Zhou H M, Bolon I, Nichols A, Wohlwend A, Vassalli J D
Department of Morphology, University of Geneva Medical School, Switzerland.
Cancer Res. 2001 Feb 1;61(3):970-6.
The serpin plasminogen activator inhibitor (PAI) type 2 is expressed in differentiated epidermal keratinocytes. To explore its role in this tissue, we studied the impact of PAI-2 overexpression on epidermal differentiation and skin carcinogenesis. A mouse PAI-2-encoding transgene was targeted to basal epidermis and hair follicles under the control of the bovine keratin type 5 gene promoter. Two mouse lines were established, one of which strongly expressed the transgene and produced elevated levels of PAI-2 in the epidermis. Although it had no manifest impact on cellularity or differentiation of skin or hair follicles, PAI-2 overexpression rendered the mice highly susceptible to skin carcinogenesis induced by a single application of 7,12-dimethylbenz(a)anthracene (initiation) followed by twice weekly applications of 12-O-tetradecanoylphorbol-13-acetate [TPA (promotion)]. In transgenic mice, papillomas could be observed after 3 weeks of promotion; after 8 weeks, 94% (31 of 33) of transgenic mice had developed readily visible papillomas, whereas only 35% (7 of 20) of control mice (transgene-negative littermates) had barely detectable lesions. After 11 weeks, all but 1 (32 of 33) of the transgenic mice had papillomas as compared with only 65% (13 of 20) of control mice. After 11 weeks of promotion, application of TPA was terminated. In control mice, papillomas regressed and eventually disappeared; in transgenic mice, there was continued growth of papillomas, some of which further progressed to carcinomas. In contrast to massive apoptosis in regressing papillomas of control mice, only a few apoptotic cells were detected in transgenic papillomas after the cessation of TPA application. The effect of PAI-2 on papilloma formation did not appear to involve inhibition of the secreted protease urokinase-type plasminogen activator (uPA): PAI-2 accumulated predominantly in cells, and PAI-2 overexpression failed to alleviate a phenotype induced by uPA secretion, as demonstrated by a double transgenic strategy. In addition, in situ hybridization revealed that uPA mRNA is not expressed concomitantly with PAI-2 in developing papillomas. We conclude that overexpression of PAI-2 promotes the development and progression of epidermal papillomas in a manner that does not involve inhibition of its extracellular target protease, uPA, but appears to be related to an inhibition of apoptosis.
丝氨酸蛋白酶抑制剂纤溶酶原激活物抑制剂（PAI）2型在分化的表皮角质形成细胞中表达。为了探究其在该组织中的作用，我们研究了PAI - 2过表达对表皮分化和皮肤癌发生的影响。在牛角蛋白5型基因启动子的控制下，将编码小鼠PAI - 2的转基因靶向基底表皮和毛囊。建立了两个小鼠品系，其中一个强烈表达转基因并在表皮中产生升高水平的PAI - 2。尽管它对皮肤或毛囊的细胞数量或分化没有明显影响，但PAI - 2过表达使小鼠对单次应用7,12 - 二甲基苯并(a)蒽（启动），随后每周两次应用12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯[TPA（促癌）]诱导的皮肤癌发生高度敏感。在转基因小鼠中，促癌3周后可观察到乳头状瘤；8周后，94%（33只中的31只）的转基因小鼠出现了易于观察到的乳头状瘤，而对照小鼠（转基因阴性同窝仔）中只有35%（20只中的7只）有几乎检测不到的病变。11周后，除1只（33只中的32只）外，所有转基因小鼠都有乳头状瘤，而对照小鼠只有65%（20只中的13只）有。促癌11周后，停止应用TPA。在对照小鼠中，乳头状瘤消退并最终消失；在转基因小鼠中，乳头状瘤持续生长，其中一些进一步发展为癌。与对照小鼠消退的乳头状瘤中的大量凋亡相反，在停止应用TPA后，转基因乳头状瘤中仅检测到少数凋亡细胞。PAI - 2对乳头状瘤形成的影响似乎不涉及对分泌型蛋白酶尿激酶型纤溶酶原激活物（uPA）的抑制：PAI - 2主要在细胞中积累，并且如双转基因策略所示，PAI - 2过表达未能减轻由uPA分泌诱导的表型。此外，原位杂交显示在发育中的乳头状瘤中uPA mRNA与PAI - 2不同时表达。我们得出结论，PAI - 2的过表达以一种不涉及抑制其细胞外靶蛋白酶uPA的方式促进表皮乳头状瘤的发生和发展，但似乎与凋亡抑制有关。
