Centre de Recherche en Cancérologie de l'Université Laval, L'Hôtel-Dieu de Québec, Centre Hospitalier Universitaire de Québec, Qc G1R 2J6, Canada.
Mol Cancer. 2010 Jun 10;9:141. doi: 10.1186/1476-4598-9-141.
Solid tumors are often poorly vascularized, with cells that can be 100 microm away from blood vessels. These distant cells get less oxygen and nutrients and are exposed to lower doses of chemotherapeutic agents. As gap junctions allow the passage of small molecules between cells, we tested the possibility that the chemotherapeutic agent gemcitabine can diffuse through gap junctions in solid tumors.
We first showed with a dye transfer assay that the glioblastoma and the osteosarcoma cells used in this study have functional gap junctions. These cells were genetically engineered to express the herpes simplex virus thymidine kinase (TK), and induced a "bystander effect" as demonstrated by the killing of TK-negative cells in presence of the nucleoside analogue ganciclovir (GCV). The ability of gemcitabine to induce a similar bystander effect was then tested by mixing cells treated with 3 microM gemcitabine for 24 hours with untreated cells at different ratios. In all cell lines tested, bystander cells were killed with ratios containing as low as 5% treated cells, and this toxic effect was reduced in presence of alpha-glycyrrhetinic acid (AGA), a specific gap junction inhibitor. We also showed that a 2- or a 24-hour gemcitabine treatment was more efficient to inhibit the growth of spheroids with functional gap junctions as compared to the same treatment made in presence of AGA. Finally, after a 24-hour gemcitabine treatment, the cell viability in spheroids was reduced by 92% as opposed to 51% in presence of AGA.
These results indicate that gemcitabine-mediated toxicity can diffuse through gap junctions, and they suggest that gemcitabine treatment could be more efficient for treating solid tumors that display gap junctions. The presence of these cellular channels could be used to predict the responsiveness to this nucleoside analogue therapy.
实体肿瘤的血管通常不够丰富，其细胞距离血管可达 100 微米之远。这些远离血管的细胞获得的氧气和营养较少，且接触到的化疗药物剂量也较低。由于间隙连接允许小分子在细胞间传递，我们检验了这样一种可能性，即化疗药物吉西他滨可以通过实体肿瘤中的间隙连接扩散。
我们首先通过染料转移实验表明，本研究中使用的神经胶质瘤和骨肉瘤细胞具有功能性间隙连接。这些细胞经过基因工程改造，表达单纯疱疹病毒胸苷激酶（TK），并在核苷类似物更昔洛韦（GCV）存在的情况下诱导“旁观者效应”，即杀死 TK 阴性细胞。然后，通过将用 3μM 吉西他滨处理 24 小时的细胞与未处理的细胞以不同比例混合，测试吉西他滨诱导类似旁观者效应的能力。在所测试的所有细胞系中，旁观者细胞在含有低至 5%处理细胞的比例下被杀死，而在α-甘草次酸（AGA）存在下，这种毒性作用降低，AGA 是一种特定的间隙连接抑制剂。我们还表明，与在 AGA 存在下进行相同处理相比，2 小时或 24 小时的吉西他滨处理更有效地抑制具有功能性间隙连接的球体的生长。最后，在用吉西他滨处理 24 小时后，与在 AGA 存在下相比，球体中的细胞活力降低了 92%，而不是 51%。
这些结果表明，吉西他滨介导的毒性可以通过间隙连接扩散，并且它们表明，在用吉西他滨治疗显示间隙连接的实体瘤时，治疗可能更有效。这些细胞通道的存在可用于预测对这种核苷类似物治疗的反应性。
