Euflammation Attenuates Central and Peripheral Inflammation and Cognitive Consequences of an Immune Challenge after Tumor Development

The role of microglia in 67NR mammary tumor-induced suppression of brain responses to immune challenges in female mice

It is poorly understood how solid peripheral tumors affect brain neuroimmune responses despite the various brain-mediated side effects and higher rates of infection reported in cancer patients. We hypothesized that chronic low-grade peripheral tumor-induced inflammation conditions microglia to drive suppression of neuroinflammatory responses to a subsequent peripheral immune challenge. Here, Balb/c murine mammary tumors attenuated the microglial inflammatory gene expression responses to lipopolysaccharide (LPS) and live Escherichia coli (E. coli) challenges and the fatigue response to an E. coli infection. In contrast, the inflammatory gene expression in response to LPS or a toll-like receptor 2 agonist of Percoll-enriched primary microglia cultures was comparable between tumor-bearing and -free mice, as were the neuroinflammatory and sickness behavioral responses to an intracerebroventricular interleukin (IL)-1β injection. These data led to the hypothesis that Balb/c mammary tumors blunt the neuroinflammatory responses to an immune challenge via a mechanism involving tumor suppression of the peripheral humoral response. Balb/c mammary tumors modestly attenuated select circulating cytokine responses to LPS and E. coli challenges. Further, a second mammary tumor/mouse strain model (E0771 tumors in C57Bl/6 mice) displayed mildly elevated inflammatory responses to an immune challenge. Taken together, these data indicate that tumor-induced suppression of neuroinflammation and sickness behaviors may be driven by a blunted microglial phenotype, partly because of an attenuated peripheral signal to the brain, which may contribute to infection responses and behavioral side effects reported in cancer patients. Finally, these neuroimmune effects likely vary based on tumor type and/or host immune phenotype.

Peripheral inflammation and neurocognitive impairment: correlations, underlying mechanisms, and therapeutic implications

Cognitive impairments, such as learning and memory deficits, may occur in susceptible populations including the elderly and patients who are chronically ill or have experienced stressful events, including surgery, infection, and trauma. Accumulating lines of evidence suggested that peripheral inflammation featured by the recruitment of peripheral immune cells and the release of pro-inflammatory cytokines may be activated during aging and these conditions, participating in peripheral immune system-brain communication. Lots of progress has been achieved in deciphering the core bridging mechanism connecting peripheral inflammation and cognitive impairments, which may be helpful in developing early diagnosis, prognosis evaluation, and prevention methods based on peripheral blood circulation system sampling and intervention. In this review, we summarized the evolving evidence on the prevalence of peripheral inflammation-associated neurocognitive impairments and discussed the research advances in the underlying mechanisms. We also highlighted the prevention and treatment strategies against peripheral inflammation-associated cognitive dysfunction.

Risk of cognition alteration and emotional frailty via circulating transcriptome in treatment naïve head and neck squamous cell cancer patients

Background

There is a dearth of research examining the association between differential expression (DE) of genetic transcritome associated with cognition alteration (CA) and emotional frailty (EF) in treatment naïve head and neck squamous cell carcinoma (HNSCC) patients. The present study was undertaken to identify the DE of mRNA of CA-EF in HNSCC tumor and correlate with clinical and other known genetic factors that promote oncogenesis as well as CA-EF.

Material and methods

Using Genome-Wide Association Studies, putative genes associated with CA-EF(Prixie Fixie score ≥0.10) were identified. The DE of the mRNA of the thus selected genes were obtained from The CANCER GENOME ATLAS - HNSCC patients along with clinical details. The DE of mRNA pertaining to known factors such as inflammation, serotonergic and dopaminergic functions as well as clinical parameters were studied for association with the risk of DE of CA-EF. Appropriate statistics were performed and P ≤ 0.05 was taken as significant.

Results

A total of 520 HNSCC patients formed study group. There were 77 (14.81%) patients at risk for CD, 41 (7.9%) for CI and 113 (21.73%) for EF risk. In all, 103 (19.81%) HNSCC patients of this cohort had DE of mRNA of genes associated with CA. Inflammation, circadian genes, mTOR pathway, invasion and metastasis set of genes had a significant association with the risk of DE of CA-EF.

Discussion

Transcriptome's have been postulated to mediate CA-EF by targeted action on human brain. Differential Expression of putative genes associated with CA-EF have been demonstrated in HNSCC tumor. These DE could predispose the patients to CA-EF by the action of gene-environmental as well as psycho-social constructs. As CA-EF could adversely influence the treatment and alter the quality of life among survivors, screening for CA-EF at HNSCC presentation becomes imperative.

Tumor resection ameliorates tumor-induced suppression of neuroinflammatory and behavioral responses to an immune challenge in a cancer survivor model

Breast cancer survivors display altered inflammatory responses to immune challenges relative to cancer-naive controls likely due to previous cancer treatments, stress associated with cancer, and/or tumor physiology. Proper inflammatory responses are necessary for adaptive sickness behaviors (e.g., fatigue, anorexia, and fever) and neuroinflammatory pathways are also implicated in mental health disturbances (e.g., cognitive impairment, depression) suffered by cancer patients and survivors. Rodent cancer models indicate that tumors are sufficient to exacerbate neuroinflammatory responses after an immune challenge, however primary tumors are not usually present in cancer survivors, and the behavioral consequences of these brain changes remain understudied. Therefore, we tested the extent to which mammary tumor resection attenuates tumor-induced neuroinflammation and sickness behavior following an immune challenge (i.p. lipopolysaccharide [LPS] injection) in mice. Tnf-α, Il-1β, and Il-6 mRNA decreased in multiple brain regions of LPS-treated tumor-bearing mice relative to LPS-treated controls; tumor resection attenuated these effects in some cases (but not Tnf-α). Tumors also attenuated sickness behaviors (hypothermia and lethargy) compared to LPS-treated controls. Tumor resection reversed these behavioral consequences, although basal body temperature remained elevated, comparable to tumor-bearing mice. Thus, tumors significantly modulate neuroinflammatory pathways with functional consequences and tumor resection mitigates most, but not all, of these changes.

Low dose aspirin blocks breast cancer-induced cognitive impairment in mice

Cancer patients with non-central nervous system tumors often suffer from cognitive impairment. While chemotherapy has long been attributed as the cause of these memory, learning and concentration difficulties, we recently observed cognitive impairment in cancer patients prior to treatment. This suggests the cancer alone may be sufficient to induce cognitive impairment, however the mechanisms are unknown. Here, we show that we can experimentally replicate the clinical phenomenon of cancer-associated cognitive impairment and we identify inflammation as a causal mechanism. We demonstrate that a peripheral tumor is sufficient to induce memory loss. Using an othotopic mouse model of breast cancer, we found that mice with 4T1.2 or EO771 mammary tumors had significantly poorer memory than mice without tumors. Memory impairment was independent of cancer-induced sickness behavior, which was only observed during the later stage of cancer progression in mice with high metastatic burden. Tumor-secreted factors were sufficient to induce memory impairment and pro-inflammatory cytokines were elevated in the plasma of tumor-bearing mice. Oral treatment with low-dose aspirin completely blocked tumor-induced memory impairment without affecting tumor-induced sickness or tumor growth, demonstrating a causal role for inflammation in cognitive impairment. These findings suggest that anti-inflammatories may be a safe and readily translatable strategy that could be used to prevent cancer-associated cognitive impairment in patients.

Inflammation markers and cognitive performance in breast cancer survivors 20 years after completion of chemotherapy: a cohort study

Background

Inflammation is an important candidate mechanism underlying cancer and cancer treatment-related cognitive impairment. We investigated levels of blood cell–based inflammatory markers in breast cancer survivors on average 20 years after chemotherapy and explored the relation between these markers and global cognitive performance.

Methods

One hundred sixty-six breast cancer survivors who received post-surgical radiotherapy and six cycles of adjuvant cyclophosphamide, methotrexate, and fluorouracil (CMF) chemotherapy on average 20 years before enrollment were compared with 1344 cancer-free women from a population-based sample (50–80 years old). Breast cancer survivors were excluded if they used adjuvant hormonal therapy or if they developed relapse, metastasis, or second primary malignancies. Systemic inflammation status was assessed by the granulocyte-to-lymphocyte ratio (GLR), platelet-to-lymphocyte ratio (PLR), and systemic immune-inflammation index (SII). Cognitive performance was assessed using an extensive neuropsychological test battery from which the general cognitive factor was derived to evaluate global cognitive performance. We examined the association between cancer, the general cognitive factor, and inflammatory markers using linear regression models.

Results

Breast cancer survivors had a lower general cognitive factor than non-exposed participants from the comparator group (mean difference = −0.21; 95% confidence interval (CI) −0.35 to −0.06). Inflammatory markers were higher in cancer survivors compared with non-exposed participants (mean difference for log(GLR) = 0.31; 95% CI 0.24 to 0.37, log(PLR) = 0.14; 95% CI 0.09 to 0.19, log(SII) = 0.31; 95% CI 0.24 to 0.39). The association between higher levels of inflammatory markers and lower general cognitive factor was statistically significant in cancer survivors but not among non-exposed participants. We found a group-by-inflammatory marker interaction; cancer survivors showed additional lower general cognitive factor per standard deviation increase in inflammatory markers (P for interaction for GLR = 0.038, PLR = 0.003, and SII = 0.033).

Conclusions

This is the first study to show that (1) cancer survivors have increased levels of inflammation on average 20 years after treatment and (2) these inflammatory levels are associated with lower cognitive performance. Although this association needs verification by a prospective study to determine causality, our findings can stimulate research on the role of inflammation in long-term cognitive problems and possibilities to diminish such problems.