Myeloid-derived suppressor cells (MDSCs) possess immunosuppressive activities, which allow cancers to escape immune surveillance and become non-responsive to immune checkpoints blockade. Here we ...report hypoxia as a cause of MDSC accumulation. Using hepatocellular carcinoma (HCC) as a cancer model, we show that hypoxia, through stabilization of hypoxia-inducible factor-1 (HIF-1), induces ectoenzyme, ectonucleoside triphosphate diphosphohydrolase 2 (ENTPD2/CD39L1), in cancer cells, causing its overexpression in HCC clinical specimens. Overexpression of ENTPD2 is found as a poor prognostic indicator for HCC. Mechanistically, we demonstrate that ENTPD2 converts extracellular ATP to 5'-AMP, which prevents the differentiation of MDSCs and therefore promotes the maintenance of MDSCs. We further find that ENTPD2 inhibition is able to mitigate cancer growth and enhance the efficiency and efficacy of immune checkpoint inhibitors. Our data suggest that ENTPD2 may be a good prognostic marker and therapeutic target for cancer patients, especially those receiving immune therapy.Myeloid-derived suppressor cells (MDSCs) promote tumor immune escape. Here, the authors show that in hepatocellular carcinoma, hypoxia induces the expression of ENTPD2 on cancer cells leading to elevated extracellular 5'-AMP, which in turn promote the maintenance of MDSCs by preventing their differentiation.
A population of stromal cells, myeloid‐derived suppressor cells (MDSCs), is present in tumors. Though studies have gradually revealed the protumorigenic functions of MDSCs, the molecular mechanisms ...guiding MDSC recruitment remain largely elusive. Hypoxia, O2 deprivation, is an important factor in the tumor microenvironment of solid cancers, whose growth often exceeds the growth of functional blood vessels. Here, using hepatocellular carcinoma as the cancer model, we show that hypoxia is an important driver of MDSC recruitment. We observed that MDSCs preferentially infiltrate into hypoxic regions in human hepatocellular carcinoma tissues and that hypoxia‐induced MDSC infiltration is dependent on hypoxia‐inducible factors. We further found that hypoxia‐inducible factors activate the transcription of chemokine (C‐C motif) ligand 26 in cancer cells to recruit chemokine (C‐X3‐C motif) receptor 1‐expressing MDSCs to the primary tumor. Knockdown of chemokine (C‐C motif) ligand 26 in cancer cells profoundly reduces MDSC recruitment, angiogenesis, and tumor growth. Therapeutically, blockade of chemokine (C‐C motif) ligand 26 production in cancer cells by the hypoxia‐inducible factor inhibitor digoxin or blockade of chemokine (C‐X3‐C motif) receptor 1 in MDSCs by chemokine (C‐X3‐C motif) receptor 1 neutralizing antibody could substantially suppress MDSC recruitment and tumor growth. Conclusion: This study unprecedentedly reveals a novel molecular mechanism by which cancer cells direct MDSC homing to primary tumor and suggests that targeting MDSC recruitment represents an attractive therapeutic approach against solid cancers. (Hepatology 2016;64:797‐813)
Poor prognosis of cancers, including hepatocellular carcinoma (HCC), is mainly associated with metastasis; however, the underlying mechanisms remain poorly understood. This article investigates the ...role of lysyl oxidase‐like 2 (LOXL‐2) in the biology of HCC metastasis. First, we showed that HCC metastasis relies on a collagen‐modifying enzyme, LOXL2, which was significantly overexpressed in tumorous tissues and sera of HCC patients, indicating that LOXL2 may be a good diagnostic marker for HCC patients. Second, we delineated a complex, interlinked signaling network that involves multiple regulators, including hypoxia, transforming growth factor beta (TGF‐β), and microRNAs (miRNAs), converging to control the expression of LOXL2. We found not only that LOXL2 was regulated by hypoxia/hypoxia‐inducible factor 1 alpha (HIF‐1α), but also that TGF‐β activated LOXL2 transcription through mothers against decapentaplegic homolog 4 (Smad4), whereas two frequently underexpressed miRNA families, miR‐26 and miR‐29, cooperatively suppressed LOXL2 transcription through interacting with the 3' untranslated region of LOXL2. Third, we demonstrated the imperative roles of LOXL2 in modifying the extracellular matrix components in the tumor microenvironment and metastatic niche of HCC. LOXL2 promoted intrahepatic metastasis by increasing tissue stiffness, thereby enhancing the cytoskeletal reorganization of HCC cells. Furthermore, LOXL2 facilitated extrahepatic metastasis by enhancing recruitment of bone‐marrow–derived cells to the metastatic site. Conclusion: These findings integrate the clinical relevance, molecular regulation, and functional implications of LOXL2 in HCC metastasis. (Hepatology 2014;60:1645–1658)
Hepatocellular carcinoma (HCC) is an aggressive tumor, with a high mortality rate due to late symptom presentation and frequent tumor recurrences and metastasis. It is also a rapidly growing tumor ...supported by different metabolic mechanisms; nevertheless, the biological and molecular mechanisms involved in the metabolic reprogramming in HCC are unclear. In this study, we found that pyruvate kinase M2 (PKM2) was frequently over-expressed in human HCCs and its over-expression was associated with aggressive clinicopathological features and poor prognosis of HCC patients. Furthermore, knockdown of PKM2 suppressed aerobic glycolysis and cell proliferation in HCC cell lines in vitro. Importantly, knockdown of PKM2 hampered HCC growth in both subcutaneous injection and orthotopic liver implantation models, and reduced lung metastasis in vivo. Of significance, PKM2 over-expression in human HCCs was associated with a down-regulation of a liver-specific microRNA, miR-122. We further showed that miR-122 interacted with the 3UTR of the PKM2 gene. Re-expression of miR-122 in HCC cell lines reduced PKM2 expression, decreased glucose uptake in vitro, and suppressed HCC tumor growth in vivo. Our clinical data and functional studies have revealed a novel biological mechanism involved in HCC metabolic reprogramming.
Background:
Cholinergic deficiency has been suggested to associate with the abnormal accumulation of Aβ and tau for patients with Alzheimer's disease (AD). However, no studies have investigated the ...effect of
APOE
-ε4 and group differences in modulating the cholinergic basal forebrain–amygdala network for subjects with different levels of cognitive impairment. We evaluated the effect of
APOE
-ε4 on the cholinergic structural association and the neurocognitive performance for subjects with different levels of cognitive impairment.
Methods:
We used the structural brain magnetic resonance imaging scans from the Alzheimer's Disease Neuroimaging Initiative dataset. The study included cognitively normal (CN,
n
= 167) subjects and subjects with significant memory concern (SMC,
n
= 96), early mild cognitive impairment (EMCI,
n
= 146), late cognitive impairment (LMCI,
n
= 138), and AD (
n
= 121). Subjects were further categorized according to the
APOE
-ε4 allele carrier status. The main effects of
APOE
-ε4 and group difference on the brain volumetric measurements were assessed. Regression analyses were conducted to evaluate the associations among cholinergic structural changes,
APOE
-ε4 status, and cognitive performance.
Results:
We found that
APOE
-ε4 carriers in the disease group showed higher brain atrophy than non-carriers in the cholinergic pathway, while there is no difference between carriers and non-carriers in the CN group.
APOE
-ε4 allele carriers in the disease groups also exhibited a stronger cholinergic structural correlation than non-carriers did, while there is no difference between the carriers and non-carriers in the CN subjects. Disease subjects exhibited a stronger structural correlation in the cholinergic pathway than CN subjects did. Moreover,
APOE-
ε4 allele carriers in the disease group exhibited a stronger correlation between the volumetric changes and cognitive performance than non-carriers did, while there is no difference between carriers and non-carriers in CN subjects. Disease subjects exhibited a stronger correlation between the volumetric changes and cognitive performance than CN subjects did.
Conclusion:
Our results confirmed the effect of
APOE-
ε4 on and group differences in the associations with the cholinergic structural changes that may reflect impaired brain function underlying neurocognitive degeneration in AD.
Immune checkpoint inhibitors are effective in the treatment of some hepatocellular carcinomas (HCCs), but these tumors do not always respond to inhibitors of programmed cell death 1 (PDCD1, also ...called PD1). We investigated mechanisms of resistance of liver tumors in mice to infiltrating T cells.
Mice were given hydrodynamic tail vein injections of clustered regularly interspaced short palindromic repeats–Cas9 (CRISPR-Cas9) and transposon vectors to disrupt Trp53 and overexpress C-Myc (Trp53KO/C-MycOE mice). Pvrl1 and Pvrl3 were knocked down in Hepa1-6 cells by using short hairpin RNAs. Hepa1-6 cells were injected into livers of C57BL/6 mice; some mice were given intraperitoneal injections of antibodies against PD1, T-cell immunoreceptor with Ig and ITIM domains (TIGIT), or CD8 before the cancer cells were injected. Liver tissues were collected from mice and analyzed by histology, immunohistochemistry, and quantitative real-time polymerase chain reaction; tumors were analyzed by mass cytometry using markers to detect T cells and other lymphocytes. We obtained HCC and nontumorous liver tissues and clinical data from patients who underwent surgery in Hong Kong and analyzed the tissues by immunohistochemistry.
Trp53KO/C-MycOE mice developed liver tumors in 3–5 weeks; injections of anti-PD1 did not slow tumor development. Tumors from mice given anti-PD1 had larger numbers of memory CD8+ T cells (CD44+CD62L–KLRG1int) and T cells that expressed PD1, lymphocyte activating 3 (LAG3), and TIGIT compared with mice not given the antibody. HCC tissues from patients had higher levels of PVRL1 messenger RNA and protein than nontumorous tissues. Increased PVRL1 was associated with shorter times of disease-free survival. Knockdown of Pvrl1 in Hepa1-6 cells caused them to form smaller tumors in mice, infiltrated by higher numbers of CD8+ T cells that expressed the inhibitory protein TIGIT; these effects were not observed in mice with depletion of CD8+ T cells. In Hepa1-6 cells, PVRL1 stabilized cell surface PVR, which interacted with TIGIT on CD8+ T cells; knockdown of Pvrl1 reduced cell-surface levels of PVR but not levels of Pvr messenger RNA. In Trp53KO/C-MycOE mice and mice with tumors grown from Hepa1-6 cells, injection of the combination of anti-PD1 and anti-TIGIT significantly reduced tumor growth, increased the ratio of cytotoxic to regulatory T cells in tumors, and prolonged survival.
PVRL1, which is up-regulated by HCC cells, stabilizes cell surface PVR, which interacts with TIGIT, an inhibitory molecule on CD8+ effector memory T cells. This suppresses the ant-tumor immune response. Inhibitors of PVRL1/TIGIT, along with anti-PD1 might be developed for treatment of HCC.
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Cancer cells preferentially utilize glucose and glutamine, which provide macromolecules and antioxidants that sustain rapid cell division. Metabolic reprogramming in cancer drives an increased ...glycolytic rate that supports maximal production of these nutrients. The folate cycle, through transfer of a carbon unit between tetrahydrofolate and its derivatives in the cytoplasmic and mitochondrial compartments, produces other metabolites that are essential for cell growth, including nucleotides, methionine, and the antioxidant NADPH. Here, using hepatocellular carcinoma (HCC) as a cancer model, we have observed a reduction in growth rate upon withdrawal of folate. We found that an enzyme in the folate cycle, methylenetetrahydrofolate dehydrogenase 1-like (MTHFD1L), plays an essential role in support of cancer growth. We determined that MTHFD1L is transcriptionally activated by NRF2, a master regulator of redox homeostasis. Our observations further suggest that MTHFD1L contributes to the production and accumulation of NADPH to levels that are sufficient to combat oxidative stress in cancer cells. The elevation of oxidative stress through MTHFD1L knockdown or the use of methotrexate, an antifolate drug, sensitizes cancer cells to sorafenib, a targeted therapy for HCC. Taken together, our study identifies MTHFD1L in the folate cycle as an important metabolic pathway in cancer cells with the potential for therapeutic targeting.
The presence of a swallow-tail sign in the nigrosome-1 with hyperintense signal shown on the susceptibility-weighted imaging (SWI) has been shown to be sensitive in detecting the abnormal iron ...deposits in this area. A systematic evaluation in healthy subjects is required before this tool can be recommended in a widespread application. We evaluated a simple and practical SWI approach using a multiecho gradient-echo sequence with an improved contrast-to-noise ratio (CNR). We also evaluated the association of the neuromelanin imaging contrast behavior with the susceptibility and relaxation measurements. Twenty-five older and 23 young healthy adults were evaluated. The CNRs of the nigrosome-1 were compared along with method and group. Correlations of the nigrosome-1 neuromelanin signal in the neuromelanin-sensitive imaging with CNRs in the susceptibility, T1 and T2 mappings were examined. Two different coils were used to confirm the reproducibility. Compared with the single-echo, multiecho SWI can improve the CNR of the swallow-tail sign. We found significant correlations between neuromelanin signal and CNRs in the susceptibility and T2 mappings, and T1 value. The older subjects exhibited increased CNRs compared with the young adults. No significant difference was observed in the measurements between 20 and 64 channels. The multiecho technique allows the high-quality nigrosome-1 images in SWI and allows for a joint analysis of T2* and quantitative-susceptibility mapping at high spatial resolution. The correlations of neuromelanin-sensitive imaging with susceptibility and T2 imply that the iron content in the nigrosome-1 may have significant influences on the hyperintensity of neuromelanin in the magnetization transfer-related contrast.
Purpose
We investigated the volumetric changes in the components of the cholinergic pathway for patients with early mild cognitive impairment (EMCI) and those with late mild cognitive impairment ...(LMCI). The effect of patients’ apolipoprotein 4 (APOE-ε4) allele status on the structural changes were analyzed.
Methods
Structural magnetic resonance imaging data were collected. Patients’ demographic information, plasma data, and validated global cognitive composite scores were included. Relevant features were extracted for constructing machine learning models to differentiate between EMCI (n = 312) and LMCI (n = 541) and predict patients’ neurocognitive function. The data were analyzed primarily through one-way analysis of variance and two-way analysis of covariance.
Results
Considerable differences were observed in cholinergic structural changes between patients with EMCI and LMCI. Cholinergic atrophy was more prominent in the LMCI cohort than in the EMCI cohort (P < 0.05 family-wise error corrected). APOE-ε4 differentially affected cholinergic atrophy in the LMCI and EMCI cohorts. For LMCI cohort, APOE-ε4 carriers exhibited increased brain atrophy (left amygdala: P = 0.001; right amygdala: P = 0.006, and right Ch123, P = 0.032). EMCI and LCMI patients showed distinctive associations of gray matter volumes in cholinergic regions with executive (R
2
= 0.063 and 0.030 for EMCI and LMCI, respectively) and language (R
2
= 0.095 and 0.042 for EMCI and LMCI, respectively) function.
Conclusions
Our data confirmed significant cholinergic atrophy differences between early and late stages of mild cognitive impairment. The impact of the APOE-ε4 allele on cholinergic atrophy varied between the LMCI and EMCI groups.
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