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. 2020 Oct;22(4):472-484.
doi: 10.1177/1099800420938141. Epub 2020 Jun 30.

Systematic Review of the Kynurenine Pathway and Psychoneurological Symptoms Among Adult Cancer Survivors

Hongjin Li  1   2 , Tingting Liu  3 , Lacey W Heinsberg  4 , Mark B Lockwood  1 , Derek A Wainwright  5 , Min Kyeong Jang  1   2 , Ardith Z Doorenbos  1   2
Affiliations

Systematic Review of the Kynurenine Pathway and Psychoneurological Symptoms Among Adult Cancer Survivors

Hongjin Li et al. Biol Res Nurs. 2020 Oct.

Abstract

The co-occurrence of multiple psychoneurological symptoms, including pain, sleep disturbance, fatigue, depression, anxiety, and cognitive disturbance among adult cancer survivors led us to question which common biological mechanisms are shared among these conditions. Variances in tryptophan (Trp) levels and downstream metabolites of the kynurenine (Kyn) metabolic pathway are known to affect immune response and psychoneurological symptoms. The objective of this systematic review was to help us (a) better understand the role of the Kyn pathway in psychoneurological symptoms among adult cancer survivors and (b) identify common significant biomarkers across psychoneurological symptoms as a guide for future research. Some evidence has shown that decreased Trp levels and increased Kyn, Trp/Kyn ratio, and kynurenic acid/Trp ratio in parallel with immune activation are correlated with some psychoneurological symptoms among people undergoing cancer treatment, although discrepancies exist between studies. Kyn pathway activation could also be associated with psychoneurological symptoms among adult cancer survivors, but further research is needed to confirm its exact etiological role with respect to psychoneurological symptoms.

Keywords: cancer; kynurenine; metabolite; psychoneurological; survivor; symptom; tryptophan.

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Conflict of interest statement

Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Figures

Figure 1.
Figure 1.
Conceptual diagram of effects of inflammatory and hypothalamic-pituitary-adrenal (HPA)-axis activation on tryptophan and kynurenine pathways. Cancer and cancer treatment can activate inflammation and the HPA axis, which results in increased levels of inflammatory cytokines and cortisol. Stimulated by inflammatory cytokines and cortisol, the rate-limiting enzymes IDO and TDO are induced and catabolize tryptophan to kynurenine. CRP = C-reactive protein; IDO = indoleamine 2,3-dioxygenase 1; IFN-ϒ = interferon gamma; IL = interleukin; KAT = kynurenine aminotransferase; KMO = kynurenine monooxygenase; TDO = tryptophan 2,3-dioxygenase; TNF = tumor necrosis factor.
Figure 2.
Figure 2.
Study selection process.
See this image and copyright information in PMC

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