Resistant subpopulation linked to leukaemia relapse

Australian scientists have identified leukaemia cells responsible for causing relapse after treatment in the most common form of childhood cancer.

Researchers led by Professor Murray Norris in the molecular diagnostics program at the Children's Cancer Institute in Sydney used PCR to characterise the small population of unique leukaemia cells responsible for relapse in patients diagnosed with acute lymphoblastic leukaemia (ALL), the most common cancer in children.

Approximately 20 per cent of children with ALL will experience a relapse of their disease following treatment. Of these, most will never be cured.

"We have previously shown that these relapses were due to small numbers of cells which survived the treatment administered to the patient," Norris said. "However, it has been unclear whether these cells developed resistance to chemotherapy during the course of treatment or if they were already present in the child at the time their cancer was diagnosed."

The findings of the study demonstrate that relapse in ALL patients can result from a minor, but intrinsically resistant subpopulation of cells, present from the time of diagnosis.

Undetected at diagnosis because of their very small numbers, this population of leukaemia cells remained in the patient's body throughout the disease and continued to thrive even after the major population of sensitive leukaemia cells were destroyed and the patient appeared to have gone into remission.

"We have shown, for the first time, that children with a greater number of these cells at diagnosis are more likely to experience relapse much sooner after treatment," he said.

"Without new strategies to identify and attack these cells early in treatment, relapse appears inevitable for these patients.

"Our ability to characterise these cells means that researchers can now develop treatments which specifically target the cells and are more effective than current options."

The results will be published in the journal Blood and is available online at http://bloodjournal.hematologylibrary.org/papbyrecent.dtl

Source: Children's Cancer Institute Australia