Pediatric lymphoid leukemia has the highest cure rate of all pediatric malignancies, yet due to its prevalence, still accounts for the majority of childhood cancer deaths and requires long-term ...highly toxic therapy. The ability to target B-cell ALL with immunoglobulin-like binders, whether anti-CD22 antibody or anti-CD19 CAR-Ts, has impacted treatment options for some patients. The development of new ways to target B-cell antigens continues at rapid pace. T-cell ALL accounts for up to 20% of childhood leukemia but has yet to see a set of high-value immunotherapeutic targets identified. To find new targets for T-ALL immunotherapy, we employed a bioinformatic comparison to broad normal tissue arrays, hematopoietic stem cells (HSC), and mature lymphocytes, then filtered the results for transcripts encoding plasma membrane proteins. T-ALL bears a core T-cell signature and transcripts encoding TCR/CD3 components and canonical markers of T-cell development predominate, especially when comparison was made to normal tissue or HSC. However, when comparison to mature lymphocytes was also undertaken, we identified two antigens that may drive, or be associated with leukemogenesis; TALLA-1 and hedgehog interacting protein. In addition, TCR subfamilies, CD1, activation and adhesion markers, membrane-organizing molecules, and receptors linked to metabolism and inflammation were also identified. Of these, only CD52, CD37, and CD98 are currently being targeted clinically. This work provides a set of targets to be considered for future development of immunotherapies for T-ALL.
Abstract
Despite improvement of survival rate with multimodal chemo- and immunotherapy, high mortality and morbidity is still substantial for patients with metastatic pediatric cancers. Recent ...studies of massively paralleled sequencing of pediatric tumors including rhabdomyosarcoma (RMS) and neuroblastoma (NB) have been focusing on somatic mutations, and revealed a low somatic mutation rate and surprisingly few recurrently somatic mutated genes in these childhood tumors. Therefore, only a small portion of pediatric cancer cases can be explained by somatic driver events; whereas the causal events for the majority of these diseases remain unknown. Here, we hypothesize that infrequent germline mutations may play a role in the initiation of sporadically occurring tumor.
To identify rare expressed germline protein-coding changing mutations, we utilized two cancer patient cohorts consisting of RMS (n=83) and NB (n=93) patients, of which latter is a part of the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) initiative for pediatric cancers. We first called high-quality protein-coding changing single nucleotide variants (SNVs) (≥100, Coverage ≥10, ≥3 variant reads, ≥30% variant allele frequency) in both paired germline and tumor genomic DNAs. Since both these two types of tumors are uncommon, we then excluded variants with frequencies of >0.1% in the normal human population using the 1000 Genomes data, but retained all disease-causing SNVs annotated either by the Human Gene Mutation Database (HGMD) or ClinVar. Previous studies have highlighted the importance of expression of variant genes (including tumor suppressor genes) for identification of driver mutations in cancers. Therefore we utilized transcriptome sequencing experiments to identify expressed variants in tumor. In addition, we performed Fisher's exact tests comparing germline mutations in these two patient cohorts with the ESP dataset comprising 6503 non-cancer subjects to identify significant overrepresentation of germline mutations in these cancers. Finally we performed pathway analyses using the significant genes.
We initially identified a total of 783169 high-quality protein-coding changing SNVs detected in both paired germline and tumor genomic DNAs, corresponding to a median of 4818 (2093-7569) SNVs per patient. After exclusion of common variants of ≥0.1% frequency in the 1000 Genomes and inclusion of all disease-causing SNVs, there are total of 91924 SNVs, representing a median of 535 (155-877) SNVs per patient corresponding to a median of 468 (153-752) genes. Approximately 59% (total 54664, Median of 319 (94-549) SNVs) of these germline variants can be detected in the transcriptome in their corresponding tumors, suggesting potential functions in these tumors. Statistical analysis is currently underway to determine potential pathological or casual germline mutations associated with neuroblastoma and rhabdomyosarcoma.
Citation Format: Jun S. Wei, Rajesh Patidar, John Shern, Shile Zhang, Trevor Pugh, Sharon J. Diskin, Sivasish Sindiri, Young K. Song, Hongling Liao, Xinyu Wen, Jianjun Wang, Stephen X. Skapek, James R. Anderson, Frederic G. Barr, Robert C. Seeger, John M. Maris, Douglas Hawkins, Javed Khan. Systematic identification of germline mutations in rhabdomyosarcoma and neuroblastoma using massively paralleled sequencing. abstract. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr A12.
Abstract
Despite improvement of survival using multimodal chemo- and immunotherapy, high mortality and morbidity is still substantial for pediatric patients with metastatic cancers. Recent ...large-scale sequencing studies of pediatric tumors including rhabdomyosarcoma (RMS) and neuroblastoma (NB) have been focusing on somatic mutations, and revealed a low somatic mutation rate and surprisingly few recurrently somatic mutated genes in these childhood tumors. Currently, only a small portion of pediatric cancer cases can be explained by somatic driver events; whereas the cause for the majority of these diseases remains unknown. Because both these two types of tumors are uncommon, here we hypothesize that infrequent germline mutations (frequency<0.05 in control populations) may play a role in the initiation of sporadically occurring tumor.
To test this hypothesis, we utilized sequencing data from two cancer patient cohorts consisting of RMS (n=133) and NB (n=222) patients, of which latter is a part of the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) initiative for pediatric cancers. First, high-quality protein-coding changing single nucleotide variants (SNVs) were called in both paired germline and tumor genomic DNAs. Then we excluded common variants with frequency >5% in a normal human population using the 1000 Genomes data. Due to our interest in the enriched variants, we further required the frequencies of variants in our rhabdomyosarcoma and neuroblastoma patient cohorts are higher than those in the ESP dataset, a non-cancer control population comprising 6503 individuals. There are 63247 SNVs fulfilled these selection criteria. Among them, 1589 have been reported in these pediatric cancers or in other malignancies in the Cancer Genome Atlas (TCGA) project; and 1178 variants are present in the Human Gene Mutation Database (HGMD). Of these HGMD variants, 49 have been reported in human diseases and 34 of them are known disease-causing mutations for human cancers and genetic disorders including TP53, ALK, CHEK2, and PINK1. Interestingly, the most frequent germline mutations in these pediatric tumors were rarely found in the TCGA project which mostly consists of adult cancers. This observation suggests a very different genetic background of pediatric cancer patients from that of the adult cancers, and warrants a careful examination of germline mutations in these cancers. Furthermore, previous studies have highlighted the importance of expression of variant genes (including tumor suppressor genes) for identification of driver mutations in cancers. Therefore we will use 178 transcriptome sequencing experiments available for these tumors (RMS=84; NB=93) to identify expressed variants in tumor. Statistical and pathway analyses are currently underway to determine potential pathological or casual germline mutations associated with neuroblastoma and rhabdomyosarcoma.
Citation Format: Jun S. Wei, Rajesh Patidar, John Shern, Shile Zhang, Trevor Pugh, Sharon J. Diskin, Sivasish Sindiri, Young K. Song, Hongling Liao, Xinyu Wen, Jianjun Wang, Stephen X. Skapek, James R. Anderson, Frederic G. Barr, Robert C. Seeger, John M. Maris, Douglas S. Hawkins, Javed Khan. Systematic identification of germline mutations in rhabdomyosarcoma and neuroblastoma using massively paralleled sequencing. abstract. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5081. doi:10.1158/1538-7445.AM2014-5081
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.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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