Lung cancer is the leading cause of cancer-related death worldwide, killing more than breast, prostate, colon, kidney, and liver cancer combined. Lung adenocarcinoma (LUAD), the most common type of lung cancer, alone kills ~60,000 Americans every year. Therefore, preventing lung cancer would have a large impact on society. Preventing lung cancer altogether would also address the problem of worse outcomes for patients who, for social and economic reasons, have unequal access to cutting-edge cancer treatment. Even patients who are cured of cancer experience psychological trauma, so prevention would also mean that no one would have to go through such a traumatic experience. Our initial results show that early lung cancers are less complex and therefore should be easier to eliminate compared to advanced disease that has spread from the lung to other parts of the body. We propose to study the earliest steps, when a normal lung cell becomes a cancer cell. To do this, we have developed a way to study lung cancer cells in the lab that closely resembles how tumors grow in humans. In addition to studying features of early lung tumor cells, we will also study the surroundings of these cells, a method that has not been used before to study lung cancer. We aim to discover molecular processes that are essential for the formation of lung cancer. Drugs could then be developed to block these processes and stop lung cancer at its earliest stages – preventing the disease altogether.