British researchers have shown that a tumor-killing virus can sneak around the body by “hitchhiking” on the back of blood cells.
It is hoped reoviruses can be used to treat cancer, but there were fears they would not work if the immune system could wipe them out.
A study published in Science Translational Medicine showed the viruses could hide in the blood and reach their target.
Experts said it was an important step in advancing cancer therapies.
Reoviruses are normally harmless, but they can cause stomach upsets and colds in childhood. However, it seems they have the ability to infect and kill some cancerous cells while leaving the surrounding tissue unharmed.
However, experiments on mice suggested the virus would not survive in the blood as the immune system would destroy it.
It meant the virus would need to be injected directly into the tumour or be given with drugs to suppress the immune system.
British researchers have shown that a tumor-killing virus can sneak around the body by "hitchhiking" on the back of blood cells
A study in 10 people at the University of Leeds and The Institute of Cancer Research, at the Royal Marsden Hospital, showed that the virus could escape the immune system by hiding in the blood.
All the patients had advanced bowel cancer which had spread to the liver, and were injected with doses of the reovirus ahead of their scheduled surgery.
The virus was detected in the tumor, but not the liver, meaning it was selectively targeting the cancer. In the blood, the virus was detected in blood cells, not the liquid blood plasma all the cells float in, meaning it was “hitchhiking”, the researchers said.
Prof. Alan Melcher, from the University of Leeds, said the virus was “even cleverer” than previously thought.
“By piggybacking on blood cells, the virus is managing to hide from the body’s natural immune response and reach its target intact.”
Prof. Alan Melcher said he had “no doubt” the virus would be eventually used “in combination with chemotherapy”.
Dr. Kevin Harrington, from the Institute of Cancer Research, said: “Viral treatments like reovirus are showing real promise in patient trials.
“This study gives us the very good news that it should be possible to deliver these treatments with a simple injection into the bloodstream.”
Why reoviruses affect only cancer cells is not entirely understood. Cancer cells behave very differently to healthy cells, which may make them more susceptible to infection.
Doctors are already testing the virus in some trials in people, such as studies on head and neck cancer.
Prof. John Bell, from the University of Ottawa, has researched using genetically modified viruses to attack cancer cells.
He said viruses could be “exquisitely selective” in targeting tumors, and that this latest study had shown how safe the technique was.
“This study is an important next step in advancing oncolytic virus therapies into cancer patients.”
[googlead tip=”patrat_mediu” aliniat=”stanga”]A new treatment for leukemia had amazing results, surprising even the researchers who designed it. The new treatment has eradicated the cancer cells present in the first three patients tested bodies.
Early results of a clinical trial showed that genetically engineered T cells eradicate leukemia cells and thrive.
Scientists from the University of Pennsylvania have genetically engineered patients’ T cells — a type of white blood cell — to attack cancer cells in advanced cases of a common type of leukemia.
The first two of three patients studied, who received the innovative treatment, have been cancer-free for more than one year. In the case of the third patient, over 70% of cancer cells were removed, according to the researchers.
"Microscopic image showing two T cells binding to beads, depicted in yellow, that cause the cells to divide. After the beads are removed, the T cells are infused into cancer patients." (Dr. Carl June / Pennsylvania Medicine)
“In just three weeks, tumors were destroyed, the effect being more violent than we ever have imagined,” said Dr. Carl June, one of the researchers involved in the study.
“Each cell can destroyed thousands of cancer cells,” said June, “each patient have been removed tumors from at least 900 grams.”
“A huge accomplishment”
[googlead tip=”vertical_mare” aliniat=”dreapta”] “This is a huge accomplishment — huge,” said Dr. Lee M. Nadler, dean for clinical and translational research at Harvard Medical School, who discovered the molecule on cancer cells that the Pennsylvania team’s engineered T cells target.
Innovative treatment is using patients’ own T cells, which are extracted from body cells and then genetically modified to attack cancer cells and to multiply and then reintroduced into patients’ blood.
Findings of the trial were reported Wednesday in the New England Journal of Medicine and Science Translational Medicine.
According to LA Times report, for building the cancer-attacking cells, the researchers modified a virus to carry instructions for making a molecule that binds with leukemia cells and directs T cells to kill them. Then they drew blood from three patients who suffered from chronic lymphocytic leukemia and infected their T cells with the virus.
When they infused the blood back into the patients, the engineered T cells successfully eradicated cancer cells, multiplied to more than 1,000 times in number and survived for months. They even produced dormant “memory” T cells that might spring back to life if the cancer was to return.
On average, the team calculated, each engineered T cell eradicated at least 1,000 cancer cells.
Side effects included loss of normal B cells, another type of white blood cell, which are also attacked by the modified T cells, and tumor lysis syndrome, a complication caused by the breakdown of cancer cells.
“We knew [the therapy] could be very potent,” said Dr. David Porter, director of the blood and marrow transplantation program at the Hospital of the University of Pennsylvania in Philadelphia and a coauthor of both papers, which were published in the New England Journal of Medicine and Science Translational Medicine.
“But I don’t think we expected it to be this dramatic on this go-around.”
Bone marrow transplants from healthy donors have been effective in fighting some cancers, including chronic lymphocytic leukemia, but the treatment can cause side effects such as infections, liver and lung damage, even death.
“1/5 of bone marrow transplant recipients may die of complications unrelated to their cancer,” Porter said.
Researchers have been working for many years to develop cancer treatments that leverage a patient’s immune system to kill tumors with much greater precision.
Specialists not involved in the trial said the new discovery is very important because it suggested that T cells could be adapted to destroy a range of cancer cells, including ones of the blood, breast or colon
“It is kind of a holy grail,” said Dr. Gary Schiller, a researcher from UCLA’s Jonsson Comprehensive Cancer Center who was not involved in the trial.
“It would be great if this could be applied to acute leukemia, where there is a terrible unmet medical need,” UCLA’s Schiller said.
Dr. David Porter added:
“Previously efforts to replace risky bone marrow transplants with such engineered T cells proved disappointing because the cells were unable to multiply or survive in patients.”
“This time, the T cells were more robust because the team added extra instructions to their virus to help the T cells multiply, survive and attack more aggressively.”
“About 15,000 patients are diagnosed with chronic lymphocytic leukemia every year. Many can live with the disease for years. Bone marrow transplants are the only treatment that eradicates the cancer.”
[googlead tip=”lista_mare” aliniat=”stanga”]Dr. David Porter cautioned that these were preliminary results and the scientists plan to continue the trial, treating more patients and following them over longer periods.
“The researchers also would like to expand the work to other tumor types and diseases,” Porter said.
The hope, scientists said, is that the method would work for cancers that can kill more ruthlessly and rapidly.