Different effects of tryptophan 2,3-dioxygenase inhibition on SK-Mel-28 and HCT-8 cancer cell lines

Abstract

Purpose Indoleamine 2,3-dioxygenase-1 (IDO1) and more recently, tryptophan 2,3-dioxygenase (TDO), are tryptophancatabolizing enzymes with immunoregulatory properties in cancer. IDO1 is more expressed than TDO in many tumours including melanomas; however, IDO inhibitors did not give expected results in clinical trials, highlighting the need to consider TDO. We aimed to characterize both TDO expression and function in a melanoma cell line, named SK-Mel-28, with the purpose to compare it with a colon cancer cell line, HCT-8, and with a human endothelial cell line (HUVEC). Methods TDO expression was assessed as real time-PCR and western blot, for mRNA and protein expression, respectively. While cell proliferation was assessed as cell duplication, cell apoptosis and cell cycle were analysed by means of flow cytometry. Results SK-Mel-28 cells showed higher TDO levels compared to HCT-8 and to HUVEC cells. A selective TDO inhibitor, 680C91, significantly impaired cell proliferation in a concentration-dependent manner, by inducing cell arrest during the G2 phase for SK-Mel-28 and HUVEC cells, while an early apoptosis was increasing in HCT-8 cells. No toxic effects were observed. These data demonstrated that TDO is highly expressed in SK-Mel-28 cells and may be involved in the regulation of their proliferation. Conclusion TDO may directly modulate cancer cell function rather than immune suppression and can be considered as a target for melanoma progression together with IDO1.

Dexamethasone Induces the Expression and Function of Tryptophan-2-3-Dioxygenase in SK-MEL-28 Melanoma Cells

“…Because TDO is involved in the regulation of SK-Mel-28 growth [ 24 ], and since dex induced TDO up-regulation, we then wished to determine whether dex stimulates SK-Mel-28 proliferation via TDO. Our results show that dex significantly and concentration-dependently increased SK-Mel-28 proliferation ( Figure 5 A).…”

“…To delineate the mechanisms underlying the proliferative effect of dex, cells were pretreated for 15 min with 680C91 (40 μM), a selective TDO inhibitor, followed by dex (25 μM). Interestingly, 680C91 significantly hampered cell proliferation by 41.2 ± 7.1%, without affecting either cell viability [ 24 ] or cell duplication in response to FGF2 ( Figure 5 C). Furthermore, inhibition of IDO1 with 1-MT or epacadostat, a newer IDO1 inhibitor, potentiated dex-induced cell proliferation ( Figure 5 D).…”

“…Quantitative real-time PCR (qRT-PCR) was carried out using SYBR Premix Ex Taq (Takara) according to the manufacturer instructions on a Rotorgene RG-3000A cycle system (Qiagen) platform. Primer sequences were the following: TDO2 fw: 5′-CTTATCTCCAGCATCAGGCTTCCAGAGT-3′ and rev: 5′-GGAGTTCTTTCCAGCCATGCCTCC-3′ [ 24 ], IDO1 amplification fw: 5′-AGTTCTGGGATGCATCACCA-3′ and rev: 5′-CAGTTTCTTGGAGAGTTGGCA-3′ and AHR amplification fw: 5′-CAAATCCTTCCAAGCGGCATA-3′ and rev: 5′-CGCTGAGCCTAAGAACTGAAA-3′.…”

“…Based on these considerations, this study was undertaken to better characterize TDO/KP in SK-Mel-28, a human melanoma cell line. We previously demonstrated that TDO is constitutively expressed in these cells and that it directly regulates their proliferation [ 24 ]. However, the effect of dex on TDO expression and function remained unclear.…”

Clinicopathologic features of TDO2 overexpression in renal cell carcinoma

“…It was reported that phosphorylation of AKT and ERK controls apoptosis [ 33 ]. Interestingly, a recently developed TDO2 inhibitor has shown an ability to impair cell proliferation by inducing apoptosis and cell cycle arrest [ 34 ]. These data suggest that TDO2 may take part in the activation of EGFR and promote tumor growth in RCC.…”