De Milito Angelo, Iessi Elisabetta, Logozzi Mariantonia, Lozupone Francesco, Spada Massimo, Marino Maria Lucia, Federici Cristina, Perdicchio Maurizio, Matarrese Paola, Lugini Luana, Nilsson Anna, Fais Stefano
Department of Drug Research and Evaluation, Pharmacogenetic, Drug Resistance, and Experimental Therapeutic Section, Istituto Superiore di Sanità, Rome, Italy.
Cancer Res. 2007 Jun 1;67(11):5408-17. doi: 10.1158/0008-5472.CAN-06-4095.
Proton pumps like the vacuolar-type H+ ATPase (V-ATPase) are involved in the control of cellular pH in normal and tumor cells. Treatment with proton pump inhibitors (PPI) induces sensitization of cancer cells to chemotherapeutics via modifications of cellular pH gradients. It is also known that low pH is the most suitable condition for a full PPI activation. Here, we tested whether PPI treatment in unbuffered culture conditions could affect survival and proliferation of human B-cell tumors. First, we showed that PPI treatment increased the sensitivity to vinblastine of a pre-B acute lymphoblastic leukemia (ALL) cell line. PPI, per se, induced a dose-dependent inhibition of proliferation of tumor B cells, which was associated with a dose- and time-dependent apoptotic-like cytotoxicity in B-cell lines and leukemic cells from patients with pre-B ALL. The effect of PPI was mediated by a very early production of reactive oxygen species (ROS), that preceded alkalinization of lysosomal pH, lysosomal membrane permeabilization, and cytosol acidification, suggesting an early destabilization of the acidic vesicular compartment. Lysosomal alterations were followed by mitochondrial membrane depolarization, release of cytochrome c, chromatin condensation, and caspase activation. However, inhibition of caspase activity did not affect PPI-induced cell death, whereas specific inhibition of ROS by an antioxidant (N-acetylcysteine) significantly delayed cell death and protected both lysosomal and mitochondrial membranes. The proapoptotic activity of PPI was consistent with a clear inhibition of tumor growth following PPI treatment of B-cell lymphoma in severe combined immunodeficient mice. This study further supports the importance of acidity and pH gradients in tumor cell homeostasis and suggests new therapeutic approaches for human B-cell tumors based on PPI.
像液泡型H⁺ ATP酶（V-ATP酶）这样的质子泵参与正常细胞和肿瘤细胞的细胞内pH调控。用质子泵抑制剂（PPI）治疗可通过改变细胞pH梯度诱导癌细胞对化疗药物敏感。还已知低pH是PPI完全激活的最适宜条件。在此，我们测试了在无缓冲培养条件下进行PPI治疗是否会影响人B细胞肿瘤的存活和增殖。首先，我们表明PPI治疗增加了前B急性淋巴细胞白血病（ALL）细胞系对长春碱的敏感性。PPI本身可诱导肿瘤B细胞增殖的剂量依赖性抑制，这与B细胞系和前B ALL患者白血病细胞中剂量和时间依赖性的凋亡样细胞毒性相关。PPI的作用是由活性氧（ROS）的极早期产生介导的，这先于溶酶体pH碱化、溶酶体膜通透性增加和胞质酸化，提示酸性囊泡区室的早期不稳定。溶酶体改变之后是线粒体膜去极化、细胞色素c释放、染色质凝聚和半胱天冬酶激活。然而，抑制半胱天冬酶活性并不影响PPI诱导的细胞死亡，而抗氧化剂（N-乙酰半胱氨酸）对ROS的特异性抑制显著延迟了细胞死亡并保护了溶酶体和线粒体膜。PPI的促凋亡活性与在严重联合免疫缺陷小鼠中用PPI治疗B细胞淋巴瘤后肿瘤生长的明显抑制一致。这项研究进一步支持了酸度和pH梯度在肿瘤细胞内稳态中的重要性，并提出了基于PPI的人B细胞肿瘤新治疗方法。
