Upregulated microRNA‐193a‐3p is responsible for cisplatin resistance in CD44(+) gastric cancer cells

Cisplatin is a well‐known anticancer drug used to treat various cancers. However, development of cisplatin resistance has hindered the efficiency of this drug in cancer treatment. Development of chemoresistance is known to involve many signaling pathways. Recent attention has focused on microRNAs (miRNAs) as potentially important upstream regulators in the development of chemoresistance. CD44 is one of the gastric cancer stem cell markers and plays a role in regulating self‐renewal, tumor initiation, metastasis and chemoresistance. The purpose of the present study was to examine the mechanism of miRNA‐mediated chemoresistance to cisplatin in CD44‐positive gastric cancer stem cells. We sorted gastric cancer cells according to level of CD44 expression by FACS and analyzed their miRNA expression profiles by microarray analysis. We found that miR‐193a‐3p was significantly upregulated in CD44(+) cells compared with CD44(?) cells. Moreover, SRSF2 of miR‐193a‐3p target gene was downregulated in CD44(+) cells. We studied the modulation of Bcl‐X and caspase 9 mRNA splicing by SRSF2 and found that more pro‐apoptotic variants of these genes were generated. We also found that downstream anti‐apoptotic genes such as Bcl‐2 were upregulated, whereas pro‐apoptotic genes such as Bax and cytochrome C were downregulated in CD44(+) cells compared to CD44(?) cells. In addition, we found that an elevated level of miR‐193a‐3p triggered the development of cisplatin resistance in CD44(+) cells. Inhibition of miR‐193a‐3p in CD44(+) cells increased SRSF2 expression and also altered the levels of multiple apoptotic genes. Furthermore, inhibition of miR‐193a‐3p reduced cell viability and increased the number of apoptotic cells. Therefore, miR‐193a‐3p may be implicated in the development of cisplatin resistance through regulation of the mitochondrial apoptosis pathway. miR‐193a‐3p could be a promising target for cancer therapy in cisplatin‐resistant gastric cancer.     

miR‐335 inhibited cell proliferation of lung cancer cells by target Tra2β

Accumulating evidence has suggested that the dysregulation of miRNA is an important factor in the pathogenesis of lung cancer. Here, we demonstrate that miR‐335 expression is reduced in non‐small cell lung cancer (NSCLC) tumors relative to non‐cancerous adjacent tissues, while the expression of Tra2β is increased. In addition, clinical data revealed that the increased Tra2β and decreased miR‐335 expression observed in NSCLC cells was associated with poor patient survival rates. In vitro experimentation showed that the overexpression of miR‐335 inhibited the growth, invasion and migration capabilities of A459 lung cancer cells, by targeting Tra2β. In contrast, inhibition of miR‐335 or overexpression of the Tra2β target gene stimulated the growth, invasion and migratory capabilities of A459 lung cancer cells in vitro. Furthermore, overexpression of miR‐335 or inhibition of Tra2β decreased the phosphorylation of Rb‐S780 and Rb‐AKT. Overall, these findings suggest that the downregulation of miR‐335 in A459 lung cancer cells promoted cell proliferation through upregulation of Tra2β, mediated via activation of the AKT/mTOR signaling pathway, and suggest that miR‐335 may have potential as a novel therapeutic target for NSCLC.     

The intratumoral distribution of nuclear β‐catenin is a prognostic marker in colon cancer

BACKGROUND:

Most colon cancers harbor mutations of APC or β‐catenin, both of which may lead to nuclear β‐catenin accumulation in the tumor cells and constitutively activated expression of its target genes. In many colon cancers, however, nuclear β‐catenin accumulation is heterogeneous throughout the tumor and often confined to the tumor margin. Herein, the authors investigated whether the intratumoral distribution of nuclear β‐catenin can serve as a prognostic marker for survival and tumor progression of stage IIA colon cancer patients.

METHODS:

In total, 142 patients with primarily resected, moderately differentiated stage IIA colon cancer were included in this study. The patterning of nuclear β‐catenin expression was evaluated on immunohistochemically stained whole tissue sections of the tumors and was correlated with cancer‐specific survival and disease‐free survival using univariate and multivariate statistical analyses.

RESULTS:

Four distinct patterns of nuclear β‐catenin expression were identified, and 2 main categories comprising tumors with or without intratumoral regulation of nuclear β‐catenin were distinguished. Moreover, the results demonstrated that the patterning, and especially the regulation or absence of regulation of nuclear β‐catenin expression, was a strong predictive marker of patient survival and tumor progression.

CONCLUSIONS:

The current results indicated that the distribution of nuclear β‐catenin expression can be used as a good prognostic marker in patients with stage IIA colon cancer. Thus, the evaluation of nuclear β‐catenin may help to identify patients who will have a shorter than average survival and patients with a greater risk of disease progression who may be considered for adjuvant therapeutic modalities and intensified clinical aftercare in the future. Cancer 2009. © 2009 American Cancer Society.     

Clinicopathological significance of the microRNA‐146a/WASP‐family verprolin‐homologous protein‐2 axis in gastric cancer

Gastric cancer (GC) is one of the most common malignancies, and cancer invasion and metastasis are the leading causes of cancer‐induced death in GC patients. WASP‐family verprolin‐homologous protein‐2 (WASF2), with a role controlling actin polymerization which is critical in the formation of membrane protrusions involved in cell migration and invasion, has been reported to possess cancer‐promoting effects in several cancers. However, data of WASF2's role in GC are relatively few and even contradictory. In this study, we analyzed WASF2 expression in GC tissues and their corresponding adjacent normal tissues. We found that WASF2 was upregulated in GC tissues and high level of WASF2 was associated with lymph node metastasis of GC. Through gain‐ and loss‐of‐function studies, WASF2 was shown to significantly increase GC cells migration and invasion, but had no effect on proliferation in vitro. Importantly, WASF2 was also found to enhance GC metastasis in vivo. Our previous research suggested that WASF2 was a direct target of microRNA‐146a (miR‐146a). Furthermore, we analyzed miR‐146a's level in GC tissues and their corresponding adjacent normal tissues. We found that miR‐146a was downregulated in GC tissues and low miR‐146a level was associated with advanced TNM stage and lymph node metastasis. The level of WASF2 in GC tissues was negatively correlated with miR‐146a expression and had inverse clinicopathologic features. The newly identified miR‐146a/WASF2 axis may provide a novel therapeutic target for GC.     

Circulating microRNA‐590‐5p functions as a liquid biopsy marker in non‐small cell lung cancer

Despite the availability of various diagnostic procedures, a tissue biopsy is still indispensable for the routine diagnosis of lung cancer. However, inaccurate diagnoses can occur, leading to inefficient cancer management. In this context, use of circulating microRNAs (miRNAs) may serve as diagnostic tools as liquid biopsies, and as biomarkers to better understand the molecular mechanisms involved in the progression of cancer. We identified miR‐590‐5p as a potential prognostic marker in the progression of non‐small cell lung cancer (NSCLC). We were able to detect this miRNA in blood plasma samples of NSCLC patients through quantitative real‐time PCR. Our data showed an ~7.5‐fold downregulation of miR‐590‐5p in NSCLC patients compared to healthy controls, which correlated with several clinicopathological features. Further, overexpression of miR‐590‐5p led to decreased cell viability, proliferation, colony formation, migration, and invasion potential of lung cancer cells, whereas its knockdown showed the opposite effect. In addition, the levels of several proteins involved in the epithelial‐to‐mesenchymal transition negatively correlated with miR‐590‐5p levels in lung adenocarcinoma cells and tumors of NSCLC patients. Further, dual‐luciferase reporter assays identified STAT3 as a direct target of miR‐590‐5p, which negatively regulated STAT3 activation and its downstream signaling molecules (eg, Cyclin D1, c‐Myc, Vimentin, and β‐catenin) involved in tumorigenesis. Taken together, our study suggests that miR‐590‐5p functions as a tumor suppressor in NSCLC through regulating the STAT3 pathway, and may serve as a useful biomarker for the diagnosis/prognosis of NSCLC, and as a potential therapeutic target for the treatment of NSCLC.     

ERGIC3, which is regulated by miR‐203a,is a potential biomarker for non‐small cell lung cancer

In a previous study, we found that ERGIC3 was a novel lung cancer‐related gene by screening libraries of differentially expressed genes. In this study, we developed a new murine monoclonal antibody (mAb) against ERGIC3. This avid antibody (6‐C4) is well suited for immunohistochemistry, immunoblotting and solid‐phase immunoassays. Furthermore, we systematically investigated expressions of ERGIC3 in a broad variety of normal human tissues and various types of tumors by immunohistochemistry. In normal human tissues, 6‐C4 reacted only in some epithelial cells, such as hepatocytes, gastrointestinal epithelium, ducts and acini of the pancreas, proximal and distal tubules of the kidney, and mammary epithelial cells; however, most normal human tissues were not stained. Moreover, almost all carcinomas that originated from the epithelial cells were positive for 6‐C4, whereas all sarcomas were negative. Notably, 6‐C4 strongly stained non‐small cell lung cancer (NSCLC) cells but did not react with normal lung tissues. Hence, ERGIC3 mAb could be used in histopathological diagnosis and cytopathological testing to detect early‐stage NSCLC. We also studied the mechanisms of ERGIC3 regulation in vitro and in vivo by means of bioinformatics analysis, luciferase reporter assay, miRNA expression profiling and miRNA transfection. Results showed that miR‐203a downregulation induced ERGIC3 overexpression in NSCLC cells.     

A MDM2‐dependent positive‐feedback loop is involved in inhibition of miR‐375 and miR‐106b induced by Helicobacter pylori lipopolysaccharide

Dysregulation of microRNAs (miRNAs) has been linked to virulence factors of Helicobacter pylori and shown to contribute to the progression of gastric cancer. However, the mechanisms of these processes remain poorly understood. The aim of this study was to investigate the mechanisms by which lipopolysaccharide (LPS), a virulence factor of H. pylori, regulates miR‐375 and miR‐106b expression in gastric epithelial cells. The results show that LPS from H. pylori 26695 downregulated the expression of miR‐375 and miR‐106b in gastric epithelial cells, and low levels of Dicer were also observed. Downregulation of miR‐375 was found to increase expression of MDM2 with SP1 activation. Overexpression of MDM2 inhibited Dicer by repressing p63 to create a positive‐feedback loop involving SP1/MDM2/p63/Dicer that leads to inhibition of miR‐375 and miR‐106b expression. In addition, we demonstrated that JAK1 and STAT3 were downstream target genes of miR‐106b. H. pylori LPS also enhanced the tyrosine phosphorylation of JAK1, JAK2 and STAT3. Together, these results provide insight into the regulatory mechanisms of MDM2 on H. pylori LPS‐induced specific miRNAs, and furthermore, suggest that gastric epithelial cells treated with H. pylori LPS may be susceptible to JAK/STAT3 signal pathway activation via inhibition of miR‐375 and miR‐106b.     

N‐glycosylation status of β‐haptoglobin in sera of patients with colon cancer,chronic inflammatory diseases and normal subjects

N‐glycosylation status of purified β‐haptoglobin from sera of 17 patients, and from sera of 14 healthy volunteer subjects, was compared by blotting with various lectins and antibodies. Patients in this study were diagnosed as having colon cancer through histological examination of each tumor tissue by biopsy. Blotting index of serum β‐haptoglobin with Aleuria aurantia lectin (AAL) was clearly higher for cancer patients than for healthy subjects. No such distinction was observed for blotting with three other lectins and two monoclonal antibodies. To determine tumor‐associated reactivity of AAL binding as compared to inflammatory processes in colonic tissues, β‐haptoglobin separated from sera of 5 patients with Crohn's disease (CD), and 4 patients with ulcerative colitis (UC), was studied. All these cases, except one case of UC, showed AAL index lower than that in cancer cases, similarly to healthy subjects. The higher AAL binding of β‐haptoglobin in colon cancer patients than in healthy subjects appeared to be due to α‐L‐fucosyl residue, since it was eliminated by bovine kidney α‐fucosidase treatment. N‐linked glycans of serum haptoglobin from colon cancer patients vs. healthy subjects were released by N‐glycanase, fluorescence‐labeled, and subjected to normal‐phase high performance liquid chromatography (NP‐HPLC). Glycan structures were determined based on glucose unit (GU) values and their changes upon sequential treatment with various exoglycosidases. Glycosyl sequences and their branching status of glycans from 14 cases of serum β‐haptoglobin were characterized. The identified glycans were sialylated or nonsialylated, bi‐antennary or tri‐antennary structures, with or without terminal fucosylation.     

Hsp27 regulates EGF/β‐catenin mediated epithelial to mesenchymal transition in prostate cancer

Increased expression of the molecular chaperone Hsp27 is associated with the progression of prostate cancer (PCa) to castration‐resistant disease, which is lethal due to metastatic spread of the prostate tumor. Metastasis requires epithelial to mesenchymal transition (EMT), which endows cancer cells with the ability to disseminate from the primary tumor and colonize new tissue sites. A wide variety of secreted factors promote EMT, and while overexpression and constitutive activation of epidermal growth factor (EGF) signaling is associated with poor prognosis of PCa, a precise role of EGF in PCa progression to metastasis remains unclear. Here, we show that Hsp27 is required for EGF‐induced cell migration, invasion and MMPs activity as well as the expression of EMT markers including Fibronectin, Vimentin and Slug with concomitant decrease of E‐cadherin. Mechanistically, we found that Hsp27 is required for EGF‐induced AKT and GSK3β phosphorylation and β‐catenin nuclear translocation. Moreover, silencing Hsp27 decreases EGF dependent phosphorylation of β‐catenin on tyrosine 142 and 654, enhances β‐catenin ubiquitination and degradation, prevents β‐catenin nuclear translocation and binding to the Slug promoter. These data suggest that Hsp27 is required for EGF‐mediated EMT via modulation of the β‐catenin/Slug signaling pathway. Together, our findings underscore the importance of Hsp27 in EGF induced EMT in PCa and highlight the use of Hsp27 knockdown as a useful strategy for patients with advanced disease.     

Downregulation of leucine‐rich repeats and immunoglobulin‐like domains 1 by microRNA‐20a modulates gastric cancer multidrug resistance

Multidrug resistance (MDR) significantly restricts the clinical efficacy of gastric cancer (GC) chemotherapy, and it is critical to search novel targets to predict and overcome MDR. Leucine‐rich repeats and immunoglobulin‐like domains 1 (LRIG1) has been proved to be correlated with drug resistance in several cancers. The present study revealed that LRIG1 was overexpressed in chemosensitive GC tissues and decreased expression of LRIG1 predicted poor survival in GC patients. We observed that upregulation of LRIG1 enhanced chemosensitivity in GC cells. Interestingly, miR‐20a, which was overexpressed in GC MDR cell lines and tissues, was identified to regulate LRIG1 expression by directly targeting its 3′ untranslated region. We also found that inhibition of miR‐20a suppressed GC MDR, and upregulation showed opposite effects. Moreover, we demonstrated that the miR‐20a/LRIG1 axis regulated GC cell MDR through epidermal growth factor receptor (EGFR)‐mediated PI3K/AKT and MAPK/ERK signaling pathways. Finally, LRIG1 expression in human GC tissues is inversely correlated with miR‐20a and EGFR. Taken together, the newly identified miR‐20a/LRIG1/EGFR link provides insight into the MDR process of GC, and targeting this axis represents a novel potential therapeutic strategy to block GC chemoresistance.     

Putative tumor suppressor miR‐145 inhibits colon cancer cell growth by targeting oncogene friend leukemia virus integration 1 gene

BACKGROUND:

Tumor suppressor microRNA miR‐145 is commonly down‐regulated in colon carcinoma tissues, but its specific role in tumors remains unknown.

METHODS:

In this study, the authors identified the Friend leukemia virus integration 1 gene (FLI1) as a novel target of miR‐145. FLI1 is involved in t(11;22)(q24:q12) reciprocal chromosomal translocation in Ewing sarcoma, and its expression appears to be associated with biologically more aggressive tumors.

RESULTS:

The authors demonstrated that miR‐145 targets a putative microRNA regulatory element in the 3′‐untranslated region (UTR) of FLI1, and its abundance is reversely associated with FLI1 expression in colon cancer tissues and cell lines. By using a luciferase/FLI1 3′‐UTR reporter system, they found that miR‐145 down‐regulated the reporter activity, and this down‐regulation was reversed by anti–miR‐145. Mutation of the miR‐145 microRNA regulatory element sequence in the FLI1 3′‐UTR abolished the activity of miR‐145. miR‐145 decreased FLI1 protein but not FLI1 mRNA, suggesting a mechanism of translational regulation. Furthermore, the authors demonstrated that miR‐145 inhibited cell proliferation and sensitized LS174T cells to 5‐fluorouracil–induced apoptosis.

CONCLUSIONS:

Taken together, these results suggest that miR‐145 functions as a tumor suppressor by down‐regulating oncogenic FLI1 in colon cancer. Cancer 2011. © 2010 American Cancer Society.     

Curcumin β‐D‐glucuronide exhibits anti–tumor effects on oxaliplatin‐resistant colon cancer with less toxicity in vivo

The NF‐kappa B (NF‐κB) pathway plays a pivotal role in tumor progression and chemoresistance, and its inhibition has been shown to suppress tumor growth in a variety of preclinical models. Recently, we succeeded in synthesizing a water‐soluble injectable type of curcumin β‐D‐glucuronide (CMG), which is converted into a free‐form of curcumin by β‐glucuronidase in vivo. Herein, we aimed to clarify the efficacy, safety and pharmacokinetics of CMG in a xenograft mouse model. First, we confirmed that the presence of KRAS/TP53 mutations significantly increased the IC₅₀ of oxaliplatin (L‐OHP) and NF‐κB activity in HCT116 cells in vitro. Then, we tested the efficacy of CMG in an HCT116 colon cancer xenograft mice model. CMG demonstrated superior anticancer effects compared to L‐OHP in an L‐OHP‐resistant xenograft model. With regard to safety, significant bodyweight loss, severe myelosuppression and AST/ALT elevation were observed in L‐OHP‐treated mice, whereas none of these toxicity was noted in CMG‐treated mice. The combination of CMG and L‐OHP exhibited additive effects in these xenograft models without increasing toxicity. Pharmacokinetic analysis revealed that high levels of free‐form curcumin were maintained in the tumor tissue after 48 hours following CMG administration, but it was not detected in other major organs, such as the heart, liver and spleen. Immunohistochemistry revealed reduced NF‐κB activity in the tumor tissue extracted from CMG‐treated mice compared with that from control mice. These results indicated that CMG could be a promising anticancer prodrug for treating colon cancer with minimal toxicity.