Scientists discovered the molecule which helps to repair the body after chemotherapy or radiotherapy, known as focal adhesion kinase (FAK), was actually helping to shield the deadly cells from the treatment.
The Cancer Research UK team at Barts Cancer Institute, London, found when they removed FAK from blood vessels in certain cancer models, chemotherapy and radiation therapies were more effective.
The researchers also studied samples taken from lymphoma patients. Those with low levels of FAK were more likely to have complete remission after treatment.
The findings suggest that developing drugs to eliminate FAK in cancer blood vessels may boost treatments and prevent the cancer from recurring.
Dr Bernardo Tavora, lead author on the paper from the Barts Cancer Institute, said: "This work shows sensitivity to cancer treatment is related to our own body mistakenly trying to shield the cancer from cell-killing effects."
The findings have been published in Nature.