CRM1

CRM1 (Chromosome region maintenance 1; Exportin 1; XPO1), a member of the karyopherin β family of transport receptors, is an important nuclear protein export receptor that recognizes hydrophobic, leucine-rich nuclear export signal (NES) and transports target proteins across a Ran-GTP gradient. CRM1 is involved in the active transport of a number of cargo proteins, including transcription factors, tumor suppressor proteins (TSPs), and cell-cycle regulators, such as p53, p21, p27, nucleophosmin 1 (NPM1), as well as RNA molecules.

Abnormal CRM1 upregulation can have several cancer-promoting consequences. Upregulation of CRM1 would allow more growth regulatory proteins, such as c-myc or BCR-ABL, to be transported into the cytoplasm and activate downstream signaling leading to sustained cell proliferation. Similarly, tumor suppressor proteins (TSPs), such as Rb, p53, p21, or p27, are functionally inactivated upon export, hence removing the check on inappropriate cell growth. Similar disruptions would occur in the processes of apoptosis, DNA damage repair, chromosomal stabilization, and angiogenesis, just to name a few examples. Hence, inhibition of CRM1 activity became an attractive therapeutic target.