低剂量/预给药条件下化疗药物显现促肿瘤生长转移作用的机制研究

Evidences have shown that parts of the chemotherapy drugs, such as cyclophosphamide, cisplatinum and paclitaxel, could provoke tumor growth and metastasis under certain conditions. However, the mechanisms are not clear yet. It was reported recently that these chemotherapy drugs could stimulate the founctions of endothelial cells at low concentration, and/or enhance the release and recruitment of bone marrow-derived cells. Based on our previous studies, we speculate that some chemotherapy drugs, in addition to their cytotoxicities, also promote angiogenesis in tumor tissues through direct or indirect activities mentioned above. As a result, chemotherapy drugs may present an opposite effect on tumor growth and metastasis owning to the differences in the threshold concentrations and the response times between cytotoxic and proangiogenic activities. To verify the hypothesis, murine tumors such as Lewis lung cancer, melanoma B16 and sarcoma S180, as well as representative antitumor drugs will be employed to observe the effects of chemotherapy agents on cancer cells, endothelia cells and tumor growth over a wide dose range in vitro and in vivo. Experimental techniques or methods, such as macrophage/platelets depletion, bone marrow transplantation, flow cytometer, immune inhibition and immunofluorescence will be utilized to investigate the effect of chemotherapy drugs on BMDCs release and recruitment, and to explore the pathways and mechanisms of chemotherapy drugs in promoting tumor growth. Data from these studies will provide necessary basic research references for the design of tumor treatment plan in clinic and for the selection of chemotherapy drugs in combination application for chemotherapy treatment.

研究显示，有些化疗药物如环磷酰胺、顺铂和紫杉醇等在低剂量或预给药条件下可促进肿瘤的生长和转移，但机制不明。近期发现该类化疗药物能增加骨髓源性细胞的释放和招募,或在低浓度下增强血管内皮细胞的功能。结合前期研究我们推测，化疗药物在其细胞毒作用之外，还能通过上述作用促进肿瘤血管新生；当药物发挥细胞毒与促肿瘤血管新生两方面作用的时机不同步或阈浓度之间存在差异时，就有可能出现促肿瘤生长和转移的异常作用。为验证该假设，本研究拟以上述代表性化疗药物为研究对象，在较大剂量范围或不同时机给药，系统观察对小鼠Lewis肺癌等实体肿瘤生长转移以及对肿瘤细胞和内皮细胞功能的影响；采用体内细胞删除、骨髓移植、流式细胞技术、免疫荧光等实验技术，探讨药物促进肿瘤生长转移的主要作用途径，考察药物对骨髓源性细胞释放和招募以及对肿瘤血管新生的影响，分析药物促进肿瘤生长转移的机制。本课题研究结果可为化疗药物的临床应用提供参考。

研究显示，有些化疗药物如环磷酰胺、顺铂和紫杉醇等在低剂量或预给药条件下可促进肿瘤的生长和转移，但机制不明。近期发现该类化疗药物能增加骨髓源性细胞的释放和招募,或在低浓度下增强血管内皮细胞的功能。结合前期研究我们推测，化疗药物在其细胞毒作用之外，还能通过上述作用促进肿瘤血管新生。为验证该假设，本研究通过代表性化疗药物为研究对象，在较大剂量范围或不同时机给药，系统观察对小鼠不同实体肿瘤生长转移以及对肿瘤细胞和内皮细胞功能的影响；采用骨髓移植、流式细胞技术、免疫荧光等实验技术，探讨药物促进肿瘤生长转移的主要作用途径，考察药物对BMDCs释放和招募以及对肿瘤血管新生的影响，分析药物促进肿瘤生长转移的机制。实验结果显示，化疗药物如CTX、5-FU、CDDP在预给药的情况下可以促进肿瘤生长和血管新生的作用；CTX、5-FU、CDDP可促进促血管新生BMDCs如αvβ3+ BMDCs、VEGFR2+ BMDCs及Gr-1+ CD11b+ BMDCs的动员，同时亦能促进肿瘤组织对BMDCs的招募与驻留；CTX、5-FU、CDDP可通过刺激BMDCs促进内皮细胞和肿瘤细胞的增殖；CTX、5-FU、CDDP可上调VEGFR2、αvβ3转录水平。小剂量多次给药条件下，CTX或5-Fu能够促进肿瘤生长和血管新生；小剂量CTX可促进αvβ3+ BMDCs、VEGFR2+ BMDCs及Gr-1+ CD11b+ BMDCs的动员，同时亦能促进肿瘤组织对BMDCs的招募与驻留；小剂量CTX可上调肿瘤组织中MMP-9和VEGFR2转录及翻译水平，同时可促进一系列促血管新生和促肿瘤生长因子的表达，亦有抑制肿瘤生长的细胞因子下调；免疫抑制作用可能并不是小剂量CTX促进肿瘤生长作用中的主导因素。小剂量5-FU可促进小鼠B16黑色素瘤和Lewis肺癌的转移，刺激肿瘤血管新生；小剂量5-FU虽可直接抑制肿瘤细胞增殖，抑制内皮细胞的增殖与粘附，但在BMDCs存在下，小剂量5-FU可明显促进肿瘤细胞的增殖、刺激肿瘤细胞的迁移和侵袭，同时可促进了内皮细胞的增殖和对BMDCs的粘附作用；小剂量5-FU刺激B16肿瘤细胞促进MMP-9 mRNA的转录水平促进肿瘤细胞的侵袭能力；小剂量5-FU促进β3+BMDCs动员和释放，促进肿瘤血管新生；增强内皮细胞β3的转录水平，进而增加肿瘤组织对BMDCs的招募。