Esophageal carcinoma: Towards targeted therapies

3,3'-Diindolylmethane modulates aryl hydrocarbon receptor of esophageal squamous cell carcinoma to reverse epithelial-mesenchymal transition through repressing RhoA/ROCK1-mediated COX2/PGE2 pathway

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is one of the most aggressive tumors in the world. Aryl hydrocarbon receptor (AHR) has been reported to promote tumor metastasis and epithelial-mesenchymal transition (EMT) is a vital process of conferring cancer cells capabilities of migration and invasion. However, the mechanism by which modulation of AHR can inhibit tumor metastasis remains unknown. Thus, we aim to investigate the underlying mechanism regarding reversing EMT process of ESCC through modulation of AHR.

METHODS

We used AHR selective modulator 3,3'-diindolylmethane (DIM) to treat ESCC cell lines TE1 and KYSE150 so as to examine alterations of migration and invasion by wound healing and Transwell assay. Western blotting (WB) and qPCR were performed to detect relative genes and proteins changes regarding EMT process. Cell transfection was utilized for confirming pathways involved in DIM-induced reversal of EMT and in vivo assay was conducted for verification of the underlying mechanism. Co-IP assay was conducted for detecting protein-protein interactions.

RESULTS

AHR was overexpressed in ESCC and modulation of AHR by DIM could inhibit migration and invasion as well as downregulate mesenchymal cell markers β-Catenin, Vimentin and Slug and upregulate epithelial cell marker Claudin-1. Meanwhile, synergically overexpression of AHR, RhoA and ROCK1 correlated with poor clinical outcomes. DIM could inhibit COX2/PGE₂ pathway by targeting AHR, and COX2 selective inhibitor Celecoxib could suppress EMT and metastasis. Results of PGE₂ treatment were opposite to that of Celecoxib. Meanwhile, blockade of RhoA/ROCK1 pathway also exerted prohibitive effects on EMT and metastasis. WB results showed COX2/PGE₂ pathway could be regulated by RhoA/ROCK1 pathway and DIM could inhibit RhoA/ROCK1 pathway through modulation of AHR. In vivo assay verified the results in vitro. Co-IP results showed DIM could modulate AHR to reverse EMT directly through inhibition of interaction between AHR and EGFR (epidermal growth factor receptor) so as to block RhoA/ROCK1-mediated COX2/PGE₂ pathway which was connected by NF-κB.

CONCLUSIONS

In brief, modulation of AHR by DIM can reverse EMT process and inhibit metastasis of ESCC through repressing RhoA/ROCK1-mediated COX2/PGE₂ pathway.

A lectin-based glycomic approach identifies FUT8 as a driver of radioresistance in oesophageal squamous cell carcinoma

PURPOSE

Radio-resistance is recognized as a main factor in the failure of radiotherapy in oesophageal squamous cell carcinoma (ESCC). Aberrant cell surface glycosylation has been reported to correlate with radio-resistance in different kinds of tumours. However, glycomic alterations and the corresponding enzymes associated with ESCC radio-resistance have not yet been defined.

METHODS

Two radioresistant cell lines, EC109R and TE-1R, were established from parental ESCC cell lines EC109 and TE-1 by fractionated irradiation. A lectin microarray was used to screen for altered glycan patterns. RNA-sequencing (RNA-seq) was employed to identify differentially expressed glycosyltransferases. Cell Counting Kit-8, colony formation and flow cytometry assays were used to measure cell viability and radiosensitivity. Expression of glycosyltransferase in ESCC tissues was assessed by immunohistochemistry. In vivo radiosensitivity was analysed using a nude mouse xenograft model. Downstream effectors of the enzyme were verified using a lectin-based pull-down assay combined with mass spectrometry.

RESULTS

We found that EC109R and TE-1R cells were more resistant to irradiation than the parental EC109 and TE-1 cells. Using lectin microarrays combined with RNA sequencing, we found that α1, 6-fucosyltransferase (FUT8) was overexpressed in the radioresistant ESCC cell lines. Both gain- and loss-of-function studies confirmed that FUT8 regulates the sensitivity of ESCC cells to irradiation. Importantly, we found that high FUT8 expression was positively linked to radio-resistance and a poor prognosis in ESCC patients who received radiation therapy. Moreover, FUT8 inhibition suppressed the growth and formation of xenograft tumours in nude mice after irradiation. Using a lectin-based pull-down assay and mass spectrometry, we found that CD147 could be glycosylated by FUT8. As expected, inhibition of CD147 partly reversed FUT8-induced radio-resistance in ESCC cells.

CONCLUSIONS

Our results indicate that FUT8 functions as a driver of radio-resistance in ESCC by targeting CD147. Therefore, FUT8 may serve as a marker for predicting the response to radiation therapy in patients with ESCC.

Epigenetic Alterations in Oesophageal Cancer: Expression and Role of the Involved Enzymes

Oesophageal cancer is a life-threatening disease, accounting for high mortality rates. The poor prognosis of this malignancy is mostly due to late diagnosis and lack of effective therapies for advanced disease. Epigenetic alterations may constitute novel and attractive therapeutic targets, owing to their ubiquity in cancer and their reversible nature. Herein, we offer an overview of the most important studies which compared differences in expression of enzymes that mediate epigenetic alterations between oesophageal cancer and normal mucosa, as well as in vitro data addressing the role of these genes/proteins in oesophageal cancer. Furthermore, The Cancer Genome Atlas database was interrogated for the correlation between expression of these epigenetic markers and standard clinicopathological features. We concluded that most epigenetic players studied thus far are overexpressed in tumours compared to normal tissue. Furthermore, functional assays suggest an oncogenic role for most of those enzymes, supporting their potential as therapeutic targets in oesophageal cancer.