Local Controlled Delivery of Anti-Neoplastic RNAse to the Brain

Purpose  Antineoplastic RNAse proteins, also known as Amphibinases, have been shown effective against various solid tumors but were found selectively neurotoxic to Purkinje cells in the cerebellum. This work describes the use of a waxy biodegradable poly(ricinoleic-co-sebacic acid) for the local controlled delivery of cytotoxic amphibinases in the parietal lobe of the brain in an attempt to overcome cerebellar neuronal toxicity while affecting glioma cells. Methods  Amphibinase analogues were encapsulated in poly(ricinoleic-co-sebacic acid) formulations using mix-melt technology and loaded onto surgical foam. In-vitro release was monitored by BCA colorimetry and by RNAse specific bioactivity. The implants were inserted into rat brains bearing 9L glioma to assess toxicity and efficacy. Results  The various formulations showed extended linear release for several weeks with minimal burst effect. Best in-vivo efficacy was obtained with ACC7201 containing implants, resulting in the extension of the median survival from 13 to 18 days with 13% long-term survivors. Conclusion  Antineoplastic proteins were released from a p(SA-RA) polyanhydride implants in a controlled manner, providing efficacy against 9L glioma, while evading neurotoxicity in the cerebellum. The controlled release of Amphibinases forms the potential for a new therapy against brain tumors.     

Targeted therapeutic RNases (ImmunoRNases)

Immunotoxins combining antibody specificity with bacterial or plant toxins are limited by their strong immunogenicity and non-specific toxicity. Ribonucleases of the RNase A protein superfamily provide a solution to address these issues because they show potent antineoplastic activity on cell internalization but do not show appreciable immunogenicity or non-specific toxicity. Their therapeutic value is demonstrated by RNase derived from the frog (Rana pipiens), Onconase^® (ONC, Alfacell, Inc., New Jersey, USA), the first and only RNase being evaluated in clinical trials at present. Conjugation or fusion of RNases to tumor specific antibodies is a promising approach to further boost tumor cell killing of these compounds. This review focuses on ‘targeted RNases/ImmunoRNases’ as promising novel anticancer therapeutics.     

重组豹蛙酶的制备及其生物学特性分析

目的:通过构建豹蛙酶原核表达载体pColdⅡ－Rap,表达?纯化豹蛙酶并研究其生物学活性?方法:合成豹蛙酶全基因序列,克隆于原核表达载体pColdⅡ中,鉴定正确后转化至大肠杆菌BL21,用SDS－PAGE和Western blot验证豹蛙酶的表达;大量表达重组豹蛙酶融合蛋白(Rap－His),通过MTT法分析Rap－His对乳腺癌细胞增殖的影响?结果:成功构建了pColdⅡ－Rap原核表达载体,经优化表达?纯化的条件,获得纯度较高的Rap－His;MTT法检测结果表明,该融合蛋白在320?160 μg/ml时对乳腺癌细胞MDA－MB－231增殖的抑制率在加药后4 d达到93.49%?结论:本研究制备的重组Rap－His融合蛋白能够抑制乳腺癌细胞MDA－MB－231增殖?这为进一步与肿瘤特异抗体偶联,构建肿瘤特异性靶向药物的研究奠定了基础?