Project description:Pediatric acute lymphoblastic leukemia (ALL) contains cytogenetically distinct subtypes that respond differently to cytotoxic drugs. Subtype classification can be also achieved through gene expression profiling. However, how to apply such classifiers to a single patient and correctly diagnose the disease subtype in an independent patient group has not been addressed. Furthermore, the underlying regulatory mechanisms responsible for the subtype-specific gene expression patterns are still largely unknown. Here, by combining three published microarray datasets (PMIDs: 12086872, 12730115, 17002788) on 535 Caucasian samples and generating a new dataset on 100 Chinese children ALL samples, we were able to 1) identify a 62-gene classifier with 97.6% accuracy from the Caucasian samples and validated it on the completely independent set of 100 Chinese samples, 2) to uncover potential regulatory networks of ALL subtypes. The classifier we identified was so far the only one that could be applied directly to a single sample and sustained validation in a large independent patient group. Our results also suggest that the etiology of ALL is largely the same among different ethnic groups, and that the transcription factor hubs in the predicted regulatory network might play important roles in regulating gene expression and development of ALL. A total of 100 Chinese pediatric acute lymphoblastic leukemia bone marrow (BM) samples were analyzed, together with five non-ALL BM samples as negative control (the five samples were combined to generate one control, see details in Li et al. Blood, 2009). The diagnosis of ALL was based on morphology, immunology, cytogenetic and molecular (MICM) classification. Cytogenetic ALL subtypes were identified experimentally by G-banding karyotype and multiplex nested RT-PCR. Among the 100 ALL patients, eleven relapsed within five years. All the samples, including those relapsed afterward, were from patients treated on BCH-2003 protocol and were extracted at their initial diagnosis. The five non-ALL BM samples were taken from the removed bones of patients who had plastic surgery for their bone deformity in Beijing Children’s Hospital. And the informed consent was obtained from parents, guardians, or patients (as appropriate). More details are available in Li et al. Gene expression-based classification and regulatory networks of pediatric acute lymphoblastic leukemia, Blood, 2009. We have generated these ALL and control samples to validate that a high accuracy subtype classifier that we identified could be applied directly to a single sample and sustained validation in a large independent patient group.

Project description:Breast cancer is a heterogeneous disease described in well-recognized biological subtypes. Particularly, gene expression profiling has revealed 5 intrinsic subtypes of breast cancer characterized by different biological and clinical features. The diversity of the intrinsic subtypes across human population has been limited described, and there is few information about the genomic architecture of breast tumors in Mexican or Hispanic populations. In this study, we performed PAM50 assay, based in Affymetrix microarray profiling of 128 fresh frozen tumors from Mexican Latino Hispanic population, to describe the overall distribution of subtypes, and characterize the relation to clinicopathologic characteristics. As well, we correlated the mRNA expression patterns with specific copy number alterations (CPA), in order to analyze their role in breast tumors. A total of 100 blood-tumor samples were assayed using Affymetrix 6.0 SNP arrays; segmentation analysis and GISTIC were performed to identify focal amplifications or deletions. The distribution of PAM50 intrinsic subtypes in our cohort was computed to be 44% luminal A, 20% luminal B, 12.0% HER2-enriched, 12% basal-like, and 12% normal-like. Study comparison with the literature mainly TCGA and METABRIC (most of the patients came from Caucasian population), as well as LACE (which describe a population study) show a similar distribution of the intrinsic subtypes within Hispanic and Caucasian populations. Interestingly, basal-like subtype is less represented than in African-American race. The sum of sensitivity and specificity between the clinicopathologic and intrinsic subtype categories across 4 groups (excluding normal-like) was 50% and 87.5%, respectively. Differentially expression profiles within the subtypes reveal a set of genes altered in each group with biological relevance to stablish the phenotypical characteristics of each subtype. Our analyses confirmed the already reported copy number data. Importantly, many of the copy number profiles correlated with mRNA subtype. With this analysis we can conclude that breast cancer intrinsic subtypes have been reproduced in Mexican population contributing to the description of the PAM50 subtypes among multiple ethnic groups based on a gene expression assay. Our observation based in the integrative genomic analysis of mRNA expression and CPA allowed us to define gene circuits and phenotypic characteristics that can explain the heterogeneity of breast cancer subtypes.

Dataset Information

Bone marrow gene expression of pediatric acute lymphoblastic leukemia (ALL)

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