The epithelial-mesenchymal transition phenotype of metastatic lymph nodes impacts the prognosis of esophageal squamous cell carcinoma patients

N-cadherin: A diagnostic marker to help discriminate primary liver carcinomas from extrahepatic carcinomas

Distinguishing primary liver cancer (PLC), namely hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (iCCA), from liver metastases is of crucial clinical importance. Histopathology remains the gold standard, but differential diagnosis may be challenging. While absent in most epithelial, the expression of the adherens junction glycoprotein N-cadherin is commonly restricted to neural and mesenchymal cells, or carcinoma cells that undergo the phenomenon of epithelial-to-mesenchymal transition (EMT). However, we recently established N- and E-cadherin expression as hallmarks of normal hepatocytes and cholangiocytes, which are also preserved in HCC and iCCA. Therefore, we hypothesized that E- and/or N-cadherin may distinguish between carcinoma derived from the liver vs carcinoma of other origins. We comprehensively evaluated E- and N-cadherin in 3359 different tumors in a multicenter study using immunohistochemistry and compared our results with previously published 882 cases of PLC, including 570 HCC and 312 iCCA. Most carcinomas showed strong positivity for E-cadherin. Strong N-cadherin positivity was present in HCC and iCCA. However, except for clear cell renal cell carcinoma (23.6% of cases) and thyroid cancer (29.2%), N-cadherin was only in some instances faintly expressed in adenocarcinomas of the gastrointestinal tract (0%-0.5%), lung (7.1%), pancreas (3.9%), gynecological organs (0%-7.4%), breast (2.2%) as well as in urothelial (9.4%) and squamous cell carcinoma (0%-5.6%). As expected, N-cadherin was detected in neuroendocrine tumors (25%-75%), malignant melanoma (46.2%) and malignant mesothelioma (41%). In conclusion, N-cadherin is a useful marker for the distinction of PLC vs liver metastases of extrahepatic carcinomas (P < .01).

Prognostic significance of positive lymph node regression grade to neoadjuvant chemoradiation for esophageal squamous cell carcinoma

BACKGROUND AND PURPOSE

To assess the relationship between metastatic lymph node (LN) responder status and recurrence-free survival (RFS) in patients undergoing neoadjuvant chemoradiotherapy (NCRT).

MATERIALS AND METHODS

We retrospectively reviewed 304 patients with local advanced esophageal squamous cell carcinoma received NCRT followed by esophagectomy. For 112 patients with positive node, according to the proportion of residual viable tumor cells area within the whole tumor beds of all metastatic LNs, we classified LN-tumor regression grade (LN-TRG) into four categories: grade 1, 0%; 2, <10%; 3, 10%-50%; 4, >50%. Patients with grade 1-2 LN-TRG of were considered LN responders, and those with grades 3-4, as LN nonresponders. Univariate and multivariate analyses of RFS were estimated by a Cox regression model, Kaplan-Meier curve, and log-rank test.

RESULTS

The median follow-up time of a total of 112 patients was 29.6 months. Fifty-two (46.4%) patients have experienced recurrence. In Cox univariate analysis, differentiation, AJCC stage LN responder status, nerve invasion, and lymphovascular invasion significantly correlated with RFS. Multivariate analysis for RFS revealed that LN responder status and AJCC stage (p < 0.05) were independent prognostic factor. The 3-year RFS rates for patients with LN-TRG of 1-4 grades were 72.7%, 76.5%, 37.4%, and 28.5%, respectively, and the median RFS times were not reach, 43.56, 28.09, and 22.77, respectively.

CONCLUSIONS

LN responder status is an independent prognostic factor for RFS in esophageal cancer patients who received NCRT.

Pathological Regression of Lymph Nodes Better Predicts Long-term Survival in Esophageal Cancer Patients Undergoing Neoadjuvant Chemotherapy Followed by Surgery

OBJECTIVE

To evaluate pathological response to NAC in metastatic LNs, and assess its clinical prognostic significance in patients with EC.

SUMMARY OF BACKGROUND DATA

The pathological response to preoperative treatment is commonly evaluated in the PT. However, LN metastases strongly correlate with systemic micro-metastases. Thus, pathological evaluation of LN response could more accurately predict prognosis in EC patients undergoing NAC before surgery.

METHODS

We enrolled 371 consecutive patients who underwent triplet NAC followed by surgery for EC between January 2010 and December 2016. Pathological LN regression grade was defined by the proportion of viable tumor area within the whole tumor bed area for all metastatic LNs: grade I, >50%; II, 10%-50%; III, <10%; and IV, 0%. We analyzed the correlation of grade with clinico-pathological parameters.

RESULTS

Among 319 patients with clinically positive LNs, pathological LN regression grades were I/II/III/IV in 115/51/58/95 patients, and 191 patients (59.9%) showed discordance between the PT and LN pathological regression grades. LN regression grade significantly correlated with cN positive number, ypTNM, lymphovascular invasion, and clinical/pathological PT response. Multivariate analysis for recurrence-free survival revealed that LN regression grade [hazard ratio (HR) = 2.25, P < 0.001], ypT (HR = 1.65, P = 0.005), and ypT (HR = 1.62, P = 0.004) were independent prognostic factors, but not pathological PT regression grade (P = 0.67).

CONCLUSIONS

Compared to PT response, pathological LN response better predicted long-term survival in EC patients who received NAC plus curative surgery.

Lymph Node Response to Neoadjuvant Chemotherapy as an Independent Prognostic Factor in Metastatic Esophageal Cancer

OBJECTIVE

The aim of this study was to evaluate primary tumor (PT) and lymph node (LN) responses to neoadjuvant chemotherapy (NACT) for predicting long-term survival in patients with metastatic esophageal cancer (EC).

BACKGROUND

In evaluating NACT responses in patients with EC, imaging modalities typically target the PT in the esophagus, which is unmeasurable. Targeting measurable organs, like positive LNs, might provide more accurate assessments.

METHODS

We enrolled 251 patients with EC and clinically positive LNs that underwent curative resections, after triplet NACT. The percent reduction of PT area was measured with bidimensional computed tomography. The LN response was defined as the percent reduction of the sum of the short diameters in all positive LNs.

RESULTS

NACT reduced PTs and LNs by (median, range) 58.0% (38.1-94.9) and 34.5% (46.2-68.2), respectively. Based on the receiver-operating characteristic analyses for predicting a histological response and a 10% stepwise cutoff analyses of recurrence-free survival (RFS), responder/nonresponder cutoff values were ≥60% for PT area reductions and ≥30% for LN size reductions. 39.6% of patients showed discordant PT and LN responses. Compared with PT-responders, LN-responders had significantly less advanced pN (P < 0.0001) and pM (P = 0.015) in addition to less advanced pT (P < 0.0001) and better histological responses (P < 0.0001), and closer correlations to lymphatic, distant metastases and dissemination. A multivariate analysis of RFS identified 2 independent prognostic factors: the LN response [hazard ratio (HR) = 2.51, 95% confidence interval (CI) = 1.63-3.95, P < 0.0001] and the pN (HR = 2.72, 95% CI = 1.44-5.64, P = 0.0016), but not the PT response.

CONCLUSIONS

The LN response to NACT predicted long-term survival more precisely than the PT response in patients with metastatic EC.

Partial EMT in Squamous Cell Carcinoma: A Snapshot

In the process of cancer EMT, some subgroups of cancer cells simultaneously exhibit both mesenchymal and epithelial characteristics, a phenomenon termed partial EMT (pEMT). pEMT is a plastic state in which cells coexpress epithelial and mesenchymal markers. In squamous cell carcinoma (SCC), pEMT is regulated, and the phenotype is maintained via the HIPPO pathway, NOTCH pathway and TGF-β pathways and by microRNAs, lncRNAs and the cancer microenvironment (CME); thus, SCC exhibits aggressive tumorigenic properties and high stemness, which leads collective migration and therapy resistance. Few studies have reported therapeutic interventions to address cells that have undergone pEMT, and this approach may be an effective way to inhibit the plasticity, drug resistance and metastatic potential of SCC.

Prognostic Value of a Four-miRNA Signature in Patients With Lymph Node Positive Locoregional Esophageal Squamous Cell Carcinoma Undergoing Complete Surgical Resection

OBJECTIVE

This study was intended to identify prognostic biomarkers for lymph node (LN)-positive locoregional esophageal squamous cell carcinoma (ESCC) patients.

SUMMARY OF BACKGROUND DATA

Surgery is a major treatment for LN-positive locoregional ESCC patients in China. However, patient outcomes are poor and heterogeneous.

METHODS

ESCC-associated miRNAs were identified by microarray and validated by quantitative real-time polymerase chain reaction analyses in ESCC and normal esophageal epithelial samples. A multi-miRNA based classifier was established using a least absolute shrinkage and selection operator model in a training set of 145 LN-positive locoregional ESCCs, and further assessed in internal testing and independent validation sets of 145 and 243 patients, respectively.

RESULTS

Twenty ESCC-associated miRNAs were identified and validated. A 4-miRNA based classifier (miR-135b-5p, miR-139-5p, miR-29c-5p, and miR-338-3p) was generated to classify LN-positive locoregional ESCC patients into high and low-risk groups. Patients with high-risk scores in the training set had a lower 5-year overall survival rate [8.7%, 95% confidence interval (CI): 0-20.3] than those with low-risk scores (50.3%, 95% CI: 40.0-60.7; P < 0.0001). The prognostic accuracy of the classifier was validated in the internal testing (P < 0.0001) and independent validation sets (P = 0.00073). Multivariate survival analyses showed that the 4-miRNA based classifier was an independent prognostic factor, and the combination of the 4-miRNA based classifier and clinicopathological prognostic factors significantly improved the prognostic accuracy of clinicopathological prognostic factors alone.

CONCLUSION

Our 4-miRNA based classifier is a reliable prognostic prediction tool for overall survival in LN-positive locoregional ESCC patients and might offer a novel probability of ESCC treatment individualization.

Emerging Concepts of Hybrid Epithelial-to-Mesenchymal Transition in Cancer Progression

Epithelial mesenchymal transition (EMT) is a complex process through which epithelial (E) cells lose their adherens junctions, transform into mesenchymal (M) cells and attain motility, leading to metastasis at distant organs. Nowadays, the concept of EMT has shifted from a binary phase of interconversion of pure E to M cells and vice versa to a spectrum of E/M transition states preferably coined as hybrid/partial/intermediate EMT. Hybrid EMT, being a plastic transient state, harbours cells which co-express both E and M markers and exhibit high tumourigenic properties, leading to stemness, metastasis, and therapy resistance. Several preclinical and clinical studies provided the evidence of co-existence of E/M phenotypes. Regulators including transcription factors, epigenetic regulators and phenotypic stability factors (PSFs) help in maintaining the hybrid state. Computational and bioinformatics approaches may be excellent for identifying new factors or combinations of regulatory elements that govern the different EMT transition states. Therapeutic intervention against hybrid E/M cells, though few, may evolve as a rational strategy against metastasis and drug resistance. This review has attempted to present the recent advancements on the concept and regulation of the process of hybrid EMT which generates hybrid E/M phenotypes, evidence of intermediate EMT in both preclinical and clinical setup, impact of partial EMT on promoting tumourigenesis, and future strategies which might be adapted to tackle this phenomenon.

A Novel Approach for Quantifying Cancer Cells Showing Hybrid Epithelial/Mesenchymal States in Large Series of Tissue Samples: Towards a New Prognostic Marker

In cancer biology, epithelial-to-mesenchymal transition (EMT) is associated with tumorigenesis, stemness, invasion, metastasis, and resistance to therapy. Evidence of co-expression of epithelial and mesenchymal markers suggests that EMT should be a stepwise process with distinct intermediate states rather than a binary switch. In the present study, we propose a morphological approach that enables the detection and quantification of cancer cells with hybrid E/M states, i.e., which combine partially epithelial (E) and partially mesenchymal (M) states. This approach is based on a sequential immunohistochemistry technique performed on the same tissue section, the digitization of whole slides, and image processing. The aim is to extract quantitative indicators able to quantify the presence of hybrid E/M states in large series of human cancer samples and to analyze their relationship with cancer aggressiveness. As a proof of concept, we applied our methodology to a series of about a hundred urothelial carcinomas and demonstrated that the presence of cancer cells with hybrid E/M phenotypes at the time of diagnosis is strongly associated with a poor prognostic value, independently of standard clinicopathological features. Although validation on a larger case series and other cancer types is required, our data support the hybrid E/M score as a promising prognostic biomarker for carcinoma patients.

Prognostic value of multiple epithelial mesenchymal transition-associated proteins in intrahepatic cholangiocarcinoma

The aim of the present study was to investigate the expression of epithelial mesenchymal transition (EMT)-associated proteins and their prognostic value in intrahepatic cholangiocarcinoma (ICC). The expression of six EMT-associated proteins, including E-cadherin, N-cadherin, Vimentin, Snail family transcriptional repressor 1 (Snail), Snail family transcriptional repressor 2 (Slug) and S100 calcium binding protein A4 (S100A4) was determined by immunohistochemistry in 109 patients with ICC who had received surgery. Survival analysis showed that patients with low E-cadherin expression (P<0.001) or high S100A4 (P<0.001) or Snail (P<0.001) expression had a reduced survival time. Based on the numbers of alterations in the expression of EMT-associated proteins as determined by immunohistochemical analysis, the patients were categorized as low (score, 0-3; n=75) or high (score, ≥4; n=34) EMT expression groups. The high EMT expression group was significantly associated with positive lymph node metastasis (P=0.023) and late Tumor-Node-Metastasis (TNM) stage (P<0.001). Furthermore, patients in the high EMT expression group had a significantly poorer overall survival time than those in the low EMT expression group (P<0.001). Multivariate analysis indicated that EMT status was a significant independent predictor for overall survival time (P=0.004), and was linked to surgical margin (P=0.013) and TNM stage (P<0.001). In conclusion, the reduced expression of E-cadherin and high expression of Snail and S100A4 were significantly associated with the poor survival of patients with ICC after surgery. The EMT protein expression status was associated with ICC progression, and may be considered as an independent prognostic indicator for patients with ICC.

Histone deacetylase 6 expression in metastatic lymph nodes is a valuable prognostic marker for resected node-positive esophageal squamous cell cancer

Background

Histone deacetylase 6 (HDAC6) exerts enzymatic deacetylation activity on histones and on non-histone substrates and plays a key role in microtubule dynamics and chaperone activities. In addition, previous studies have demonstrated its role in cancer progression. However, its clinical significance in esophageal squamous cell cancer (ESCC) has not been elucidated. We investigated the correlation of HDAC6 expression and clinical outcome in a group of T3N1–3M0 surgically resected ESCCs.

Methods

Tissue microarrays were conducted on 209 surgically resected T3N1–3M0 ESCC tumors, including 163 pairs of primary tumors (PTs) and their corresponding metastatic lymph nodes (MLNs). Immunohistochemistry was utilized to evaluate HDAC6 protein levels. The relationship between patient outcomes and HDAC6 expression was analyzed statistically.

Results

The level of HDAC6 expression in ESCC MLNs was found to be significantly lower than that in PTs (P<0.001). Patients with lower MLN HDAC6 expression demonstrated improved overall survival (P=0.011) and disease-free survival (P=0.012) than those with higher HDAC6 expression. HDAC6 expression levels in PTs revealed no prognostic significance. Multivariate analysis showed that the MLN HDAC6 expression level was an independent prognostic factor for both overall survival (HR 1.456, P=0.029) and disease-free survival (HR 1.432, P=0.033).

Conclusion

High expression of HDAC6 in MLNs but not in PTs suggests a poor prognosis for patients with resected T3N1–3M0 ESCC. We should take into account the protein expression of MLNs when assessing prognosis in patients with lymph-node involvement.

Hybrid epithelial/mesenchymal phenotypes promote metastasis and therapy resistance across carcinomas

Cancer metastasis and therapy resistance are the major unsolved clinical challenges, and account for nearly all cancer-related deaths. Both metastasis and therapy resistance are fueled by epithelial plasticity, the reversible phenotypic transitions between epithelial and mesenchymal phenotypes, including epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET). EMT and MET have been largely considered as binary processes, where cells detach from the primary tumor as individual units with many, if not all, traits of a mesenchymal cell (EMT) and then convert back to being epithelial (MET). However, recent studies have demonstrated that cells can metastasize in ways alternative to traditional EMT paradigm; for example, they can detach as clusters, and/or occupy one or more stable hybrid epithelial/mesenchymal (E/M) phenotypes that can be the end point of a transition. Such hybrid E/M cells can integrate various epithelial and mesenchymal traits and markers, facilitating collective cell migration. Furthermore, these hybrid E/M cells may possess higher tumor-initiation and metastatic potential as compared to cells on either end of the EMT spectrum. Here, we review in silico, in vitro, in vivo and clinical evidence for the existence of one or more hybrid E/M phenotype(s) in multiple carcinomas, and discuss their implications in tumor-initiation, tumor relapse, therapy resistance, and metastasis. Together, these studies drive the emerging notion that cells in a hybrid E/M phenotype may occupy 'metastatic sweet spot' in multiple subtypes of carcinomas, and pathways linked to this (these) hybrid E/M state(s) may be relevant as prognostic biomarkers as well as a promising therapeutic targets.

Esophageal squamous cell carcinoma with low mitochondrial copy number has mesenchymal and stem-like characteristics, and contributes to poor prognosis

Alterations in mitochondrial DNA (mtDNA) copy numbers in various human cancers have been studied, but any such changes in esophageal squamous cell carcinoma (ESCC) are not established. In the present study, we investigated the correlation of mtDNA copy number with clinicopathologic features, prognosis, and malignant potential of ESCC. MtDNA copy numbers of resected specimens from 80 patients treated with radical esophagectomy were measured by quantitative real-time PCR analyses. Human ESCC cells, TE8 and TE11, were cultured, and depletion of mtDNA content was induced by knockdown of mitochondrial transcription factor A expression or treatment with ethidium bromide. The mRNA and protein expression, proliferation, invasion, and cell cycle were investigated. The results showed that the mtDNA copy number of cancerous portions was 56.0 (37.4-234.5) percent that of non-cancerous parts and significantly lower (p<0.01). Low mtDNA copy number in resected cancerous tissues was significantly correlated with pathological depth of tumor invasion (p = 0.045) and pathological stage (p = 0.025). Patients with lower mtDNA copy number had significantly poorer 5-year overall survival compared to patients with higher levels (p<0.01). The mtDNA-depleted TE8 and TE11 cells had morphological changes and proliferated more slowly than control cells under normoxia but proliferated at almost the same rate under hypoxic conditions. In mtDNA-depleted cells, E-cadherin mRNA expression was decreased, and N-cadherin, vimentin, zeb-1, and cd44 mRNA expression was increased. Immunoblotting and flow cytometry analysis also showed downregulated E-cadherin and upregulated N-cadherin and CD44 protein in mtDNA-depleted cells. Moreover, mtDNA-depleted cells had enhanced invasion, migration, and sphere formation abilities, and the cell cycle arrest at G0/G1 phase was induced in these cells. These results suggested that mtDNA-depleted ESCC cells had mesenchymal characteristics, cancer stemness, and tolerance to hypoxia, which played important role in cancer progression. In conclusion, a low copy number of mtDNA is associated with tumor progression in ESCC.

The prognostic significance of MCL1 copy number gain in esophageal squamous cell carcinoma

Background

MCL1 copy number variations have been reported to be associated with cancer prognosis in several cancers. However, the role of MCL1 gain has not yet been determined in esophageal squamous cell carcinomas (ESCC).

Methods

Fluorescence in situ hybridization (FISH) for MCL1 was performed on 262 ESCC samples using tissue microarray (TMA).

Results

The median age of ESCC patients was 62 years (range 37-83), with frequencies between women (16.4%) and men (83.6%). Of the 262 tumors, 77 tumors (29.4%) had high MCL1 gain. In the multivariate analysis, lymph node metastasis (HR: 3.236, P<0.001 for DFS; HR: 3.501, P<0.001 for OS) and clinical stage (HR: 3.388, P<0.001 for DFS; HR: 3.616, P<0.001 for OS) were identified as independent worse prognostic factors. Interestingly, among patients without lymph node metastasis or stage I-II patients, high MCL1 gain was associated with better DFS (P=0.009 or 0.046) and OS (P=0.014 or 0.069) after disease free survival time was more than or equal to 12 months. Reversely, among patients with lymph node metastasis or stage III-IVa patients, high MCL1 gain was associated with poorer DFS (P=0.007 or 0.021) and OS (P=0.029 or 0.068) after disease free survival time was more than or equal to 29 months.

Conclusion

We observed that high MCL1 gain had bidirectional prognostic significance in ESCC patients with different lymph node status or clinical stage. These findings might provide the useful way of detailed risk stratification in patients with ESCC, and an insight into pathogenesis and mechanism of progression in ESCC.

Epithelial-to-Mesenchymal Transition and MicroRNAs in Lung Cancer

Despite major advances, non-small cell lung cancer (NSCLC) remains the major cause of cancer-related death in developed countries. Metastasis and drug resistance are the main factors contributing to relapse and death. Epithelial-to-mesenchymal transition (EMT) is a complex molecular and cellular process involved in tissue remodelling that was extensively studied as an actor of tumour progression, metastasis and drug resistance in many cancer types and in lung cancers. Here we described with an emphasis on NSCLC how the changes in signalling pathways, transcription factors expression or microRNAs that occur in cancer promote EMT. Understanding the biology of EMT will help to define reversing process and treatment strategies. We will see that this complex mechanism is related to inflammation, cell mobility and stem cell features and that it is a dynamic process. The existence of intermediate phenotypes and tumour heterogeneity may be debated in the literature concerning EMT markers, EMT signatures and clinical consequences in NSCLC. However, given the role of EMT in metastasis and in drug resistance the development of EMT inhibitors is an interesting approach to counteract tumour progression and drug resistance. This review describes EMT involvement in cancer with an emphasis on NSCLC and microRNA regulation.

Distinct effects of EGFR inhibitors on epithelial- and mesenchymal-like esophageal squamous cell carcinoma cells

Background

Epidermal growth factor receptor (EGFR) plays a pivotal role in the pathophysiology of esophageal squamous cell carcinoma (ESCC). However, the clinical effects of EGFR inhibitors on ESCC are controversial. This study sought to identify the factors determining the therapeutic efficacy of EGFR inhibitors in ESCC cells.

Methods

Immortalized-human esophageal epithelial cells (EPC2-hTERT), transformed-human esophageal epithelial cells (T-Epi and T-Mes), and ESCC cells (TE-1, TE-5, TE-8, TE-11, TE-11R, and HCE4) were treated with the EGFR inhibitors erlotinib or cetuximab. Inhibitory effects on cell growth were assessed by cell counting or cell-cycle analysis. The expression levels of genes and proteins such as involucrin and cytokeratin13 (a squamous differentiation marker), E-cadherin, and vimentin were evaluated by real-time polymerase chain reaction or western blotting. To examine whether mesenchymal phenotype influenced the effects of EGFR inhibitors, we treated T-Epi cells with TGF-β1 to establish a mesenchymal phenotype (mesenchymal T-Epi cells). We then compared the effects of EGFR inhibitors on parental T-Epi cells and mesenchymal T-Epi cells. TE-8 (mesenchymal-like ESCC cells)- or TE-11R (epithelial-like ESCC cells)-derived xenograft tumors in mice were treated with cetuximab, and the antitumor effects of EGFR inhibitors were evaluated.

Results

Cells were classified as epithelial-like or mesenchymal-like phenotypes, determined by the expression levels of E-cadherin and vimentin. Both erlotinib and cetuximab reduced cell growth and the ratio of cells in cell-cycle S phase in epithelial-like but not mesenchymal-like cells. Additionally, EGFR inhibitors induced squamous cell differentiation (defined as increased expression of involucrin and cytokeratin13) in epithelial-like but not mesenchymal-like cells. We found that EGFR inhibitors did not suppress the phosphorylation of EGFR in mesenchymal-like cells, while EGFR dephosphorylation was observed after treatment with EGFR inhibitors in epithelial-like cells. Furthermore, mesenchymal T-Epi cells showed resistance to EGFR inhibitors by circumventing the dephosphorylation of EGFR signaling. Cetuximab consistently showed antitumor effects, and increased involucrin expression in TE-11R (epithelial-like)-derived xenograft tumors but not TE-8 (mesenchymal-like)-derived xenograft tumors.

Conclusions

The factor determining the therapeutic effects of EGFR inhibitors in ESCC cells is the phenotype representing the epithelial-like or mesenchymal-like cells. Mesenchymal-like ESCC cells are resistant to EGFR inhibitors because EGFR signaling is not blocked. EGFR inhibitors show antitumor effects on epithelial-like ESCC cells accompanied by promotion of squamous cell differentiation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-017-0572-7) contains supplementary material, which is available to authorized users.

Silencing of Ribosomal Protein L34 (RPL34) Inhibits the Proliferation and Invasion of Esophageal Cancer Cells

Ribosomal protein L34 (RPL34) belongs to the L34E family of ribosomal proteins and contains a zinc finger motif. Aberrant expression of RPL34 has been reported in several human malignancies. However, the precise role and potential underlying mechanisms of RPL34 in human esophageal cancer remain largely unknown. Thus, the objective of this study was to investigate the role of RPL34 in esophageal cancer progression. Our results showed that the expression of RPL34 at both the mRNA and protein levels was frequently upregulated in esophageal cancer cell lines. Knockdown of RPL34 efficiently inhibited esophageal cancer cell proliferation, migration, and invasion in vitro. Mechanistically, knockdown of RPL34 significantly downregulated the protein expression level of p-PI3K and p-Akt in esophageal cancer cells. Finally, knockdown of RPL34 attenuated tumor growth in nude mice. In conclusion, our study revealed that RPL34 functions as an oncogene that modulates the proliferation and metastasis of esophageal cancer cells, in part, by the inactivation of the PI3K/Akt signaling pathway. Thus, these findings suggest that RPL34 may serve as a potential therapeutic target for the treatment of esophageal cancer.

Knockdown of Ubiquitin-Specific Protease 14 (USP14) Inhibits the Proliferation and Tumorigenesis in Esophageal Squamous Cell Carcinoma Cells

Ubiquitin-specific protease 14 (USP14), one of three proteasome-associated deubiquitinating enzymes (DUBs), plays an essential role in the development of human carcinoma. However, to the best of our knowledge, the role of USP14 in esophageal squamous cell carcinoma (ESCC) is unknown. In the current study, we investigated the expression and role of USP14 in ESCC. Our results showed that the level of USP14 was significantly increased in ESCC tissues and cell lines. Downregulation of USP14 significantly inhibited ESCC cell proliferation and ESCC tumor growth in nude mice. Downregulation of USP14 also suppressed the migration/invasion in ESCC cells. Mechanically, downregulation of USP14 decreased the protein expression levels of β-catenin, cyclin D1, and c-Myc in ESCC cells. In conclusion, our study shows that USP14 plays an important role in the progression and metastasis of ESCC. Therefore, these data suggest that USP14 may be a potentially useful therapeutic strategy for the treatment of ESCC.