The strain of chemotherapy can cause the body to activate stress defences which then shield cancer cells, a study has discovered.
The findings, which are reported in the journal Cell, provide further evidence that inflammation caused as part of the immune response is linked with cancer.
Scientists conducted the study by treating mice that had lymphoma with a chemotherapy drug.
They found that the lymphoma, an organ where immune cells mature, became a refuge to some tumour cells.
From within the lymphoma they were shielded from the drug by an “anti-stress” immune system molecule generated by healthy cells.
The signalling molecule, interleukin-6 (IL-6), allowed the cancer cells to persist in the thymus.
Further experiments showed that human liver cancer cells exposed to the chemotherapy agent doxorubicin also produced IL-6.
When chemotherapy was combined with a treatment that blocked IL-6, the cancer cells were more likely to die.
IL-6 is already linked to harmful inflammation and autoimmune conditions. Anti-IL-6 therapies are now in development for treating patients with rheumatoid arthritis.
Researcher Dr Michael Hemann, from Massachusetts Institute of Technology in Boston, US, said the findings made sense from the point of view of organ survival in the face of stress.
To maintain itself, an organ had to respond to stressful conditions, he pointed out. He added: “In this case, the stress response is to chemo. The chemotherapy kills tumour cells while it elicits stress responses that protect a subset of tumour cells in select locations from drug action.”
Copyright Press Association 2010