Peripheral tumors induce depressive-like behaviors and cytokine production and alter hypothalamic-pituitary-adrenal axis regulation.

A strong and positive correlation exists between chronic disease and affective disorders, but the biological mechanisms underlying this relationship are not known. Here we show that rats with mammary cancer exhibit depression- and anxiety-like behaviors in the absence of overt sickness behaviors. The production of proinflammatory cytokines, known to induce depressive-like behaviors, was elevated in the periphery and in the hippocampus of rats with tumors compared with controls. In tumor-bearing rats, circulating corticosterone, which inhibits cytokine signaling, was suppressed following a stressor, and gene expression of hippocampal glucocorticoid receptors was elevated. The results establish that tumors alone are sufficient to trigger changes in emotional behaviors. Dampened glucocorticoid responses to stressors may exacerbate the deleterious effects of tumor-induced cytokines on affective states.

Mammary tumors induce select cognitive impairments.

Cancer, in addition to many other chronic diseases, is associated with serious and problematic behavioral symptoms, including cognitive impairments. In humans, various factors likely contribute to cancer-associated cognitive deficits including disease awareness and chemotherapy; however, the endogenous biological factors arising from tumor development may also play a causal role. In the present study, rats with mammary tumors exhibited impaired spatial reference memory on a radial arm maze and amnesia for familiar objects in an object recognition memory test. In contrast, their performance in the Morris water maze and in fear conditioning tests was comparable to that of controls. These select cognitive impairments were accompanied by elevations in hippocampal interleukin-1beta mRNA expression, but were not associated with decreases in hippocampal brain-derived neurotrophic factor gene expression. Together the results indicate that peripheral tumors alone are sufficient to induce increases in hippocampal cytokine expression and select deficits in hippocampal-dependent memory tasks.

Common variation at BARD1 results in the expression of an oncogenic isoform that influences neuroblastoma susceptibility and oncogenicity.

The mechanisms underlying genetic susceptibility at loci discovered by genome-wide association study (GWAS) approaches in human cancer remain largely undefined. In this study, we characterized the high-risk neuroblastoma association at the BRCA1-related locus, BARD1, showing that disease-associated variations correlate with increased expression of the oncogenically activated isoform, BARD1ß. In neuroblastoma cells, silencing of BARD1ß showed genotype-specific cytotoxic effects, including decreased substrate-adherence, anchorage-independence, and foci growth. In established murine fibroblasts, overexpression of BARD1ß was sufficient for neoplastic transformation. BARD1ß stabilized the Aurora family of kinases in neuroblastoma cells, suggesting both a mechanism for the observed effect and a potential therapeutic strategy. Together, our findings identify BARD1ß as an oncogenic driver of high-risk neuroblastoma tumorigenesis, and more generally, they illustrate how robust GWAS signals offer genomic landmarks to identify molecular mechanisms involved in both tumor initiation and malignant progression. The interaction of BARD1ß with the Aurora family of kinases lends strong support to the ongoing work to develop Aurora kinase inhibitors for clinically aggressive neuroblastoma.