Protein kinase Cδ and caspase-3 modulate TRAIL-induced apoptosis in breast tumor cells.

Abstract

This report describes that protein kinase C delta (PKCδ) overexpression prevents TRAIL-induced apoptosis in breast tumor cells; however, the regulatory mechanism(s) involved in this phenomenon is(are) incompletely understood. In this study, we have shown that TRAIL-induced apoptosis was significantly inhibited in PKCδ overexpressing MCF-7 (MCF7/PKCδ) cells. Our data reveal that PKCδ inhibits caspase-8 activation, a first step in TRAIL-induced apoptosis, thus preventing TRAIL-induced apoptosis. Inhibition of PKCδ using rottlerin or PKCδ siRNA reverses the inhibitory effect of PKCδ on caspase-8 activation leading to TRAIL-induced apoptosis. To determine if caspase-3-induced PKCδ cleavage reverses its inhibition on caspase-8, we developed stable cell lines that either expresses wild-type PKCδ (MCF-7/cas-3/PKCδ) or caspase-3 cleavage-resistant PKCδ mutant (MCF-7/cas-3/PKCδ mut) utilizing MCF-7 cells expressing caspase-3. Cells that overexpress caspase-3 cleavage-resistant PKCδ mutant (MCF-7/cas-3/PKCδmut) significantly inhibited TRAIL-induced apoptosis when compared to wild-type PKCδ (MCF-7/cas-3/PKCδ) expressing cells. In MCF-7/cas-3/PKCδmut cells, TRAIL-induced caspase-8 activation was blocked leading to inhibition of apoptosis when compared to wild-type PKCδ (MCF-7/cas-3/PKCδ) expressing cells. Together, these results strongly suggest that overexpression of PKCδ inhibits caspase-8 activation leading to inhibition of TRAIL-induced apoptosis and its inhibition by rottlerin, siRNA, or cleavage by caspase-3 sensitizes cells to TRAIL-induced apoptosis. Clinically, PKCδ overexpressing tumors can be treated with a combination of PKCδ inhibitor(s) and TRAIL as a new treatment strategy.

• Authors: Shuping Yin, Seema Sethi, Kaladhar B Reddy
• Journal: Journal of cellular biochemistry (J Cell Biochem) Vol. 111 Issue 4 Pg. 979-87 (Nov 01 2010) ISSN: 1097-4644 [Electronic] United States
• PMID: 20665667 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• RNA, Small Interfering
• TNF-Related Apoptosis-Inducing Ligand
• PRKCD protein, human
• Protein Kinase C-delta
• CASP3 protein, human
• Caspase 3

Topics

• Apoptosis (drug effects)
• Breast Neoplasms (enzymology, pathology)
• Caspase 3 (metabolism)
• Cell Line, Tumor
• Cytoprotection (drug effects)
• Female
• Humans
• Immunohistochemistry
• Protein Kinase C-delta (metabolism)
• RNA, Small Interfering (metabolism)
• TNF-Related Apoptosis-Inducing Ligand (pharmacology)