Cloning, Expression And Determination The Human Carboxypeptidase A1 And Active Center Gene

Most drugs for chemotherapy lack selective specificity to malignant cells in cancer treatment, which usually brings damage to normal tissues while targeting on tumor cells instantaneously because of cytotoxicity. So in recent years one of the most important research topics on tumor chemotherapy is to build directed high selective specificity target treatment system. But scholars are not satisfied with its anti-tumor outcome. The direction chemotherapy strategy for tumor can avoid the side effects in theory but the result is far from expectation with the research development, because many toxic drugs conjugated with antibody protocols couldn't play the therapeutic efficacy fully in vivo test for clinic application. The conjugated drugs can not reach the malignant tissue to produce an efficiently effect of anti-tumor owing to the following possible reasons:(1)the quantity limitation caused by the antibody binding capacity that necessary for the toxic drug molecules attachment; (2)the big conjugation consisted of antibody and toxic drug can hardly reach the solid tumor location efficiently; (3)The conjugation consisted of antibody and toxic drug, which formmacromolecules in administration, has immunogenicity for complicated immune reaction which impose negative impact on the treatment effect in clinic application.Antibody-directed enzyme prodrug therapy (ADEPT) is one of the noticeable new progresses in the research of antibody-directed treatment for tumor in recent years. The prodrug, a kind of substances has no or only lower activity, can be converted into activated drug when catalyzed in vivo. The antibody, as the vector to carry the specific activating enzyme to catalyze the prodrug, can selectively conjugate to the target malignant tissue at the same time. Then the prodrug can be activated by the enzyme, which is carried by the antibody just mentioned above, and converted into activated cytotoxitic molecules located at a certain region in the tumor tissue to play the cytotoxitic effect on the malignant cells and kill them only ultimately. According to some literature reports one carboxypeptidase G2 (carboxypeptidase G2, CPG2) molecule can degradation 800 substrate molecules named acidum benzoicum mustine just in one second and give a magnifying consequence in order to try to locate the activated drug on the target cell, thus make up the low capability of the immunologic conjugation and kill the malignant cells efficiently in clinic application.ADEPT strategy, initially put up by Philpott, then improved by Bagshawe and Senter further, has been attracting more and more scientists from all over the world to keep on research into it since 1987. Now both foreign and domestic researchers in this field are on the way to make it flawless. The research on CPG2 system for carcinoma of colon treatment, now in phase II clinic experiment, shows a nice prospect for therapy effect and application in clinic. Other ADEPT protocols such as penicillin amidase system, cytosine deaminase system and beta-glucuronidase system are on the list of producing and consummating.Prostate cancer, one of the most prevalent malignant tumors in older males, takes the first place for American old man on the list of male tumor incidence rate. The incidence rate has been increasing year by year with the change of average life span and dietary structure in China. Except operation, there is no other better protocol to treat the cancer happened in the prostate gland and it's very necessary to explore and find some new strategies for this malignant disease. ADEPT is one of the strategies on the way to discover the possible therapy for it. Our research team has been working on the carboxypeptidase Al system for ADEPT to treat prostate cancer and established a stronger basis for further development thus made some exciting progresses. We have synthesized two prodrugs derivated from methothexate- a -peptide called MTX- a -phenylalanine and MTX- a -arginine. After hydrolysis by carboxypeptidase A, the MTX- a -phenylalanine cleaved the a -carboxyl...