MKI67, AURKA and UBE2C: We focused on proliferation genes because of the importance of this process on breast cancer prognosis (7 (link)). Genomic studies demonstrated the existence of a proliferation cluster containing numerous correlated genes. We chose these three genes because they are known to play an active role in proliferation process in breast cancer: MKI67 is coding for KI67 protein, which is routinely explored by means of immunohistochemistry, AURKA is considered as the proliferation prototypic gene and UBE2C bears a high prognostic informativity (8 (link), 9 (link)).
ESR1, GATA3, FOXA1 and XBP1: Numerous studies, notably based on microarrays, have shown that expressions of GATA3, FOXA1 and XBP1 were strongly correlated to that of ESR1 (10 (link)).
TNFAIP1/POLDIP2, RAF1/MKRN2 and TBCB/POLR2I: The examples of TNFAIP1/POLDIP2, RAF1/MKRN2 and TBCB/POLR2I are of particular interest because these couples of genes demonstrated co-regulatory pattern in breast cancer tumours, are located at the same locus and are organized in sense–antisense architecture on the opposite DNA strands of chromosome 17, 3 and 19, respectively (11 ).