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Chromosome 8p tumor suppressor genes SH2D4A and SORBS3 cooperate to inhibit interleukin-6 signaling in hepatocellular carcinoma.

ABSTRACT: UNLABELLED:Several chronic inflammatory liver diseases, e.g., chronic hepatitis B or C viral infection and steatohepatitis, have been shown to predispose to the development of hepatocellular carcinoma (HCC). In patients with chronic liver disease, interleukin-6 (IL-6) serum levels are elevated and increase even more when HCC develops. However, the impact and regulatory mechanisms of IL-6 signaling during hepatocarcinogenesis are still poorly defined. Here, we show that gene expression profiles of patients with chromosome 8p loss correlate with increased IL-6 signaling. In addition, the chromosome 8p tumor suppressor genes Src homology 2 domain containing 4A (SH2D4A) and Sorbin and Src homology 3 domain containing 3 (SORBS3) together exerted greater inhibition of cell growth and clonogenicity compared to a single gene. Overexpression of SH2D4A and SORBS3 in HCC cells led to decreased IL-6 target gene expression and reduced signal transducer and activator of transcription 3 (STAT3) signaling. In situ and in vitro coimmunoprecipitation assays revealed that SH2D4A directly interacts with STAT3, thereby retaining STAT3 in the cytoplasm and inhibiting STAT3 transcriptional activity. On the other hand, SORBS3 coactivated estrogen receptor ? signaling, leading indirectly to repression of STAT3 signaling. In human HCC tissues, SH2D4A was positively associated with infiltrating regulatory and cytotoxic T-cell populations, suggesting distinct immunophenotypes in HCC subgroups with chromosome 8p loss. Thus, the genetically linked tumor suppressors SH2D4A and SORBS3 functionally cooperate to inhibit STAT3 signaling in HCC. CONCLUSION:The chromosome 8p tumor suppressor genes SORBS3 and SH2D4A are physically and functionally linked and provide a molecular mechanism of inhibiting STAT3-mediated IL-6 signaling in HCC cells. (Hepatology 2016;64:828-842).

SUBMITTER: Ploeger C

PROVIDER: S-EPMC5098049 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

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Chromosome 8p tumor suppressor genes SH2D4A and SORBS3 cooperate to inhibit interleukin-6 signaling in hepatocellular carcinoma.

Ploeger Carolin C Waldburger Nina N Fraas Angelika A Goeppert Benjamin B Pusch Stefan S Breuhahn Kai K Wang Xin Wei XW Schirmacher Peter P Roessler Stephanie S

Hepatology (Baltimore, Md.) 20160715 3

<h4>Unlabelled</h4>Several chronic inflammatory liver diseases, e.g., chronic hepatitis B or C viral infection and steatohepatitis, have been shown to predispose to the development of hepatocellular carcinoma (HCC). In patients with chronic liver disease, interleukin-6 (IL-6) serum levels are elevated and increase even more when HCC develops. However, the impact and regulatory mechanisms of IL-6 signaling during hepatocarcinogenesis are still poorly defined. Here, we show that gene expression pr ...[more]

PMID: 27311882

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Project description:Programmed cell death 4 (Pdcd4), a tumor invasion suppressor, is frequently downregulated in colorectal cancer and other cancers. In this study, we find that loss of Pdcd4 increases the activity of mammalian target of rapamycin complex 2 (mTORC2) and thereby upregulates Snail expression. Examining the components of mTORC2 showed that Pdcd4 knockdown increased the protein but not mRNA level of stress-activated-protein kinase interacting protein 1 (Sin1), which resulted from enhanced Sin1 translation. To understand how Pdcd4 regulates Sin1 translation, the SIN1 5' untranslated region (5'UTR) was fused with luciferase reporter and named as 5'Sin1-Luc. Pdcd4 knockdown/knockout significantly increased the translation of 5'Sin1-Luc but not the control luciferase without the SIN1 5'UTR, suggesting that Sin1 5'UTR is necessary for Pdcd4 to inhibit Sin1 translation. Ectopic expression of wild-type Pdcd4 and Pdcd4(157-469), a deletion mutant that binds to translation initiation factor 4A (eIF4A), sufficiently inhibited Sin1 translation, and thus suppressed mTORC2 kinase activity and invasion in colon tumor cells. By contrast, Pdcd4(157-469)(D253A,D418A), a mutant that does not bind to eIF4A, failed to inhibit Sin1 translation, and consequently failed to repress mTORC2 activity and invasion. In addition, directly inhibiting eIF4A with silvestrol significantly suppressed Sin1 translation and attenuated invasion. These results indicate that Pdcd4-inhibited Sin1 translation is through suppressing eIF4A, and functionally important for suppression of mTORC2 activity and invasion. Moreover, in colorectal cancer tissues, the Sin1 protein but not mRNA was significantly upregulated while Pdcd4 protein was downregulated, suggesting that loss of Pdcd4 might correlate with Sin1 protein level but not mRNA level in colorectal cancer patients. Taken together, our work reveals a novel mechanism by which Pdcd4 inhibits Sin1 translation to attenuatemTORC2 activity and thereby suppresses invasion.

Dataset Information

Chromosome 8p tumor suppressor genes SH2D4A and SORBS3 cooperate to inhibit interleukin-6 signaling in hepatocellular carcinoma.

Publications

Chromosome 8p tumor suppressor genes SH2D4A and SORBS3 cooperate to inhibit interleukin-6 signaling in hepatocellular carcinoma.

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