PRKCD and colorectal carcinoma: First, we analyzed correlations between the expression of PKCs and that of B7-H4 in CRC patient samples based on the LinkedOmics and GEPIA databases and found that the expression of both PKRCA and PRKCD (PKCδ) was positively associated with B7-H4 expression, but only PKCδ was abnormally upregulated in colorectal cancer tissues (Additional file 1: Figure S1).