(CANCER RESEARCH 48, 3828-3833, July 1, 1988] Transmissibility of a Neurofibromatosis-like Disease in Bicolor Damselfish ' Michael C. Schmale2 and George T. Hensley Division of Biology and Living Resources, Rosenstiel School of Marine and Atmospheric Science [M, C. S.J, and Department of Pathology, School of Medicine [G. T. H.I, University of Miami, Miami, Florida 33149 ABSTRACT A neoplastic disease that affects a common species of marine fish, the bicolor damselflsh (Pomacentrus partitas), on Florida reefs consists of multiple, disseminated neurofibromas (including plexiform lesions), ma lignant schwannomas, and hyperpigmented epidermal lesions. Based on similarities to von Recklinghausen neurofìbromatosis,we have termed this disease damselflsh neurofìbromatosis.Previous surveys of the prev alence of fish with damselflsh neurofìbromatosison Florida reefs dem onstrated a distribution pattern of cases consistent with what would be expected for an infectious disease. The transmissibility of damselfish neurofìbromatosiswas assessed by inoculations of homogenized tumor tissue s.c. and i.p. into healthy bicolor damselfish. This protocol resulted in the development of Schwann cell tumors, identical to the naturally occurring lesions, at the injection sites in approximately 84% of inocu lated fish. These tumors appeared within an average of 5 mo of inoculation for juvenile fish and 14 mo for adults. Experimentally produced tumors appeared to arise in host fish by the neoplastic transformation of host nerves rather than by transplantation and proliferation of tumor cells from the donor fish. This finding suggests that an infectious, transmissible agent such as a virus may be the etiological agent responsible for production of neurofibromas and other Schwann cell tumors in this species of fish. INTRODUCTION We have previously described a neoplastic disease that affects a common species of marine fish, the bicolor damselfish (Po macentrus partitus), on Florida reefs (1, 2). The hist »patholog ical features of this disease are similar to many of the major stigmata of von Recklinghausen NF3 including: multiple, dis seminated neurofibromas (including plexiform lesions); malig nant schwannomas; and hyperpigmented epidermal lesions. Based on these similarities, we have termed this disease DNF. The human and fish diseases differ chiefly in that the fish tumors exhibit a higher degree of malignancy, and the hyper pigmented lesions are composed primarily of neoplastic, rather than benign, cells. Neurofibromatosis in humans has been established to be an autosomal dominant disorder with essentially complete pene- trance. However, approximately one-half of the known cases is attributed to new mutations (3). Considering the high incidence of this disease (approximately 1 in 3000 births), this represents one of the highest mutation rates reported for a genetic disease (3,4). Surveys for oncogene expression have not yielded positive results (5), and the gene or genes responsible for this disorder have not been identified. However, recent DNA restriction fragment length polymorphism studies of affected families have suggested that at least one gene involved in von Recklinghausen Received 9/21/87; revised 2/22/88; accepted 4/4/88. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 'Supported by USPHS Grant NS-21997 (to M. C. S.) from the National Institute of Neurological and Communicative Disorders and Stroke. 2 To whom requests for reprints should be addressed, at Rosenstiel School of Marine and Atmospheric Science. University of Miami, 4600 Rickenbacker Cswy., Miami, FL 33149. 3The abbreviations used are: NF, neurofibromatosis; DNF, damselfish neu rofìbromatosis;HTLV-1, human T-lymphotrophic virus type 1; MEM, minimal essential medium; RSV, Rous sarcoma virus: MSV, murine sarcoma virus; MLV, murine leukemia virus. NF is located on chromosome 17, and the gene responsible for the central form of NF is located on chromosome 22 (6, 7). The lack of information on the actual gene(s) or gene products responsible for this disorder as well as a lack of understanding of the extreme variability in phenotypic expression seen in various forms of NF may be largely attributable to the absence of suitable animal models of NF. Although Schwann cell tumors have been observed sporadically in various mammalian species, none appears predictably or at high incidence. Malignant schwannomas have been produced in neonatal rats by transpla- cental administration of nitrosamines. However, these animals do not develop neurofibromas or other signs of NF. Recently, neurofibromas have been observed in transgenic mice produced by the insertion of the tat gene and associated long terminal repeat of HTLV-1 into fertilized eggs (8). Numerous cases of peripheral nerve sheath tumors have been reported in fishes (9- 11). However, most of these cases represent isolated occur rences, and attempts to transfer such tumors have been unsuc cessful (12). At present, there are apparently no documented cases of successful transmission of a Schwann cell tumor to a noninbred or nonimmunosuppressed host. Surveys of the prevalence of fish with DNF conducted pre viously on reefs in the Florida Keys demonstrated that diseased fish were significantly more abundant on reef areas with higher population densities of P. partitas and that affected fish were spatially clustered (13). These results are consistent with distri bution patterns produced by infectious diseases. Bicolor dam- selfish are aggressive, territorial fish that often inflict injuries on each other in the course of territorial conflicts. Thus, the social behavior of these fish would provide ample opportunity for the contact transmission of an infectious agent. An experi mental protocol was designed to assess the potential for trans mission of DNF to healthy bicolor damselfish. This protocol was designed to maximize the likelihood of successfully trans ferring the tumors. MATERIALS AND METHODS Bicolor damselfish used in these studies were collected from reefs offshore of southern Florida. Fish were maintained in the laboratory in 110-liter aquaria, subdivided into 37-liter compartments holding one fish each. Experimental and control fish were kept in different aquaria. Aquaria were maintained as closed systems at 21-27°Cat a salinity of 30-38 ppt. All fish were observed in the laboratory for at least 2 wk prior to experiments to ascertain that they were asymptomatic at the time an experiment began. Five transmission experiments were conducted utilizing a total of 43 fish. Two control studies involved 11 fish. Adult fish of an approxi mately equal sex ratio as well as juveniles were utilized in these studies. Gonadal maturation occurs in P. partitas when fish are 55 to 65 mm in total length (14). In the present study, fish 60 mm and larger were considered to be adults. These fish reach a maximum length of about 85 mm. Transmission experiments were conducted by injecting a homogenate of tumor tissue into healthy fish. In each experiment, except Experi ment 2, both pigmented and nonpigmented tumor tissues were obtained from one or two fish with spontaneous DNF. A serial passage of the tumor was attempted in Experiment 2, with donor tissue being obtained from a nonpigmented tumor that developed at an injection site of a 3828 Research. on September 23, 2015. © 1988 American Association for Cancer cancerres.aacrjournals.org Downloaded from