Fig. 1

Flowchart of a novel identification strategy for housekeeping genes (nHKGs) in breast cancer. A list of 7780 genes was first obtained by selecting genes with low 0’s proportion and coefficient of variation (CV). 0’s proportion is defined as the proportion of different cell lines in which a given gene is not expressed; and CV is the ratio of the standard variation to the mean. Among the nHKG candidates, 10 with the lowest CVs were further validated by qRT-PCR and for their 0’s proportion in a large human tissue dataset from ICGC. For the sake of comparison, we included traditional housekeeping genes (tHKGs) selected from the literature, i.e., PUM1, RPL13A, PGK1, GUSB, ACTB, DIMT1, TUBA1A, GAPDH, B2M, 18S