Nonhematopoietic IRAK1 drives arthritis via neutrophil chemoattractants.

IL-1 receptor-activated kinase 1 (IRAK1) is involved in signal transduction downstream of many TLRs and the IL-1R. Its potential as a drug target for chronic inflammatory diseases is underappreciated. To study its functional role in joint inflammation, we generated a mouse model expressing a functionally inactive IRAK1 (IRAK1 kinase deficient, IRAK1KD), which also displayed reduced IRAK1 protein expression and cell type-specific deficiencies of TLR signaling. The serum transfer model of arthritis revealed a potentially novel role of IRAK1 for disease development and neutrophil chemoattraction exclusively via its activity in nonhematopoietic cells. Consistently, IRAK1KD synovial fibroblasts showed reduced secretion of neutrophil chemoattractant chemokines following stimulation with IL-1ß or human synovial fluids from patients with rheumatoid arthritis (RA) and gout. Together with patients with RA showing prominent IRAK1 expression in fibroblasts of the synovial lining, these data suggest that targeting IRAK1 may be therapeutically beneficial. As pharmacological inhibition of IRAK1 kinase activity had only mild effects on synovial fibroblasts from mice and patients with RA, targeted degradation of IRAK1 may be the preferred pharmacologic modality. Collectively, these data position IRAK1 as a central regulator of the IL-1ß-dependent local inflammatory milieu of the joints and a potential therapeutic target for inflammatory arthritis.

Adult stromal cells derived from human adipose tissue provoke pancreatic cancer cell death both in vitro and in vivo.

BACKGROUND: Normal tissue homeostasis is maintained by dynamic interactions between epithelial cells and their microenvironment. Disrupting this homeostasis can induce aberrant cell proliferation, adhesion, function and migration that might promote malignant behavior. Indeed, aberrant stromal-epithelial interactions contribute to pancreatic ductal adenocarcinoma (PDAC) spread and metastasis, and this raises the possibility that novel stroma-targeted therapies represent additional approaches for combating this malignant disease. The aim of the present study was to determine the effect of human stromal cells derived from adipose tissue (ADSC) on pancreatic tumor cell proliferation. PRINCIPAL FINDINGS: Co-culturing pancreatic tumor cells with ADSC and ADSC-conditioned medium sampled from different donors inhibited cancer cell viability and proliferation. ADSC-mediated inhibitory effect was further extended to other epithelial cancer-derived cell lines (liver, colon, prostate). ADSC conditioned medium induced cancer cell necrosis following G1-phase arrest, without evidence of apoptosis. In vivo, a single intra-tumoral injection of ADSC in a model of pancreatic adenocarcinoma induced a strong and long-lasting inhibition of tumor growth. CONCLUSION: These data indicate that ADSC strongly inhibit PDAC proliferation, both in vitro and in vivo and induce tumor cell death by altering cell cycle progression. Therefore, ADSC may constitute a potential cell-based therapeutic alternative for the treatment of PDAC for which no effective cure is available.