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Meta-Analysis
. 2020 May 26;20(1):471.
doi: 10.1186/s12885-020-06956-5.

The prognostic value of IDO expression in solid tumors: a systematic review and meta-analysis

Sen Wang  1   2 , Jia Wu  1 , Han Shen  3 , Junjun Wang  4
Affiliations
Meta-Analysis

The prognostic value of IDO expression in solid tumors: a systematic review and meta-analysis

Sen Wang et al. BMC Cancer. .

Abstract

Background: Indoleamine 2,3-dioxygenase (IDO) is a rate-limiting enzyme in the metabolism of tryptophan into kynurenine. It is considered to be an immunosuppressive molecule that plays an important role in the development of tumors. However, the association between IDO and solid tumor prognosis remains unclear. Herein, we retrieved relevant published literature and analyzed the association between IDO expression and prognosis in solid tumors.

Methods: Studies related to IDO expression and tumor prognosis were retrieved using PMC, EMbase and web of science database. Overall survival (OS), time to tumor progression (TTP) and other data in each study were extracted. Hazard ratio (HR) was used for analysis and calculation, while heterogeneity and publication bias between studies were also analyzed.

Results: A total of 31 studies were included in this meta-analysis. Overall, high expression of IDO was significantly associated with poor OS (HR 1.92, 95% CI 1.52-2.43, P < 0.001) and TTP (HR 2.25 95% CI 1.58-3.22, P < 0.001). However, there was significant heterogeneity between studies on OS (I2 = 81.1%, P < 0.001) and TTP (I2 = 54.8%, P = 0.007). Subgroup analysis showed lower heterogeneity among prospective studies, studies of the same tumor type, and studies with follow-up periods longer than 45 months.

Conclusions: The high expression of IDO was significantly associated with the poor prognosis of solid tumors, suggesting that it can be used as a biomarker for tumor prognosis and as a potential target for tumor therapy.

Keywords: IDO; Meta-analysis; Solid tumor; Survival.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
The flow chart of the selection process in our meta-analysis
Fig. 2
Fig. 2
Meta-analysis of impact of IDO expression on prognosis of patients with solid tumors. Forest plot of HRs for correlation between IDO expression and OS in solid tumor patients. Results are presented as individual and metaHR, and 95% CI. The random-effects model was used. The square size of individual studies represented the weight of the study. Vertical lines represent 95% CI of the pooled estimate. The diamond represents the overall summary estimate, with the 95% CI given by its width
Fig. 3
Fig. 3
Forest plot of HRs for correlation between IDO expression and TTP in solid tumor patients. Results are presented as individual and metaHR, and 95% CI. The random-effects model was used. The square size of individual studies represents the weight of the study. Vertical lines represent 95% CI of the pooled estimate. The diamond represents the overall summary estimate, with the 95% CI given by its width
Fig. 4
Fig. 4
Begg’s funnel plots and Egger’s publication bias plots for studies involved in the meta-analysis. Begg’s funnel plots for the studies included in meta-analysis regarding. OS (a) and TTP (b). Each hazard ratio (HR) was plotted on an HR scale against its standard error (SE). The horizontal lines indicate the pooled estimate of the overall HR, with the sloping lines reflecting the expected 95% confidence interval for a given SE. Egger’s publication bias plots for the studies included in meta-analysis regarding OS (c) and TTP (d). The 95% confidence intervals of the regression line’s y intercept include zero, P values were 0.59 and 0.89, respectively, indicating that there was no evidence of publication bias
Fig. 5
Fig. 5
Sensitivity analysis of the meta-analysis. a Overall survival. b Time to tumor progression. The vertical axis at 1.98 and 2.25 indicates the overall HR, and the vertical lines on either side of 1.98 and 2.25 indicate the 95% CI. Every hollow round indicates the pooled HR when the left study was omitted in a meta-analysis with a random model. The two ends of every broken line represent the respective 95% CI
See this image and copyright information in PMC

References

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