Selective targeting of KRAS-driven lung tumorigenesis via unresolved ER stress
Iwao Shimomura, Naoaki Watanabe, Tomofumi Yamamoto, Minami Kumazaki, Yuji Tada, Koichiro Tatsumi, Takahiro Ochiya, Yusuke Yamamoto
Iwao Shimomura, Naoaki Watanabe, Tomofumi Yamamoto, Minami Kumazaki, Yuji Tada, Koichiro Tatsumi, Takahiro Ochiya, Yusuke Yamamoto
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Research Article Cell biology Oncology

Selective targeting of KRAS-driven lung tumorigenesis via unresolved ER stress

Abstract

Lung cancer with oncogenic KRAS makes up a significant proportion of lung cancers and is accompanied by a poor prognosis. Recent advances in understanding the molecular pathogenesis of lung cancer with oncogenic KRAS have enabled the development of drugs, yet mutated KRAS remains undruggable. We performed small-molecule library screening and identified verteporfin, a yes-associated protein 1 (YAP1) inhibitor; verteporfin treatment markedly reduced cell viability in KRAS-mutant lung cancer cells in vitro and suppressed KRAS-driven lung tumorigenesis in vivo. Comparative functional analysis of verteporfin treatment and YAP1 knockdown with siRNA revealed that the cytotoxic effect of verteporfin was at least partially independent of YAP1 inhibition. A whole-transcriptome approach revealed the distinct expression profiles in KRAS-mutant lung cancer cells between verteporfin treatment and YAP1 knockdown and identified the selective involvement of the ER stress pathway in the effects of verteporfin treatment in KRAS-mutant lung cancer, leading to apoptotic cell death. These data provide novel insight to uncover vulnerabilities in KRAS-driven lung tumorigenesis.

Authors

Iwao Shimomura, Naoaki Watanabe, Tomofumi Yamamoto, Minami Kumazaki, Yuji Tada, Koichiro Tatsumi, Takahiro Ochiya, Yusuke Yamamoto

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Figure 6

Characterization of unresolved ER stress mechanism in KRAS-mutant lung cancer cells by verteporfin treatment.

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Characterization of unresolved ER stress mechanism in KRAS-mutant lung c...
(A) Relative expression analysis of leading genes in ER stress pathways in KRAS-mutant cells treated with verteporfin or YAP1 knockdown by RNA-Seq. (B) Relative expression analysis of leading genes in ER stress pathways in KRAS-mutant and WT cells treated with verteporfin (control and 10 μM) determined by quantitative reverse transcription PCR. The values are the mean ± SD (3 KRAS-mutant cell lines [A-549, H-23 and H-1573] and 3 WT cell lines [H-1650, H-522 and Calu-3], each n = 3). Statistical significance was determined using an unpaired 2-tailed Student’s t test. *, P < 0.05. (C) Characterization of unspliced XBP1 (uXBP1) and spliced XBP1 (sXBP1) in KRAS-mutant and WT cells treated by verteporfin in various concentrations. The normalization control was performed by total XBP1 (tXBP1). The values are the mean ± SD (n = 3). (D) Effects of combination therapy of verteporfin and TUDCA (ER stress inhibitor) in KRAS-mutant cells. The results of combination therapy of eeyarestatin (ERAD inhibitor) and TUDCA are shown as a control. E, eeyarestatin. The values are the mean ± SD (n = 3). Statistical significance was determined using an unpaired 2-tailed Student’s t test. **, P < 0.01 and ***, P < 0.001. FPKM, fragments per kilobase per million mapped reads.