This image compares the infiltration of immune cells (magenta and green) between two mirrored mouse lung tumors. The left tumor shows high immune cell infiltration, which is associated with a better response after immunotherapy. On the contrary, the right tumor, shows almost no immune cell infiltration. These tumors were generated using identical lung adenocarcinoma cell lines that were engineered to differentially express one gene, indicating the profound impact that different mutations in tumor cells can have on the anti-tumor immune response. Understanding how different genes in cancer cells modulate the immune system will help us to develop new targeted therapies that will improve responses to immunotherapy.