Zhenyu Zhong

ER Stress Cooperates with Hypernutrition to Trigger TNF-Dependent Spontaneous HCC Development

Endoplasmic reticulum (ER) stress has been implicated in the pathogenesis of viral hepatitis, insulin resistance, hepatosteatosis, and nonalcoholic steatohepatitis (NASH), disorders that increase risk of hepatocellular carcinoma (HCC). To determine whether and how ER stress contributes to obesity-driven hepatic tumorigenesis we fed wild-type (WT) and MUP-uPA mice, in which hepatocyte ER stress is induced by plasminogen activator expression, with high-fat diet. Although both strains were equally insulin resistant, the MUP-uPA mice exhibited more liver damage, more immune infiltration, and increased lipogenesis and, as a result, displayed classical NASH signs and developed typical steatohepatitic HCC. Both NASH and HCC development were dependent on TNF produced by inflammatory macrophages that accumulate in the MUP-uPA liver in response to hepatocyte ER stress.

Autophagy, Inflammation, and Immunity: A Troika Governing Cancer and Its Treatment.

Autophagy, a cellular waste disposal process, has well-established tumor-suppressive properties. New studies indicate that, in addition to its cell-autonomous anti-tumorigenic functions, autophagy inhibits cancer development by orchestrating inflammation and immunity. While attenuating tumor-promoting inflammation, autophagy enhances the processing and presentation of tumor antigens and thereby stimulates anti-tumor immunity. Although cancer cells can escape immunosurveillance by tuning down autophagy, certain chemotherapeutic agents with immunogenic properties may enhance anti-tumor immunity by inducing autophagic cell death. Understanding the intricate and complex relationships within this troika and how they are affected by autophagy enhancing drugs should improve the efficacy of cancer immunotherapy.

Immunosuppressive plasma cells impede T cell-dependent immunogenic chemotherapy

Cancer-associated genetic alterations induce expression of tumour antigens that can activate CD8+ cytotoxic T cells (CTLs), but the microenvironment of established tumours promotes immune tolerance through poorly understood mechanisms. Recently developed therapeutics that overcome tolerogenic mechanisms activate tumour-directed CTLs and are effective in some human cancers. Immune mechanisms also affect treatment outcome, and certain chemotherapeutic drugs stimulate cancer-specific immune responses by inducing immunogenic cell death and other effector mechanisms. Our previous studies revealed that B cells recruited by the chemokine CXCL13 into prostate cancer tumours promote the progression of castrate-resistant prostate cancer by producing lymphotoxin, which activates an IκB kinase α (IKKα)-BMI1 module in prostate cancer stem cells. Because castrate-resistant prostate cancer is refractory to most therapies, we examined B cell involvement in the acquisition of chemotherapy resistance. Here we focus on oxaliplatin, an immunogenic chemotherapeutic agent that is effective in aggressive prostate cancer. We show that mouse B cells modulate the response to low-dose oxaliplatin, which promotes tumour-directed CTL activation by inducing immunogenic cell death. Three different mouse prostate cancer models were refractory to oxaliplatin unless genetically or pharmacologically depleted of B cells. The crucial immunosuppressive B cells are plasmocytes that express IgA, interleukin (IL)-10 and programmed death ligand 1 (PD-L1), the appearance of which depends on TGFβ receptor signalling. Elimination of these cells, which also infiltrate human-therapy-resistant prostate cancer, allows CTL-dependent eradication of oxaliplatin-treated tumours.

Interleukin-17 receptor A signaling in transformed enterocytes promotes early colorectal tumorigenesis

Interleukin-17A (IL-17A) is a pro-inflammatory cytokine linked to rapid malignant progression of colorectal cancer (CRC) and therapy resistance. IL-17A exerts its pro-tumorigenic activity through its type A receptor (IL-17RA). However, IL-17RA is expressed in many cell types, including hematopoietic, fibroblastoid, and epithelial cells, in the tumor microenvironment, and how IL-17RA engagement promotes colonic tumorigenesis is unknown. Here we show that IL-17RA signals directly within transformed colonic epithelial cells (enterocytes) to promote early tumor development. IL-17RA engagement activates ERK, p38 MAPK, and NF-κB signaling and promotes the proliferation of tumorigenic enterocytes that just lost expression of the APC tumor suppressor. Although IL-17RA signaling also controls the production of IL-6, this mechanism makes only a partial contribution to colonic tumorigenesis. Combined treatment with chemotherapy, which induces IL-17A expression, and an IL-17A neutralizing antibody enhanced the therapeutic responsiveness of established colon tumors. These findings establish IL-17A and IL-17RA as therapeutic targets in colorectal cancer.

p62, Upregulated during Preneoplasia, Induces Hepatocellular Carcinogenesis by Maintaining Survival of Stressed HCC-Initiating Cells

p62 is a ubiquitin-binding autophagy receptor and signaling protein that accumulates in premalignant liver diseases and most hepatocellular carcinomas (HCCs). Although p62 was proposed to participate in the formation of benign adenomas in autophagy-deficient livers, its role in HCC initiation was not explored. Here we show that p62 is necessary and sufficient for HCC induction in mice and that its high expression in non-tumor human liver predicts rapid HCC recurrence after curative ablation. High p62 expression is needed for activation of NRF2 and mTORC1, induction of c-Myc, and protection of HCC-initiating cells from oxidative stress-induced death.

Targeting colorectal cancer via its microenvironment by inhibiting IGF-1 receptor-insulin receptor substrate and STAT3 signaling.

The tumor microenvironment (TME) exerts critical pro-tumorigenic effects through cytokines and growth factors that support cancer cell proliferation, survival, motility and invasion. Insulin-like growth factor-1 (IGF-1) and signal transducer and activator of transcription 3 (STAT3) stimulate colorectal cancer development and progression via cell autonomous and microenvironmental effects. Using a unique inhibitor, NT157, which targets both IGF-1 receptor (IGF-1R) and STAT3, we show that these pathways regulate many TME functions associated with sporadic colonic tumorigenesis in CPC-APC mice, in which cancer development is driven by loss of the Apc tumor suppressor gene. NT157 causes a substantial reduction in tumor burden by affecting cancer cells, cancer-associated fibroblasts (CAF) and myeloid cells. Decreased cancer cell proliferation and increased apoptosis were accompanied by inhibition of CAF activation and decreased inflammation. Furthermore, NT157 inhibited expression of pro-tumorigenic cytokines, chemokines and growth factors, including IL-6, IL-11 and IL-23 as well as CCL2, CCL5, CXCL7, CXCL5, ICAM1 and TGFβ; decreased cancer cell migratory activity and reduced their proliferation in the liver. NT157 represents a new class of anti-cancer drugs that affect both the malignant cell and its supportive microenvironment.

Inflammation-induced IgA + cells dismantle anti-liver cancer immunity

The role of adaptive immunity in early cancer development is controversial. Here we show that chronic inflammation and fibrosis in humans and mice with non-alcoholic fatty liver disease is accompanied by accumulation of liver-resident immunoglobulin-A-producing (IgA+) cells. These cells also express programmed death ligand 1 (PD-L1) and interleukin-10, and directly suppress liver cytotoxic CD8+ T lymphocytes, which prevent emergence of hepatocellular carcinoma and express a limited repertoire of T-cell receptors against tumour-associated antigens. Whereas CD8+ T-cell ablation accelerates hepatocellular carcinoma, genetic or pharmacological interference with IgA+ cell generation attenuates liver carcinogenesis and induces cytotoxic T-lymphocyte-mediated regression of established hepatocellular carcinoma. These findings establish the importance of inflammation-induced suppression of cytotoxic CD8+ T-lymphocyte activation as a tumour-promoting mechanism.

New mitochondrial DNA synthesis enables NLRP3 inflammasome activation

Dysregulated NLRP3 inflammasome activity results in uncontrolled inflammation, which underlies many chronic diseases. Although mitochondrial damage is needed for the assembly and activation of the NLRP3 inflammasome, it is unclear how macrophages are able to respond to structurally diverse inflammasome-activating stimuli. Here we show that the synthesis of mitochondrial DNA (mtDNA), induced after the engagement of Toll-like receptors, is crucial for NLRP3 signalling. Toll-like receptors signal via the MyD88 and TRIF adaptors to trigger IRF1-dependent transcription of CMPK2, a rate-limiting enzyme that supplies deoxyribonucleotides for mtDNA synthesis. CMPK2-dependent mtDNA synthesis is necessary for the production of oxidized mtDNA fragments after exposure to NLRP3 activators. Cytosolic oxidized mtDNA associates with the NLRP3 inflammasome complex and is required for its activation. The dependence on CMPK2 catalytic activity provides opportunities for more effective control of NLRP3 inflammasome-associated diseases.New mitochondrial DNA synthesis links the priming and activation of the NLRP3 inflammasome.

Erratum: Inflammation-induced IgA + cells dismantle anti-liver cancer immunity

This corrects the article DOI: 10.1038/nature24302

Novel Fate-Tracing Strategies Show that Hepatic Stellate Cells Mediate Fibrosis In Vivo

Mederacke I, Hsu CC, Troeger JS, et al. Fate tracing reveals hepatic stellate cells as dominant contributors to liver fibrosis independent of its aetiology. Nat Commun 2013;4:2823. Liver fibrosis often arises as a result of chronic liver damage and is characterized by the deposition of extracellular matrix (ECM) proteins, including collagen at injury sites, which can impair normal liver function and may lead to portal hypertension and hepatic failure (N Engl J Med 2004;350:1646–1654). Clinically, liver fibrosis leads to severe morbidity and mortality in patients (J Clin Invest 2005;115:209–218). Myofibroblast, a cell population that produce ECM proteins, has been shown as the mediator for liver fibrogenesis. However, the identity of cellular sources that give rise to myofibroblast remains elusive. In a recent article published in Nature Communications, Mederacke et al discovered lecithin-retinol acyltrasferase (Lrat) as a novel marker for hepatic stellate cells (HSCs). The expression of Lrat was distinctively high in HSCs, whereas other cells, such as hepatocytes, Kupffer cells, cholangiocytes, or endothelial cells, had undetectable Lrat expression. Consistent with its unique expression pattern, Lrat has been shown to play a pivotal role in regulating the formation of retinyl ester-containing lipid droplet, the signature for quiescent HSCs. With the help of this newly discovered marker for HSCs, Mederacke et al studied the precise contribution of HSCs in promoting liver fibrosis in vivo. Briefly, they designed a novel fate-tracing strategy by generating transgenic mice that have Cre recombinase expression cassette under the control of murine Lrat promoter. These animals were then crossed with floxed Zs-Green fluorescent mice; therefore, HSCs in the progeny mice would be labeled by Zs-Green fluorescence. Mederacke et al first confirmed that Lrat-Cre-labeled cells are mostly (>99%) HSCs, because Lrat-Cre expression and known markers of HSCs (ie, desmin and Pdgfrβ) almost completely overlapped. To investigate the precise role of HSCs in promoting liver fibrogenesis in vivo, they performed fate-tracing experiments in several different fibrotic animal models, including toxin-induced liver fibrosis models (ie, carbon tetrachloride-induced and thioacetamide-induced liver fibrosis models) and biliary liver fibrosis models (ie, bile duct ligation model, 3,5-diethoxycarbonyl-1,4-dihydrocollidine-containing diet model and Mdr2KO mouse model). Strikingly, Mederacke et al found that HSCs are the dominant and universal cell population that gives rise to collagen-secreting myofibroblasts in various murine liver fibrosis models. This was also confirmed by the reduction of liver fibrosis in mice with depletion of HSCs using Lrat-induced diphthelia toxin receptor, which further strengthens the concept that HSCs are the responsible cell types in hepatic fibrosis in general. Another important finding by Mederacke et al is that HSCs do not give rise to epithelial cells after liver damage. They found no increase in the numbers of Lrat-Cre and HNF4a (a hepatocyte marker) double-positive cells during liver regeneration after liver damage caused by 7 different hepatic injury models, including 70% partial hepatectomy model. In addition, by employing series of experiments using bone marrow transplantation, Mederacke et al further concluded that HSCs are endogenous to liver, rather than a bone marrow-derived cell population.