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Identification of Doxorubicin as an Inhibitor of the IRE1?-XBP1 Axis of the Unfolded Protein Response.

ABSTRACT: Activation of the IRE1?-XBP1 branch of the unfolded protein response (UPR) has been implicated in multiple types of human cancers, including multiple myeloma (MM). Through an in silico drug discovery approach based on protein-compound virtual docking, we identified the anthracycline antibiotic doxorubicin as an in vitro and in vivo inhibitor of XBP1 activation, a previously unknown activity for this widely utilized cancer chemotherapeutic drug. Through a series of mechanistic and phenotypic studies, we showed that this novel activity of doxorubicin was not due to inhibition of topoisomerase II (Topo II). Consistent with its inhibitory activity on the IRE1?-XBP1 branch of the UPR, doxorubicin displayed more potent cytotoxicity against MM cell lines than other cancer cell lines that have lower basal IRE1?-XBP1 activity. In addition, doxorubicin significantly inhibited XBP1 activation in CD138(+) tumor cells isolated from MM patients. Our findings suggest that the UPR-modulating activity of doxorubicin may be utilized clinically to target IRE1?-XBP1-dependent tumors such as MM.

SUBMITTER: Jiang D

PROVIDER: S-EPMC5025885 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

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Identification of Doxorubicin as an Inhibitor of the IRE1α-XBP1 Axis of the Unfolded Protein Response.

Jiang Dadi D Lynch Connor C Medeiros Bruno C BC Liedtke Michaela M Bam Rakesh R Tam Arvin B AB Yang Zhifen Z Alagappan Muthuraman M Abidi Parveen P Le Quynh-Thu QT Giaccia Amato J AJ Denko Nicholas C NC Niwa Maho M Koong Albert C AC

Scientific reports 20160916

Activation of the IRE1α-XBP1 branch of the unfolded protein response (UPR) has been implicated in multiple types of human cancers, including multiple myeloma (MM). Through an in silico drug discovery approach based on protein-compound virtual docking, we identified the anthracycline antibiotic doxorubicin as an in vitro and in vivo inhibitor of XBP1 activation, a previously unknown activity for this widely utilized cancer chemotherapeutic drug. Through a series of mechanistic and phenotypic stud ...[more]

PMID: 27634301

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Project description:BACKGROUND:Many viruses depend on the extensive membranous network of the endoplasmic reticulum (ER) for their translation, replication, and packaging. Certain membrane modifications of the ER can be a trigger for ER stress, as well as the accumulation of viral protein in the ER by viral infection. Then, unfolded protein response (UPR) is activated to alleviate the stress. Zika virus (ZIKV) is a mosquito-borne flavivirus and its infection causes microcephaly in newborns and serious neurological complications in adults. Here, we investigated ER stress and the regulating model of UPR in ZIKV-infected neural cells in vitro and in vivo. METHODS:Mice deficient in type I and II IFN receptors were infected with ZIKV via intraperitoneal injection and the nervous tissues of the mice were assayed at 5 days post-infection. The expression of phospho-IRE1, XBP1, and ATF6 which were the key markers of ER stress were analyzed by immunohistochemistry assay in vivo. Additionally, the nuclear localization of XBP1s and ATF6n were analyzed by immunohistofluorescence. Furthermore, two representative neural cells, neuroblastoma cell line (SK-N-SH) and astrocytoma cell line (CCF-STTG1), were selected to verify the ER stress in vitro. The expression of BIP, phospho-elF2?, phospho-IRE1, and ATF6 were analyzed through western blot and the nuclear localization of XBP1s was performed by confocal immunofluorescence microscopy. RT-qPCR was also used to quantify the mRNA level of the UPR downstream genes in vitro and in vivo. RESULTS:ZIKV infection significantly upregulated the expression of ER stress markers in vitro and in vivo. Phospho-IRE1 and XBP1 expression significantly increased in the cerebellum and mesocephalon, while ATF6 expression significantly increased in the mesocephalon. ATF6n and XBP1s were translocated into the cell nucleus. The levels of BIP, ATF6, phospho-elf2?, and spliced xbp1 also significantly increased in vitro. Furthermore, the downstream genes of UPR were detected to investigate the regulating model of the UPR during ZIKV infection in vitro and in vivo. The transcriptional levels of atf4, gadd34, chop, and edem-1 in vivo and that of gadd34 and chop in vitro significantly increased. CONCLUSION:Findings in this study demonstrated that ZIKV infection activates ER stress in neural cells. The results offer clues to further study the mechanism of neuropathogenesis caused by ZIKV infection.

Dataset Information

Identification of Doxorubicin as an Inhibitor of the IRE1?-XBP1 Axis of the Unfolded Protein Response.

Publications

Identification of Doxorubicin as an Inhibitor of the IRE1α-XBP1 Axis of the Unfolded Protein Response.

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