AMSTERDAM – Wetenschappers hebben een vernietig-mij-niet-signaal ontdekt dat tumoren beschermt tegen aanvallen van het immuunsysteem
De onderzoekers van Stanford University in Amerika beschrijven hun ontdekking dinsdag in PNAS.
Normaal gesproken pakt het lichaam cellen die ontregeld zijn in hun groei aan door het
immuunsysteem erop af te sturen. Zogenaamde fagocyten kapselen de dader in en verteren het.
Zo niet bij tumorcellen, zij ontsnappen aan dit proces. Een van de redenen daarvoor blijkt de overproductie van het zogenaamde CD47-eiwit te zijn, zo ontdekten de onderzoekers.
Dankzij dat eiwit zet de cel een vernietig-mij-niet-signaal aan. Fagocyten treden daarom niet op en de tumor kan ongecontroleerd doorgroeien. De wetenschappers vonden het signaal bij verschillende typen kanker.
Blokkeren van het eiwit in muizen bleek het signaal uit te zetten en de groei en uitzaaiing van de tumor te remmen. De onderzoekers hopen hiermee een nieuw doel voor kankeraanpak te hebben gevonden.
Wel waarschuwen ze voor al te veel optimisme: gerommel met het signaal zou een nadelig effect op andere processen in het lichaam kunnen hebben.
Niet alleen de hond is gebaat bij de onderzoeken. Nieuwe inzichten die de diergeneeskundig zorg verbeteren kunnen
ook waardevolle informatie opleveren voor kanker bij mensen.
Een nieuw ontwikkelde kankertherapie blijkt zeer succesvol bij het behandelen van bepaalde typen kanker bij honden en katten. Dezelfde therapie zal naar verwachting ook bij mensen effectief zijn. Omdat mensen genetisch gezien erg op hun huisdieren lijken -meer dan 90% van de genen zijn hetzelfde – is honden, katten, en mensenkanker vaak vergelijkbaar.
Professor Jolle Kirpensteijn van de Universiteit Utrecht heeft de nieuwe honden en katten kankertherapie ontwikkeld. Waar het feitelijk om gaat is het inspuiten van kwaadaardige tumoren met microscopisch kleine radioactieve bolletjes. Die radioactieve stof heet holmium. Dat materiaal straalt krachtig, maar kortdurend, en over een zeer geringe afstand.
Het mooie van de holmiumtherapie is dus dat er zeer plaatselijk bestraald wordt, en maar heel even. Het levert daarom nauwelijks bijwerkingen op; de rest van het lichaam blijft gevrijwaard van radioactiviteit. Ook aantrekkelijk is dat de behandeling niet meer inhoudt dan een injectie: Snel, simpel, en nauwelijks belastend. De patiënt kan direct weer naar huis. Maar het allerbeste is nog wel dat de holmiumtherapie uiterst effectief is. Kirpensteijn is er zelf nog steeds verbaasd over…
“We noemen deze tumor het ‘Plaveisel-cel carcinoom’ en het is eigenlijk een tumor van het mondslijmvlies. Bij katten komen die heel veel voor en we hadden tot nu toe geen goede behandeling. We hebben de Holmium therapie dus op de kat uitgeprobeerd en daaruit blijkt dat de tumor enorm krimpt of zelfs helemaal verdwijnt.”
Dat is een verbluffend resultaat als je bedenkt dat er eerst helemaal geen behandeling mogelijk was, en het geeft te denken dat deze soort van kanker ook bij de mens voorkomt. Vandaar dat Kirpensteijn in zijn oratie – de aanvaardingstoespraak bij het ambt van hoogleraar – een vlammend betoog hield voor samenwerking tussen menselijke en dierlijke geneeskunde, met name als het gaat om de bestrijding van kanker: “Juist door die samenwerking kan er veel moois ontstaan; de holmiumherapie is maar een eerste voorbeeld.”
Dr. Frank Nijsen werkt in het UMC in Utrecht en is dus humaan geneeskundige. Hij is het van harte met Kirpensteijn eens vooral omdat kanker bij dieren en mensen onderling niet zoveel verschilt.
” Het lijkt op elkaar. De technieken die je gebruikt zijn hetzelfde, de tumoren lijken heel erg op wat je in de humane situatie vind. En de problemen die je tegenkomt zijn dus ook vergelijkbaar.”
Nijsen is dus ook een warm voorstander van het meer integreren van menselijke en dierlijke geneeskunde. Logisch, want als je de holmiumtherapie maar weer als voorbeeld neemt; menselijke patiënten willen ook graag geholpen worden met een simpel prikje, om daarna gewoon naar huis te gaan en geen last te hebben van bijwerkingen.
De eerste stappen richting intensieve samenwerking tussen humane – en diergeneeskunde zijn gezet. Juist de holmiumtherapie is een voorbeeld; het is een doorontwikkeling van een al langer bestaande behandeling tegen leverkanker bij de mens. Maar nu moet het ‘One Health Principle’, zoals de integratie van dier- en humane geneeskunde heet, de gouden standaard worden. Daarover zijn Kirpensteijn en Nijsen het roerend eens.
Stichting FICCA strijd tegen kanker bij honden. Wij zamelen geld in voor het onderzoek naar de oorzaken van
Leading Texas veterinarians are mobilizing to enlist pets in the testing of experimental cancer therapies, a potential benefit to not just dogs and cats but people.
The veterinarians recently set up a registry they hope will connect pet owners and cancer researchers and show that diseased pets – dogs in particular – are better predictors of the efficacy of new cancer drugs and devices in people than mice, oncologists’ favorite test subject historically.
“Dogs may be man’s best friend in more ways than one,” says Dr. Theresa Fossum, a Texas A&M professor of veterinary surgery and founder of the Texas Veterinary Cancer Registry. “Because they suffer from cancers that are nearly identical to those in humans, but quicker to run their course, they can speed up and make more reliable the process of determining whether a therapy will work.”
Veterinarians are just starting to get the ear of cancer researchers, who don’t reflexively think of naturally occurring disease models that go home with their owner, Fossum said. The Cancer Prevention and Research Institute of Texas recently rejected a grant application because “housing the dogs would be so expensive,” says Fossum. The application will be resubmitted to specify that the treated pets would remain with their owners.
Texas veterinary oncologists are hoping the registry can help change attitudes by providing a database of dogs and cats diagnosed with cancer that could be candidates for clinical research. The registry identified its first patient in November, an 8-year-old Great Pyrenees with bone cancer.
Instead of the standard treatment, amputation, Rowdy got an experimental procedure: radiation injected into 22 tiny holes drilled directly into the bone cancer. Two months later, Rowdy’s owner reports he is running around symptom-free, though Fossum stresses the six-month check-up will be the big test.
The procedure’s success in a dog trial would bode well for people with the disease – particularly children. Osteosarcoma, Rowdy’s cancer, is the sixth most common form of childhood cancer. One in 3 diagnosed with the disease die from it.
The idea of using animals’ naturally developing cancers as models for human disease goes back a decade but has never taken off.
“It’s a great concept, but the problem has always been the lack of infrastructures pairing researchers and patients,” said Dr. Peggy Tinkey, chair of veterinary medicine and surgery at the University of Texas M.D. Anderson Cancer Center.
That’s where the new cancer registry comes in. Owners of dogs and cats diagnosed with the disease are being asked to register their pet at http://texasvetcancerregistry.com/, already up and running though the official launch isn’t scheduled until this spring. Registry staff will contact the pet’s vet for more information, then look for potential research matches.
There should be no shortage of candidates. There are 77.5 million owned dogs in the United States and a fourth will develop cancer – including those in the bone, breast, pancreas, liver, prostate, lung and skin. Veterinarians report that owners increasingly want to treat them, at around $5,000, but the options can be limited.
The technology used in Rowdy’s case was pioneered at a Houston company, Valco Instruments, that makes very small, precise instruments used in laboratories. After his dog was diagnosed with bone cancer, the company’s president developed a drill that can open holes the size of human hairs to deliver radioactive isotopes that pinpoint the tumor and don’t damage surrounding tissue.
“It sounded perfect,” said Rowdy’s owner, Kate Cordts, a librarian in San Antonio. “Rowdy’s such an active, happy-go-lucky dog – I just didn’t have the heart for amputation.”
Just the beginning
For all their benefits, pets won’t ever replace lab mice as cancer test models. For one thing, mice are perfect specimens for engineering genetic impairments and studying precisely targeted genes or pathways suspected to be involved in a disease. For another, they’re better for establishing initial safety, necessary before experimenting in pets.
Still, Fossum thinks pets can play an important role. She notes that one reason it costs $1.2 billion, probably more, to get a new drug on the market is that most fail in clinical trials. Mice simply aren’t good disease predictors, she says, not like dogs and cats, which live with people, have intact immune systems and probably develop cancer for the same reasons.
The pet cancer registry is just the beginning. Fossum has plans, once she gets grant money, to launch pet registries for heart and kidney disease too.
By Todd Ackerman
Dogs With Cancer Helping to Find a Cure
Dogs receiving various treatments are helping medicine find new therapies for people, too
When her black Lab, Emmy, started limping in 2008, Kathi Streeter suspected the normal aches and pains of aging. Then came the devastating diagnosis: osteosarcoma, a deadly bone tumor. Osteosarcoma affects humans, too - mostly children, whose long-term survival rate, if the cancer spreads, is under 40 percent. Though Emmy died in May at the ripe old age of 13, she gained nearly three years of healthy living, and one day her treatment may help those kids.
[Learn more about how dogs help mankind in Mysteries of Science: Amazing Animals.]
In her quest to save Emmy, Streeter learned about a study underway at Colorado State University’s Animal Cancer Center in Fort Collins, about 100 miles from her home in Franktown, Colo. It was testing a gene therapy that could be injected straight into osteosarcoma tumors. The gene delivers a molecule designed to induce the cancer cells to self-destruct. Veterinarians there wanted to see how well dogs reacted to the treatment, as part of an effort to determine whether it might also be investigated for use in children.
Streeter is a cancer survivor herself - in 2004, she underwent a double mastectomy and chemotherapy to treat breast cancer - and didn`t hesitate to sign Emmy up. After the injection, CSU vets gave Emmy the standard treatment, too: amputation of her leg plus six rounds of chemo. They’re now evaluating how the injection affected the tumor. Although the results of this trial have not yet been published, previous trials suggest that the therapy may enhance the immune system’s ability to combat the tumor.
CSU is one of 20 participants in the Comparative Oncology Trials Consortium (COTC), a growing program started in 2003 and managed by the National Cancer Institute to study cancer in dogs and to recruit them for clinical trials of new treatments. The goal is more effective, more personalized treatments for man as well as his best friend. “Several tumor types in dogs mimic human cancers in their biologic behavior and genetic signature,” says Susan Lana, associate professor of clinical oncology at CSU. “Dogs can help us try to answer questions like, ‘Why does this cancer spread?’ and ‘ Are there genetic pathways we can explore for treatment?’ ”
Dogs are ideal models, Lana says, because they’re genetically similar to humans and share the same environment. They develop cancer naturally, unlike mice and rats, which must be engineered to have the disease. And dogs are big enough to undergo MRIs as well as blood tests and biopsies, so scientists can better observe changes in the cancer over time. Thanks to advances in genomics and gene sequencing, researchers have established which canine cancers are most similar to their human counterparts. Besides osteosarcoma, they include prostate and breast cancer, melanoma, soft tissue sarcoma, and non-Hodgkin’s lymphoma.
Vaccine success. Comparative oncology has already produced some success stories. In 2010, the U.S. Department of Agriculture approved Oncept, a therapeutic vaccine for dogs with melanoma. Therapeutic vaccines are designed to mobilize the immune system to make antibodies against cancer cells, which ideally then destroy the cells and keep the cancer from coming back, and they’ve long been the holy grail of cancer drug development. But many of the vaccines tested have proved disappointing. If Oncept is any indication, dogs might hold the key to fine-tuning cancer vaccines. Some dogs in the Oncept trials lived more than a year after their diagnosis - far outpacing the typical lifespan of one to five months with conventional therapies.
The data from the dog trials were impressive enough to prompt the Food and Drug Administration to green-light a small human trial of a similar drug. Jedd Wolchok, a physician at Memorial Sloan-Kettering Cancer Center in New York and the drug’s codeveloper, is hoping a pharmaceutical company will fund the large clinical trials that would be needed to get the human version of the vaccine approved. “These trials can take over five years and they’re exorbitantly expensive, but the risk could lead to a long-term payoff,” he says.
Veterinarian Gerald Post learned the benefits of canine cancer trials as a pet owner. “ Instead of living three months, he lived two and a half years, - Post says of his miniature schnauzer, Smokey, a participant in the Oncept trials. “He taught me to leave no stone unturned.” Post is now an investigator for several canine clinical trials, which he runs out of his Norwalk, Conn., office.
Joining a trial offers twin rewards for dog owners: access to cutting-edge treatments they might not otherwise be able to find or afford, and, even when there’s little hope, the satisfaction of contributing to the quest for cures. “We knew the trial wouldn’t resolve the cancer,” says Richard Liscinsky, whose golden retriever, Samantha, 6, was part of a one-week trial of a protein-based lymphoma drug designed to restrict the growth of cancer cells. Liscinsky and his wife, Ann, who live in Bronxville, N.Y., hoped the treatment regimen would offer up some answers and give them one more summer in Vermont with their beloved pet. Lymphoma is all too common in golden retrievers; Samantha is the second of the three goldens the Liscinskys have owned that has contracted the disease. “It’s frightening that cancer is so rampant - for all of us,” Ann says.
Owners who participate in trials typically get at least part of the care at no charge. The funding comes from a variety of sources, including federal grants, pharmaceutical companies, and philanthropists with a soft spot for dogs. Among the last group are Dave and LuAnn Runkle of Wayzata, Minn., who lost their golden retriever, William, to a rare and aggressive form of cancer called histiocytosis and then launched the Will-Power Cancer Research Fund to support comparative oncology trials at the University of Minnesota. The $10,000 they’ve raised so far is helping to fund trials in both dogs and cats, which also develop tumors that are similar to human cancers. Dave’s motto? “Help your animal, help yourself,” he says.
Shelter rescues. Some comparative oncology programs are reaching out to dogs that have no owners to rely on. In the summer of 2009, the University of Pennsylvania’s School of Veterinary Medicine launched the Shelter Canine Mammary Tumor Program, for example. Veterinarians there rescue dogs with mammary tumors from shelters, remove the tumors, and then adopt the dogs out to local families. More than 30 dogs have benefited so far, says Karin Sorenmo, Penn Vet’s chief of medical oncology.
Sorenmo’s team is studying the tumors to try to figure out what causes benign breast cells to turn malignant and spread. “It’s metastasis that kills the cancer patient,” Sorenmo says. “If we can learn what genetic events make tumors spread, it opens up a lot of possibilities for new treatments.”
For Mildred Edmond, that possibility is intriguing on several levels. Edmond adopted Cali, a 6-year-old bichon frise in the Penn trial who had 11 tumors removed. “Poor little Cali - she had a full mastectomy,” Edmond says. Edmond herself survived breast cancer six years ago, so she is eager for the scientists at Penn to unravel the complexities of the disease. “I have two granddaughters and a great granddaughter. I’d hate for them to go through what I went through,” she says. (Edmond and Cali are both now cancer-free.)
Dog survivors sometimes play more than a research role. After Emmy survived her bout with cancer, Streeter signed her up for a program at Children’s Hospital of Denver called YAPS, for Youth and Pet Survivors. With Streeter’s help, Emmy sent letters and photos to a young girl being treated for brain cancer. “I became [the patient’s] pen pal,” Streeter says. “She brought pictures of Emmy to surgery.”
Streeter likes to think that giving Emmy the opportunity to contribute to a fuller understanding of a cancer that affects kids made the disease more bearable for everyone involved. Emmy loved children, she says. “ If I could have asked her permission to do the trial, she would have said, ‘Yeah, let’s do it.’ ”
Arlene Weintraub is the New York editor of Xconomy.com.
The College of Veterinary Medicine will begin a new trial this week.
When Luke, the Huston family`s 6 year old English Springer Spaniel, was diagnosed with lymphoma, their vet recommended a new trial at the University of Minnesota`s College of Veterinary Medicine.
Luke was the first participant in a trial for dogs with lymphoma, but he`s one of many animal-companion owners bring to the University to contribute to research.
This week, the College of Veterinary Medicine will begin a new trial aimed at the latest treatment for dogs with osteosarcoma, a cancerous bone tumor.
Osteosarcoma often occurs in dogs` front or hind legs, causing pain and bone destruction. It has high potential to spread to other parts of the body, said Antonella Borgatti, assistant professor of oncology and a researcher for the trial.
Catherine St. Hill, assistant professor of veterinary clinical science, said there are carbohydrates attached to cancer cells that make it easier for them to bind tightly to blood vessels - their mode of transportation through the body.
The goal of her research is to discover a way to either prevent the making of the carbohydrate or slow the progression of the disease.
When dogs pass away from osteosarcoma, it is most commonly a result of spreading, Borgatti said.
The OSAL - osteosarcoma and salmonella - trial aims to stop the spread of cancer through amputation of the infected limb followed by chemotherapy and treatment using genetically modified salmonella designed to attack only the cancerous cells.
Kathy Stuebner, research coordinator for the University`s Clinical Investigation Center, said researchers will use PET-CT, a full body scan used to detect cancer and cancer spread. It will be used on dogs for the first time before and after the treatment to help detect its effectiveness and identify proper treatment levels.
The goal for all their trials is to keep the dogs comfortable and prolong remission, she said.
Stuebner said the trial is `approved and ready to go.` They hope to start this week.
In the meantime, five other oncology trials are active. The trial that Luke initiated, called `Licking Lymphoma,` is testing Valspodar, a study drug, which Borgatti said should decrease the resistance to chemotherapy.
The trial was designed by Jaime Modiano, professor of veterinary clinical science, in partnership with Purdue University and the University of Pennsylvania. Modiano said the trial was designed out of `scientific curiosity` and it `is transformational because it combines companion animals and human benefit.`
Dogs with lymphoma - cancer of the lymph nodes - go through 'staging,' or full body testing, with X-rays and biopsies to determine the stage of their cancer. Generally, healthy dogs with 'B cell' lymphoma are accepted for the study, Borgatti said.
The dogs are put into two groups, some are given Valspodar and others are given a placebo, for four days. Then they all go through chemotherapy.
The Huston family got involved in the `Licking Lymphoma` trial in April when they noticed their dog Luke had swollen lymph nodes in his neck.
Mike Huston, Luke`s owner, said they took him to the vet thinking he was suffering from allergies. After a blood test, they were told that Luke might have lymphoma. Their vet said Luke might meet the criteria to be a participant in the University`s lymphoma trials.
Huston said they took Luke to the University to be tested and after a long discussion as a family they decided to apply for the trial.
After the treatment Huston said Luke went into remission for seven months.
Borgatti said that most dogs only go into remission for a few months, so in Luke`s case, the trial was a success.
`Luke never showed any signs of pain, even during treatment. He still runs and plays ball, everything is the same,` Huston said.
He added that the experience was much easier than he imagined because the veterinarians were very professional, yet personable.
`If he was going to get treatment, we decided we should do it there because the facility is the best and he could contribute to future research,` he said.
All studies that are done in the CVM are approved by the Institutional Animal Care and Use Committee, who check for ethics and animal welfare, which comforts many pet owners, Stuebner said.
There is also a financial incentive for owners to help pay for the chemotherapy in the oncology trials. The `Licking Lymphoma` trial credits the owner $2,500 after he or she makes an initial payment before treatment.
"It`s a hard decision to make and most people wouldn`t pay for treatment for their pet without financial incentive," Borgatti said.
There are free social services available to all clients who need extra support and help making a decision about what is best for them and their pet, she said.
She added that 'most owners are happy that the trial is giving them an option.' By participating in research, they get more personal attention than they would at a normal vet.
'The trials give us a chance to get to know the owners really well,' Stuebner said.
Stuebner and Borgatti said the lymphoma trial has been going on for about six months and based on their expectations, they said they hope the study will be finished in six months to a year.
The trials being done for dogs in the CVM are unique because they hope the research will be used for humans with similar diseases in the future, Borgatti said.
"It is very satisfying because if we`re wrong, we learn from it," Modiano said. "And if we`re right, we’ve got something that works better than anything else."
Luke`s lymphoma has returned, but like always, he still enjoys playing around with his family. The Hustons are working with the University to keep him comfortable as the disease progresses.
ScienceDaily (Nov. 3, 2011) - North Carolina State University researchers have uncovered evidence that evolutionary “breakpoints” on canine chromosomes are also associated with canine cancer. Mapping these “fragile” regions in dogs may also have implications for the discovery and treatment of human cancers.
When new species evolve, they leave genetic evidence behind in the form of “breakpoint regions.” These regions are sites on the genome where chromosomes broke during speciation (when new species of dogs developed). Dr. Matthew Breen, professor of genomics at NC State, and graduate student Shannon Becker looked at the breakpoint regions that occurred when the canid (dog) species differentiated during evolution. They compared the genomes of several wild canine species with those of the domestic dog. By overlaying the genomes, they found shared breakpoints among 11 different canid species — the so-called evolutionary breakpoints.
“The interesting thing about the breakpoint areas in the canid chromosome is that they are the same regions that we have shown to be associated with chromosome breaks in spontaneously occurring cancers,” Breen says. “It is possible that the re-arrangement of chromosomes that occurred when these species diverged from one another created unstable regions on the chromosome, and that is why these regions are associated with cancer.”
The researchers’ results appear in Chromosome Research.
“As species evolve, genetic information encoded on chromosomes can be restructured — resulting in closely related species having differently organized genomes,” says Becker. “ In some cases, species acquire extra chromosomes, called B chromosomes. We looked at these extra B chromosomes in three canid species and found that they harbor several cancer-associated genes. Our work adds to the growing evidence that there is an association between cancer-associated genomic instability and genomic rearrangement during speciation.”
“The presence of clusters of cancer- associated genes on canid B chromosomes suggests that while previously though to be inert, these chromosomes may have played a role in sequestering excess copies of such genes that were generated during speciation,” adds Breen. “We now need to determine whether these stored genes are active or inert — that information could give us new tools in cancer detection and treatment.”
The research was funded by the Morris Animal Foundation. The Department of Molecular Biomedical Sciences is part of NC State’s College of Veterinary Medicine.
Lymphoma is one of the most common forms of cancer in dogs. Every time I diagnose one of my patients with lymphoma I have what boils down to a “bad news : a little bit of good news” discussion with my client.
First the bad news: Lymphoma in dogs is almost always a fatal disease. But the good news is that unlike some other types of canine cancer, we can sometimes manage it quite successfully for an extended period of time.
For the minimalists amongst us, prednisone alone can make a dog feel almost back to normal for several weeks to months. More aggressive chemotherapy protocols can help many dogs live happily for an additional year or even longer. While this might not sound like much, when you put it into the perspective of a dog`s short life, it is significant.
A new, experimental vaccine might make the “good news” associated with canine lymphoma even better.
Researchers at the University of Pennsylvania recently tested a vaccine that is made by growing B-cells (a type of lymphocyte, the cells that become cancerous in lymphoma) from the patient`s own blood. These cells were then loaded with RNA that had been isolated from the dog`s tumor and injected back into the patient. Dogs in the study received three vaccinations after standard chemotherapy protocols achieved remission, and the progression of their disease was compared to a group of dogs that received chemotherapy only.
Dogs that were vaccinated and those in the control group both had similar rates of relapse. However, when treated with a second round of chemotherapy called a rescue protocol, dogs that were vaccinated had much better survival rates than those in the control group. Some vaccinated dogs were still disease-free after three years.
According to Nicola Mason, assistant professor of medicine at the University of Pennsylvania School of Veterinary Medicine and one of the authors of the study:
Though vaccinated and unvaccinated dogs relapsed with clinical disease at the same time, 40 percent of vaccinated dogs that relapsed experienced long-term survival after a second round of chemotherapy; only 7 percent of unvaccinated dogs that relapsed and were treated with the same rescue chemotherapy protocol survived long term. Furthermore, when the vaccinated long-term survivors did eventually die, they showed no evidence of lymphoma on full necropsy.
It appears that chemotherapy and the vaccine work together to improve survivability. The details of how this might work are still unclear, but continued research could lead to even more exciting results. As Dr. Mason said:
These dogs just received three doses of vaccine, three weeks apart. If we kept boosting the immune system in this way by vaccination, perhaps the dogs would not relapse in the first place.
The dogs in this study had what is called non-Hodgkin`s lymphoma in the human medical world. Fingers crossed that this research will lead to great advances in treatment for both people and pets with this all-too-common disease.
Dr. Jennifer Coates
Hoe lang leven Cockers? Volgens de Engelse Kennelclub in ieder geval langer dan 11. Wat opvalt bij dat onderzoek is dat bijna 30% van de cockers overlijden aan een vorm van kanker, en ongeveer 17% aan ouderdom. Dat is dus veel meer dan de overlijdensgevallen van FN (`maar' 5%). Nu weet ik wel ook wel dat deze informatie gekleurd is, maar de trend is duidelijk: kanker si doodsoorzaak nummer 1 bij cockers!
Kankeronderzoek bij cockers is dus ook van groot belang. Nu zijn er aanwijzingen dat er een verband is tussen anaalklier kanker (eentje die vaak voorkomt bij de cockers) en die MHC-genen. Link: http://onlinelibrary.wiley.com/doi/10.1111/j.1399-0039.2010.01554.x/abstract
Die MHC-genen moeten in zoveel mogelijk variatie in het DNA voorkomen. Elke variant hiervan kan een paar soorten aanvallers (bacterie/virus) in het lichaam herkennen en antistoffen maken om die aanval af te slaan. http://www.thetech.org/genetics/ask.php?id=131 . Wat nu precies het mechanisme is hoe daaruit kanker ontstaat is nog niet bekend, maar dat het verband houdt is wel duidelijk.
Natuurlijk zijn deze genen niet de enige faktor die meespeelt, ook de omgeving (zoals ziekten waarmee je in contact komt) spelen een belangrijke rol. Als voorbeeld baarmoederhalskanker: Als je niet besmet bent met HPV-virus krijg je geen baarmoederhalskanker. Maar als je in de MHC’s de juiste versie hebt om het virus aan te vallen zul je nooit baarmoederhalskanker krijgen ook al ben je besmet. Bij een heleboel kankersoorten zijn die verwekkers (omgevingsfactoren) jammer genoeg nog niet bekend. Maar aan de hand van de gen-variaties in het MHC moet binnenkort een inschatting te maken zijn over de kans dat je hond kanker krijgt.
Bekend is dat die variatie in MHC’s bij ingeteelde honden veel lager is dat bij een niet-ingeteelde hond. De manier om die variatie hoog te houden is dus het beperken van inteelt en inbrengen van vreemd bloed.
Die MHC-genen zullen we dus nog wel vaker tegenkomen in dit blog. Inteeltbeperking bij rashonden is een van DE grote issues in de kynologie.