Andrew S. Brohl

Comprehensive Genomic Analysis of Rhabdomyosarcoma Reveals a Landscape of Alterations Affecting a Common Genetic Axis in Fusion-Positive and Fusion-Negative Tumors

UNLABELLED Despite gains in survival, outcomes for patients with metastatic or recurrent rhabdomyosarcoma remain dismal. In a collaboration between the National Cancer Institute, Childrens Oncology Group, and Broad Institute, we performed whole-genome, whole-exome, and transcriptome sequencing to characterize the landscape of somatic alterations in 147 tumor/normal pairs. Two genotypes are evident in rhabdomyosarcoma tumors: those characterized by the PAX3 or PAX7 fusion and those that lack these fusions but harbor mutations in key signaling pathways. The overall burden of somatic mutations in rhabdomyosarcoma is relatively low, especially in tumors that harbor a PAX3/7 gene fusion. In addition to previously reported mutations in NRAS, KRAS, HRAS, FGFR4, PIK3CA, and CTNNB1, we found novel recurrent mutations in FBXW7 and BCOR, providing potential new avenues for therapeutic intervention. Furthermore, alteration of the receptor tyrosine kinase/RAS/PIK3CA axis affects 93% of cases, providing a framework for genomics-directed therapies that might improve outcomes for patients with rhabdomyosarcoma. SIGNIFICANCE This is the most comprehensive genomic analysis of rhabdomyosarcoma to date. Despite a relatively low mutation rate, multiple genes were recurrently altered, including NRAS, KRAS, HRAS, FGFR4, PIK3CA, CTNNB1, FBXW7, and BCOR. In addition, a majority of rhabdomyosarcoma tumors alter the receptor tyrosine kinase/RAS/PIK3CA axis, providing an opportunity for genomics-guided intervention.

The genomic landscape of the Ewing Sarcoma family of tumors reveals recurrent STAG2 mutation.

The Ewing sarcoma family of tumors (EFT) is a group of highly malignant small round blue cell tumors occurring in children and young adults. We report here the largest genomic survey to date of 101 EFT (65 tumors and 36 cell lines). Using a combination of whole genome sequencing and targeted sequencing approaches, we discover that EFT has a very low mutational burden (0.15 mutations/Mb) but frequent deleterious mutations in the cohesin complex subunit STAG2 (21.5% tumors, 44.4% cell lines), homozygous deletion of CDKN2A (13.8% and 50%) and mutations of TP53 (6.2% and 71.9%). We additionally note an increased prevalence of the BRCA2 K3326X polymorphism in EFT patient samples (7.3%) compared to population data (OR 7.1, p = 0.006). Using whole transcriptome sequencing, we find that 11% of tumors pathologically diagnosed as EFT lack a typical EWSR1 fusion oncogene and that these tumors do not have a characteristic Ewing sarcoma gene expression signature. We identify samples harboring novel fusion genes including FUS-NCATc2 and CIC-FOXO4 that may represent distinct small round blue cell tumor variants. In an independent EFT tissue microarray cohort, we show that STAG2 loss as detected by immunohistochemistry may be associated with more advanced disease (p = 0.15) and a modest decrease in overall survival (p = 0.10). These results significantly advance our understanding of the genomic and molecular underpinnings of Ewing sarcoma and provide a foundation towards further efforts to improve diagnosis, prognosis, and precision therapeutics testing.

Clinicopathologic features of a second patient with Ewing-like sarcoma harboring CIC-FOXO4 gene fusion.

Sugita et al. recently reported a Ewing-like sarcoma within the right posterior neck of a 63 year old man that was found to have a novel CIC-FOXO4 gene fusion caused by translocation t(X;19)(q13;q13.3).1 The tumor was composed of sheets of undifferentiated small round blue cells within abundant desmoplastic stroma containing coarse chromatin and conspicuous nucleoli which expressed CD99, CD56, and WT1 but not SMA, desmin, CD34, or EMA. This patient is reportedly alive and disease-free at six months after gross total resection followed by adjuvant radiation and chemotherapy with adriamycin and ifosfamide.1 The prevalence, pathologic characteristics, and clinical behavior of this Ewing-like sarcoma with novel CIC-FOXO4 fusion are undefined.

Germline CARD11 Mutation in a Patient with Severe Congenital B Cell Lymphocytosis

PurposeActivating germline mutations in CARD11 have recently been linked to a rare genetic disorder associated with congenital B cell lymphocytosis. We describe a patient with a similar clinical phenotype who had a de novo germline G123D CARD11 mutation.MethodsWhole exome sequencing was performed on DNA from the patient and his biological parents. Laboratory studies examined characteristics of the patient’s B and T lymphocytes. A CARD11 cDNA containing the mutation was transfected into a lymphocyte cell line to gain an understanding of its function. RNA sequencing was performed on samples from the patient and from patients with alternate germline CARD11 mutations and differential gene expression analysis was performed.ResultsThe patient had a decade-long history of severe polyclonal B lymphocytosis in the 20,000–90,000 lymphocytes/mm3 range, which was markedly exacerbated by EBV infection and splenectomy at different times. He had a heterozygous germline CARD11 mutation causing a G123D amino acid substitution, which was demonstrated to induce NF-κB activation in unstimulated lymphocytes. In contrast to previous patients with CARD11 mutations, this patient’s B cells exhibited higher expression of several cell cycle progression genes, as well as enhanced proliferation and improved survival following B cell receptor stimulation.ConclusionsThis is the third reported germline and first de novo CARD11 mutation shown to cause congenital B cell lymphocytosis. The mutation was associated with a dramatically greater lymphocytosis than in previously described cases, disproportionate to the level of constitutive NF-κB activation. However, comparative review of the patient’s clinical history, combined with additional genomic and functional analyses, underscore other important variables that may affect pathophysiology or regulate mutant CARD11 function in B cell proliferation and disease. We now refer to these patients as having BENTA disease (B cell Expansion with NF-κB and T cell Anergy).

MultiDimensional ClinOmics for Precision Therapy of Children and Adolescent Young Adults with Relapsed and Refractory Cancer: A Report from the Center for Cancer Research

Purpose: We undertook a multidimensional clinical genomics study of children and adolescent young adults with relapsed and refractory cancers to determine the feasibility of genome-guided precision therapy. Experimental Design: Patients with non-central nervous system solid tumors underwent a combination of whole exome sequencing (WES), whole transcriptome sequencing (WTS), and high-density single-nucleotide polymorphism array analysis of the tumor, with WES of matched germline DNA. Clinically actionable alterations were identified as a reportable germline mutation, a diagnosis change, or a somatic event (including a single nucleotide variant, an indel, an amplification, a deletion, or a fusion gene), which could be targeted with drugs in existing clinical trials or with FDA-approved drugs. Results: Fifty-nine patients in 20 diagnostic categories were enrolled from 2010 to 2014. Ages ranged from 7 months to 25 years old. Seventy-three percent of the patients had prior chemotherapy, and the tumors from these patients with relapsed or refractory cancers had a higher mutational burden than that reported in the literature. Thirty patients (51% of total) had clinically actionable mutations, of which 24 (41%) had a mutation that was currently targetable in a clinical trial setting, 4 patients (7%) had a change in diagnosis, and 7 patients (12%) had a reportable germline mutation. Conclusions: We found a remarkably high number of clinically actionable mutations in 51% of the patients, and 12% with significant germline mutations. We demonstrated the clinical feasibility of next-generation sequencing in a diverse population of relapsed and refractory pediatric solid tumors. Clin Cancer Res; 22(15); 3810–20. ©2016 AACR.

Frequent inactivating germline mutations in DNA repair genes in patients with Ewing sarcoma

Purpose:Ewing sarcoma is a small round blue cell tumor that is highly malignant and predominantly affects the adolescent and young adult population. It has long been suspected that a genetic predisposition exists for this cancer, but the germ-line genetic underpinnings of this disease have not been well established.Methods:We performed germline variant analysis of whole-genome or whole-exome sequencing of samples from 175 patients affected by Ewing sarcoma.Results:We discovered pathogenic or likely pathogenic germline mutations in 13.1% of our cohort. Pathogenic mutations were highly enriched for genes involved with DNA damage repair and for genes associated with cancer predisposition syndromes.Conclusion:Our findings reported here have important clinical implications for patients and families affected by Ewing sarcoma. Genetic counseling should be considered for patients and families affected by this disease to take advantage of existing risk management strategies. Our study also highlights the importance of germline sequencing for patients enrolled in precision-medicine protocols.Genet Med advance online publication 26 January 2017

Abstract 1340: RAS pathway activation and sensitivity to therapeutic agents is correlated with NF1 residual activity in malignant peripheral nerve sheath tumors

Background: Malignant Peripheral Nerve Sheath Tumor (MPNST) is a malignant sarcoma that derives from a peripheral nerve or plexiform neurofibroma. Neurofibromatosis type 1 (NF-1) patients are particularly susceptible, with a higher risk, earlier onset, and worse prognosis. The major factor associated with MPNST and NF-1 is Neurofibromin 1, coded by the NF1 gene. NF1 mutation results in RAS hyperactivation. Chemotherapy for MPNST is currently limited, with poor prognosis for metastatic or unresectable tumors. Thus, the development of promising treatment solutions for MPNST to translate to clinical trials is required. Methods: Here, we seek to identify efficacious chemotherapeutic treatments for MPNST with a combination of drug screening and biological pathway analysis. We used our previously established preclinical system to test FDA approved or promising developmental agents against five cell line models for MPNST. We screened sixty agents with diverse mechanisms of action below published maximum plasma concentrations, and measured effects with a CellTiter-Glo viability assay. Promising agents were then tested in two-drug combinations, allowing for determination of synergism. We then examined the molecular effects of the top candidates with use of antibody arrays that permit detection of a series of phosphorylated proteins. Results: The group of most efficacious drugs was enriched with agents that target factors downstream of RAS, including MEK, mTOR, and PI3K inhibitors, with microtubule inhibitors, genotoxics, and HDAC inhibitors also demonstrating good results. Strong synergism was observed across our cell line models particularly in combinations containing the dual mTORC1/2 inhibitor INK128. Interestingly, drug sensitivity varied greatly between cell lines, correlating with relative NF1 protein and RAS-GTP levels. We analyzed the activation of the RAS pathway in response to drug treatment with antibody arrays and found that, following treatment, relative phosphorylation signal was more decreased compared to controls in cell lines with lower relative NF1 protein levels. Doxorubicin was able to reduce phosphorylation signal compared to controls to a level near comparable to targeted inhibitors, which could contribute to doxorubicin’s current usefulness against MPNSTs. Importantly, we identified combination treatments that were able to greatly reduce the relative phosphorylation signal of RAS pathway members versus control. Combinations containing INK128 resulted in the most pathway shutdown. These findings suggest that MPNSTs may be susceptible to combination treatments targeting RAS pathway members. Moreover, it may be possible to use pathway analysis as a diagnostic tool to predict drug tolerance. Citation Format: Elliot Kahen, Darcy Welch, Diana Yu, Christopher Cubitt, Jae Lee, Andrew Brohl, Damon R. Reed. RAS pathway activation and sensitivity to therapeutic agents is correlated with NF1 residual activity in malignant peripheral nerve sheath tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1340. doi:10.1158/1538-7445.AM2017-1340

Abstract 2020: Next-generation sequencing for mutation discovery in Ewing sarcoma.

Background: Ewing sarcoma (EWS) is the second most common type of primary bone tumor to affect children and adolescent and accounts for 2.9% of all childhood cancers. Despite advances in multidisciplinary treatment leading to improved outcomes over time, long term survival still remains less than 50% for patients older than 15 years of age and only 65% in younger patients. In an effort to identify novel prognostic and therapeutic targets, we utilized next generation sequencing techniques to evaluate EWS samples for somatic mutation. Methods: Whole genome paired-end sequencing using the Complete Genomics method was performed on the DNA from 6 EWS matched tumor-normal samples. Somatic mutations were identified and classified using standard bioinformatics techniques and mutations of interest were verified using capillary sequencing. To extend discoveries and evaluate for mutational recurrence, targeted sequencing was performed on a validation cohort of 61 EWS tumors and 22 EWS cell lines using a custom multiplex PCR design followed by high-coverage sequencing on the Ion Torrent system. Results: In the discovery cohort, we detected an average of 361 somatic mutations per tumor in non-repetitive regions and an average of 6 somatic mutations per tumor in protein coding regions (=0.15 mutations/Mb of coding sequence). The well-established FLI1-EWSR1 gene fusion was detected by the whole genome sequencing in all 6 samples. Additional previously reported genetic events were also seen including frequent chromosomal trisomy and deletion of the CDKN2A containing locus on chromosomal region 9p21 in 2 of 6 samples. In the validation cohort of tumors, known recurrent mutations such as in TP53 (3/61 = 4.9%) were seen at rates similar to that previously reported in EWS. Continued efforts are underway to verify novel recurrent mutations. Conclusion: Next-generation sequencing provides a powerful tool to characterize the genetic landscape and evaluate for recurrent mutations in cancer. We utilize this tool in Ewing sarcoma in a project that provides both a comprehensive genomic evaluation from whole genome sequencing data and as well evaluates for recurrent mutations using a targeted sequencing approach. Citation Format: Andrew S. Brohl, Young Song, Laura Hurd, Hongling Liao, Li Chen, Rajesh Patidar, John F. Shern, Jun S. Wei, Javed Khan. Next-generation sequencing for mutation discovery in Ewing sarcoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2020. doi:10.1158/1538-7445.AM2013-2020

Synchronous indolent primary gastrointestinal lymphomas managed successfully with conservative measures.

We report the case of a 65-year-old man who presented with epigastric pain and guaic-positive stool. Upper and lower endoscopy revealed abnormalities in the gastric antrum and terminal ileum. Biopsy of these sites revealed histologically and immunophenotypically distinct lymphomas: gastric extranodal marginal zone lymphoma in the background of Helicobacter pylori infection and follicular lymphoma of the terminal ileum. After treatment with an H. pylori eradication regimen, repeat endoscopy showed resolution of the gastric extranodal marginal zone lymphoma and persistence of the ileal follicular lymphoma. Interestingly, molecular studies performed on the biopsy specimens revealed a common IgH rearrangement, suggesting a common precursor cell responsible for these two malignant processes. We present this unique case with a review of the literature, highlighting treatment principles for these two subtypes of indolent gastrointestinal non-Hodgkin lymphoma.