COX2 inhibitors reduce TNF-α expression and attenuate cachexia in human renal cell cancer xenografts

4668 The paraneoplastic wasting syndrome, known as cancer cachexia, is mediated by complex interactions of proinflammatory cytokines and catabolic factors and appears to be partly communicated by prostanoids. Tumor necrosis factor-a (TNF-α) and the cyclooxygenase 2 (COX2) product prostaglandin E2 (PGE2) however, seem to be the most important mediators in that TNF-α antibodies and COX2 inhibitors have been shown to effectively attenuate cachexia. This study was aimed to examine whether COX2 inhibition and TNF-α expression are related and can be causally linked in well characterized cachexia models of human cancer. The Freiburg human tumor xenograft panel comprises a collection of 400 patient explants growing s.c. in nude mice. Ten %, mainly cancers of the kidney, lung, pancreas, and cervix uteri were found to induce cachexia. Here, 5 renal cell cancer (RCC) xenografts and cell lines derived thereof which show (RXF 393, RXF 486, RXF 1220) or lack (RXF 631, RXF 944LX) the cachectic phenotype were used. RCC xenografts were transplanted s.c. into nude mice and grown until a body weight loss of 20% or tumor burden of 1.5 g occurred. Tumor tissue, and plasma were collected as well as 24h conditioned media from 106 exponentially growing cell lines. Body weight and tumor volume, were recorded daily. Cytokine levels (IL-1, IL-6, TNF-α) were determined by ELISA assays specific for human proteins. COX2 activity was analyzed by PGE2 ELISA, and COX2 immunoperoxidase staining (IHC) in tissues. IL-1 levels were found elevated in media of RXF 393 (47 pg/106 cells) and RXF 486 (65 pg/106 cells), but were negative for RXF 1220, RXF 631 and RXF 944LX . IL-6 was high in all RCC with concentrations around 8,5 ng/106 cells. High TNF-α was detectable only in media of cachectogenic tumors (58-220 pg/ml), but was absent in RXF 944LX and RXF 631 (0 pg/ml). The measurement of PGE2 yielded similar results: 962 pg/ml were found in media of RXF 486 and 5.7 pg/ml for RXF 631. IHC for COX2 revealed strong cytoplasmic expression in tissue from cachectic mice versus very weak in non-cachectogenic tumors. Treatment of RCC with COX2 inhibitors rofecoxib (12,5 mg/kg/d p.o.) and nimesulide (5 mg/kg/d p.o.) resulted in a delay of onset of body weight loss for 5-12 days despite progressive tumor growth. TNF-α was markedly reduced in tumor lysates from treated mice at maximum effects. RXF 393 controls expressed 8.7 pg TNF-α /μg protein, rofecoxib 2.5 and nimesulide treated tissue contained 2 pg/μg TNF-α. Accordingly, PGE2 production was inhibited by both, rofecoxib and nimesulide in cultures of cachectic tumors (IC50 at 24 hr = 100 μM). Our data indicate that TNF-α is the only discriminative cytokine in cachexia and that its overexpression is paralleled by COX2 activity in RCC. COX2 inhibition can modulate the cascade of proinflammatory cytokines and thus, might provide patients with a therapeutic option for prevention and treatment of the paraneoplastic wasting syndrome.