Tenascin-C serum levels and its prognostic power in non-small cell lung cancer.

BACKGROUND: Tenascin-C is overexpressed in the stroma of most solid malignancies and may function as a diagnostic tumor marker. This study was conducted to evaluate the potential significance of Tenascin-C as a predictive marker for tumor progression in the sera of non-small cell lung cancer (NSCLC) patients. RESULTS: Serum concentration of Tenascin-C is significantly elevated in NSCLC patients compared to healthy controls (p=0.013). The sensitivity of Tenascin-C in detecting NSCLC was 74% at a specificity of 57%. Elevated Tenascin-C serum values are associated with larger tumor size and lymph node involvement (p=0.022 and p=0.036, respectively). The Kaplan-Meyer-curves showed a significant association of Tenascin-C with the patient's overall survival (p=0.004), but not with the recurrence-free survival (p=0.328). METHODS: We quantified Tenascin-C in the sera of 103 NSCLC patients and 76 healthy blood donors by enzyme-linked immune-absorbance assay tests. Prognostic significance was determined by area under the curve analysis and Youden-index. The results were correlated with clinical, histopathological, and patient survival data (Chi-square test, Kaplan-Meier analysis, log-rank test, multivariate Cox-regression analysis). CONCLUSION: Although significantly elevated in patients with NSCLC, the sensitivity and specificity of the Tenascin-C serum quantification test was low. However, although failing to be an independent prognosticator in multivariate analysis, the results implicate Tenascin-C as a predictive prognostic marker for NSCLC patients. The data must be further validated in future prospective trials with larger patient cohorts.

Lysosomal targeting of the CLN7 membrane glycoprotein and transport via the plasma membrane require a dileucine motif.

CLN7 is a polytopic lysosomal membrane protein deficient in variant late infantile neuronal ceroid lipofuscinosis, a neurodegenerative lysosomal storage disorder. In this study fluorescence protease protection assays and mutational analyses revealed the N- and C-terminal tails of CLN7 in the cytosol and two N-glycosylation sites at N371 and N376. Both partially and non-glycosylated CLN7 were correctly transported to lysosomes. To identify lysosomal targeting motifs, we generated CD4-chimera fused to the N- and C-terminal domains of CLN7. Lysosomal localization of the chimeric proteins requires a consensus acidic dileucine-based motif in the N-terminus and two tandem tyrosine-based signals in the C-terminus. Mutation of these sorting motifs resulted in cell surface redistribution of CD4 chimeras. However, the dileucine-based motif is of critical importance for lysosomal localization of the full-length CLN7 in different cell lines. Cell surface biotinylation revealed that at equilibrium 22% of total CLN7 is localized at the plasma membrane. Mutation of the dileucine motif or the co-expression of dominant-negative mutant dynamin K44A led to a further increase of CLN7 at the plasma membrane. Our data demonstrate that CLN7 contains several cytoplasmic lysosomal targeting signals of which the N-terminal dileucine-based motif is required for the predominant lysosomal targeting along the indirect pathway and clathrin-mediated endocytosis of CLN7.