Malignant Histiocytosis in the Bernese Mountain = Dog:

Malignant Histiocytosis = in the=20 Bernese Mountain Dog:

Study of the = physiopathology and=20 genetic causes

Written from = notes by Pat=20 Long from the presentation by Dr. Andr=E9.

By Dr. = Catherine=20 Andr=E9

She graduated = with a PhD=20 in Molecular genetics and oncology at the Paris University in 1992. = Since 1995=20 she has worked at the University of Rennes in France (CNRS) on canine = genomics=20 and genetics. She manages the =93canine genetics=94 group in CNRS = working on the=20 search for the genetic basis of inherited diseases in canines and=20 humans.

Presented = October 7, 2006=20 in Como Italy.

In=20 the study of the genetic basis for disease, it must first be determined = if the=20 disease is probably genetic. Pedigree study is used for this. The aim of = canine=20 genetic research is to develop genetic tests, and to determine if it is = a=20 homologous disease in humans =96 in other words, does it involve the = same genetic=20 mutation in humans.

Canine histiocytic = poliferative=20 disorders are hetergenous diseases that include reactive disorders such = as=20 cutaneous and systemic histiocytosis, and neoplasia such as cutaneous=20 histiocytoma and localized and disseminated histiocytic sarcoma = (malignant=20 histiocytosis). It involves the accumulation and proliferation of = histiocytes in=20 specific tissues.

1. = Cutaneous histiocytoma:
Cutaneous = histiocytoma=20 is the proliferation of epidermal langerhans cells. It is found more in = young=20 dogs, there is no breed disposition, and it normally = regresses.

2. = Reactive = histiocytic=20 disorders:
Cutaneous histiocytosis = is=20 characterized with cutaneous lesions. It is called systemic = histiocytosis=20 when extensions to the lymph nodes or other tissus is observed. It = is=20 familial in Berners, and is generally seen in young adults aged 4 to 5 = years.=20 It may be an=20 immune system deregulation.

3. = Malignant histiocytosis = (Histiocytic=20 sarcoma):
Malignant = histiocytosis=20 is an aggressive disseminated histiocytic sarcoma, found in the lungs, = spleen,=20 liver, bone marrow, among other organs. There is a high incidence of the = disease=20 in BMDs, and it represents nearly 25% of the cause of death in the = breed,=20 perhaps more =96 it is probably under diagnosed. It was found to be = genetic=20 (Padgett et al. 1995). About 80% of all cases are found in Bernese, = Rotties,=20 Goldens, and Flat Coated Retrievers.

The = clinical signs=20 of MH can involve: loss of weight, reduction of appetite, or a bad mood. = Tumors=20 in the lung may be indicated by a cough, and tumors in the liver may be=20 indicated by pale gums. It may be found in one organ, or it may be=20 multifocal.

The = diagnosis can=20 only be done by cytology and histology. Immunohistochemistry is needed = in=20 borderline cases. Dr. Peter Moore at UC Davis has developed special = reagents to=20 assist with this.

= Histiocytosis shares=20 many clinical and pathological features with Langerhans cell = histiocytosis in=20 humans, for which the underlying causes are still unknown. It occurs in = children=20 typically under the age of 5 years, and it is rare. There are only about = 50=20 cases per year in France. It can evolve to dramatic tumorgenic form, = which=20 resemble canine MH.

MH in = Berners is a=20 unique spontaneous model for human genetic study, so it is ideal for = genetic=20 research. The goal of the research is to develop genetic tests, aid in=20 diagnosis, and ultimately to prevent the disease in canines and to = facilitate the search for = the genes=20 responsible of the human forms of Histiocytosis.

The search of the genetic bases of MH = in the=20 BMD has been undertaken:

=B7 =20 In France, at the = CNRS of=20 Rennes (Lab of Catherine Andr=E9), a family of more than 300 dogs has = been=20 collected, 103 of those dogs were affected. All affected dogs in the = study have=20 a histopathological report and are submitted for histological = confirmation and=20 characterization. There were 49 males, 54 females. There were 33 = unaffected dogs=20 all over the age of 10 years.

A segregation analysis is underway = to=20 determine the mode of transmission. Up=20 to now, a transmission mode involving a small number of genes has been=20 hypothesized (oligogenic transmission). Moreover, owing to a questionnaire = completed by the=20 veterinarians who are referring the MH cases, clinicopathological data = are under=20 investigation. A better characterization of the condition is also = underway=20 through immunohistochemical analysis. The genetic analysis is undertaken = by a so=20 called "Genetic Linkage Analysis" on 200 dogs of the family and by = the=20 collection of tumor tissues to analyze gene expression at the RNA=20 level.

=B7 =20 In the US, at the = NIH, Bethesda=20 (Lab of Dr. Elaine Ostrander), a set of 100 cases and controls from = American=20 Berners are also being collected, and genetic analyses are underway. = This is=20 called an "association study" using a population of unrelated healthy = and=20 affected dogs. 60 affected and 125 unaffected BMDs were = analyzed.

=B7 =20 In the US, at the = North=20 Carolina University, in Raleigh (Lab of Dr. Matthew Breen) another = genetic study=20 is ongoing on fresh tumor tissue samples to find chromosomal = abnormalities.=20

These 3 genetic studies aim to identify = specific=20 genes that are involved in the disease.

In France, = at the=20 CNRS of Rennes and the Veterinary school of Nantes (C. Andr=E9 and J. = Abadie),=20 clinicopathological data were obtained from the analysis of 60 affected = dogs.=20 The data for this study will be published in 2007, and updated = here.

= There is a high prevalence of MH in = Berners in=20 France. Incidence is similar in males and females. The mean age is 6 = years.=20 There is no association with other proliferative histiocytic diseases, = and no=20 association with vaccines, infectious diseases, or environment. There is = a very=20 homogeneous clinical presentation, and a poor prognosis.

After 10 = years of=20 mapping the canine genome, 10,000 genes were finally mapped (Hitte et = al.,=20 2005 : a collaboration between C. Andr=E9 and F. Galibert = =96France, E.=20 Ostrander =96US, M. Breen =96US, E. Kirkness =96US, and P. Deloukas = =96GB) and the=20 sequencing of the entire genome was completed last year (Lindblad-Toh et = al.,=20 2005, international collaboration). 2,000,000 polymorphic markers, or = SNPs were=20 identified. Among the 2000 microsatellite markers, 300 microsatellite = markers=20 well distributed throughout all the chromosomes have been selected for = genetic=20 studies.

Now these = tools are=20 ready to serve for genetic mapping with complementary methods in the = study of=20 Dr. C. Andr=E9 and E. Ostrander, in collaboration. Both studies use the = same sets=20 of markers but different samples (a family in France, a series of non = related=20 cases and controls in the US). Experiments and statistical analyses are = being=20 done. In parallel, tumor samples have been collected to analyze = RNA and=20 gene expression of candidate = genes=20 (among others growth factors, receptors, adhesion molecules, = interleukins=85).=20

If you want to = participate=20 in the study, please see the protocol by clicking here.

Due to = shipping=20 times, all European samples should be sent to Dr. Andr=E9=92s lab in = France, and all=20 North American samples should be shipped to the researchers Dr. E. = Ostrander or=20 M. Breen in the USA.

The following would be needed:

=B7 Pedigree

=B7 Blood sample in an EDTA tube

=B7 Knowledge of whether the dog is affected = or=20 not

=B7 Histopathological report

=B7 Tumor and healthy tissue (fresh, -20=B0C = frozen or in=20 paraffin)