pH regulating therapy for hepatocellular carcinoma

细胞内pH值（pHi）的测量显示，实体瘤和正常组织之间的平均pHi（几乎7.2）没有显著差异。两个膜离子泵（N+/H+反向转运和Na+依赖的HCO 3-/Cl-交换）参与了pHi的调节。本研究旨在阐明抑制剂对两种离子交换剂的抗肿瘤作用。选择人肝细胞癌（HCC）作为靶肿瘤，因为肿瘤的细胞外pH（pHe）通过经导管动脉栓塞术（TAE）具有更酸性的潜力，TAE是HCC的最有效的治疗方法之一。在使用人HCC细胞系的体外试验中，与pHe 7.2相比，在pHe 6.6下暴露于EIPA：5-（N-乙基-N-异丙基）阿米洛利（N+/H+反向转运的抑制剂）和DIDS：4，4-二异硫氰基二苯乙烯2，2-二磺酸（Na+依赖性HCO 3-/Cl-交换的抑制剂）引起100倍的细胞杀伤。在低氧条件下，细胞毒作用增强约10倍。使用左后腿携带人HCC肿瘤的裸鼠进行的体内测定中，以未发生动物死亡的最大剂量施用这些抑制剂导致肿瘤大小显著减小，并具有大量坏死区域。来自用抑制剂处理的肿瘤的非坏死组织的细胞在体外培养，并且与它们的野生型细胞相比显示出对pH调节疗法的耐受性。由于技术问题，未能在小动物肝脏上建立HCC模型，因此尚未估计这些pH调节疗法和TAE的联合作用。

Measurements of intracellular pH (pHi) have shown no significant difference in mean pHi (almost 7.2) between solid tumors and normal tissues. Two membranous ion pumps (N+/H+ antiport and Na+- dependentHCO3-/Cl- exchanger) contribute to the regulation of pHi. This study was planned to clarify the anti-tumor effect of inhibiting agents against the two ion exchangers. Human hepatocellular carcinoma (HCC) was selected as a target tumor since the extracellular pH (pHe) of the tumor has potential to be more acidic by transcatheter arterioembolization (TAE) that is one of the most effective therapy for HCC. Under in-vitro assay using human HCC cell lines, Exposure to EIPA : 5-(N-ethyl-N-isopropyl) amiloride (an inhibitor of N+/H+ antiport) and DIDS : 4,4-diisothiocyanstibene 2,2- disulfonic acid (an inhibitor of Na+-dependentHCO3-/Cl- exchanger) at pHe 6.6 caused 100-fold cell killing compared with pHe 7.2. The cytotoxicity was enhanced about 10-fold under the hypoxic condition. In vivo assay using nude mice bearing human HCC tumors at the left hind leg, the administration of these inhibiting agents at the maximal dose that no animal death occurred led to significant reduction of the tumor size with massive necrotic area. Cells from non-necrotic tissues of the tumor treated with the inhibiting agents were cultured in vitro and showed the tolerance to the pH regulating therapy compared with their wild type cells. The establishment of the HCC models on the liver of small animals was not achieved because of the technical problem, therefore the combination effects of those pH regulating therapy and TAE have not been estimated.