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Background and Aim: Although rectal neuroendocrine tumor (NET-G1) have potential metastatic capability, even among small tumors, no predictive biomarker for invasion and metastasis has been reported. We analyzed microRNA (miRNA) expression profiles in rectal NET-G1 tissues with and without lymphovascular invasion (LVI). Moreover, we then investigated their target genes to clarify the mechanism of invasion/metastasis in NET-G1. Methods: miRNA array analysis was performed using 7 rectal NET-G1 tissues with LVI and 7 without LVI. miRNA expression was confirmed by quantitative real-time PCR. A NET cell line H727 was transfected with miRNA mimic or target gene small interfering RNA, and migration and invasion assays were performed. Results: The expression levels of miR-144-3p and miR-451a were significantly higher in NET-G1 with LVI versus without LVI, as determined by miRNA array analysis and RT-qPCR. A significant correlation was observed between miR-144-3p and miR-451a expression levels, strongly suggesting miR144/451 cluster overexpression in NET-G1 with LVI. Bioinformatic analysis of target genes revealed that miR-144-3p and miR-451a directly interact with PTEN and p19 mRNA, respectively. Immunohistochemistry revealed significantly lower expression of PTEN and p19 in NET-G1 tissues with LVI than in those without LVI. The miR-144-3p and miR-451a mimic significantly increased cell migration/invasion capability, respectively. Knockdown of PTEN and p19 induced significant augmentation of cell invasion and migration capability, respectively. Conclusions: Our data suggest that overexpression of miR-144/miR-451 cluster promotes LVI via repression of PTEN and p19 in rectal NET-G1 cells. miR-144/451 cluster may be a novel biomarker for predicting invasion/metastasis in rectal NET-G1.

Background/Aims: Sessile serrated adenomas/polyps (SSA/Ps) are a putative precursor lesion of colon cancer. Although the relevance of DNA hypermethylation in the SSA/P-cancer sequence is well documented, the role of DNA hypomethylation is unknown. We investigated the biological relevance of DNA hypomethylation in the SSA/P-cancer sequence by using 3-dimensional organoids of SSA/P. Methods: We first analyzed hypomethylated genes using datasets from our previous DNA methylation array analysis on 7 SSA/P and 2 cancer in SSA/P specimens. Expression levels of hypomethylated genes in SSA/P specimens were determined by RT-PCR and immunohistochemistry. We established 3-dimensional SSA/P organoids and performed knockdown experiments using a lentiviral shRNA vector. DNA hypomethylation at CpG sites of the gene was quantitated by MassARRAY analysis. Results: The mean number of hypomethylated genes in SSA/P and cancer in SSA/P was 41.6 ± 27.5 and 214 ± 19.8, respectively, showing a stepwise increment in hypomethylation during the SSA/P-cancer sequence. S100P, S100α2, PKP3, and MUC2 were most commonly hypomethylated in SSA/P specimens. The mRNA and protein expression levels of S100P, S100α2, and MUC2 were significantly elevated in SSA/P compared with normal colon tissues, as revealed by RT-PCR and immunohistochemistry, respectively. Among these, mRNA and protein levels were highest for S100P. Knockdown of the S100P gene using a lentiviral shRNA vector in 3-dimensional SSA/P organoids inhibited cell growth by >50% (p < 0.01). The mean diameter of SSA/P organoids with S100P gene knockdown was significantly smaller compared with control organoids. MassARRAY analysis of DNA hypomethylation in the S100P gene revealed significant hypomethylation at specific CpG sites in intron 1, exon 1, and the 5′-flanking promoter region. Conclusion: These results suggest that DNA hypomethylation, including S100P hypomethylation, is supposedly associated with the SSA/P-cancer sequence. S100P overexpression via DNA hypomethylation plays an important role in promoting cell growth in the SSA/P-cancer sequence.

Background/Aims: Pancreatic ductal adenocarcinoma (PDAC) is characterized by aggressive invasion, early metastasis, and resistance to chemotherapy, leading to a poor prognosis. To clarify the molecular mechanism of these malignant characteristics, we performed a genome-wide microRNA (miRNA) array analysis utilizing micro-cancer tissues from patients with unresectable PDAC (stage IV), obtained by endoscopic ultrasound-fine needle aspiration (EUS-FNA). Methods: The expression profiles of 2,042 miRNAs were determined using micro-cancer tissues from 13 patients with unresectable PDAC obtained by EUS-FNA. The relationship between individual miRNA levels and overall survival (OS) was analyzed. Possible target genes for miRNAs were bioinformatically analyzed using the online database miRDB. Pancreatic cancer cell lines PANC-1, MIA PaCa-2, and PK-8 were transfected with miRNA mimic or small interfering RNA, and cell invasion, epithelial-mesenchymal transition (EMT), and apoptosis markers were examined. miRNA and mRNA expressions were examined by quantitative polymerase chain reaction. Results: Of 2,042 miRNAs, the 10 that exhibited the lowest correlation coefficient (p ≤ 0.005) between miRNA expression level and OS among the patients were identified. The miRDB and expression analysis in cancer cell lines for the 10 miRNAs identified miR-296-5p and miR-1207-5p as biomarkers predictive of shorter survival (p < 0.0005). Bioinformative target gene analysis and transfection experiments with miRNA mimics showed that Bcl2-related ovarian killer (BOK), a pro-apoptotic gene, is a target for miR296-5p in pancreatic cancer cells; transfection of miR-296-5p mimic into PANC-1, MIA PaCa-2, and PK-8 cells resulted in significant suppression of BOK mRNA and protein expression. These transfectants showed significantly higher invasion capability compared with control cells, and knock down of BOK in pancreatic cancer cells similarly enhanced invasion capability. Transfectants of miR-296-5p mimic also exhibited aberrant expression of EMT markers, including vimentin and N-cadherin. Moreover, these transfectants showed a significantly lower apoptosis rate in response to 5-fluorouracil and gemcitabine with a decrease of BOK expression, suggesting a role of miR-296-5p in drug resistance. Conclusion: These results suggest that miR-296-5p is a useful biomarker for a poor prognosis in patients with PDAC, and that the miR-296-5p/BOK signaling axis plays an important role in cell invasion, drug resistance, and EMT in PDACs.

To overcome the problem of overlooking colorectal tumors, a new and highly sensitive modality of colonoscopy is needed. Moreover, it is also important to establish a new modality to evaluate viable tumor volume in primary lesions of colorectal cancer (CRC) during chemotherapy. Therefore, we carried out molecular imaging of colorectal tumors targeting epidermal growth factor receptor (EGFR), which is highly expressed on tumor cells, for evaluating chemotherapeutic efficacy and for endoscopic detection of colorectal adenomas. We first attempted to image five CRC cell lines with various levels of EGFR expression using an Alexa Fluor‐labeled anti‐EGFR monoclonal antibody (AF‐EGFR‐Ab). A strong fluorescence signal was observed in the cells depending on the level of EGFR expression. When nude mice xenografted with LIM1215 CRC cells, which highly express EGFR, were i.v. injected with AF‐EGFR‐Ab, a strong fluorescence signal appeared in the tumor with a high signal to noise ratio, peaking at 48 hours after injection and then gradually decreasing, as shown using an IVIS Spectrum system. When the xenografted mice were treated with 5‐fluorouracil, fluorescence intensity in the tumor decreased in proportion to the viable tumor cell volume. Moreover, when the colorectum of azoxymethane‐treated rats was observed using a thin fluorescent endoscope with AF‐EGFR‐Ab, all 10 small colorectal adenomas (≤3 mm) were detected with a clear fluorescence signal. These preliminary results of animal experiments suggest that EGFR‐targeted fluorescent molecular imaging may be useful for quantitatively evaluating cell viability in CRC during chemotherapy, and also for detecting small adenomas using a fluorescent endoscope.

ABC, antibody-binding capacity; ADCC, antibody-dependent cellular cytotoxicity; ATCC, American Type Culture Collection; BSA, bovine serum albumin; CR, complete response; CRC, colorectal cancer; CT, computed tomography; ECACC, European Collection of Authenticated Cell Cultures; EGF, epidermal growth factor; EGFR, epidermal growth factor receptor; ETS, early tumor shrinkage; FBS, fetal bovine serum; FISH, fluorescent in situ hybridization; HRP, horseradish peroxidase; HSRRB, Health Science Research Resources Bank; IHC, immunohistochemistry; MesNa, Mercaptoethanesulfonic acid sodium; mCRC, metastatic colorectal cancer; mAb, monoclonal antibody; mAbs, monoclonal antibodies; PARP, poly (ADP-ribose) polymerase; PBS, phosphate buffered saline; PD, progressive disease; p-ERK, phosphorylated ERK; PNA-LNA, peptide nucleic acid-locked nucleic acid; PR, partial response; PVDF, polyvinylidene difluoride; RECIST, Response Evaluation Criteria in Solid Tumors; RIKEN BRC, RIKEN BioResource Center; SD, stable disease; SDS, sodium dodecyl sulfate; SDS-PAGE, SDS-polyamide gel electrophoresis; TBS-T, Tris-buffered saline with 0.1% Tween; TGF-α, transforming growth factor-α.

Objectives: The aim of this study was to identify biomarkers for predicting the efficacy of docetaxel, cisplatin, and S-1 (DCS) therapy for advanced gastric cancer using microarrays of biopsy specimens before chemotherapy. Methods: Nineteen samples were taken from 19 patients with unresectable metastatic gastric cancer who received DCS as a first-line therapy. Laser capture microdissection was performed, and total cellular RNA was extracted from each microdissected sample. Whole-gene expression was analyzed by microarray, and the difference in mRNA expression observed with the microarrays was confirmed by quantitative real-time PCR. Immunohistochemical staining was performed using clinical tissue sections obtained by endoscopic biopsy. Results: Eleven patients were identified as early responders and 8 patients as nonresponders to DCS therapy. Twenty-nine genes showed significant differences in relative expression ratios between tumor and normal tissues. A classifier set of 29 genes had high accuracy (94.7%) for distinguishing gene expression between 11 early responders and 8 nonresponders. Decreasing the size of the classifier set to 4 genes (PDGFB, PCGF3, CISH, and ANXA5) increased the accuracy to 100%. Expression levels by real-time PCR for validation were well correlated with those 4 genes in microarrays. Conclusion: The genes identified may serve as efficient biomarkers for personalized cancer-targeted therapy.

The antitumor activity of pladienolide B, a novel splicing inhibitor, against gastric cancer is totally unknown and no predictive biomarker of pladienolide B efficacy has been reported. We investigated the antitumor activity of pladienolide B and its derivative on gastric cancer cell lines and primary cultured cancer cells from carcinomatous ascites of gastric cancer patients. The effect of pladienolide B and its derivative on six gastric cancer cell lines was investigated using a MTT assay and the mean IC50 values determined to be 1.6 ± 1.2 (range, 0.6–4.0) and 1.2 ± 1.1 (range, 0.4–3.4) nM, respectively, suggesting strong antitumor activity against gastric cancer. The mean IC50 value of pladienolide B derivative against primary cultured cells from 12 gastric cancer patients was 4.9 ± 4.7 nM, indicative of high antitumor activity. When 18 SCID mice xenografted with primary cultured cells from three patients were administered the pladienolide B derivative intraperitoneally, all tumors completely disappeared within 2 weeks after treatment. Histological examination revealed a pathological complete response for all tumors. In the xenograft tumors after treatment with pladienolide B derivative, immature mRNA were detected and apoptotic cells were observed. When the expressions of cell-cycle proteins p16 and cyclin E in biopsied gastric cancer specimens were examined using immunohisctochemistry, positivities for p16 and cyclin E were significantly and marginally higher, respectively, in the low-IC50 group compared with the high-IC50 group, suggesting the possibility that they might be useful as predictive biomarkers for pladienolide B. In conclusion, pladienolide B was very active against gastric cancer via a mechanism involving splicing impairment and apoptosis induction.