Takehiko Yokobori

Epithelial–mesenchymal transition in cancer development and its clinical significance

The epithelial–mesenchymal transition (EMT) plays a critical role in embryonic development. EMT is also involved in cancer progression and metastasis and it is probable that a common molecular mechanism is shared by these processes. Cancer cells undergoing EMT can acquire invasive properties and enter the surrounding stroma, resulting in the creation of a favorable microenvironment for cancer progression and metastasis. Furthermore, the acquisition of EMT features has been associated with chemoresistance which could give rise to recurrence and metastasis after standard chemotherapeutic treatment. Thus, EMT could be closely involved in carcinogenesis, invasion, metastasis, recurrence, and chemoresistance. Research into EMT and its role in cancer pathogenesis has progressed rapidly and it is now hypothesized that novel concepts such as cancer stem cells and microRNA could be involved in EMT. However, the involvement of EMT varies greatly among cancer types, and much remains to be learned. In this review, we present recent findings regarding the involvement of EMT in cancer progression and metastasis and provide a perspective from clinical and translational viewpoints. (Cancer Sci 2009)

MicroRNA-125a-5p Is an Independent Prognostic Factor in Gastric Cancer and Inhibits the Proliferation of Human Gastric Cancer Cells in Combination with Trastuzumab

Purpose: MicroRNA 125a-5p (miR-125a-5p) has been reported to be a tumor suppressor in malignancies of the breast, ovary, lung, and central nervous system. However, the clinical significance of miR-125a-5p in human gastrointestinal cancer has not been explored. We investigated a tumor inhibitory effect of miR-125a-5p in gastric cancer, focusing in particular on the miR-125a-ERBB2 (HER2, HER-2/neu) pathway. Experimental Design: Quantitative RT-PCR was used to evaluate miR-125a-5p expression in 87 gastric cancer cases to determine the clinicopathologic significance of miR-125a-5p expression. The regulation of ERBB2 by miR-125a-5p was examined with precursor miR-125a–transfected cells. Furthermore, we investigated whether miR-125a-5p suppresses proliferation of gastric cancer cells in combination with trastuzumab, a monoclonal antibody against ERBB2. Results: Low expression levels of miR-125a-5p were associated with enhanced malignant potential such as tumor size (P = 0.0068), tumor invasion (P = 0.031), liver metastasis (P = 0.029), and poor prognosis (P = 0.0069). Multivariate analysis indicated that low miR-125a-5p expression was an independent prognostic factor for survival. In vitro assays showed that ERBB2 is a direct target of miR-125a-5p, which potently suppressed the proliferation of gastric cancer cells, and, interestingly, the growth inhibitory effect was enhanced in combination with trastuzumab. Conclusions:miR-125a-5p is a meaningful prognostic marker. Furthermore, miR-125a-5p mimic alone or in combination with trastuzumab could be a novel therapeutic approach against gastric cancer. Clin Cancer Res; 17(9); 2725–33. ©2011 AACR.

Plastin3 Is a Novel Marker for Circulating Tumor Cells Undergoing the Epithelial–Mesenchymal Transition and Is Associated with Colorectal Cancer Prognosis

Circulating tumor cells (CTC) in blood have attracted attention both as potential seeds for metastasis and as biomarkers. However, most CTC detection systems might miss epithelial-mesenchymal transition (EMT)-induced metastatic cells because detection is based on epithelial markers. First, to discover novel markers capable of detecting CTCs in which EMT has not been repressed, microarray analysis of 132 colorectal cancers (CRC) from Japanese patients was conducted, and 2,969 genes were detected that were overexpressed relative to normal colon mucosa. From the detected genes, we selected those that were overexpressed CRC with distant metastasis. Then, we analyzed the CRC metastasis-specific genes (n = 22) to determine whether they were expressed in normal circulation. As a result, PLS3 was discovered as a CTC marker that was expressed in metastatic CRC cells but not in normal circulation. Using fluorescent immunocytochemistry, we validated that PLS3 was expressed in EMT-induced CTC in peripheral blood from patients with CRC with distant metastasis. PLS3-expressing cells were detected in the peripheral blood of approximately one-third of an independent set of 711 Japanese patients with CRC. Multivariate analysis showed that PLS3-positive CTC was independently associated with prognosis in the training set (n = 381) and the validation set [n = 330; HR = 2.17; 95% confidence interval (CI) = 1.38-3.40 and HR = 3.92; 95% CI = 2.27-6.85]. The association between PLS3-positive CTC and prognosis was particularly strong in patients with Dukes B (HR = 4.07; 95% CI = 1.50-11.57) and Dukes C (HR = 2.57; 95% CI = 1.42-4.63). PLS3 is a novel marker for metastatic CRC cells, and it possesses significant prognostic value.

p53-Altered FBXW7 Expression Determines Poor Prognosis in Gastric Cancer Cases

A molecular target associated with the progression of gastric cancer has not yet been uncovered. FBXW7 is a tumor suppressor gene transcriptionally controlled by p53 that plays a role in the regulation of cell cycle exit and reentry via c-Myc degradation. Few studies have addressed the clinical significance of FBXW7 expression in gastric cancer. Therefore, we examined FBXW7 mRNA expression to determine its clinicopathologic significance in 100 cases of gastric cancer. Low expression levels of FBXW7 in primary gastric cancer contributed to malignant potential, such as lymph node metastasis (P = 0.0012), tumor size (P = 0.0003), and poor prognosis (P = 0.018). In comparison with 52 cases of gastric cancer without the p53 mutation, 29 cases with the mutation exhibited lower expression levels of FBXW7 (P = 0.0034), revealing a significant relationship between p53 mutation and FBXW7 expression. Furthermore, we found that gastric cancer patients who had low FBXW7 expression levels and p53 mutation had a distinctively poor prognosis in comparison with other subgroups (P = 0.0033). In conclusion, we showed a role for p53 in the transcriptional regulation of FBXW7 expression in clinical gastric cancer cases and showed that disruption of both p53 and FBXW7 contributes to poor prognosis.

MiR‐150 is associated with poor prognosis in esophageal squamous cell carcinoma via targeting the EMT inducer ZEB1

The association of microRNAs (miRs) with cancer progression has been established in many cancers including esophageal squamous cell carcinoma (ESCC). A public microarray database showed that the expression of miR‐150 was lower in ESCC than in normal esophageal mucosa. Here, we focused on ZEB1, epithelial‐mesenchymal‐transition (EMT)‐inducer, as a target gene of miR‐150 based on in silico predictions. The purpose of this study was to clarify the clinicopathological significance of miR‐150 in ESCC, and to investigate miR‐150′s EMT‐regulatory ability. Quantitative RT‐PCR was used to evaluate miR‐150 expression in 108 curative resected ESCC samples to determine the clinicopathological significance. Moreover, we examined the in vitro and in vivo function of miR‐150 via degradation of ZEB1. MiR‐150 expression was significantly lower in cancer tissues compared to adjacent non‐cancerous tissues (P < 0.001). Low expression of miR‐150 in ESCC contributed to malignant potential, such as tumor depth, lymph node metastasis, lymphatic invasion, venous invasion, clinical staging, and poor prognosis (P < 0.05). In vitro assays showed that EMT‐inducer‐ZEB1 is a new direct target of miR‐150. Moreover, miR‐150 induced MET‐like changes in TE‐8 cells through ZEB1 degradation (e.g., E‐cadherin expression, vimentin repression, epithelial morphology, and suppression of migration ability), and significantly inhibited tumorigenicity and tumor growth in a mouse xenograft model. Analysis of the regulation of ZEB1 by miR‐150 could provide new insights into preventing metastasis and also suggests novel targeted therapeutic strategies in ESCC. (Cancer Sci 2013; 104: 48–54)

Loss of FBXW7, a cell cycle regulating gene, in colorectal cancer: Clinical significance

This study focused on a cell cycle regulatory gene, FBXW7, which ubiquitinates c‐Myc and cyclin E and promotes exit from the cell cycle. We determined the expression level of FBXW7 in colorectal cancer (CRC) cases, correlated those values with clinicopathologic features, and characterized the molecular mechanism of reduced expression of FBXW7 in CRC cells in vitro. FBXW7 mRNA and protein expression were evaluated in 93 CRC cases. Using CGH array, the copy number aberrations of the flanking region of FBXW7 were evaluated in another 130 CRC specimens. In vitro analysis of FBXW7 gene silencing in CRC cells was conducted. FBXW7 mRNA expression was significantly lower in tumor tissues than the corresponding normal tissues. The low FBXW7 expression group showed a significantly poorer prognosis than patients in the high expression group. A concordant relationship was observed between the incidence of FBXW7 repression and the genetic alteration. The incidence of genetic alteration was associated with the stage of disease progression. In vitro, FBXW7‐specific siRNA enhanced expression of c‐MYC and cyclin E proteins and up‐regulated cell proliferation. Genetic alterations in tumors led to the loss of FBXW7 expression and increased cell proliferation. FBXW7 expression provides a prognostic factor for patients with CRC.

MicroRNA miR-125b is a prognostic marker in human colorectal cancer

MicroRNAs (miRNAs) are small, non-coding RNAs that can function as oncogenes or tumor suppressors in human cancer. Recent reports have highlighted the oncogenic aspects of microRNA miR-125b. However, the clinical significance of miR-125b in gastrointestinal cancers has not been sufficiently investigated. To this end, we analyzed miR-125b expression in colorectal cancer cases. Quantitative RT-PCR was used to evaluate miR-125b expression in 89 colorectal cancer cases to determine the clinicopathological significance of miR-125b expression. The high miR-125b expression group showed a greater incidence of advanced tumor size and tumor invasion compared to the low miR-125b expression group (P<0.05). In addition, the high miR-125b expression group had a significantly poorer prognosis compared to the low expression group (P<0.05). Multivariate analysis indicated that high miR-125b expression was an independent prognostic factor for survival. Our analysis of miR-125b focused on the miR-125b/p53 pathway. In vitro assays revealed that overexpression of miR-125b repressed the endogenous level of p53 protein in human colorectal cancer cells. These data show that miR-125b is directly involved in cancer progression and is associated with poor prognosis in human colorectal cancer. Our findings suggest that miR-125b could be an important prognostic indicator for colorectal cancer patients.

MicroRNA-7 expression in colorectal cancer is associated with poor prognosis and regulates cetuximab sensitivity via EGFR regulation

MicroRNA-7 (miR-7) has been reported to be a tumor suppressor in all malignancies including colorectal cancer (CRC). However, its significance for CRC clinical outcomes has not yet been explored. The potential for miR-7 to act as a tumor suppressor by coordinately regulating the epidermal growth factor receptor (EGFR) signaling pathway at several levels was examined. We investigated the tumor inhibitory effect of miR-7 in CRC, with particular focus on the relationship between miR-7 and the EGFR pathway. Quantitative reverse transcription-PCR was used to evaluate miR-7 expression in 105 CRC cases to determine the clinicopathologic significance of this miRNA. The regulation of EGFR by miR-7 was examined with miR-7 precursor-transfected cells. Furthermore, we investigated whether miR-7 suppresses proliferation of CRC cells in combination with cetuximab, a monoclonal antibody against EGFR. Multivariate analysis indicated that low miR-7 expression was an independent prognostic factor for poor survival (P = 0.0430). In vitro assays showed that EGFR and RAF-1 are direct targets of miR-7, which potently suppressed the proliferation of CRC cells, and, interestingly, that the growth inhibitory effect of each of these was enhanced by cetuximab. miR-7 is a meaningful prognostic marker. Furthermore, these data indicate that miR-7 precursor, alone or in combination with cetuximab, may be useful in therapy against CRC.

A large-scale study of MT1-MMP as a marker for isolated tumor cells in peripheral blood and bone marrow in gastric cancer cases.

BackgroundRecently, a marker for predicting metastasis or recurrence precisely in solid cancers has been focused on instead of the identification of isolated tumor cells detected by epithelial genes in circulating system. We identified a candidate marker in gastric cancer by microarray and validated it through a quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR) assay.MethodsTo identify metastasis-related genes, we performed cDNA microarray analysis of total RNA from whole bone marrow blood from six cases with metastasis and three cases without metastasis. We determined clinical significance of the identified gene by microarray analysis with quantitative real-time RT-PCR in bone marrow and peripheral blood from 810 cases of gastric cancer.ResultsWe focused on membrane type 1 matrix metalloproteinase (MT1-MMP) as a candidate marker to predict distant metastasis among identified genes. MT1-MMP-positive expression in peripheral blood was associated with incidence of peritoneal dissemination, lymphatic permeation, vascular permeation, and lymph node metastasis. MT1-MMP-positive expression in bone marrow was also significantly related to the incidence of distant metastasis and peritoneal dissemination.ConclusionThe expression of MT1-MMP in peripheral blood from gastric cancer cases was a powerful indicator of distant metastasis especially for peritoneal dissemination. The presence of MT1-MMP-expressing cells in bone marrow indicated higher risk for distant metastasis in gastric cancer cases.

Identification of recurrence-related microRNAs in the bone marrow of breast cancer patients

Recently, bone marrow has been considered as playing a critical role in the generation of both metastasis and recurrent disease. The accumulation of a single microRNA in the bone marrow has the potential to regulate the translation of multiple genes in cancer metastasis and may therefore serve as a prognostic marker for cancer recurrence. MicroRNA microarray analysis was performed to compare microRNA levels in bone marrow from 4 breast cancer patients with recurrent disease and 4 patients without recurrence. Accumulation of two of these microRNAs, miR-21 and miR-181a, in the recurrent breast cancer cases was validated by RT-PCR in bone marrow from 291 additional breast cancer cases. Expression of a common target gene, PDCD4, was also determined in bone marrow from 291 breast cancer cases. Increased miR-21 and miR-181a levels were significantly associated with shortened disease-free survival (DFS; p=0.0003, 0.0007) and overall survival (OS; p=0.0351, 0.0443), respectively. While low PDCD4 expression was also significantly associated with poorer DFS (p=0.036). Multivariate analysis identified bone marrow miR-21 and mR-181a levels as valuable independent prognostic factors, with correlation coefficients that were significantly higher than that of the transcript of their common target gene. Accumulation of miR-21 and miR-181a in bone marrow appears to be associated with prognosis in breast cancer patients. The much higher significant correlation with microRNA levels and prognosis suggests epistatic effects on multiple target genes in the bone marrow of breast cancer patients.