Transcription profiling of mouse PKCa -/- mutant vs. wild type small intestine

Members of the PKC family of serine / threonine kinases play key regulatory roles in numerous cellular processes including differentiation and proliferation. Of the eleven mammalian PKC isoforms known several have been implicated in tumor development and progression. However, in most cases isotype specificity is poorly defined and even contrary functions for a single PKC have been reported, mostly because appropriate molecular and genetic tools were missing to specifically assess the contribution of single PKC isoforms in vivo. In this report we therefore used PKC genetic targeting to study the role of PKCa and PKCz in colorectal cancer. Both isoforms were found to be strongly down-regulated in intestinal tumors of ApcMin/+ mice. A deletion of PKCz did not affect tumorigenesis in this animal model. In contrast, PKCa deficient ApcMin/+ mice developed more aggressive tumors and died significantly earlier than their PKCa proficient littermates. Even without an additional Apc mutation PKCa knock out mice showed an elevated tendency to develop spontaneous intestinal tumors. Transcriptional profiling revealed a role for this kinase in regulating EGFR signaling and proposed a synergistic mechanism for EGFR / AP-1 and WNT / APC pathways in mediating intestinal tumor development. Experiment Overall Design: Adult male animals (PKCa -/- and congenic wt controls; 50-60 days old) were sacrificed by cervical dislocation. Small intestines were dissected and total RNA (~5µg per sample) was extracted using the QIAGEN RNeasy kit. Experiment Overall Design: Sample processing (performed at the RZPD, Deutsches Ressourcenzentrum für Genomforschung GmbH, Heubnerweg 6, 14059 Berlin) included cRNA generation and labeling with biotin. cRNA samples were hybridized to the GeneChips and chips stained with a streptavidine-phycoerythrine conjugate, Experiment Overall Design: washed and scanned. Hybridization images were analyzed using Experiment Overall Design: GCOS™ 1.1.