RT Journal Article SR Electronic T1 Protein Kinases D2 and D3 Are Novel Growth Regulators in HCC1806 Triple-negative Breast Cancer Cells JF Anticancer Research JO Anticancer Res FD International Institute of Anticancer Research SP 393 OP 399 VO 33 IS 2 A1 QIN HAO A1 RAYMOND MCKENZIE A1 HUACHEN GAN A1 HUA TANG YR 2013 UL http://ar.iiarjournals.org/content/33/2/393.abstract AB Aim: The role of protein kinase D (PKD) in the context of breast cancer cell biology is not clear. Materials and Methods: The expression of PKD isoforms was assessed in various breast cancer cell lines and PKD isoform-specific siRNAs and selective inhibitors were used to study the role of PKD in breast cancer cell growth. Results: PKD2 and PKD3 were two major isoforms expressed at the highest levels in tumorgenic HCC1806 triple-negative breast cancer cells. Silencing PKD2 or PKD3 significantly inhibited HCC1806 cell proliferation, and PKD3 silencing had a higher inhibitory effect than PKD2 silencing on cell growth and PKD-mediated signaling. HCC1806 breast cancer cells were highly responsive to PKD inhibitors but not to a general protein kinase C (PKC) inhibitor. Conclusion: We have identified PKD2 and PKD3, especially PKD3, as novel cell growth regulators in HCC1806 triple-negative breast cancer cells. Targeting PKD instead of all PKCs effectively inhibited cell proliferation in a number of breast cancer cell lines.