African Americans (AAs) have higher mortality rate from breast cancer than that 
of Caucasian Americans (CAs) even when socioeconomic factors are accounted for. 
To better understand the driving biological factors of this health disparity, we 
performed a comprehensive differential gene expression analysis, including 
subtype- and stage-specific analysis, using the breast cancer data in the Cancer 
Genome Atlas (TCGA). In total, 674 unique genes and other transcripts were found 
differentially expressed between these two populations. The numbers of 
differentially expressed genes between AA and CA patients increased in each 
stage of tumor progression: there were 26 in stage I, 161 in stage II, and 223 
in stage III. Resistin, a gene that is linked to obesity, insulin resistance, 
and breast cancer, was expressed more than four times higher in AA tumors. An 
uncharacterized, long, non-coding RNA, LOC90784, was down-regulated in AA 
tumors, and its expression was inversely related to cancer stage and was the 
lowest in triple negative AA breast tumors. Network analysis showed increased 
expression of a majority of components in p53 and BRCA1 subnetworks in AA breast 
tumor samples, and members of the aurora B and polo-like kinase signaling 
pathways were also highly expressed. Higher gene expression diversity was 
observed in more advanced stage breast tumors suggesting increased genomic 
instability during tumor progression. Amplified resistin expression may indicate 
insulin-resistant type II diabetes and obesity are associated with AA breast 
cancer. Expression of LOC90784 may have a protective effect on breast cancer 
patients, and its loss, particularly in triple negative breast cancer, could be 
having detrimental effects. This work helps elucidate molecular mechanisms of 
breast cancer health disparity and identifies putative biomarkers and 
therapeutic targets such as resistin, and the aurora B and polo-like kinase 
signaling pathways for treating AA breast cancer patients.