Molecular subtypes including luminal subtypes A and B drive patient outcomes in human breast cancer but the biological basis for this is not completely understood (1-4). We mined published microarray data (5, 6) to discover in an unbiased fashion the most distinguishing genetic and transcriptional features of tumors of each breast cancer molecular subtype. We identified a single nucleotide polymorphism, rs10879065, residing within MYRFL, as among the most significant genetic differences in the

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... umors of patients with luminal B breast cancer. Analysis of a separate cohort of patients with luminal B subtype breast cancer demonstrated that the MYRFL gene was not differentially expressed, however. Kaplan-Meier survival data revealed that MYRFL primary tumor expression was correlated with distant metastasis-free survival in patients with basal-like breast cancer. Sequence variation in the MYRFL gene may be important in understanding differences in genetic background that favor development of luminal B subtype human breast cancer.