Mechanism produces resistance to lung cancer drugs

Researchers have identified a new mechanism that provokes resistance to certain lung cancer drugs, which may exist in other types of cancerous tumors, according to a study published Thursday in the United States.

The international team of scientists, in a report to appear in the April 27 issue of the journal Science and released online in advance, said their findings suggest a treatment strategy for patients with the resistant tumors.

The mechanism was discovered in about 20 percent of patients with tumors that became resistant to Tarceva or Iressa, two commonly used targeted therapy drugs in the United States, said Jeffrey Engelman of Massachusetts General Hospital, the paper's lead author.
The resistance was "caused by the genetic activation of an oncogene that is not the normal target of the drug, which is something that has never been seen before," Engelman said.

Tarceva (eriotinib) and Iressa (gefitinib) are used to treat advanced types of lung cancer, the leading cause of cancer deaths in the United States.

"We also identified a potential new way to treat these resistant tumors with combination therapy directed against both protein targets," said Pasi Jaenne of the Dana-Farber Cancer Institute in Boston, Massachusetts, the study's senior author.

The drugs act by blocking a growth factor receptor, a molecule on the surface of cancer cells.