Early Clearance of Plasma Epidermal Growth Factor Receptor Mutations as a Predictor of Outcome on Osimertinib in Advanced Non-Small Cell Lung Cancer; Exploratory Analysis from AURA3 and FLAURA.

PURPOSE: Plasma circulating tumor DNA (ctDNA) analysis is used for genotyping advanced non-small cell lung cancer (NSCLC); monitoring dynamic ctDNA changes may be used to predict outcomes. PATIENTS AND METHODS: This was a retrospective, exploratory analysis of two phase III trials [AURA3 (NCT02151981), FLAURA (NCT02296125)]. All patients had EGFR mutation-positive (EGFRm; ex19del or L858R) advanced NSCLC; AURA3 also included T790M-positive NSCLC. Osimertinib (FLAURA, AURA3), or comparator EGFR-tyrosine kinase inhibitor (EGFR-TKI; gefitinib/erlotinib; FLAURA), or platinum-based doublet chemotherapy (AURA3) was given. Plasma EGFRm was analyzed at baseline and Weeks 3/6 by droplet digital PCR. Outcomes were assessed by detectable/non-detectable baseline plasma EGFRm and plasma EGFRm clearance (non-detection) at Weeks 3/6. RESULTS: In AURA3 (n = 291), non-detectable versus detectable baseline plasma EGFRm had longer median progression-free survival [mPFS; HR, 0.48; 95% confidence interval (CI), 0.33-0.68; P < 0.0001]. In patients with Week 3 clearance versus non-clearance (n = 184), respectively, mPFS (months; 95% CI) was 10.9 (8.3-12.6) versus 5.7 (4.1-9.7) with osimertinib and 6.2 (4.0-9.7) versus 4.2 (4.0-5.1) with platinum-pemetrexed. In FLAURA (n = 499), mPFS was longer with non-detectable versus detectable baseline plasma EGFRm (HR, 0.54; 95% CI, 0.41-0.70; P < 0.0001). For Week 3 clearance versus non-clearance (n = 334), respectively, mPFS was 19.8 (15.1 to not calculable) versus 11.3 (9.5-16.5) with osimertinib and 10.8 (9.7-11.1) versus 7.0 (5.6-8.3) with comparator EGFR-TKI. Similar outcomes were observed by Week 6 clearance/non-clearance. CONCLUSIONS: Plasma EGFRm analysis as early as 3 weeks on-treatment has the potential to predict outcomes in EGFRm advanced NSCLC.

Candidate mechanisms of acquired resistance to first-line osimertinib in EGFR-mutated advanced non-small cell lung cancer.

Osimertinib, an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), potently and selectively inhibits EGFR-TKI-sensitizing and EGFR T790M resistance mutations. In the Phase III FLAURA study (NCT02296125), first-line osimertinib improved outcomes vs comparator EGFR-TKIs in EGFRm advanced non-small cell lung cancer. This analysis identifies acquired resistance mechanisms to first-line osimertinib. Next-generation sequencing assesses circulating-tumor DNA from paired plasma samples (baseline and disease progression/treatment discontinuation) in patients with baseline EGFRm. No EGFR T790M-mediated acquired resistance are observed; most frequent resistance mechanisms are MET amplification (n = 17; 16%) and EGFR C797S mutations (n = 7; 6%). Future research investigating non-genetic acquired resistance mechanisms is warranted.

Analysis of acquired resistance mechanisms to osimertinib in patients with EGFR-mutated advanced non-small cell lung cancer from the AURA3 trial.

Osimertinib, an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), potently and selectively inhibits EGFR-TKI-sensitizing and EGFR T790M resistance mutations. This analysis evaluates acquired resistance mechanisms to second-line osimertinib (n = 78) in patients with EGFR T790M advanced non-small cell lung cancer (NSCLC) from AURA3 (NCT02151981), a randomized phase 3 study comparing osimertinib with chemotherapy. Plasma samples collected at baseline and disease progression/treatment discontinuation are analyzed using next-generation sequencing. Half (50%) of patients have undetectable plasma EGFR T790M at disease progression and/or treatment discontinuation. Fifteen patients (19%) have >1 resistance-related genomic alteration; MET amplification (14/78, 18%) and EGFR C797X mutation (14/78, 18%).

Osimertinib + Savolitinib to Overcome Acquired MET-Mediated Resistance in Epidermal Growth Factor Receptor-Mutated, MET-Amplified Non-Small Cell Lung Cancer: TATTON.

MET-inhibitor and EGFR tyrosine kinase inhibitor (EGFR-TKI) combination therapy could overcome acquired MET-mediated osimertinib resistance. We present the final phase Ib TATTON (NCT02143466) analysis (Part B, n = 138/Part D, n = 42) assessing oral savolitinib 600 mg/300 mg once daily (q.d.) + osimertinib 80 mg q.d. in patients with MET-amplified, EGFR-mutated (EGFRm) advanced non-small cell lung cancer (NSCLC) and progression on prior EGFR-TKI. An acceptable safety profile was observed. In Parts B and D, respectively, objective response rates were 33% to 67% and 62%, and median progression-free survival (PFS) was 5.5 to 11.1 months and 9.0 months. Increased antitumor activity may occur with MET copy number ≥10. EGFRm circulating tumor DNA clearance on treatment predicted longer PFS in patients with detectable baseline ctDNA, while acquired resistance mechanisms to osimertinib + savolitinib were mediated by MET, EGFR, or KRAS alterations. SIGNIFICANCE: The savolitinib + osimertinib combination represents a promising therapy in patients with MET-amplified/overexpressed, EGFRm advanced NSCLC with disease progression on a prior EGFR-TKI. Acquired resistance mechanisms to this combination include those via MET, EGFR, and KRAS. On-treatment ctDNA dynamics can predict clinical outcomes and may provide an opportunity to inform earlier decision-making. This article is highlighted in the In This Issue feature, p. 1.

Osimertinib plus Selumetinib in EGFR-Mutated Non-Small Cell Lung Cancer After Progression on EGFR-TKIs: A Phase Ib, Open-Label, Multicenter Trial (TATTON Part B).

BACKGROUND: MEK/ERK inhibition can overcome acquired resistance to osimertinib in preclinical models. Osimertinib [EGFR-tyrosine kinase inhibitor (TKI)] plus selumetinib (MEK1/2 inhibitor) was assessed in the global TATTON study. METHODS: This multicenter, open-label, phase Ib study expansion cohort enrolled patients (aged ≥18 years) with MET-negative, EGFRm advanced NSCLC who had progressed on EGFR-TKIs. Patients were assigned to one of two cohorts by prior first- or second-generation or T790M-directed EGFR-TKI and received osimertinib 80 mg every day and intermittent selumetinib 75 mg twice a day orally. Safety and tolerability (primary objective) and antitumor activity determined by objective response rate (ORR), and progression-free survival (PFS) using RECIST v1.1 were assessed. Data cutoff: March 4, 2020. RESULTS: Forty-seven patients received treatment (prior first- or second-generation EGFR-TKI, n = 12; prior T790M-directed EGFR-TKI, n = 35). Forty-four (94%) patients were Asian; 30 (64%) had baseline exon 19 deletion. Most common AEs were diarrhea (89%), decreased appetite (40%), and stomatitis (32%); 11/47 patients (23%) had an AE Grade ≥3 possibly causally selumetinib-related. ORR was 66.7% [95% confidence interval (CI), 34.9-90.1] in the prior first- or second-generation EGFR-TKI group, 22.9% (95% CI, 10.4-40.1) in the prior T790M-directed EGFR-TKI group, and 34.0% (95% CI, 20.9-49.3) overall; median PFS was 15.0 (95% CI, 2.7-33.0), 2.8 (95% CI, 1.6-5.5), and 4.2 months (95% CI, 2.7-7.2), respectively. CONCLUSIONS: In this small study, AEs and tolerability of osimertinib plus selumetinib were as expected, on the basis of previous studies. The combination demonstrated antitumor activity supportive of further investigation in patients with MET-negative, EGFRm advanced NSCLC who had progressed on a previous EGFR-TKI.

A Novel Mouse Model for SNP in Steroid Receptor Co-Activator-1 Reveals Role in Bone Density and Breast Cancer Metastasis.

The steroid receptor coactivator-1 (SRC-1) is a nuclear receptor co-activator, known to play key roles in both estrogen response in bone and in breast cancer metastases. We previously demonstrated that the P1272S single nucleotide polymorphism (SNP; P1272S; rs1804645) in SRC-1 decreases the activity of estrogen receptor in the presence of selective estrogen receptor modulators (SERMs) and that it is associated with a decrease in bone mineral density (BMD) after tamoxifen therapy, suggesting it may disrupt the agonist action of tamoxifen. Given such dual roles of SRC-1 in the bone microenvironment and in tumor cell-intrinsic phenotypes, we hypothesized that SRC-1 and a naturally occurring genetic variant, P1272S, may promote breast cancer bone metastases. We developed a syngeneic, knock-in mouse model to study if the SRC-1 SNP is critical for normal bone homeostasis and bone metastasis. Our data surprisingly reveal that the homozygous SRC-1 SNP knock-in increases tamoxifen-induced bone protection after ovariectomy. The presence of the SRC-1 SNP in mammary glands resulted in decreased expression levels of SRC-1 and reduced tumor burden after orthotopic injection of breast cancer cells not bearing the SRC-1 SNP, but increased metastases to the lungs in our syngeneic mouse model. Interestingly, the P1272S SNP identified in a small, exploratory cohort of bone metastases from breast cancer patients was significantly associated with earlier development of bone metastasis. This study demonstrates the importance of the P1272S SNP in both the effect of SERMs on BMD and the development of tumor in the bone.

The genomic landscape of metastatic breast cancer: Insights from 11,000 tumors.

BACKGROUND: Metastatic breast cancer is the leading cause of cancer death in women, but the genomics of metastasis in breast cancer are poorly studied. METHODS: We explored a set of 11,616 breast tumors, including 5,034 metastases, which had undergone targeted sequencing during standard clinical care. RESULTS: Besides the known hotspot mutations in ESR1, we observed a metastatic enrichment of previously unreported, lower-prevalence mutations in the ligand-binding domain, implying that these mutations may also be functional. Furthermore, individual ESR1 hotspots are significantly enriched in specific metastatic tissues and histologies, suggesting functional differences between these mutations. Other alterations enriched across all metastases include loss of function of the CDK4 regulator CDKN1B, and mutations in the transcription factor CTCF. Mutations enriched at specific metastatic sites generally reflect biology of the target tissue and may be adaptations to growth in the local environment. These include PTEN and ASXL1 alterations in brain metastases and NOTCH1 alterations in skin. We observed an enrichment of KRAS, KEAP1, STK11 and EGFR mutations in lung metastases. However, the patterns of other mutations in these tumors indicate that these are misdiagnosed lung primaries rather than breast metastases. CONCLUSIONS: An order-of-magnitude increase in samples relative to previous studies allowed us to detect novel genomic characteristics of metastatic cancer and to expand and clarify previous findings.

ERBB3 and IGF1R Signaling Are Required for Nrf2-Dependent Growth in KEAP1-Mutant Lung Cancer.

Mutations in KEAP1 and NFE2L2 (encoding the protein Nrf2) are prevalent in both adeno and squamous subtypes of non-small cell lung cancer, as well as additional tumor indications. The consequence of these mutations is stabilized Nrf2 and chronic induction of a battery of Nrf2 target genes. We show that knockdown of Nrf2 caused modest growth inhibition of cells growing in two-dimension, which was more pronounced in cell lines expressing mutant KEAP1. In contrast, Nrf2 knockdown caused almost complete regression of established KEAP1-mutant tumors in mice, with little effect on wild-type (WT) KEAP1 tumors. The strong dependency on Nrf2 could be recapitulated in certain anchorage-independent growth environments and was not prevented by excess extracellular glutathione. A CRISPR screen was used to investigate the mechanism(s) underlying this dependence. We identified alternative pathways critical for Nrf2-dependent growth in KEAP1-mutant cell lines, including the redox proteins thioredoxin and peroxiredoxin, as well as the growth factor receptors IGF1R and ERBB3. IGF1R inhibition was effective in KEAP1-mutant cells compared with WT, especially under conditions of anchorage-independent growth. These results point to addiction of KEAP1-mutant tumor cells to Nrf2 and suggest that inhibition of Nrf2 or discrete druggable Nrf2 target genes such as IGF1R could be an effective therapeutic strategy for disabling these tumors. SIGNIFICANCE: This study identifies pathways activated by Nrf2 that are important for the proliferation and tumorigenicity of KEAP1-mutant non-small cell lung cancer.

A Novel Next-Generation Sequencing Approach to Detecting Microsatellite Instability and Pan-Tumor Characterization of 1000 Microsatellite Instability-High Cases in 67,000 Patient Samples.

Microsatellite instability (MSI) is an important biomarker for predicting response to immune checkpoint inhibitor therapy, as emphasized by the recent checkpoint inhibitor approval for MSI-high (MSI-H) solid tumors. Herein, we describe and validate a novel method for determining MSI status from a next-generation sequencing comprehensive genomic profiling assay using formalin-fixed, paraffin-embedded samples. This method is 97% (65/67) concordant with current standards, PCR and immunohistochemistry. We further apply this method to >67,000 patient tumor samples to identify genes and pathways that are enriched in MSI-stable or MSI-H tumor groups. Data show that although rare in tumors other than colorectal and endometrial carcinomas, MSI-H samples are present in many tumor types. Furthermore, the large sample set revealed that MSI-H tumors selectively share alterations in genes across multiple common pathways, including WNT, phosphatidylinositol 3-kinase, and NOTCH. Last, MSI is sufficient, but not necessary, for a tumor to have elevated tumor mutation burden. Therefore, MSI can be determined from comprehensive genomic profiling with high accuracy, allowing for efficient MSI-H detection across all tumor types, especially those in which routine use of immunohistochemistry or PCR-based assays would be impractical because of a rare incidence of MSI. MSI-H tumors are enriched in alterations in specific signaling pathways, providing a rationale for investigating directed immune checkpoint inhibitor therapies in combination with pathway-targeted therapies.

FGFR4 overexpression and hotspot mutations in metastatic ER+ breast cancer are enriched in the lobular subtype.

Invasive lobular carcinoma (ILC) is an understudied subtype of breast cancer that requires novel therapies in the advanced setting. To study acquired resistance to endocrine therapy in ILC, we have recently performed RNA-Sequencing on long-term estrogen deprived cell lines and identified FGFR4 overexpression as a top druggable target. Here, we show that FGFR4 expression also increases dramatically in endocrine-treated distant metastases, with an average fold change of 4.8 relative to the paired primary breast tumor for ILC, and 2.4-fold for invasive ductal carcinoma (IDC). In addition, we now report that FGFR4 hotspot mutations are enriched in metastatic breast cancer, with an additional enrichment for ILC, suggesting a multimodal selection of FGFR4 activation. These data collectively support the notion that FGFR4 is an important mediator of endocrine resistance in ILC, warranting future mechanistic studies on downstream signaling of overexpressed wild-type and mutant FGFR4.

Targeted mutation detection in breast cancer using MammaSeq™.

BACKGROUND: Breast cancer is the most common invasive cancer among women worldwide. Next-generation sequencing (NGS) has revolutionized the study of cancer across research labs around the globe; however, genomic testing in clinical settings remains limited. Advances in sequencing reliability, pipeline analysis, accumulation of relevant data, and the reduction of costs are rapidly increasing the feasibility of NGS-based clinical decision making. METHODS: We report the development of MammaSeq, a breast cancer-specific NGS panel, targeting 79 genes and 1369 mutations, optimized for use in primary and metastatic breast cancer. To validate the panel, 46 solid tumors and 14 plasma circulating tumor DNA (ctDNA) samples were sequenced to a mean depth of 2311× and 1820×, respectively. Variants were called using Ion Torrent Suite 4.0 and annotated with cravat CHASM. CNVKit was used to call copy number variants in the solid tumor cohort. The oncoKB Precision Oncology Database was used to identify clinically actionable variants. Droplet digital PCR was used to validate select ctDNA mutations. RESULTS: In cohorts of 46 solid tumors and 14 ctDNA samples from patients with advanced breast cancer, we identified 592 and 43 protein-coding mutations. Mutations per sample in the solid tumor cohort ranged from 1 to 128 (median 3), and the ctDNA cohort ranged from 0 to 26 (median 2.5). Copy number analysis in the solid tumor cohort identified 46 amplifications and 35 deletions. We identified 26 clinically actionable variants (levels 1-3) annotated by OncoKB, distributed across 20 out of 46 cases (40%), in the solid tumor cohort. Allele frequencies of ESR1 and FOXA1 mutations correlated with CA.27.29 levels in patient-matched blood draws. CONCLUSIONS: In solid tumor biopsies and ctDNA, MammaSeq detects clinically actionable mutations (OncoKB levels 1-3) in 22/46 (48%) solid tumors and in 4/14 (29%) of ctDNA samples. MammaSeq is a targeted panel suitable for clinically actionable mutation detection in breast cancer.

Frequent ESR1 and CDK Pathway Copy-Number Alterations in Metastatic Breast Cancer.

DNA sequencing has identified a limited number of driver mutations in metastatic breast cancer beyond single base-pair mutations in the estrogen receptor (ESR1). However, our previous studies and others have observed that structural variants, such as ESR1 fusions, may also play a role. Therefore, we expanded upon these observations by performing a comprehensive and highly sensitive characterization of copy-number (CN) alterations in a large clinical cohort of metastatic specimens. NanoString DNA hybridization was utilized to measure CN gains, amplifications, and deletions of 67 genes in 108 breast cancer metastases, and in 26 cases, the patient-matched primary tumor. For ESR1, a copyshift algorithm was applied to identify CN imbalances at exon-specific resolution and queried large data sets (>15,000 tumors) that had previously undergone next-generation sequencing (NGS). Interestingly, a subset of ER+ tumors showed increased ESR1 CN (11/82, 13%); three had CN amplifications (4%) and eight had gains (10%). Increased ESR1 CN was enriched in metastatic specimens versus primary tumors, and this was orthogonally confirmed in a large NGS data set. ESR1-amplified tumors showed a site-specific enrichment for bone metastases and worse outcomes than nonamplified tumors. No ESR1 CN amplifications and only one gain was identified in ER- tumors. ESR1 copyshift was present in 5 of the 11 ESR1-amplified tumors. Other frequent amplifications included ERBB2, GRB7, and cell-cycle pathway members CCND1 and CDK4/6, which showed mutually exclusivity with deletions of CDKN2A, CDKN2B, and CDKN1B. IMPLICATIONS: Copy-number alterations of ESR1 and key CDK pathway genes are frequent in metastatic breast cancers, and their clinical relevance should be tested further.

Actionable Activating Oncogenic ERBB2/HER2 Transmembrane and Juxtamembrane Domain Mutations.

Deregulated HER2 is a target of many approved cancer drugs. We analyzed 111,176 patient tumors and identified recurrent mutations in HER2 transmembrane domain (TMD) and juxtamembrane domain (JMD) that include G660D, R678Q, E693K, and Q709L. Using a saturation mutagenesis screen and testing of patient-derived mutations we found several activating TMD and JMD mutations. Structural modeling and analysis showed that the TMD/JMD mutations function by improving the active dimer interface or stabilizing an activating conformation. Further, we found that HER2 G660D employed asymmetric kinase dimerization for activation and signaling. Importantly, anti-HER2 antibodies and small-molecule kinase inhibitors blocked the activity of TMD/JMD mutants. Consistent with this, a G660D germline mutant lung cancer patient showed remarkable clinical response to HER2 blockade.

STK11/LKB1 Mutations and PD-1 Inhibitor Resistance in KRAS-Mutant Lung Adenocarcinoma.

KRAS is the most common oncogenic driver in lung adenocarcinoma (LUAC). We previously reported that STK11/LKB1 (KL) or TP53 (KP) comutations define distinct subgroups of KRAS-mutant LUAC. Here, we examine the efficacy of PD-1 inhibitors in these subgroups. Objective response rates to PD-1 blockade differed significantly among KL (7.4%), KP (35.7%), and K-only (28.6%) subgroups (P < 0.001) in the Stand Up To Cancer (SU2C) cohort (174 patients) with KRAS-mutant LUAC and in patients treated with nivolumab in the CheckMate-057 phase III trial (0% vs. 57.1% vs. 18.2%; P = 0.047). In the SU2C cohort, KL LUAC exhibited shorter progression-free (P < 0.001) and overall (P = 0.0015) survival compared with KRASMUT;STK11/LKB1WT LUAC. Among 924 LUACs, STK11/LKB1 alterations were the only marker significantly associated with PD-L1 negativity in TMBIntermediate/High LUAC. The impact of STK11/LKB1 alterations on clinical outcomes with PD-1/PD-L1 inhibitors extended to PD-L1-positive non-small cell lung cancer. In Kras-mutant murine LUAC models, Stk11/Lkb1 loss promoted PD-1/PD-L1 inhibitor resistance, suggesting a causal role. Our results identify STK11/LKB1 alterations as a major driver of primary resistance to PD-1 blockade in KRAS-mutant LUAC.Significance: This work identifies STK11/LKB1 alterations as the most prevalent genomic driver of primary resistance to PD-1 axis inhibitors in KRAS-mutant lung adenocarcinoma. Genomic profiling may enhance the predictive utility of PD-L1 expression and tumor mutation burden and facilitate establishment of personalized combination immunotherapy approaches for genomically defined LUAC subsets. Cancer Discov; 8(7); 822-35. ©2018 AACR.See related commentary by Etxeberria et al., p. 794This article is highlighted in the In This Issue feature, p. 781.

BRAF in Lung Cancers: Analysis of Patient Cases Reveals Recurrent BRAF Mutations, Fusions, Kinase Duplications, and Concurrent Alterations.

PURPOSE: Dabrafenib and trametinib are approved for the management of advanced non-small-cell lung cancers (NSCLCs) that harbor BRAF V600E mutations. Small series and pan-cancer analyses have identified non-V600 alterations as therapeutic targets. We sought to examine a large genomic data set to comprehensively characterize non-V600 BRAF alterations in lung cancer. PATIENTS AND METHODS: A total of 23,396 patients with lung cancer provided data to assay with comprehensive genomic profiling. Data were reviewed for predicted pathogenic BRAF base substitutions, short insertions and deletions, copy number changes, and rearrangements. RESULTS: Adenocarcinomas represented 65% of the occurrences; NSCLC not otherwise specified (NOS), 15%; squamous cell carcinoma, 12%; and small-cell lung carcinoma, 5%. BRAF was altered in 4.5% (1,048 of 23,396) of all tumors; 37.4% (n = 397) were BRAF V600E, 38% were BRAF non-V600E activating mutations, and 18% were BRAF inactivating. Rearrangements were observed at a frequency of 4.3% and consisted of N-terminal deletions (NTDs; 0.75%), kinase domain duplications (KDDs; 0.75%), and BRAF fusions (2.8%). The fusions involved three recurrent fusion partners: ARMC10, DOCK4, and TRIM24. BRAF V600E was associated with co-occurrence of SETD2 alterations, but other BRAF alterations were not and were instead associated with CDKN2A, TP53, and STK11 alterations (P < .05). Potential mechanisms of acquired resistance to BRAF V600E inhibition are demonstrated. CONCLUSION: This series characterized the frequent occurrence (4.4%) of BRAF alterations in lung cancers. Recurrent BRAF alterations in NSCLC adenocarcinoma are comparable to the frequency of other NSCLC oncogenic drivers, such as ALK, and exceed that of ROS1 or RET. This work supports a broad profiling approach in lung cancers and suggests that non-V600E BRAF alterations represent a subgroup of lung cancers in which targeted therapy should be considered.

High-Throughput Genomic Profiling of Adult Solid Tumors Reveals Novel Insights into Cancer Pathogenesis.

Genomic profiling is widely predicted to become a standard of care in clinical oncology, but more effective data sharing to accelerate progress in precision medicine will be required. Here, we describe cancer-associated genomic profiles from 18,004 unique adult cancers. The dataset was composed of 162 tumor subtypes including multiple rare and uncommon tumors. Comparison of alteration frequencies to The Cancer Genome Atlas identified some differences and suggested an enrichment of treatment-refractory samples in breast and lung cancer cohorts. To illustrate novelty within the dataset, we surveyed the genomic landscape of rare diseases and identified an increased frequency of NOTCH1 alterations in adenoid cystic carcinomas compared with previous studies. Analysis of tumor suppressor gene patterns revealed disease specificity for certain genes but broad inactivation of others. We identified multiple potentially druggable, novel and known kinase fusions in diseases beyond those in which they are currently recognized. Analysis of variants of unknown significance identified an enrichment of SMAD4 alterations in colon cancer and other rare alterations predicted to have functional impact. Analysis of established, clinically relevant alterations highlighted the spectrum of molecular changes for which testing is currently recommended, as well as opportunities for expansion of indications for use of approved targeted therapies. Overall, this dataset presents a new resource with which to investigate rare alterations and diseases, validate clinical relevance, and identify novel therapeutic targets. Cancer Res; 77(9); 2464-75. ©2017 AACR.

Genomic analysis of 63,220 tumors reveals insights into tumor uniqueness and targeted cancer immunotherapy strategies.

BACKGROUND: The integration of genomics with immunotherapy has potential value for cancer vaccine development. Given the clinical successes of immune checkpoint modulators, interest in cancer vaccines as therapeutic options has been revived. Current data suggest that each tumor contains a unique set of mutations (mutanome), thus requiring the creation of individualized cancer vaccines. However, rigorous analysis of non-individualized cancer immunotherapy approaches across multiple cancer types and in the context of known driver alterations has yet to be reported. We therefore set out to determine the feasibility of a generalizable cancer vaccine strategy based on targeting multiple neoantigens in an HLA-A/B subtype-directed manner. METHODS: A cancer gene-focused, hybrid capture-based genomic analysis was performed on 63,220 unique tumors. Neoantigens were predicted using a combined peptide processing and MHC-I binding prediction tool (IEDB) for all recurrent (>10 tumors) missense alterations and non-frameshift indels for the two most common HLA-A/B subtypes in North American/European populations. RESULTS: Despite being overwhelmingly unique overall, many mutanomes (~45%) contain at least one mutation from a set of ten mutations chosen to maximize the number of unique tumors. This held true for tumors driven by KRAS G12C (n = 1799), PIK3CA E545K (n = 1713), or EGFR L858R (n = 478) alterations, which define distinct sample subsets. We therefore hypothesized that sets of carefully selected mutations/neoantigens may allow the development of broadly applicable semi-universal cancer vaccines. To test the feasibility of such an approach, antigen processing and MHC-I binding prediction was applied for HLA subtypes A*01:01/B*08:01 and A*02:01/B*44:02. In tumors with a specific HLA type, 0.7 and 2.5% harbored at least one of a set of ten neoantigens predicted to bind to each subtype, respectively. In comparison, KRAS G12C-driven tumors produced similar results (0.8 and 2.6% for each HLA subtype, respectively), indicating that neoantigen targets still remain highly diverse even within the context of major driver mutations. CONCLUSIONS: This "best case scenario" analysis of a large tumor set across multiple cancer types and in the context of driver alterations reveals that semi-universal, HLA-specific cancer vaccine strategies will be relevant to only a small subset of the general population. Similar analysis of whole exome/genome sequencing, although not currently feasible at scale in a clinical setting, will likely uncover further diversity.

Intrinsic Subtype Switching and Acquired ERBB2/HER2 Amplifications and Mutations in Breast Cancer Brain Metastases.

IMPORTANCE: Patients with breast cancer (BrCa) brain metastases (BrM) have limited therapeutic options. A better understanding of molecular alterations acquired in BrM could identify clinically actionable metastatic dependencies. OBJECTIVE: To determine whether there are intrinsic subtype differences between primary tumors and matched BrM and to uncover BrM-acquired alterations that are clinically actionable. DESIGN, SETTING, AND PARTICIPANTS: In total, 20 cases of primary breast cancer tissue and resected BrM (10 estrogen receptor [ER]-negative and 10 ER-positive) from 2 academic institutions were included. Eligible cases in the discovery cohort harbored patient-matched primary breast cancer tissue and resected BrM. Given the rarity of patient-matched samples, no exclusion criteria were enacted. Two validation sequencing cohorts were used-a published data set of 17 patient-matched cases of BrM and a cohort of 7884 BrCa tumors enriched for metastatic samples. MAIN OUTCOMES AND MEASURES: Brain metastases expression changes in 127 genes within BrCa signatures, PAM50 assignments, and ERBB2/HER2 DNA-level gains. RESULTS: Overall, 17 of 20 BrM retained the PAM50 subtype of the primary BrCa. Despite this concordance, 17 of 20 BrM harbored expression changes (<2-fold or >2-fold) in clinically actionable genes including gains of FGFR4 (n = 6 [30%]), FLT1 (n = 4 [20%]), AURKA (n = 2 [10%]) and loss of ESR1 expression (n = 9 [45%]). The most recurrent expression gain was ERBB2/HER2, which showed a greater than 2-fold expression increase in 7 of 20 BrM (35%). Three of these 7 cases were ERBB2/HER2-negative out of 13 ERBB2/HER2-negative in the primary BrCa cohort and became immunohistochemical positive (3+) in the paired BrM with metastasis-specific amplification of the ERBB2/HER2 locus. In an independent data set, 2 of 9 (22.2%) ERBB2/HER2-negative BrCa switched to ERBB2/HER2-positive with 1 BrM acquiring ERBB2/HER2 amplification and the other showing metastatic enrichment of the activating V777L ERBB2/HER2 mutation. An expanded cohort revealed that ERBB2/HER2 amplification and/or mutation frequency was unchanged between local disease and metastases across all sites; however, a significant enrichment was appreciated for BrM (13% local vs 24% BrM; P < .001). CONCLUSIONS AND RELEVANCE: Breast cancer BrM commonly acquire alterations in clinically actionable genes, with metastasis-acquired ERBB2/HER2 alterations in approximately 20% of ERBB2/HER2-negative cases. These observations have immediate clinical implications for patients with ERBB2/HER2-negative breast cancer and support comprehensive profiling of metastases to inform clinical care.

Epigenomic Deconvolution of Breast Tumors Reveals Metabolic Coupling between Constituent Cell Types.

Cancer progression depends on both cell-intrinsic processes and interactions between different cell types. However, large-scale assessment of cell type composition and molecular profiles of individual cell types within tumors remains challenging. To address this, we developed epigenomic deconvolution (EDec), an in silico method that infers cell type composition of complex tissues as well as DNA methylation and gene transcription profiles of constituent cell types. By applying EDec to The Cancer Genome Atlas (TCGA) breast tumors, we detect changes in immune cell infiltration related to patient prognosis, and a striking change in stromal fibroblast-to-adipocyte ratio across breast cancer subtypes. Furthermore, we show that a less adipose stroma tends to display lower levels of mitochondrial activity and to be associated with cancerous cells with higher levels of oxidative metabolism. These findings highlight the role of stromal composition in the metabolic coupling between distinct cell types within tumors.