Abstract
The aim of this research was to establish an artificial metastatic model to study the influence of pre-irradiation (6 MV X-ray) of thorax on the process of metastasis in lung. C3H/HeN mice were injected i.v. with 1x10E5 NFsa cells/mouse, sacrificed at the 8th day after injection. The number of lung colony at lung surface was counted. For irradiated group, the mice’ thorax was irradiated 20 Gy X-ray and injected i.v. NFsa tumors cells immediately after irradiation. In 8 repeated experiments, the ratio of the number of lung colonies at surface between irradiated group and non-irradiated group was 3.18±1.26 (p = 0.02). In lung sections, the number of metastatic tumors per normal lung area and the ratio between total tumor area and total normal lung area in irradiated group were both higher than those of the non-irradiated. The ratios were similar to that we observed in the number of lung colonies at lung surface. To evaluate if pre-irradiation promote the growth rate of tumor, the lung section was stained with H&E and the distribution of the size of lung tumor was calculated. We observed that irradiated group had more potential to get bigger tumors than those of non-irradiated group. To evaluate the dose-response, we gave the grading radiation doses including 0 Gy, 6 Gy, 12 Gy and 20 Gy. The results showed that even at lower dose of 6 Gy, the formation of lung colony was still promoted by the pre-irradiation of thorax but the effect was less obvious than that at 20 Gy. To evaluate if the promotion of tumor is time-dependent, we injected NFsa tumor cells at various time after irradiation. Immediately or at the first day after irradiation of thorax, we found both can promote metastasis in lung. When the time interval between irradiation and injection of tumor cells became longer; the ability of metastasis was lower and no significant increase of lung metastasis was found if time interval was up to 1 month. Finally, we found that aspirin cannot inhibit the promotion of metastasis induced by pre-irradiation of thorax.