Reinheckel Thomas, Peters Christoph, Krüger Achim, Turk Boris, Vasiljeva Olga
Institute of Molecular Medicine and Cell Research, Albert-Ludwigs-University Freiburg Freiburg, Germany.
Front Pharmacol. 2012 Jul 11;3:133. doi: 10.3389/fphar.2012.00133. eCollection 2012.
Lysosomal cysteine cathepsins belong to a family of 11 human proteolytic enzymes. Some of them correlate with progression in a variety of cancers and therefore are considered as potential therapeutic targets. Until recently, the contribution of individual cathepsins to tumorigenesis and tumor progression remained unknown. By crossing various types of mouse cancer models with mice where specific cathepsins have been ablated, we contributed to this gap of knowledge and will summarize the results in this report. The employed models are the Rip1-Tag2 model for pancreatic neuroendocrine tumors, the K14-HPV16 model for squamous skin and cervical cancers, and the MMTV-PyMT model for metastasizing breast cancer, the KPC model for pancreatic ductal adenocarcinoma, and the APC(min) mice developing early stages of intestinal neoplasia. All models harbor mutations in relevant tumor suppressors and/or cell-type specific expression of potent oncogenes, which initiate de novo carcinogenesis in the targeted tissues. In all these models deletion of cathepsin B led to suppression of the aggressiveness of the respective cancer phenotype. Cathepsin B is networking with other proteases as it was shown for cathepsin X/Z. In contrast, deletion of cathepsin L was beneficial in the RiP1-Tag2 model, but enhanced tumorigenesis in the APC(min), and the K14-HPV16 mice. A logical consequence of these results would be to further pursue selective inhibition of cathepsin B. Moreover, it became clear that cathepsins B and S derived from cells of the tumor microenvironment support cancer growth. Strikingly, delivery of broad spectrum cysteine cathepsin inhibitors in the tumor microenvironment disrupts the permissive ecosystem of the cancer and results in impaired growth or even in regression of the tumor. In addition, combination of cysteine cathepsin inhibition and standard chemotherapy improves the therapeutic response of the latter. Taken together, the next preclinical challenges for developing cathepsin inhibition as cancer therapy might be the improvement of inhibitor selectivity and targeted delivery to the tumor microenvironment and investigation of the biological context of the individual factors within the complex proteolytic network.
溶酶体半胱氨酸组织蛋白酶属于一个由11种人类蛋白水解酶组成的家族。其中一些与多种癌症的进展相关，因此被视为潜在的治疗靶点。直到最近，单个组织蛋白酶对肿瘤发生和肿瘤进展的作用仍不清楚。通过将各种类型的小鼠癌症模型与特定组织蛋白酶已被敲除的小鼠进行杂交，我们填补了这一知识空白，并将在本报告中总结结果。所采用的模型包括用于胰腺神经内分泌肿瘤的Rip1-Tag2模型、用于鳞状皮肤癌和宫颈癌的K14-HPV16模型、用于转移性乳腺癌的MMTV-PyMT模型、用于胰腺导管腺癌的KPC模型以及用于发展肠道肿瘤早期阶段的APC(min)小鼠。所有模型在相关肿瘤抑制因子中都存在突变和/或强效癌基因的细胞类型特异性表达，这些在靶向组织中引发了从头致癌作用。在所有这些模型中，组织蛋白酶B的缺失导致相应癌症表型的侵袭性受到抑制。组织蛋白酶B与其他蛋白酶相互作用，就像组织蛋白酶X/Z的情况一样。相比之下，组织蛋白酶L的缺失在RiP1-Tag2模型中是有益的，但在APC(min)和K14-HPV16小鼠中增强了肿瘤发生。这些结果的一个合理推论是进一步寻求对组织蛋白酶B的选择性抑制。此外，很明显，源自肿瘤微环境细胞的组织蛋白酶B和S支持癌症生长。引人注目的是，在肿瘤微环境中递送广谱半胱氨酸组织蛋白酶抑制剂会破坏癌症的允许生态系统，并导致肿瘤生长受损甚至消退。此外，半胱氨酸组织蛋白酶抑制与标准化疗的联合改善了后者的治疗反应。综上所述，将组织蛋白酶抑制开发为癌症治疗的下一个临床前挑战可能是提高抑制剂的选择性和靶向递送至肿瘤微环境，以及研究复杂蛋白水解网络中各个因素的生物学背景。
