Stem cells could shield healthy tissue from chemotherapy

Stem cells transplanted into the brain may offer protection against the side effects of chemotherapy, say US researchers.

A study involving three patients with glioblastoma, an aggressive form of brain cancer, isolated stem cells extracted from the patients' bone marrow. Using a virus, a gene was inserted into the stem cells' DNA which protected the cells against the side effects of a chemotherapy drug. The cells were then put back into the patient.

The three patients survived an average of 22 months - the average survival for patients with the type of glioblastoma is just one year.

'We found that patients were able to tolerate the chemotherapy better and without negative side effects after transplantation of the gene-modified stem cells', said Professor Hans-Peter Kiem at the Fred Hutchinson Cancer Research Center, Seattle, which carried out the study. 'This compares with patients in previous studies who received the same type of chemotherapy without a transplant of gene-modified stem cells'.

Many types of glioblastoma are resistant to a chemotherapy agent, temozolomide, because they possess a gene called MGMT that repairs the damaged cancer cells. Patients are given benzylguanine to block this gene, but the side-effect is that the drug also makes healthy bone marrow cells sensitive to damage. 'Without those cells, patients become very susceptible to infections', explained Professor Kiem. 'Then they can't get the appropriate amount of chemotherapy because they have to stop treatment'.

By reintroducing the patients' bone marrow cells with a modified version of MGMT, called P140K, the cells are protected from both benzylguanine and the effects of chemotherapy. 'P140K can repair the damage caused by chemotherapy and is impervious to the effects of benzylguanine', said Professor Kiem.

Professor Susan Short of Cancer Research UK said: 'This is a very interesting study and a completely new approach to protecting normal cells during cancer treatment'.

'It needs to be tested in more patients but it may mean that we can use temozolomide for more brain tumour patients than we previously thought', Professor Short continued. 'This approach could also be a model for other situations where the bone marrow is affected by cancer treatment'.