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EMT and MET comprise the processes by which cells transit between epithelial and mesenchymal states, and they play integral roles in both normal development and cancer metastasis. This article reviews these processes and the molecular pathways that contribute to them. First, we compare embryogenesis and development with cancer metastasis. We then discuss the signaling pathways and the differential expression and down-regulation of receptors in both tumor cells and stromal cells, which play a role in EMT and metastasis. We further delve into the clinical implications of EMT and MET in several types of tumors, and lastly, we discuss the role of epigenetic events that regulate EMT/MET processes. We hypothesize that reversible epigenetic events regulate both EMT and MET, and thus, also regulate the development of different types of metastatic cancers.

Objective To investigate the effects of minimally invasive esophagectomy (MIE) and open esophagectomy (OE) on circulating tumor cell (CTC) level of elderly patients with esophageal cancer (EC). Methods A total of 78 elderly EC patients who aged over 64 years were divided into the MIE group ( n  = 40) and the OE group ( n  = 38). CTC enrichment was performed through CD326 (EpCAM) immunomagnetic beads positive sorting, and then labeled by CK-PE and CD45. The quantity of CTCs was measured by multiparameter flow cytometry. Double antibody sandwich enzyme-linked immuno sorbent assay ELISA (DAS-ELISA) was used for detecting the levels of IL-6, IL-10, and IFN-γ. Results Among the 78 elderly EC patients, CTC level after the surgery was higher than that during the surgery, and CTC level during surgery was higher than that before the surgery (both P  < 0.05). Postoperative CTC level in the MIE group was lower than that in the OE group, and the variation of CTC level from pre-operation to intra-operation in the MIE group was also lower than that in the OE group (both P  < 0.05). Furthermore, there was significant difference in the incidences of intra-operative and postoperative complications between the MIE group and the OE group (17 cases vs. 31 cases, P  < 0.05), and the CTC levels of the patients with complications in either group were significantly higher than the patients without complications (both P  < 0.05). IL-6 and IL-10 levels significantly increased, while IFN-γ level decreased in both groups during the surgery and 3 days after the surgery compared to those before the surgery; 2 weeks after the surgery, IL-6 and IL-10 levels in the MIE group recovered to the pre-operative levels (all P  < 0.05). However, in the OE group, IL-6 and IL-10 levels 2 weeks after the surgery were still significantly higher than those before the surgery (all P  < 0.05); IFN-γ levels in both groups recovered to the pre-operative levels, with higher level in the MIE group than that in the OE group ( P  < 0.05). Conclusion MIE helped to reduce the survival rate of tumor cells in peripheral blood at the early period of postoperation, and dynamic monitoring CTC level could be used to evaluate the prognosis of EC patients.

Background Approximately 20%–45% of colorectal cancer (CRC) patients ultimately develop local recurrence or metastasis following curative surgical resection. The latter is caused by tumor cells shed from the primary carcinoma prior to or during operation, currently undetected by standard clinical staging. Fortunately, the presence of tumor cells in peripheral blood can be detected by molecular methods and is being regarded increasingly as a clinically relevant prognostic factor. Materials and Methods To detect the presence of circulating tumor cells and evaluate their relationship to postoperative metastatic relapse, we simultaneously examined human telomerase reverse transcriptase (hTERT), cytokeratin‐19 (CK‐19), cytokeratin‐20 (CK‐20), and carcinoembryonic antigen (CEA) mRNA (messenger RNA) in the peripheral blood of 72 CRC patients and 30 healthy individuals. Using a reverse‐transcriptase polymerase chain reaction (RT‐PCR), these tumor‐related mRNAs were amplified; in addition, analyses were carried out for their correlation with patients’ clinicopathologic features, as well as the occurrence of postoperative metastasis. Results In RT‐PCR analysis of the peripheral blood, 69.4% (50 out of 72), 66.7% (48 out of 72), 52.8% (38 out of 72), and 72.2% (52 out of 72) of CRC patients were positive for hTERT, CK‐19, CK‐20, and CEA mRNA respectively. All 30 healthy individuals were negative for hTERT and CEA mRNA expression, while 2 were positive for either CK‐19 mRNA or CK‐20 mRNA expression. The detection of CEA mRNA was significantly correlated with depth of tumor invasion (P = 0.012), vessel invasion (P = 0.035), TNM stage (P < 0.0001), and postoperative metastasis (P < 0.0001), while positive hTERT mRNA was correlated with TNM stage (P = 0.037) and CK‐19 was correlated with depth of tumor invasion (P = 0.039) and postoperative metastasis (P = 0.017). In addition, multivariate logistic regression showed that only CEA mRNA was an independent and significant predictor of postoperative metastasis (P = 0.006). Our findings suggest that CEA mRNA may be a more reliable marker than hTERT, CK‐19, and CK‐20 for the detection of circulating cancer cells in the peripheral blood of CRC patients. Conclusions Using RT‐PCR for the detection of CEA mRNA is feasible and may be a promising tool for early detection of micrometastatic circulating tumor cells in CRC patients. CRC patients expressing positive CEA mRNA in peripheral blood have a significantly higher risk of postoperative metastasis. Nevertheless, confirmation of CEA mRNA as a prognostic predictive factor requires the continuation of patient follow‐up.

Early detection of tumor DNA in serum/plasma prior to the development of recurrence or metastases could help improve the outcome of patients with colorectal cancer (CRC) after tumor resection. Recent advances in the detection of tumor DNA in the serum/plasma has opened up numerous new areas for investigation and new possibilities for molecular diagnosis. APC and K‐ras mutations are considered to be early‐stage developments of CRCs, whereas p53 mutations are thought to be relatively late events in the tumorigenesis of CRCs. The aim of this study was to search for the presence of genetic mutations in the DNA extracted from the serum of CRC patients and healthy subjects. We simultaneously evaluate the significance of APC, K‐ras, and p53 gene mutations in cancer tissues and their paired serum samples of 104 CRC patients by polymerase chain reaction‐single strand conformation polymorphism analysis (PCR‐SSCP) followed by direct sequencing. Additionally, analysis was carried out to detect the serum carcinoembryonic antigen (CEA) levels in CRC patients. Overall, we found at least one of the gene mutations in tumor tissues from 75% (78/104) of the CRC patients. Comparison of the three molecular markers showed that the detection rates in the serum were 30.4%, 34.0%, and 34.2% for APC, K‐ras, and p53 genes, respectively. Of these patients, 46.2% (36/78) were identified as having positive serum results, whereas all healthy controls remained negative. The overall positive tumor DNA detection rates in the serum were 0% (0/7) for Dukes’ A classification, 22.4% (11/49) for Dukes’ B, 48.7% (19/39) for Dukes’ C, and 66.7% (6/9) for Dukes’ D. The detection rate increased as the tumor stage progressed (p = 0.012). Concurrently, a significant difference was observed between lymph node metastases and positive serum tumor DNA detection (p < 0.001). A significantly higher postoperative metastasis/recurrence rate in patients harboring gene mutations with serum tumor DNA than those without serum tumor DNA was also demonstrated (p < 0.001). However, no significant correlation between the postoperative metastasis/recurrence and serum CEA levels was observed (p = 0.247). These data suggest that the identification of circulating tumor DNA using the molecular detection of APC, K‐ras, and p53 gene mutations is a potential tool for early detection of postoperative recurrence/metastases. Moreover, these genes may be potential molecular markers of poor clinical outcome in CRC patients.

Technological, methodological, and analytical advances continue to improve the resolution of our view into the cancer genome, even as we discover ways to carry out analyses at greater distances from the primary tumor sites. These advances are finally making the integration of cancer genomic profiling into clinical practice feasible. Formalin fixation and paraffin embedding, which has long been the default pathological biopsy medium, is now being supplemented with liquid biopsy as a means to profile the cancer genomes of patients. At each stage of the genomic data generation process—sample collection, preservation, storage, extraction, library construction, sequencing, and variant calling—there are variables that impact the sensitivity and specificity of the analytical result and the clinical utility of the test. These variables include sample degradation, low yields of nucleic acid, and low variant allele fractions (proportions of assayed molecules carrying variant allele(s)). We review here the most common pre-analytical and analytical factors relating to routine cancer patient genome profiling, some solutions to common challenges, and the major sample preparation and sequencing technology choices available today.

Tumor cell dissemination appears to be an early event in tumor progression, and tumor cells can be detected in peripheral venous blood at the time of the operation. Although cytokeratin 20 (CK‐20) is not specifically expressed by colorectal carcinomas, it represents a widely used marker for the detection of colorectal tumor cells. We used the combination of density centrifugation and CK‐20 real‐time reverse transcription polymerase chain reaction to detect CK‐20‐positive cells in the peripheral venous blood of 37 patients with colorectal carcinoma. Detection rates were compared to serum levels of the tumor markers carcinoembryonic antigen (CEA), carbohydrate antigen CA 19‐9, and cancer antigen CA 125. The prognostic impact was assessed by the overall survival and by univariate and multivariate analysis. Overall, CK‐20‐positive cells in peripheral venous blood were detected in 11 of 37 (29.7%) patients. CK‐20‐positive patients showed a significantly higher mean serum CEA level (90.3 ng/ml) than the 4.1 ng/ml found in the CK‐20‐negative group (p = 0.03). CEA levels also correlated with CK‐20 copy numbers. No significant correlation was observed for CA 19‐9 or CA 125. CK‐20‐negative patients showed a trend toward better survival (p = 0.08). In the univariate analysis, CA 19‐9, CEA, tumor size, lymph node status, grading, the presence of distant metastases, and resection status reached significant prognostic levels, whereas the detection of CK‐20‐positive cells showed only a prognostic trend (p = 0.06). Multivariate analysis failed to identify independent prognostic parameters. Here we report the correlation of CK‐20‐positive cells in peripheral venous blood with the serum CEA level of patients with colorectal cancer, which may represent a potential marker of the tumor load.

Despite widespread use of laparoscopic surgery for colorectal operations, its application for curative resection of colorectal cancer is still controversial. One of the major concerns is the impact of the laparoscopic procedure on dissemination of tumor cells. The main purpose of this study was to investigate the impact of laparoscopic surgery on circulating tumor cells in colorectal cancer patients. Quantitation of circulating free tumor cells (FTCs) was performed preoperatively, during the operation, and 14 days later by means of real‐time quantitative reverse transcriptase‐polymerase chain reaction (RT‐PCR) targeting guanylyl cyclase C (GCC) mRNA in 42 colorectal cancer patients undergoing laparoscopic resections. Despite an increasing trend of FTC detection in patients with advancing stage, there is no significant difference in the preoperative FTC level by disease stage. No elevation in FTC level was found during the laparoscopic procedure in most patients compared with their preoperative FTC value. Patients with a persistently high FTC load [per nucleated blood cells (NBCs)] (> 102 FTCs/106 NBCs) 2 weeks postoperatively portends a poor prognosis regarding disease recurrence and tumor‐related mortality when compared to those with an undetectable or low FTC load (≤ 102 FTCs/106 NBCs). We concluded that the laparoscopic procedure itself had no significantly deleterious effect on circulating FTCs and that the detection of FTCs by real‐time qRT‐PCR might be of clinical importance during the postoperative follow‐up for colorectal cancer patients.

Despite curative tumor resection, about 30%–50% of patients with locally advanced gastrointestinal (GI) carcinoma develop tumor recurrence which may be caused by pre‐ or intraoperative tumor cell dissemination. We examined the combination of optimized density gradient centrifugation with a CK‐20 reverse transcriptase‐polymerase chain reaction to detect and quantify circulating tumor cells in peripheral blood. Peripheral venous blood (20 ml) of patients with GI carcinomas was collected during primary tumor staging before and after the endoscopy procedure. CK‐20 expression in peripheral venous blood was found in 22 of 82 patients (26.8%) with a nonsignificant difference between the upper GI tract (23.9%) and the lower GI tract (30.5%). The correlation with clinical outcome (24‐month‐survival) revealed a significantly worse prognosis (p < 0.05) of CK‐20–positive patients with carcinoma of the upper GI tract and a trend toward a worse prognosis for patients with carcinoma of the lower GI tract. Quantification of CK‐20 expression in peripheral blood showed a significantly higher circulating CK‐20 copy number (median: 2816) in patients with metastatic tumors than in those with non‐metastatic tumors (median: 983) (p < 0.05). For a subset of 42 primarily operated patients, we correlated the detection rate with UICC (International Union Against Cancer) staging categories. In contrast to the upper GI tract, the detection rate of patients with carcinoma of the lower GI tract showed a trend toward tumor size (pT) and a significant correlation with the presence of distant metastases (pM) (p < 0.01) and the postoperative residual tumor status (R) (p < 0.01). The endoscopy procedure did not lead to an increased detection of CK‐20 expression.

The great advances in mPCa management recently obtained with the second-line treatments have highlighted the need to identify and exploit surrogate endpoints for survival of patients and effectiveness of treatment. These surrogate endpoints could be also used to reduce size and costs of pivotal trials of new molecules and the time from the benchtop to the patients’ bedside. A large consensus is emerging in the scientific community that circulating tumor cells (CTCs) meet the criteria required for a surrogate endpoint, particularly in mPCa. The main open question about the clinical management of mPCa is discussed, with the intent to underscore how the extended use of CTC detection and characterization can offer further benefit to these patients.