A new discovery may offer a glimmer of hope to patients with one of the deadliest cancers, research has shown.
Scientists have identified a previously unknown faulty gene that appears to play a key role in some aggressive forms of pancreatic cancer.
But studies suggest the defect could be fixed using experimental drugs which have already shown promise in lung cancer.
The gene, called USP9x, could be affected in around one in seven pancreatic cancers.
Research on human cell lines and mice have shown that the gene is switched off by chemical "tags" on the surface of its DNA.
Lead scientist Professor David Tuveson, from Cancer Research UK's Cambridge Research Institute, said: "Drugs which strip away these tags are already showing promise in lung cancer and this study suggests they could also be effective in treating up to 15% of pancreatic cancers."
The research is reported in the latest online edition of the journal Nature.
Pancreatic cancer kills around 8,000 people in the UK each year. Although survival rates are improving, fewer than one in five patients survive more than a year after diagnosis.
The scientists screened a mouse version of pancreatic cancer for genes that sped up cancer growth.
They uncovered many genes already known to be involved in the disease. But surprisingly, the most common gene fault was one with no previous links to any cancer type.
Prof Tuveson said: "The genetics of pancreatic cancer has already been studied in some detail, so we were surprised to find that this gene hadn't been picked up before.
"We suspected that the fault wasn't in the genetic code at all, but in the chemical tags on the surface of the DNA that switch genes on and off, and by running more lab tests we were able to confirm this."
Colleague Dr David Adams, from the Wellcome Trust Sanger Institute in Hinxton, Cambridgeshire, said: "The human genome sequence has delivered many new promising leads and transformed our understanding of cancer. Without it, we would have only a small, shattered glimpse into the causes of this disease. This study strengthens our emerging understanding that we must also look into the biology of cells to identify all the genes that play a role in cancer."
Dr Julie Sharp, senior science information manager at Cancer Research UK, said: "These results raise the possibility that a class of promising new cancer drugs may be effective at treating some pancreatic cancers.
"Fewer than 20% of people survive pancreatic cancer for a year after diagnosis - a situation that has improved little in the last 20 years. Studies like this one are part of Cancer Research UK's commitment to invest more in hard-to-treat cancers like pancreatic cancer, hopefully improving treatment to save more lives in the future."