RNASEN regulates cell proliferation and affects survival in esophageal cancer patients

PURPOSE

MicroRNAs (miRNA) are small noncoding RNAs thought to be involved in physiologic and developmental processes by negatively regulating the expression of target genes. Little is known about the role of miRNAs in normal and cancer cells. It is possible that deregulation of miRNA may contribute to the oncogenesis of some cancers. We studied the expression level of the miRNA processing enzyme (DICER1, DGCR8, and RNASEN) in esophageal squamous cell carcinoma (ESCC).

EXPERIMENTAL DESIGN

The expression levels of DICER1, DGCR8, and RNASEN mRNA in 73 ESCC tissues were compared with that in corresponding normal esophageal epithelium by Taqman real-time reverse-transcription PCR. We also examined RNASEN protein expression in 27 cell lines. The role of RNASEN in cell proliferation in ESCC cells was assessed by small interfering RNA. Paraffin sections of ESCC patients were immunohistochemically investigated.

RESULTS

We found that RNASEN expression levels were enhanced in a fraction of esophageal cancers. Multivariate Cox regression analysis showed that the prognostic effect of RNASEN (P = 0.0036) seems to be independent of disease stage (P = 0.0060). Knockdown of RNASEN in esophageal cancer cell lines resulted in a 46% to 85% reduction in cell number. In an immunohistochemical study, the intensity of RNASEN expression was often increased in the tumor compared with that in normal epithelium.

CONCLUSIONS

The relationship between the RNASEN expression and the prognosis of the ESCC patients warrants a further study on the role of miRNA and tumor progression.

Counterbalance between RB inactivation and miR-17-92 overexpression in reactive oxygen species and DNA damage induction in lung cancers

Small-cell lung cancer (SCLC) is a highly aggressive disease that exhibits rapid growth and genetic instability. We found earlier frequent overexpression of the miR-17-92 microRNA cluster, and showed that SCLC cells were addicted to continued expressions of miR-17-5p and miR-20a, major components of this microRNA cluster. In this study, we identified the frequent presence of constitutively phosphorylated H2AX (gamma-H2AX), which reflects continuing DNA damage, preferentially in SCLC. Knockdown of RB induced gamma-H2AX foci formation in non-small cell lung cancer (NSCLC) cells with wild-type RB, in association with growth inhibition and reactive oxygen species (ROS) generation, which was canceled by overexpression of miR-17-92. Conversely, induction of gamma-H2AX was observed in a miR-17-92-overexpressing SCLC cell line with miR-20a antisense oligonucleotides. These findings suggest that miR-17-92 overexpression may serve as a fine-tuning influence to counterbalance the generation of DNA damage in RB-inactivated SCLC cells, thus reducing excessive DNA damage to a tolerable level and consequently leading to genetic instability. Therefore, miR-17-92 may be an excellent therapeutic target candidate to elicit excessive DNA damage in combination with DNA-damaging chemotherapeutics.

Identification of Decatenation G2 Checkpoint Impairment Independently of DNA Damage G2 Checkpoint in Human Lung Cancer Cell Lines

It has been suggested that attenuation of the decatenation G(2) checkpoint function, which ensures sufficient chromatid decatenation by topoisomerase II before entering into mitosis, may contribute to the acquisition of genetic instability in cancer cells. To date, however, very little information is available on this type of checkpoint defect in human cancers. In this study, we report for the first time that a proportion of human lung cancer cell lines did not properly arrest before entering mitosis in the presence of a catalytic, circular cramp-forming topoisomerase II inhibitor ICRF-193, whereas the decatenation G(2) checkpoint impairment was present independently of the impaired DNA damage G(2) checkpoint. In addition, the presence of decatenation G(2) checkpoint dysfunction was found to be associated with diminished activation of ataxia-telangiectasia mutated in response to ICRF-193, suggesting the potential involvement of an upstream pathway sensing incompletely catenated chromatids. Interestingly, hypersensitivity to ICRF-193 was observed in cell lines with decatenation G(2) checkpoint impairment and negligible activation of ataxia-telangiectasia mutated. These findings suggest the possible involvement of decatenation G(2) checkpoint impairment in the development of human lung cancers, as well as the potential clinical implication of selective killing of lung cancer cells with such defects by this type of topoisomerase II inhibitor.

Decreased expression of NDRG1 is correlated with tumor progression and poor prognosis in patients with esophageal squamous cell carcinoma

NDRG1 (N-myc downstream regulated gene-1) was reported to be necessary for p53-mediated apoptosis and to be regulated by PTEN (phosphatase and tensin homolog). In several cancers, it was suggested to be a tumor suppressor gene. Its significance in esophageal squamous cell carcinoma (ESCC) has not been studied. The objective of this study was to clarify the relation between clinicopathological and biologic factors in esophageal carcinoma and to determine the prognostic significance of the expression of NDRG1. Expression of NDRG1 mRNA was quantified by real-time reverse transcription polymerase chain reaction using a Lightcycler in 47 esophageal ESCC specimens. The data were analyzed with reference to clinicopathological factors. Among the esophageal cancer tissues, NDRG1 mRNA expression was significantly lower in tumors of more advanced pathological stage (0-I vs. II-IV; P = 0.0027) and local tumor invasion (T1-2 vs. T3-4; P = 0.0136). Patients who had low NDRG1 mRNA expression had a significantly shorter survival after surgery compared with patients who had high NDRG1 mRNA expression (log-rank test, P = 0.0478). Impaired NDRG1 expression may lead to more aggressive invasion of ESCC.

CLCP1 interacts with semaphorin 4B and regulates motility of lung cancer cells

We previously established a highly metastatic subline, LNM35, from the NCI-H460 lung cancer cell line, and demonstrated upregulation of a novel gene, CLCP1 (CUB, LCCL-homology, coagulation factor V/VIII homology domains protein), in LNM35 and lung cancer specimens. In this study, we focused on the potential roles of that gene in cancer metastasis. First, we established stable LNM35 RNAi clones, in which CLCP1 expression was suppressed by RNAi, and found that their motility was significantly reduced, although growth rates were not changed. Next, in vitro selection of a phage display library demonstrated that a phage clone displaying a peptide similar to a sequence within the Sema domain of semaphorin 4B (SEMA4B) interacted with LNM35. Immunoprecipitation experiments confirmed interaction of CLCP1 with SEMA4B, regulation of CLCP1 protein by ubiquitination and proteasome degradation enhanced in the presence of SEMA4B. These results are the first to indicate that CLCP1 plays a role in cell motility, whereas they also showed that at least one of its ligands is SEMA4B and that their interaction mediates proteasome degradation by CLCP1. Although the physiological role of the interaction between CLCP1 and SEMA4B remains to be investigated, this novel gene may become a target of therapy to inhibit metastasis of lung cancers.

Novel NBS1 heterozygous germ line mutation causing MRE11-binding domain loss predisposes to common types of cancer

DNA damage response (DDR) pathways maintain genomic stability. A 657del5 mutation of NBS1, a key DDR component, causing the rare cancer-predisposing Nijmegen breakage syndrome has been reported nearly exclusively in Slavic populations. In this study, we describe the first identification in a Japanese population of an unprecedented type of heterozygous NBS1 mutant, termed IVS11+2insT, lacking the MRE11- and ATM-binding site at the COOH terminus. Profoundly defective in crucial binding to MRE11, MDC1, BRCA1, and wild-type NBS1, the mutant caused impaired ATM phosphorylation in response to low-dose irradiation in a heterozygous state. Importantly, whereas IVS11+2insT was found in only 2 (0.09%) of 2,348 control subjects, it was identified in 2% (2 of 96) of heterozygotes with gastric cancer, 0.8% (3 of 376) of those with colorectal cancer, and 0.4% (2 of 532) of those with lung cancer, which were comparable to frequencies reported for other DDR-related genes known to confer cancer susceptibility. The presence of the heterozygous IVS11+2insT mutation seemed to be associated with an increased risk for gastrointestinal cancers, with an odds ratio of 12.6 and 95% confidence interval (95% CI) of 2.05 to 132.1 (P = 0.0001). The odds ratios separately calculated for gastric and colorectal cancers were 25.0 (95% CI, 1.78-346.0) and 9.43 (95% CI, 1.08-113.1), respectively. These findings suggest that IVS11+2insT is associated with an increased risk for the development of certain types of common cancers, warranting future investigation including detailed phenotypic characterization of age of onset and penetrance in heterozygotes, as well as screening in other ethnic groups.

Histone modification in the TGFbetaRII gene promoter and its significance for responsiveness to HDAC inhibitor in lung cancer cell lines

We previously reported silencing of the TGF-beta type II receptor gene (TGFbetaRII), involving histone deacetylation, instead of DNA methylation (DNA-Me). Because different histone modifications may play crucial roles in the epigenetic alterations, we further studied links with silencing of the TGFbetaRII gene promoter in six lung cancer cell lines. ChIP assays demonstrated three chromatin patterns for this gene silencing (Pattern I: histone H3 acetylation (H3-Ac)(+/-)/histone H3 lysine 4 methylation (H3K4-Me)(+)/DNA-Me(-), Pattern II; H3-Ac(-)/H3K4-Me(+/-)/DNA-Me(-), and Pattern III; H3-Ac(-)/H3K4-Me(-)/DNA-Me(+)), indicating possible progressive alterations with H3K4-Me alteration. With exposure to a histone deacetylase inhibitor (HDAC-I), trichostatin A, cell lines with the pattern II demonstrated strong and persistent induction of TGFbetaRII expression, while those with the pattern III showed only weak or no induction. ACC-LC-91 cell line, one of the pattern II examples demonstrated strong and continuous induction of H3K4-Me similar to TGFbetaRII expression. In contrast, ACC-LC-176 with the pattern III showed only weak and transient induction of H3K4-Me, similar to TGFbetaRII expression. Treatment with 5-aza-2'-deoxycytidine (5aza-dC) in addition to HDAC-I resulted in strong and continuous induction of TGFbetaRII expression and H3K4-Me in ACC-LC-176, although 5aza-dC alone was without such effects. In ACC-LC-91, both H3-Ac and H3K4-Me were promptly and simultaneously induced by HDAC-I, and similarly inhibited by wortmannin, a PI3K family inhibitor, together with TGFbetaRII induction. These findings suggested progressive alterations of chromatin configuration including H3K4-Me alteration in TGFbetaRII gene silencing. A possible involvement of a wortmannin-sensitive kinase in histone modification was also suggested.

NOTCH1 activates the Wnt/β-catenin signaling pathway in colon cancer

PURPOSE AND METHODS

The translocation of β-catenin/CTNNB1 to the nucleus activates Wnt signaling and cell proliferation; however, the precise mechanism underlying this phenomenon remains unknown. Previous reports have provided evidence that NOTCH1 is involved in the Wnt signaling pathway. Therefore, we sought to determine the mechanism by which NOTCH1 influences the Wnt/β-catenin pathway. We constructed a vector expressing the NOTCH1 intracellular domain (NICD1) and transfected the vector into HCT116 which has low expression of NICD1. Furthermore, inhibition of NOTCH signal pathway in SW480 which has abundant NICD1 expression, was performed by transfection of siNICD1 or DAPT, gamma secretase inhibitor, treatment. In addition, we evaluated NICD1 and β-catenin localization in colon cancer cell lines and in 189 colon cancer tissue samples and analyzed the correlation between the nuclear localization of NICD1 and the clinicopathological features of colon cancer patients.

RESULTS

Immunohistochemical assays demonstrated that NICD1 and β-catenin exhibited a similar localization pattern in colon cancer tissues. In addition, we found that NICD1 induced the translocation of β-catenin to the nucleus and that NICD1 and β-catenin co-localized in the nucleus. Overexpression of NICD1 increased luciferase activity of Wnt signal pathway. On the other hand, reduction of NICD1 reduced luciferase activity of Wnt signaling pathway. In the 189 analyzed colon cancer cases, multivariate COX regression analysis demonstrated the independent prognostic impact of nuclear localization of NICD1(p=0.0376).

CONCLUSION

NOTCH1 plays a key role in the Wnt pathway and activation of NOTCH1 is associated with the translocation of β-catenin to the nucleus.

Relationship between expression of 5-fluorouracil metabolic enzymes and 5-fluorouracil sensitivity in esophageal carcinoma cell lines

5-Fluorouracil (5-FU) is a key drug in the treatment of esophageal squamous cell carcinoma (ESCC). Gene expression of 5-FU metabolic enzymes such as thymidylate synthase (TS), thymidine phosphorylase (TP), dihydropyrimidine dehydrogenase (DPD) and orotate phosphoribosyl transferase (OPRT), has recently been investigated in order to predict the 5-FU sensitivity of several cancers. We examined the relationship between such gene expression and 5-FU sensitivity in 25 ESCC cell lines. TS, DPD, TP and OPRT mRNA levels were assessed by real-time polymerase chain reaction. The 50% inhibitory concentrations (IC50) of 5-FU in 25 ESCC cell lines were determined by cell proliferation assay. IC50 values for 5-FU ranged from 1.00 to 39.81 micromol/L. There were significant positive correlations between IC50 and TS mRNA expression (R(2) = 0.5781, P < 0.0001) and DPD mRNA expression (R(2) = 0.3573, P = 0.0016). There were no correlations between IC50 and TP or OPRT mRNA expression. TS and DPD mRNA expression levels may be useful indicators in predicting the anti-tumor activity of 5-FU in ESCC.

Thymidylate synthetase and dihydropyrimidine dehydrogenase mRNA levels in esophageal cancer

This study investigated the mRNA levels of thymidylate synthetase (TYMS) and dihydropyrimidine dehydrogenase (DPYD) in esophageal squamous cell carcinoma (ESCC). TYMS and DPYD gene expression was quantified using real-time RT-PCR in 56 patients with ESCC, co-amplified with glyceraldehyde-3-phosphate dehydrogenase as an internal standard. The results were analyzed with reference to the clinicopathological characteristics and the prognosis of the ESCC patients. The TYMS and DPYD expression levels in patients positive with lymphatic invasion were significantly higher compared to those in patients who exhibited negative lymphatic invasion (TYMS P=0.0127, DPYD P=0.0127). Patients were classified into the groups high TYMS/DPYD, high TYMS but low DPYD, low TYMS but high DPYD and low TYMS/DPYD. The highest survival rate was found in the group with low TYMS/DPYD and the lowest survival rate in the group with high TYMS/DPYD (P=0.017). It was concluded that, on the basis of the multivariate analysis, TYMS mRNA expression is a candidate that serves as an independent prognostic factor for ESCC patients.

Frequent loss of the long arm of chromosome 18 in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most common and deadly cancers in Japan. In this study we performed fluorescent in situ hybridization (FISH) and loss of heterozygosity (LOH) analysis for chromosome 18q in ESCC cells to investigate allelic imbalance of chromosome 18q in ESCC. In the FISH analysis, only one signal for chromosome 18q was detected in TE-1 esophageal cancer cells, whereas two signals were detected in TE-2 cells. Two of five resected ESCC samples from patients showed loss of one copy of chromosome 18q. To construct a precise deletion map of chromosome 18q, LOH analysis was performed using 30 microsatellite markers localized to chromosome 18q. LOH was observed in 31 of 46 ESCC samples (67.4%) for at least one locus on chromosome 18q. LOH frequency for individual markers varied from 18.5% (D18S460) to 48.4% (D18S866). Thirteen of 46 ESCC samples (28.3%) showed the loss of most of the long arm of chromosome 18. Lymph node metastasis and vein invasion were significantly associated with the deletion of chromosome 18q. Loss of chromosome 18q may play an important role in the progression of ESCC.

The overexpression of caveolin-1 and caveolin-2 correlates with a poor prognosis and tumor progression in esophageal squamous cell carcinoma

Caveolin-1 (CAV1) and caveolin-2 (CAV2) are the major structural proteins of caveolae. We investigated the relationship between the clinicopathological factors of esophageal squamous cell carcinoma (ESCC) and the expression of CAV1 and CAV2. CAV1 and CAV2 expression were analyzed by quantitative reverse transcription-polymerase chain reaction (RT-PCR) in 15 esophageal cancer cell lines (TE1-15) and a normal esophageal epithelium cell line (Het-1A). CAV1 and CAV2 expression was examined by RT-PCR and immunohistochemical analysis in 47 ESCC specimens. High levels of CAV1 and CAV2 mRNA were detected in TE1-15, but neither CAV1 nor CAV2 mRNA were detected in Het-1A. In the ESCC samples CAV1 and CAV2 mRNA expression in the ESCC samples were significantly higher than in the corresponding normal esophageal mucosa (CAV1, P=0.0024; CAV2, P=0.0136). However, we could not find any significant relationship between CAV1 or CAV2 mRNA expression and clinicopathological factors. Immunostaining for CAV1 was positive in 13 of 47 patients (27.7%), whereas CAV2 was positive in 22 of 47 patients (46.8%). A significant correlation was observed between CAV1 and CAV2 immunostaining and T factor, lymphatic invasion, vein invasion and differentiation. The patients with positive staining for CAV1 or CAV2 had a significantly shorter survival than those with negative staining (P=0.0105 and 0.0424 for CAV1 and CAV2, respectively). These results suggest that positive staining for CAV1 and CAV2 could be a potentially useful prognostic marker of ESCC.

Expression and prognostic roles of PABPC1 in esophageal cancer: correlation with tumor progression and postoperative survival

The prognosis of patients with esophageal cancer remains poor. TNM classification is not sufficient to predict their prognosis, and novel predictive markers of the prognosis of esophageal cancer patients are therefore needed. Poly A binding protein, cytoplasmic 1 (PABPC1) plays a role in post-transcriptional control of mRNA and may be involved in tumorigenesis. PABPC1 expression has not been studied in esophageal cancer. Expression of PABPC1 was quantified by real-time reverse transcription polymerase chain reaction (RT-PCR) using LightCycler in 41 primary esophageal squamous cell carcinomas (ESCCs) and their paired normal esophageal mucosa. We examined the correlation between PABPC1 expression and the clinicopathological factors and prognosis of ESCC patients. Reduced expression of PABPC1 was accompanied by locally invasive tumors (t-factor, p=0.0145) and more advanced tumors (pathologic stage, p=0.0264). Moreover, ESCC patients with low PABPC1 mRNA expression had a significantly shorter postoperative survival time than those with high expression (median survival, 3.1 vs. 6.5 months, p=0.002). In esophageal cancer, reduced expression of PABPC1 was correlated with local tumor progression and poor prognosis after surgery.

A novel gene, RSRC2, inhibits cell proliferation and affects survival in esophageal cancer patients

In Japan and China, esophageal cancer is common and more than 90% of esophageal cancers are squamous cell carcinoma. Esophageal squamous cell carcinoma (ESCC) shows a poor prognosis, but the mechanism of ESCC and target genes for treatment remains unclear. We searched for genes related to ESCC, and identified a novel gene, FLJ11021, which was designated arginine/serine-rich coiled-coil 2 (RSRC2). We sought to determine the role of RSRC2 in the proliferation of esophageal cell lines and to examine the relationship between RSRC2 and clinicopathologic factors and ESCC prognosis. Expression of RSRC2 was quantified by real-time reverse transcription polymerase chain reaction (RT-PCR) in 70 primary ESCCs and paired noncancerous esophageal mucosa. To determine the role of RSRC2 in ESCC cell proliferation, we used vector-based transfection and small interfering RNA methods. Our results show that RSRC2mRNA levels in all ESCC cell lines (TE1-15, excluding TE7) were lower than those in a human esophageal squamous epithelial cell line (Het-1A). Cell proliferation of an ESCC cell line was inhibited by overexpression of RSRC2, while reduced expression was accompanied by tumor progression. RSRC2 expression levels were significantly correlated with depth of invasion, lymph node metastasis, lymphatic invasion and vascular invasion. Moreover, ESCC patients with low RSRC2mRNA expression had significantly shorter post-operative survival time than those with high expression. In vitro study revealed that RSRC2 might play a role in cell proliferation. Our study demonstrated that RSRC2 expression may be a novel tumor suppressor of esophageal cancer cell growth and a prognostic factor in ESCC.

Expression of ACP6 is an independent prognostic factor for poor survival in patients with esophageal squamous cell carcinoma

ACP6 (acid phosphatase 6, lysophosphatidic) is a lysophosphatidic acid (LPA)-specific phosphatase that hydrolyzes LPA to monoacylglycerol and is involved in lipid metabolism in the mitochondria. Its role in oncogenesis and cancer progression has not been studied. In this study, we examined the expression of ACP6 mRNA and evaluated its clinical significance in esophageal squamous cell carcinoma (ESCC). Expression of ACP6 mRNA was quantified by real-time reverse transcription polymerase chain reaction using the LightCycler in 70 esophageal ESCC specimens and their paired normal esophageal mucosa. The data were analyzed with reference to clinicopathological factors. ACP6 mRNA expression in esophageal cancer tissue was significantly lower than that in corresponding normal esophageal mucosa (P=0.0301). Among the esophageal cancer tissues, ACP6 mRNA expression significantly correlated with local tumor invasion (T factor, P=0.0461) and lymph node metastasis (P=0.0128). Furthermore, low ACP6 mRNA expression was associated with a significantly shorter survival time compared with high expression (log-rank test, P=0.0358). In multivariate analysis, ACP6 mRNA expression emerged as a significant independent factor (P=0.0148). Impaired ACP6 expression may lead to more aggressive invasion of ESCC, and ACP6 mRNA expression level could be an independent prognostic factor for patients with ESCC.