The protein MDM2 starts destroying key cancer-preventing protein p53 due to a biochemical imbalance.
The scientists said that new drugs could work by stopping MDM2 become a cancer-promoting catalyst.
Head investigator Dr. Kathryn Ball said the study had also identified another template for new drugs.
"We have identified protein fragments which can bind to MDM2, inhibiting its activity," she told BBC. "These fragments could be a good template for drugs designed to hinder the role of MDM2 in the p53 destruction pathway."
Prof. John Toy, medical director at Cancer Research UK, the organization responsible for who sponsoring the study, said: "P53 is a crucial protein that acts as a guardian of the normal cell.
"Its failure to do its job properly is associated with many types of cancer," he added. "If p53 is being destroyed by another protein in a cancer cell, then it offers an excellent target when designing new anti-cancer drugs.
