Retinoic acid morpholine amide (RAMA) inhibits expression of Fas ligand through EP1 receptor in colon cancer cells
Among the members of tumour necrosis factor family Fas ligand on binding to its receptor strongly induces apoptosis of tumour-infiltrating lymphocytes (TIL). Thus, FasL acts as an inhibitor of anti-tumour immune response. The present study demonstrates that retinoic acid morpholine amide (RAMA) significantly suppresses FasL expression in colon cancer cells in a dose- and time-dependent manner. The suppression of FasL mRNA and proteins was significant at a concentration of 30 μM after 48 h in CLT85 and HT26 colon cancer cells. There was around 2.6- and 3.2-fold decrease in FasL mRNA after incubation with 30 μM of RAMA in CLT85 cells and HT26 cells, respectively. The results from Western blot showed a decrease in FasL mRNA and protein expression in both CLT85 and HT26 cells after suppression of cyclooxygenase (COX)-2 and COX-1 by RNAi. However, when COX-2-specific silencer RNA (siCOX-2)- and siCOX-1-treated CLT85 and HT26 cells were exposed to RAMA, inhibition of FasL expression was further suppressed. The siCOX-2-treated CLT85 and HT26 cells on exposure to RAMA showed ∼87 and ∼54 % reduction in FasL mRNA, respectively. Co-culture of Jurkat T cells with RAMA-treated HT26 and CLT85 cells decreased the viability of Jurkat T cells by only 2 and 4.3 %, respectively, compared to 19.5 and 37.3 % in control HT26 and CLT85 cells. The results from real-time reverse transcription polymerase chain reaction (RT-PCR) and immunoblotting showed that suppression of EP1 prevented RAMA-induced FasL suppression in CLT85 cells at both the mRNA and protein levels. Thus, RAMA can be a potent therapeutic agent for the treatment of colon tumours.
KeywordsTumour necrosis Immune response Cytotoxicity Fas-sensitive
This work was supported by Project (No: 2013DFA31510) and China-Japan Friendship Hospital Youth Science and Technology Excellence Project (No. 2015-QNYC-B-02).
Conflicts of interest
Shao-Xuan Chen, Li Yao and Shi-Yu Du designed the study. Yun-Ting Wang, Hong-Chuan Zhao and Yan-Li Zhang wrote the manuscript. Shi-Yu Du carried out the cell culture and Western blot. All authors approved the final version of the manuscript.
- 7.Bennett MW, O’Connell J, Houston A, Kelly J, O’Sullivan GC, Collins JK, et al. Fas ligand upregulation is an early event in colonic carcinogenesis. J ClinPathol. 2001;54:598–604.Google Scholar
- 11.Barnhart BC, Legembre P, Pietras E, Bubici C, Franzoso G, Peter ME. CD95 ligand induces motility and invasiveness of apoptosis-resistant tumor cells. EMBO J. 2004;22:22.Google Scholar
- 18.Moon RC, McCormick DL, Mehta RG. Inhibition of carcinogenesis by retinoids. Cancer Res. 1983;43:2469.Google Scholar