The complex interplays among transcription factors are essential for development and progression of breast cancer to a lethal disease.6 For example, the transcription factor FOXK2 represses the proliferation and invasion of breast cancer cells via reciprocal successive feedback by transcription factor HIF-1β.24 It has been shown that C-MYC is a crucial transcription factor for breast cancer progression and tamoxifen resistance.39 In this report we uncovered the connection between the transcription factors SOX9 and C-MYC. This evidence concerns the gene ARNT and breast carcinoma.