FOXP3 inhibits NF-κB activity and hence COX2 expression in gastric cancer cells
Introduction
Gastric cancer is one of the most common malignant tumors in the world [1]. Previous studies have shown that expression of Cyclooxygenase-2 (COX2) is significantly higher than in normal gastric tissue and plays as a key molecule in the development of gastric cancer [2]. Expression of COX2 has been found to be significantly correlated with lymph node metastasis, poor differentiation and advanced tumor/node/metastasis (TNM) staging. The detection of COX2 is helpful in judging the prognosis of gastric cancer [3]. Among the regulators of COX2 expression, NF-κB, nuclear factor κB, is recognized as the key regulator [4]. NF-κB itself plays an important role in tumor growth and metastasis, and COX2 in turn is the most important downstream mediator [5]. Constitutive activation of NF-κB is a common feature of several tumor cells. Expression of COX2 is up-regulated by activated NF-κB in various kinds of stimuli or other carcinogenic factors, thus inducing apoptosis, proliferation imbalance and other changes, eventually inducing carcinogenesis. Up to now, how COX2 is regulated by NF-κB in gastric cancer and whether there are endogenous co-activators and co-repressors is still largely unknown.
Forkhead box protein 3 (FOXP3) belongs to the forkhead/winged-helix family of transcriptional regulators. While most studies mainly focused on regulatory T cells (Tregs) and their role in immunosuppression [6], [7], there are still some studies indicating that FOXP3 was also expressed in some cancer cells [8]. FOXP3 expression in different tumor cells may have different functions. Most of the studies suggest a tumor suppressor role for FOXP3. Researchers reported that the expression of FOXP3 inhibited the expression of HER-2 [9], SKP2 [10]. It is reported that FOXP3 played a cancer suppressor role in MCF-7 cells by transcriptionally activating p21 expression, suggesting a tumor suppressor role in breast cancer [11]. The interaction between FOXP3 and NF-κB in tumor cells and its functional role in inflammatory microenvironment have also been reported. Foxp3 interacts with NF-κB to repress cytokine gene expression and effector functions of T helper cells [12]. We also report that p65 could interact with FOXP3 and in turn inhibit FOXP3 mediated p21 transcription activation [13], and to some extent dilute the tumor suppressor role of FOXP3. However, how FOXP3 regulates the activity of NF-κB still awaits elucidation. It is especially interesting to see whether how NF-κB and FOXP3 interaction affects NF-κB target gene, such as COX2. Here, we examined the expression of COX2, nuclear localization of NF-κB, NF-κB activity and the expression of FOXP3 in different gastric cancer cell lines. Our study here revealed that expression of COX2, is correlated with NF-κB activity rather than nuclear localization only. Further study revealed that FOXP3 interacts with p65 and in turn inhibits NF-κB activation. FOXP3 and NF-κB expression levels together determine the NF-κB activity and thus COX2 expression. In summary, our study here revealed that FOXP3 functions as a negative regulator of NF-κB activity and thus plays a tumor suppressor role by reducing cell metastasis.
Section snippets
Cell culture
Normal gastric epithelial cell lines (GES-1), and gastric cancer cell lines AGS, MKN45, MKN28 and SGC7901, were cultured in 1640 medium (Invitrogen, Carlsbad, CA), supplemented with 2 mmol/L glutamine, 0.06 g/L penicillin, 0.1 g/L streptomycin, and 10% fetal bovine serum (FBS) at 37 °C in a humidified atmosphere of 5% CO2.
RNA interference and gene transfection
FOXP3 siRNAs (GenePharma, Shanghai, China) were synthesized to knockdown FOXP3 expression in cells. A scrambled siRNA (GenePharma) that targets no known genes was used as a
NF-κB activity correlates with COX2 expression better than solely p65 nuclear localization
First, different gastric cancer cell lines and the normal gastric epithelium were used to study the relationship between COX2 and NF-κB. COX2 expression in both was found upregulated in cancerous cell lines, both at mRNA and protein levels (Fig. 1A and B). COX2 was highly expressed in some low differentiated cell lines. As COX2 is a well-known NF-κB target gene, we next examined nuclear p65 expression in these cell lines. Strikingly, COX2 expression is not closely correlated with p65 nuclear
Discussion
Gastric cancer remains the main cause of cancer deaths worldwide, and the key reason for death was gastric cancer metastasis. Our study here has revealed that COX2 expression in gastric cancer cells are coordinately regulated by FOXP3 and NF-κB. By inhibiting NF-κB activity, which is the key factor for COX2 induction, FOXP3 inhibits the expression of COX2 and hence cell metastasis, thus playing a tumor suppressor role.
COX2 expression was induced to attenuate the degree of atrophic gastritis,
Conclusions
Taken together, our data demonstrates that FOXP3 interacts with p65 and in turn inhibits NF-κB activation. FOXP3 and NF-κB expression levels together determine the NF-κB activity and thus COX2 expression. Our study here reveals that FOXP3 functions as a negative regulator of NF-κB activity and thus plays a tumor suppressor role by reducing cell metastasis. Our study has revealed an instinctive negative regulator of NF-κB, and thus rescue of FOXP3 expression and function might pave the way to
Acknowledgments
This work was supported by grants from the Natural Science Foundation of China (NSFC, Nos. 81001182, 31000406, 30972672, 81171978). We appreciate the valuable comments from the other members of our laboratories.
References (24)
- et al.
J. Biol. Chem.
(2005) - et al.
Biochem. Biophys. Res. Commun.
(2013) - et al.
Cell. Signal.
(2008) - et al.
Hum. Pathol.
(2009) - et al.
J. Biol. Chem.
(2003) - et al.
CA Cancer J. Clin.
(2012) - et al.
Ai Zheng
(2002) - et al.
Oncol. Rep.
(1999) - et al.
Cell. Oncol.: Off. J. Int. Soc. Cell. Oncol.
(2007) - et al.
Nat. Immunol.
(2005)
Nat. Immunol.
J. Transl. Med.
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These authors contributed equally to this work.