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| Dr Weir's pomeranian Tex hangs twenty on a surfboard at home. As you do. |
Immunotherapy is a hot area of oncology research, but it isn't easy to get one's head around. As SAT readers will know we're undertaking an oncology distance education program this year, and so far a structured investigation into the literature on cancer in companion animals has been mind-blowing.
Tumour cells survive in part by evading the immune system, so turning the immune system against tumours makes intuitive sense. Of course, tumours are heterogenous, complex structures and there is no magic bullet. They can maniupulate the immune system and use things like inflammation to their advantage. However, canine trials of autologous vaccines are promising.
WARNING: There is a surgical image in this post of a spleen. The patient is anaesthetised and the spleen was removed without complications, and the patient made a full recovery. Spleens look like big purple things and in the scheme of things they aren't all all disgusting, but some readers might want to scroll down with care.
Dr Christopher Weir, at
the Bill Walsh Translational Cancer Research Laboratory at Sydney’s Kolling
Institute, has been involved in the development of vaccines which have the
potential to improve life expectancy of both human and animal patients with
cancer.
He uses cells from the dog's own tumour as source material to create an individualised vaccine. In
preliminary trials the vaccines have successfully slowed the growth of tumours,
reduced the incidence of new tumour formation and prolonged the lives of canine
patients, some of whom were diagnosed with advanced cancer. SAT had the opportunity to ask Dr Weir some questions about his research.
How did you get involved?
It
started about eight or nine years ago. My then boss Professor Ross Davey was
interested in targeting vasculature proteins of tumours with either drugs or
monoclonal antibodies carrying drugs. We had developed a method where we could
isolate proteins from the vasculature of tumours, and spent about a year trying
to make antibodies against these proteins.
It
dawned on me that we could see if they would work in a vaccine scenario. We
started with pretty crude vaccines around four to five years ago that didn’t
work initially. Since then we’ve done a lot of work to improve and then fine-tune
them.
How do vaccines work against cancer?
We
aim to get as much of the tumour as we can, and we mash it up, using soluble
proteins in a special buffer. We slightly modify the tumour proteins and link
these to a bacterial protein, which acts like a stimulant and attracts T-cells.
Our understanding is that because the tumour cells are linked to a stimulant,
the immune system processes and recognises them as foreign, then goes back in
and attacks the residual tumour.
But the sample needs to be large?
Where
we only have a biopsy sample it doesn’t work as well. We think that you need to
disrupt the tumour significantly because it is a closed off environment. The
immune system gets in there but its effects appear to be short-lived. If you
get a nice chunk and disrupt the tumour, and then vaccinate, the immune system
has a bit of an advantage. We’ve made vaccines for dogs with really advanced
cancer, and their vets have done some pretty amazing surgery to get a good part
of that tumour out.
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| Splenic mass being removed via an emergency splenectomy. (NB this mass turned out to be a haematoma, not a tumour, but one needs histopathology to differentiate). |
How long does it take to make the
vaccine?
Dependant
upon when the sample is received, the vaccine should be ready for injection at
the vet by suture removal. The tissue needs to be fresh or frozen – you can’t
have formalin near it.
How many vaccines does a dog need?
Two
shots, three weeks apart.
Would autologous vaccines work
against some cancers better than others?
It
seems so, although it may be too early to tell. For the safety trial we have
taken on almost any patient whose owners are willing to enrol them in the
study. One type of cancer the vaccines work particularly well on is
osteosarcoma. The average survival time with amputation and chemotherapy is
around 9-12 months. We’ve treated three dogs with vaccines, and two lived
beyond two years. The third had metastatic disease and lived for nine months.
Are you still accepting animals into
the trial?
We
have limited places left in the safety trial and we only have Animal Ethics
approval for cases in NSW, Queensland or Victoria. As a part of this trial the
Bill Walsh Cancer Research Laboratories have made the vaccines for free but we
do require the tumour to have histopathology done on it to be correctly
identified and graded, and be able to track the dog’s progress.
RegeneusLtd have the rights to commercialise the vaccine and next year we will perform
a controlled study on the use of the vaccine in dogs with osteosarcoma in the
US.
What about cats?
We
haven’t yet obtained ethics approval to recruit cats.
Dr Weir will be talking at the 2014 Annual AVA Conference in Perth. For more info visit the conference website here.
Meanwhile, about those guinea pigs...
I've had a lot of queries about the wellbeing of Osler and Cushing, the guinea pigs born on Saturday. I can report that they continue to be the cutest critters on the planet, they're healthy, and that Cornflake really is the most wonderful mother. If you have the opportunity, now is the time to buy shares in Basil, bok choy, parsley and every other vegetable that I am spending a fortune on. Cornflake is making up for all the calories she pumped into those babies!!! |
| Cushing and Osler are held while their Orchard grass is freshened up. |
