Targeting the XIAP/caspase-7 complex selectively kills caspase-3–deficient malignancies
Yuan-Feng Lin, … , Michael Hsiao, Po-Huang Liang
Yuan-Feng Lin, … , Michael Hsiao, Po-Huang Liang
Published August 27, 2013
Citation Information: J Clin Invest. 2013;123(9):3861-3875. https://doi.org/10.1172/JCI67951.
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Research Article

Targeting the XIAP/caspase-7 complex selectively kills caspase-3–deficient malignancies

Abstract

Caspase-3 downregulation (CASP3/DR) in tumors frequently confers resistance to cancer therapy and is significantly correlated with a poor prognosis in cancer patients. Because CASP3/DR cancer cells rely heavily on the activity of caspase-7 (CASP7) to initiate apoptosis, inhibition of activated CASP7 (p19/p12-CASP7) by X-linked inhibitor of apoptosis protein (XIAP) is a potential mechanism by which apoptosis is prevented in those cancer cells. Here, we identify the pocket surrounding the Cys246 residue of p19/p12-CASP7 as a target for the development of a protein-protein interaction (PPI) inhibitor of the XIAP:p19/p12-CASP7 complex. Interrupting this PPI directly triggered CASP7-dependent apoptotic signaling that bypassed the activation of the apical caspases and selectively killed CASP3/DR malignancies in vitro and in vivo without adverse side effects in nontumor cells. Importantly, CASP3/DR combined with p19/p12-CASP7 accumulation correlated with the aggressive evolution of clinical malignancies and a poor prognosis in cancer patients. Moreover, targeting of this PPI effectively killed cancer cells with multidrug resistance due to microRNA let-7a-1–mediated CASP3/DR and resensitized cancer cells to chemotherapy-induced apoptosis. These findings not only provide an opportunity to treat CASP3/DR malignancies by targeting the XIAP:p19/p12-CASP7 complex, but also elucidate the molecular mechanism underlying CASP3/DR in cancers.

Authors

Yuan-Feng Lin, Tsung-Ching Lai, Chih-Kang Chang, Chi-Long Chen, Ming-Shyan Huang, Chih-Jen Yang, Hon-Ge Liu, Jhih-Jhong Dong, Yi-An Chou, Kuo-Hsun Teng, Shih-Hsun Chen, Wei-Ting Tian, Yi-Hua Jan, Michael Hsiao, Po-Huang Liang

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Figure 2

I-Lys directly triggers CASP7-mediated apoptotic signaling by disrupting the XIAP:p19/p12-CASP7 complex in MCF-7 cells.

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I-Lys directly triggers CASP7-mediated apoptotic signaling by disrupting...
(A) Determination of intracellular caspase activity in untreated (UT) MCF-7 cells or in MCF-7 cells treated with IDAM, N-acetyl-Lys, I-Lys, or STS (1 μM each) for 24 hours. (B) Immunoblotting for the full-length (FL) and cleaved forms of PARP in MCF-7 cells treated with 1 μM I-Lys for the indicated times. (C) Apoptosis in MCF-7 cells treated with 1 μM I-Lys for 24 hours in the presence or absence of the CASP7 inhibitor MPS or the PARP inhibitor IAB at the indicated doses. (D–F) Immunoblotting for pro-CASP7 and p19/p12-CASP7 (D), tracing p19/p12-CASP7 by biotin-VAD (E), and immunoprecipitation/Western blot analysis of XIAP:p19/p12-CASP7 complexes (F) in MCF-7 cells treated with I-Lys or STS (1 μM each) for the indicated times. (G) Real-time DEVDase activity in MCF-7 cells treated with I-Lys (1 μM), in the absence or presence of MPS (10 μM), or with STS (1 μM). I-Lys or STS were added to the medium 50 seconds after the onset of the experiment. Scale bar: 100 seconds. (A and C) Data are mean ± SEM.