Dr Tom Mules Photo: Sciencelens
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Dr Tom Mules wears two hats. He’s a researcher at the Malaghan Institute for Medical Research, but he’s also a gastroenterologist at Hutt Valley hospital. It’s there that he meets patients suffering from stomach cancer.
“It’s a horrible disease. A large number of people are diagnosed when the treatment options are limited, when it’s too late for surgery,” he says.
This is what has motivated him to take on his latest research challenge – one that he hopes will reduce stomach cancer rates and disparities in Aotearoa.
What’s a bacterium got to do with stomach cancer?
Worldwide, stomach cancer was responsible for more than 660,000 deaths in 2022. In Aotearoa New Zealand it’s the eighth leading cause of cancer death for men. But when you look into the data, the picture gets more complicated. Māori and Pacific peoples are three to six times more likely to develop stomach cancer, and chances of survival are worse.
There are some well-established risk factors for stomach cancer, and one of these is infection with the stomach bacterium Helicobacter pylori (H. pylori). Many people around the world are infected with H. pylori, between 40–50% of the global population, and a lot of people are asymptomatic. However, in some people H. pylori can cause inflammation of the stomach lining, and, if left untreated, this can lead to tissue damage, ulcers, and eventually, for some people, stomach cancer.
As Tom explains, we don’t have up-to-date data on the rates of infection of H. pylori in New Zealand, the best information we have comes from a small South Auckland study from over a decade ago.
Looking at just shy of 600 people, the researchers found that around 30% of Māori and Pasifika had H. pylori infection, while for New Zealand Europeans it was just under 8%.
A team at the University of Otago is currently running a study to find out how common H. pylori is in New Zealand, so that we have better numbers.
Kate Maclean Photo: Claire Concannon / RNZ
The rise of resistance
Of course, because it is a bacterium, we can target it with antibiotics. The current strategy in New Zealand is a kind of scattergun attack: patients diagnosed with an infection will be given a mixture of three antibiotics to take.
However, worldwide there has been a rise of antibiotic-resistant strains of H. pylori. Again, we don’t have recent figures on the extent of the problem here, says Tom, but it’s likely to have followed the trend overseas.
Unfortunately, H. pylori is notoriously hard to grow in the lab, meaning it’s tricky to test its resistance to different antibiotics.
This is where Tom’s current research comes in.
At the Malaghan Institute, Tom is working with fellow researcher Kate Maclean to develop a new way to test for H. pylori. By extracting the H. pylori bacterial DNA from patient stomach tissue samples – or, they hope, the less invasive-to-collect stool samples – they’ll use a molecular biology technique to look for the presence of antibiotic resistance genes.
If it works, clinicians will be able to quickly test for resistance, and then tailor the antibiotic treatment for the patient based on exactly what strain of H. pylori they are infected with.
To evaluate whether this results in better health outcomes for patients, Tom and Kate, along with Dr Stephen Innes of Hutt Valley hospital and the University of Otago, are establishing a clinical trial to test this tailored treatment against the current treatment regime.
Listen to the episode as Claire visits Tom and Kate in the Malaghan Institute to find out just how they are going to go about this.
Dr Chris Puli'uvea. Photo: Tim Hamilton/Vision Works Photography
Genetic variants and the immune system
Just as changes in the H. pylori genome can affect whether antibiotics will work on it, small variations in human genes can change how people might respond to therapeutic drugs or affect their susceptibility to different diseases.
Dr Chris Puli’uvea from Auckland University of Technology researches the immune system and is particularly interested in variants commonly found in Māori and Pacific genomes.
Listen as Chris explains to Claire how small changes in the genome can potentially have a big effect, and how studying these variants can help us better understand the immune system.
Learn more
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Listen to ‘Planning for Aotearoa’s genomic medicine future’ to learn more about the Aotearoa Variome project, which aims to add to our knowledge of the natural variation in Māori genomes.
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This year the Hereditary Diffuse Gastric Cancer Team won the Prime Minister’s Science Prize for their work identifying a genetic link, and developing a test, to a hereditary form of stomach cancer. They spoke to Susie Ferguson on Saturday Morning, and keep an eye out on Our Changing World for an upcoming episode about this work too.
