A genome-wide association study implicates NR2F2 in lymphangioleiomyomatosis pathogenesis

INTRODUCTION

Lymphangioleiomyomatosis (LAM) occurs either associated with tuberous sclerosis complex (TSC) or as sporadic disease (S-LAM). Risk factors for development of S-LAM are unknown. We hypothesised that DNA sequence variants outside of TSC2/TSC1 might be associated with susceptibility for S-LAM and performed a genome-wide association study (GWAS).

METHODS

Genotyped and imputed data on 5 426 936 single nucleotide polymorphisms (SNPs) in 426 S-LAM subjects were compared, using conditional logistic regression, with similar data from 852 females from COPDGene in a matched case-control design. For replication studies, genotypes for 196 non-Hispanic White female S-LAM subjects were compared with three different sets of controls. RNA sequencing and immunohistochemistry analyses were also performed.

RESULTS

Two noncoding genotyped SNPs met genome-wide significance: rs4544201 and rs2006950 (p=4.2×10^-8 and 6.1×10^-9, respectively), which are in the same 35 kb linkage disequilibrium block on chromosome 15q26.2. This association was replicated in an independent cohort. NR2F2 (nuclear receptor subfamily 2 group F member 2), a nuclear receptor and transcription factor, was the only nearby protein-coding gene. NR2F2 expression was higher by RNA sequencing in one abdominal LAM tumour and four kidney angiomyolipomas, a LAM-related tumour, compared with all cancers from The Cancer Genome Atlas. Immunohistochemistry showed strong nuclear expression in both LAM and angiomyolipoma tumours.

CONCLUSIONS

SNPs on chromosome 15q26.2 are associated with S-LAM, and chromatin and expression data suggest that this association may occur through effects on NR2F2 expression, which potentially plays an important role in S-LAM development.

MET IHC Is a Poor Screen for MET Amplification or MET Exon 14 Mutations in Lung Adenocarcinomas: Data from a Tri-Institutional Cohort of the Lung Cancer Mutation Consortium

INTRODUCTION

MNNG HOS Transforming gene (MET) amplification and MET exon 14 (METex14) alterations in lung cancers affect sensitivity to MET proto-oncogene, receptor tyrosine kinase (MET [also known by the alias hepatocyte growth factor receptor]) inhibitors. Fluorescence in situ hybridization (FISH), next-generation sequencing (NGS), and immunohistochemistry (IHC) have been used to evaluate MET dependency. Here, we have determined the association of MET IHC with METex14 mutations and MET amplification.

METHODS

We collected data on a tri-institutional cohort from the Lung Cancer Mutation Consortium. All patients had metastatic lung adenocarcinomas and no prior targeted therapies. MET IHC positivity was defined by an H-score of 200 or higher using SP44 antibody. MET amplification was defined by copy number fold change of 1.8x or more with use of NGS or a MET-to-centromere of chromosome 7 ratio greater than 2.2 with use of FISH.

RESULTS

We tested tissue from 181 patients for MET IHC, MET amplification, and METex14 mutations. Overall, 71 of 181 patients (39%) were MET IHC-positive, three of 181 (2%) were MET-amplified, and two of 181 (1%) harbored METex14 mutations. Of the MET-amplified cases, two were FISH positive with MET-to-centromere of chromosome 7 ratios of 3.1 and 3.3, one case was NGS positive with a fold change of 4.4x, and one of the three cases was MET IHC-positive. Of the 71 IHC-positive cases, one (1%) was MET-amplified and two (3%) were METex14-mutated. Of the MET IHC-negative cases, two of 110 (2%) were MET-amplified.

CONCLUSIONS

In this study, nearly all MET IHC-positive cases were negative for MET amplification or METex14 mutations. MET IHC can also miss patients with MET amplification. The limited number of MET-amplified cases in this cohort makes it challenging to demonstrate an association between MET IHC and MET amplification. Nevertheless, IHC appears to be an inefficient screen for these genomic changes. MET amplification or METex14 mutations can best be detected by FISH and a multiplex NGS panel.

Phenotypic distinctions between mosaic forms of tuberous sclerosis complex

Purpose:

To determine if mosaic tuberous sclerosis complex (TSC) can be stratified into subtypes that correspond with prognosis and extent of disease.

Methods:

Next-generation sequencing of skin tumor and other samples was used to identify patients with mosaic pathogenic variants in TSC1 or TSC2. Extent of disease, onset age, and family history of TSC were determined through retrospective analysis of patient records.

Results:

The median number of disease findings and age at penetrance differed between mosaic patients with asymmetrically distributed facial angiofibromas (4 findings, 24y, n=7), mosaic patients with bilaterally symmetric facial angiofibromas (8 findings, 10y, n=12), and germline TSC patients (10 findings, 4y, n=29). Cutaneous and internal organ involvement positively correlated in mosaic (R=0.62, p=0.005), but not germline (R=−0.24, p=0.24) TSC. Variant allele fraction (VAF) in the blood (range: 0-19%) positively correlated with the number of major features (R=0.55, p=0.028). Five had a TSC2 variant identified in the skin that was below detection in the blood. One of 12 children from a mosaic parent had TSC.

Conclusion:

The phenotype of mosaic TSC ranged from mild to indistinguishable from germline disease. Patients with mosaicism and asymmetric facial angiofibromas exhibited fewer findings, later onset, and lower VAF in the blood.

Association of polybromo-associated BAF (PBAF) complex mutations with overall survival (OS) in cancer patients (pts) treated with checkpoint inhibitors (ICIs)

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Background: ICIs have shown benefit across several metastatic carcinomas, yet predictive biomarkers are still lacking. 20% of malignancies harbor alterations in ≥1gene that is part of PBAF complex. With recent data suggesting an association between PBRM1 mutations (mts) and outcomes in renal cell carcinoma (RCC) pts treated with ICIs (Miao, Science, 2018), we examined the association between PBAF mts and OS in ICI-treated patients across several solid cancer (ca) types. Methods: Of 6007 pts with different ca histologies and targeted exome sequencing (Oncopanel) at Dana Farber Cancer institute (DFCI), 138 pts had truncating mts in any PBAF gene (SMARCA4, PBRM1, and ARID2) or oncogenic missense mts in SMARCA4 and were treated with ICIs. 138 histology-matched DFCI pts had none. A publicly-available cohort (2:1 histology matched) from Memorial Sloan Kettering (MSKCC) (Samstein et al., Nature Genetics, 2019) of 621 ca pts (PBAF mutant [MT] = 207, PBAF wild type [WT] = 414) treated with ICIs was analyzed for association between PBAF mts and OS. OS was defined from time from ICI initiation. OS was compared by Cox regression between PBAF MT and PBAF WT. Hazard ratio (HR) was derived using univariable and multivariable analysis (MVA) adjusted for ICI regimen (single vs combination) and age. Results: Median (Md) follow-up for the combined cohort (n = 897) was 27 months (m). Major histologies were non-small cell lung ca (268; 29.9%), melanoma (220; 24.5%), RCC (181; 20.2%), and bladder ca (65; 7.2%). Results on univariable and MVA analyses from individual and combined cohorts are presented below. Conclusions: PBAF mts are associated with survival in ICI-treated ca pts. Work in progress with non-ICI treated pts will determine if this is prognostic or predictive of response. [Table: see text]

Germline variants in urothelial carcinoma: Analysis of pathogenic and likely pathogenic variants in 645 subjects

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Background: While small studies have supported a genetic cancer predisposition among subjects with urothelial carcinoma (UC), systematic germline evaluation of this population is lacking. Here, we report the prevalence of germline variants among subjects with UC from multiple centers completing panel-based testing at a large, commercial laboratory. Methods: 1149 UC subjects underwent germline testing of 1 to 126 genes using massively parallel sequencing with customized capture bait-sets to analyze exonic regions, flanking intronic sequences, and copy number alterations. Pathogenic (P) and likely pathogenic (LP) were confirmed using orthogonal technology in accordance with Invitae standard operating practices. Analysis was limited to 645 subjects who completed testing of a shared set of 42 genes. P/LP variants including single nucleotide variants/indels/ copy number variants are reported. De-identified personal and family cancer histories were evaluated. Fisher’s Exact test and the Mann-Whitney test were used to analyze categorical and continuous variables respectively. Results: Among the 645 UC subjects with 42-gene testing for any indication, median age at testing was 60 years (6-88) and 326 (51%) were female. P/LP variants were identified in 21 (50%) of the 42 genes in 98 (15%) of subjects, including Lynch syndrome genes (n = 26 [4%]), BRCA1/2 (n = 16 [2.5%]), CHEK2 (n = 15 [2.3%]), and heterozygous MUTYH (n = 12 [1.9%]). Among 18 DNA damage repair (DDR) genes assessed, 90 P/LP variants were detected in 88 subjects (12.2%). There was no significant association between presence of a DDR gene variant and age at diagnosis, gender or reported family history of UC in a first degree relative (n = 48). Among subjects with documented history of UC only without other cancers (n = 195), 24 (12.3%) had P/ LP variants, of which 23 (11.8%) were in a DDR gene. Conclusions: Germline P/LP variants were identified in 15% of UC subjects most of which (92%) were in DDR genes, including 27% in Lynch syndrome genes. PARP and T-cell checkpoint inhibitors may warrant evaluation in subjects with germline DDR mutations. Further validation in unselected UC pts is warranted to propose examining germline P/LP variants in all UC patients.

Neoadjuvant atezolizumab in resectable non-small cell lung cancer (NSCLC): Interim analysis and biomarker data from a multicenter study (LCMC3)

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Background: Small pilot studies (e.g., N Engl J Med. 2018;378:1976) have shown that preoperative immune checkpoint inhibitor therapy may be of benefit in early-stage NSCLC. This large multicenter trial assesses the benefit of neoadjuvant treatment with atezolizumab (atezo; NCT02927301). Methods: Patients (pts) with stages IB to selected IIIB resectable NSCLC receive 2 cycles of atezo 1200 mg (days 1, 22) then undergo resection (day 40 ± 10). Primary tumor +/- node biopsies and blood samples are obtained before atezo and at surgery for biomarker studies. The primary endpoint is major pathological response (MPR), defined as ≤ 10% viable tumor cells in the resection specimen. Secondary endpoints include safety and correlation of response with PD-L1 expression, tumor mutation burden (TMB) and gene expression signatures. Results: For this interim efficacy analysis (5 Sep 2018 data cut), we report on the first 101 of 180 planned pts: 47 males, median age, 64 y; all ECOG PS 0-1; 23 current and 68 former smokers; 66 non-squamous NSCLC; clinical stages IB/IIA/IIB/IIIA/IIIB n = 11/16/28/39/7. There were 2 treatment-unrelated Gr 5 AEs (cardiac death post surgical resection; death due to disease progression), 29 Gr 3-4 AEs (6 [6%] treatment related). 90 pts had surgery. Excluding 8 pts who had driver mutations (7 EGFR, 1 ALK, no MPR), MPR rate was 15/82 (18%, 95% CI 11%-28%), 4 pts had pathological complete response (pCR). By RECIST, 6/82 pts had PR, 72 had SD and 4 had PD. Two of 26 (8%) PD-L1− (TC0 and IC0, clone SP142) and 10 of 35 (29%) PD-L1+ had MPR ( P= 0.055). Five of 44 (11%) TPS < 50 (PD-L1 clone 22C3) and 7 of 20 (35%) TPS > 50 had MPR ( P= 0.040). Exome sequencing data was available for 47/101 pts. Median TMB was 10.4 (range, 1.5-46.5) mutations per Mb and was not different in those with MPR compared with those without MPR. Further analysis of TMB, mutation signatures, and gene expression profiling is ongoing. Conclusions: Atezo in the neoadjuvant setting was well tolerated, and pCR and MPR rates are encouraging in this large multicenter trial. Efficacy interim analysis passed its futility boundary, and study enrollment continues. Safety, efficacy results and ongoing correlative analyses will be presented. Clinical trial information: NCT02927301.

ABI-009 (nab-sirolimus) in advanced malignant perivascular epithelioid cell tumors (PEComa): Preliminary efficacy, safety, and mutational status from AMPECT, an open label phase II registration trial

11005

Background: Malignant PEComa is a rare, aggressive sarcoma, with no approved treatment or prior clinical trials. Case reports suggest mTOR activation through mutations or deletions of TSC1 or TSC2 and activity of mTOR inhibitors in this disease. ABI-009 is an albumin-bound mTOR inhibitor with increased tumor uptake. The AMPECT trial is the first prospective study in malignant PEComa. Methods: Eligible patients (pts) with centrally confirmed PEComa receive ABI-009 (100 mg/m2 IV, wkly, 2/3 wks) until progression or unacceptable toxicity. Primary endpoint: ORR by independent review (IR), assessed every 6 wks (RECIST v1.1). Secondary endpoints: duration of response (DOR), PFS6, PFS, and safety. Exploratory endpoints (EE): investigator-assessed (IA) outcomes and mutational status. Sample size: 30 efficacy-evaluable pts based on target ORR of 30% (primary analysis planned when all pts treated ≥6 mo). Results: EE and safety are reported (IR pending). As of Feb 12, 2019, enrollment is complete; 34 pts treated, 31 evaluable for efficacy, 42% (13/31) pts ongoing Rx. IA ORR is 42% PR (13/31, 95% CI: 24.5, 60.9), 35% SD (11/31), and 23% PD (7/31); 69% of PRs were reached at 1st restaging (wk 6); 69% PRs are ongoing, with 5 pts >1yr and 2 pt >2 yrs on Rx (all ongoing). Other IA outcomes: median DOR is not reached; PFS6 is 66%; median PFS is 8.9 mo (95% CI: 5.5, -). The most common (>30%) nonhematologic treatment-related AEs (TRAEs) of any grade: mucositis (65%), fatigue (53%), nausea/weight loss (35% each), diarrhea (32%); the most common (>15%) hematologic TRAEs: anemia (44%) and thrombocytopenia (18%). Pneumonitis (15%) was G1/G2. The most common (>10%) G3 TRAEs: mucositis (18%), anemia (12%); No grade ≥4 TRAEs. TSC1 or TSC2 mutations occurred in 5 and 9 (no overlap) of 25 pts with known mutational status, respectively. PR was seen in 100% (9/9) pts with TSC2 mutation, 20% (1/5) pts with TSC1 mutation, and 9% (1/11) pts without mutation in TSC1 or TSC2, P < 0.0001 (2x3 Fisher exact test). PR was significantly higher in pts with TSC2 mutations vs pts without mutation in TSC1 or TSC2, P = 0.0001 (Fisher exact test). Disease control (PR+SD) was seen in 93% (13/14) pts with TSC1 or TSC2 mutations vs 55% (6/11) pts without mutation in TSC1 or TSC2, P = NS. Conclusions: Preliminary IA outcomes showed that ABI-009 treatment of PEComa resulted in substantial and durable responses with manageable toxicities. TSC2 mutations were associated with IA response. Clinical trial information: NCT02494570.

The Codon 72 TP53 Polymorphism Contributes to TSC Tumorigenesis through the Notch-Nodal Axis

We discovered that 90.3% of patients with angiomyolipomas, lymphangioleiomyomatosis (LAM), and tuberous sclerosis complex (TSC) carry the arginine variant of codon 72 (R72) of TP53 and that R72 increases the risk for angiomyolipoma. R72 transactivates NOTCH1 and NODAL better than the proline variant of codon 72 (P72); therefore, the expression of NOTCH1 and NODAL is increased in angiomyolipoma cells that carry R72. The loss of Tp53 and Tsc1 within nestin-expressing cells in mice resulted in the development of renal cell carcinomas (RCC) with high Notch1 and Nodal expression, suggesting that similar downstream mechanisms contribute to tumorigenesis as a result of p53 loss in mice and p53 polymorphism in humans. The loss of murine Tp53 or expression of human R72 contributes to tumorigenesis via enhancing epithelial-to-mesenchymal transition and motility of tumor cells through the Notch and Nodal pathways. IMPLICATIONS: This work revealed unexpected contributions of the p53 polymorphism to the pathogenesis of TSC and established signaling alterations caused by this polymorphism as a target for therapy. We found that the codon 72 TP53 polymorphism contributes to TSC-associated tumorigenesis via Notch and Nodal signaling.

A novel mouse model of hemangiopericytoma due to loss of Tsc2

Hemangiopericytoma (HPC) is a rare vascular tumor, which is thought to originate from pericytes. However, no direct evidence for the cell of origin has been found, and the mechanism of HPC tumorigenesis is poorly understood. Here we report that loss of the tumor suppressor gene Tsc2 in pericytes using a FoxD1 promoter driven cre allele (Foxd1tm1(GFP/cre) Amc, FoxD1GC) leads to the formation of HPC in multiple sites. Tsc2ffFoxD1GC mice had stunted growth with seizures and tail and hind limb tremor with a median survival of 110 days. They also showed recombination in brain, spinal cord, tongue, liver, intestine and skeletal muscle. Distinctive perivascular tumors consisting of cells with oval nuclei and scant cytoplasm were identified in multiple sites in all Tsc2ffFoxD1GC mice. Immunohistochemistry staining showed a high expression of phospho-S6-S240/244, a hallmark of activated mTORC1, as well as pericyte markers NG2 and vimentin in these tumors. In summary, we demonstrate that loss of Tsc2 in pericytes generates HPC, the first mouse model of HPC reported.

Genetic Etiologies, Diagnosis, and Treatment of Tuberous Sclerosis Complex

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder that affects multiple organ systems due to an inactivating variant in either TSC1 or TSC2, resulting in the hyperactivation of the mechanistic target of rapamycin (mTOR) pathway. Dysregulated mTOR signaling results in increased cell growth and proliferation. Clinically, TSC patients exhibit great phenotypic variability, but the neurologic and neuropsychiatric manifestations of the disease have the greatest morbidity and mortality. TSC-associated epilepsy occurs in nearly all patients and is often difficult to treat because it is refractory to multiple antiseizure medications. The advent of mTOR inhibitors offers great promise in the treatment of TSC-associated epilepsy and other neurodevelopmental manifestations of the disease; however, the optimal timing of therapeutic intervention is not yet fully understood.

Neoadjuvant atezolizumab in resectable NSCLC patients: Updated clinical and immunophenotyping results from a multicenter trial

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Background: Targeting PD-L1/PD-1 to activate anti-tumor immunity is associated with improved response and survival compared to chemo in NSCLC pts. We present a preliminary analysis of the clinical efficacy, safety and peripheral blood (PB) immunophenotyping from an ongoing multicenter atezolizumab (atezo) neoadjuvant immunotherapy study in resectable NSCLC. Methods: Pts received 2 cycles of atezo, 1200mg, days 1, 22 before resection. Tumor biopsies and PB were obtained pre-atezo & pre-surgery. The biomarker evaluable population (BEP) included pts with paired PB analyzed within 72 hrs by 10-color flow cytometry (IMMUNOME) and major pathological response (MPR) assessment (defined as ≤ 10% residual tumor). The primary endpoint was MPR. Secondary endpoints included safety, MPR by PD-L1, OS, and DFS. Immunophenotypic analyses were correlated with treatment, MPR and PD-L1 expression. Results: 116 patients have been enrolled as of October 31, 2018 and here we report on 54 of 180 planned pts with follow-up through surgery. 15 pts had Gr 3-4 AEs (3 treatment related), one Gr 5 AE (sudden death) was unrelated. By RECIST there were 3 PR, 49 SD, and 2 PD. 50/54 pts underwent the planned surgery, 47 pts had MPR assessment: 4 pts discontinued study preop (2 radiographic PD, 2 other reasons); 3 were unresectable. Excluding 5 pts with EGFR or ALK mutations, MPR rate was 10/45 (22%, 95% CI 11-37%). Baseline PD-L1 status was evaluable in 44/54 pts; BEP included 31 pts, 23 had tissue PD-L1 status: 16 PD-L1+. We observed significant increases in natural killer (NK) cells, CD8+ T-cells, Th1-response related dendritic cells (DC), and decreases in B-cells after atezo. Non-MPR pts showed significant increases in late activated NK cells, monocytic myeloid cells and Th2 and Th17-response–related DCs. PD-L1+ pts showed significant decreases of senescent T cells, monocytic myeloid cells, and increases of Th1-response–related DCs. We analyzed 22/54 tumor pairs, PD-L1+ cells increased in most pts after atezo treatment. Conclusions: Neoadjuvant atezo was well tolerated and the MPR rate is encouraging. Preliminary immunophenotyping data showed significant changes in PB with immunotherapy. Clinical trial information: NCT02927301.

Germline alterations in urothelial carcinoma (UC) patients with family history of UC

474

Background: UC is associated with germline alterations in a small minority of patients (pts). The prevalence of germline alterations in those with familial UC is unknown. We identified genomic alterations among familial UC pts to provide insights into pathogenesis and improve management. Methods: We analyzed deidentified data for UC pts with germline multigene panel testing (Invitae) who had a family history of UC, defined as a 1st-3rd degree relative with UC. Massively parallel sequencing used customized capture bait-sets to analyze exonic regions, flanking intronic sequences, and copy number variations (CNVs) for 1-126 genes. Pathogenic and likely pathogenic (P/LP) variants underwent orthogonal confirmation, per standard policy, including single nucleotide variants (SNVs)/small indels/CNVs. Patient characteristics were compared using the Fisher’s Exact and Wilcoxon-Rank Sum test. Results: 79 UC pts with a family history of UC were identified (67 bladder, 6 upper tract, 6 unknown). Six patients (8%) were excluded as the relation of the family member was unknown. 48/73 (66%) pts had first-degree relatives (fdr) with UC (4 upper tract, 39 bladder, 5 unknown) and 25 (34%) had second-degree (or higher) relatives (sdr) (2 upper tract, 22 bladder, 1 unknown). 56 germline alterations were found in 38 (52%) pts. 14 known pathogenic alterations occurred in 13 (18%) pts: SDHC (1), MITF (2), BRIP1 (1), BRCA2 (1), MSH2 (3), BRCA1 (1), CHEK2 (1), PTCH (1), MUTYH (2), BAP1 (1). 8/48 (17%) pts with fdr had pathogenic variants vs. 5/25 (20%) pts with sdr or more. There was no difference in the prevalence of pathogenic variants based on gender (p=0.37) or age (p=0.77). The limitations are modest sample size and differences in panels of genes. Conclusions: This is the first study to our knowledge to report germline alterations in UC pts with a family history of UC. Pathogenic germline alterations were seen in 18% of pts, which were enriched for DNA damage repair gene alterations, and could have important therapeutic implications. Further study of germline alterations using larger panels in pts with family history of UC may provide novel insights, since most pts did not have pathogenic alterations.

Cell-free DNA analysis in renal cell carcinoma: Comparison with tumor sequencing and correlation with response to therapy

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Background: Massively parallel sequencing (MPS) of circulating-free DNA (cfDNA) is seeing increasing use in multiple cancer types. There is little data on its use in metastatic renal cell carcinoma (mRCC) as a tool for prognostication and disease monitoring. Methods: cfDNA was extracted from 63 blood samples of 40 metastatic RCC patients (pts). Serial samples were obtained in 12 of 40 (30%) pts (median = 1, range = 1-7). cfDNA was used for targeted MPS using a custom bait-set of 27 genes commonly mutated in RCC. Variants observed in at least 3 reads, in both read directions, and at an allele frequency (AF) of ≥0.5% for single nucleotide variants (SNV), or in 2 reads and AF of ≥0.2% for small indels, were candidate variants validated by Sanger sequencing or amplicon MPS (aMPS). All mutations identified in cfDNA were also assessed in matched patient WBC DNA using aMPS and Sanger sequencing. Tumor specimens from 23 pts were also sequenced in parallel using our institutional OncoPanel assay that assesses 275-447 cancer-associated genes and results were compared with those seen in the cfDNA. Results: Thirty-one of 38 (82%) candidate variants were validated in 17 of 40 pts. Ten of those (32%) from 10 pts were also detected in WBC DNA, 3 of which were germline and 7 were at low mosaic frequency and likely reflected clonal hematopoiesis (CH). The remaining 21 variants validated in cfDNA were in TP53 (6), PBRM1 (3), SETD2 (3), VHL (2), ATM (2), NF2 (2), PTEN (1), PIK3CA (1), and MTOR (1). Two of 17 (12%) pts without tumor mutation analysis had 4 validated variants seen in cfDNA only. 10 of 23 (43%) pts with tumor mutation analysis had one or more variants seen in both tumor DNA and cfDNA. Three of the 23 had mutations seen only in cfDNA. Pts with any mutation in cfDNA (n = 14) had a significantly shorter overall survival in comparison to those without a finding (p < 0.001). Among 12 pts with serial samples, 5 had cfDNA variants identified. Response to therapy correlated with variant prevalence in all 5, including 2 with significant partial responses. Conclusions: This study suggests that paired tumor–cfDNA analysis has value in the assessment of response to therapy in RCC. Further analysis is proceeding.

Genomic and clinical determinants of recurrence in localized clear cell renal cell carcinoma (ccRCC)

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Background: Multiple clinical risk scores and gene expression models have predicted recurrence in localized ccRCC. However, few studies explored genomic alterations (GA) predicting recurrence. Methods: We assessed genomic and clinical correlates of disease-free survival (DFS) in surgically treated localized ccRCC using a targeted next generation sequencing (NGS) platform (Oncopanel/PROFILE) and publicly available NGS and clinical data from TCGA. Univariable and stepwise multivariable Cox regression models (stratified by database) were performed. Results: 478 patients (123 patients from our institution and 355 patients from TCGA) were included. 150 (31.4%) patients experienced a DFS event (recurrence or death) and 94 (19.7%) died at 3.1 years (yrs) of median follow-up. Median DFS was 6.3 (5.4-7.2) yrs and the 5-yr overall survival rate was 70.8% (64.9-76.7). On multivariable analysis, 4 clinical factors and mutations in 3 genes were significantly associated with recurrence (Table). Conclusions: Our study suggests that PTEN, BAP1 and KDM5C GA may improve on clinical factors for prediction of localized ccRCC recurrence. Further work is needed to determine if these GA could improve existing validated risk models. [Table: see text]

Genomic profiling of variant urinary tract tumor histologies

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Background: Little is known about the genomic features of rare histologic variants of urinary tract (UT) tumors. The purpose of this study is to compare the pattern of genetic alterations in UT tumors with adenocarcinoma (AD), small cell (SC), or squamous cell (SQ) histology to UT tumors with urothelial carcinoma (UC) histology. Methods: We identified patients with pure variant (AD, SC, or SQ) or UC histology evaluated at Dana Farber Cancer Institute (DFCI). Tumors with mixed histology were excluded. We employed Oncopanel, which assesses 275-447 cancer genes for somatic mutations and copy number variations (CNVs). Alterations observed at an allele frequency > 0.1% in the ExAC database were assumed to be germline variants and were excluded. Mutation frequencies, CNVs, and tumor mutation burden (TMB) were determined for AD, SC, SQ, and UC, and were compared using the Fisher’s Exact test and Kruskall Wallis Test. Nominal p values were obtained, and fdr correction was employed (q < 0.1). Results: Genetic data was available for 11 AD, 6 SC, 9 SQ, and 120 UC tumors. All patients had muscle-invasive disease. The mean age was 67.8 years and 74% of patients were male. Overall, UC had significantly higher TMB than AD (median = 9.5 vs median = 6 respectively, p = 0.03). There were no significant differences in the CNV count among the four subtypes. Statistically significant differences in genetic alterations by subtype are shown in the Table. ARID1A and KDM6A mutations were less common in the variant histologies; while DICER1, FBXW7, MAP2K4, and MYB alterations were higher in ≥1 variant histology. RB1 and TP53 mutations were enriched in SC tumors while SMAD4 alterations were enriched in AD tumors. Conclusions: Genetic features of variant histology UT tumors differ from those seen in UC, suggesting biological differences and possibly different therapies. Validation in larger datasets is warranted. [Table: see text]

MCL1 and DEDD Promote Urothelial Carcinoma Progression

Focal amplification of chromosome 1q23.3 in patients with advanced primary or relapsed urothelial carcinomas is associated with poor survival. We interrogated chromosome 1q23.3 and the nearby focal amplicon 1q21.3, as both are associated with increased lymph node disease in patients with urothelial carcinoma. Specifically, we assessed whether the oncogene MCL1 that resides in 1q21.3 and the genes that reside in the 1q23.3 amplicon were required for the proliferation or survival of urothelial carcinoma. We observed that suppressing MCL1 or the death effector domain-containing protein (DEDD) in the cells that harbor amplifications of 1q21.3 or 1q23.3, respectively, inhibited cell proliferation. We also found that overexpression of MCL1 or DEDD increased anchorage independence growth in vitro and increased experimental metastasis in vivo in the nonamplified urothelial carcinoma cell line, RT112. The expression of MCL1 confers resistance to a range of apoptosis inducers, while the expression of DEDD led to resistance to TNFα-induced apoptosis. These observations identify MCL1 and DEDD as genes that contribute to aggressive urothelial carcinoma. IMPLICATIONS: These studies identify MCL1 and DEDD as genes that contribute to aggressive urothelial carcinomas.

TSC2 regulates microRNA biogenesis via mTORC1 and GSK3β

Tuberous sclerosis complex (TSC) is an autosomal dominant disease caused by germline inactivating mutations of TSC1 or TSC2. In TSC-associated tumors of the brain, heart, skin, kidney and lung, inactivation of both alleles of TSC1 or TSC2 leads to hyperactivation of the mTORC1 pathway. The TSC/mTORC1 pathway is a key regulator of cellular processes related to growth, proliferation and autophagy. We and others have previously found that mTORC1 regulates microRNA biogenesis, but the mechanisms are not fully understood. Microprocessor, a multi-protein complex including the nuclease Drosha, processes the primary miR transcript. Using a dual-luciferase reporter, we found that inhibition of mTORC1 or downregulation of Raptor decreased Microprocessor activity, while loss of TSC2 led to a striking increase (∼5-fold) in Microprocessor activity. To determine the global impact of TSC2 on microRNAs we quantitatively analyzed 752 microRNAs in Tsc2-expressing and Tsc2-deficient cells. Out of 259 microRNAs expressed in both cell lines, 137 were significantly upregulated and 24 were significantly downregulated in Tsc2-deficient cells, consistent with the increased Microprocessor activity. Microprocessor activity is known to be regulated in part by GSK3β. We found that total GSK3β levels were higher in Tsc2-deficient cells, and the increase in Microprocessor activity associated with Tsc2 loss was reversed by three different GSK3β inhibitors. Furthermore, mTOR inhibition increased the levels of phospho-GSK3β (S9), which negatively affects Microprocessor activity. Taken together these data reveal that TSC2 regulates microRNA biogenesis and Microprocessor activity via GSK3β.

Mutational Analysis of 472 Urothelial Carcinoma Across Grades and Anatomic Sites

PURPOSE

The purpose of this study is to characterize the mutational landscape across the spectrum of urothelial carcinoma (UC) to identify mutational features and potential therapeutic targets.

EXPERIMENTAL DESIGN

Using targeted exome sequencing (n = 237 genes), we analyzed the mutation spectra of 82 low-grade nonmuscle-invasive bladder cancers (LG-NMIBC), 126 high-grade (HG) NMIBC, 199 muscle-invasive bladder cancers (MIBC), 10 LG-upper tract urothelial cancers (LG-UTUC), and 55 HG-UTUC.

RESULTS

FGFR3 and KDM6A mutations were significantly more common in LG-NMIBC (72% and 44%, respectively) versus other bladder subtypes. FGFR3 alterations were also enriched in LG-UTUC versus HG-UTUC tumors (80% vs. 16%). In contrast, TP53 and RB1 mutations were significantly more frequent in all 3 HG urothelial carcinoma subtypes than in LG-NIMBC (45%-58% vs. 4%; 9%-22% vs. 0; respectively). Among LG-NMIBC tumors, KDM6A mutations were more common in women than in men (71% vs. 38%). HG-NMIBC and MIBC had higher tumor mutational burden (TMB) than LG-NMIBC (P = 0.001 and P < 0.01, respectively). DNA-damage repair (DDR) alterations were associated with a higher TMB in HG-NMIBC and MIBC tumors, and these two tumor types were also enriched for an APOBEC mutational signature compared with LG-NMIBC and HG-UTUC. Alterations in FGFR3, PIK3CA, and EP300 correlated with worse overall survival in HG-UTUC and occurred concurrently.

CONCLUSIONS

Our analysis suggests that a fraction of MIBCs likely arise from precursor lesions other than LG-NMIBC. KDM6A mutations are twice as common in women with LG-NIMBC than those in men. DDR gene mutations and APOBEC mutagenesis drive mutations in HG-NMIBC and MIBC. UTUC has a distinct mutation profile from bladder cancer.

Integrative Molecular Characterization of Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is a highly lethal cancer of the lining of the chest cavity. To expand our understanding of MPM, we conducted a comprehensive integrated genomic study, including the most detailed analysis of BAP1 alterations to date. We identified histology-independent molecular prognostic subsets, and defined a novel genomic subtype with TP53 and SETDB1 mutations and extensive loss of heterozygosity. We also report strong expression of the immune-checkpoint gene VISTA in epithelioid MPM, strikingly higher than in other solid cancers, with implications for the immune response to MPM and for its immunotherapy. Our findings highlight new avenues for further investigation of MPM biology and novel therapeutic options. SIGNIFICANCE: Through a comprehensive integrated genomic study of 74 MPMs, we provide a deeper understanding of histology-independent determinants of aggressive behavior, define a novel genomic subtype with TP53 and SETDB1 mutations and extensive loss of heterozygosity, and discovered strong expression of the immune-checkpoint gene VISTA in epithelioid MPM.See related commentary by Aggarwal and Albelda, p. 1508.This article is highlighted in the In This Issue feature, p. 1494.

Mechanisms of acquired resistance to rapalogs in metastatic renal cell carcinoma

The mechanistic target of rapamycin (mTOR) is an established therapeutic target in renal cell carcinoma (RCC). Mechanisms of secondary resistance to rapalog therapy in RCC have not been studied previously. We identified six patients with metastatic RCC who initially responded to mTOR inhibitor therapy and then progressed, and had pre-treatment and post-treatment tumor samples available for analysis. We performed deep whole exome sequencing on the paired tumor samples and a blood sample. Sequence data was analyzed using Mutect, CapSeg, Absolute, and Phylogic to identify mutations, copy number changes, and their changes over time. We also performed in vitro functional assays on PBRM1 in RCC cell lines. Five patients had clear cell and one had chromophobe RCC. 434 somatic mutations in 416 genes were identified in the 12 tumor samples. 201 (46%) of mutations were clonal in both samples while 129 (30%) were acquired in the post-treatment samples. Tumor heterogeneity or sampling issues are likely to account for some mutations that were acquired in the post-treatment samples. Three samples had mutations in TSC1; one in PTEN; and none in MTOR. PBRM1 was the only gene in which mutations were acquired in more than one post-treatment sample. We examined the effect of PBRM1 loss in multiple RCC cell lines, and could not identify any effect on rapalog sensitivity in in vitro culture assays. We conclude that mTOR pathway gene mutations did not contribute to rapalog resistance development in these six patients with advanced RCC. Furthermore, mechanisms of resistance to rapalogs in RCC remain unclear and our results suggest that PBRM1 loss may contribute to sensitivity through complex transcriptional effects.

Mammalian target of rapamycin (mTOR) inhibitors, everolimus and temsirolimus, are FDA-approved for treatment of metastatic renal cell carcinoma (mRCC), but molecular mechanisms of acquired or secondary resistance to these agents are unknown. We evaluated six mRCC patients with available pre-treatment specimens who were treated with mTOR inhibitors and had a good clinical outcome, and then had a second biopsy at the time of resistance. We found that mutations in PBRM1 appeared to be enriched in post-treatment samples. However, modulation of PBRM1 levels in vitro in cell lines had no apparent effect on rapalog sensitivity. We conclude that mechanisms of resistance to rapalog therapy in RCC are not easily explained by gene mutations in most cases, and may depend on more subtle transcriptional and/or epigenetic changes.

RAS-MAPK Reactivation Facilitates Acquired Resistance in FGFR1-Amplified Lung Cancer and Underlies a Rationale for Upfront FGFR-MEK Blockade

The FGFR kinases are promising therapeutic targets in multiple cancer types, including lung and head and neck squamous cell carcinoma, cholangiocarcinoma, and bladder cancer. Although several FGFR kinase inhibitors have entered clinical trials, single-agent clinical efficacy has been modest and resistance invariably occurs. We therefore conducted a genome-wide functional screen to characterize mechanisms of resistance to FGFR inhibition in a FGFR1-dependent lung cancer cellular model. Our screen identified known resistance drivers, such as MET, and additional novel resistance mediators including members of the neurotrophin receptor pathway (NTRK), the TAM family of tyrosine kinases (TYRO3, MERTK, AXL), and MAPK pathway, which were further validated in additional FGFR-dependent models. In an orthogonal approach, we generated a large panel of resistant clones by chronic exposure to FGFR inhibitors in FGFR1- and FGFR3-dependent cellular models and characterized gene expression profiles employing the L1000 platform. Notably, resistant clones had enrichment for NTRK and MAPK signaling pathways. Novel mediators of resistance to FGFR inhibition were found to compensate for FGFR loss in part through reactivation of MAPK pathway. Intriguingly, coinhibition of FGFR and specific receptor tyrosine kinases identified in our screen was not sufficient to suppress ERK activity or to prevent resistance to FGFR inhibition, suggesting a redundant reactivation of RAS-MAPK pathway. Dual blockade of FGFR and MEK, however, proved to be a more powerful approach in preventing resistance across diverse FGFR dependencies and may represent a therapeutic opportunity to achieve durable responses to FGFR inhibition in FGFR-dependent cancers. Mol Cancer Ther; 17(7); 1526-39. ©2018 AACR.