Clinicopathological significance of indoleamine 2,3-dioxygenase 1 expression in colorectal cancer

  • Ferdinande L
  • Decaestecker C
  • Verset L
 et al. 
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BACKGROUND: Indoleamine 2,3-dioxygenase 1 (IDO1) is a tryptophan-catabolising enzyme that induces immune tolerance by modulating T-cell responses. Carcinomas may create an immunosuppressive state via IDO1 expression. Here we examined a possible contribution of IDO1 on this phenomenon and investigated whether IDO1 has prognostic value in colorectal cancer (CRC).

METHODS: IDO1 expression was investigated by quantitative PCR and western blotting in three colon cancer cell lines, in basal state and after interferon (IFN)-γ stimulation. Semi-quantitative immunohistochemistry was used to evaluate IDO1 expression in 265 pT1-4N0-2Mx-staged CRCs. Results were related to clinical variables and correlated with amounts of CD3(+) and CD8(+) T lymphocytes, which were quantitatively evaluated using image analysis.

RESULTS: In vitro expression of IDO1 depended on IFN-γ stimulation. Higher IDO1 expression at the tumour invasion front was an independent adverse prognostic factor in pT1-4N1Mx-staged CRC. It was associated with overall survival (P=0.001) and with metachronous metastases (P=0.018). IDO1 expression was not associated with the presence of CD3(+) or CD8(+) T lymphocytes.

CONCLUSION: Higher IDO1 expression at the tumour invasion front is involved in CRC progression and correlates with impaired clinical outcome, suggesting that IDO1 is an independent prognostic indicator for CRC.

Author-supplied keywords

  • colon cancer cell lines
  • colorectal cancer
  • immunohistochemistry
  • indoleamine 2,3-dioxygenase 1
  • tumour invasion front

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