Many proteins require transport across the nuclear envelope, the physical barrier separating the nucleus from the cytoplasm. Karyopherin β (Kpnβ1) proteins are the major nuclear receptor proteins in the cell that cargo proteins across the nuclear envelope, allowing them to enter and exit the cell nucleus. Karyopherin β1, a major nuclear import receptor, plays an integral role in importing transcription factors, cell signaling proteins, cell cycle proteins, and so forth, into the nucleus, thus playing a crucial role in maintaining normal cell homeostasis. However, cancer cells appear to differentially regulate the expression of the Karyopherin β proteins, presumably in order to maintain increased nuclear transport rates, thus implicating this protein family as a target for cancer therapy. The role of Kpnβ1 in cancer is only now being elucidated, and recent work points to its potential usefulness as an anti-cancer target.