PRKD3 and cancer: Protein Kinase D3 has been implicated in a variety of functions in broad ranges of cancer types.2, 3, 4, 5, 6, 7 Additionally, PRKD3 has been suggested to be up‐regulated and involved in mediating the survival, differentiation, migration and proliferation of the triple‐negative breast cancer cells.8, 9, 10 Diacylglycerol (DAG) has been found to bind to the cysteine‐rich domain of PRKD3 and played important roles in PRKD3 activation via PKC signalling.11 However, the downstream pathway of PRKD3 is not well‐understood.