic between the SHQ1 and GXYLT2 genes, both of which are involved in the Notch signaling pathway. Markers proximal to NR2F2 (rs13270533, p=7.8 × 10-6) and within SAMD12 (rs13270533, p = 9.23 × 10-6) were also identified; the latter two genes have been implicated as being oncogenic. Additionally, we identified several markers implicating genes involved in inflammation, specifically macrophage activation, including TLE1 (rs3739581, p = 9.25 × 10-7), SLC16A4 (rs2271885, p=9.23 × 10-6) and CYP2J2 (rs427970, p=2.03 × 10-6).

Conclusions: Results from our meta-analysis suggest that genes related to inflammation processes and those with known contributions to oncogenesis may play a role in the development of severe irAEs resulting from ipilimumab monotherapy. If further validated, these findings may provide the foundation to advance models to discriminate patients with a high likelihood of suffering irAE allowing for heightened surveillance of symptom onset or joint decision making for alternative therapies.

Citation Format: John Pluta, Lu Qian, Kurt D'Andrea, Chunzhe Duan, Benita Weathers, Megan Wind-Rotolo, Peter Kanetsky, Katherine Nathanson. Genetic susceptibility to immune-related adverse events among melanoma patients treated with ipilimumab [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1352.

Evolution of delayed resistance to immunotherapy in a melanoma responder

Despite initial responses1-3, most melanoma patients develop resistance4 to immune checkpoint blockade (ICB). To understand the evolution of resistance, we studied 37 tumor samples over 9 years from a patient with metastatic melanoma with complete clinical response to ICB followed by delayed recurrence and death. Phylogenetic analysis revealed co-evolution of seven lineages with multiple convergent, but independent resistance-associated alterations. All recurrent tumors emerged from a lineage characterized by loss of chromosome 15q, with post-treatment clones acquiring additional genomic driver events. Deconvolution of bulk RNA sequencing and highly multiplexed immunofluorescence (t-CyCIF) revealed differences in immune composition among different lineages. Imaging revealed a vasculogenic mimicry phenotype in NGFRhi tumor cells with high PD-L1 expression in close proximity to immune cells. Rapid autopsy demonstrated two distinct NGFR spatial patterns with high polarity and proximity to immune cells in subcutaneous tumors versus a diffuse spatial pattern in lung tumors, suggesting different roles of this neural-crest-like program in different tumor microenvironments. Broadly, this study establishes a high-resolution map of the evolutionary dynamics of resistance to ICB, characterizes a de-differentiated neural-crest tumor population in melanoma immunotherapy resistance and describes site-specific differences in tumor-immune interactions via longitudinal analysis of a patient with melanoma with an unusual clinical course.

Phase II Study of Maintenance Rucaparib in Patients With Platinum-Sensitive Advanced Pancreatic Cancer and a Pathogenic Germline or Somatic Variant in BRCA1, BRCA2, or PALB2

PURPOSE

Olaparib, a poly (ADP-ribose) polymerase (PARP) inhibitor (PARPi), is approved as maintenance therapy for patients with advanced pancreatic cancer (PC) and a germline BRCA1 or BRCA2 pathogenic variant (PV). This investigator-initiated, single-arm phase II study assessed the role of the PARPi rucaparib as maintenance therapy in advanced PC with germline or somatic PV in BRCA1, BRCA2, or PALB2.

PATIENTS AND METHODS

Eligible patients had advanced PC; germline (g) or somatic (s) PVs in BRCA1, BRCA2, or PALB2, and received at least 16 weeks of platinum-based chemotherapy without evidence of platinum resistance. Chemotherapy was discontinued and patients received rucaparib 600 mg orally twice a day until progression. The primary end point was the progression-free survival (PFS) rate at 6 months (PFS6). Secondary end points included safety, ORR, disease control rate, duration of response, and overall survival.

RESULTS

Of 46 enrolled patients, 42 were evaluable (27 gBRCA2, seven gBRCA1, six gPALB2, and two sBRCA2). PFS6 was 59.5% (95% CI, 44.6 to 74.4), median PFS was 13.1 months (95% CI, 4.4 to 21.8), and median overall survival was 23.5 months (95% CI, 20 to 27). The PFS at 12 months was 54.8%. ORR of the 36 patients with measurable disease was 41.7% (3 complete responses; 12 partial responses; 95% CI, 25.5 to 59.2), and disease control rate was 66.7% (95% CI, 49.0 to 81.4). Median duration of response was 17.3 months (95% CI, 8.8 to 25.8). Responses occurred in patients with gBRCA2 (41%, 11 out of 27), gPALB2 (50%, 3 out of 6), and sBRCA2 (50%, 1 out of 2). No new safety signals were noted.

CONCLUSION

Maintenance rucaparib is a safe and effective therapy for platinum-sensitive, advanced PC with a PV in BRCA1, BRCA2, or PALB2. The finding of efficacy in patients with gPALB2 and sBRCA2 PVs expands the population likely to benefit from PARPi beyond gBRCA1/2 PV carriers.

Abstract 1203: Identification of 22 novel loci associated with susceptibility to testicular germ cell tumors

Background: Testicular germ cell tumors (TGCT) are the most common cancers in young men of European ancestry aged 20 to 39 years. The incidence of TGCT has doubled over the past 20 years, yet no robust environmental risk factors for disease have been identified. Although TGCTs are treatable by surgery, radiation, and platinum-based chemotherapy, multiple long-term toxicities of treatment often occur impacting morbidity and mortality. Due to their high heritability and homogenous cell of origin, TGCTs are well suited to genome-wide association methods. The Testicular Cancer Consortium (TECAC) has brought together the largest genome-wise association study (GWAS) study of TGCT to date.

Methods: We conducted a GWAS of 5,602 cases and 5,006 controls aggregated from 12 locations in the US and Europe. Logistic regression models adjusted for study center and genomic ancestry. Genotypes were imputed against the Human Haplotype Reference Consortium. Meta-analysis was performed to combine GWAS results with summary statistics from five previously published TGCT studies, UK Biobank, deCODE Genetics, and an independent set of cases and controls, for a total of 10,156 cases and 179,683 controls. Biologic function of loci was explored using PAINTOR annotated with ATAC-seq data of four TGCT cell lines, SPATIAL-seq data of the NTERA2 TGCT cell-line, and publicly available data from ENCODE. Polygenic risk scores (PRS) were computed using subject-level data from the 5,602 cases and 5,006 controls, and effect sizes of the novel hits derived from the meta-analysis.

Results: 22 novel and 45 previously reported loci associated with TGCT surpassed genome-wide significance (p &lt; 5e-08). We discovered additional markers in known susceptibility loci and identified novel regions associated with germ cell development and sex determination (e.g., BCL11, AR), immune function (e.g., TNXB, ITIH5), and for the first time identified genes associated with kinetochore activity (e.g., PPP2R5A, ANAPC2). All identified risk SNPs to date account for 42.3% of heritability. Men in the highest 1% of PRS had over a 15-fold increased risk of TGCT compared to those at the median PRS, and PRS overall had an AUC of 74.29%.

Conclusions: Results from our TGCT meta-analysis continue to provide insights into biological pathways affecting germ cell specification, expression, and epigenetic reprogramming, and sex determination. Our results also uniquely place TGCT as the only cancer type in which inherited variants implicating kinetochore activity, critical for chromosomal segregation, have been identified.

Citation Format: John Pluta, Louisa Pyle, Timothy Bishop, Javier Benitez, Victoria Cortessis, Alberto Ferlin, Jourik Gietema, Mark Greene, Thomas Grotmol, Ramneek Gupta, Robert Hamilton, Michelle Hildebrandt, Lambertus Kiemeney, Davor Lessel, Thorunn Rafnar, Lorenzo Richiardi, Rolf Skotheim, Clare Turnbull, Fredrik Wiklund, Tongzhang Zheng, Ewa Rajpert- De Meyts, Stephen Schwartz, Katherine McGlynn, Peter Kanetsky, Katherine Nathanson. Identification of 22 novel loci associated with susceptibility to testicular germ cell tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1203.

Tumor detection rates in screening carriers with SDHx-related hereditary paraganglioma-pheochromocytoma syndrome based on prior tumor history

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Background: Patients with germline pathogenic variants (PVs) in the SDHx genes have increased risk for paragangliomas/pheochromocytomas (PGL/PCC), renal cell carcinomas, and gastrointestinal stromal tumors. Expert recommendation suggests individuals with SDHx PVs undergo biennial whole-body imaging and annual biochemical testing. This study aimed to evaluate tumor detection rate using standard biochemical and imaging protocols for individuals with SDHx PVs, particularly in those with and without SDHx-related tumor history, and in those with biochemical testing data. Methods: A retrospective longitudinal observational study at the Universities of Michigan, Pennsylvania, and Utah Huntsman Cancer Institute was conducted from the start of each center’s screening program through March 1, 2018. Individuals with SDHx PVs had clinical imaging with whole body MRI/CT and biochemical testing per expert recommendation. SDHx-related tumors identified during clinical screening were measured. Results: A total of 263 individuals with SDHx PVs completed 491 screens. Individuals with SDHB PVs were the most prevalent (n = 188, 71.5%). The average number of screens per subject was 1.87 (range 1-7). A majority (n = 194, 73.7%) of individuals did not have a prior history of PGL/PCC. Overall, SDHx-related tumors were detected in 17.1% (n = 45) of the cohort. Of the 46 scans that identified an SDHx-related tumor, 85% of them (n = 39) were baseline scans. SDHx-related tumors were identified in 18.6% (n = 36/194) of individuals that did not have a prior history of PGL/PCC, whereas they were identified in 13.0% (n = 9/69) of individuals that did have a prior history of PGL/PCC (p = 0.39). Biochemical testing was available for 70% (n = 343) of imaging screens, of which 18% (n = 61) had positive biochemistry. Of those with positive biochemistry, 19 tumors were identified on imaging (6%). Sixteen tumors were identified on imaging with negative biochemistry (5%) with a sensitivity of 54% and a specificity of 94%. Utilizing a cut-off of two times the upper limit of normal, 9.91% (n = 34) biochemical tests were positive, and 15 (44.12%) had an SDHx-related tumor on corresponding imaging. Conclusions: Current SDHx screening protocols are effective at identifying SDHx-related tumors. Tumors were detected in subjects with a prior history of PGL/PCC and those with no prior history. This suggests life-long screening is important for all SDHx carriers. Imaging is a crucial piece of SDHx screening given biochemical testing’s sensitivity and specificity.

The BRCA founder outreach study: Initial results of a digital health model

2007

Background: NCCN now endorses BRCA founder mutation genetic testing (GT) via longitudinal studies in all Ashkenazi Jewish (AJ) individuals. The BRCA Founder OutReach (BFOR) study offers pre-GT online education with posttest engagement of primary care providers (PCPs). Methods: The study in 4 US cities enrolls those age > 25 with > 1 AJ grandparent. Participants enroll online with chatbot and video education, have GT at local centers, receive results from their PCP or BFOR staff, and are surveyed 12 weeks post disclosure and annually for 5 years. Univariate analyses and multivariable (MV) logistic regression models were used to evaluate characteristics associated with not completing GT, selecting PCP to disclose GT, and positive GT. Results: As of January 2020, 4754 participants consented (77.5% female, median age 51); 37.7% never previously considered GT. Cancer family histories (FHx) were 56.4% low risk (LR), 36.4% high risk (HR), and 7.2% had a familial mutation (FM). To date, 3658 participants (76.9%) completed and 677 (14.2%) did not complete GT; the remainder are pending. Only 34.8% of participants selected PCP to disclose GT, and 42.6% of PCPs agreed. Of the 124 mutation carriers (3.4%) identified, 60.5% had a FM. At the 12-week survey, 65.4% of mutation carriers planned to proceed with recommended screening or scheduled risk reducing surgery; 3.5% of those with negative GT and HR FHx reported further GT. Satisfaction was high (mean 9.58/10, SD 1.12) and unrelated to result (p>.05). Conclusions: A digital model for founder mutation testing engaged those with LR FHx and no prior experience with GT. Older participants were more likely to complete the study. Males were less likely to enroll but more likely to carry mutations. The majority of those who tested positive had a FM. A minority of results were disclosed by PCPs. Continued follow up is needed to determine long term outcomes. [Table: see text]

Genetic risk assessment for hereditary RCC: Report from the consensus panel meeting

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Background: While many genes are now known to be associated with hereditary kidney cancer syndromes, there is a paucity of guidelines or uniform consensus on genetic testing for these patients. An expert panel was organized to assess who, what, when and how patients should be evaluated and what testing should be initiated. Methods: A national, multidisciplinary, panel of experts in urology, medical oncology, clinical geneticists, genetic counselors and patient advocates with background and knowledge in hereditary syndromic kidney cancer convened in person in September 2019. A renal cell carcinoma (RCC) genetic risk assessment questionnaire consisting of 52 questions was compiled prior to the meeting using modified Delphi methodology. The questions were then discussed and reviewed with uniform consensus defined as a minimum of 85% agreement in accordance with the National Comprehensive Cancer Network criteria. Results: The panel consisted of twenty-six attendees represented by urologists (43%), medical oncologist (23%), genetic counselors (13%), clinical geneticists (7%), and patient advocates (3%). The questionnaire consisted of fifty-five statements focusing on who, what, when and how genetic testing should be performed in a patient suspected of hereditary RCC syndrome. A >85% agreement was reached on 30/52 statements with 18/25 (72%) achieving consensus addressing “who”, 2/6 (33%) achieving consensus in “what’ category, 2/7 (29%) in ‘when’ and 4/6 (67%) on how. The questions with least consensus were found in the “what/when?” category with only 4/13 questions with minimum 85% agreement. Specific areas of debate included an age cutoff for prompting a genetic risk assessment as well as need for familial testing in patients with variants of unknown significance. Conclusions: Despite experience of the panel in management of hereditary RCC, the consensus was reached only on 66% of genetic testing. While many issues will need to be discussed further, those statements with consensus may be used to guide physicians and patients on who, what, when and how genetic RCC risk assessment should be performed.

Abstract P4-12-33: Frequency of radiation-induced malignancies post-adjuvant radiotherapy for breast cancer in patients with Li-Fraumeni syndrome

Background. Women with Li-Fraumeni syndrome (LFS), a cancer predisposition syndrome caused by germline mutations in TP53, have an over 50% risk of developing breast cancer (BC) by age 70. Providers often avoid adjuvant radiotherapy to treat BC in LFS patients due to a reported high risk of radiation-induced malignancies of over 30%. We aimed to investigate the characteristics of LFS-associated BC and the risk of subsequent malignancy in BC patients with LFS following adjuvant radiotherapy.

Methods. A single institution retrospective chart review was conducted for female BC patients with a confirmed germline TP53 mutation. Statistical analyses were performed to compare the frequency of radiation-induced malignancies in LFS patients to non-LFS BC cases reported in the Penn Medicine Cancer Registry (PMCR) (n=6607 patients total, 3863 who received radiation).

Results. Among 95 patients with LFS, we identified 51 female BC patients with 74 primary BC diagnoses. Of 51 patients, 57% had a history of BC only, and 25% had BC as their presenting diagnosis of LFS. LFS-associated BCs were predominantly invasive ductal carcinoma (48%) and HER2+ (58%). We analyzed 20 LFS BC patients who underwent adjuvant radiotherapy with an average follow up of 11.1 (2-20) years. Of 18 patients who received radiation in a curative setting, one (6%) patient developed thyroid cancer and one (6%) patient developed sarcoma in the radiation field. The incidence of thyroid cancer did not significantly differ between LFS-associated and non-LFS BCs. The incidence of radiation-induced sarcoma in patients with LFS is significantly higher than in non-LFS BC patients (0.03%, p=0.01).

Conclusion. We found a 6% (one in 18 patients) risk of radiation-induced sarcoma in LFS BC patients, lower than the previously reported rate of 33%. Adjuvant radiotherapy should be considered in LFS BC patients when the potential risk for locoregional recurrence (LRR) or the mortality benefit to radiation is greater than 6%.

Citation Format: Anh N Le, Jacquelyn Powers, Kristin Zelley, Angela Bradbury, Payal Shah, Gary Freedman, Katherine Nathanson, Susan M Domchek, Suzanne P MacFarland, Kara N Maxwell. Frequency of radiation-induced malignancies post-adjuvant radiotherapy for breast cancer in patients with Li-Fraumeni syndrome [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-12-33.

The CHD8 overgrowth syndrome: A detailed evaluation of an emerging overgrowth phenotype in 27 patients

CHD8 has been reported as an autism susceptibility/intellectual disability gene but emerging evidence suggests that it additionally causes an overgrowth phenotype. This study reports 27 unrelated patients with pathogenic or likely pathogenic CHD8 variants (25 null variants, two missense variants) and a male:female ratio of 21:6 (3.5:1, p < .01). All patients presented with intellectual disability, with 85% in the mild or moderate range, and 85% had a height and/or head circumference ≥2 standard deviations above the mean, meeting our clinical criteria for overgrowth. Behavioral problems were reported in the majority of patients (78%), with over half (56%) either formally diagnosed with an autistic spectrum disorder or described as having autistic traits. Additional clinical features included neonatal hypotonia (33%), and less frequently seizures, pes planus, scoliosis, fifth finger clinodactyly, umbilical hernia, and glabellar hemangioma (≤15% each). These results suggest that, in addition to its established link with autism and intellectual disability, CHD8 causes an overgrowth phenotype, and should be considered in the differential diagnosis of patients presenting with increased height and/or head circumference in association with intellectual disability.

Abstract 1682: Non-V600 BRAF mutants in melanoma: Multiple MAPK mutations and distinctive RNA expression

Large discovery sequencing analyses conducted by our group and others enabled classification of melanomas into major and minor subtypes, helping to elucidate the role and diversity of activating mutations within the MAPK pathway. We sequenced 482 melanoma PDX, cell lines and patient biopsies, of which 20 (4.1%) carry non-V600 BRAF mutations. Of the 20 mutations, 14 are pathogenic, 5 are likely pathogenic and 1 is a variant of unknown significance. Interestingly, 78.5% of tumors with pathogenic non-V600 mutants and all likely pathogenic or VUS non-V600 mutants carry additional mutations within the MAPK pathway. To explore this pattern, we queried publicly available melanoma sequencing data from six previously published sequencing studies of melanoma. Consistent with our findings, nonV600-BRAF mutations were identified in 0 - 9% of melanoma sequencing studies. Of the tumors carrying non-V600 BRAF mutants, 26 of 42 (62%) carry additional mutations in the MAPK pathway. Given the co-occurrence of MAPK mutations with non-V600 mutants, we considered whether these mutations are found together within the same cell or if mutants are encoded in distinct cell populations and reflect admixture of a heterogenous tumor. We compared the variant allele frequency (VAF) of co-occurring MAPK mutants with their non-V600 BRAF counterparts in 41 available samples. The VAF between mutants was discordant (&gt;0.10 change in VAF between mutants) in 27 of 41 (68%) of the samples. To more precisely assess variants at single-cell resolution, we established a PCR based method for variant calling using single-cell-derived cDNA libraries. Pilot studies supported distinct expression patterns and we are working to generate robust and reproducible sequencing data. We also compared RNA expression data between BRAFV600 melanomas and non-V600 melanomas. This analysis revealed distinct transcriptomes that were easily distinguished based on previously established quaternary structure and kinase activity of various BRAF mutants. Interestingly, MAPK-pathway genes did not account for most of the differential expression, and an AXL-high/MITF-low expression program was highly enriched in non-V600 BRAF tumors relative to their V600 BRAF counterpart (FDR &lt;0.01). Taken together, non-V600 BRAF mutant melanomas represent a subtype characterized by a tendency for multiple MAPK mutations and an AXL-high/MITF-low enriched RNA expression pattern differentiated based on BRAF structure and function. Further studies of this rare sub-type of melanoma are important to demonstrate the diversity and interplay of MAPK dysregulation in cancer and may reveal mechanisms of tumorigenesis.

Citation Format: Elizabeth Kiernan, Paul Bastian, Liza Dorfman, Ioannis N. Anastopoulos, Brad Wubbenhorst, Clemens Krepler, Vito Rebecca, Meenhard Herlyn, Katherine Nathanson. Non-V600 BRAF mutants in melanoma: Multiple MAPK mutations and distinctive RNA expression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1682.

Abstract CT234: A Phase II, single arm study of maintenance rucaparib in patients with platinum-sensitive advanced pancreatic cancer and a pathogenic germline or somatic mutation in BRCA1, BRCA2 or PALB2

Background: PARP inhibitors have activity in multiple BRCA-related malignancies and have recently demonstrated dramatic efficacy as a maintenance strategy for platinum-sensitive ovarian cancer. Between 5-8% of patients with pancreatic cancer (PC) have a pathogenic mutation in BRCA1, BRCA2 or PALB2. Therefore, we initiated a single arm phase II clinical trial of maintenance monotherapy rucaparib in patients with advanced PC and a pathogenic germline or somatic BRCA or PALB2 mutation, whose cancer had not progressed following at least four months of platinum-based chemotherapy (NCT 03140670).

Methods: Patients were enrolled and treated with rucaparib 600mg PO BID until disease progression or unacceptable toxicity. The primary endpoint is progression free survival (PFS). Patients have previously received &gt;4 months of platinum-based chemotherapy without evidence of disease progression. However, patients with a medical contraindication to receiving the full four months of platinum have been permitted to enroll at the discretion of the primary investigator. Responses were determined using RECIST v1.1.

Results: As of December 31st, 2018, we have enrolled 24 of the planned 42 patients, of which 19 are evaluable for PFS at the time of this interim analysis. For these patients, the mutational distribution includes: 13 germline BRCA2, 3 germline BRCA1, 2 germline PALB2, 1 somatic BRCA2. Patients were predominantly female (84.2%) with a median age of 61 years (range: 35-81). Patients had received a median of four months (range 0.5-32 months) of prior platinum therapy for advanced disease. All patients were evaluable for toxicity. Overall, treatment with rucaparib was well tolerated without dose limiting toxicities. The most common adverse events that were at least possibly related to treatment included nausea (grade 1, 41.6%; grade 2, 4.2%), dysgeusia (grade 1, 33.3%) and fatigue (grade 1, 25%). One patient required dose reduction for nausea. The median PFS was 9.1 months from the start of rucaparib therapy with an ORR of 36.8% (six PRs; one CR). Disease control rate (CR + PR + SD) was 89.5% for at least eight weeks. Two patients (10.5%) had progressive disease at first follow-up scan two months after beginning treatment. Eight patients have been on rucaparib for &gt;6 months and two patients remain on treatment for &gt;1 year (13 months and 15 months). The seven responding patients include those with germline BRCA2 mutations (4 patients), germline PALB2 mutations (2 patients) and somatic BRCA2 mutation (1 patient).

Conclusions: Based on these early data, maintenance rucaparib following induction with platinum-based chemotherapy shows encouraging disease control with minimal toxicity in patients with platinum-sensitive advanced PC and a pathogenic mutation in BRCA1, BRCA2 or PALB2.

Citation Format: Kim A. Reiss Binder, Rosemarie Mick, Mark O'Hara, Ursina Teitelbaum, Thomas Karasic, Charles Schneider, Peter J. O'Dwyer, Erica Carpenter, Austin Pantel, Mehran Makvandi, David Mankoff, Katherine Nathanson, Kara Maxwell, Stacy Cowden, Mary Jane Fuhrer, Janae Romeo, Gregory L. Beatty, Susan Domchek. A Phase II, single arm study of maintenance rucaparib in patients with platinum-sensitive advanced pancreatic cancer and a pathogenic germline or somatic mutation in BRCA1, BRCA2 or PALB2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT234.

Early results from the BRCA Founder Outreach (BFOR) Study: Population genetic screening using a medical model

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Background: Barriers to population screening for BRCA mutations include access, availability of counseling, and readiness of care providers to participate in this process. The BRCA Founder OutReach (BFOR) study evaluates a digital approach to genetic testing of a defined population using a medical model and risk-adapted follow-up. Methods: The BFOR study (Bforstudy.com) includes web-based enrollment open to individuals in four US cities who are age 25 or older and have at least one grandparent of Ashkenazi Jewish (AJ) ancestry. Participants receive web-based education, provide consent, complete questionnaires, and note their preference for receiving results either from their primary care provider (PCP) or BFOR staff. BRCA AJ founder mutation results are disclosed by (e)mail or phone, depending on need for additional counseling/genetic testing. Participants will be surveyed by email for up to 5 years; a subset of PCPs is also being surveyed. Results: From March 2018 to January 2019, 2562 participants enrolled: 78% female; < 30 years old, 8%; 30-50 years, 39%; > 50 years, 53%. At enrollment, 33% requested disclosure of results by PCP. Among 847 PCPs invited to disclose results, 45% accepted, 50% declined and 5% have yet to respond. 69 (3.2%) participants tested positive for a BRCA founder mutation, of whom 8 (12%) had no significant family history. 2087 participants tested negative, of whom 6% reported a known family mutation, 38% reported a family history of breast/ovarian cancer, and 56% no such history. The most common reason for study participation was referral by a friend. One individual with a distant history of breast cancer tested positive for a BRCA2 mutation and underwent risk reducing surgery that identified an early stage fallopian tube carcinoma. Her daughter then tested positive and underwent prophylactic surgeries. Conclusions: Population screening of individuals at higher risk for cancer-predisposing mutations is feasible and identifies individuals who would not have been tested using clinical criteria. Preliminary findings reveal challenges for engaging PCPs and at-risk individuals, particularly men. Ongoing follow-up and a second phase of the study will address these barriers to testing. Clinical trial information: NCT03351803.

Genetic predisposition to breast cancer among African American women

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Background: The identification of pathogenic mutations in breast cancer susceptibility genes through clinical genetic testing leads to focused screening and prevention strategies for women at increased risk of cancer. However, the frequency of mutations and the risks of cancer associated with breast cancer predisposition genes has not been established for the African American population. Methods: Germline DNA samples from African American women (5,054 breast cancer cases and 4,993 age-matched unaffected controls) from 10 U.S. studies were tested for mutations in 20 established breast cancer predisposition genes using a QIAseq multiplex amplicon panel as part of the “CAnceR RIsk Estimates Related to Susceptibility” (CARRIERS) study. The frequency of mutations in each gene and associations between mutations and breast cancer risk, adjusted for study design, age, and first-degree family history of breast cancer, were evaluated. Results: The mean age at diagnosis of breast cancer cases was 54.4 years and the mean age of controls was 55.2 years. 18.2% of cases and 10.8% of controls reported a first-degree family history of breast cancer. Pathogenic mutations in any of the 20 breast cancer predisposition genes were identified in 7.6% of breast cancer cases and 2.4% of controls. In multivariable analyses, mutations in BRCA1, BRCA2, and PALB2 were associated with high risks of breast cancer (odds ratio (OR) > 5.0). Mutations in CHEK2 were associated with moderate risks of breast cancer (OR > 2.0), whereas mutations in ATM had lower clinical relevance (OR = 1.8). Mutations in BRCA1, BRCA2, PALB2, and RAD51D, but not CHEK2 or ATM, were associated with increased risks of estrogen receptor negative breast cancer. Conclusions: Cancer predisposition genes confer similar risks of breast cancer in the African American population as in non-Hispanic Whites. These studies provide important insights into the risks of breast cancer associated with predisposition gene mutations in the African American population.

EMR documentation of genetics evaluations in patients with ovarian cancer

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Background: Genetic testing for hereditary cancer predisposition has become increasingly complex yet impactful. Provider knowledge of test results influences risk management, implications for family members, and therapeutics. Currently, it’s unknown if genetic test (GT) results are appropriately recorded and accessible within the electronic medical record (EMR). Methods: We conducted a single-institution retrospective chart review to examine clinical diagnoses, family history of cancer, genetics referrals, and genetics services received at University of Pennsylvania’s Cancer Risk Evaluation Program (CREP) or elsewhere. The study cohort included new and prevalent cases of ovarian cancer (OC) seen by either a gynecologic or medical oncologist at the University of Pennsylvania in 2016. Analyses were conducted using SAS 9.4. Results: 667 women (83% white, 9% black, 4% Asian; mean age 61) with OC were included. 58% had a documented family history of breast, ovarian, prostate or pancreas cancer. 48% had documentation of referral to genetic testing and an additional 26% had documentation of testing outside of CREP. 26% had no documentation of referral or testing. Of those referred to CREP, 75% had genetic testing: in total 62% of the cohort had documented testing. 94% of those tested had a result documented in a provider note, and 64% had a scanned testing report uploaded into the EMR, including 74.3% of those tested through CREP and 25.7% of those tested outside. Among the 118 pathogenic mutations, 70% were documented on the EMR “problem list.” Conclusions: In this study, most, though not all, OC patients had documentation of a GT referral or testing in the EMR. Although GT results were routinely included in progress notes, these reports were less commonly scanned into the EMR (particularly for those tested outside Penn) or included in the EMR “problem list” which is both searchable and immediately visible. Capturing genetic data in a uniform and easily accessible manner within the EMR is necessary to maximize clinical utility of this information and should be a focus for EMR module development.

Subphenotype meta-analysis of testicular cancer genome-wide association study data suggests a role for RBFOX family genes in cryptorchidism susceptibility

STUDY QUESTION

Can subphenotype analysis of genome-wide association study (GWAS) data from subjects with testicular germ cell tumor (TGCT) provide insight into cryptorchidism (undescended testis, UDT) susceptibility?

SUMMARY ANSWER

Suggestive intragenic GWAS signals common to UDT, TGCT case-case and TGCT case-control analyses occur in genes encoding RBFOX RNA-binding proteins (RBPs) and their neurodevelopmental targets.

WHAT IS KNOWN ALREADY

UDT is a strong risk factor for TGCT, but while genetic risk factors for TGCT are well-known, genetic susceptibility to UDT is poorly understood and appears to be more complex.

STUDY DESIGN, SIZE, DURATION

We performed a secondary subphenotype analysis of existing GWAS data from the Testicular Cancer Consortium (TECAC) and compared these results with our previously published UDT GWAS data, and with data previously acquired from studies of the fetal rat gubernaculum.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Studies from the National Cancer Institute (NCI), United Kingdom (UK) and University of Pennsylvania (Penn) that enrolled white subjects were the source of the TGCT GWAS data. We completed UDT subphenotype case-case (TGCT/UDT vs TGCT/non-UDT) and case-control (TGCT/UDT vs control), collectively referred to as 'TECAC' analyses, followed by a meta-analysis comprising 129 TGCT/UDT cases, 1771 TGCT/non-UDT cases, and 3967 unaffected controls. We reanalyzed our UDT GWAS results comprising 844 cases and 2718 controls by mapping suggestive UDT and TECAC signals (defined as P < 0.001) to genes using Ingenuity Pathway Analysis (IPA®). We compared associated pathways and enriched gene categories common to all analyses after Benjamini-Hochberg multiple testing correction, and analyzed transcript levels and protein expression using qRT-PCR and rat fetal gubernaculum confocal imaging, respectively.

MAIN RESULTS AND THE ROLE OF CHANCE

We found suggestive signals within 19 genes common to all three analyses, including RBFOX1 and RBFOX3, neurodevelopmental paralogs that encode RBPs targeting (U)GCATG-containing transcripts. Ten of the 19 genes participate in neurodevelopment and/or contribute to risk of neurodevelopmental disorders. Experimentally predicted RBFOX gene targets were strongly overrepresented among suggestive intragenic signals for the UDT (117 of 628 (19%), P = 3.5 × 10-24), TECAC case-case (129 of 711 (18%), P = 2.5 × 10-27) and TECAC case-control (117 of 679 (17%), P = 2 × 10-21) analyses, and a majority of the genes common to all three analyses (12 of 19 (63%), P = 3 × 10-9) are predicted RBFOX targets. Rbfox1, Rbfox2 and their encoded proteins are expressed in the rat fetal gubernaculum. Predicted RBFOX targets are also enriched among transcripts differentially regulated in the fetal gubernaculum during normal development (P = 3 × 10-31), in response to in vitro hormonal stimulation (P = 5 × 10-45) and in the cryptorchid LE/orl rat (P = 2 × 10-42).

LARGE SCALE DATA

GWAS data included in this study are available in the database of Genotypes and Phenotypes (dbGaP accession numbers phs000986.v1.p1 and phs001349.v1p1).

LIMITATIONS, REASONS FOR CAUTION

These GWAS data did not reach genome-wide significance for any individual analysis. UDT appears to have a complex etiology that also includes environmental factors, and such complexity may require much larger sample sizes than are currently available. The current methodology may also introduce bias that favors false discovery of larger genes.

WIDER IMPLICATIONS OF THE FINDINGS

Common suggestive intragenic GWAS signals suggest that RBFOX paralogs and other neurodevelopmental genes are potential UDT risk candidates, and potential TGCT susceptibility modifiers. Enrichment of predicted RBFOX targets among differentially expressed transcripts in the fetal gubernaculum additionally suggests a role for this RBP family in regulation of testicular descent. As RBFOX proteins regulate alternative splicing of Calca to generate calcitonin gene-related peptide, a protein linked to development and function of the gubernaculum, additional studies that address the role of these proteins in UDT are warranted.

STUDY FUNDING/COMPETING INTEREST(S)

The Eunice Kennedy Shriver National Institute for Child Health and Human Development (R01HD060769); National Center for Research Resources (P20RR20173), National Institute of General Medical Sciences (P20GM103464), Nemours Biomedical Research, the Testicular Cancer Consortium (U01CA164947), the Intramural Research Program of the NCI, a support services contract HHSN26120130003C with IMS, Inc., the Abramson Cancer Center at Penn, National Cancer Institute (CA114478), the Institute of Cancer Research, UK and the Wellcome Trust Case-Control Consortium (WTCCC) 2. None of the authors reports a conflict of interest.

Reframing the Biological Basis of Neuroprotection Using Functional Genomics: Differentially Weighted, Time-Dependent Multifactor Pathogenesis of Human Ischemic Brain Damage

Background: Neuroprotection studies are generally unable to demonstrate efficacy in humans. Our specific hypothesis is that multiple pathophysiologic pathways, of variable importance, contribute to ischemic brain damage. As a corollary to this, we discuss the broad hypothesis that a multifaceted approach will improve the probability of efficacious neuroprotection. But to properly test this hypothesis the nature and importance of the multiple contributing pathways needs elucidation. Our aim is to demonstrate, using functional genomics, in human cardiac surgery procedures associated with cerebral ischemia, that the pathogenesis of perioperative human ischemic brain damage involves the function of multiple variably weighted proteins involving several pathways. We then use these data and literature to develop a proposal for rational design of human neuroprotection protocols.

Methods: Ninety-four patients undergoing deep hypothermic circulatory arrest (DHCA) and/or aortic valve replacement surgery had brain damage biomarkers, S100β and neurofilament H (NFH), assessed at baseline, 1 and 24 h post-cardiopulmonary bypass (CPB) with analysis for association with 92 single nucleotide polymorphisms (SNPs) (selected by co-author WAK) related to important proteins involved in pathogenesis of cerebral ischemia.

Results: At the nominal significance level of 0.05, changes in S100β and in NFH at 1 and 24 h post-CPB were associated with multiple SNPs involving several prospectively determined pathophysiologic pathways, but were not individually significant after multiple comparison adjustments. Variable weights for the several evaluated SNPs are apparent on regression analysis and, notably, are dissimilar related to the two biomarkers and over time post CPB. Based on our step-wise regression model, at 1 h post-CPB, SOD2, SUMO4, and GP6 are related to relative change of NFH while TNF, CAPN10, NPPB, and SERPINE1 are related to the relative change of S100B. At 24 h post-CPB, ADRA2A, SELE, and BAX are related to the relative change of NFH while SLC4A7, HSPA1B, and FGA are related to S100B.

Conclusions: In support of the proposed hypothesis, association SNP data suggest function of specific disparate proteins, as reflected by genetic variation, may be more important than others with variation at different post-insult times after human brain ischemia. Such information may support rational design of post-insult time-sensitive multifaceted neuroprotective therapies.

Induction of Telomere Dysfunction Prolongs Disease Control of Therapy-Resistant Melanoma

Purpose: Telomerase promoter mutations are highly prevalent in human tumors including melanoma. A subset of patients with metastatic melanoma often fail multiple therapies, and there is an unmet and urgent need to prolong disease control for those patients.Experimental Design: Numerous preclinical therapy-resistant models of human and mouse melanoma were used to test the efficacy of a telomerase-directed nucleoside, 6-thio-2'-deoxyguanosine (6-thio-dG). Integrated transcriptomics and proteomics approaches were used to identify genes and proteins that were significantly downregulated by 6-thio-dG.Results: We demonstrated the superior efficacy of 6-thio-dG both in vitro and in vivo that results in telomere dysfunction, leading to apoptosis and cell death in various preclinical models of therapy-resistant melanoma cells. 6-thio-dG concomitantly induces telomere dysfunction and inhibits the expression level of AXL.Conclusions: In summary, this study shows that indirectly targeting aberrant telomerase in melanoma cells with 6-thio-dG is a viable therapeutic approach in prolonging disease control and overcoming therapy resistance. Clin Cancer Res; 24(19); 4771-84. ©2018 AACR See related commentary by Teh and Aplin, p. 4629.

Abstract 4835: Targeting the ATR/CHK1 axis in combination with PARP inhibition is more effective than PARP inhibition alone in BRCA mutant models

Introduction:

Approximately 50% of high grade serous ovarian cancers (HGSOC) have defects in genes involved in homologous recombination repair (HR). BRCA1/2 mutant HGSOCs have a deficiency in the repair of double strand DNA breaks by HR. Poly(ADP-ribose) polymerase inhibitors (PARPi) block the repair of single-stranded breaks leading to double strand DNA breaks which cannot be repaired efficiently in BRCA-deficient cancers capitalizing on synthetic lethality. PARPi have a modest clinical response of only ∼40% in recurrent BRCA mutant HGSOCs. We hypothesize that PARPi alone increases reliance on other DNA repair pathways such as ATR/CHK1 in HR deficient cells, and by targeting ATR/CHK1 in combination with PARPi would be more effective in eradicating tumor growth.

Experimental Procedures:

Effects of PARP inhibitor (PARPi, Olaparib), CHK1 inhibitor (CHK1i, MK8776), and ATR inhibitor (ATRi, AZD6738) on cell cycle, survival, colony formation, genome stability were evaluated in PEO1 (BRCA2 mutant), PEO4 (BRCA wild-type), JHOS4 (BRCA1 mutant), and WO-24 (BRCA wild-type) ovarian cancer cells. A BRCA2 mutant (8945delAA) orthotopic PDX model was used to evaluate PARPi alone or in combination with CHK1/ATRi. Targeted capture massively parallel sequencing, Reverse-Phase Protein Array Analysis (RPPA) and IHC were performed on cells and xenografts to evaluate for biomarkers of response.

Results:

Monotherapy with PARPi, CHK1i, and ATRi in vitro demonstrated selectivity in mediating cell death and DNA damage in BRCA1/2 mutant cell lines (PEO1, JHOS4) compared to BRCA1/2 wild-type, platinum resistant cell lines (PEO4, WO-24). However, monotherapy only results in ∼40-50% cell death in BRCA1/2 mutant cell lines. PARPi alone resulted in tumor suppression but not tumor eradication in a BRCA2 mutant PDX model. PARPi treatment resulted in an increase in ATR/CHK1 signaling in BRCA1/2 mutant cells. Treatment with ATR/CHK1i in combination with PARPi is synergistic in reducing survival of BRCA1/2 cells. Combination treatment was more effective in targeting cell cycle mediators, and promoting apoptosis. Treatment with either PARPi+ATRi or PARPi+CHK1i combinations was synergistic in causing tumor suppression but PARPi/ATRi combination caused tumor regression in a BRCA2 mutant PDX model.

Conclusions:

Strategies to optimize approaches capitalizing on synthetic lethality are needed for HR deficient HGSOC. PARPi is effective in BRCA deficient cancers but can potentially be more effective when combined with ATR/CHK1i.

Citation Format: Erin George, Hyoung Kim, Janos Tanyi, Ryan Ragland, Rugang Zhang, Patricia Bradford, Clemens Krepler, Katherine Nathanson, Brandon Wenz, Yiling Lu, Gordon Mills, Mark Morgan, Fiona Simpkins. Targeting the ATR/CHK1 axis in combination with PARP inhibition is more effective than PARP inhibition alone in BRCA mutant models. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4835.

Abstract 796: ERCC3 R109X is a moderate risk breast cancer risk variant in Ashkenazi Jews

Background:

Known gene mutations account for approximately 50% of the risk for breast cancer. However, a considerable fraction of heritable risk remains unexplained. Fifteen percent of the risk is accounted for by BRCA1/2 and another 3% by TP53, PTEN, LKB1 and CDH1. CHEK2, ATM, PALB2, BRIP1, RAD51C, RAD51D and BARD1 account for 4%, while SNPs discovered from large multicenter genome-wide association studies explain another 14% of the heritable risk. Founder mutations in the DNA repair pathway genes such as BRCA1 and BRCA2 account for the majority of AJ breast cancer mutations.

Methods:

We performed exome sequencing of 49 early onset (age &lt;35) breast cancer cases, and 85 BRCA wild type familial breast cancer cases, all of Ashkenazi Jewish (AJ) from the New York City area. A recurrent truncating mutation was then analyzed in 3131 breast cancer cases and 2716 unaffected women of Ashkenazi ancestry from New York and Israel. Using CRISPR and overexpression systems on the human mammary epithelial cell line HMLE, transcript and protein levels were assayed for the mutant and compared to wild-type. Treatment with IlludinS and UVC were performed to assess DNA damage response. Finally, clonogenic survival assay was also performed.

Results: Amongst the DNA repair pathway genes, exome sequencing revealed a heterozygous recurrent truncating mutation in ERCC3 (R109X) in 2 of 49 early onset breast cancer cases of AJ ancestry and 4 familial AJ probands. Taqman genotyping in a case control setting from New York and Israel revealed 54 mutation carriers in 3131 cases and 32 in the 2716 controls. In total, there were 60 heterozygotes detected in 3209 cases and 32 in 2716 controls [OR 1.59 (95% CI 1.01-2.50)]; p = 0.02 Fisher one- tailed). Functional studies using CRISPR and overexpression systems on human mammary epithelial cells, show that the mutation results in lower transcript levels and this reduction is effected by nonsense mediated decay of the mutant transcript. Western blotting showed that the mutation resulted in a smaller protein (∼12kDa). Clonogenic assays showed similar survival rate of mutant and wildtype under UVC exposure, however the mutant cell line showed significantly smaller colony size demonstrating a growth disadvantage that was further increased upon DNA damage. Treatment with fungal sesquiterpene IlludinS, a known sensitizer to mutant ERCC3 cell lines, showed drastically reduced survival when compared to the wild type human mammary epithelial cells.

Conclusions:

We demonstrate that ERCC3 is a moderate risk gene for breast cancer in individuals of Ashkenazi ancestry. ERCC3 is somatically mutated in multiple cancers including breast, ovarian and pancreatic cancers, however its role as a cancer susceptibility gene requires further elucidation. Additional functional and population genetic studies to further characterize this novel ERCC3 variant are underway.

Citation Format: Joseph Vijai, Sabine Topka, Kara Maxwell, Vignesh Ravichandran, Tinu Thomas, Danylo Villano, Ann Maria, Pragna Gaddam, Anne Lincoln, Steven Hart, Susan Neuhausen, Mark Robson, Jeffrey Weitzel, Mark Daly, Katherine Nathanson, Fergus Couch, Gadi Rennert, Kenneth Offit. ERCC3 R109X is a moderate risk breast cancer risk variant in Ashkenazi Jews. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 796.

Abstract P6-07-05: Mutational spectrum and tumor response in metastatic breast cancer

Background: While several comprehensive genomic sequencing tests are clinically available for breast cancer(BC), little is known about the spectrum of findings reported in the general population and clinical utility of findings for patients(pts). Here we report tumor sequencing from the METAMORPH study, a comprehensive genomic testing approach in pts with metastatic(met) BC.

Methods: Pts with either known or suspected BC mets consented to and clinically underwent concurrent diagnostic and research tumor biopsies(bx). FFPE specimens were profiled via Illumina TruSeq Cancer Panel next generation sequencing platform covering 212 amplicons in 47 cancer genes. Pathology, treatment and outcome data were prospectively collected and tracked. Aside from Her2-directed treatment, therapy was not mutation (mut)-matched.

Results: 64 pts enrolled between 11/2013 – 05/2015. Of these, 48 had bx successfully sequenced (75%). Of those without sequencing, 5 had negative/insufficient tissue, 2 had insufficient DNA, remainder no bx/pending. Median age of those sequenced was 56 (range 31-78); 81% Caucasian, 17% African American. 25% (12 pts) presented with de novo stage IV disease. Of those with recurrence (n=36), 83% had prior adjuvant chemotherapy; 81% hormone receptor positive(HR+) had prior endocrine therapy. Median # prior lines of therapy for met disease was 2 (IQR 0 – 8). Tumor characteristics, including mut analyses, are shown in Table 1. # muts did not differ significantly by subtype(p=0.22). Frequency of TP53 and PIK3CA hotspot muts was nearly identical to TCGA. Median # muts was 1 for pts with both de novo mets and recurrence(p=0.79). # of muts was not associated with time to recurrence(p=0.80). Excluding pts found to have TP53 mut only or ERBB2 alterations in known Her2+ disease, 42% of pts were identified as having at least one potentially actionable alteration (PIK3CA mut, AKT1 mut or EGFR amplification). Median time to treatment failure(TTF) on subsequent therapy was 4.1 months for overall group, and 4.1, 6.2, and 1.6 months for HR+/Her2-, any Her2+ and TN, respectively, adjusted for line of therapy(p=0.03). After adjustment for # lines of prior met therapy, TTF was 4.7 vs. 4.1 months for pts with any mut vs. none(p=0.89); 5.7 vs 4.1 months for PIK3CA+ vs. not (p=0.94); 3.3 vs. 6.5 months for TP53+ vs. not (p=0.03).

Conclusion: Pts with met BC have frequent and potentially actionable muts.While overall # of muts did not affect response, tumors with TP53 muts had shorter response to subsequent therapy in this cohort. Additional data are needed to determine the clinical utility of mut testing in met BC, for both standard and mut-matched therapy.

 Total (n=48)HR+/Her2- (n=28)Any HER2+ (n=7)TN (n=13)Receptor concordant with primary 100%78%77%# Mutations Median (Range)1 (0-4)1 (0-3)1 (1-2)1 (0-4)014 (29%)10 (36 %)04 (31%)118 (38%)11 (39%)4 (57%)3 (23%)213 (27%)5 (18%)3 (43%)5 (38%)3+3 (6%)2 (7%)01 (8%)Prevalent Mutations (&gt;20%)TP53 (38%), PIK3CA (35%)PIK3CA (50%), TP53 (25%)TP53 (60%), ERBB2amp (86%)TP53 (62%),PIK3CA (23%)Other Alterations (#)ATM (1), KIT (1), PDGFRA (1), PTEN(1), RB1 (1), SMAD4 (1), SMO (1), STK11 (1)AKT1 (1), ATM VUS (1), ERBB2 (1), PTEN (1), SMAD4 VUS (1), SMO VUS (1)ERBB2 (1), STK11(1)EGFR amp (2), KIT amp (1),PDGFRA amp (1), RB1 VUS (1)

Citation Format: Soucier-Ernst D, Colameco C, Troxel AB, Clark C, Shih N, Maxwell KN, Morrissette J, Lieberman D, Feldman M, Goodman N, Bradbury A, Clark A, Domchek S, Fox K, Glick J, Matro J, Nathanson K, Chodosh L, DeMichele A. Mutational spectrum and tumor response in metastatic breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-07-05.

Collaborative science in the next-generation sequencing era: a viewpoint on how to combine exome sequencing data across sites to identify novel disease susceptibility genes

The purpose of this article is to inform readers about technical challenges that we encountered when assembling exome sequencing data from the 'Simplifying Complex Exomes' (SIMPLEXO) consortium-whose mandate is the discovery of novel genes predisposing to breast and ovarian cancers. Our motivation is to share these obstacles-and our solutions to them-as a means of communicating important technical details that should be discussed early in projects involving massively parallel sequencing.

Abstract 4668: Targeted, massively parallel sequencing identifies novel genetic subsets of cutaneous melanoma

Despite the prevalence of recurrent, high activating BRAF V600 mutations in 45% of tumors, cutaneous melanoma (CM) is a heterogeneous malignancy resulting from aberrant signaling in multiple pathways. It has been traditionally characterized by activation of the MAPK and PI3K signaling pathways, as well as cell cycle disruption. In recent years, whole-genome and exome sequencing studies have identified several new genes associated with melanomagenesis. However, a comprehensive understanding of concurrent, and mutually exclusive, mutations in tumors is currently lacking. Using a custom targeted capture of 108 genes previously implicated in melanoma pathogenesis, massively parallel sequencing was performed on 94 human melanoma cell lines, 67 patient-derived xenografts (PDX), and 5 cell lines made from PDX, all untreated. Samples were then clustered into groups based on deleterious mutations. 83% of samples had deleterious mutations in the MAPK signaling pathway, including 92 high activity BRAF (55%), 35 RAS codon 61 (21%), 7 with multiple mutations (e.g. low activity BRAF/RAS codons 12/13) (4%) and 10 NF1 (6%) mutated samples. Likely deleterious NF1 mutations were found in several BRAF or NRAS-mutated samples. PI3K pathway mutations were found in 10% of samples, predominantly associated with BRAF mutations. TP53 mutations were found in 24% of samples and were associated with all MAPK signaling mutations. Mutations in chromatin remodeling genes (ARID1A/1B, ARID2, TRRAP, and BAP1) were mutually exclusive with each other and primarily found in tumors with high activity BRAF or NRAS mutations. The majority of BRAF or RAS-mutated samples with a mutation in a chromatin remodeling gene lacked mutations in cell cycle, TP53, and PI3K signaling genes; however, 100% of deleterious, or likely deleterious, NF1-mutated samples with a chromatin remodeling gene mutation harbored additional mutations in cell cycle, TP53, and/or PI3K signaling genes. Of particular interest, five of the 10 NF1-mutated samples (50%) lacked BRAF, RAS, and MEK1/2 mutations but harbored likely deleterious mutations in MAP3K5 or MAP3K9, suggesting the potential involvement of the JNK signal transduction pathway in this particular cohort. Only 4% of samples did not have a deleterious mutation in any of the genes on the panel. These data reveal novel insights into the genetics of melanomas lacking a canonical BRAF V600 mutation. Functional assays are needed to confirm the biological relevance of likely deleterious mutations, which will further facilitate a more thorough classification of CM subsets.

Citation Format: Bradley Garman, Clemens Krepler, Katrin Sproesser, Patrica Brafford, Melissa Wilson, Bradley Wubbenhorst, Ravi Amaravadi, Joseph Bennett, Marilda Beqiri, Michael Davies, David Elder, Keith Flaherty, Dennie Frederick, Tara C. Gangadhar, Michael Guarino, David Hoon, Giorgos Karakousis, Nandita Mitra, Nicholas J. Petrelli, Lynn Schuchter, Batool Shannan, Jennifer Wargo, Min Xiao, Wei Xu, Xaiowei Xu, Meenhard Herlyn, Katherine Nathanson. Targeted, massively parallel sequencing identifies novel genetic subsets of cutaneous melanoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4668. doi:10.1158/1538-7445.AM2015-4668

Abstract 1182: Patient derived xenograft (PDX) of human melanoma to predict clinical responses

The approval of three drugs targeting the MAPK pathway has led to new standard therapies for melanoma with BRAFV600E mutations. The excitement about these therapeutic successes is somewhat dampened by the relapse of most if not all treated patients due to the development of acquired (secondary) resistance. Early clinical trial results indicate that combining BRAF and MEK inhibitors can improve survival and delay the onset of resistance. Currently, there is a lack of good translational models to study resistance pathways found in patients. We have developed a patient-derived xenograft (PDX) bank for assessing patients' responses to therapies.

Human melanoma tissues were obtained following surgery, and small pieces were implanted subcutaneously with Matrigel® into NSG mice. This technique was advantageous over injecting single tumor cells. It also allows prior dissociation and freezing for extended time periods prior to injection. The xenografts maintained a histological architecture similar to the respective patients' lesions. NSG mice injected with tumor fragments and single cells allow a high rate of tumor growth of approximately 90%, even if few malignant cells from fine needle aspirates are injected. When injecting decreasing numbers of tumor cells after removal of endothelial cells, hematopoietic cells and red blood cells (but not fibroblasts), in 5 out of 7 cases single malignant cells induced tumors. Our current tumor bank contains 125 samples linked to patients' clinical data and characterized for mutational status and spontaneous metastasis rates (25%). DNA fingerprinting was matched to normal blood DNA if available to assure identity of the samples. The samples had a similar distribution pattern of genetic abnormalities to those in patients, thus allowing their use for mutation-specific therapy strategies. As an example, a PDX from a patient with intrinsic resistance to vemurafenib was grown to compare tumor growth on a 200 ppm BRAF inhibitor (PLX4720) diet, 200 ppm PLX4720 + 7 ppm MEK inhibitor (PD0325901) combination diet, or control diet for 21 days. As in the original patient, the BRAF inhibitor alone did not inhibit tumor growth, while the combination of BRAF and MEK inhibition showed significant tumor growth inhibition demonstrating that a PDX can predict clinical outcome.

Citation Format: Clemens Krepler, Katrin Sproesser, Patricia Brafford, Min Xiao, Marilda Beqiri, Wei Xu, Katherine Nathanson, Jennifer Wargo, Keith Flaherty, Donald L. Morton, Dave S. Hoon, Randall Ryan, Michael Guarino, Nicholas J. Petrelli, David Elder, Xiawei Xu, Giorgos Karakousis, Lynn Schuchter, Meenhard Herlyn. Patient derived xenograft (PDX) of human melanoma to predict clinical responses. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1182. doi:10.1158/1538-7445.AM2014-1182

Abstract 3282: Determination of cancer susceptibility in probands with breast and ovarian cancer

Germline mutations of BRCA1 and BRCA2 underlie joint susceptibility to breast and ovarian cancers, but do not account for all cases. Genome wide association studies show little overlap between common variants associated with breast and ovarian cancer susceptibility, whereas rare variants in genes initially identified as breast cancer susceptibility genes also confer susceptibility to ovarian cancer cases, unselected for breast cancer. Ovarian and breast tumors also are observed in Peutz-Jeghers and possibly in Lynch syndrome. To further elucidate rare germline susceptibilities for breast and ovarian cancer, we have ascertained a unique cohort of 90 BRCA1/2-negative probands with a personal history of breast cancer and ovarian/fallopian tube/peritoneal cancer, unselected for family history. Cases are from the clinical genetics services of Memorial Sloan-Kettering Cancer Center and University of Pennsylvania. Analysis is ongoing using both targeted and exome sequencing approaches. Germline DNA of 69 cases will be subjected to whole exome sequencing. A total of 21 additional cases will undergo targeted sequencing for 28 genes (8 cases) and an extended panel of 54 genes (13 cases). The majority of ovarian cancers are high-grade serous epithelial ovarian carcinoma (n=51), in combination with invasive ductal or DCIS (n=36), invasive lobular (n=4), or unspecified (n=11) breast cancers. The remaining ovarian subgroups comprise other epithelial subtypes; endometrioid (n=9), clear cell (n=3), mucinous and low-grade serous (n=3) and non-epithelial (n=4) or unclassified (n=20), in combination with invasive ductal or DCIS (n=21), invasive lobular (n=5) or unspecified (n=13) breast cancers. Preliminary analysis of the targeted set of genes in 69 cases, reveals 43 predicted pathogenic coding or splice site variants; 17 of which are within PALB2, MSH2, MSH6, BARD1, FANCE, CDKN2A, TP53, SETD2, SIRT1, BRIP1, RAD50, and RAD51D and are not seen in dbSNP138, 1000 Genomes or Exome Variant Server ESP6500 and 26 variants with reported frequencies in MUTYH, MSH6, MLH1, FAM175A, RAD50, UIMC1, JARID2, PHF3, SIRT1, MRE11A, ATM, BRCA2, TP53BP1, CDH1, RAD51D, BRCA1, BABAM1 of less than 1% allele frequency in public databases. Analysis of these variants across and within histologic subtypes is being undertaken to look for specific genotype-phenotype correlations. Analysis of novel candidate genes and pathways by co-segregation, functional analysis, as well as external replication is underway to determine whether shared rare variants, mutated genes, or altered pathways confer cancer susceptibility in this cohort. Germline susceptibility to breast and ovarian cancer is heterogenous and remains a critical research and clinical question. Improved understanding of the susceptibility genetics will allow further examination of the utility of targeted cancer prevention strategies in those who are found to be at risk.

Citation Format: Kasmintan A. Schrader, Kara N. Maxwell, Joseph Vijai, Steven Hart, Tinu Thomas, Bradley Wubbenhorst, Lucia Guidugli, Robert Klein, Marina Corines, Liying Zhang, Susan Neuhausen, Jeffrey Weitzel, Namrata Gupta, Larry Norton, Clifford Hudis, Gad Getz, Mark Daly, Steven Lipkin, David Altshuler, Fergus Couch, Katherine Nathanson, Kenneth Offit. Determination of cancer susceptibility in probands with breast and ovarian cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3282. doi:10.1158/1538-7445.AM2014-3282

Abstract 2378: Harmonization of next generation sequencing data within consortia for gene discovery in familial breast cancer

Massively parallel next generation sequencing data (NGS) has proved to be useful in identification of rare Mendelian disorders. Efforts are on-going to use NGS for discovery of novel rare variants in common disease etiology. Distinguishing rare private mutations from causal variants remains a major challenge in complex disorders. With decreasing cost, investigators are generating NGS data for common cancers. However, power and other considerations suggest that a consortia approach of pooling data is more likely to succeed where individual efforts fail. Combining data within such consortia brings its own level of challenges. We enumerate these challenges and suggest recommendations based on our experience of combining and harmonizing NGS data on 358 breast cancer samples from four centers; (City of Hope n=8, Mayo Clinic n=221, MSKCC n=96 and University of Pennsylvania n=33). Major concerns were ability of individual datasets to discover known and novel variations, depth of coverage across the exome, and quality of variants. Using pre- and post-processed data, we demonstrate an increased power for detecting variants when using a joint-calling method, quality control (QC) and quality assurance pre- and post-merge, as well as the advantages of combined annotations and filtering procedures. To generate a filtered list of high confident calls, we subset the data on Depth per Allele (DP), Genotyping Quality (GQ), Allele balance, Phred likelihood score (PL) as well as using frequency filters on the alternate allele both within the data and comparing against convenience control summaries. We describe general principles and QC measures to be adopted when NGS data is used from diverse sources, specifically applicable to large consortia.

Note: This abstract was not presented at the meeting.

Citation Format: Joseph Vijai, Steven Hart, Tinu Thomas, Bradley Wubbenhorst, Lucia Guidugli, Kasmintan Schrader, Kara Maxwell, Lauren Jacobs, Danylo Villano, Robert Klein, Steven Lipkin, Susan Neuhausen, Jeffrey Weitzel, David Altshuler, Fergus Couch, Kenneth Offit, Katherine Nathanson. Harmonization of next generation sequencing data within consortia for gene discovery in familial breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2378. doi:10.1158/1538-7445.AM2014-2378

DNA glycosylases involved in base excision repair may be associated with cancer risk in BRCA1 and BRCA2 mutation carriers

Single Nucleotide Polymorphisms (SNPs) in genes involved in the DNA Base Excision Repair (BER) pathway could be associated with cancer risk in carriers of mutations in the high-penetrance susceptibility genes BRCA1 and BRCA2, given the relation of synthetic lethality that exists between one of the components of the BER pathway, PARP1 (poly ADP ribose polymerase), and both BRCA1 and BRCA2. In the present study, we have performed a comprehensive analysis of 18 genes involved in BER using a tagging SNP approach in a large series of BRCA1 and BRCA2 mutation carriers. 144 SNPs were analyzed in a two stage study involving 23,463 carriers from the CIMBA consortium (the Consortium of Investigators of Modifiers of BRCA1 and BRCA2). Eleven SNPs showed evidence of association with breast and/or ovarian cancer at p<0.05 in the combined analysis. Four of the five genes for which strongest evidence of association was observed were DNA glycosylases. The strongest evidence was for rs1466785 in the NEIL2 (endonuclease VIII-like 2) gene (HR: 1.09, 95% CI (1.03-1.16), p = 2.7 × 10(-3)) for association with breast cancer risk in BRCA2 mutation carriers, and rs2304277 in the OGG1 (8-guanine DNA glycosylase) gene, with ovarian cancer risk in BRCA1 mutation carriers (HR: 1.12 95%CI: 1.03-1.21, p = 4.8 × 10(-3)). DNA glycosylases involved in the first steps of the BER pathway may be associated with cancer risk in BRCA1/2 mutation carriers and should be more comprehensively studied.

COMPLEXO: identifying the missing heritability of breast cancer via next generation collaboration

Linkage analysis, positional cloning, candidate gene mutation scanning and genome-wide association study approaches have all contributed significantly to our understanding of the underlying genetic architecture of breast cancer. Taken together, these approaches have identified genetic variation that explains approximately 30% of the overall familial risk of breast cancer, implying that more, and likely rarer, genetic susceptibility alleles remain to be discovered.

A classification model for BRCA2 DNA binding domain missense variants based on homology-directed repair activity

The relevance of many BRCA2 variants of uncertain significance (VUS) to breast cancer has not been determined due to limited genetic information from families carrying these alterations. Here, we classified six new variants as pathogenic or nonpathogenic by analysis of genetic information from families carrying 64 individual BRCA2 DNA binding domain (DBD) missense mutations using a multifactorial likelihood model of cancer causality. Next, we evaluated the use of a homology-directed DNA break repair (HDR) functional assay as a method for inferring the clinical relevance of VUS in the DBD of BRCA2 using 18 established nonpathogenic missense variants and all 13 established pathogenic missense mutations from the BRCA2 DBD. Compared with the known status of these variants based on the multifactorial likelihood model, the sensitivity of the HDR assay for pathogenic mutations was estimated at 100% [95% confidence interval (CI): 75.3%-100%] and specificity was estimated at 100% (95% CI: 81.5%-100%). A statistical classifier for predicting the probability of pathogenicity of BRCA2 DBD variants was developed using these functional results. When applied to 33 additional VUS, the classifier identified eight with 99% or more probability of nonpathogenicity and 18 with 99% or more probability of pathogenicity. Thus, in the absence of genetic evidence, a cell-based HDR assay can provide a probability of pathogenicity for all VUS in the BRCA2 DBD, suggesting that the assay can be used in combination with other information to determine the cancer relevance of BRCA2 VUS.

Abstract B12: PTEN modulates sensitivity to a novel ERK inhibitor in BRAFV600E-mutant melanomas

The presence of activating BRAF mutations in approximately 50% of melanomas, the majority of which are BRAFV600E, has prompted the development of selective inhibitors of the BRAF/MAPK/ERK pathway for targeted therapy. RAF inhibitors, including vemurafenib and GSK2118436, have shown striking results in clinical trials, highlighting this pathway as a suitable target for melanoma therapy. A number of other pharmacological agents targeting this pathway are currently in pre-clinical or clinical development. However, therapy with MAPK pathway inhibitors results in a wide range of response patterns in patients with BRAF-mutant tumors. Furthermore, even in patients with measurable responses, tumors eventually develop resistance and patients relapse. It has been previously reported that activation of the PI3K pathway may play a role modulating the response to RAF and MEK inhibitors. Here we report that melanoma cells which harbor the BRAFV600E mutation and express PTEN have low levels of phospho-AKT and are sensitive to a novel ATP-competitive ERK inhibitor. In contrast, BRAFV600E mutant melanoma cell lines that do not express PTEN have higher levels of phospho-AKT and are less sensitive to ERK inhibition. Importantly, we have confirmed these findings in an in vivo xenotransplantation model of melanoma. Additionally, we found that siRNA-mediated PTEN silencing in a PTEN wild-type cell line modestly decreases sensitivity to ERK inhibition. Conversely, PTEN overexpression in a PTEN-null cell line partially sensitizes cells to the ERK small molecule inhibitor. Consistent with these findings, targeting PI3K in melanoma cells lacking functional PTEN sensitizes them to ERK inhibition. Our studies suggest that the presence or absence of functional PTEN can modulate response to ERK inhibitors and warrant further evaluation of combination strategies to treat melanomas refractory to inhibitors of the MAPK pathway.

Abstract 5557: Mutation analysis of melanoma tumor samples from ECOG 2603 clinical trial

The BRAF kinase, a member of the MAP kinase pathway, has emerged as an attractive molecule to target in melanoma. In an initial attempt to target BRAF in melanoma, a randomized, phase III trial (ECOG 2603) of carboplatin, paclitaxel, and sorafenib versus carboplatin, paclitaxel, and placebo was performed. Patients enrolled on the trial had either unresectable, locally advanced Stage III or Stage IV melanoma. We analyzed patients’ tumor samples for 74 mutations in 13 genes using a custom iPlex (Sequenom). We have preliminarily analyzed 157 tumor samples from patients enrolled in this clinical trial. Analysis of the initial data set demonstrates that 62 samples (42%, 62/148, 95% CI 34%,50%) carried BRAF mutations - 60 samples with V600 and two samples having a BRAF V601 mutation. Thirty eight samples (26%, 38/148, 95% CI 19%,33%) were positive for NRAS mutations, with 33 with Q61, two G12 and three G13 mutations. With the exception of one tumor sample, the BRAF and NRAS mutations were negatively correlated with each other, consistent with prior observations. We also observed a number of rare mutations in our samples including one in AKT1, one in AKT3, four in CDK4, five in beta-catenin, two in GNAQ and three in KIT. The results of this study demonstrated no difference between the two treatment arms in OS and PFS and no association with treatment outcome and BRAF and NRAS mutations. Consequently, the treatment arms were collapsed, and we examined the relationship of BRAF and NRAS mutations with OS and PFS. Interestingly, our data demonstrated that the BRAF and NRAS mutations did not correlate with OS or PFS. This sample population is unique in that it provides a large data set of melanoma tumor samples, all of whom were entered on a clinical trial, unselected for pre-existing mutations. Using the Sequenom assay platform, we have identified a number of mutations in a subset of genes known to be involved in melanoma in patient tumor samples. In the future, these tumor samples will be informative as we continue to examine and identify additional genetic alterations in melanoma, providing information regarding the natural history and distribution of certain mutations. Future studies will use array comparative genomic hybridization to further investigate additional somatic mutations occurring in melanoma tumors and correlate these with clinical outcome, as well as provide insight into the pathogenesis of melanoma. These results may lead to further opportunities for clinical trials.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5557. doi:1538-7445.AM2012-5557

Distinct MHC gene expression patterns during progression of melanoma

Abnormal expression of major histocompatibility complex (MHC) molecules in melanoma has been reported previously. However, the MHC molecule expression patterns in different growth phases of melanoma and the underlying mechanisms are not well understood. Here, we demonstrate that in vertical growth phase (VGP) melanomas, MHC genes are subject to increased rates of DNA copy number gains, accompanied by increased expression, in comparison to normal melanocytes. In contrast, MHC expression in metastatic melanomas drastically decreased compared to VGP melanomas, despite still prevalent DNA copy number gains. Subsequent investigations found that the master transactivator of MHC genes, CIITA, was also significantly downregulated in metastatic melanomas when compared to VGP melanomas. This could be one of the mechanisms accounting for the discrepancy between DNA copy number and expression level in metastatic melanomas, a potentially separate mechanism of gene regulation. These results infer a dynamic role of MHC function in melanoma progression. We propose potential mechanisms for the overexpression of MHC molecules in earlier stages of melanoma as well as for its downregulation in metastatic melanomas.