CHARACTERIZATION OF A NOVEL TUMOR-DERIVED CYTOKINE - ENDOTHELIAL-MONOCYTE ACTIVATING POLYPEPTIDE-II

Endothelial-monocyte activating polypeptide II (EMAP II) was initially identified in the supernatant of murine methylcholanthrene A-induced fibrosarcomas (Meth A) by its capacity to activate host effector cells (Kao, J., Ryan, J., Brett, J., Chen, J., Shen, H., Fan, Y-G., Godman, G., Familletti, P., Wang, F., Pan, Y-C., Stern, D., and Clauss, M. (1 992) J. Biol. Chem. 267, 20239-20247). Based on the NH2-terminal prote in sequence, a full-length cDNA has been cloned which indicates that t he precursor of EMAP II is a unique, leaderless, single polypeptide ch ain with predicted molecular mass approximate to 34 kDa and that the m ature form released by Meth A cells corresponds to approximate to 20 k Da. Purified recombinant mature EMAP II (EMAP II, approximate to 20 kD a form) activated endothelial cells with resulting elevation of cytoso lic free calcium concentration, release of von Willebrand factor, indu ction of tissue factor, and expression of the adhesion molecules E-sel ectin and P-selectin. Neutrophils exposed to EMAP II demonstrated elev ated cytosolic free calcium concentration, peroxidase generation, and chemotaxis. EMAP II also activated mononuclear phagocytes elevating cy tosolic free calcium concentration, inducing tumor necrosis factor-alp ha (TNF) and tissue factor, and stimulating chemotaxis. Systemic infus ion of EMAP II into C3H/HeJ or Balb/c mice was associated with systemi c toxicity, pulmonary congestion, and the appearance of TNF, interleuk in-1 and -6 in the plasma. A single intratumor injection of EMAP II in to Meth A sarcomas induced acute thrombohemorrhage and partial tumor r egression. Local injection of EMAP II into a tumor resistant to the ef fects of TNF murine mammary carcinoma, rendered it sensitive to subseq uently administered TNF, which resulted in acute thrombohemorrhage and partial regression. These data suggest that recombinant EMAP II, a tu mor-derived cytokine, has properties of a proinflammatory mediator wit h the capacity to prime the tumor vasculature for a locally destructiv e process.