The Karyopherin proteins, Crm1 and Karyopherin β1, are overexpressed in cervical cancer and are critical for cancer cell survival and proliferation

The Karyopherin proteins are involved in nucleo-cytoplasmic trafficking and are critical for protein anti RNA subcellular localization. Recent studies suggest they are important in nuclear envelope component assembly, mitosis and replication. Since these are all critical cellular functions, alterations in the expression of the Karyopherins may have an impact on the biology of cancer cells. In this study, we examined the expression of the Karyopherins, Crm1, Karyopherin beta 1 (Kpn beta 1) and Karyopherin alpha 2 (Kpn alpha 2), in cervical tissue and cell lines. The functional significance of these proteins to cancer cells was investigated using individual siRNAs to inhibit their expression. Microarrays, quantitative RT-PCR and immunofluorescence revealed significantly higher expression of Crm1, Kpn beta 1 and Kpn alpha 2 in cervical cancer compared to normal tissue. Expression levels were similarly elevated in cervical cancer cell lines compared to normal cells, and in transformed epithelial and fibroblast cells. Inhibition of Crm1. and Kpn beta 1 in cancer cells significantly reduced cell proliferation, while Kpn alpha 2 inhibition had no effect. Noncancer cells were unaffected by the inhibition or Crml and Kpn beta 1. The reduction in proliferation of cancer cells was associated with an increase in a subG1 population by cell cycle analysis and Caspase-3/7 assays revealed increased apoptosis. Crml and Kpn beta 1 siRNA-indticed apoptosis was accompanied by an increase in the levels of growth inhibitory proteins, p539 p27, p21 and p18. Our results demonstrate that Crm1, Kpn beta 1 and Kpn alpha 2 are overexpressed in cervical cancer and that inhibiting the expression of Crm1 and Kpn beta 1, not Kpn alpha 2, induces cancer cell death, making Crm1 and Kpn beta 1 promising candidates as both biomarkers and potential anticancer therapeutic targets, (C) 2008 Wiley-Liss, Inc,