Disclosed are compositions, kits, and methods for identifying genes that are involved in T-cell trafficking. In particular, the compositions, kits, and methods may be used to identify genes involved in T-cell trafficking and/or infiltration into tumors such as genes that encode immune checkpoint regulators and/or stimulatory agents. The disclosed compositions, kits, and methods utilize the Sleeping Beauty transposon system in a mouse tumor model to identify genes that are involved in T-cell trafficking and infiltration into tumors. The genes identified in the disclosed methods may provide immunotherapy targets in the tumor microenvironment. The identified genes may be utilized in order to develop therapies that enhance T-cell trafficking and infiltration into tumors and/or T-cell killing of tumors such as in chimeric antigen receptor (CAR) T cell therapies.