CDKN1B and cholangiocarcinoma: The inhibition of cholangiocarcinoma cell proliferation by p27kip1 can be attenuated by overexpression of RANBP2, which was attributed to the fact that SUMOylation of p27kip1 facilitates the nucleoplasmic translocation of p27kip1 and attenuates the G1 arrest brought about by the accumulation of p27kip1 in the nucleus.69