HIF-1α promotes autophagic proteolysis of Dicer and enhances tumor metastasis
Hui-Huang Lai, … , Hiroshi I. Suzuki, Pai-Sheng Chen
Hui-Huang Lai, … , Hiroshi I. Suzuki, Pai-Sheng Chen
Published December 18, 2017
Citation Information: J Clin Invest. 2018;128(2):625-643. https://doi.org/10.1172/JCI89212.
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Research Article Cell biology

HIF-1α promotes autophagic proteolysis of Dicer and enhances tumor metastasis

Abstract

HIF-1α, one of the most extensively studied oncogenes, is activated by a variety of microenvironmental factors. The resulting biological effects are thought to depend on its transcriptional activity. The RNAse enzyme Dicer is frequently downregulated in human cancers, which has been functionally linked to enhanced metastatic properties; however, current knowledge of the upstream mechanisms regulating Dicer is limited. In the present study, we identified Dicer as a HIF-1α–interacting protein in multiple types of cancer cell lines and different human tumors. HIF-1α downregulated Dicer expression by facilitating its ubiquitination by the E3 ligase Parkin, thereby enhancing autophagy-mediated degradation of Dicer, which further suppressed the maturation of known tumor suppressors, such as the microRNA let-7 and microRNA-200b. Consequently, expression of HIF-1α facilitated epithelial-mesenchymal transition (EMT) and metastasis in tumor-bearing mice. Thus, this study uncovered a connection between oncogenic HIF-1α and the tumor-suppressive Dicer. This function of HIF-1α is transcription independent and occurs through previously unrecognized protein interaction–mediated ubiquitination and autophagic proteolysis.

Authors

Hui-Huang Lai, Jie-Ning Li, Ming-Yang Wang, Hsin-Yi Huang, Carlo M. Croce, Hui-Lung Sun, Yu-Jhen Lyu, Jui-Wen Kang, Ching-Feng Chiu, Mien-Chie Hung, Hiroshi I. Suzuki, Pai-Sheng Chen

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Figure 1

HIF-1α interacts with Dicer in multiple human cancer cell lines and tumors.

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HIF-1α interacts with Dicer in multiple human cancer cell lines and tumo...
(A–D) Endogenous interaction between HIF-1α and Dicer. Immunoprecipitation of endogenous HIF-1α and Dicer were performed using anti–HIF-1α and anti-Dicer antibodies in HEK293T (A and B) and HCT116 cells (C and D). Ago2 was detected in anti–HIF-1α immunoprecipitates from HEK-293T cells. Lamin B1 was used as a loading control (B). (E and F) Immunoprecipitation analysis of the association between endogenous HIF-1α (E) or Myc–HIF-1α (F) and FLAG-Dicer in HCT116 cells. (G) BiFC of the association of VC115-fused HIF-1α and VN173-fused Dicer (top). HCT116 cells were transfected with VC155–HIF-1α, VN173-fused Dicer, or corresponding vector. (H–J) HIF-1α interacts with Dicer in tumor tissues. Anti–HIF-1α immunoprecipitates were isolated from lysates of surgically resected tumors to detect the in vivo interaction between HIF-1α and Dicer in colon (H) and breast (I) cancer tissues. The immunoblots presented were derived from replicate samples run on parallel gels (I). HIF-1α and Dicer were detected using in situ PLA in human colon, breast, lung, liver, and prostate normal and cancer tissues (J). PLA signals are shown in red along with DAPI nuclear staining (blue). Each red fluorescent dot indicates the direct binding of the HIF-1α/Dicer complex in close distance (<40 nm). Tissues stained with only anti–HIF-1α antibodies were also analyzed as negative controls shown in Supplemental Figure 1I. Data are presented as mean ± SD, with at least n = 3 per group. Multigroup comparisons were analyzed by 1-way ANOVA with Tukey’s post hoc test. ***P < 0.001.