Campo M S, Jarrett W F, Barron R, O'Neil B W, Smith K T
Beatson Institute for Cancer Research, CRC Beatson Laboratories, Glasgow, Scotland.
Cancer Res. 1992 Dec 15;52(24):6898-904.
The bladder cancer syndrome that often accompanies chronic enzootic hematuria in cattle grazing on pastures infested by bracken fern has been experimentally reproduced in animals fed a diet of bracken. The experimentally induced tumors were histologically and pathologically indistinguishable from the naturally occurring ones and comprised two main types: (a) carcinoma of the urothelium identical to that seen in humans; and (b) hemangioendotheliomas of the subjacent capillaries. Often the two types of tumor occurred together in the same bladder. In animals experimentally immunosuppressed with azathioprine "bracken type" hemangiomas developed in the bladder lining. DNA of bovine papillomavirus (BPV) type 2 was found in 46% (7 of 15) of the natural cancer cases and in 69% (9 of 13) of the experimentally induced lesions, independently of histological type and including the hemangiomas of the azathioprine-treated animals, suggesting a close association between BPV and bovine bladder neoplasia. Moreover, BPV-2 DNA was found in experimental animals that had not been inoculated with BPV at all or had been inoculated with a different BPV type and had been kept in isolation, suggesting that BPV can persist in a latent state and be activated when the animal is exposed to the bracken cocarcinogens and to immunosuppressants.
在食用蕨菜的动物中，膀胱癌症候群常伴随慢性地方流行性血尿出现，这种候群已在喂食蕨菜的动物身上通过实验重现。实验诱导产生的肿瘤在组织学和病理学上与自然发生的肿瘤并无差异，主要有两种类型：（a）与人类所见相同的尿路上皮癌；（b）下方毛细血管的血管内皮瘤。通常这两种肿瘤会在同一个膀胱中同时出现。在用硫唑嘌呤进行实验性免疫抑制的动物中，膀胱内衬会出现“蕨菜型”血管瘤。在46%（15例中的7例）的自然癌症病例以及69%（13例中的9例）的实验诱导病变中发现了2型牛乳头瘤病毒（BPV）的DNA，无论组织学类型如何，包括硫唑嘌呤处理动物的血管瘤，这表明BPV与牛膀胱肿瘤之间存在密切关联。此外，在根本未接种BPV或接种了不同BPV类型并处于隔离状态的实验动物中也发现了BPV-2 DNA，这表明BPV可以以潜伏状态持续存在，并在动物接触蕨菜协同致癌物和免疫抑制剂时被激活。
