Gemcitabine and 5‐FU disrupt nuclear transport and subsequent localization of p21, p27 and p53 in cancer cells

Abstract

Altered nuclear transport plays a role in the mislocalization of tumor suppressor proteins in certain cancers. In addition, the disruption of nuclear transport and the nuclear pore complex during apoptosis are important mechanisms of action in several different chemotherapies. We previously demonstrated that the chemotherapy 5‐Fluorouracil (5‐FU) alters nuclear transport by disrupting the Ran gradient and increasing nuclear pore permeability. This block in nuclear transport may be advantageous to overcome Crm1‐induced excessive nuclear export in some cancers or with certain cases of drug resistance. Other work has shown that an additional chemotherapy, gemcitabine, is more effective when in combination with Crm1 inhibition. Therefore, we were interested in determining if gemcitabine and 5‐FU work effectively alone and in combination to disrupt nuclear transport via mislocalization of the transport protein Ran. We utilized immunofluorescence to determine the localization of Ran, which is normally localized to the nucleus. We show here that while each of these drugs mislocalized Ran at both 6h and 24h time points, and that gemcitabine counteracts the effects of 5‐FU in combination treatments to induce no change in Ran localization. This may be due to gemcitabine inhibiting 5‐FU's calcium‐mediated mechanism for inducing nuclear pore permeability. Additionally, we were interested in determining how these drugs affected the localization of three cargo proteins regulated by Crm1‐mediated export: p53, p27 and p21. These proteins have important function in the nucleus to control cell cycle progression and induction of apoptosis. Therefore, inhibition of Crm1 export should lead to nuclear accumulation of these factors and a potential increase in their function as tumor suppressors. We show here that 5‐FU and gemcitabine have opposing effects on the nuclear localization of both p53 and p21, and that the drugs again have counteractive effects when in combination treatments. Both 5‐FU and gemcitabine decrease the nuclear localization and expression of p27, while the combination treatment shows an additive effect on both localization and expression. The effects of these drugs on protein localization may be related to an additional block in nuclear import, as well as an induction of nuclear pore permeability downstream of the induction of apoptosis. Further research will help to characterize the effects of 5‐FU and gemcitabine on nuclear transport and subsequent protein localization. This may help to determine how these drugs may be more effectively used in the treatment of specific cancers and in specific drug combinations.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.