Noha Gerges

Recurrent somatic mutations in ACVR1 in pediatric midline high-grade astrocytoma

Pediatric midline high-grade astrocytomas (mHGAs) are incurable with few treatment targets identified. Most tumors harbor mutations encoding p.Lys27Met in histone H3 variants. In 40 treatment-naive mHGAs, 39 analyzed by whole-exome sequencing, we find additional somatic mutations specific to tumor location. Gain-of-function mutations in ACVR1 occur in tumors of the pons in conjunction with histone H3.1 p.Lys27Met substitution, whereas FGFR1 mutations or fusions occur in thalamic tumors associated with histone H3.3 p.Lys27Met substitution. Hyperactivation of the bone morphogenetic protein (BMP)-ACVR1 developmental pathway in mHGAs harboring ACVR1 mutations led to increased levels of phosphorylated SMAD1, SMAD5 and SMAD8 and upregulation of BMP downstream early-response genes in tumor cells. Global DNA methylation profiles were significantly associated with the p.Lys27Met alteration, regardless of the mutant histone H3 variant and irrespective of tumor location, supporting the role of this substitution in driving the epigenetic phenotype. This work considerably expands the number of potential treatment targets and further justifies pretreatment biopsy in pediatric mHGA as a means to orient therapeutic efforts in this disease.

New technologies for the detection of circulating tumour cells

The vast majority of cancer-related death is due to the metastatic spread of the primary tumour. Circulating tumour cells (CTC) are essential for establishing metastasis and their detection has long been considered as a possible tool to assess the aggressiveness of a given tumour and its potential of subsequent growth at distant organs. Conventional markers are not reliable in detecting occult metastasis and, for example, fail to identify approximately 40% of cancer patients in need of more aggressive or better adjusted therapies. Recent studies in metastatic breast cancer have shown that CTC detection can be used as a marker for overall survival and assessment of the therapeutic response. The benefits of CTC detection in early breast cancer and other solid tumours need further validation. Moreover, optimal CTC detection techniques are the subject of controversy as several lack reproducibility, sensitivity and/or specificity. Recent technical advances allow CTC detection and characterization at the single-cell level in the blood or in the bone marrow. Their reproducibility propels the use of CTC in cancer staging and real-time monitoring of systemic anticancer therapies in several large clinical trials. CTC assays are being integrated in large clinical trials to establish their potential in the management of cancer patients and improve our understanding of metastasis biology. This review will focus on the techniques currently used, the technical advancements made, the limitations of CTC detection and future perspectives in this field.

Fusion of TTYH1 with the C19MC microRNA cluster drives expression of a brain-specific DNMT3B isoform in the embryonal brain tumor ETMR

Embryonal tumors with multilayered rosettes (ETMRs) are rare, deadly pediatric brain tumors characterized by high-level amplification of the microRNA cluster C19MC. We performed integrated genetic and epigenetic analyses of 12 ETMR samples and identified, in all cases, C19MC fusions to TTYH1 driving expression of the microRNAs. ETMR tumors, cell lines and xenografts showed a specific DNA methylation pattern distinct from those of other tumors and normal tissues. We detected extreme overexpression of a previously uncharacterized isoform of DNMT3B originating at an alternative promoter that is active only in the first weeks of neural tube development. Transcriptional and immunohistochemical analyses suggest that C19MC-dependent DNMT3B deregulation is mediated by RBL2, a known repressor of DNMT3B. Transfection with individual C19MC microRNAs resulted in DNMT3B upregulation and RBL2 downregulation in cultured cells. Our data suggest a potential oncogenic re-engagement of an early developmental program in ETMR via epigenetic alteration mediated by an embryonic, brain-specific DNMT3B isoform.

Preponderance of sonic hedgehog pathway activation characterizes adult medulloblastoma

Medulloblastoma (MB) represents approximately 4% of adult brain tumours, and as such is a poorly studied disease. Although many adult MB are treated using paediatric MB protocols, the reported outcomes are inferior to those observed in children. It remains unclear whether biologic differences underlie these clinical observations. We investigated the molecular characteristics of 31 adult MB. Twelve and 19 adult MB were respectively examined using Affymetrix-HG-U133-plus-2.0-genechips and immunohistochemical analyses. 26/31 (84%) of adult MB examined by gene expression and/or immunohistochemical analysis showed evidence of sonic hedgehog (SHH) pathway activation. A comparison of adult and paediatric MB showed that most adult tumours cluster within the SHH-active subgroup of paediatric MB. The preponderance of SHH activity in adult MB tumours was also shown by positive SFRP1 immunostaining in 16/19 adult paraffin-embedded adult MB tumour blocks. A smaller proportion of adult tumours exhibited evidence of WNT pathway activation, as confirmed by nuclear β-catenin staining (9.7%; 3/31). Notably, we found PTCH1 gene mutation in 4/8 samples tested. Similar to children, adult MB has abnormalities in developmental signalling pathways including SHH and WNT. Importantly, we found a preponderance of SHH pathway activation amongst MB tumours in adults. This SHH signature does not appear to correlate with a long-term favourable outcome. Differences in molecular profiles exist between adult and paediatric SHH-driven MB and further investigations are needed to better characterize age-related molecular profiles in this subgroup.

Coagulation-related gene expression profile in glioblastoma is defined by molecular disease subtype.

1 Bonello L, Tantry US, Marcucci R, Blindt R, Angiolillo DJ, Becker R, Bhatt DL, Cattaneo M, Collet JP, Cuisset T, Gachet C, Montalescot G, Jennings LK, Kereiakes D, Sibbing D, Trenk D, van Werkum JW, Paganelli F, Price MJ, Waksman R, et al.; Working Group on High On-Treatment Platelet Reactivity. Consensus and future directions on the definition of high on-treatment platelet reactivity to adenosine diphosphate. J Am Coll Cardiol 2010; 56: 919–33. 2 Beitelshees AL, Horenstein RB, Vesely MR, Mehra MR, Shuldiner AR. Pharmacogenetics and clopidogrel response in patients undergoing percutaneous coronary interventions. Clin Pharmacol Ther 2011; 89: 455–9. 3 Yin OQ, Tomlinson B, Chow AH, Waye MM, Chow MS. Omeprazole as a CYP2C19 marker in Chinese subjects: assessment of its gene-dose effect and intrasubject variability. J Clin Pharmacol 2004; 44: 582–9. 4 Ieiri I, Kubota T, Urae A, Kimura M, Wada Y, Mamiya K, Yoshioka S, Irie S, Amamoto T, Nakamura K, Nakano S, Higuchi S. Pharmacokinetics of omeprazole (a substrate of CYP2C19) and comparison with two mutant alleles, CYP2C19 m1 in exon 5 and CYP2C19 m2 in exon 4, in Japanese subjects. Clin Pharmacol Ther 1996; 59: 647–53. 5 Gremmel T, Panzer S. Clinical, genetic and confounding factors determine the dynamics of the in vitro response/non response to clopidogrel. Thromb Haemost 2011; 106: 211–8. 6 Ramsj€ o M, Aklillu E, Bohman L, Ingelman-Sundberg M, Roh HK, Bertilsson L. CYP2C19 activity comparison between Swedes and Koreans: effect of genotype, sex, oral contraceptive use, and smoking. Eur J Clin Pharmacol 2010; 66: 871–7. 7 Bouman HJ, Harmsze AM, van Werkum JW, Breet NJ, Bergmeijer TO, Ten Cate H, Hackeng CM, Deneer VH, Ten Berg JM. Variability in on-treatment platelet reactivity explained by CYP2C19*2 genotype is modest in clopidogrel pretreated patients undergoing coronary stenting.Heart 2011; 97: 1239–44. 8 Feng HJ, Huang SL, Wang W, Zhou HH. The induction effect of rifampicin on activity of mephenytoin 4′-hydroxylase related to M1 mutation of CYP2C19 and gene dose. Br J Clin Pharmacol 1998; 45: 27–9. 9 Price MJ, Murray SS, Angiolillo DJ, Lillie E, Smith EN, Tisch RL, Schork NJ, Teirstein PS, Topol EJ; GIFT Investigators. Influence of Genetic Polymorphisms on the Effect of Highand Standard-Dose Clopidogrel After Percutaneous Coronary Intervention: The GIFT (Genotype Information and Functional Testing) Study. J Am Coll Cardiol 2012; 59: 1928–37.

Biomarkers in cancer micrometastasis: where are we at?

Despite considerable advances in the field of solid tumors, disseminated malignancy remains the cause of the vast majority of cancer-related deaths. In patients with no overt metastasis, early spread of tumor cells is usually undetected by current imaging technologies. In addition, the metastatic process is complex and depends on multiple interactions (crosstalk) of disseminating tumor cells with the individual homeostatic mechanisms, which the tumor cells can usurp. Despite these many variables, a flurry of surrogate biomarkers to detect micrometastasis has been developed in the last decade. These biomarkers open avenues for understanding cancer dormancy and metastasis, have the potential to provide novel therapeutic targets and may help predict outcome and therapeutic decisions at diagnosis and during follow-up of cancer patients. This review focuses on ongoing efforts to unravel metastasis biology, surrogate biomarkers currently investigated to monitor micrometastasis and tools used to identify, quantify and determine their capacity to efficiently establish metastasis.

Pediatric high-grade astrocytomas: a distinct neuro-oncological paradigm

Brain tumors are the leading cause of cancer-related death in children. High-grade astrocytomas (HGAs), in particular, are lethal in children across all ages. Integrative genome-wide analyses of the tumors genome, transcriptome and epigenome, using next-generation sequencing technologies and genome-wide DNA methylation arrays, have provided valuable breakthroughs in our understanding of the pathogenesis of HGAs across all ages. Recent profiling studies have provided insight into the epigenetic nature of gliomas in young adults and HGAs in children, particularly with the identification of recurrent gain-of-function driver mutations in the isocitrate dehydrogenase 1 and 2 genes (IDH1/2) and the epigenetic influence of their oncometabolite 2-hydroxyglutarate, as well as mutations in the histone 3 variant 3 gene (H3F3A) and loss-of-function mutations in the histone 3 lysine 36 trimethyltransferase gene (SETD2). Mutations in H3F3A result in amino acid substitutions at residues thought to directly (K27M) or indirectly (G34R/V) affect histone post-translational modifications, suggesting they have the capacity to affect the epigenome in a profound manner. Here, we review recent genomic studies, and discuss evidence supporting the molecular characterization of pediatric HGAs to complement traditional approaches, such as histology of resected tumors. We also describe newly identified molecular mechanisms and discuss putative therapeutic approaches for HGAs specific to pediatrics, highlighting the necessity for the evolution of HGA disease management approaches.

Non-random aneuploidy specifies subgroups of pilocytic astrocytoma and correlates with older age.

Pilocytic astrocytoma (PA) is the most common brain tumor in children but is rare in adults, and hence poorly studied in this age group. We investigated 222 PA and report increased aneuploidy in older patients. Aneuploid genomes were identified in 45% of adult compared with 17% of pediatric PA. Gains were non-random, favoring chromosomes 5, 7, 6 and 11 in order of frequency, and preferentially affecting non-cerebellar PA and tumors with BRAF V600E mutations and not with KIAA1549-BRAF fusions or FGFR1 mutations. Aneuploid PA differentially expressed genes involved in CNS development, the unfolded protein response, and regulators of genomic stability and the cell cycle (MDM2, PLK2),whose correlated programs were overexpressed specifically in aneuploid PA compared to other glial tumors. Thus, convergence of pathways affecting the cell cycle and genomic stability may favor aneuploidy in PA, possibly representing an additional molecular driver in older patients with this brain tumor.