Effects of indoleamine 2,3-dioxygenase inhibitor in non-Hodgkin lymphoma model mice.

Nobuhiko Nakamura, Takeshi Hara, Masahito Shimizu, Ryoko Mabuchi, Junji Nagano, Tomohiko Ohno, Takahiro Kochi, Masaya Kubota, Yohei Shirakami, Naoe Goto, Hiroyasu Ito, Kuniaki Saito, Takuji Tanaka, Hisataka Moriwaki, Hisashi Tsurumi

Index: Int. J. Hematol. 102 , 327-34, (2015)

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Abstract

Indoleamine 2,3-dioxygenase (IDO) catalyzes the rate-limiting step in the metabolism of tryptophan along the kynurenine pathway. In tumors, increased IDO activity inhibits proliferation and induces apoptosis of T cells and natural killer cells. We investigated the therapeutic potential of IDO inhibitor 1-methyl-D-tryptophan (D-1MT) with cyclophosphamide (CY) in a mouse model of lymphoma. To examine the effect of D-1MT, mice were killed on day 28. Serum concentrations of L-kynurenine and L-tryptophan were measured by high-performance liquid chromatography. Regulatory T cells (Tregs) were counted by flow cytometry, and mRNA expressions of IDO1, Foxp3, IFN-γ, and COX-2 were examined by quantitative real-time reverse transcription-polymerase chain reaction. D-1MT+CY combination treatment significantly inhibited tumor growth as compared to either treatment alone. There were no significant differences in the serum L-kynurenine/L-tryptophan ratio or the IDO1 expression level in the tumors among the treatment groups. The expression levels of IFN-γ and COX-2 mRNA in tumor-draining lymph nodes (TDLNs) were found to be significantly up-regulated in the CY and D-1MT+CY groups. The number of Tregs in TDLNs in the D-1MT+CY group was significantly lower than that in CY groups on day 17. These results suggest that D-1MT in combination with CY is an effective treatment for lymphoma in a mouse model.