Tumor cell integrin ß4 and tumor stroma E-/P-selectin cooperatively regulate tumor growth in vivo.

BACKGROUND: The immunological composition of the tumor microenvironment has a decisive influence on the biological course of cancer and is therefore of profound clinical relevance. In this study, we analyzed the cooperative effects of integrin ß4 (ITGB4) on tumor cells and E-/P-selectin on endothelial cells within the tumor stroma for regulating tumor growth by shaping the local and systemic immune environment. METHODS: We used several preclinical mouse models for different solid human cancer types (xenograft and syngeneic) to explore the role of ITGB4 (shRNA-mediated knockdown in tumor cells) and E-/P-selectins (knockout in mice) for tumor growth; effects on apoptosis, proliferation and intratumoral signaling pathways were determined by histological and biochemical methods and 3D in vitro experiments; changes in the intratumoral and systemic immune cell composition were determined by flow cytometry and immunohistochemistry; chemokine levels and their attracting potential were measured by ELISA and 3D invasion assays. RESULTS: We observed a very robust synergism between ITGB4 and E-/P-selectin for the regulation of tumor growth, accompanied by an increased recruitment of CD11b+ Gr-1Hi cells with low granularity (i.e., myeloid-derived suppressor cells, MDSCs) specifically into ITGB4-depleted tumors. ITGB4-depleted tumors undergo apoptosis and actively attract MDSCs, well-known to promote tumor growth in several cancers, via increased secretion of different chemokines. MDSC trafficking into tumors crucially depends on E-/P-selectin expression. Analyses of clinical samples confirmed an inverse relationship between ITGB4 expression in tumors and number of tumor-infiltrating leukocytes. CONCLUSIONS: These findings suggest a distinct vulnerability of ITGB4Lo tumors for MDSC-directed immunotherapies.

Procalcitonin Exerts a Mediator Role in Septic Shock Through the Calcitonin Gene-Related Peptide Receptor.

OBJECTIVES: Clinically, procalcitonin represents the most widely used biomarker of sepsis worldwide with unclear pathophysiologic significance to date. Pharmacologically, procalcitonin was shown to signal through both calcitonin receptor and calcitonin gene-related peptide receptor in vitro, yet the identity of its biologically relevant receptor remains unknown. DESIGN: Prospective randomized animal investigations and in vitro human blood studies. SETTING: Research laboratory of a university hospital. SUBJECTS: C57BL/6J mice and patients with post-traumatic sepsis. INTERVENTIONS: Procalcitonin-deficient mice were used to decipher a potential mediator role in experimental septic shock and identify the relevant receptor for procalcitonin. Cecal ligation and puncture and endotoxemia models were employed to investigate septic shock. Disease progression was evaluated through survival analysis, histology, proteome profiling, gene expression, and flow cytometry. Mechanistic studies were performed with cultured macrophages, dendritic cells, and gamma delta T cells. Main findings were confirmed in serum samples of patients with post-traumatic sepsis. MEASUREMENTS AND MAIN RESULTS: Procalcitonin-deficient mice are protected from septic shock and show decreased pulmonary inflammation. Mechanistically, procalcitonin potentiates proinflammatory cytokine expression in innate immune cells, required for interleukin-17A expression in gamma delta T cells. In patients with post-traumatic sepsis, procalcitonin positively correlates with systemic interleukin-17A levels. In mice with endotoxemia, immunoneutralization of interleukin-17A inhibits the deleterious effect of procalcitonin on disease outcome. Although calcitonin receptor expression is irrelevant for disease progression, the nonpeptide calcitonin gene-related peptide receptor antagonist olcegepant, a prototype of currently introduced antimigraine drugs, inhibits procalcitonin signaling and increases survival time in septic shock. CONCLUSIONS: Our experimental data suggest that procalcitonin exerts a moderate but harmful effect on disease progression in experimental septic shock. In addition, the study points towards the calcitonin gene-related peptide receptor as relevant for procalcitonin signaling and suggests a potential therapeutic application for calcitonin gene-related peptide receptor inhibitors in sepsis, which warrants further clinical investigation.