Background:This study aims to explore novel microRNAs in plasma for screening cancer and predicting clinical outcomes in pancreatic cancer (PCa) patients using a microRNA array-based approach.Methods:We used the Toray 3D-Gene microRNA array-based approach to compare plasma levels between PCa patients and healthy volunteers.Results:(1) Six oncogenic microRNAs (miR-615-5p, -744, -575, -557, -675, and -550a) with high expression in plasma were selected. (2) By quantitative RT–PCR using plasma samples from 94 PCa patients and 68 healthy volunteers, a significantly higher level of plasma miR-744 in PCa patients than in healthy volunteers was validated in small-scale analysis (P=0.0038), two independent cohort analyses, and large-scale analysis (P<0.0001, AUC 0.8307). (3) miR-744 expression was significantly higher in PCa tissues (P=0.0069) and PCa cell lines (P=0.0074) than in normal tissues and fibroblasts, respectively. Preoperative plasma level of miR-744 was significantly reduced in postoperative samples (P=0.0063). (4) A high level of plasma miR-744, which was correlated with lymph node metastasis (P=0.0407) and recurrences (P=0.0376), was an independent poor prognostic factor of PCa patients after pancreatectomy (P=0.0007, HR 21.2 (3.17–436)). Furthermore, a high level of plasma miR-744 contributed to poorer progression-free survival of non-operable PCa patients who underwent gemcitabine-based chemotherapy (P=0.0533). Overexpression of miR-744 in PCa cells induced significant chemoresistance to gemcitabine in vitro.Conclusions:Plasma miR-744 might be useful biomarker for screening PCa, monitoring, and predicting poor prognosis and chemoresistance in PCa patients.

Hepatocellular carcinoma (HCC), with its high incidence and mortality rate, is one of the most common malignant tumors. Despite recent development of a diagnostic and treatment method, the prognosis of HCC remains poor. Therefore, to provide optimal treatment for each patient with HCC, more precise and effective biomarkers are urgently needed which could facilitate a more detailed individualized decision-making during HCC treatment, including the following; risk assessment, early cancer detection, prediction of treatment or prognostic outcome. In the blood of cancer patients, accumulating evidence about circulating tumor cells and cell-free nucleic acids has suggested their potent clinical utilities as novel biomarker. This concept, so-called “liquid biopsy” is widely known as an alternative approach to cancer tissue biopsy. This method might facilitate a more sensitive diagnosis and better decision-making by obtaining genetic and epigenetic aberrations that are closely associated with cancer initiation and progression. In this article, we review recent developments based on the available literature on both circulating tumor cells and cell-free nucleic acids in cancer patients, especially focusing on Hepatocellular carcinoma.

Background:PDZ-binding kinase/T-LAK cell-originated protein kinase (PBK/TOPK) is a serine–threonine kinase and overexpressed in various types of cancer by inhibiting the transactivation activities of p53 and PTEN. We tested whether PBK/TOPK acts as a cancer-promoting gene through its activation/overexpression in gastric cancer (GC).Methods:We analysed five GC cell lines and 144 primary tumours, which were curatively resected in our hospital between 2001 and 2003.Results:Overexpression of the PBK/TOPK protein was frequently detected in GC cell lines (4 out of 5 lines, 80.0%) was detected in primary tumour samples of GC (24 out of 144 cases, 16.6%) and was significantly correlated with venous invasion, tumour depth and recurrence rate. PDZ-binding kinase/T-LAK cell-originated protein kinase-overexpressing tumours had a worse survival rate than those with non-expressing tumours (P=0.0009, log-rank test). PDZ-binding kinase/T-LAK cell-originated protein kinase positivity was independently associated with a worse outcome in multivariate analysis (P<0.0001, hazard ratio 6.40 (2.71–14.49)). In PBK/TOPK-overexpressing GC cells, knockdown of PBK/TOPK inhibited the cell proliferation through the p53 activation in a TP53 mutation-dependent manner and inhibited the migration/invasion through the PTEN upregulation in a TP53 mutation-independent manner.Conclusions:These findings suggest PBK/TOPK plays a crucial role in tumour malignant potential through its overexpression and highlight its usefulness as a prognostic factor and potential therapeutic target in GC.

BACKGROUNDThis study aims to explore novel microRNAs in plasma for predicting chemoresistance in preoperative chemotherapy of patients with esophageal squamous cell carcinoma (ESCC) using a microRNA array-based approach.RESULTS(1) Four candidate microRNAs (miR-223, 103a, 23b and 23a), which were highly expressed in the pretreatment plasma of patients with a low histopathologic response, were selected. (2) In a large-scale validation analysis by quantitative RT–PCR, plasma levels of miR-223, miR-23b and miR-23a were significantly higher in patients with a low histopathologic response than in those with a high histopathologic response (p = 0.0345, p = 0.0125 and p = 0.0114). (3) Of all candidate microRNAs, miR-23a expression of pretreatment ESCC tumor tissues was significantly higher in ESCC patients with a low histopathologic response than in those with a high histopathologic response (p = 0.0278). (4) After overexpressing each candidate in ESCC cells, miR-23a induced significant chemoresistance to both 5-fluorouracil and cisplatin, and miR-223 to cisplatin in vitro. (5) A high level of plasma miR-23a, which tended to correlate with lymphatic invasion (p = 0.0808) and deep depth of invasion (p = 0.0658), was an independent risk factor for chemoresistance in ESCC (p = 0.0222; odds ratio: 12.4; range 1.46–105).MATERIALS AND METHODSWe used the Toray® 3D-Gene microRNA array-based approach to compare plasma microRNA levels between patients with a high or a low histopathologic response to chemotherapy. All patients underwent a preoperative chemotherapy regimen with cisplatin plus 5-fluorouracil.CONCLUSIONSPlasma miR-23a might be a useful biomarker for predicting chemoresistance in ESCC patients.

AimsThis study was designed to identify novel microRNAs (miRNAs) in plasma for detecting and monitoring hepatocellular carcinoma (HCC), independent of hepatic function and background liver diseases with different etiologies.Results(1) Four oncogenic miRNAs (miR-151, 155, 191 and 224) with high expression in HCC tissues were selected as candidates. (2) Quantitative RT-PCR using plasma samples from 107 HCC patients and 75 healthy volunteers revealed a significantly higher level of plasma miR-224 in HCC patients than in healthy volunteers according to a small-scale analysis (P < 0.0001), two independent large-scale cohort analysis (P < 0.0001, AUC 0.908). (3) miR-224 expression was significantly higher in HCC tissues and HCC cell lines than in normal hepatic tissues and fibroblasts, respectively. (P = 0.0011, 0.0150) (4) Plasma miR-224 reflected tumor dynamics; preoperative plasma levels of miR-224 were significantly reduced in postoperative samples (P = 0.0058), and plasma miR-224 levels were significantly correlated with paired miR-224 levels in HCC tissues (P = 0.0005). (5) Furthermore, plasma miR-224 levels significantly discriminated HCC patients from patients with chronic liver disease (P = 0.0008). A high plasma miR-224 level was significantly correlated with larger tumor size (P = 0.0005) and recurrences (P = 0.0027). The plasma miR-224 level could accurately detect small tumors less than 18 mm preoperatively.MethodsWe performed a systematic review of the NCBI database and selected candidate miRNAs reported as highly expressed in HCC tissue.ConclusionsPlasma miR-224 may be a sensitive biomarker for screening HCC and monitoring tumor dynamics.

MicroRNAs (miRNAs) are short noncoding RNAs that post-transcriptionally regulate gene expression and play important roles in various physiological and developmental processes such as oncogenic or tumor suppressive regulators. Specific miRNA expression signatures have been identified in a number of human cancers. Cell-free miRNAs have recently been stably detected in plasma and serum (circulating miRNAs), and their presence in blood has attracted the attention of researchers due to their potential as non-invasive biomarkers. Circulating miRNAs have emerged as tumor-associated biomarkers that reflect not only the existence of early-stage tumors, but also the dynamics and status of advanced stage tumors, tumor recurrence, and drug sensitivities. This methodology for liquid biopsy may provide non-invasive and reproductive biomarkers and individualized therapeutic strategies for cancer patients. We herein review the current phase of biological and clinical research on the circulating miRNAs of solid cancers, particularly digestive tract cancers, and discuss future perspectives. The present review may be beneficial for future research on miRNAs used to detect various cancers.

This study explored decreased tumor suppressor microRNA (miRNA) plasma levels in pancreatic cancer (PCa) patients to clarify their potential as novel biomarkers and therapeutic targets. We used the microRNA array-based approach to select candidates by comparing plasma levels between PCa patients and healthy volunteers. Six down-regulated miRNAs (miR-107, miR-126, miR-451, miR-145, miR-491-5p, and miR-146b-5p) were selected. Small- and large-scale analyses using samples from 100 PCa patients and 80 healthy volunteers revealed that miR-107 was the most down-regulated miRNA in PCa patients compared with healthy volunteers (P < 0.0001; area under the receiver-operating characteristic curve, 0.851). A low miR-107 plasma level was significantly associated with advanced T stage, N stage, and liver metastasis and was an independent factor predicting poor prognosis in PCa patients (P = 0.0424; hazard ratio, 2.95). miR-107 overexpression in PCa cells induced G1/S arrest with the production of p21 and inhibited cell proliferation through the transcriptional regulation of Notch2. In vivo, the restoration and maintenance of the miR-107 plasma level significantly inhibited tumor progression in mice. Depletion of the tumor suppressor miR-107 in plasma relates to tumor progression and poor outcomes. The restoration of the plasma miR-107 level might be a novel anticancer treatment strategy for PCa.

Despite recent advances in surgical techniques and perioperative management, the prognosis of pancreatic cancer (PCa) remains extremely poor. To provide optimal treatment for each patient with Pca, superior biomarkers are urgently needed in all phases of management from early detection to staging, treatment monitoring, and prognosis. In the blood of patients with cancer, circulating tumor cells (CTCs) and cell-free nucleic acids (cfNAs), such as DNA, mRNA, and noncoding RNA have been recognized. In the recent years, their presence in the blood has encouraged researchers to investigate their potential use as novel blood biomarkers, and numerous studies have demonstrated their potential clinical utility as a biomarker for certain types of cancer. This concept, called "liquid biopsy" has been focused on as a less invasive, alternative approach to cancer tissue biopsy for obtaining genetic and epigenetic aberrations that contribute to oncogenesis and cancer progression. In this article, we review the available literature on CTCs and cfNAs in patients with cancer, particularly focusing on PCa, and discuss future perspectives in this field.