UT Southwestern Medical Center cancer researchers have found a molecule that selectively and irreversibly interferes with the activity of a mutated cancer gene common in 30 percent of tumors.The molecule, SML-8-73-1 (SML), interferes with the KRAS gene, or Kirsten rat sarcoma viral oncogene homolog. The gene produces proteins called K-Ras that influence when cells divide. Mutations in K-Ras can result in normal cells dividing uncontrollably and turning cancerous. These mutations are particularly found in cancers of the lung, pancreas, and colon. In addition, people who have the mutated gene are less responsive to therapy.