EGFR-IL-6 Signaling Axis Mediated the Inhibitory Effect of Methylseleninic Acid on Esophageal Squamous Cell Carcinoma.

Yu Wang,Yang Gao,Hongxia Zhu,Xianghe Liu,Mei Liu,Ningzhi Xu,Miaomiao Huo,Chenfei Hu,Guanghui Hu

doi:10.3389/fphar.2021.719785

Abstract

Epidemiological and experimental evidence indicate that selenium is associated with a reduced risk of some cancers, including esophageal cancer. However, the exact mechanism is still unclear. In the present study, we used esophageal squamous cell carcinoma (ESCC) cell lines and animal models to explore the anti-cancer mechanism of methylseleninic acid (MSA). Firstly, MSA treatment dramatically attenuated Epidermal Growth Factor Receptor (EGFR) protein expression but did not alter mRNA levels in ESCC cells. On the contrary, EGFR overexpression partly abolished the inhibitory effect of MSA. With a microRNA-array, we found MSA up-regulated miR-146a which directly targeted EGFR, whereas miR-146a inhibitor antagonized MSA-induced decrease of EGFR protein. We further used 4-nitroquinoline-1-oxide (4NQO)-induced esophageal tumor mice model to evaluate the inhibitory effect of MSA in vivo. MSA treatment significantly decreased the tumor burden and EGFR protein expression in tumor specimens. Furthermore, MSA treatment inhibited EGFR pathway and subsequntly reduced Interleukin-6 (IL-6) secretion in the supernatant of cancer cell lines. MSA-induced IL-6 suppression was EGFR-dependent. To further evaluate the association of IL-6 and the anti-tumor effect of MSA on esophageal cancer, we established the 4NQO-induced esophageal tumor model in IL-6 knock-out (IL-6 KO) mice. The results showed that IL-6 deficiency did not affect esophageal tumorigenesis in mice, but the inhibitory effect of MSA was abolished in IL-6 KO mice. In conclusion, our study demonstrated that MSA upregulated miR-146a which directly targeted EGFR, and inhibited EGFR protein expression and pathway activity, subsequently decreased IL-6 secretion. The inhibitory effect of MSA on esophageal cancer was IL-6 dependent. These results suggested that MSA may serve as a potential drug treating esophageal cancer.

Highlights

Specialty section: This article was submitted to Inflammation Pharmacology, a section of the journal Frontiers in Pharmacology
The results showed that IL-6 deficiency did not affect esophageal tumorigenesis in mice, but the inhibitory effect of methylseleninic acid (MSA) was abolished in IL-6 knock-out (IL-6 KO) mice
Previous studies showed that selenium treatment could downregulate Epidermal Growth Factor Receptor (EGFR) mRNA levels in human biopsy-derived glima cells (Rooprai et al, 2007) and lung cancer cell lines (Shin et al, 2007)

Summary

MATERIALS AND METHODS

The KYSE series was kindly provided by Dr Yutaka Shimada (Kyoto University, Kyoto, Japan). To examine whether MSA suppressed cell growth by downregulating EGFR in ESCC cells, KYSE150 and KYSE510 cells were transfected with EGFR expression plasmid or the empty control plasmid (Figure 1C), and treated with or without MSA, respectively. All these indicated that MSA could inhibit the activation of EGFR pathway in ESCC cells. In accord with the cytokine array, ELISA results showed a significant decrease of IL-6 in the supernant of ESCC cells with MSA treatment (Figure 4D). EGFR overexpression increased the phosphorylation of EGFR, Akt, and STAT3 signaling proteins and could partly restored the inhitory effect of MSA treatment, including the phosphorylation of EGFR, Akt, STAT3 (Figure 5D) and IL-6 mRNA levels in both KYSE150 and KYSE 510 cells (Figure 5E). All these implicated that the anti-tumor effect of MSA was at least partly dependent on IL-6

DISCUSSION

ETHICS STATEMENT