Project description:Non-small cell lung cancer (NSCLC), the most frequent subtype of lung cancer, remains a highly lethal malignancy and one of the leading causes of cancer deaths worldwide. Mutant KRAS is the prevailing oncogenic driver of lung adenocarcinoma, the most common histological form of NSCLC. In this study, we examined the role of PKCe, an oncogenic kinase highly expressed in NSCLC and other cancers, in KRAS-driven tumorigenesis. Notably, database analysis revealed an association between PKCe expression and poor outcome in lung adenocarcinoma patients specifically having KRAS mutation. By generating a PKCe-deficient, conditionally activatable allele of oncogenic Kras (LSL-Kras G12D ;PKCe -/- mice) we were able to demonstrate the requirement of PKCe for Kras-driven lung tumorigenesis in vivo, which is consistent with the impaired transformed growth observed in PKCe-deficient KRAS-dependent NSCLC cells. Moreover, PKCe-knockout mice were found to be less susceptible to lung tumorigenesis induced by benzo[a]pyrene, a carcinogen that induces mutations in Kras. Mechanistic analysis using RNA-Seq revealed little overlapping for PKCe and KRAS in the control of genes/biological pathways relevant in NSCLC, suggesting that a permissive role of PKCe in KRAS-driven lung tumorigenesis may involve non-redundant mechanisms. Our results thus highlight the relevance and potential of targeting PKCe for lung cancer therapeutics.
Project description:Atrial fibrillation (AF), the most common abnormal heart rhythm, is a major cause for stroke. Aging is the greatest risk factor for AF, however, specific ionic pathways that can elucidate how aging leads to AF remain elusive. We used young and old wild type (WT) and PKC epsilon (PKCepsilon) knockout (KO) mice, whole animal, and cellular electrophysiology, as well as whole heart, and cellular imaging to investigate how aging leads to the aberrant functioning of a potassium current, and consequently to AF facilitation. Our experiments showed that knocking out PKC epsilon abrogates the effects of aging on AF by preventing the development of a constitutively active acetylcholine sensitive inward rectifier potassium current (IKACh). Moreover, blocking this abnormal current in the old heart prevents AF inducibility. Our studies demonstrate that in the aging heart, IKACh is constitutively active in a PKC epsilon dependent manner, contributing to the perpetuation of AF
Project description:Oncogenic STAT3 functions are known in various malignancies. We found that STAT3 plays an unexpected tumor suppressive role in KRAS-mutant non-small-cell-lung cancer (NSCLC). In mice, tissue-specific inactivation of Stat3 resulted in increased Kras (G12D)-driven NSCLC initiation and malignant progression leading to markedly reduced survival. Clinically, low STAT3 expression levels correlate with poor survival in human lung adenocarcinoma patients with smoking history. Consistently, KRAS-mutant lung tumors showed reduced STAT3 levels. Mechanistically, we show that STAT3 controls NFκB-induced IL-8-expression by sequestering NFκB in the cytoplasm while IL-8 in turn regulates myeloid tumor infiltration and tumor vascularization thereby promoting tumor progression. These results identify a novel STAT3-NFκB-IL-8 axis in KRAS-mutant NSCLC with therapeutic and prognostic relevance WT: Control lung; KRAS: Lung tumors expressing KRAS G12D; KRAS STAT3 KO: Lung tumors expressing KRAS G12D- STAT3 deficient; tumors of four mice pooled per sample
Project description:The PKC-regulated genome protective pathway provides transformed cells a failsafe to successfully complete mitosis. Despite the necessary role for Aurora B in this programme, it is unclear whether its requirement is sufficient or if other PKC cell cycle targets are involved. To address this, we developed a trapping strategy using UV-photocrosslinkable amino acids encoded in the PKC kinase domain. The validation of the mRNA binding protein SERBP1 as a PKC substrate revealed a series of mitotic events controlled by the catalytic form of PKC. PKC represses protein translation, altering SERBP1 binding to the 40S ribosomal subunit and promoting the assembly of ribonucleoprotein granules containing SERBP1, termed M-bodies. Independent of Aurora B, SERBP1 is shown to be necessary for chromosome segregation and successful cell division, correlating with M-body formation. This requirement for SERBP1 demonstrates that Aurora B acts in concert with translational regulation in the PKC-controlled pathway exerting genome protection.
Project description:KRAS, mutated in ~30% of all cancers, activates the RAF-MEK-ERK signaling cascade. It has previously been shown that CRAF is required for growth of KRAS mutant lung tumors but the requirement for CRAF kinase activity is unknown. Here, we show that subsets of KRAS mutant tumors are dependent on CRAF for growth. Kinase-dead but not dimer-defective CRAF rescued growth inhibition suggesting that dimerization but not kinase activity is required. Quantitative proteomics demonstrated enrichment of CRAF:ARAF dimers in KRAS mutant cells and depletion of both CRAF and ARAF rescued the CRAF loss phenotype. Mechanistically, CRAF depletion caused sustained ERK activation and induction of cell cycle arrest. Treatment with low dose MEK or ERK inhibitor rescued the CRAF loss phenotype. Our studies highlight the role of CRAF in regulating MAPK signal intensity to promote tumorigenesis downstream of mutant KRAS and suggest that disrupting dimerization or degrading CRAF may have therapeutic benefit.