Rofstad E K, Danielsen T
Department of Biophysics, Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, Oslo.
Br J Cancer. 1998 Mar;77(6):897-902. doi: 10.1038/bjc.1998.148.
Tumour cells exposed to hypoxia in vitro can show increased expression of several selected genes, including the gene encoding the vascular endothelial growth factor (VEGF), suggesting that hypoxia followed by reoxygenation might promote the malignant progression of tumours. An in vitro/in vivo study was conducted to investigate whether hypoxia can increase the angiogenic potential of tumour cells through increased VEGF secretion. Four human melanoma cell lines (A-07, D-12, R-18, U-25) were included in the study. Cell cultures were exposed to hypoxia (oxygen concentration <10 p.p.m.) in vitro using the steel chamber method. Rate of VEGF secretion was measured in vitro in aerobic and hypoxic cell cultures by ELISA. Angiogenesis was assessed in vivo using the intradermal angiogenesis assay. Aliquots of cells harvested from aerobic cultures or cultures exposed to hypoxia for 24 h were inoculated intradermally in the flanks of adult female BALB/c-nu/nu mice. Tumours developed and angiogenesis was quantified by scoring the number of capillaries in the dermis oriented towards the tumours. The number of tumour-oriented capillaries did not differ significantly between tumours from hypoxic and aerobic cultures for A-07 and U-25, whereas tumours from hypoxic cultures showed a larger number of tumour-oriented capillaries than tumours from aerobic cultures for D-12 and R-18. The VEGF secretion under aerobic conditions and the absolute increase in VEGF secretion induced by hypoxia were lower for D-12 and R-18 than for A-07 and U-25, whereas the relative increase in VEGF secretion induced by hypoxia was higher for D-12 and R-18 than for A-07 and U-25. VEGF is not a limiting factor in the angiogenesis of some tumours under normoxic conditions. Hypoxia can increase the angiogenic potential of tumour cells by increasing the secretion of VEGF, but only of tumour cells showing low VEGF secretion under normoxia. Transient hypoxia might promote the malignant progression of tumours by temporarily increasing the angiogenic potential of tumour cells showing low VEGF expression under normoxic conditions.
体外暴露于缺氧环境的肿瘤细胞可表现出几种特定基因的表达增加，包括编码血管内皮生长因子（VEGF）的基因，这表明缺氧后再给氧可能促进肿瘤的恶性进展。开展了一项体外/体内研究，以调查缺氧是否可通过增加VEGF分泌来提高肿瘤细胞的血管生成潜力。该研究纳入了四个人类黑色素瘤细胞系（A - 07、D - 12、R - 18、U - 25）。使用钢箱法在体外使细胞培养物暴露于缺氧环境（氧气浓度<10 ppm）。通过ELISA在需氧和缺氧细胞培养物中体外测量VEGF分泌率。使用皮内血管生成试验在体内评估血管生成。从需氧培养物或暴露于缺氧环境24小时的培养物中收获的细胞等分试样皮内接种于成年雌性BALB/c - nu/nu小鼠的侧腹。待肿瘤形成后，通过对朝向肿瘤的真皮内毛细血管数量进行评分来量化血管生成。对于A - 07和U - 25，缺氧培养物和需氧培养物来源的肿瘤中朝向肿瘤的毛细血管数量无显著差异，而对于D - 12和R - 18，缺氧培养物来源的肿瘤比需氧培养物来源的肿瘤显示出更多朝向肿瘤的毛细血管。D - 12和R - 18在需氧条件下的VEGF分泌以及缺氧诱导的VEGF分泌绝对增加量低于A - 07和U - 25，而缺氧诱导的VEGF分泌相对增加量D - 12和R - 18高于A - 07和U - 25。在常氧条件下，VEGF不是某些肿瘤血管生成的限制因素。缺氧可通过增加VEGF分泌来提高肿瘤细胞的血管生成潜力，但仅针对在常氧下VEGF分泌较低的肿瘤细胞。短暂缺氧可能通过暂时增加在常氧条件下VEGF表达较低的肿瘤细胞的血管生成潜力来促进肿瘤的恶性进展。
