Dataset Information

Expression Profiles of Breast Tumors from Singapore and Europe

ABSTRACT: To facilitate a better understanding of the molecular heterogeneity of breast cancer and to uncover gene-survival associations that segregate with distinct molecular subtypes, we recently compiled a meta-analytical database of over 2,000 human breast tumor expression profiles variously annotated for clinical and pathological variables and derived from various institutions worldwide. This database was utilized for the breast tumor study cited below: Nagalla, et. al., Genome Biology, 2013. While the majority of the tumor expression profiles included in this database derived from publicly accessible microarray repositories, a number of the samples had not been previously published. Here, we describe the origin of these samples and provide their associated clinical and pathological annotations with the hope that other investigators will be able to utilize these data in their own research.

ORGANISM(S): Homo sapiens

PROVIDER: GSE45255 | GEO | 2013/03/21

SECONDARY ACCESSION(S): PRJNA193335

REPOSITORIES: GEO

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Project description:Histological grading of breast cancer defines morphological subtypes informative of metastatic potential, although not without considerable inter-observer disagreement and clinical heterogeneity particularly among the moderately differentiated grade II (G2) tumors. We posited that a gene expression signature capable of discerning tumors of grade I (G1) and grade III (G3) histology might provide a more objective measure of grade with prognostic benefit for patients with moderately differentiated disease. To this end, we studied the expression profiles of 347 primary invasive breast tumors analyzed on Affymetrix microarrays. Using class prediction algorithms, we identified 264 robust grade-associated markers, six of which could accurately classify G1 and G3 tumors, and separate G2 tumors into two highly discriminant classes (termed G2a and G2b genetic grades) with patient survival outcomes highly similar to those with G1 and G3 histology, respectively. Statistical analysis of conventional clinical variables further distinguished G2a and G2b subtypes from each other, but also from histologic G1 and G3 tumors. In multivariate analyses, genetic grade was consistently found to be an independent prognostic indicator of disease recurrence comparable to that of lymph node status and tumor size. When incorporated into the Nottingham Prognostic Index, genetic grade enhanced detection of patients with less harmful tumors, likely to benefit little from adjuvant therapy. Our findings show that a genetic grade signature can improve prognosis and therapeutic planning for breast cancer patients, and support the view that low and high grade disease, as defined genetically, reflect independent pathobiological entities rather than a continuum of cancer progression. Three separate breast cancer cohorts were analyzed: 1) Uppsala (n=249), 2) Stockholm (n=58), 3) Singapore (n=40). The Uppsala and Singapore data can be accessed here. The Stockholm cohort data can be accessed at GEO Series GSE1456. Experiment Overall Design: All tumor specimens were assessed on U133 A and B arrays.

Project description:Introduction: MicroRNAs (miRNAs) are small non-coding RNA that play a vital role in cancer progression. Neo-adjuvant chemotherapy (NAC) has become the standard of care for locally advanced breast cancer. The aim of this study was to evaluate miRNA alterations during NAC using multiple samples of tissue and serum to correlate miRNA expression with clinico-pathological features and patient outcomes. Methods: Tissue and serum samples were collected from patients with locally advanced breast cancer undergoing NAC at four time points: time of diagnosis, after the first and fourth cycle of doxorubicin/cyclophosphamide treatment, and after the fourth cycle of docetaxel administration. First, we evaluated the miRNA expression profiles in tissue and correlated expression with clinico-pathological features. Then, a panel of four miRNAs (miR-451, miR-3200, miR-21, and miR-205) in serum samples was further validated using quantitative reverse-transcription polymerase chain reaction (RT-qPCR). The alterations in serum levels of miRNA, associations with clinical and pathological responses, correlation with clinico-pathological features, and survival outcomes were studied using Friedman, Mann-Whitney U, Spearman, Wilcoxon signed-ranks tests. Pâ¤0.05 was considered statistically significant. Results: We analyzed 32 tissue samples and 108 serum samples from 8 patients and 27 patients, respectively. MicroRNA expression profiling of tumor versus normal tissue revealed more than 100 differentially expressed miRNAs. Serum miR-451 levels were significantly decreased during treatment, and higher serum levels were associated with improved clinical and pathological responses and disease-free survival. The serum levels of miR-3200 declined during NAC, and higher serum levels were associated with lower residual breast cancer burden and relapse rates. Conclusion: Variations in serum miRNA levels during NAC treatment may be therapeutically significant for predicting response and survival outcomes. Serum and tissue from a total of 27 consecutive patients diagnosed with locally advanced breast cancer undergoing NAC treatment were collected however microarray data were generated from tissue biopsy of 5 patients at four timepoints for both Normal and tumor. Additionally 3 tissue from only tumor at four timepoints and 6 patients at two timepoint T1 and T4

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Expression Profiles of Breast Tumors from Singapore and Europe

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