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14-3-3? inhibits heme oxygenase-1 (HO-1) degradation and promotes hepatocellular carcinoma proliferation: involvement of STAT3 signaling.

ABSTRACT: BACKGROUND:Heme oxygenase 1 (HO-1) has been reported to be very important in the pathogenesis or progression of multiple types of cancer. Identification of novel hmox1 binding proteins may reveal undefined oncogenes, tumor suppressors, signaling pathways, and possible treatment targets. METHODS:Immunoprecipitation and mass spectrometry analyses were used to identify novel regulators of HO-1. The association of the 14-3-3? protein with HO-1 and modulation of the stability of HO-1 were investigated by co-immunoprecipitation, immunofluorescence, western blotting, and quantitative RT-PCR. Degradation and in vivo ubiquitination assays were utilized to examine whether 14-3-3? stabilizes the HO-1 protein by inhibiting its ubiquitination. The effect of 14-3-3? on proliferation was investigated by function assays conducted in vitro using the CCK-8 and colony formation assays and in vivo in a xenograft mouse model. The biological functions of the 14-3-3?/HO-1 axis were demonstrated by western blotting and rescue experiments. Using gain-of-function and loss-of-function strategies, we further clarified the impact of 14-3-3?/HO-1 complex on the signal transducers and activators of transcription 3 (STAT3) signaling pathway in cancer cells. RESULTS:We identified 14-3-3? as a novel HO-1 binding protein. The binding inhibited the ubiquitination and proteasome-mediated degradation of HO-1, thus facilitating its stabilization. Enforced expression of 14-3-3? significantly promoted cell proliferation in vitro, as well as tumorigenesis in vivo, while 14-3-3? knockdown had opposite effects. The data indicated that 14-3-3? can stabilize HO-1 expression and thus influence cancer cell proliferation. We further demonstrated the involvement of the STAT3 pathway in 14-3-3?/HO-1 regulation of hepatocellular carcinoma cell proliferation. CONCLUSIONS:Collectively, these data show that 14-3-3? regulates the stability of HO-1 to promote cancer cell proliferation and STAT3 signaling activation. The data establish the 14-3-3?-HO-1-STAT3 axis as an important regulatory mechanism of cancer cell growth and implicate HO-1 and 14-3-3? as potential therapeutic targets in hepatocellular carcinoma.

SUBMITTER: Song J

PROVIDER: S-EPMC6319010 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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14-3-3ζ inhibits heme oxygenase-1 (HO-1) degradation and promotes hepatocellular carcinoma proliferation: involvement of STAT3 signaling.

Song Jia J Zhang Xiaochao X Liao Zhibin Z Liang Huifang H Chu Liang L Dong Wei W Zhang Xuewu X Ge Qianyun Q Liu Qiumeng Q Fan Pan P Zhang Zhanguo Z Zhang Bixiang B

Journal of experimental & clinical cancer research : CR 20190103 1

<h4>Background</h4>Heme oxygenase 1 (HO-1) has been reported to be very important in the pathogenesis or progression of multiple types of cancer. Identification of novel hmox1 binding proteins may reveal undefined oncogenes, tumor suppressors, signaling pathways, and possible treatment targets.<h4>Methods</h4>Immunoprecipitation and mass spectrometry analyses were used to identify novel regulators of HO-1. The association of the 14-3-3ζ protein with HO-1 and modulation of the stability of HO-1 w ...[more]

PMID: 30606233

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Project description:Heme oxygenase (HO), in conjunction with biliverdin reductase, degrades heme to carbon monoxide, ferrous iron and bilirubin (BR); the latter is a potent antioxidant. The induced isoform HO-1 has evoked intense research interest, especially because it manifests anti-inflammatory and anti-apoptotic effects relieving acute cell stress. The mechanisms by which HO mediates the described effects are not completely clear. However, the degradation of heme, a strong pro-oxidant, and the generation of BR are considered to play key roles. The aim of this study was to determine the effects of BR on vital functions of hepatocytes focusing on mitochondria and the endoplasmic reticulum (ER). The affinity of BR to proteins is a known challenge for its exact quantification. We consider two major consequences of this affinity, namely possible analytical errors in the determination of HO activity, and biological effects of BR due to direct interaction with protein function. In order to overcome analytical bias we applied a polynomial correction accounting for the loss of BR due to its adsorption to proteins. To identify potential intracellular targets of BR we used an in vitro approach involving hepatocytes and isolated mitochondria. After verification that the hepatocytes possess HO activity at a similar level as liver tissue by using our improved post-extraction spectroscopic assay, we elucidated the effects of increased HO activity and the formed BR on mitochondrial function and the ER stress response. Our data show that BR may compromise cellular metabolism and proliferation via induction of ER stress. ER and mitochondria respond differently to elevated levels of BR and HO-activity. Mitochondria are susceptible to hemin, but active HO protects them against hemin-induced toxicity. BR at slightly elevated levels induces a stress response at the ER, resulting in a decreased proliferative and metabolic activity of hepatocytes. However, the proteins that are targeted by BR still have to be identified.

Dataset Information

14-3-3? inhibits heme oxygenase-1 (HO-1) degradation and promotes hepatocellular carcinoma proliferation: involvement of STAT3 signaling.

Publications

14-3-3ζ inhibits heme oxygenase-1 (HO-1) degradation and promotes hepatocellular carcinoma proliferation: involvement of STAT3 signaling.

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