Differential expression of Axl and Gas6 in renal cell carcinoma reflecting tumor advancement and survival

PURPOSE: Overexpression of the receptor tyrosine kinase Axl is implicated in several cancers. Therefore, we conducted this study to determine the expression of Axl and its ligand Gas6 in various renal cell carcinoma (RCC) types and in oncocytoma. EXPERIMENTAL DESIGN: Real-time quantitative reverse transcription-PCR was used to quantify tumor mRNA levels for Axl and Gas6 in a cohort (n = 221) of RCC patients. Serum levels of soluble sAxl and Gas6 proteins were measured using specific ELISA assays (n = 282). The presence of Axl protein in tumor tissue was evaluated by immunohistochemistry (n = 294). Results were correlated to tumor-associated variables, clinical biochemical tests, and patient survival. RESULTS: Tumor Axl mRNA levels correlated independently to survival when assessed against tumor stage and grade. In the study group, the median cancer-specific survival of all RCC patients during 307 months of follow-up was 55 months (confidence interval, +/-40.4). The 25% of patients with lowest tumor Axl mRNA levels had significantly better survival than the rest (P = 0.0005), with 70% of the patients still alive at the end of follow-up. In contrast, in patients with medium-high Axl mRNA, only 25% were alive at the end of follow-up. Tumor Gas6 mRNA levels correlated to survival, tumor-associated variables, and disease severity as did serum levels of soluble sAxl and Gas6 protein. However, no correlation between Axl protein in tumor tissue and survival was found. CONCLUSIONS: Axl and Gas6 expression in RCC are associated with tumor advancement and patient survival. In particular, low tumor Axl mRNA levels independently correlated with improved survival

Solution Structure of Tensin2 SH2 Domain and Its Phosphotyrosine-Independent Interaction with DLC-1

Background: Src homology 2 (SH2) domain is a conserved module involved in various biological processes. Tensin family member was reported to be involved in tumor suppression by interacting with DLC-1 (deleted-in-liver-cancer-1) via its SH2 domain. We explore here the important questions that what the structure of tensin2 SH2 domain is, and how it binds to DLC-1, which might reveal a novel binding mode. Principal Findings: Tensin2 SH2 domain adopts a conserved SH2 fold that mainly consists of five b-strands flanked by two a-helices. Most SH2 domains recognize phosphorylated ligands specifically. However, tensin2 SH2 domain was identified to interact with nonphosphorylated ligand (DLC-1) as well as phosphorylated ligand. Conclusions: We determined the solution structure of tensin2 SH2 domain using NMR spectroscopy, and revealed the interactions between tensin2 SH2 domain and its ligands in a phosphotyrosine-independent manner

Phosphotyrosine Profiling of NSCLC Cells in Response to EGF and HGF Reveals Network Specific Mediators of Invasion

Growth factor signaling is deregulated in cancer and often leads to invasion, yet receptor tyrosine kinase signaling pathways driving invasion under different growth factor conditions are not well understood. To identify specific signaling molecules regulating invasion of A549 non-small cell lung carcinoma (NSCLC) cells downstream of the epidermal growth factor receptor (EGFR) and Met, quantitative site-specific mass spectrometric analysis of tyrosine phosphorylation was performed following epidermal growth factor (EGF) or hepatocyte growth factor (HGF) stimulation, at three different growth factor concentrations and at two time points. Through this analysis, the temporal and concentration dependent phosphorylation profiles were obtained for 131 and 139 sites downstream of EGF and HGF stimulation, respectively. To characterize the effect of these signaling network alterations, we quantified 3D cell migration/invasion through Matrigel. Partial least-squares regression (PLSR) analysis was performed to identify the tyrosine phosphorylation sites most strongly correlated with EGF and/or HGF mediated invasion. Potential common and specific signaling events required for driving invasion downstream of EGFR and Met were identified using either a combined or two independent PLSR models, based on the quantitative EGF or HGF data. Our data highlight the integration and compartmentalization of signaling required for invasion in cancer.National Institutes of Health (U.S.) (Grant R01CA118705)National Institutes of Health (U.S.) (Grant U54CA112967)National Institutes of Health (U.S.) (Grant U24CA159988)National Institutes of Health (U.S.) (Grant SU01CA141556-03