The influence of tumour resection on angiostatin levels and tumour growth - an experimental study in tumour-bearing mice

The phenomenon of primary neoplasms inhibiting the growth of their metastat ic lesions is thought to be related to endogenous angiogenesis inhibitors. The aim of this experiment was to investigate the influence of tumour resec tion on angiostatin levels and tumour growth using a tumour-bearing mouse m odel. A primary Lewis lung cancer tumour model was established in C57BL/6 m ice and these mice were divided into two groups 10 days after the tumour ce lls were inoculated. In the surgical resection group (S group) the tumour w as resected, but in the control group (C group) a sham operation was perfor med. The level of angiostatin in the sera was analysed 5 days after the ope ration by western blotting. To observe tumour growth, four Lewis lung cance r models were established in these mice from both the S and C groups. An im munohistochemical analysis of the tumour tissues was conducted to estimate the proliferation and apoptotic rates of the tumour cells, as well as the a mount of neoangiogenesis in the tumours. Angiostatin was observed in the tu mour-bearing mice, but disappeared within 5 days after the tumour had been resected. Increased tumour growth was observed in all of the tumour models in the S group compared with the C group and the differences were significa nt. A significantly higher intratumour vessel density and proliferation cel l index, but a significantly lower apoptotic index were also found in the S group compared with the C group. These findings demonstrated that angiosta tin was generated directly from the tumour tissue. Furthermore, tumour rese ction accelerates the growth of other tumours and this is probably related to multiple factors including increased neoangiogenesis, increased tumour c ell proliferation, and decreased apoptosis. (C) 2001 Elsevier Science Ltd. All rights reserved.