James Sun

Development and validation of a clinical cancer genomic profiling test based on massively parallel DNA sequencing

As more clinically relevant cancer genes are identified, comprehensive diagnostic approaches are needed to match patients to therapies, raising the challenge of optimization and analytical validation of assays that interrogate millions of bases of cancer genomes altered by multiple mechanisms. Here we describe a test based on massively parallel DNA sequencing to characterize base substitutions, short insertions and deletions (indels), copy number alterations and selected fusions across 287 cancer-related genes from routine formalin-fixed and paraffin-embedded (FFPE) clinical specimens. We implemented a practical validation strategy with reference samples of pooled cell lines that model key determinants of accuracy, including mutant allele frequency, indel length and amplitude of copy change. Test sensitivity achieved was 95–99% across alteration types, with high specificity (positive predictive value >99%). We confirmed accuracy using 249 FFPE cancer specimens characterized by established assays. Application of the test to 2,221 clinical cases revealed clinically actionable alterations in 76% of tumors, three times the number of actionable alterations detected by current diagnostic tests.

Emergence of Constitutively Active Estrogen Receptor-α Mutations in Pretreated Advanced Estrogen Receptor–Positive Breast Cancer

Purpose: We undertook this study to determine the prevalence of estrogen receptor (ER) α (ESR1) mutations throughout the natural history of hormone-dependent breast cancer and to delineate the functional roles of the most commonly detected alterations. Experimental Design: We studied a total of 249 tumor specimens from 208 patients. The specimens include 134 ER-positive (ER+/HER2−) and, as controls, 115 ER-negative (ER−) tumors. The ER+ samples consist of 58 primary breast cancers and 76 metastatic samples. All tumors were sequenced to high unique coverage using next-generation sequencing targeting the coding sequence of the estrogen receptor and an additional 182 cancer-related genes. Results: Recurring somatic mutations in codons 537 and 538 within the ligand-binding domain of ER were detected in ER+ metastatic disease. Overall, the frequency of these mutations was 12% [9/76; 95% confidence interval (CI), 6%–21%] in metastatic tumors and in a subgroup of patients who received an average of 7 lines of treatment the frequency was 20% (5/25; 95% CI, 7%–41%). These mutations were not detected in primary or treatment-naïve ER+ cancer or in any stage of ER− disease. Functional studies in cell line models demonstrate that these mutations render estrogen receptor constitutive activity and confer partial resistance to currently available endocrine treatments. Conclusions: In this study, we show evidence for the temporal selection of functional ESR1 mutations as potential drivers of endocrine resistance during the progression of ER+ breast cancer. Clin Cancer Res; 20(7); 1757–67. ©2014 AACR.

Rucaparib in relapsed, platinum-sensitive high-grade ovarian carcinoma (ARIEL2 Part 1): an international, multicentre, open-label, phase 2 trial

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

Targeted Next Generation Sequencing Identifies Markers of Response to PD-1 Blockade

Mutational load, by whole exome sequencing, can correlate with immunotherapy responses. Assessing melanoma mutational load of a fraction of the genome, by hybrid capture-based NGS, provided an accurate surrogate for WES determinations, and predicted response to anti-PD-1. Therapeutic antibodies blocking programmed death-1 and its ligand (PD-1/PD-L1) induce durable responses in a substantial fraction of melanoma patients. We sought to determine whether the number and/or type of mutations identified using a next-generation sequencing (NGS) panel available in the clinic was correlated with response to anti–PD-1 in melanoma. Using archival melanoma samples from anti–PD-1/PD-L1-treated patients, we performed hybrid capture–based NGS on 236–315 genes and T-cell receptor (TCR) sequencing on initial and validation cohorts from two centers. Patients who responded to anti–PD-1/PD-L1 had higher mutational loads in an initial cohort (median, 45.6 vs. 3.9 mutations/MB; P = 0.003) and a validation cohort (37.1 vs. 12.8 mutations/MB; P = 0.002) compared with nonresponders. Response rate, progression-free survival, and overall survival were superior in the high, compared with intermediate and low, mutation load groups. Melanomas with NF1 mutations harbored high mutational loads (median, 62.7 mutations/MB) and high response rates (74%), whereas BRAF/NRAS/NF1 wild-type melanomas had a lower mutational load. In these archival samples, TCR clonality did not predict response. Mutation numbers in the 315 genes in the NGS platform strongly correlated with those detected by whole-exome sequencing in The Cancer Genome Atlas samples, but was not associated with survival. In conclusion, mutational load, as determined by an NGS platform available in the clinic, effectively stratified patients by likelihood of response. This approach may provide a clinically feasible predictor of response to anti–PD-1/PD-L1. Cancer Immunol Res; 4(11); 959–67. ©2016 AACR.

Relapsed Classic E-Cadherin (CDH1)–Mutated Invasive Lobular Breast Cancer Shows a High Frequency of HER2 (ERBB2) Gene Mutations

Purpose: We queried whether comprehensive genomic profiling using a next-generation sequencing–based assay could identify novel and unanticipated targets of therapy for patients with relapsed invasive lobular carcinoma (ILC). Experimental Design: DNA sequencing (Illumina HiSeq 2000) was conducted for 3,320 exons of 182 cancer-related genes and 37 introns of 14 genes frequently rearranged in cancer on indexed, adaptor-ligated, hybridization-captured libraries using DNA isolated from formalin-fixed paraffin-embedded sections from 22 histologically verified ILC. Results: A total of 75 genomic alterations were identified with an average of 3.4 alterations per tumor (range, 1–6), of which 35 were actionable for an average of 1.59 actionable alterations per patient (range, 0–3). Nineteen of 22 (86%) of the ILC samples harbored at least one actionable alteration. Six (27%) cases featured alterations in ERRB2 including 4 (18%) with ERBB2 mutation, 1 (5%) with an ERBB2 gene fusion, and 1 (5%) with an ERBB2 copy number gain (amplification). The enrichment of ERBB2 mutations/fusion in CDH1-mutated ILC (5 of 22, 23%) compared with the 5 ERBB2 mutations in a series of 286 non-CDH1-mutated breast cancers from which the ILC cases were obtained (5 of 286, 2%) was significant (P = 0.0006). Conclusions: Comprehensive genomic profiling of relapsed CDH1-mutated ILC revealed actionable genomic alterations in 86% of cases, featured a high incidence of ERBB2 alterations, and can reveal actionable alterations that can inform treatment decisions for patients with ILC. Clin Cancer Res; 19(10); 2668–76. ©2013 AACR.

Secondary Somatic Mutations Restoring RAD51C and RAD51D Associated with Acquired Resistance to the PARP Inhibitor Rucaparib in High-Grade Ovarian Carcinoma

High-grade epithelial ovarian carcinomas containing mutated BRCA1 or BRCA2 (BRCA1/2) homologous recombination (HR) genes are sensitive to platinum-based chemotherapy and PARP inhibitors (PARPi), while restoration of HR function due to secondary mutations in BRCA1/2 has been recognized as an important resistance mechanism. We sequenced core HR pathway genes in 12 pairs of pretreatment and postprogression tumor biopsy samples collected from patients in ARIEL2 Part 1, a phase II study of the PARPi rucaparib as treatment for platinum-sensitive, relapsed ovarian carcinoma. In 6 of 12 pretreatment biopsies, a truncation mutation in BRCA1, RAD51C, or RAD51D was identified. In five of six paired postprogression biopsies, one or more secondary mutations restored the open reading frame. Four distinct secondary mutations and spatial heterogeneity were observed for RAD51CIn vitro complementation assays and a patient-derived xenograft, as well as predictive molecular modeling, confirmed that resistance to rucaparib was associated with secondary mutations.Significance: Analyses of primary and secondary mutations in RAD51C and RAD51D provide evidence for these primary mutations in conferring PARPi sensitivity and secondary mutations as a mechanism of acquired PARPi resistance. PARPi resistance due to secondary mutations underpins the need for early delivery of PARPi therapy and for combination strategies. Cancer Discov; 7(9); 984-98. ©2017 AACR.See related commentary by Domchek, p. 937See related article by Quigley et al., p. 999See related article by Goodall et al., p. 1006This article is highlighted in the In This Issue feature, p. 920.

Non-V600BRAF Mutations Define a Clinically Distinct Molecular Subtype of Metastatic Colorectal Cancer

Purpose Molecular diagnostic testing has become an integral part of the evaluation of patients with metastatic colorectal cancer (CRC). Expanded mutational testing, such as next-generation sequencing (NGS), often identifies mutations with unclear clinical or prognostic implications. One such example is BRAF mutations that occur outside of codon 600 (non-V600 BRAF mutations). Methods We conducted this multicenter, retrospective cohort study to characterize the clinical, pathologic, and survival implications of non-V600 BRAF mutations in metastatic CRC. We pooled patients in whom non-V600 BRAF mutations were identified from NGS databases at three large molecular genetics reference laboratories. Results A total of 9,643 patients with metastatic CRC underwent NGS testing. We identified 208 patients with non-V600 BRAF mutations, which occurred in 2.2% of all patients tested and accounted for 22% of all BRAF mutations identified. Cancers with non-V600 BRAF mutations, compared with cancers with V600E BRAF (V600E BRAF) mutations, were found in patients who were significantly younger (58 v 68 years, respectively), fewer female patients (46% v 65%, respectively), and patients who had fewer high-grade tumors (13% v 64%, respectively) or right-sided primary tumors (36% v 81%, respectively). Median overall survival was significantly longer in patients with non-V600 BRAF-mutant metastatic CRC compared with those with both V600E BRAF-mutant and wild-type BRAF metastatic CRC (60.7 v 11.4 v 43.0 months, respectively; P < .001). In multivariable analysis, non-V600 BRAF mutation was independently associated with improved overall survival (hazard ratio, 0.18; P < .001). Conclusion Non-V600 BRAF mutations occur in approximately 2.2% of patients with metastatic CRC and define a clinically distinct subtype of CRC with an excellent prognosis.

Comprehensive genomic profiling of anal squamous cell carcinoma reveals distinct genomically defined classes

BACKGROUND Squamous cell cancers of the anal canal (ASCC) are increasing in frequency and lack effective therapies for advanced disease. Although an association with human papillomavirus (HPV) has been established, little is known about the molecular characterization of ASCC. A comprehensive genomic analysis of ASCC was undertaken to identify novel genomic alterations (GAs) that will inform therapeutic choices for patients with advanced disease. PATIENTS AND METHODS Hybrid-capture-based next-generation sequencing of exons from 236 cancer-related genes and intronic regions from 19 genes commonly rearranged in cancer was performed on 70 patients with ASCC. HPV status was assessed by aligning tumor sequencing reads to HPV viral genomes. GAs were identified using an established algorithm and correlated with HPV status. RESULTS Sixty-one samples (87%) were HPV-positive. A mean of 3.5 GAs per sample was identified. Recurrent alterations in phosphoinositol-3-kinase pathway (PI3K/AKT/mTOR) genes including amplifications and homozygous deletions were present in 63% of cases. Clinically relevant GAs in genes involved in DNA repair, chromatin remodeling, or receptor tyrosine kinase signaling were observed in 30% of cases. Loss-of-function mutations in TP53 and CDKN2A were significantly enhanced in HPV-negative cases (P < 0.0001). CONCLUSIONS This is the first comprehensive genomic analysis of ASCC, and the results suggest new therapeutic approaches. Differing genomic profiles between HPV-associated and HPV-negative ASCC warrants further investigation and may require novel therapeutic and preventive strategies.

Loss of Heterozygosity at the CYP2D6 Locus in Breast Cancer: Implications for Germline Pharmacogenetic Studies

BACKGROUND Controversy exists regarding the impact of CYP2D6 genotype on tamoxifen responsiveness. We examined loss of heterozygosity (LOH) at the CYP2D6 locus and determined its impact on genotyping error when tumor tissue is used as a DNA source. METHODS Genomic tumor data from the adjuvant and metastatic settings (The Cancer Genome Atlas [TCGA] and Foundation Medicine [FM]) were analyzed to characterize the impact of CYP2D6 copy number alterations (CNAs) and LOH on Hardy Weinberg equilibrium (HWE). Additionally, we analyzed CYP2D6 *4 genotype from formalin-fixed paraffin-embedded (FFPE) tumor blocks containing nonmalignant tissue and buccal (germline) samples from patients on the North Central Cancer Treatment Group (NCCTG) 89-30-52 tamoxifen trial. All statistical tests were two-sided. RESULTS In TCGA samples (n =627), the CYP2D6 LOH rate was similar in estrogen receptor (ER)-positive (41.2%) and ER-negative (35.2%) but lower in HER2-positive tumors (15.1%) (P < .001). In FM ER+ samples (n = 290), similar LOH rates were observed (40.8%). In 190 NCCTG samples, the agreement between CYP2D6 genotypes derived from FFPE tumors and FFPE tumors containing nonmalignant tissue was moderate (weighted Kappa = 0.74; 95% CI = 0.63 to 0.84). Comparing CYP2D6 genotypes derived from buccal cells to FFPE tumor DNA, CYP2D6*4 genotype was discordant in six of 31(19.4%). In contrast, there was no disagreement between CYP2D6 genotypes derived from buccal cells with FFPE tumors containing nonmalignant tissue. CONCLUSIONS LOH at the CYP2D6 locus is common in breast cancer, resulting in potential misclassification of germline CYP2D6 genotypes. Tumor DNA should not be used to determine germline CYP2D6 genotype without sensitive techniques to detect low frequency alleles and quality control procedures appropriate for somatic DNA.

Oncogenic ALK Fusion in Rare and Aggressive Subtype of Colorectal Adenocarcinoma as a Potential Therapeutic Target

Purpose: Chromosomal translocations in the anaplastic lymphoma kinase (ALK) gene have been identified as oncogenic drivers in lung adenocarcinomas and other tumors, recently including rare cases of colorectal carcinoma. We identified a patient with refractory metastatic colorectal carcinoma harboring a STRN–ALK gene fusion who achieved an exceptional clinical benefit to the ALK inhibitor ceritinib. Our goal was to further define the clinicopathologic features of ALK-rearranged colorectal carcinoma in a large cohort. Experimental Design: Clinical cases of colorectal carcinoma evaluated by comprehensive genomic profiling (CGP) or by ALK immunohistochemistry (IHC) were reviewed retrospectively. FISH and microsatellite instability (MSI) analyses were performed. Results: Nine colorectal carcinoma cases harbored ALK gene fusions. Six cases were identified by CGP of 3,157 colorectal carcinoma (0.2%) and three by IHC of 2,980 colorectal carcinoma (0.1%). The ALK fusions involved known ALK partners EML4, C2orf44, CAD, and the novel STRN, PPP1R21, SENPF, MAPRE3, and PRKAP1B partners. These advanced-stage colorectal carcinomas lacked mutations in other oncogenic drivers, predominantly involved the proximal colon, and often exhibited MSI and mucinous phenotype. The index patient was treated with the ALK inhibitor ceritinib, resulting in a marked decrease in size of a skin metastasis, and resolution by computerized tomography of all contrast enhancing tumor. After 9 months of treatment, biopsy of progressive disease demonstrated a KRAS mutation, consistent with acquired resistance to ceritinib. Conclusions: Colorectal carcinoma harboring ALK fusions represent a rare aggressive subtype of colorectal carcinoma with distinct clinicopathologic features. This report provides the first clinical evidence that such patients may benefit from targeted monotherapy with ALK inhibitors. Clin Cancer Res; 22(15); 3831–40. ©2016 AACR.