Protein Kinase C δ Is a Downstream Effector of Oncogenic K-ras in Lung Tumors
- 14 March 2011
- journal article
- Published by American Association for Cancer Research (AACR) in Cancer Research
- Vol. 71 (6), 2087-2097
- https://doi.org/10.1158/0008-5472.can-10-1511
Abstract
Oncogenic activation of K-ras occurs commonly in non–small cell lung cancer (NSCLC), but strategies to therapeutically target this pathway have been challenging to develop. Information about downstream effectors of K-ras remains incomplete, and tractable targets are yet to be defined. In this study, we investigated the role of protein kinase C δ (PKCδ) in K-ras–dependent lung tumorigenesis by using a mouse carcinogen model and human NSCLC cells. The incidence of urethane-induced lung tumors was decreased by 69% in PKCδ-deficient knockout (δKO) mice compared with wild-type (δWT) mice. δKO tumors are smaller and showed reduced proliferation. DNA sequencing indicated that all δWT tumors had activating mutations in KRAS, whereas only 69% of δKO tumors did, suggesting that PKCδ acts as a tumor promoter downstream of oncogenic K-ras while acting as a tumor suppressor in other oncogenic contexts. Similar results were obtained in a panel of NSCLC cell lines with oncogenic K-ras but which differ in their dependence on K-ras for survival. RNA interference–mediated attenuation of PKCδ inhibited anchorage-independent growth, invasion, migration, and tumorigenesis in K-ras–dependent cells. These effects were associated with suppression of mitogen-activated protein kinase pathway activation. In contrast, PKCδ attenuation enhanced anchorage-independent growth, invasion, and migration in NSCLC cells that were either K-ras–independent or that had WT KRAS. Unexpectedly, our studies indicate that the function of PKCδ in tumor cells depends on a specific oncogenic context, as loss of PKCδ in NSCLC cells suppressed transformed growth only in cells dependent on oncogenic K-ras for proliferation and survival. Cancer Res; 71(6); 2087–97. ©2011 AACR.Keywords
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