ARGININE DEIMINASE AS AN ANTI-CANCER THERAPY

肝细胞癌、恶性黑色素瘤和某些肉瘤对精氨酸的独特需求为潜在的新型化疗提供了基础。精氨酸脱亚胺酶（ADI）可使血清精氨酸耗竭；此外，聚乙二醇（PEG）在ADI上的共价附着显著延长了这种耗竭的持续时间。初步研究表明，PEG-ADI治疗可提高肉瘤、肝癌或黑色素瘤小鼠的存活率。当更大的PEG与ADI连接时，PEG-ADI的抗肿瘤效果增强。因此，本提案的目标是确定高效的ADI的PEG修饰，从而为开发用于治疗恶性黑色素瘤和肝细胞癌的PEG-ADI疗法提供基础。为了确定最佳的ADI修饰，将5 - 100 kDa的线性peg和支链peg偶联到ADI上，并确定peg -ADI的具体活性。将评估peg -ADI在消耗血清精氨酸、降低ADI免疫原性和提高肉瘤小鼠存活率方面的体内有效性。然后在人肝癌和黑色素瘤小鼠中评价三种最有希望的PEG-ADIs的抗肿瘤效果。拟议的商业应用：拟议的研究可能导致开发一种安全有效的治疗方法来对抗恶性黑色素瘤（3期）和肝细胞癌。目前还没有有效的治疗这些肿瘤的方法，迫切需要。此外，可能存在其他肿瘤亚群，它们表现出精氨酸依赖，因此可能是PEG-ADI治疗的候选者。

The distinctive arginine requirement of hepatocellular carcinomas, malignant melanomas and some sarcomas provides the basis for a new potential chemotherapy. The enzyme arginine deiminase (ADI) can deplete serum arginine; moreover, the duration of this depletion is significantly extended by covalent attachment of polyethylene glycol (PEG) to ADI. Preliminary studies indicate that PEG-ADI treatment increases the survival of mice bearing sarcomas, hepatomas or melanomas. The anti-tumor efficacy of PEG-ADI was enhanced when a larger PEG was linked to ADI. Thus, the goals of this proposal are to identify highly efficacious PEG modifications of ADI, and thereby provide a foundation for the development of a PEG-ADI therapy in the treatment of malignant melanomas and hepatocellular carcinomas. In order to identify such optimal ADI modifications, linear PEGs, from 5 to 100 kDa, and branched PEGs will be coupled to ADI and the specific activities of the PEG-ADIs will be determined. The in vivo effectiveness of the PEG-ADIs, in depleting serum arginine, reducing ADI immunogenicity and increasing the survival of sarcoma bearing mice will be assessed. Then the anti-tumor efficacy of the three most promising PEG-ADIs will be evaluated in mice bearing human hepatomas and melanomas. PROPOSED COMMERCIAL APPLICATIONS: The proposed studies could lead to the development of a safe and effective therapy to combat malignant melanoma (stage 3) and hepatocellular carcinoma. Effective treatments for these neoplasias are currently not available and are urgently needed. In addition, there may be subsets of other neoplasias, which exhibit an arginine dependence, and hence might be candidates for PEG-ADI treatment.