Image: Latvian Biomedical Research and Study Centre
Early cancer detection
Ģederts Ģelzis, Riga
April 23, 2013
Latvian scientists are close to inventing a non-invasive blood test for early detection of gastric cancer. The disease is often only diagnosed when it is too late for treatment.
After six years of painstaking research, scientists at Latvia's Biomedical Research and Study Center in Riga are starting to see the fruits of their labor. Last year they made one of the most significant achievements in science in Latvia - they came a step closer towards inventing a new method for diagnosing gastric cancer in its initial stages - before it's too late for treatment.
They have discovered auto-antibodies that may work against tumor-associated antigens.
Antibodies are proteins produced by B-cells in the human immune system. Their task is to fight viruses and bacteria. But the immune system can also produce auto-antibodies.
Auto-antibodies see the body's own tissues as foreign and so try to neutralize them. The antibodies identify the foreign elements by way of antigens - substances that cause the immune system to react to unknown objects.
And it's these antigens that are the basis of the study, published in the "International Journal of Cancer" earlier this year.
In search of the immunome
"In the first step we tried to identify the so-called cancer immunome," says Aija Linē, the chief scientist of the Latvian Biomedical Research and Study Centre. "Basically, it is a set of antigens that the human immune system can recognize and produce antibodies against."
Aija Linē and her team of researchers initially tried to discover all the antigens associated with various types of cancer. They then focused on gastric cancer.
So far they have obtained more than 1500 antigens. All of the antigens are stored in a special database. But it's with the gastric cancer study where the scientists have made their discovery.
"We have identified a set of 45 antigens," says Linē. "If we detect auto-antibodies against these 45 tumor antigens, we can detect the presence of cancer with approximately 60 per cent sensitivity."
So, in a group of 100 gastric cancer sufferers, the scientists they could correctly identify 60 cases.
But how does it work?
It all starts with your doctor, who takes a sample of tumor tissue during surgery. The sample is sent to a laboratory where scientists extract its genetic data. To do this, molecular biologists use various laboratory tests, high-tech devices and scientific calculations to find the auto-antibodies.
No magic bullet against cancer
The results of the analysis are displayed on the lab's computer, via a microscope and special scanner.
There is an image with a pattern of many green and red spots of various degrees of intensity. They reveal how the immune system reacts to the gastric cancer.
"Each of these spots represents one single antigen," says Linē.
She explains that if there are bright red spots in the pattern, they can tell that the patient's serum has antibodies against tumor-associated antigens. "We never see reactions against these antigens in healthy control tests."
Linē and her team of scientists believe that their study of auto-antibodies will enable them to invent a simple, non-ivasive blood test for diagnosing gastric cancer.
Stomach cancer tends to be detected in its advanced stages - when it's too late for treatment. Doctors use endoscopy - a complicated and expensive procedure during which a thin tube, with a tiny camera, is inserted into the patient's body. There's also a pepsinogen test – a blood test for chronic atrophic gastritis and other conditions, but it does not reveal all the tumors in the stomach.
Growing threat of cancer
Stomach cancer is caused by the Helicobacter pylori which are commonly found in the stomach. According to the International Agency for Research on Cancer, gastric cancer is the fourth most widespread form of cancer in the world.
"Latvia has some of the highest rates of gastric cancer," says Mârcis Leja, a gastroenterologist at Riga Eastern Clinical University Hospital. "Each year around 600 people fall ill with the illness in Latvia."
Leja and others say there is an urgent need for a simple screening method in countries like Japan, Korea, Latin America and also the Baltic States, where the incidence of stomach cancer is also very high.
Rolando Herrero, the head of Prevention and Implementation Group at the International Agency for Research on Cancer, says the Latvian scientists have made an important discovery. But he says it is too early to say whether it will solve every problem.
"The most important thing is to make sure that at the population level, when this test is applied to a large population, that it's able to detect the early cancers that are present in that population," says Herrero. "This will require a different study design, which can be relatively complex and sometimes very costly."