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PURPOSE: Histologic tumor grade is a well-established prognostic factor for breast cancer, and tumor grade-associated genes are the common denominator of many prognostic gene signatures. The objectives of this study are as follows: (a) to develop a simple gene expression index for tumor grade (molecular grade index or MGI), and (b) to determine whether MGI and our previously described HOXB13:IL17BR index together provide improved prognostic information. EXPERIMENTAL DESIGN: From our previously published list of genes whose expression correlates with both tumor grade and tumor stage progression, we selected five cell cycle-related genes to build MGI and evaluated MGI in two publicly available microarray data sets totaling 410 patients. Using two additional cohorts (n = 323), we developed a real-time reverse transcription PCR assay for MGI, validated its prognostic utility, and examined its interaction with HOXB13:IL17BR. RESULTS: MGI performed consistently as a strong prognostic factor and was comparable with a more complex 97-gene genomic grade index in multiple data sets. In patients treated with endocrine therapy, MGI and HOXB13:IL17BR modified each other's prognostic performance. High MGI was associated with significantly worse outcome only in combination with high HOXB13:IL17BR, and likewise, high HOXB13:IL17BR was significantly associated with poor outcome only in combination with high MGI. CONCLUSIONS: We developed and validated a five-gene reverse transcription PCR assay for MGI suitable for analyzing routine formalin-fixed paraffin-embedded clinical samples. The combination of MGI and HOXB13:IL17BR outperforms either alone and identifies a subgroup ( approximately 30%) of early stage estrogen receptor-positive breast cancer patients with very poor outcome despite endocrine therapy.

Original publication

DOI

10.1158/1078-0432.CCR-07-5026

Type

Journal article

Journal

Clin Cancer Res

Publication Date

01/05/2008

Volume

14

Pages

2601 - 2608

Keywords

Autoantigens, Breast Neoplasms, Centromere Protein A, Chromosomal Proteins, Non-Histone, Cohort Studies, Gene Expression Profiling, Genes, Neoplasm, Homeodomain Proteins, Humans, Kaplan-Meier Estimate, NIMA-Related Kinases, Prognosis, Proportional Hazards Models, Protein-Serine-Threonine Kinases, Receptors, Interleukin, Ribonucleoside Diphosphate Reductase