Other transcription factors have been shown to interact with the CIS promoter such as Ets factors GABPα/β and NFκB, and deletion of STAT 5 elements in the proximal human CIS promoter still results in substantial levels of basal activity (Verdier et al, 1998), so other cis acting factors may be important in maintaining CIS expression in these breast cancer cells. This evidence concerns the gene NFKB1 and breast carcinoma.