Acquired small cell lung cancer resistance to Chk1 inhibitors involves Wee1 up-regulation.

Xiaoliang Zhao,Eiji Iwama,Bhaskar Kallakury,Yu‐Wen Zhang,Vincent Chen,Giuseppe Giaccone,Shigeki Umemura,Mariaelena Pierobon,In‐Kyu Kim,Emanuel Petricoin,Joeffrey J Chahine,Justine N Mccutcheon,Changli Wang

doi:10.1002/1878-0261.12882

Abstract

Platinum‐based chemotherapy has been the cornerstone treatment for small cell lung cancer (SCLC) for decades, but no major progress has been made in the past 20 years with regard to overcoming chemoresistance. As the cell cycle checkpoint kinase 1 (Chk1) plays a key role in DNA damage response to chemotherapeutic drugs, we explored the mechanisms of acquired drug resistance to the Chk1 inhibitor prexasertib in SCLC. We established prexasertib resistance in two SCLC cell lines and found that DNA copy number, messengerRNA (mRNA) and protein levels of the cell cycle regulator Wee1 significantly correlate with the level of acquired resistance. Wee1 small interfering RNA (siRNA) or Wee1 inhibitor reversed prexasertib resistance, whereas Wee1 transfection induced prexasertib resistance in parental cells. Reverse phase protein microarray identified up‐regulated proteins in the resistant cell lines that are involved in apoptosis, cell proliferation and cell cycle. Down‐regulation of CDK1 and CDC25C kinases promoted acquired resistance in parental cells, whereas down‐regulation of p38MAPK reversed the resistance. High Wee1 expression was significantly correlated with better prognosis of resected SCLC patients. Our results indicate that Wee1 overexpression plays an important role in acquired resistance to Chk1 inhibition. We also show that bypass activation of the p38MAPK signaling pathway may contribute to acquired resistance to Chk1 inhibition. The combination of Chk1 and Wee1 inhibitors may provide a new therapeutic strategy for the treatment of SCLC.

Highlights

Small cell lung cancer (SCLC) harbors very frequent mutations in p53 and Rb, which are key cell cycle regulators in normal cells [1,2]
In the absence of p53 suppressor activity, SCLC cells mainly rely on the Ataxia Telangiectasia and Rad3 (ATR)-Checkpoint Kinase 1 (Chk1) pathway to overcome replication stress in the event of DNA damage [3,4]
As Chk1 inhibition leads to apoptosis in S phase [25,26], prexasertib treatment caused significant cell cycle arrest in S phase in the parental cells, at the cost of significant reduction in G0/G1 cells, followed by a relative increase in the G2/M phase at later time points; in the resistant cells, there was no significant difference between untreated and treated cells and the percentage of cells in the different phases remains relatively stable (Fig. 1E,F)

Summary

Introduction

Small cell lung cancer (SCLC) harbors very frequent mutations in p53 and Rb, which are key cell cycle regulators in normal cells [1,2]. In the absence of p53 suppressor activity, SCLC cells mainly rely on the Ataxia Telangiectasia and Rad (ATR)-Checkpoint Kinase 1 (Chk1) pathway to overcome replication stress in the event of DNA damage [3,4]. Chk is a vital serine/threonine protein kinase that is responsible for cell cycle checkpoint-mediated DNA damage response [5]. Studies showed that Chk regulates the firing of dormant origins [4], which are initiation zones or clusters of DNA replication [7]. In p53-intact normal or cancer cells, DNA damage can activate p53, which protects cells from premature cell cycle progression caused by Chk inhibition [12,13]. Byers and colleagues have presented promising results using Chk inhibition alone or combined with cisplatin in SCLC xenograft models [15]

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Conclusion