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IntroductionBrain‐derived neurotrophic factor (BDNF) has an important role in the neurogenesis and neuroplasticity of the brain. This systematic review was designed to examine the association between BDNF Val66Met (rs6265) polymorphism and four cognitive domains—attention and concentration, executive function, verbal fluency, and memory, respectively.MethodologyPrimary literature search was performed using search engines such as PubMed and Scopus. Observational studies that evaluated the neurocognitive performances in relation to BDNF polymorphism within human subjects were included in this review, while animal studies, overlapping studies, and meta‐analysis were excluded.ResultsForty of 82 reviewed studies (48.8%) reported an association between Val66Met polymorphism and neurocognitive domains. The proportion of the studies showing positive findings in cognitive performances between Val/Val homozygotes and Met carriers was comparable, at 30.5% and 18.3%, respectively. The highest percentage of positive association between Val66Met polymorphism and neurocognition was reported under the memory domain, with 26 of 63 studies (41.3%), followed by 18 of 47 studies (38.3%) under the executive function domain and four of 23 studies (17.4%) under the attention and concentration domain. There were no studies showing an association between Val66Met polymorphism and verbal fluency. In particular, Val/Val homozygotes performed better in tasks related to the memory domain, while Met carriers performed better in terms of executive function, in both healthy individuals and clinical populations.ConclusionWhile numerous studies report an association between Val66Met polymorphism and neurocognitive changes in executive function and memory domains, the effect of Met allele has not been clearly established.

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A decline in cognitive function following cancer treatment is one of the most commonly reported post-treatment symptoms among patients with cancer and those in remission, and include memory, processing speed, and executive function. A clear understanding of cognitive impairment as a result of cancer and its therapy can be obtained by delineating structural and functional changes using brain imaging studies and neurocognitive assessments. There is also a need to determine the underlying mechanisms and pathways that impact the brain and affect cognitive functioning in cancer survivors. Exosomes are small cell-derived vesicles formed by the inward budding of multivesicular bodies, and are released into the extracellular environment via an exocytic pathway. Growing evidence suggests that exosomes contribute to various physiological and pathological conditions, including neurological processes such as synaptic plasticity, neuronal stress response, cell-to-cell communication, and neurogenesis. In this review, we summarize the relationship between exosomes and cancer-related cognitive impairment. Unraveling exosomes' actions and effects on the microenvironment of the brain, which impacts cognitive functioning, is critical for the development of exosome-based therapeutics for cancer-related cognitive impairment.Int. J. Mol. Sci. 2020, 21, 2755 2 of 16 attention, learning, and executive function [10]. CRCI adversely affects cancer patients and survivors, causing distress and reduced quality of life, and impacts many facets of their daily lives [11]. CRCI is complicated by many factors including the direct effects of cancer, genetic predisposition (e.g., carrier of apolipoprotein E type epsilon 4 allele [12] and brain-derived neurotrophic factor Met allele [13]), comorbidities independent of the actual disease, and/or treatments or combinations of treatments administered for the disease [14].Efforts to better understand cancer-and cancer-therapy-associated cognitive impairment have relied on methods ranging from cognitive functioning assessment to imaging technologies on brain structure and function (e.g., magnetic resonance imaging scan). However, these approaches may be limited to help us understand the etiology and pathophysiology of cognitive dysfunction. The emerging application of the use of liquid biopsies (e.g., plasma and cerebrospinal fluid) as a strategy for biomarker discovery to detect, assess and monitor CRCI is fast-expanding and evolving [15,16]. In published literature, studies have revealed that genetics and neurobiological and immunological mechanisms may be involved in the biogenesis and development of CRCI. Preclinical studies have also provided insights into the pathophysiological mechanisms underlying CRCI, including neurotoxicity and inflammatory factors, which were shown to be responsible for CRCI [17]. Nevertheless, the underlying mechanisms of CRCI have yet to be established. While the role of exosomes in cancer has been well-documented [18][19][20], the role of cancer exosomes and their ability ...

Cancer‐related fatigue (CRF) is subjective and has wide inter‐individual variability. Given that leptin is commonly associated with fatigue syndrome, its use as a potential biomarker for CRF is being investigated. The primary objective of this study was to evaluate the association between leptin and CRF in early‐stage breast cancer patients receiving chemotherapy. In a prospective cohort study, patients completed assessments at baseline (T1), during chemotherapy (T2) and after chemotherapy (T3). Levels of plasma leptin and adipokines were measured using a Luminex bead‐immunoassay and CRF was measured using the Multi‐Dimensional Fatigue Symptom Inventory‐Short Form (MFSI‐SF). Data were analysed longitudinally using a generalised estimating equation incorporating clinically relevant parameters and pro‐inflammatory adipokines. The analysis included 136 patients (mean age ± SD = 51.5 ± 8.8 years; 69.1% receiving anthracycline‐based chemotherapy). More patients experienced CRF at T3 (23.8%) than at T2 (13.8%) compared to baseline. An increase was observed in the median plasma leptin level at T2, followed by a decrease at T3 (T1: 4.07 ng/mL, T2: 4.95 ng/mL and T3: 3.96 ng/mL). In the multivariate model, the change in leptin levels over time was significantly associated with the total MFSI‐SF score ( β = −0.15, P = 0.003) after adjusting for the tumour necrosis factor‐α (TNF‐α) level, anxiety, depression, insomnia, age, menopausal status and type of chemotherapy. This is the first study to report leptin as a biomarker that predicts the onset of CRF over time. Future studies are required to validate the findings.

Background: There is little information about cancer-related cognitive impairment (CRCI) in adolescent and young adults (AYA, 15-39 years old) due to its rare incidence. Here, we present the pre-treatment (before chemotherapy or radiotherapy) evaluation of cognitive function and ability of AYA with cancer (AYAC) in a multicentered cohort study. Methods: Newly diagnosed AYAC and age-matched healthy controls (HC) were recruited between 2018 and 2021. The primary outcome was the comparison of pre-treatment cognitive impairment defined as 2 standard deviations (SDs) below the HC on ≥1 cognitive test, or >1.5 SDs below on ≥2 tests using CANTAB® between AYAC and HC. Secondary outcomes included self-perceived cognitive ability assessed by FACT-Cog v3 and biomarkers (inflammatory cytokines and brain-derived neurotrophic factor [BDNF]). Results:We recruited 74 AYAC (median age = 34) and 118 HC (median age = 32). On objective cognitive testing, we observed three times more AYAC patients performed poorly on at least 2 cognitive tests compared to HC (40.5% vs. 13.6%, p < 0.001). AYAC self-perceived less degree of cognitive impairment than HC (p < 0.001). However, AYAC perceived a greater impact of cognitive changes on their quality of life compared to HC (p = 0.039). Elevated baseline inflammatory markers (IL-2, IL-4, IL-6, IL-8, IL-10 and IFN-γ) were observed among AYAC compared to HC, and baseline BDNF was lower in AYAC compared to HC. Interaction effects between cancer diagnosis and biomarkers were observed in predicting cognitive function. Conclusion:With the pre-existence of CRCI and risk factors of neuroinflammation even prior to systemic therapy, AYAC should receive early rehabilitation to prevent further deterioration of cognitive function after initiation of systemic therapies. (Clini calTr ials.gov Identifier: NCT03476070).

Cancer-related cognitive impairment (CRCI) adversely affects cancer patients. We had previously demonstrated that the BDNF Val66Met genetic polymorphism is associated with lower odds of subjective CRCI in the multitasking and verbal ability domains among breast cancer patients receiving chemotherapy. To further assess our previous findings, we evaluated the association of BDNF Val66Met polymorphism with subjective and objective CRCI in a temporally separate cohort of patients and pooled findings from both the original ( n = 145) and current ( n = 193) cohorts in a meta-analysis. Subjective CRCI was assessed using FACT-Cog. Objective CRCI was evaluated using computerized neuropsychological tests. Genotyping was carried out using Sanger sequencing. The association of BDNF Val66Met genotypes and CRCI was examined with logistic regression. A fixed-effect meta-analysis was conducted using the inverse variance method. In the meta-analysis ( n = 338), significantly lower odds of CRCI were associated with Met allele carriers based on the global FACT-Cog score (OR = 0.52, 95% CI 0.29–0.94). Furthermore, Met allele carriers were at lower odds of developing impairment in the domains of memory (OR = 0.34, 95% CI: 0.17–0.70), multitasking (OR = 0.33, 95% CI: 0.18–0.59), and verbal ability (OR = 0.46, 95% CI: 0.24–0.88). Consistent with the previous study, lower odds of subjective CRCI among patients with the BDNF Met allele was observed after adjusting for potential confounders in the multitasking (OR = 0.30, 95% CI: 0.14–0.67) domain. In conclusion, carriers of the BDNF Met allele were protected against global subjective CRCI, particularly in the domains of memory, multitasking, and verbal ability. Our findings further contribute to the understanding of CRCI pathophysiology. Electronic supplementary material The online version of this article (10.1007/s12035-018-1410-4) contains supplementary material, which is available to authorized users.