Cluster microRNAs miR-194 and miR-215 suppress the tumorigenicity of intestinal tumor organoids.

Tumor stem cells with self-renewal and multipotent capacity play critical roles in the initiation and progression of cancer. Recently, a new 3-D culture system known as organoid culture has been developed, allowing Lgr5-positive stem cells to form organoids that resemble the properties of original tissues. Here we established organoids derived from intestinal tumors of Apcmin/+ mice and normal intestinal epithelia of C57BL/6J mice and investigated the roles of microRNA (miRNA) in intestinal tumor organoids. The results of microarray analyses revealed that expression of the cluster miRNAs, miR-194 and miR-215 was markedly suppressed in intestinal tumor organoids in comparison with organoids derived from normal intestinal epithelia. Enforced expression of miR-194 resulted in inhibition of E2f3, a positive regulator of the cell cycle and growth suppression of intestinal tumor organoids. In addition, enforced expression of miR-215 suppressed the cancer stem cell signature through downregulation of intestinal stem cell markers including Lgr5. These findings indicate that the miRNA cluster including miR-194 and miR-215 plays important roles in suppressing the growth and attenuating the stemness of intestinal tumor organoids.

Gut microbiota-mediated generation of saturated fatty acids elicits inflammation in the liver in murine high-fat diet-induced steatohepatitis.

BACKGROUND: The gut microbiota plays crucial roles in the development of non-alcoholic steatohepatitis (NASH). However, the precise mechanisms by which alterations of the gut microbiota and its metabolism contributing to the pathogenesis of NASH are not yet fully elucidated. METHODS: Mice were fed with a recently reported new class of high-fat diet (HFD), steatohepatitis-inducing HFD (STHD)-01 for 9 weeks. The composition of the gut microbiota was analyzed by T-RFLP. Luminal metabolome was analyzed using capillary electrophoresis and liquid chromatography time-of-flight mass spectrometry (CE- and LC-TOFMS). RESULTS: Mice fed the STHD-01 developed NASH-like pathology within a short period. Treatment with antibiotics prevented the development of NASH by STHD-01. The composition of the gut microbiota and its metabolic activities were markedly perturbed in the STHD-01-fed mice, and antibiotic administration normalized these changes. We identified that long-chain saturated fatty acid and n-6 fatty acid metabolic pathways were significantly altered by STHD-01. Of note, the changes in gut lipidome caused by STHD-01 were mediated by gut microbiota, as the depletion of the gut microbiota could reverse the perturbation of these metabolic pathways. A saturated long-chain fatty acid, palmitic acid, which accumulated in the STHD-01 group, activated liver macrophages and promoted TNF-α expression. CONCLUSIONS: Lipid metabolism by the gut microbiota, particularly the saturation of fatty acids, affects fat accumulation in the liver and subsequent liver inflammation in NASH.

Aberrant DNA Methylation as a Biomarker and a Therapeutic Target of Cholangiocarcinoma.

Cholangiocarcinoma is an epithelial malignancy arising in the region between the intrahepatic bile ducts and the ampulla of Vater at the distal end of the common bile duct. The effect of current chemotherapy regimens against cholangiocarcinoma is limited, and the prognosis of patients with cholangiocarcinoma is poor. Aberrant DNA methylation and histone modification induce silencing of tumor suppressor genes and chromosomal instability during carcinogenesis. Studies have shown that the tumor suppressor genes and microRNAs (miRNAs) including MLH1, p14, p16, death-associated protein kinase (DAPK), miR-370 and miR-376c are frequently methylated in cholangiocarcinoma. Silencing of these tumor suppressor genes and miRNAs plays critical roles in the initiation and progression of cholangiocarcinoma. In addition, recent studies have demonstrated that DNA methylation inhibitors induce expression of endogenous retroviruses and exert the anti-tumor effect of via an anti-viral immune response. Aberrant DNA methylation of tumor suppressor genes and miRNAs could be a powerful biomarker for the diagnosis and treatment of cholangiocarcinoma. Epigenetic therapy with DNA methylation inhibitors holds considerable promise for the treatment of cholangiocarcinoma through the reactivation of tumor suppressor genes and miRNAs as well as the induction of an anti-viral immune response.

Erratum: Publisher Correction: Epigenetic silencing of Lgr5 induces senescence of intestinal epithelial organoids during the process of aging.

[This corrects the article DOI: 10.1038/s41514-018-0031-5.].

Glucose Depletion Enhances the Stem Cell Phenotype and Gemcitabine Resistance of Cholangiocarcinoma Organoids through AKT Phosphorylation and Reactive Oxygen Species.

Cancer cells are strongly dependent on the glycolytic pathway for generation of energy even under aerobic condition through a phenomenon known as the Warburg effect. Rapid proliferation of cancer cells is often accompanied by high glucose consumption and abnormal angiogenesis, which may lead to glucose depletion. In the present study, we investigated how cholangiocarcinoma cells adapt to glucose depletion using a 3D organoid culture system. We cultured organoids derived from cholangiocarcinoma under glucose-free condition and investigated cell proliferation, expression of stem cell markers and resistance to gemcitabine. Cholangiocarcinoma organoids cultured under glucose-free condition showed reduced proliferation but were able to survive. We also observed an increase in the expression of stem cell markers including LGR5 and enhancement of stem cell phenotypic characteristics such as resistance to gemcitabine through AKT phosphorylation and reactive oxygen species. These findings indicate that cholangiocarcinoma cells are able to adapt to glucose depletion through enhancement of their stem cell phenotype in response to changes in microenvironmental conditions.

Epigenetic silencing of Lgr5 induces senescence of intestinal epithelial organoids during the process of aging.

To understand the molecular features underlying stem cell aging, we established intestinal epithelial organoids derived from both young and aged mice and investigated alterations in their senescence and epigenetic status. Senescence-related changes including accumulation of senescence-associated ß-galactosidase and up-regulation of Cdkn1a (p21) by DNA demethylation were observed in intestinal epithelial organoids derived from aged mice. We also demonstrated that the important stem cell marker Lgr5 was epigenetically silenced by trimethylation of histone H3 lysine 27, inducing suppression of Wnt signaling and a decrease of cell proliferation in organoids from aged mice. We further treated intestinal epithelial organoids from aged mice with nicotinamide mononucleotide (NMN), a key NAD+ intermediate. As a result, the organoids showed a higher NAD+ level, increased cell proliferative ability, activation of Lgr5 and suppression of senescence-associated genes, indicating that treatment with NMN could ameliorate senescence-related changes in intestinal epithelia. These findings suggest that organoids derived from aged animals could be a powerful research tool for investigating the molecular mechanisms underlying stem cell aging and for development of some form of anti-aging intervention, thus contributing to prolongation of healthy life expectancy.

Induction of differentiation of intrahepatic cholangiocarcinoma cells to functional hepatocytes using an organoid culture system.

Intrahepatic cholangiocarcinoma (IHCC) is a highly aggressive malignancy with a poor prognosis. It is thought to originate from cholangiocytes, which are the component cells of intrahepatic bile ducts. However, as patients with viral hepatitis often develop IHCC, it has been suggested that transformed hepatocytes may play a role in IHCC development. To investigate whether IHCC cells can be converted to functional hepatocytes, we established organoids derived from human IHCC and cultured them under conditions suitable for hepatocyte differentiation. IHCC organoids after hepatocyte differentiation acquired functions of mature hepatocytes such as albumin secretion, bile acid production and increased CYP3A4 activity. Studies using a mouse model of IHCC indicate that Wnt3a derived from macrophages recruited upon inflammation in the liver may promote the malignant transformation of hepatocytes to IHCC cells. The results of the present study support the recently proposed hypothesis that IHCC cells are derived from hepatocytes.

Inhibition of DNA Methylation Suppresses Intestinal Tumor Organoids by Inducing an Anti-Viral Response.

Recent studies have proposed that the major anti-tumor effect of DNA methylation inhibitors is induction of interferon-responsive genes via dsRNAs-containing endogenous retroviruses. Recently, a 3D culture system for stem cells known as organoid culture has been developed. Lgr5-positive stem cells form organoids that closely recapitulate the properties of original tissues. To investigate the effect of DNA demethylation on tumor organoids, we have established organoids from intestinal tumors of Apc(Min/+) (Min) mice and subjected them to 5-aza-2'-deoxycytidine (5-Aza-CdR) treatment and Dnmt1 knockdown. DNA demethylation induced by 5-Aza-CdR treatment and Dnmt1 knockdown significantly reduced the cell proliferation of the tumor organoids. Microarray analyses of the tumor organoids after 5-Aza-CdR treatment and Dnmt1 knockdown revealed that interferon-responsive genes were activated by DNA demethylation. Gene ontology and pathway analyses clearly demonstrated that these genes activated by DNA demethylation are involved in the anti-viral response. These findings indicate that DNA demethylation suppresses the proliferation of intestinal tumor organoids by inducing an anti-viral response including activation of interferon-responsive genes. Treatment with DNA methylation inhibitors to activate a growth-inhibiting immune response may be an effective therapeutic approach for colon cancers.

microRNA-34a as a Therapeutic Agent against Human Cancer.

microRNAs (miRNAs) are small non-coding RNAs that down-regulate expression of various target genes. Cancer-related miRNAs are aberrantly expressed and act as tumor suppressors or oncogenes during carcinogenesis. We and other researchers have demonstrated that important tumor suppressor miRNAs are silenced by epigenetic alterations, resulting in the activation of target oncogenes in cancer cells. miR-34a was identified as a target of p53 and induces a G1 cell cycle arrest, senescence and apoptosis in response to DNA damage. miR-34a is an important tumor suppressor whose expression is epigenetically silenced in various human cancers. Enforced expression of miR-34a induces cell cycle arrest, apoptosis, senescence, and suppression of epithelial-mesenchymal transition and inhibits cell proliferation of cancer stem cells. Epigenetic therapy with chromatin-modifying drugs such as inhibitors of DNA methylation and histone deacetylase has shown clinical promise for the treatment of malignancies. Restoring of miR-34a expression by epigenetic therapy and/or delivery of miR-34a mimics may be a promising therapeutic strategy against human cancer.

A case of osteonecrosis of the jaw in a breast cancer patient with bone metastases receiving long-term treatment with bisphosphonates.

Bisphosphonates (BPs) are often used for the treatment of several diseases such as osteoporosis, cancer-associated hypercalcemia, and osteolytic bone metastasis. Recently, there have been reports of osteonecrosis of the jaw (ONJ) in cancer patients whose treatment regimens include BPs. In this case report, we describe complications and treatment of ONJ in a breast cancer patient with bone metastases who received long-term treatment with BPs. A 70-year-old woman underwent modified radical mastectomy on her left breast cancer and received oral 5-fluorouracil derivatives for 2 years in another hospital. Eleven years after the surgery, she came to our hospital complaining of spinalgia and was diagnosed with recurrent breast cancer with multiple metastases to the stomach, liver, multiple lymph nodes, and spine. After surgery for spine metastases, she was given a combination therapy of trastuzumab (initial bolus: 170 mg/body, followed by two or more cycles of 85 mg/body) every week, docetaxel (100 mg/body) every 3 weeks, and BPs (90 mg/body) every 4 weeks. About 1 year and 4 months later, she complained of pain in her right maxilla; biopsy revealed ONJ. Medical oncologists need to recognize ONJ as a serious side effect of BP treatment; dentists and oral and maxillofacial surgeons need to thoroughly consult patients regarding the administration of BPs and have them make an informed consent.