Correction to: Relationship between TRAF6 and deterioration of HCC: an immunohistochemical and in vitro study.

[This corrects the article DOI: 10.1186/s12935-016-0352-z.].

Relationship between TRAF6 and deterioration of HCC: an immunohistochemical and in vitro study.

OBJECTIVE: To explore the relationship between tumor necrosis factor receptor-associated factor 6 (TRAF6) and the clinicopathological features in HCC as well as its biological function. METHODS: Totally, 412 liver tissues were collected, including 171 hepatocellular carcinoma (HCC) and their corresponding non-tumor tissues, 37 cirrhosis and 33 normal liver tissues. The expression of TRAF6 was assessed by immunohistochemistry. Then, analysis of the correlations between TRAF6 expression and clinicopathological parameters in HCC was conducted. Furtherer, in vitro experiments on HepG2 and Hep3B cells were performed to validate the biological function of TRAF6 on HCC cells. TRAF6 siRNA was transfected into HepG2 and Hep3B cell lines and TRAF6 expression was evaluated with RT-qPCR and western blot. The assays of cell viability, proliferation, apoptosis and caspase-3/7 activity were carried out to investigate the effects of TRAF6 on HCC cells with RNA interference. Cell viability was assessed with Cell Titer-Blue kit. Cell proliferation was tested with MTS kit. Cell apoptosis was checked through morphologic detection with fluorescence microscope, as well as caspase-3/7 activity was measured with fluorogenic substrate detection. RESULTS: The positive expression rate of TRAF6 protein was 49.7 % in HCC, significantly higher than that of normal liver (12.1 %), cirrhosis (21.6 %) and adjacent non-cancerous tissues (36.3 %, all P < 0.05). Upregulated TRAF6 was detected in groups with metastasis (Z = -2.058, P = 0.04) and with low micro-vessel density (MVD) expression (Z = -2.813, P = 0.005). Spearman correlation analysis further showed that the expression of TRAF6 was positively correlated with distant metastasis (r = 0.158, P = 0.039) and negatively associated with MVD (r = -0.249, P = 0.004). Besides, knock-down of TRAF6 mRNA in HCC cell lines HepG2 and Hep3B both resulted in cell viability and proliferation inhibition, also cell apoptosis induction and caspase-3/7 activity activation. CONCLUSIONS: TRAF6 may contribute to metastasis and deterioration of the HCC via influencing cell growth and apoptosis. Thus, TRAF6 might become a predictive and therapeutic biomarker for HCC.

Mesenchymal Stromal Cells Increase the Natural Killer Resistance of Circulating Tumor Cells via Intercellular Signaling of cGAS-STING-IFNß-HLA.

Circulating tumor cells (CTCs) shed from primary tumors must overcome the cytotoxicity of immune cells, particularly natural killer (NK) cells, to cause metastasis. The tumor microenvironment (TME) protects tumor cells from the cytotoxicity of immune cells, which is partially executed by cancer-associated mesenchymal stromal cells (MSCs). However, the mechanisms by which MSCs influence the NK resistance of CTCs remain poorly understood. This study demonstrates that MSCs enhance the NK resistance of cancer cells in a gap junction-dependent manner, thereby promoting the survival and metastatic seeding of CTCs in immunocompromised mice. Tumor cells crosstalk with MSCs through an intercellular cGAS-cGAMP-STING signaling loop, leading to increased production of interferon-ß (IFNß) by MSCs. IFNß reversely enhances the type I IFN (IFN-I) signaling in tumor cells and hence the expression of human leukocyte antigen class I (HLA-I) on the cell surface, protecting the tumor cells from NK cytotoxicity. Disruption of this loop reverses NK sensitivity in tumor cells and decreases tumor metastasis. Moreover, there are positive correlations between IFN-I signaling, HLA-I expression, and NK tolerance in human tumor samples. Thus, the NK-resistant signaling loop between tumor cells and MSCs may serve as a novel therapeutic target.

Label-free optical metabolic imaging of adipose tissues for prediabetes diagnosis.

Rationale: Prediabetes can be reversed through lifestyle intervention, but its main pathologic hallmark, insulin resistance (IR), cannot be detected as conveniently as blood glucose testing. In consequence, the diagnosis of prediabetes is often delayed until patients have hyperglycemia. Therefore, developing a less invasive diagnostic method for rapid IR evaluation will contribute to the prognosis of prediabetes. Adipose tissue is an endocrine organ that plays a crucial role in the development and progression of prediabetes. Label-free visualizing the prediabetic microenvironment of adipose tissues provides a less invasive alternative for the characterization of IR and inflammatory pathology. Methods: Here, we successfully identified the differentiable features of prediabetic adipose tissues by employing the metabolic imaging of three endogenous fluorophores NAD(P)H, FAD, and lipofuscin-like pigments. Results: We discovered that 1040-nm excited lipofuscin-like autofluorescence could mark the location of macrophages. This unique feature helps separate the metabolic fluorescence signals of macrophages from those of adipocytes. In prediabetes fat tissues with IR, we found only adipocytes exhibited a low redox ratio of metabolic fluorescence and high free NAD(P)H fraction a1. This differential signature disappears for mice who quit the high-fat diet or high-fat-high-sucrose diet and recover from IR. When mice have diabetic hyperglycemia and inflamed fat tissues, both adipocytes and macrophages possess this kind of metabolic change. As confirmed with RNA-seq analysis and histopathology evidence, the change in adipocyte's metabolic fluorescence could be an indicator or risk factor of prediabetic IR. Conclusion: Our study provides an innovative approach to diagnosing prediabetes, which sheds light on the strategy for diabetes prevention.

Engineering of human mesenchymal stem cells resistant to multiple natural killer subtypes.

Mesenchymal stem cells (MSCs) as a therapeutic promise are often quickly cleared by innate immune cells of the host including natural killer (NK) cells. Efforts have been made to generate immune-escaping human embryonic stem cells (hESCs) where T cell immunity is evaded by defecting ß-2-microglobulin (B2M), a common unit for human leukocyte antigen (HLA) class I, and NK cells are inhibited via ectopic expression of HLA-E or -G. However, NK subtypes vary among recipients and even at different pathologic statuses. It is necessary to dissect and optimize the efficacy of the immune-escaping cells against NK subtypes. Here, we first generated B2M knockout hESCs and differentiated them to MSCs (EMSCs) and found that NK resistance occurred with B2M-/- EMSCs expressing HLA-E and -G only when they were transduced via an inducible lentiviral system in a dose-dependent manner but not when they were inserted into a safe harbor. HLA-E and -G expressed at high levels together in transduced EMSCs inhibited three major NK subtypes, including NKG2A+ /LILRB1+ , NKG2A+ /LILRB1- , and NKG2A- /LILRB1+ , which was further potentiated by IFN-γ priming. Thus, this study engineers MSCs with resistance to multiple NK subtypes and underscores that dosage matters when a transgene is used to confer a novel effect to host cells, especially for therapeutic cells to evade immune rejection.

Reciprocal activation between MMP-8 and TGF-ß1 stimulates EMT and malignant progression of hepatocellular carcinoma.

The efficiency of surgery in hepatocellular carcinoma (HCC) is limited due to metastasis and recurrence, but the molecular mechanisms are unclear. Here, we show that MMP-8 and TGF-ß1 accumulate in highly invasive HCC cell lines and invasive HCC patient tissues. Upregulation of MMP-8 and TGF-ß1 correlated with changes in cellular epithelial-mesenchymal transition (EMT) phenotypes and HCC migration and invasion. The expression of TGF-ß1 was markedly restored by MMP-8 overexpression in TGF-ß1-depleted HCC cells mainly via the activation of PI3K/Akt/Rac1 pathway. Similarly, the expression of MMP-8 was restored by TGF-ß1 treatment in MMP-8-depleted HCC cells mainly through the activation of the same PI3K/Akt/Rac1 pathway. MMP-8 expression was significantly related to TGF-ß1 expression in HCC patient tissues, and high expression of MMP-8 or TGF-ß1 was significantly associated with TNM stage and HCC metastasis. Specifically, patients with high co-expression of MMP-8 and TGF-ß1 had a shorter time-to-recurrence than those with low co-expression. Therefore, the reciprocal positive interplay between MMP-8 and TGF-ß1 contributes to HCC invasion and metastasis by inducing EMT mainly through the PI3K/Akt/Rac1 pathway.

[Lentivirus-mediated shRNA interference of Cx26 suppresses epithelial mesenchymal transition and invasion of highly invasive hepatocellular carcinoma cells in vitro].

OBJECTIVE: To explore the effect of lentivirus-mediated shRNA interference of Cx26 on epithelial-mesenchymal transition (EMT) and invasion of highly invasive human hepatocellular carcinoma cells in vitro. METHODS: SK-Hep-1 cells were infected with the lentivirus for delivering Cx26 shRNA, and the stably transfected cells were selected by puromycin. The interference efficiency of shRNA-Cx26 was assessed with real-time PCR and Western blotting. The morphological changes of the transfected SK-Hep-1 cells were observed microscopically, and the protein expressions of E-cadherin and vimentin were detected using Western blotting. The effect of Cx26 interference on the invasiveness of SK-Hep-1 cells was determined by Transwell invasion assay. RESULTS: Compared with SK-Hep-1 cells infected with empty EGFP vector and uninfected cells, the cells transfected with shRNA-Cx26 showed significantly reduced mRNA and protein expressions of Cx26 (P<0.01), which resulted in obvious morphological conversion from mesenchymal cells to epithelial cells. shRNA-Cx26-transfected cells showed significantly increased E-cadherin protein expression (P<0.01) but decreased vimentin expression (P<0.01) with obviously attenuated invasive ability in vitro (P<0.01). CONCLUSION: Targeted down-regulation of Cx26 expression can inhibit the EMT and invasion of SK-Hep-1 cells in vitro.