Piroxicam, indomethacin and aspirin action on a murine fibrosarcoma. Effects on tumour-associated and peritoneal macrophages.

Growth of a methylcholanthrene-induced fibrosarcoma in BALB/c mice was accompanied by an increase in the activation state of tumour-associated macrophages (TAM), as measured by their FcIgG receptor expression, phagocytic index and beta-glucuronidase levels. All of these parameters were markedly higher in TAM than in peritoneal macrophages (PM) derived from the same animal. On the other hand, PM from tumour-bearing mice showed lower activation parameters than PM from normal animals. We also studied the effect on tumour development of three inhibitors of prostaglandin synthesis: indomethacin, piroxicam and aspirin. Intraperitoneal administration of these drugs during 8 d was followed by the regression of palpable tumours. Indomethacin (90 mg/d) induced 45% regression, while with piroxicam (two 400 mg/d doses and six 200 mg/d doses) and aspirin (1 mg/d) 32% and 30% regressions, respectively, were observed. The growth rate of nonregressing tumours, which had reached different volumes by the end of the treatment, was delayed to a similar extent by the three anti-inflammatory non-steroidal drugs (NSAID). With respect to TAM, the treatment did not induce any significant change in their activation state, though both piroxicam and indomethacin increased slightly the TAM number. In contrast, NSAID administration was followed by a remarkable increase in the activation parameters of PM when compared with PM from tumour-bearing mice receiving no treatment. Indeed, these parameters were in some cases higher than those of PM from normal mice. The leukocytosis (60,000/microliters) with neutrophilia (80%) induced by tumour growth on peripheral blood leukocytes (PBL) was reversed by the treatment to values close to normal, in parallel with the reduction of tumour size. A drop in haematocrit was also noted which was most probably a consequence of tumour growth rather than of the treatment. This study reveals that the three NSAID tested have a remarkable antitumour activity, which correlates with the restoration of PM activity and PBL values.