Perfil de citocinas pró- e anti-inflamatória e da proteína c-reativa no tratamento do tumor venéreo transmissível canino

Abstract

The canine transmissible venereal tumor (CTVT) is unique in various aspects, and the principal is that the tumoral cells are not originated from the hos t. Recent findings showed that the CTVT is a transplantable tumor that first appeared in a dog ancestor approximately 10000 years ago. The tumoral cells propagate mainly through coitus, develop a s a graft, and have the capability of installing themselves by mechanisms of escape from the host's immunologic response. This specific response involves cellular and humoral immunity and varies according to some factors not yet very elucidated. Beyond the well-known role of fi ghting the tumor cells, the inflammatory response also plays an involuntary and paradoxical role, w hich results in the promotion of tumor growth by releasing vasculogenic, antiapoptotic, and cellular growth- promoting substances. The fact that tumors can benefit from the inf lammatory response makes the investigation of the mechanisms involved important for the development of new therapies focused on the modulation of the inflammatory response to control the tumor development. The aim of this work is to better understand the mechanisms behind tumora l growth by the measurement of the levels of pro-inflammatory (IL-1, IL-6, TNF- α and INF- γ ) and anti- inflammatory (IL-10) cytokines and the C-reactive protein (CRP) ove r the treatment of dogs naturally infected with CTVT. The quantification of the cytokines and CRP was performed in the animals' serum from samples obtained at the moments of the diagnosis and pre-therapy, immediately before chemotherapy, and after the confirmation of the cure of each animal. According to therapy response, two groups were identified, R, were t he tumor was resistant to therapy and NR, which was susceptible. A cure probability was define d in relation to time of treatment and tumor response to vincristin. In group R all parameter s varied significantly: The expression of pro-inflammatory cytokines and CRP were higher, and of I L-10, lower, comparing to group NR. For pro-inflammatory cytokines, this difference was ma intained until cure. Statistical analysis was able to detect correlations betwee n all variables, demonstrating the participation of cytokines during tumor evolution. The role of inflammati on has been postulated and, although the mechanisms remain unclear, a correlation of chronic i nflammation and cancer susceptibility has been demonstrated. Because CTVT is a tumor of foreign cells, it is a suitable model to investigate the mechanisms involved in tumor maintenance and deve loping, as well as the associated immune response.