Receptor/ligand interactions in the C-C chemokine family

Neuroblastoma-derived secretory protein is a novel secreted factor overexpressed in neuroblastoma

Secreted proteins such as growth factors, cytokines, and chemokines play important roles in tumor development. Through expression microarray and bioinformatic analysis, we discovered a novel secreted protein, neuroblastoma-derived secretory protein (NDSP). The NDSP gene is found on chromosome 1q25.2 and encodes a 167 amino acid protein with a putative signal peptide. Using real-time PCR and immunoblotting, we find that NDSP is specifically overexpressed in neuroblastoma at much higher levels than other adult and pediatric malignancies and normal tissues. NDSP is an 18-kDa protein that can be secreted by NDSP-transfected HEK-293T cells, as well as, neuroblastoma cell lines endogenously expressing NDSP. Inhibiting NDSP expression in neuroblastoma cell lines with retrovirally transduced NDSP small hairpin interfering RNA, sh-NDSP, results in decreased cellular proliferation and colony formation. We also find inhibited extracellular signal-regulated kinase (ERK)1/2 phosphorylation in the sh-NDSP cell line. Treating the parental cell line with MAP/ERK kinase 1/2 inhibitors, which diminish ERK1/2 phosphorylation, results in decreased cell proliferation. Culturing these transduced cells with recombinant NDSP, reintroducing NDSP overexpression in the knockdown cell line, or inducing Ras oncogene overexpression for constitutive ERK1/2 activation results in a reversal of the growth-inhibited phenotype and proliferation rates similar to the control cells. In addition, reintroduction of NDSP overexpression in the sh-NDSP cell line results in ERK1/2 phosphorylation similar to control. We conclude that NDSP is specifically overexpressed in neuroblastoma and actively secreted from tumor cells. Furthermore, NDSP serves as a growth factor for neuroblastoma tumor cells through activation of the ERK-mediated proliferation pathway.

Thiazolidinedione inhibits production of RANTES in a cytokine-treated human lung epithelial cell line

The chemokine RANTES is a potent chemoattractant for eosinophils. RANTES is produced by lung epithelial cells during eosinophil-rich inflammatory diseases such as asthma. In this study, we examined the effects of thiazolidinediones (TZD) on RANTES expression in a human lung epithelial cell line, A549. In A549 cells, interleukin-1beta and tumor necrosis factor-alpha induced endogenous RANTES protein secretion, mRNA expression, and promoter activity. The TZD inhibited these effects. Our data indicate that the suppression of the expression of RANTES can be accomplished by TZD treatment, raising the possibility that TZD might be of therapeutic value in diseases such as asthma.

Modulation of RANTES production by human cytomegalovirus infection of fibroblasts

Chemokines play a major role in inflammatory responses and affect hematopoiesis both negatively and positively. We show that fresh isolates and laboratory strains (Towne and Ad-169) of human cytomegalovirus (HCMV) induce production of the CC chemokine RANTES in fibroblasts. Induction of extracellular RANTES production occurred as early as 8 h after infection, peaked around 24 h after infection, and was almost undetectable by 48 and 72 h. Upregulation occurred in the absence of viral DNA synthesis, suggesting that it was due to immediate-early-early HCMV gene expression. CMV infection stimulated RANTES transcription, since reverse transcription-PCR detected a sharp increase in RANTES RNA which persisted even when extracellular RANTES was no longer detected. Induction of RANTES in fibroblasts was not due to prior induction of tumor necrosis factor alpha or interleukin 1 beta. Down-regulation required an active viral genome. Decrease of RANTES in culture supernatants may be associated with the appearance of the HCMV CC chemokine receptor US28, since we show that this gene is transcribed as early as 8 h after infection. Modulation of CC chemokine production early during CMV infection might have a regulatory effect on viral replication, as well as affect immune surveillance.