The role of EMT and MET in cancer dissemination

Epithelial-to-mesenchymal transition, circulating tumor cells and cancer metastasis: Mechanisms and clinical applications

Epithelial-to-mesenchymal transition (EMT) endows epithelial cells with enhanced motility and invasiveness, allowing them to participate in many physiological and pathological processes. Epithelial-to-mesenchymal transition contributes to the generation of circulating tumor cells (CTCs) in epithelial cancers because it increases tumor cell invasiveness, promotes tumor cell intravasation and ensures tumor cell survival in the peripheral system. Although the contribution of epithelial-to-mesenchymal transition to tumor cell invasiveness has been confirmed, the role epithelial-to-mesenchymal transition plays in metastasis remains debated. As a favorable material for a “liquid biopsy”, circulating tumor cells have been shown to have promising values in the clinical management of tumors. Furthermore, an increasing number of studies have begun to explore the value of CTC-related biomarkers, and some studies have found that the expression of EMT and stemness markers in circulating tumor cells, in addition to CTC detection, can provide more information on tumor diagnosis, treatment, prognosis and research.

MiR-520b as a novel molecular target for suppressing stemness phenotype of head-neck cancer by inhibiting CD44

Cancer stem cells preferentially acquire the specific characteristics of stress tolerance and high mobility, allowing them to progress to a therapy-refractive state. To identify a critical molecule to regulate cancer stemness is indispensable to erratically cure cancer. In this study, we identified miR-520b as a novel molecular target to suppress head-neck cancer (HNC) with stemness phenotype. MiR-520b inhibited cellular migration and invasion via the mechanism of epithelial-mesenchymal transition. It also sensitized cells to therapeutic drug and irradiation. Significantly, miR-520b suppressed spheroid cell formation, as well as reduced expressions of multiple stemness regulators (Nestin, Twist, Nanog, Oct4). The CD44 molecule was identified as a direct target of miR-520b, as shown by the reverse correlative expressions, the response to miR-520 modulation, the luciferase reporter assay, and the functional rescue analyses. These cellular results were confirmed by a tumor xenograft mice study. Administration of miR-520b dramatically restrained tumorigenesis and liver colonization. Conversely, miR-520b silencing led to an acceleration of tumor growth. Taken together, our study demonstrated that miR-520b inhibits the malignancy of HNC through regulation of cancer stemness conversion by targeting CD44. MiR-520b may serve as an emerging therapeutic target that may be further developed for the intervention of refractory HNC.

miR-10a suppresses colorectal cancer metastasis by modulating the epithelial-to-mesenchymal transition and anoikis

MicroRNAs (miRNAs) have a critical role in tumorigenesis and metastasis, which are major obstacles of cancer therapy. However, the role of miRNAs in colorectal cancer (CRC) metastasis remains poorly understood. Here, we found that miRNA-10a (miR-10a) was upregulated in primary CRC tissues and cell line (SW480) derived from primary CRC compared with metastatic cancer tissues in lymph node and cell line (SW620). The differential expression of miR-10a was inversely correlated with distant metastasis and invasion depth. miR-10a promoted migration and invasion in vitro but inhibited metastasis in vivo by regulating the epithelial-to-mesenchymal transition and anoikis. Furthermore, matrix metalloproteinase 14 (MMP14) and actin gamma 1 (ACTG1) were validated as target genes of miR-10a in CRC cells. Ectopic expression of MMP14 and ACTG1 counteracted the decreased cell adhesion and anoikis resistance activities induced by miR-10a. These findings not only describe the mechanism by which miR-10a suppresses CRC metastasis but also suggest the potential prognostic and therapeutic value of miR-10a in CRC patients.

The relationship between platinum drug resistance and epithelial-mesenchymal transition

One of the most commonly used chemotherapeutics, platinum drugs are used to treat a wide range of cancer types. Although many cancers initially respond well to those drugs, drug resistance occurs frequently and different molecular mechanisms have been associated with it. However, predictive biomarkers of cellular response in specific tumour types still do not exist. Epithelial-mesenchymal transition (EMT) is a malignant cancer phenotype characterized by aggressive invasion and metastasis, and resistance to apoptosis. Recent studies indicate that EMT accompanies the development of drug resistance to a number of cancer chemotherapies. The link between these two phenomena is still not elucidated, although several important molecules involved in both these complex processes, such as transcription factors (SNAIL, TWIST, ZEB, etc.) and miRNAs (miRNA-200 family, miR-15, miR-186, etc.) have been recognized as important. This article reviews numerous unresolved issues regarding platinum drugs resistance and EMT, the complexity of the signalling networks that regulate those two phenomena and their importance in tumour response and spreading which are becoming focuses of interest of many scientists. This article also presents molecules involved in platinum resistance and EMT as possible targets for new cancer therapy.

The role of lymphangiogenesis and angiogenesis in tumor metastasis

BACKGROUND

Metastasis is the main cause of mortality in cancer patients. Two major routes of cancer cell spread are currently being recognized: dissemination via blood vessels (hematogenous spread) and dissemination via the lymphatic system (lymphogenous spread). Here, our current knowledge on the role of both blood and lymphatic vessels in cancer cell metastasis is summarized. In addition, I will discuss why cancer cells select one or both of the two routes to disseminate and I will provide a short description of the passive and active models of intravasation. Finally, lymphatic vessel density (LVD), blood vessel density (BVD), interstitial fluid pressure (IFP) and tumor hypoxia, as well as regional lymph node metastasis and the recently discovered primo vascular system (PVS) will be highlighted as important factors influencing tumor cell motility and spread and, ultimately, clinical outcome.

CONCLUSIONS

Lymphangiogenesis and angiogenesis are important phenomena involved in the spread of cancer cells and they are associated with a poor prognosis. It is anticipated that new discoveries and advancing knowledge on these phenomena will allow an improvement in the treatment of cancer patients.

Endometrial androgen signaling and decidualization regulate trophoblast expansion and invasion in co-culture: A time-lapse study

INTRODUCTION

To elucidate whether trophoblast expansion and invasion are modulated by androgen signaling in an in vitro co-culture model system with decidualizing endometrial stromal cells (ESCs).

METHODS

We employed an in vitro co-culture model of early embryo implantation, consisting of human ESCs (EtsT499 cells) and spheroids generated by extravillous trophoblast (EVT) derived HTR8/Svneo. The ESCs were decidualized with 8-bromo-cAMP (8-br-cAMP) in the presence or absence of dihydrotestosterone (DHT) at various concentrations for 5 days before co-culture with EVT spheroids. Trophoblast expansion was monitored by fluorescent time-lapse imaging microscopy. ESCs motility was visualized by using CellTracker™ Orange CMRA fluorescent probe. Apoptosis of ESCs was detected by CellEvent™ Caspase-3/7^® green detection reagent. Invasion assays were performed to quantify EVT invasion through a chemotaxis cell membrane.

RESULTS

Expansion of EVT spheroids was significantly enhanced by decidualized compared to undifferentiated ESCs. This process was further stimulated if ESCs were first decidualized in the presence of DHT. In contrast to decidualized ESCs, undifferentiated cells actively migrated away from expanding EVT spheroids. Invasiveness of EVT toward decidualized ESCs was significantly attenuated in comparison to undifferentiated ESCs. DHT had no effect on EVT invasion. However, an inhibitor of intercellular gap junction communication significantly enhanced EVT invasion towards decidualized ESCs.

CONCLUSIONS

These results indicate distinct roles for androgen signaling and gap junction formation in decidual cells in regulating trophoblast expansion and invasion.

Transketolase Serves a Poor Prognosticator in Esophageal Cancer by Promoting Cell Invasion via Epithelial-Mesenchymal Transition

Background: To characterize the potential function and clinical significance of Transketolase (TKT) in esophageal cancer.

Methods: High invasive esophageal squamous cell carcinoma (ESCC) cell line CE48T/VGH was used. Cellular functions in response to TKT modulation were examined, including cell growth, migration and invasion. The underlying molecules involved in the TKT regulatory mechanism were determined by western blot and confocal microscopic analysis. Clinically, TKT expressions in 76 ESCC patients were assessed by immunohistochemical (IHC) method, and the association with treatment outcome was determined.

Results: TKT silencing inhibited cell migration and invasion but had a minimal effect on cell growth. This TKT silencing also induced the reversion of epithelial-mesenchymal transition (EMT), as evidenced by the spindle to cuboidal morphological change, increased the expression of epithelial markers (γ-catenin), and decreased the levels of mesenchymal markers (fibronectin and N-cadherin). Mechanically, TKT was shown to modulate the EMT through the pERK-Slug/Snail-associated signaling pathway. Clinically, a high level of TKT in the cancer tissues of patients with esophageal squamous cell carcinoma was associated with poor survival (P = 0.042). In the multivariate analysis, a high TKT level was also shown to be an independent unfavorable prognostic factor (Odds ratio: 1.827, 95% confidence interval: 1.045-3.196, P = 0.035).

Conclusions: TKT contributes to esophageal cancer by promoting cell invasion via meditating EMT process. Clinically, the over-expression of TKT in ESCC patients predicts poorer survival. TKT inhibition may be a useful strategy to intervene in cancer cell invasion and metastasis, which may lead to better prognosis for ESCC patients.

Attenuated LKB1-SIK1 signaling promotes epithelial-mesenchymal transition and radioresistance of non-small cell lung cancer cells

Background

Radiotherapy is one of the main therapeutic approaches for non–small cell lung cancer (NSCLC). However, radioresistant cancer cells can eventually cause tumor relapse and even fatal metastasis. It is thought that radioresistance and metastasis could be potentially linked by epithelial-mesenchymal transition (EMT). In this study, we established radioresistant NSCLC cells to investigate the potential relationship among radioresistance, EMT, and enhanced metastatic potential and the underlying mechanism involving liver kinase B1 (LKB1)-Salt-inducible kinase 1 (SIK1) signaling.

Methods

The radioresistant cell lines A549R and H1299R were generated by dose-gradient irradiation of the parental A549 and H1299 cells. The radioresistance/sensitivity was evaluated by Cell Counting Kit-8 assay, apoptosis analysis, and/or clonogenic cell survival assay. The EMT phenotype and the signaling change were assessed by Western blotting. The abilities of invasion and migration were evaluated by transwell assays and wound healing assays.

Results

The radioresistant cell lines A549R and H1299R displayed mesenchymal features with enhanced invasion and migration. Mechanistically, A549R and H1299R cells had attenuated LKB1-SIK1 signaling, which leaded to the up-regulation of Zinc-finger E-box-binding homeobox factor 1 (ZEB1)—a transcription factor that drives EMT. Re-expression of LKB1 in A549R cells reversed the EMT phenotype, whereas knockdown of LKB1 in H1299R cells further promoted the EMT phenotype. Moreover, re-expression of LKB1 in A549 cells increased the radiosensitivity, whereas knockdown of LKB1 in H1299 cells decreased the radiosensitivity.

Conclusions

Our findings suggest that attenuated LKB1-SIK1 signaling promotes EMT and radioresistance of NSCLC cells, which subsequently contributes to the enhanced metastatic potential. Targeting the LKB1-SIK1-ZEB1 pathway to suppress EMT might provide therapeutic benefits.

Mimicking Metastases Including Tumor Stroma: A New Technique to Generate a Three-Dimensional Colorectal Cancer Model Based on a Biological Decellularized Intestinal Scaffold

Tumor models based on cancer cell lines cultured two-dimensionally (2D) on plastic lack histological complexity and functionality compared to the native microenvironment. Xenogenic mouse tumor models display higher complexity but often do not predict human drug responses accurately due to species-specific differences. We present here a three-dimensional (3D) in vitro colon cancer model based on a biological scaffold derived from decellularized porcine jejunum (small intestine submucosa+mucosa, SISmuc). Two different cell lines were used in monoculture or in coculture with primary fibroblasts. After 14 days of culture, we demonstrated a close contact of human Caco2 colon cancer cells with the preserved basement membrane on an ultrastructural level as well as morphological characteristics of a well-differentiated epithelium. To generate a tissue-engineered tumor model, we chose human SW480 colon cancer cells, a reportedly malignant cell line. Malignant characteristics were confirmed in 2D cell culture: SW480 cells showed higher vimentin and lower E-cadherin expression than Caco2 cells. In contrast to Caco2, SW480 cells displayed cancerous characteristics such as delocalized E-cadherin and nuclear location of β-catenin in a subset of cells. One central drawback of 2D cultures—especially in consideration of drug testing—is their artificially high proliferation. In our 3D tissue-engineered tumor model, both cell lines showed decreased numbers of proliferating cells, thus correlating more precisely with observations of primary colon cancer in all stages (UICC I-IV). Moreover, vimentin decreased in SW480 colon cancer cells, indicating a mesenchymal to epithelial transition process, attributed to metastasis formation. Only SW480 cells cocultured with fibroblasts induced the formation of tumor-like aggregates surrounded by fibroblasts, whereas in Caco2 cocultures, a separate Caco2 cell layer was formed separated from the fibroblast compartment beneath. To foster tissue generation, a bioreactor was constructed for dynamic culture approaches. This induced a close tissue-like association of cultured tumor cells with fibroblasts reflecting tumor biopsies. Therapy with 5-fluorouracil (5-FU) was effective only in 3D coculture. In conclusion, our 3D tumor model reflects human tissue-related tumor characteristics, including lower tumor cell proliferation. It is now available for drug testing in metastatic context—especially for substances targeting tumor–stroma interactions.

Correlation of standard diffusion-weighted imaging and diffusion kurtosis imaging with distant metastases of rectal carcinoma

PURPOSE

To investigate the correlation of standard diffusion-weighted imaging (DWI) and diffusion kurtosis imaging (DKI) with distant metastases of rectal carcinoma.

MATERIALS AND METHODS

Fifty-eight patients with rectal carcinoma (27 with distant metastasis and 31 with no metastasis) were included in this study. The apparent diffusion coefficient (ADC) value from standard DWI (b values of 0 and 1000 sec/mm(2) ), Dapp , and Kapp from DKI (b values of 0, 700, 1400, and 2000 sec/mm(2) ) were acquired with a 3.0T magnetic resonance imaging (MRI) scanner. These quantitative parameters were calculated from the entire tumors. Receiver operating characteristic curve analyses were conducted to assess the utility for discrimination of tumor with distant metastasis and those without metastasis. Parameters were compared using the independent-samples t-test.

RESULTS

The histogram metrics 10th percentile of Dapp (Dapp-10th ) and ADC values (ADC10th ) were significantly lower in the distant metastasis group than those without metastasis (972.5 ± 118.8 vs. 1121.3 ± 133.8 × 10(-6) mm(2) /s, P = 0.03; 809.2 ± 67.1 vs. 856.2 ± 72.1 × 10(-6) mm(2) /s, P = 0.03). Dapp-10th showed relatively higher area under the curve (AUC) (0.856 vs. 0.669, P = 0.024), and higher specificity (100% vs. 68%) than ADC10th did for differentiation of lesions with distant metastasis from those without metastasis.

CONCLUSION

DKI was relatively better than standard DWI in discriminating rectal carcinoma with distant metastasis from those without metastasis. J. Magn. Reson. Imaging 2016;44:221-229.