Gene therapy can help breast cancer treatment work more effectively by delivering it directly to the tumour, scientists say.
The treatment could help tackle breast cancer
Tests have shown it can help a chemotherapy drug work more effectively and reduce the side-effects from the treatment.
The therapy could also help tackle other cancers, including pancreatic, ovarian and neck cancers.
Chemotherapy works by poisoning cancer cells and killing them.
But it can also kill healthy cells as well.
It is far too soon to know whether it will turn out to be an effective treatment for cancer patients.
Kate Law, Cancer Research UK
The researchers behind the new gene therapy say because the gene therapy helps the drug target the tumour directly, it should mean fewer healthy cells are killed.
The new treatment, called Metxia, is being developed by Oxford-based researchers.
It works in conjunction with the chemotherapy drug cyclophosphamide.
The drug is swallowed as a pill, but its cancer-killing properties are only activated by an enzyme in the liver.
Once "charged", cyclophosphamide then begins killing cells.
Metxia contains CYP-2B6, a gene normally found in liver cells.
This gene is injected directly into the tumour, which means the drug can be activated exactly where it is needed.
Trials of a low-dose of the therapy on four patients show it has been effective.
Patients' immune systems were prompted to attack cancer cells by the treatment.
Researchers found they were also able to deliver the therapeutic gene to tumour cells 10 times more effectively than in previous studies.
The scientists, from Oxford Biomedica, a spin-off company from Oxford University, say if trials of medium dose Metxia are as effective, it may be possible to stop the trial early.
Professor Alan Kingsman, who carried out the research told BBC News Online: "Metxia accelerates the killing of tumours by cyclophosphamide.
"We hope that Metxia will help cyclophosphamide act more effectively, but reduce side effects from the drug."
He added: "These results are very promising. If results continue to be as promising, we may be able to stop the trials early."
Gene therapy is a developing field and although there have been some significant advances, many experiments have failed - and some patients have died.
The government last week announced £5.5m of funding for gene therapy research.
Commenting on this latest research, Kate Law, head of clinical trials at Cancer Research UK, said: "This trial is an early stage study with only small numbers of patients being treated.
"These studies focus on safety and dose levels and it is therefore far too soon to know whether it will turn out to be an effective treatment for cancer patients.
"If, however, this type of targeted approach to treatment does turn out to be successful it is likely to result in more effective treatments which have fewer side effects than current chemotherapy."