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Combinations of proteasome inhibitors with obatoclax are effective for small cell lung cancer


Proteasome inhibitors, bortezomib (BTZ), and carfilzomib (CFZ) are approved drugs for hematological malignancies, but lack anticancer activities against most solid tumors. Small cell lung cancer (SCLC) is a very aggressive neuroendocrine carcinoma of the lungs demanding effective therapy. In this study we investigated whether BTZ or CFZ combined with obatoclax (OBX), an antagonist for MCL-1 and a pan-BCL family inhibitor, could cause synergistic growth inhibition of SCLC cells. We showed that combined application of BTZ or CFZ with OBX caused synergistic growth inhibition of human SCLC cell lines (H82, H526, DMS79, H196, H1963, and H69) than single agent alone. Both BTZ–OBX and CFZ–OBX combinations displayed marked synergism on inducing apoptosis (~50% increase vs BTZ or CFZ alone). A comprehensive proteomics analysis revealed that BTZ preferentially induced the expression of MCL-1, an antiapoptotic protein, in SCLC cells. Thus, proteasome inhibitor–OBX combinations could specifically induce massive growth inhibition and apoptosis in SCLC cells. Subsequent proteome-wide profiling analysis of activated transcription factors suggested that BTZ- or CFZ-induced MCL-1 upregulation was transcriptionally driven by FOXM1. In nude mice bearing in SCLC H82 xenografts, both BTZ–OBX, and CFZ–OBX combinations exhibited remarkable antitumor activities against SCLC tumors evidenced by significant reduction of tumor size and the proliferation marker Ki-67 signals in tumor tissues as compared with single agent alone. Thus, proteasome inhibitor–OBX combinations are worth immediate assessments for SCLC in clinical settings.

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Fig. 1: BTZ treatment preferentially induced MCL-1 expression in SCLC cells.
Fig. 2: The BTZ–OBX combination caused synergistic growth inhibition in SCLC cells.
Fig. 3: The CFZ–OBX combination caused synergistic growth inhibition in SCLC cells.
Fig. 4: The BTZ–OBX and CFZ–OBX combinations induced synergistic apoptosis.
Fig. 5: BTZ and CFZ induced the transcription of MCL-1 rather than inhibiting its degradation.
Fig. 6: Proteome-wide profiling analysis of activated transcription factors indicated that HIF-1α and FOXM1 were preferentially induced by BTZ treatment.
Fig. 7: FOXM1 mediated the upregulation of MCL-1 by BTZ and CFZ.
Fig. 8: OBX enhanced the antitumor activity of BTZ or CFZ in vivo.
Fig. 9: Histologic analysis of tumors for cellular proliferation and apoptosis.

Data availability

Raw MS data were uploaded to iProX. These data can be accessed at the following url:;?url=1596784470810tGwJ (keywords, sDU3).


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This study was supported by the National Natural Science Foundation of China (Grant Numbers: 81672647, 81872438, 81502632, 81372214, and 81972191), Natural Science Foundation of Anhui Province (Grant Number: 1608085MH179), Science and Technology Major Project of Anhui Province (Grant Number: 18030801140) and 100-Talent Program of Chinese Academy of Sciences. A portion of this work was supported by the High Magnetic Field Laboratory of Anhui Province.

Author information




BH, WCL, and CD designed the study. YPY, BH, WHS, KD, and XLL performed the experiments. BH, YPY, WHS, HL, XTL, CD, and WCL analyzed and interpreted the data. YPY, BH and WHS wrote the manuscript. VWYL, WCL, and CD critically commented and edited the manuscript. All authors read and approved the final version of the manuscript.

Corresponding authors

Correspondence to Chen Ding or Bo Hong or Wen-chu Lin.

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The authors declare no competing interests.

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Yin, Yp., Shi, Wh., Deng, K. et al. Combinations of proteasome inhibitors with obatoclax are effective for small cell lung cancer. Acta Pharmacol Sin (2020).

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  • small cell lung cancer
  • obatoclax
  • bortezomib
  • carfilzomib
  • MCL-1
  • apoptosis
  • FOXM1
  • proteomics analysis


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