The Protein Kinase D (PKD) family of serine/threonine kinases consists of three members-PKD1, PKD2, and PKD3. While PKD1 in many cancers has been identified as a suppressor of the invasive phenotype, the two other PKD subtypes, PKD2 and PKD3, have been attributed oncogenic functions. In invasive Breast Cancer cells PKD1 expression is downregulated by methylation of the PRKD1 promoter. On the other hand, PKD2 and PKD3 are not silenced, and drive proliferation, invasion, and mediate chemoresistance. Two strategies emerge to utilize this knowledge for novel treatment opportunities. First, pan PKD inhibitors could be developed and used for these aggressive cancers. An alternative approach to obtain similar effects would be to induce the re-expression of PKD1.