Alterations of gene expression in blood cells associated with chronic fatigue in breast cancer survivors

Cancer-Related Fatigue and Circulating Biomarkers in Breast Cancer Survivors

PURPOSE

Cancer-related fatigue (CRF) is the most common and disruptive symptom experienced by cancer survivors and because of its frequency and severity is especially worrisome in breast cancer survivors (BCS). Despite a great deal of research, the mechanisms underlying CRF have not been determined. The present study aims to describe associations between CRF in BCS and different blood biomarkers.

METHODS

A descriptive and cross-sectional study was conducted. A set of biomarkers assessing inflammation were measured in BCS: C-reactive protein (CRP), neutrophil-lymphocyte ratio (NLR), IL-1β, IL-6, IL-8, IL-10, tumor necrosis factor (TNF); HPA axis dysfunction (cortisol), autonomic dysfunction (noradrenaline); oxidative stress (8-OH deoxyguanosine); insulin resistance markers (insulin, IGF-I, IGFBP3) and sexual hormones (estrogens, progesterone, testosterone).

RESULTS

NLR (p = .00) and cortisol (p = .02) were positive and negatively associated with CRF, respectively. The rest of the blood markers were not associated with CRF.

CONCLUSION

Our results increase the evidence on pathophysiological mechanisms driving CRF in BCS. However, longitudinal studies are needed to explore the role of these factors as potential causal mechanisms.

Biological mechanisms of cancer-related fatigue in breast cancer survivors after treatment: a scoping review

PURPOSE

Cancer-related fatigue (CRF) is the most common symptom experienced by cancer survivors. It is a multidimensional symptom affecting physical, emotional, and/or cognitive spheres, different from other types of fatigue. Characteristically is not alleviated by sleep or rest. CRF could have specific features in breast cancer survivors (BCS), because of sex, hormones, and distinct treatments. On the other hand, more than 25% of BCS report persistent CRF for 10 years or more after the diagnosis. The present study aims to recapitulate the knowledge about the biological mechanisms that potentially drive CRF in BCS after treatment.

METHODS

To answer a broad question, a scoping review methodology was used. Data were collated from three bibliographic databases: PubMed, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL). Studies were selected if they had included more than 20 BCS, after finishing their treatment, fatigue was measured with a quantitative scale and biomarkers were analyzed.

RESULTS

The final database was composed of 1896 records. Sixty-four studies finally met the eligibility criteria. Inflammation (61%), hypothalamic-pituitary-adrenal (HPA) axis dysregulation (14%), autonomic nervous system (ANS) dysfunction (11%), and diet (9%) were the biological pathways most frequently studied. Unfortunately, results from studies about inflammation and HPA axis show many inconsistencies.

CONCLUSION

More research about the role of ANS dysfunction and diet on the pathogenesis of CRF would be warranted according to the results of the review. There are some fields such as endocannabinoid systems, mitochondrial dysfunction, gut microbiota, and oxidative stress that have been insufficiently explored.

IMPLICATIONS FOR CANCER SURVIVORS

To widen the scope of future research in the physiopathology of CRF, it is necessary to identify mechanisms that would be potentially involved and have been insufficiently explored. Because of the high prevalence of CRF in BCS and the tremendous impact that fatigue has in their quality of life, it is essential to improve the efficacy of the treatments through a good knowledge of the biological basis of CRF.

Perturbations in common and distinct inflammatory pathways associated with morning and evening fatigue in outpatients receiving chemotherapy

BACKGROUND

Moderate to severe fatigue occurs in up to 94% of patients with cancer. Recent evidence suggests that morning and evening fatigue are distinct dimensions of physical fatigue. The purposes of this study were to evaluate the transcriptome for common and distinct perturbed inflammatory pathways in patients receiving chemotherapy who reported low versus high levels of morning or low versus high levels of evening cancer-related fatigue.

METHODS

Patients completed questionnaires during the week prior to their chemotherapy treatment. Severity of morning and evening fatigue was evaluated using the Lee Fatigue Scale. Gene expression and pathway impact analyses (PIA) were performed in two independent samples using RNA-sequencing (n = 357) and microarray (n = 360). Patterns of interactions between and among these perturbed pathways were evaluated using a knowledge network (KN).

RESULTS

Across the PIA, nine perturbed pathways (FDR < 0.025) were common to both morning and evening fatigue, six were distinct for morning fatigue, and four were distinct for evening fatigue. KN (19 nodes, 39 edges) identified the phosphatidylinositol 3-kinase (PI3K)-Akt pathway node (perturbed in evening fatigue) with the highest betweenness (0.255) and closeness (0.255) centrality indices. The next highest betweenness centrality indices were seen in pathways perturbed in evening fatigue (i.e., nuclear factor kappa B: 0.200, natural killer cell-mediated cytotoxicity: 0.178, mitogen-activated protein kinase: 0.175).

CONCLUSIONS

This study describes perturbations in common and distinct inflammatory pathways associated with morning and/or evening fatigue. PI3K-Akt was identified as a bottleneck pathway. The analysis identified potential targets for therapeutic interventions for this common and devastating clinical problem.

A Pilot Study Using a Multistaged Integrated Analysis of Gene Expression and Methylation to Evaluate Mechanisms for Evening Fatigue in Women Who Received Chemotherapy for Breast Cancer

CONTEXT

Fatigue is the most common symptom associated with cancer and its treatment. Investigation of molecular mechanisms associated with fatigue may identify new therapeutic targets.

OBJECTIVE

The objective of this pilot study was to evaluate the relationships between gene expression and methylation status and evening fatigue severity in women with breast cancer who received chemotherapy.

METHODS

Latent class analysis (LCA) was used to identify evening fatigue phenotypes. In this analysis, the lowest (i.e., moderate, n = 7) and highest (i.e., very high, n = 29) fatigue-severity classes identified using LCA were analyzed via two stages. First, a total of 32,609 transcripts from whole blood were evaluated for differences in expression levels between the classes. Next, 637 methylation sites located within the putative transcription factor binding sites for those genes demonstrating differential expression were evaluated for differential methylation state between the classes.

RESULTS

A total of 89 transcripts in 75 unique genes were differentially expressed between the moderate (the lowest fatigue-severity class identified) and very high evening fatigue classes. In addition, 23 differentially methylated probes and three differentially methylated regions were found between the moderate and very high evening fatigue classes.

CONCLUSIONS

Using a multistaged integrated analysis of gene expression and methylation, differential methylation was identified in the regulatory regions of genes associated with previously hypothesized mechanisms for fatigue, including inflammation, immune function, neurotransmission, circadian rhythm, skeletal muscle energy, carbohydrate metabolism, and renal function as well as core biological processes including gene transcription and the cell-cycle regulation.

Genomic mechanisms of fatigue in survivors of colorectal cancer

BACKGROUND

Many cancer survivors experience fatigue as a nagging symptom lasting years after treatment. To learn of the relevant biological pathways involved in fatigue among cancer survivors, the authors tested for an association between fatigue levels and leukocyte gene expression profiles and determined the specific mediating immune cell types.

METHODS

A sample of 89 Hispanic/Latino adults aged 60.5 years, 62% of whom were male, who were diagnosed with colorectal cancer and were 2.9 years since diagnosis provided blood for transcriptome profiling and completed a validated measure of fatigue (Multidimensional Fatigue Symptom Inventory-Short Form). The authors applied genome-wide transcriptional profiling of leukocyte RNA to identify gene expression activity associated with fatigue, tested for the activity of specific transcription factors involved in previously established markers of inflammation and immunologic activation, and identified the specific cell types mediating these transcriptional alterations.

RESULTS

In analyses adjusting for demographic and behavioral health risk factors, results linked fatigue with increased activation of B lymphocytes and CD8-positive T cells, as well as several transcription factors involved in immune activation (nuclear factor κB [NF-κB], signal transducer and activator of transcription [STAT], and cAMP responsive element-binding protein [CREB]). Results also replicated several specific genomic effects previously observed in fatigued cancer survivors, including upregulated expression of α-synuclein (SNCA) and hemoglobin subunits (HBA and HBB).

CONCLUSIONS

Cancer survivors' heightened fatigue levels may be partially explained by activation of specific immune cell subsets, thereby providing a potential molecular biomarker for clinical interventions targeting the remediation of fatigue. Cancer 2018;124:2637-44. © 2018 American Cancer Society.

Genetic contributions to self-reported tiredness

Self-reported tiredness and low energy, often called fatigue, are associated with poorer physical and mental health. Twin studies have indicated that this has a heritability between 6 and 50%. In the UK Biobank sample (N=108 976), we carried out a genome-wide association study (GWAS) of responses to the question, 'Over the last two weeks, how often have you felt tired or had little energy?' Univariate GCTA-GREML found that the proportion of variance explained by all common single-nucleotide polymorphisms for this tiredness question was 8.4% (s.e.=0.6%). GWAS identified one genome-wide significant hit (Affymetrix id 1:64178756_C_T; P=1.36 × 10-11). Linkage disequilibrium score regression and polygenic profile score analyses were used to test for shared genetic aetiology between tiredness and up to 29 physical and mental health traits from GWAS consortia. Significant genetic correlations were identified between tiredness and body mass index (BMI), C-reactive protein, high-density lipoprotein (HDL) cholesterol, forced expiratory volume, grip strength, HbA1c, longevity, obesity, self-rated health, smoking status, triglycerides, type 2 diabetes, waist-hip ratio, attention deficit hyperactivity disorder, bipolar disorder, major depressive disorder, neuroticism, schizophrenia and verbal-numerical reasoning (absolute rg effect sizes between 0.02 and 0.78). Significant associations were identified between tiredness phenotypic scores and polygenic profile scores for BMI, HDL cholesterol, low-density lipoprotein cholesterol, coronary artery disease, C-reactive protein, HbA1c, height, obesity, smoking status, triglycerides, type 2 diabetes, waist-hip ratio, childhood cognitive ability, neuroticism, bipolar disorder, major depressive disorder and schizophrenia (standardised β's had absolute values<0.03). These results suggest that tiredness is a partly heritable, heterogeneous and complex phenomenon that is phenotypically and genetically associated with affective, cognitive, personality and physiological processes.

Differential expression of genes and differentially perturbed pathways associated with very high evening fatigue in oncology patients receiving chemotherapy

PURPOSE

Fatigue is the most common symptom associated with cancer and its treatment. Investigation of molecular mechanisms associated with fatigue in oncology patients may identify new therapeutic targets. The objectives of this study were to evaluate the relationships between gene expression and perturbations in biological pathways and evening fatigue severity in oncology patients who received chemotherapy (CTX).

METHODS

The Lee Fatigue Scale (LFS) and latent class analysis were used to identify evening fatigue phenotypes. We measured 47,214 ribonucleic acid transcripts from whole blood collected prior to a cycle of CTX. Perturbations in biological pathways associated with differential gene expression were identified from public data sets (i.e., Kyoto Encyclopedia Gene and Genomes, BioCarta).

RESULTS

Patients were classified into Moderate (n = 65, mean LFS score 3.1) or Very High (n = 195, mean LFS score 6.4) evening fatigue groups. Compared to patients with Moderate fatigue, patients with Very High fatigue exhibited differential expression of 29 genes. A number of the perturbed pathways identified validated prior mechanistic hypotheses for fatigue, including alterations in immune function, inflammation, neurotransmission, energy metabolism, and circadian rhythms. Based on our findings, energy metabolism was further divided into alterations in carbohydrate metabolism and skeletal muscle energy. Alterations in renal function-related pathways were identified as a potential new mechanism.

CONCLUSIONS

This study identified differential gene expression and perturbed biological pathways that provide new insights into the multiple and likely inter-related mechanisms associated with evening fatigue in oncology patients.

Fatigue During and After Breast Cancer Therapy-A Prospective Study

CONTEXT

Chronic fatigue (CF) in breast cancer (BC) survivors is multifactorial and may be caused by immune activation triggered by BC or its treatment. In the Neoadjuvant Avastin in Breast Cancer study, BC patients received neoadjuvant chemotherapy (FEC100→taxane) ± bevacizumab, a monoclonal antibody with fatigue as a potential side effect.

OBJECTIVES

To examine fatigue levels and prevalence of CF before and during chemotherapy and at follow-up, and their associations with C-reactive protein (CRP) and clinical variables.

METHODS

Eighty-four HER2-negative patients with cT2-4N0-3M0 BC responded to questionnaires and had CRP measured before treatment (T0), after FEC100 (T1), after taxanes before surgery (T2), and at two-year follow-up (T3).

RESULTS

The prevalence of CF increased from 8% at T0 to 36% at T3, P < 0.0001. Fatigue levels peaked during chemotherapy from 12.0 at T0 to 20.0 at T2, and declined to 16.7 at T3, P < 0.001. Women with CF at T3 had higher fatigue levels at T0, T2, and T3 than those without CF (P ≤ 0.01). Psychological distress (P = 0.03) and pain (P = 0.04) at T3 were associated with CF at T3. Only psychological distress remained a significant predictor in multivariate analysis. CRP increased from T0 to T1 (P < 0.01) and declined to baseline values at T3, but changes were not associated with bevacizumab treatment. No association was found between bevacizumab or CRP, and fatigue levels or CF.

CONCLUSION

Neither bevacizumab treatment nor low-grade systemic inflammation as measured by CRP was associated with the increased fatigue levels and raised prevalence of CF, observed during and after BC therapy. Increased fatigue levels at baseline and psychological distress at T3 were associated with CF at T3.

Inflammatory pathway genes associated with inter-individual variability in the trajectories of morning and evening fatigue in patients receiving chemotherapy

Fatigue, a highly prevalent and distressing symptom during chemotherapy (CTX), demonstrates diurnal and interindividual variability in severity. Little is known about the associations between variations in genes involved in inflammatory processes and morning and evening fatigue severity during CTX. The purposes of this study, in a sample of oncology patients (N=543) with breast, gastrointestinal (GI), gynecological (GYN), or lung cancer who received two cycles of CTX, were to determine whether variations in genes involved in inflammatory processes were associated with inter-individual variability in initial levels as well as in the trajectories of morning and evening fatigue. Patients completed the Lee Fatigue Scale to determine morning and evening fatigue severity a total of six times over two cycles of CTX. Using a whole exome array, 309 single nucleotide polymorphisms SNPs among the 64 candidate genes that passed all quality control filters were evaluated using hierarchical linear modeling (HLM). Based on the results of the HLM analyses, the final SNPs were evaluated for their potential impact on protein function using two bioinformational tools. The following inflammatory pathways were represented: chemokines (3 genes); cytokines (12 genes); inflammasome (11 genes); Janus kinase/signal transducers and activators of transcription (JAK/STAT, 10 genes); mitogen-activated protein kinase/jun amino-terminal kinases (MAPK/JNK, 3 genes); nuclear factor-kappa beta (NFkB, 18 genes); and NFkB and MAP/JNK (7 genes). After controlling for self-reported and genomic estimates of race and ethnicity, polymorphisms in six genes from the cytokine (2 genes); inflammasome (2 genes); and NFkB (2 genes) pathways were associated with both morning and evening fatigue. Polymorphisms in six genes from the inflammasome (1 gene); JAK/STAT (1 gene); and NFkB (4 genes) pathways were associated with only morning fatigue. Polymorphisms in three genes from the inflammasome (2 genes) and the NFkB (1 gene) pathways were associated with only evening fatigue. Taken together, these findings add to the growing body of evidence that suggests that morning and evening fatigue are distinct symptoms.

Genomic Variants Associated With Cancer-Related Fatigue: A Systematic Review

BACKGROUND

Cancer-related fatigue (CRF) is the most common stressful side effect caused by cancer and cancer treatments. Although CRF causes a significant burden to quality of life, no pharmacologic interventions are available because the mechanism remains unknown.

OBJECTIVES

This systematic review analyzed the genomic variants that have been found to be associated with CRF.

METHODS

A search for peer-reviewed articles through PubMed, EBSCOhost, and DePaul WorldCat Libraries Worldwide yielded 16 published studies.

FINDINGS

The majority of genomic variants demonstrated that the inflammatory and immune response pathways, including the neuro-proinflammatory cytokine pathway, have statistically significant associations with CRF. Additional genomic studies are still needed to validate the findings in this systematic review. The exact biologic underpinnings that contribute to the development of CRF remain unknown.

Gene Expression Profiling of Evening Fatigue in Women Undergoing Chemotherapy for Breast Cancer

Moderate-to-severe fatigue occurs in up to 94% of oncology patients undergoing active treatment. Current interventions for fatigue are not efficacious. A major impediment to the development of effective treatments is a lack of understanding of the fundamental mechanisms underlying fatigue. In the current study, differences in phenotypic characteristics and gene expression profiles were evaluated in a sample of breast cancer patients undergoing chemotherapy (CTX) who reported low (n = 19) and high (n = 25) levels of evening fatigue. Compared to the low group, patients in the high evening fatigue group reported lower functional status scores, higher comorbidity scores, and fewer prior cancer treatments. One gene was identified as upregulated and 11 as downregulated in the high evening fatigue group. Gene set analysis found 24 downregulated and 94 simultaneously up- and downregulated pathways between the two fatigue groups. Transcript origin analysis found that differential expression (DE) originated primarily from monocytes and dendritic cell types. Query of public data sources found 18 gene expression experiments with similar DE profiles. Our analyses revealed that inflammation, neurotransmitter regulation, and energy metabolism are likely mechanisms associated with evening fatigue severity; that CTX may contribute to fatigue seen in oncology patients; and that the patterns of gene expression may be shared with other models of fatigue (e.g., physical exercise and pathogen-induced sickness behavior). These results suggest that the mechanisms that underlie fatigue in oncology patients are multifactorial.

A Transcriptional Signature of Fatigue Derived from Patients with Primary Sjögren's Syndrome

Background

Fatigue is a debilitating condition with a significant impact on patients’ quality of life. Fatigue is frequently reported by patients suffering from primary Sjögren’s Syndrome (pSS), a chronic autoimmune condition characterised by dryness of the eyes and the mouth. However, although fatigue is common in pSS, it does not manifest in all sufferers, providing an excellent model with which to explore the potential underpinning biological mechanisms.

Methods

Whole blood samples from 133 fully-phenotyped pSS patients stratified for the presence of fatigue, collected by the UK primary Sjögren’s Syndrome Registry, were used for whole genome microarray. The resulting data were analysed both on a gene by gene basis and using pre-defined groups of genes. Finally, gene set enrichment analysis (GSEA) was used as a feature selection technique for input into a support vector machine (SVM) classifier. Classification was assessed using area under curve (AUC) of receiver operator characteristic and standard error of Wilcoxon statistic, SE(W).

Results

Although no genes were individually found to be associated with fatigue, 19 metabolic pathways were enriched in the high fatigue patient group using GSEA. Analysis revealed that these enrichments arose from the presence of a subset of 55 genes. A radial kernel SVM classifier with this subset of genes as input displayed significantly improved performance over classifiers using all pathway genes as input. The classifiers had AUCs of 0.866 (SE(W) 0.002) and 0.525 (SE(W) 0.006), respectively.

Conclusions

Systematic analysis of gene expression data from pSS patients discordant for fatigue identified 55 genes which are predictive of fatigue level using SVM classification. This list represents the first step in understanding the underlying pathophysiological mechanisms of fatigue in patients with pSS.

Genomic Profile of Fatigued Men Receiving Localized Radiation Therapy

PURPOSE

The purpose of this study was to explore gene expression changes in fatigued men with nonmetastatic prostate cancer receiving localized external beam radiation therapy (EBRT).

METHODS

Fatigue was measured in 40 men with prostate cancer (20 receiving EBRT and 20 controls on active surveillance) using the Functional Assessment of Cancer Therapy-Fatigue (FACT-F). EBRT subjects were followed from baseline to midpoint and end point of EBRT, while controls were seen at one time point. EBRT subjects were categorized into high- and low-fatigue groups based on change in FACT-F scores from baseline to EBRT completion. Full genome microarray was performed from peripheral leukocyte RNA to determine gene expression changes related to fatigue phenotypes. Real-time polymerase chain reaction and enzyme-linked immunosorbent assay confirmed the most differentially expressed gene in the microarray experiment.

RESULTS

At baseline, mean FACT-F scores were not different between EBRT subjects (44.3 ± 7.16) and controls (46.7 ± 4.32, p = .24). Fatigue scores of EBRT subjects decreased at treatment midpoint (38.6 ± 9.17, p = .01) and completion (37.6 ± 9.9, p = .06), indicating worsening fatigue. Differential expression of 42 genes was observed between fatigue groups when EBRT time points were controlled. Membrane-spanning four domains, subfamily A, member (MS4A1) was the most differentially expressed gene and was associated with fatigue at treatment end point (r = -.46, p = .04).

CONCLUSION

Fatigue intensification was associated with MS4A1 downregulation, suggesting that fatigue during EBRT may be related to impairment in B-cell immune response. The 42 differentially expressed fatigue-related genes are associated with glutathione biosynthesis, γ-glutamyl cycle, and antigen presentation pathways.

The biology of cancer-related fatigue: a review of the literature

PURPOSE

Understanding the etiology of cancer-related fatigue (CRF) is critical to identify targets to develop therapies to reduce CRF burden. The goal of this systematic review was to expand on the initial work by the National Cancer Institute CRF Working Group to understand the state of the science related to the biology of CRF and, specifically, to evaluate studies that examined the relationships between biomarkers and CRF and to develop an etiologic model of CRF to guide researchers on pathways to explore or therapeutic targets to investigate.

METHODS

This review was completed by the Multinational Association of Supportive Care in Cancer Fatigue Study Group-Biomarker Working Group. The initial search used three terms (biomarkers, fatigue, cancer), which yielded 11,129 articles. After removing duplicates, 9145 articles remained. Titles were assessed for the keywords "cancer" and "fatigue" resulting in 3811 articles. Articles published before 2010 and those with samples <50 were excluded, leaving 75 articles for full-text review. Of the 75 articles, 28 were further excluded for not investigating the associations of biomarkers and CRF.

RESULTS

Of the 47 articles reviewed, 25 were cross-sectional and 22 were longitudinal studies. More than half (about 70 %) were published recently (2010-2013). Almost half (45 %) enrolled breast cancer participants. The majority of studies assessed fatigue using self-report questionnaires, and only two studies used clinical parameters to measure fatigue.

CONCLUSIONS

The findings from this review suggest that CRF is linked to immune/inflammatory, metabolic, neuroendocrine, and genetic biomarkers. We also identified gaps in knowledge and made recommendations for future research.

Biomarkers of fatigue related to adjuvant chemotherapy for breast cancer: evaluation of plasma and lymphocyte expression

Background

Fatigue is common in cancer patients receiving adjuvant chemotherapy. To further understand the mechanism of fatigue and search for potential biomarkers, we conducted this prospective study. Methods

We enrolled breast cancer (BC) patients before their first adjuvant Adriamycin-based chemotherapy cycle. Patients responded to the brief fatigue inventory (BFI) and Chalder fatigue questionnaires and had their blood drawn for both plasma evaluation and evaluation of the peripheral mononuclear cell fraction (PMNCF) mRNA expression of various biomarkers. We evaluated FSH, LH, estradiol, DHEA, DHEAS, IL6, IL2, ILIRA, IL1β, CRP, Cortisol in the plasma and IL2, IL10, IL6, TGF-β, KLRC1, TNF, BTP, SNCA, SOD1, BLNK, PTGS2 and INF γ expression in the PMNCF.

Results

11 patients did not exhibit an increase in their BFI scores and served as controls, whereas 32 patients exhibited an increase in their BFI scores compared with the baseline scores. From the biomarkers we evaluated in the PMNCF, the only one significantly associated with fatigue was TGF-β (p = 0.0343), while there was a trend towards significance with KLRC1 (p = 0.0627). We observed no evidence of significant associations of any plasma biomarkers with the development of fatigue. However when we analyzed patients with more severe fatigue, plasma IL1-RA levels correlated directly with higher fatigue scores (p = 0.0136).

Conclusions

We conclude that fatigue induced by chemotherapy in BC patients is associated with changes in IL1-ra plasma levels and in TGF-β lymphocyte expression. Its mechanism may be different than that observed in long-term BC survivors or that induced by radiation therapy.

Trial registration

NCT02041364 [ClinicalTrials.gov]

Fighting insomnia and battling lethargy: the yin and yang of palliative care

There is an interdependent relationship between insomnia and fatigue in the medical literature, but both remain distinct entities. Insomnia entails problematic sleep initiation, maintenance, or restoration with an accompanying decrease in perceived daytime function. Lethargy is a symptom that has a wide differential diagnosis that heavily overlaps with cancer-related fatigue; however, insomnia may contribute to worsened fatigue and lethargy in cancer patients. Insomnia is a major risk factor for mood disturbances such as depression, which may also contribute to lethargy in this at-risk population. The pathophysiology of fatigue and insomnia is discussed in this review, including their differential diagnoses as well as the emerging understanding of the roles of neurotransmitters, branched-chain amino acids, and inflammatory cytokines. Treatment approaches for insomnia and fatigue are also discussed and reviewed, including the role of hypnotics, psychotropics, hormonal agents, and alternative therapies.

Cancer-related fatigue--mechanisms, risk factors, and treatments

Fatigue is one of the most common adverse effects of cancer that might persist for years after treatment completion in otherwise healthy survivors. Cancer-related fatigue causes disruption in all aspects of quality of life and might be a risk factor of reduced survival. The prevalence and course of fatigue in patients with cancer have been well characterized and there is growing understanding of the underlying biological mechanisms. Inflammation seems to have a key role in fatigue before, during, and after cancer-treatment. However, there is a considerable variability in the presentation of cancer-related fatigue, much of which is not explained by disease-related or treatment-related characteristics, suggesting that host factors might be important in the development and persistence of this symptom. Indeed, longitudinal studies have identified genetic, biological, psychosocial, and behavioural risk factors associated with cancer-related fatigue. Although no current gold-standard treatment for fatigue is available, a variety of intervention approaches have shown beneficial effects in randomized controlled trials, including physical activity, psychosocial, mind-body, and pharmacological treatments. This Review describes the mechanisms, risk factors, and possible interventions for cancer-related fatigue, focusing on recent longitudinal studies and randomized trials that have targeted fatigued patients.

Local and systemic pathogenesis and consequences of regimen-induced inflammatory responses in patients with head and neck cancer receiving chemoradiation

Treatment-related toxicities are common among patients with head and neck cancer, leading to poor clinical outcomes, reduced quality of life, and increased use of healthcare resources. Over the last decade, much has been learned about the pathogenesis of cancer regimen-related toxicities. Historically, toxicities were separated into those associated with tissue injury and those with behavioural or systemic changes. However, it is now clear that tissue-specific damage such as mucositis, dermatitis, or fibrosis is no longer the sole consequence of direct clonogenic cell death, and a relationship between toxicities that results in their presentation as symptom clusters has been documented and attributed to a common underlying pathobiology. In addition, the finding that patients commonly develop toxicities representing tissue injury outside radiation fields and side effects such as fatigue or cognitive dysfunction suggests the generation of systemic as well as local mediators. As a consequence, it might be appropriate to consider toxicity syndromes, rather than the traditional approach, in which each side effect was considered as an autonomous entity. In this paper, we propose a biologically based explanation which forms the basis for the diverse constellation of toxicities seen in response to current regimens used to treat cancers of the head and neck.

Chronic restraint stress upregulates erythropoiesis through glucocorticoid stimulation

In response to elevated glucocorticoid levels, erythroid progenitors rapidly expand to produce large numbers of young erythrocytes. Previous work demonstrates hematopoietic changes in rodents exposed to various physical and psychological stressors, however, the effects of chronic psychological stress on erythropoiesis has not be delineated. We employed laboratory, clinical and genomic analyses of a murine model of chronic restraint stress (RST) to examine the influence of psychological stress on erythropoiesis. Mice exposed to RST demonstrated markers of early erythroid expansion involving the glucocorticoid receptor. In addition, these RST-exposed mice had increased numbers of circulating reticulocytes and increased erythropoiesis in primary and secondary erythroid tissues. Mice also showed increases in erythroid progenitor populations and elevated expression of the erythroid transcription factor KLF1 in these cells. Together this work reports some of the first evidence of psychological stress affecting erythroid homeostasis through glucocorticoid stimulation.

Recommendations for high-priority research on cancer-related fatigue in children and adults

Over the past decades, some scientific progress has been made in understanding and treating cancer-related fatigue (CRF). However, three major problems have limited further progress: lack of agreement about measurement, inadequate understanding of the underlying biology, and problems in the conduct of clinical trials for CRF. This commentary reports the recommendations of a National Cancer Institute Clinical Trials Planning Meeting and an ongoing National Cancer Institute working group to address these problems so that high-priority research and clinical trials can be conducted to advance the science of CRF and its treatment. Recommendations to address measurement issues included revising the current case definition to reflect more rigorous criteria, adopting the Patient Reported Outcomes Measurement Information System fatigue scales as standard measures of CRF, and linking legacy measures to the scales. With regard to the biology of CRF, the group identified the need for longitudinal research to examine biobehavioral mechanisms underlying CRF and testing mechanistic hypotheses within the context of intervention research. To address clinical trial issues, recommendations included using only placebo-controlled trial designs. setting eligibility to minimize sample heterogeneity or enable subgroup analysis, establishing a CRF severity threshold for participation in clinical trials, conducting dissemination trials of efficacious interventions (such as exercise), and combining nonpharmacologic and pharmacologic interventions to exploit the potential synergy between these approaches. Accomplishing these goals has the potential to advance the science of CRF and improve the clinical management of this troubling symptom.

A possible genetic association with chronic fatigue in primary Sjögren's syndrome: a candidate gene study

Fatigue is prevalent and disabling in primary Sjögren's syndrome (pSS). Results from studies in chronic fatigue syndrome (CFS) indicate that genetic variation may influence fatigue. The aim of this study was to investigate single nucleotide polymorphism (SNP) variations in pSS patients with high and low fatigue. A panel of 85 SNPs in 12 genes was selected based on previous studies in CFS. A total of 207 pSS patients and 376 healthy controls were genotyped. One-hundred and ninety-three patients and 70 SNPs in 11 genes were available for analysis after quality control. Patients were dichotomized based on fatigue visual analogue scale (VAS) scores, with VAS <50 denominated "low fatigue" (n = 53) and VAS ≥50 denominated "high fatigue" (n = 140). We detected signals of association with pSS for one SNP in SLC25A40 (unadjusted p = 0.007) and two SNPs in PKN1 (both p = 0.03) in our pSS case versus control analysis. The association with SLC25A40 was stronger when only pSS high fatigue patients were analysed versus controls (p = 0.002). One SNP in PKN1 displayed an association in the case-only analysis of pSS high fatigue versus pSS low fatigue (p = 0.005). This candidate gene study in pSS did reveal a trend for associations between genetic variation in candidate genes and fatigue. The results will need to be replicated. More research on genetic associations with fatigue is warranted, and future trials should include larger cohorts and multicentre collaborations with sharing of genetic material to increase the statistical power.

Nervous system regulation of the cancer genome

Genomics-based analyses have provided deep insight into the basic biology of cancer and are now clarifying the molecular pathways by which psychological and social factors can regulate tumor cell gene expression and genome evolution. This review summarizes basic and clinical research on neural and endocrine regulation of the cancer genome and its interactions with the surrounding tumor microenvironment, including the specific types of genes subject to neural and endocrine regulation, the signal transduction pathways that mediate such effects, and therapeutic approaches that might be deployed to mitigate their impact. Beta-adrenergic signaling from the sympathetic nervous system has been found to up-regulated a diverse array of genes that contribute to tumor progression and metastasis, whereas glucocorticoid-regulated genes can inhibit DNA repair and promote cancer cell survival and resistance to chemotherapy. Relationships between socio-environmental risk factors, neural and endocrine signaling to the tumor microenvironment, and transcriptional responses by cancer cells and surrounding stromal cells are providing new mechanistic insights into the social epidemiology of cancer, new therapeutic approaches for protecting the health of cancer patients, and new molecular biomarkers for assessing the impact of behavioral and pharmacologic interventions.

Inflammation and cancer-related fatigue: mechanisms, contributing factors, and treatment implications

Fatigue is one of the most common and distressing side effects of cancer and its treatment, and may persist for years after treatment completion in otherwise healthy survivors. Guided by basic research on neuro-immune interactions, a growing body of research has examined the hypothesis that cancer-related fatigue is driven by activation of the pro-inflammatory cytokine network. In this review, we examine the current state of the evidence linking inflammation and cancer-related fatigue, drawing from recent human research and from experimental animal models probing effects of cancer and cancer treatment on inflammation and fatigue. In addition, we consider two key questions that are currently driving research in this area: what are the neural mechanisms of fatigue, and what are the biological and psychological factors that influence the onset and/or persistence of inflammation and fatigue in cancer patients and survivors? Identification of the mechanisms driving cancer-related fatigue and associated risk factors will facilitate the development of targeted interventions for vulnerable patients.

A systematic review of the association between immunogenomic markers and cancer-related fatigue

Fatigue, which is one of the most commonly reported symptoms in cancer, can negatively impact the functional status and the health-related quality of life of individuals. This paper systematically reviews 34 studies to determine patterns of associations between immunogenomic markers and levels of cancer-related fatigue (CRF). Findings from the longitudinal studies revealed that elevated fatigue symptoms especially of women with early stages of breast cancer were associated with high levels of neutrophil/monocyte, IL-1ra, and IL-6 during radiation therapy; high levels of CD4+, IL-1β, and IL-6 with stressing stimuli; high levels of IL-1β during chemotherapy; low NK cell levels after chemotherapy; and presence of homozygous IL-6 and TNF alleles. In the cross-sectional studies, associations between levels of fatigue and immune/inflammatory markers were not consistently found, especially when covariates such as BMI, ethnicity, menopausal status, and educational level were controlled in the statistical analyses. However, a number of genomic markers were observed to be elevated mostly in fatigued breast cancer survivors in the cross-sectional studies. Gaps in knowledge and recommendations for future research are discussed.

Fatigue after treatment in breast cancer survivors: prevalence, determinants and impact on health-related quality of life

PURPOSE

Fatigue is a phenomenon that may persist for years after completion of adjuvant therapy, and is one of the most frequent symptoms associated with breast cancer survivors. The purposes of this study were to investigate the occurrence of fatigue in disease-free breast cancer survivors after treatment, to identify variables associated with fatigue, and to evaluate the impact of fatigue on health-related quality of life.

METHODS

A cross-sectional study was conducted on 202 consecutive women diagnosed with in-situ to Stage III breast cancer attending in outpatient facilities of two large hospitals, one year or more after diagnosis. They completed the Piper Fatigue Scale-Revised and the European Organization for Research and Treatment of Cancer QLQ-C30. Multiple logistic regression models were used to identify predictive factors associated with fatigue. EORTC QLQC-30 scores for fatigued survivors were compared to non-fatigued survivors.

RESULTS

The prevalence of fatigue reported by the breast cancer survivors was 37.6%. Multiple logistic regression analysis revealed that predictive factors for fatigue included younger age (odds ratio [OR]=2.23, 95% confidence interval [CI]=1.11-4.45, p = 0.024); presence of pain (OR = 3.87, 95% CI = 1.88-7.98, p = 0.000); dyspnea (OR = 3.72, 95% CI = 1.46-9.50, p = 0.006); insomnia (OR = 2.40, 95% CI = 1.19-4.86, p = 0.015); and nausea and vomiting (OR = 12.25, 95% CI = 1.18-126.75, p = 0.036). Fatigued women had poorer health-related quality of life than non-fatigued women in all domains.

CONCLUSION

Our results suggest that many disease-free breast cancer survivors after treatment experienced fatigue that compromises their health-related quality of life.

Fatigued breast cancer survivors and gene polymorphisms in the inflammatory pathway

Chronic fatigue (CF) in breast cancer survivors (BCSs) has been associated with increased serum C-reactive protein-levels (CRP), pro-inflammatory cytokines and cytokine gene single nucleotide polymorphisms (SNPs). Still, there are few studies on these topics, and due to small study-cohorts the possibility to adjust for other conditions related to inflammatory processes, e.g. depression, has been limited. In 302 BCSs, examined approximately four years after treatment for breast cancer stage II/III, data on high sensitivity (hs)CRP, leukocytes and mRNA interleukin (IL)1β and IL6R expression, depression and chronic fatigue were available. Three years thereafter, 236 BCSs were re-examined. The associations between fatigue and SNPs in inflammation-related genes; IL1β (rs16944), IL6 (rs1800795), IL6receptor (rs4129267, rs4845617, rs2228145), CRP (rs2794521, rs3091244) were investigated, together with the relations between SNPs in IL6R,IL1β and CRP genes and mRNA blood expression levels of IL6R and IL1β and serum hsCRP-levels, respectively. All analyses were repeated after exclusion of depressed individuals and separating BCSs with persistent fatigue from never-fatigued individuals. Even after exclusion of depressed individuals neither the SNPs nor the mRNA IL1β and IL6R expression levels were associated with chronic or persistent fatigue. In the subset of persistent fatigued and never-fatigued individuals the CRP SNP (rs3091244) was associated with hsCRP level (p=0.02). IL1β and IL6R mRNA expression levels were not related to the IL1β and IL6R genotypes. In a large cohort of BCSs the investigated SNPs in inflammation-related genes were not associated with fatigue, though subset analyses indicated an association between the CRP SNP (rs3091244) and serum hsCRP.

Higher levels of fatigue are associated with higher CRP levels in disease-free breast cancer survivors

OBJECTIVE

To investigate the associations between level of fatigue and various potential inflammatory biomarkers for fatigue after multivariate adjustments for possible confounders in a sample of 299 disease-free survivors of breast cancer (BCSs) at a mean of 4 years post diagnosis.

METHODS

Medical record data were used for cancer-related information, and a follow-up mailed survey collected data on fatigue, depression, anxiety and insomnia symptoms as well as information on demographics, physical health, medication and lifestyle. Blood samples drawn at an outpatient examination were analyzed for leukocyte count, high sensitivity C-reactive Protein (CRP), interleukin 1 receptor antagonist (IL-1ra), interleukin-6 (IL-6), soluble tumor necrosis factor receptor type 1 (sTNF-R1) and neopterin.

RESULTS

Fatigue levels were significantly and positively associated with hsCRP (p<.001) and leukocyte count (p=.018), but not with levels of IL-1ra, IL-6, sTNF-R1 or neopterin in unadjusted analyses. Only hsCRP remained significantly associated with fatigue levels in the fully adjusted models (p=.020). Depression and self-rated health also remained independently associated with fatigue; however these variables were not significantly associated with hsCRP in multivariate analyses.

CONCLUSION

In general, and after adjustment for potential confounders, our hypotheses of positive associations between fatigue and several inflammatory markers were not confirmed. However, a small but independent association between level of fatigue and hsCRP was observed and supports the hypothesis that low-grade inflammation could play a role in the pathogenesis of fatigue in BCSs.

Fatigue and gene expression in human leukocytes: increased NF-κB and decreased glucocorticoid signaling in breast cancer survivors with persistent fatigue

Fatigue is highly prevalent in the general population and is one of the most common side effects of cancer treatment. There is growing evidence that pro-inflammatory cytokines play a role in cancer-related fatigue, although the molecular mechanisms for chronic inflammation and fatigue have not been determined. The current study utilized genome-wide expression microarrays to identify differences in gene expression and associated alterations in transcriptional activity in leukocytes from breast cancer survivors with persistent fatigue (n=11) and non-fatigued controls (n=10). We focused on transcription of inflammation-related genes, particularly those responsive to the pro-inflammatory NF-κB transcription control pathway. Further, given the role of glucocorticoids as key regulators of inflammatory processes, we examined transcription of glucocorticoid-responsive genes indicative of potential glucocorticoid receptor (GR) desensitization. Plasma levels of cortisol were also assessed. Consistent with hypotheses, results showed increased expression of transcripts with response elements for NF-κB, and reduced expression of transcripts with response elements for glucocorticoids (p<.05) in fatigued breast cancer survivors. No differences in plasma levels of cortisol were observed. These data indicate that increased activity of pro-inflammatory transcription factors may contribute to persistent cancer-related fatigue and provide insight into potential mechanisms for tonic increases in NF-κB activity, specifically decreased expression of GR anti-inflammatory transcription factors.

Predictors and course of chronic fatigue in long-term breast cancer survivors

BACKGROUND

The course of fatigue in long-term breast cancer survivors (BCSs) is unknown. The current study examined chronic fatigue (CF) cross-sectionally and longitudinally in relapse-free women up to 10 years after multimodal treatment for BC stage II/III. The prevalence of persistent fatigue (PF: having CF at two assessments separated by >2 years) and its predictors were also investigated.

METHODS

Data from questionnaires (including the Fatigue Questionnaire and questions regarding socio-demographics and physical symptoms) were collected twice from 249 BCSs: 2.5-7 years post-BC diagnosis (T1) and 2.5-3 years thereafter (T2). A physical examination including blood sampling was performed at T1.

RESULTS

CF was diagnosed in 33% of the women at T1 and in 39% at T2, including 57 (23%) subjects with PF. Current psychological distress, treatment-area related discomfort and high body mass index (BMI) were associated with CF at T1 and predicted PF. Increased leukocyte count also predicted PF. Treatment for mental problems prior to the BC, increased hsCRP-level and respiratory symptoms were associated with CF at T1 but did not predict PF.

CONCLUSIONS

Women may experience fatigue up to 10 years after multimodal BC treatment, with about one third having CF and about one fourth having PF.

IMPLICATIONS FOR CANCER SURVIVORS

During follow-up, BCSs and their doctors should maximize their efforts to reduce psychological distress, overweight and pain within the BC-treated area, all linked to the development of persistent fatigue.

NOTCH2 in breast cancer: association of SNP rs11249433 with gene expression in ER-positive breast tumors without TP53 mutations

Background

A recent genome-wide association study (GWAS) has identified a single nucleotide polymorphism (SNP) rs11249433 in the 1p11.2 region as a novel genetic risk factor for breast cancer, and this association was stronger in patients with estrogen receptor (ER)⁺ versus ER^- cancer.

Results

We found association between SNP rs11249433 and expression of the NOTCH2 gene located in the 1p11.2 region. Examined in 180 breast tumors, the expression of NOTCH2 was found to be lowest in tumors with TP53 mutations and highest in TP53 wild-type/ER⁺ tumors (p = 0.0059). In the latter group, the NOTCH2 expression was particularly increased in carriers of the risk genotypes (AG/GG) of rs11249433 when compared to the non-risk AA genotype (p = 0.0062). Similar association between NOTCH2 expression and rs11249433 was observed in 60 samples of purified monocytes from healthy controls (p = 0.015), but not in total blood samples from 302 breast cancer patients and 76 normal breast tissue samples. We also identified the first possible dominant-negative form of NOTCH2, a truncated version of NOTCH2 consisting of only the extracellular domain.

Conclusion

This is the first study to show that the expression of NOTCH2 differs in subgroups of breast tumors and by genotypes of the breast cancer-associated SNP rs11249433. The NOTCH pathway has key functions in stem cell differentiation of ER⁺ luminal cells in the breast. Therefore, increased expression of NOTCH2 in carriers of rs11249433 may promote development of ER⁺ luminal tumors. Further studies are needed to investigate possible mechanisms of regulation of NOTCH2 expression by rs11249433 and the role of NOTCH2 splicing forms in breast cancer development.

Review: the use of proteomics as a research methodology for studying cancer-related fatigue: a review

There is an increasing emphasis on using translational research to examine mechanisms and increase our understanding of disease. Translational research involves the use of basic science techniques to generate new treatments for use in a clinical setting - the so called 'bench to bedside' approach. This methodology could be used to enhance our understanding of complex symptoms such as cancer-related fatigue. This review will examine specifically the potential role of the science of protein structure and function (proteomics) as a technique to improve our knowledge in this area. This will include an explanation of the specific methods used in this research in order to increase our understanding of the mechanisms of cancer-related fatigue and discuss potential directions for future research with the development of more targeted therapies.