Cytoplasmic p21 Mediates 5-Fluorouracil Resistance by Inhibiting Pro-Apoptotic Chk2.

Arnatchai Maiuthed,Arnatchai Maiuthed,Benardina Ndreshkjana,Pithi Chanvorachote,Adriana Vial Roehe,Husayn Ahmed P,Katharina Erlenbach-Wuensch,Arndt Hartmann,Julienne Muenzner,Aylin Caliskan,Vijayalakshmi Mahadevan,Chatchai Chaotham,Chuanpit Ninsontia,Regine Schneider-Stock,Chuanpit Ninsontia

doi:10.3390/cancers10100373

Abstract

The oncogenic cytoplasmic p21 contributes to cancer aggressiveness and chemotherapeutic failure. However, the molecular mechanisms remain obscure. Here, we show for the first time that cytoplasmic p21 mediates 5-Fluorouracil (5FU) resistance by shuttling p-Chk2 out of the nucleus to protect the tumor cells from its pro-apoptotic functions. We observed that cytoplasmic p21 levels were up-regulated in 5FU-resistant colorectal cancer cells in vitro and the in vivo Chorioallantoic membrane (CAM) model. Kinase array analysis revealed that p-Chk2 is a key target of cytoplasmic p21. Importantly, cytoplasmic form of p21 mediated by p21T145D transfection diminished p-Chk2-mediated activation of E2F1 and apoptosis induction. Co-immunoprecipitation, immunofluorescence, and proximity ligation assay showed that p21 forms a complex with p-Chk2 under 5FU exposure. Using in silico computer modeling, we suggest that the p21/p-Chk2 interaction hindered the nuclear localization signal of p-Chk2, and therefore, the complex is exported out of the nucleus. These findings unravel a novel mechanism regarding an oncogenic role of p21 in regulation of resistance to 5FU-based chemotherapy. We suggest a possible value of cytoplasmic p21 as a prognosis marker and a therapeutic target in colorectal cancer patients.

Highlights

The oncogenic cytoplasmic p21 contributes to cancer aggressiveness and chemotherapeutic failure
Our present study has identified pChk2T68 as a novel interaction partner of cytoplasmic p21 that seems to confer to 5FU resistance in colorectal cancer (CRC)
To define a suitable experimental model for investigation of the role of p21 for 5FU resistance, we evaluated the susceptibility to 5FU treatment in three different colorectal tumor cell lines (HCT116, HT29 and SW837)

Summary

Introduction

The oncogenic cytoplasmic p21 contributes to cancer aggressiveness and chemotherapeutic failure. We show for the first time that cytoplasmic p21 mediates 5-Fluorouracil (5FU) resistance by shuttling p-Chk out of the nucleus to protect the tumor cells from its pro-apoptotic functions. Using in silico computer modeling, we suggest that the p21/p-Chk interaction hindered the nuclear localization signal of p-Chk, and the complex is exported out of the nucleus. These findings unravel a novel mechanism regarding an oncogenic role of p21 in regulation of resistance to 5FU-based chemotherapy. Accumulating evidence has suggested that p21 may play an oncogenic role In this regard, high expression levels of p21 in many cancer types are correlated with tumor progression [7,8,9,10,11]. Cytoplasmic p21 has been shown to mediate cisplatin and paclitaxel resistance in various cancers [23,24,25]

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Conclusion