Loss of KAP3 decreases intercellular adhesion and impairs intracellular transport of laminin in signet ring cell carcinoma of the stomach.

Signet-ring cell carcinoma (SRCC) is a unique subtype of gastric cancer that is impaired for cell-cell adhesion. The pathogenesis of SRCC remains unclear. Here, we show that expression of kinesin-associated protein 3 (KAP3), a cargo adaptor subunit of the kinesin superfamily protein 3 (KIF3), a motor protein, is specifically decreased in SRCC of the stomach. CRISPR/Cas9-mediated gene knockout experiments indicated that loss of KAP3 impairs the formation of circumferential actomyosin cables by inactivating RhoA, leading to the weakening of cell-cell adhesion. Furthermore, in KAP3 knockout cells, post-Golgi transport of laminin, a key component of the basement membrane, was inhibited, resulting in impaired basement membrane formation. Together, these findings uncover a potential role for KAP3 in the pathogenesis of SRCC of the stomach.

miR-766-5p Targets Super-Enhancers by Downregulating CBP and BRD4.

Super-enhancers (SE) are clusters of transcription enhancers that drive gene expression. SEs are typically characterized by high levels of acetylation of histone H3 lysine 27 (H3K27ac), which is catalyzed by the histone lysine acetyltransferase CREB binding protein (CBP). Cancer cells frequently acquire tumor-specific SEs at key oncogenes, such as MYC, which induce several hallmarks of cancer. BRD4 is recruited to SEs and consequently functions as an epigenetic reader to promote transcription of SE-marked genes in cancer cells. miRNAs can be potent candidates for nucleic acid therapeutics for cancer. We previously identified miR-766-5p as a miRNA that downregulated MYC expression and inhibited cancer cell growth in vitro. In this study, we show that miR-766-5p directly targets CBP and BRD4. Concurrent suppression of CBP and BRD4 cooperatively downregulated MYC expression in cancer cells but not in normal cells. Chromatin immunoprecipitation analysis revealed that miR-766-5p reduced levels of H3K27ac at MYC SEs via CBP suppression. Moreover, miR-766-5p suppressed expression of a BRD4-NUT fusion protein that drives NUT midline carcinoma. In vivo administration of miR-766-5p suppressed tumor growth in two xenograft models. Collectively, these data suggest that targeting SEs using miR-766-5p-based therapeutics may serve as an effective strategy for the treatment of MYC-driven cancers. SIGNIFICANCE: This study demonstrates that miR-766-5p targets CBP and BRD4, which can mitigate the protumorigenic consequences of SEs and oncogenic fusion proteins.

Concurrent targeting of MAP3K3 and BRD4 by miR-3140-3p overcomes acquired resistance to BET inhibitors in neuroblastoma cells.

Neuroblastoma (NB) harboring MYCN amplification is a refractory disease with a poor prognosis. As BRD4, an epigenetic reader belonging to the bromodomain and extra terminal domain (BET) family, drives transcription of MYCN in NB cells, BET inhibitors (BETis) are considered useful for NB therapy. However, clinical trials of BETis suggested that early acquired resistance to BETis limits their therapeutic benefit. MicroRNAs are small non-coding RNAs that mediate post-transcriptional silencing of target genes. We previously identified miR-3140-3p as a potent candidate for nucleic acid therapeutics for cancer, which directly targets BRD4. We demonstrated that miR-3140-3p suppresses tumor cell growth in MYCN-amplified NB by downregulating MYCN and MYC through BRD4 suppression. We established BETi-acquired resistant NB cells to evaluate the mechanism of resistance to BETi in NB cells. We revealed that activated ERK1/2 stabilizes MYCN protein by preventing ubiquitin-mediated proteolysis via phosphorylation of MYCN at Ser62 in BETi-acquired resistant NB cells, thereby attenuating the effects of BETi in these cells. miR-3140-3p efficiently downregulated MYCN expression by directly targeting the MAP3K3-ERK1/2 pathway in addition to BRD4 suppression, inhibiting tumor cell growth in BETi-acquired resistant NB cells. This study suggests that miR-3140-3p has the potential to overcome resistance to BETi in NB.

SOX2 enhances cell survival and induces resistance to apoptosis under serum starvation conditions through the AKT/GSK-3ß signaling pathway in esophageal squamous cell carcinoma.

The human SOX2 gene was recently identified as a novel major oncogene, recurrently amplified and overexpressed in esophageal squamous cell carcinoma (ESCC). However, the role and molecular mechanism of SOX2 in the carcinogenesis of ESCC remain to be elucidated. The present study investigated the effect of SOX2 on ESCC cell survival and resistance to apoptosis under serum starvation conditions. An adenoviral vector-mediated expression system and RNA interference were used to study the effect of SOX2. The present results revealed that SOX2 promoted ESCC cell survival and enhanced resistance to apoptosis under serum starvation conditions, but not in culture conditions with serum. Mechanistically, SOX2 increased the expression levels of phosphorylated AKT and glycogen synthase kinase-3ß (GSK-3ß), a downstream factor of AKT, under serum starvation conditions, leading to the promotion of ESCC cell survival. Additionally, SOX2 activated AKT through the PTEN/PI3K/phosphoinositide-dependent protein kinase 1 and mammalian target of rapamycin complex 2 signaling pathways. Therefore, SOX2 may facilitate the survival of ESCC cells under poor nutrient conditions by activating the AKT/GSK-3ß signaling pathway.

miR-1293, a Candidate for miRNA-Based Cancer Therapeutics, Simultaneously Targets BRD4 and the DNA Repair Pathway.

BRD4, a member of the bromodomain and extra-terminal domain (BET) protein family, plays a role in the organization of super-enhancers and transcriptional activation of oncogenes in cancer and is recognized as a promising target for cancer therapy. microRNAs (miRNAs), endogenous small noncoding RNAs, cause mRNA degradation or inhibit protein translation of their target genes by binding to complementary sequences. miRNA mimics simultaneously targeting several tumor-promoting genes and BRD4 may be useful as therapeutic agents of tumor-suppressive miRNAs (TS-miRs) for cancer therapy. To investigate TS-miRs for the development of miRNA-based cancer therapeutics, we performed function-based screening in 10 cancer cell lines with a library containing 2,565 human miRNA mimics. Consequently, miR-1293, miR-876-3p, and miR-6571-5p were identified as TS-miRs targeting BRD4 in this screening. Notably, miR-1293 also suppressed DNA repair pathways by directly suppressing the DNA repair genes APEX1 (apurinic-apyrimidinic endonuclease 1), RPA1 (replication protein A1), and POLD4 (DNA polymerase delta 4, accessory subunit). Concurrent suppression of BRD4 and these DNA repair genes synergistically inhibited tumor cell growth in vitro. Furthermore, administration of miR-1293 suppressed in vivo tumor growth in a xenograft mouse model. These results suggest that miR-1293 is a candidate for the development of miRNA-based cancer therapeutics.

Blue laser imaging-bright improves the real-time detection rate of early gastric cancer: a randomized controlled study.

BACKGROUND AND AIMS: Blue laser imaging-bright (BLI-bright) has shown promise as a more useful tool for detection of early gastric cancer (EGC) than white-light imaging (WLI). However, the diagnostic performance of BLI-bright in the detection of EGC has not been investigated. We aimed to compare real-time detection rates of WLI with that of BLI-bright for EGC. METHODS: This was a prospective, randomized, controlled study in 2 Japanese academic centers. We investigated 629 patients undergoing follow-up endoscopy for atrophic gastritis with intestinal metaplasia or surveillance after endoscopic resection of EGC. Patients were randomly assigned to receive primary WLI followed by BLI-bright or primary BLI-bright followed by WLI. The real-time detection rates of EGC were compared between primary WLI and primary BLI-bright. RESULTS: There were 298 patients in each group. The real-time detection rate of EGC with primary BLI-bright was significantly greater than that with primary WLI (93.1% vs 50.0%; P = .001). Primary BLI-bright had a significantly greater ability to detect EGCs in patients with a history of endoscopic resection for EGC, no Helicobacter pylori infection in the stomach after eradication therapy, lesions with an open-type atrophic border, lesions in the lower third of the stomach, depressed-type lesions, small lesions measuring <10 mm and 10 to 20 mm in diameter, reddish lesions, well-differentiated adenocarcinomas, and lesions with a depth of invasion of T1a. CONCLUSIONS: BLI-bright has a higher real-time detection rate for EGC than WLI. BLI-bright should be performed during surveillance endoscopy in patients at high risk for EGC. (Clinical trial registration number: UMIN000011324.).

Oncogenic miR-96-5p inhibits apoptosis by targeting the caspase-9 gene in hepatocellular carcinoma.

The aberrant expression or alteration of microRNAs (miRNAs/miRs) contributes to the development and progression of cancer. In the present study, the functions of miR-96-5p in hepatocellular carcinoma (HCC) were investigated. It was identified that miR-96-5p expression was significantly upregulated in primary HCC tumors compared with their non-tumorous counterparts. A copy number gain was frequently observed at chromosomal region 7q32.2 in which the MIR96 locus is located, suggesting that gene amplification may be one of the mechanisms by which miR-96-5p expression is increased in HCC. Transfection of miR-96-5p mimic into HCC cells decreased the expression of CASP9, which encodes caspase-9, the essential initiator caspase in the mitochondrial apoptotic pathway, at the mRNA and protein levels. A putative binding site for miR-96-5p was identified in the CASP9 3'-untranslated region, and the results of a luciferase assay indicated that CASP9 is a potential direct target of miR-96-5p. The miR-96-5p mimic increased resistance to doxorubicin- and ultraviolet-induced apoptosis through the decrease in caspase-9 expression in HCC cells. Transfection of miR-96-5p inhibitor enhanced the cytotoxic effect of doxorubicin by increasing caspase-9 expression in the HCC cells, suggesting a synergistic effect between the miR-96-5p inhibitor and doxorubicin. In conclusion, the results of the present study suggest that miR-96-5p, which is frequently upregulated in HCC, inhibits apoptosis by targeting CASP9. Therefore, miR-96-5p may be a potential therapeutic target for HCC.

Publisher Correction: miR-3140 suppresses tumor cell growth by targeting BRD4 via its coding sequence and downregulates the BRD4-NUT fusion oncoprotein.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

miR-3140 suppresses tumor cell growth by targeting BRD4 via its coding sequence and downregulates the BRD4-NUT fusion oncoprotein.

Bromodomain Containing 4 (BRD4) mediates transcriptional elongation of the oncogene MYC by binding to acetylated histones. BRD4 has been shown to play a critical role in tumorigenesis in several cancers, and the BRD4-NUT fusion gene is a driver of NUT midline carcinoma (NMC), a rare but highly lethal cancer. microRNAs (miRNAs) are endogenous small non-coding RNAs that suppress target gene expression by binding to complementary mRNA sequences. Here, we show that miR-3140, which was identified as a novel tumor suppressive miRNA by function-based screening of a library containing 1090 miRNA mimics, directly suppressed BRD4 by binding to its coding sequence (CDS). miR-3140 concurrently downregulated BRD3 by bind to its CDS as well as CDK2 and EGFR by binding to their 3' untranslated regions. miR-3140 inhibited tumor cell growth in vitro in various cancer cell lines, including EGFR tyrosine kinase inhibitor-resistant cells. Interestingly, we found that miR-3140 downregulated the BRD4-NUT fusion protein and suppressed in vitro tumor cell growth in a NMC cell line, Ty-82 cells. Furthermore, administration of miR-3140 suppressed in vivo tumor growth in a xenograft mouse model. Our results suggest that miR-3140 is a candidate for the development of miRNA-based cancer therapeutics.

ASPP2 suppresses invasion and TGF-ß1-induced epithelial-mesenchymal transition by inhibiting Smad7 degradation mediated by E3 ubiquitin ligase ITCH in gastric cancer.

ASPP2 regulates cell polarity and cell-cell adhesion by binding to, and co-localizing with PAR3 at tight junctions. Here we show a novel role of ASPP2 in suppressing gastric cancer (GC) invasiveness. Immunoprecipitation and immunofluorescence analyses showed that ASPP2 promoted the recruitment of PAR3 to cell-cell junctions in GC cells. Diminished expression of ASPP2 and loss of junctional PAR3 localization were significantly associated with diffuse-type histology, deeper invasion depth, positive peritoneal dissemination and worse prognosis in primary GC. ASPP2 suppressed migration and invasion of GC cells in vitro and peritoneal dissemination of GC cells in vivo in a mouse model. ASPP2 suppressed epithelial-mesenchymal transition (EMT) induced by TGF-ß1-Smad2/3 signaling in GC cells through suppression of the degradation of Smad7, a negative regulator of TGF-ß1-Smad2/3 signaling, by interacting with the E3 ubiquitin ligase ITCH. In conclusion, ASPP2 suppresses invasion, peritoneal dissemination and TGF-ß1-induced EMT by inhibiting Smad7 degradation mediated by ITCH.

Loss of PAR-3 protein expression is associated with invasion, lymph node metastasis, and poor survival in esophageal squamous cell carcinoma.

Disrupted cell polarity is a feature of epithelial cancers. The partitioning defective 3 (PAR-3) protein, a key component of the PAR complex that regulates the polarization of cells, is involved in tight junction formation at epithelial cell-cell contacts. Our previous study detected a homozygous deletion of the PAR-3 gene in esophageal squamous cell carcinoma (ESCC) cell lines and frequent copy number loss of the PAR-3 gene in primary ESCC. Here, we aimed to investigate the clinicopathological relevance of altered expression of the PAR-3 protein in primary ESCC. We immunohistochemically analyzed expression of the PAR-3 protein, as well as that of other tight junction proteins, ZO-1 and claudin-1, in 74 primary ESCCs. While the PAR-3 protein was expressed in the cytoplasm of basal cells, it was localized on the plasma membrane of suprabasal cells of normal squamous epithelium of the esophagus. Of the 74 ESCC tumors, 20 (27%), 11 (15%), and 13 (18%) were negative for PAR-3, ZO-1, and claudin-1 proteins, respectively. Negative PAR-3 protein expression, but not negative ZO-1 or claudin-1 expression, was significantly associated with deeper tumor invasion (P<.01), positive lymph node metastasis (P=.03), and advanced tumor stage (P=.01). Patients with PAR-3-negative tumors showed marginally significantly shorter overall survival after surgery than those with PAR-3-positive tumors (P=.053). In conclusion, these results suggest that PAR-3 protein expression is frequently lost in primary ESCC and that loss of the PAR-3 protein is associated with aggressive clinicopathological features of ESCC.

A case of gastric hamartomatous inverted polyp resected endoscopically.

We report the case of a 55-year-old woman with a tumor in the greater curvature of the upper gastric body. The tumor was incidentally found on an upper gastrointestinal X-ray series performed during a routine medical examination. Whereas endoscopy revealed a gastric submucosal tumor (SMT), endoscopic ultrasonography demonstrated a heterogeneous tumor with small, cystic, hypoechoic spots originating from the second layer. The patient was clinically asymptomatic, with no contributory family history or abnormal laboratory data. The results of a physical examination, abdominal computed tomography, and plain chest radiography were all unremarkable. Although the endoscopic tumor type was determined to be SMT, the tumor was successfully resected by endoscopic submucosal dissection (ESD) and subsequently diagnosed as a gastric hamartomatous inverted polyp (GHIP). The findings of the present case highlight the importance of considering GHIP as a diagnosis and indicate the utility of en bloc resection of GHIP with ESD.

The amino acid-rich elemental diet Elental® preserves lean body mass during chemo- or chemoradiotherapy for esophageal cancer.

Chemo (chemoradio) therapy can induce oral mucositis and change body composition in patients with esophageal cancer. The impact of the amino acid-rich elemental diet Elental® on oral mucositis and changes in body composition during chemo (chemoradio) therapy is unclear. Thus, the purpose of the present study was to examine the preventive effects of Elental on oral mucositis and sarcopenia progression during chemo (chemoradio) therapy for esophageal cancer. Patients were randomized to receive either azulene oral rinse (Arm 1) or Elental (Arm 2) during the treatment cycle (4 weeks). The incidence of oral mucositis and other adverse events was evaluated weekly. Body composition pre- and post-treatment cycle was measured by bioelectric impedance analysis. Thirty­three patients (17 azulene and 16 Elental) completed the study, and the groups were well matched. Elental tended to reduce the incidence of oral mucositis (Arm 1, 23.5% and Arm 2, 12.5%), but there was no statistically significant difference between the groups. The average body mass index (BMI) and body fat mass decreased significantly in both groups after the treatments. Lean body mass (LBM) was reduced in Arm 1, but was increased in Arm 2 after the treatment; the relative change of LBM after the treatment was significant between Arm 1 and Arm 2 (P=0.007). This study revealed that Elental nutrition could counteract sarcopenia development during chemoradiotherapy for esophageal cancer. These properties may lead to improvement of the quality of life and clinical outcome of esophageal cancer patients treated with chemo (chemoradio) therapy (Clinical Trial Registry ID: UMIN 000007960).

Genome-wide DNA methylation analysis in hepatocellular carcinoma.

Epigenetic changes as well as genetic changes are mechanisms of tumorigenesis. We aimed to identify novel genes that are silenced by DNA hypermethylation in hepatocellular carcinoma (HCC). We screened for genes with promoter DNA hypermethylation using a genome-wide methylation microarray analysis in primary HCC (the discovery set). The microarray analysis revealed that there were 2,670 CpG sites that significantly differed in regards to the methylation level between the tumor and non-tumor liver tissues; 875 were significantly hypermethylated and 1,795 were significantly hypomethylated in the HCC tumors compared to the non­tumor tissues. Further analyses using methylation-specific PCR, combined with expression analysis, in the validation set of primary HCC showed that, in addition to three known tumor-suppressor genes (APC, CDKN2A, and GSTP1), eight genes (AKR1B1, GRASP, MAP9, NXPE3, RSPH9, SPINT2, STEAP4, and ZNF154) were significantly hypermethylated and downregulated in the HCC tumors compared to the non-tumor liver tissues. Our results suggest that epigenetic silencing of these genes may be associated with HCC.

EVI1, a target gene for amplification at 3q26, antagonizes transforming growth factor-ß-mediated growth inhibition in hepatocellular carcinoma.

EVI1 (ecotropic viral integration site 1) is one of the most aggressive oncogenes associated with myeloid leukemia. We investigated DNA copy number aberrations in human hepatocellular carcinoma (HCC) cell lines using a high-density oligonucleotide microarray. We found that a novel amplification at the chromosomal region 3q26 occurs in the HCC cell line JHH-1, and that MECOM (MDS1 and EVI1 complex locus), which lies within the 3q26 region, was amplified. Quantitative PCR analysis of the three transcripts transcribed from MECOM indicated that only EVI1, but not the fusion transcript MDS1-EVI1 or MDS1, was overexpressed in JHH-1 cells and was significantly upregulated in 22 (61%) of 36 primary HCC tumors when compared with their non-tumorous counterparts. A copy number gain of EVI1 was observed in 24 (36%) of 66 primary HCC tumors. High EVI1 expression was significantly associated with larger tumor size and higher level of des-γ-carboxy prothrombin, a tumor marker for HCC. Knockdown of EVI1 resulted in increased induction of the cyclin-dependent kinase inhibitor p15(INK) (4B) by transforming growth factor (TGF)-ß and decreased expression of c-Myc, cyclin D1, and phosphorylated Rb in TGF-ß-treated cells. Consequently, knockdown of EVI1 led to reduced DNA synthesis and cell viability. Collectively, our results suggest that EVI1 is a probable target gene that acts as a driving force for the amplification at 3q26 in HCC and that the oncoprotein EVI1 antagonizes TGF-ß-mediated growth inhibition of HCC cells.

L-menthol improves adenoma detection rate during colonoscopy: a randomized trial.

BACKGROUND AND STUDY AIMS: Colonoscopy is one of the most reliable methods for the detection of colorectal neoplasms. However, colonic peristalsis during colonoscopy results in some neoplastic lesions being hidden from view and commonly requires an intravenous or intramuscular injection of antispasmodic agents, which may sometimes causes unexpected adverse reactions. The aim of this study was to evaluate the efficacy of L-menthol spray as an antiperistaltic agent and its effect on adenoma detection. PATIENTS AND METHODS: This was a prospective, randomized, single-blind placebo-controlled trial. A total of 226 patients who were scheduled to undergo colonoscopy were randomly assigned to receive either 20 mL of 1.6 % L-menthol (n = 118) or placebo (n = 108). Both treatments were sprayed locally onto the colonic mucosa via an endoscope. The adenoma detection rate (ADR) and the proportion of patients with no peristalsis were the primary and secondary outcomes, respectively. RESULTS: The ADR was significantly higher in the L-menthol group than in the placebo group (60.2 % vs. 42.6 %; P = 0.0083). The proportion of patients with no peristalsis after treatment with L-menthol was significantly higher than in the placebo group (71.2 % vs. 30.9 %; P < 0.0001). There were no adverse effects in either group. CONCLUSIONS: The results suggest that the suppression of colonic peristalsis by L-menthol sprayed directly onto the colonic mucosa improves the ADR. CLINICAL TRIAL REGISTRATION: ID: UMIN 000007972.

Endoscopic transgastric drainage of a gastric wall abscess after endoscopic submucosal dissection.

A 63-year-old woman was referred to our hospital for further examination because of an incidental finding of early gastric cancer. Endoscopic submucosal dissection (ESD) was successfully performed for complete resection of the tumor. On the first post-ESD day, the patient suddenly complained of abdominal pain after an episode of vomiting. Abdominal computed tomography (CT) showed delayed perforation after ESD. The patient was conservatively treated with an intravenous proton pump inhibitor and antibiotics. On the fifth post-ESD day, CT revealed a gastric wall abscess in the gastric body. Gastroscopy revealed a gastric fistula at the edge of the post-ESD ulcer, and pus was found flowing into the stomach. An intradrainage stent and an extradrainage nasocystic catheter were successfully inserted into the abscess for endoscopic transgastric drainage. After the procedure, the clinical symptoms and laboratory test results improved quickly. Two months later, a follow-up CT scan showed no collection of pus. Consequently, the intradrainage stent was removed. Although the gastric wall abscess recurred 2 wk after stent removal, it recovered soon after endoscopic transgastric drainage. Finally, after stent removal and oral antibiotic treatment for 1 mo, no recurrence of the gastric wall abscess was found.

Aberrant expression of the PHF14 gene in biliary tract cancer cells.

DNA copy number aberrations in human biliary tract cancer (BTC) cell lines were investigated using a high-density oligonucleotide microarray. A novel homozygous deletion was detected at chromosomal region 7p21.3 in the OZ cell line. Further validation experiments using genomic PCR revealed a homozygous deletion of a single gene, plant homeodomain (PHD) finger protein 14 (PHF14). No PHF14 mRNA or protein expression was detected, thus demonstrating the absence of PHF14 expression in the OZ cell line. Although the PHD finger protein is considered to be involved in chromatin-mediated transcriptional regulation, little is known about the function of PHF14 in cancer. The present study observed that the knock down of PHF14 using small interfering RNA (siRNA) enhanced the growth of the BTC cells. These observations suggest that aberrant PHF14 expression may have a role in the tumorigenesis of BTC.

SOX2 promotes tumor growth of esophageal squamous cell carcinoma through the AKT/mammalian target of rapamycin complex 1 signaling pathway.

The transcription factor SOX2 is essential for the maintenance of embryonic stem cells and normal development of the esophagus. Our previous study revealed that the SOX2 gene is an amplification target of 3q26.3 in esophageal squamous cell carcinoma (ESCC), and that SOX2 promotes ESCC cell proliferation in vitro. In the present study, we aimed to identify the mechanisms by which SOX2 promotes proliferation of ESCC cells. Using a phosphoprotein array, we assayed multiple signaling pathways activated by SOX2 and determined that SOX2 activated the AKT/mammalian target of rapamycin complex 1 (mTORC1) signaling pathway. LY294002, an inhibitor of phosphatidylinositol 3-kinase, and rapamycin, an inhibitor of mTORC1, suppressed the ability of SOX2 to enhance proliferation of ESCC cells in vitro. Effects of SOX2 knockdown, including reduced levels of phosphorylated AKT and decreased ESCC cell proliferation, were reversed with constitutive activation of AKT with knockdown of phosphatase and tensin homolog. In mouse xenografts, SOX2 promoted in vivo tumor growth of ESCC, which was dependent on AKT/mTORC1 activation. LY294002 suppressed the ability of SOX2 to enhance tumor growth of ESCC by reducing cell proliferation, but not by enhancing apoptosis. Furthermore, tissue microarray analysis of 61 primary ESCC tumors showed a positive correlation between expression levels of SOX2 and phosphorylated AKT. Our findings suggest that SOX2 promotes in vivo tumor growth of ESCC through activation of the AKT/mTORC1 signaling pathway, which enhances cell proliferation.

Alterations of the SWI/SNF chromatin remodelling subunit-BRG1 and BRM in hepatocellular carcinoma.

BACKGROUND: The SWI/SNF chromatin remodelling complex, which contains either brahma-related gene-1 (BRG1) or brahma (BRM) as the catalytic ATPase, functions as a master regulator of gene expression. AIMS: To examine alterations of BRG1 and BRM in hepatocellular carcinoma (HCC). METHODS: We investigated DNA copy number aberrations in human HCC cell lines using a high-density oligonucleotide microarray. We determined DNA copy numbers and expression levels of BRG1 and BRM genes in primary HCC tumours, and conducted further searches for mutations in BRG1 and BRM genes. RESULTS: Homozygous deletion of the BRG1 gene was found in HCC cell line SNU398. Copy number losses of BRG1 and BRM genes were observed in 14 (26%) and 7 (13%) of 54 primary HCC tumours respectively. We found four somatic missense mutations in the BRG1 gene in two of 36 primary HCC tumours, but no mutations in BRM gene. Expression of BRM mRNA, but not BRG1 mRNA, was significantly reduced in primary HCC tumours, compared to non-tumour tissue counterparts. Immunohistochemical analyses of non-tumour liver tissues showed that BRM protein was expressed in hepatocytes and bile-duct epithelial cells, whereas BRG1 protein was expressed in bile-duct epithelial cells, but not in hepatocytes. BRM protein expression was lost in nine (22.5%) of 40 HCC tumours. Loss of BRM protein expression was significantly associated with poor overall survival. CONCLUSION: Reduced expression of BRM may contribute to the carcinogenesis of HCC. Although deletions and mutations in BRG1 gene were identified, the role of BRG1 in HCC tumourigenesis remains unclear.