Our long-term goal is to identify protein kinase C (PKC) signaling mechanisms that contribute to cancer and translate these mechanistic insights into better prognostic and therapeutic intervention strategies. In previous funding periods, we: 1) identified atypical PKC isozyme PKC? as an oncogene in non-small cell lung cancer (NSCLC), the leading cause of cancer death in the U.S.; 2) established that PKC? enforces a highly aggressive tumor-initiating cell (TIC) phenotype in two major NSCLC subtypes, lung adenocarcinoma (LADC) and lung squamous cell carcinoma (LSCC); and 3) identified a small molecule PKC? inhibitor that shows clinical promise for lung and ovarian cancer treatment. During the current funding period we showed that: 1) PKC? drives a LSCC TIC phenotype by directly phosphorylating and regulating the transcriptional activity of Sox2, a LSCC lineage-specific pluripotent stem cell factor; 2) PKC? establishes a LADC TIC phenotype by phosphorylating and regulating Elf3, a key transcription factor in LADC; 3) PKC? directly phosphorylates and activates the Rho family GTPase GEF Ect2 to regulate its oncogenic activity; 4) Ect2 regulates ribosomal DNA transcription by binding the Upstream binding factor 1 (Ubf1), a major rDNA transcription factor, and recruiting Rac1 and Npm to rDNA to drive transformed growth and lung tumor formation in vivo; 5) PKC?-mediated Ect2 phosphorylation is required for Ect2-driven rDNA transcription. Our preliminary studies indicate that: 1) PKC? phosphorylates Ubf1 at a unique site required for Ect2 binding and rDNA transcription; 2) PKC?-mediated Sox2 phosphorylation regulates Sox2 binding to direct transcriptional targets implicated in LSCC transformation; 3) PKC? and Ect2 are overexpressed in a genetically-tractable mouse model of Sox2-dependent LSCC that faithfully recapitulates many aspects of human LSCC. Based on these data, we hypothesize that: 1) PKC? regulates Ubf1-, Ect2-dependent rRNA transcription and LSCC transformation through phosphorylation- dependent regulation of Ubf1-Ect2 binding interactions; 2) PKC?-mediated Sox2 phosphorylation controls Sox2 transcriptional programming of LSCC TICs; and 3) Prkci and Ect2 are required for Sox2-driven mouse LSCC tumorigenesis in vivo. These hypotheses will be tested by completing three interrelated specific aims designed to: 1) determine the mechanism by which PKC? regulates ribosomal RNA transcription in LSCC cells; 2) identify and functionally characterize direct PKC?-Sox2 transcriptional targets involved in LSCC tumorigenesis; and 3) determine the role of PKC? and Ect2 in Sox2-dependent LSCC tumorigenesis in vivo. Successful completion of these aims will provide significant new insight into how three oncogenes that are coordinately amplified and overexpressed in the vast majority of human LSCCs, PRKCI, ECT2 and SOX2, cooperate to drive LSCC tumorigenesis. Mechanistic insights gained through these studies will provide new therapeutic opportunities to improve treatment of LSCC. Translation of key findings will be facilitated by our ongoing clinical development of the PKC? inhibitor Auranofin.

Public Health Relevance

Lung cancer is the number one cause of cancer death in the United States. Protein kinase C? (PKC?) is an oncogene, prognostic marker and therapeutic target in lung cancer. This project will investigate how PKC? stimulates lung squamous cell carcinoma cell growth in vitro, assess the role of PKC? in lung squamous cell carcinoma development, progression and spread in pre-clinical animal models in vivo, and determine the translational relevance of these findings to primary human lung cancers.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Special Emphasis Panel (ZRG1)
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Xu, Wanping
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Mayo Clinic Jacksonville
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Fields, Alan P; Ali, Syed A; Justilien, Verline et al. (2017) Targeting oncogenic protein kinase C? for treatment of mutant KRAS LADC. Small GTPases 8:58-64
Wang, Y; Justilien, V; Brennan, K I et al. (2017) PKC? regulates nuclear YAP1 localization and ovarian cancer tumorigenesis. Oncogene 36:534-545
Justilien, Verline; Ali, Syed A; Jamieson, Lee et al. (2017) Ect2-Dependent rRNA Synthesis Is Required for KRAS-TRP53-Driven Lung Adenocarcinoma. Cancer Cell 31:256-269
Fields, Alan P; Justilien, Verline; Murray, Nicole R (2016) The chromosome 3q26 OncCassette: A multigenic driver of human cancer. Adv Biol Regul 60:47-63
Ali, Syed A; Justilien, Verline; Jamieson, Lee et al. (2016) Protein Kinase C? Drives a NOTCH3-dependent Stem-like Phenotype in Mutant KRAS Lung Adenocarcinoma. Cancer Cell 29:367-378
Fields, Alan P; Ali, Syed A; Murray, Nicole R (2016) Oncogenic PKC? decides tumor-initiating cell fate. Cell Cycle 15:2383-4
Murray, Nicole R; Justilien, Verline; Fields, Alan P (2016) SOX2 Determines Lineage Restriction: Modeling Lung Squamous Cell Carcinoma in the Mouse. Cancer Cell 30:505-507
Liou, Geou-Yarh; Döppler, Heike; Braun, Ursula B et al. (2015) Protein kinase D1 drives pancreatic acinar cell reprogramming and progression to intraepithelial neoplasia. Nat Commun 6:6200
Butler, Amanda M; Scotti Buzhardt, Michele L; Erdogan, Eda et al. (2015) A small molecule inhibitor of atypical protein kinase C signaling inhibits pancreatic cancer cell transformed growth and invasion. Oncotarget 6:15297-310
Justilien, Verline; Fields, Alan P (2015) Molecular pathways: novel approaches for improved therapeutic targeting of Hedgehog signaling in cancer stem cells. Clin Cancer Res 21:505-13

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