Luo C, MacPhail S H, Dougherty G J, Naus C C, Olive P L
Medical Biophysics Department, British Columbia Cancer Research Centre, Vancouver, Canada.
Exp Cell Res. 1997 Aug 1;234(2):225-32. doi: 10.1006/excr.1997.3613.
Some cell lines grown for only two cell doublings as multicell spheroids develop a form of resistance to killing by ionizing radiation that has been called the "contact" effect. While our previous results have implicated a role for higher order chromatin structure in the contact effect, another possible explanation is the presence of intercellular gap junctions that might facilitate communication between cells grown as spheroids and thereby enhance the ability of cells to resist or recover from radiation damage. To examine the role of gap junctions in the contact effect, rat glioma C6 and mouse EMT6 cell lines were transfected with a gene encoding the gap junctional protein connexin43. While C6 glioma cells are deficient in gap junctional communication, cells from spheroids were nonetheless more resistant than monolayers to killing by ionizing radiation, and the contact effect was present to a similar extent in the three transfected clones. For mouse EMT6 cells, radiosensitivity was similar whether cells were grown as monolayers or spheroids. Transfection of EMT6 cells with connexin43 increased gap junctional communication but did not promote development of a contact effect. Tumor volume doubling time in SCID mice increased significantly for one transfected clone; however, doubling time in vitro was also increased relative to the EMT6 parent. We conclude that extensive gap junctional communication is not a requirement for the increased radiation resistance observed when some cell lines are grown as spheroids.
一些仅经过两次细胞倍增培养形成多细胞球体的细胞系，会产生一种对电离辐射杀伤的抗性形式，这种抗性被称为“接触”效应。虽然我们之前的结果表明高阶染色质结构在接触效应中起作用，但另一种可能的解释是存在细胞间缝隙连接，它可能促进作为球体生长的细胞之间的通讯，从而增强细胞抵抗辐射损伤或从辐射损伤中恢复的能力。为了研究缝隙连接在接触效应中的作用，用编码缝隙连接蛋白连接蛋白43的基因转染大鼠胶质瘤C6细胞系和小鼠EMT6细胞系。虽然C6胶质瘤细胞缺乏缝隙连接通讯，但来自球体的细胞比单层细胞对电离辐射杀伤更具抗性，并且在三个转染克隆中接触效应的程度相似。对于小鼠EMT6细胞，无论细胞是作为单层还是球体生长，放射敏感性都相似。用连接蛋白43转染EMT6细胞增加了缝隙连接通讯，但没有促进接触效应的发展。一个转染克隆在SCID小鼠中的肿瘤体积倍增时间显著增加；然而，相对于EMT6亲本，体外倍增时间也增加了。我们得出结论，当一些细胞系作为球体生长时观察到的辐射抗性增加并不需要广泛的缝隙连接通讯。
