O'Brien T G, O'Donnell K, Kruszewski F H, DiGiovanni J
Wistar Institute of Anatomy and Biology, Philadelphia, PA 19104.
Carcinogenesis. 1988 Nov;9(11):2081-5. doi: 10.1093/carcin/9.11.2081.
Recent work from this laboratory has demonstrated the presence of a structurally and functionally different ornithine decarboxylase (ODC) in mouse epidermal tumors induced by a two-stage protocol involving initiation with 7,12-dimethylbenzanthracene (DMBA) and promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). In this report, the enzymatic properties of ODC present in DMBA-initiated chrysarobin-promoted papillomas are compared to the enzyme induced by chrysarobin in normal epidermis. Analyses of 13 individual tumor extracts indicated each had an elevated level of ODC activity compared to uninduced normal epidermis. Addition of GTP to the enzyme assay caused a marked stimulation of ODC activity in nine of 13 tumor extracts but had no effect on chrysarobin-induced epidermal ODC. Enzyme kinetic analyses indicated that GTP lowered the atypically high apparent Km values for L-ornithine of the papilloma enzyme to values typical of epidermal ODC. The K 1/2 for GTP activation of papilloma ODC was approximately 7 x 10(-9) M. When a series of nucleotides was tested, only GTP, the non-hydrolysable analog GTP gamma S, dGTP and GDP were capable of significant activation at 1 microM, while other derivatives including GMP, ATP and CTP were less effective. The ability of the tumor enzyme to bind GTP was confirmed by the results of GTP-agarose chromatography, in which the papilloma enzyme (but not chrysarobin-induced epidermal ODC) bound to this affinity column and could be eluted by GTP. While some differences were observed in the properties of ODC from chrysarobin-promoted versus TPA-promoted papillomas, the major conclusion of this study is that both agents cause the appearance of a functionally altered ODC in the majority of papillomas produced by a two-step protocol.
该实验室最近的研究表明，在由两阶段方案诱导的小鼠表皮肿瘤中存在一种结构和功能不同的鸟氨酸脱羧酶（ODC）。该方案包括用7,12 - 二甲基苯并蒽（DMBA）启动，并用12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯（TPA）促进。在本报告中，将DMBA启动、柯桠素促进的乳头状瘤中存在的ODC的酶学性质与柯桠素在正常表皮中诱导的酶进行了比较。对13个单独的肿瘤提取物的分析表明，与未诱导的正常表皮相比，每个提取物中的ODC活性水平都有所升高。在酶测定中加入GTP导致13个肿瘤提取物中的9个提取物的ODC活性显著刺激，但对柯桠素诱导的表皮ODC没有影响。酶动力学分析表明，GTP将乳头状瘤酶对L - 鸟氨酸的异常高的表观Km值降低到表皮ODC的典型值。乳头状瘤ODC的GTP激活的K 1/2约为7×10（-9）M。当测试一系列核苷酸时，只有GTP、不可水解的类似物GTPγS、dGTP和GDP在1μM时能够显著激活，而其他衍生物包括GMP、ATP和CTP则效果较差。GTP - 琼脂糖色谱结果证实了肿瘤酶结合GTP的能力，其中乳头状瘤酶（但不是柯桠素诱导的表皮ODC）与该亲和柱结合，并可被GTP洗脱。虽然在柯桠素促进的乳头状瘤与TPA促进的乳头状瘤的ODC性质上观察到一些差异，但本研究的主要结论是，这两种试剂都会导致在两步方案产生的大多数乳头状瘤中出现功能改变的ODC。
