Cytochrome b561 regulates iron metabolism by activating the Akt/mTOR pathway to promote Breast Cancer Cells proliferation

Breast cancer (BC) is the leading cause of cancer-related mortality in women, necessitating the development of novel therapeutic targets. While cytochrome b561 (CYB561) expression is associated with poor prognosis in BC, the precise role of CYB561 in BC and its potential mechanisms remain unclear. In the present study, we found that CYB561 plays an essential role in BC growth. CYB561 expression was up-regulated in surgically resected cancerous tissues and in six BC cell lines. Lentivirus-mediated CYB561 knockdown in BC cells significantly reduced their proliferation, migration, and invasiveness. CYB561 participates in the regulation of iron metabolism in BC. CYB561 knockdown reduced total iron content, increased ferrous iron content, and down-regulated the expression of proteins associated with iron metabolism (transferrin receptor 1, divalent metal transporter 1, and ferritin heavy chain 1). Conversely, up-regulation of CYB561 through co-incubation with exogenous iron (ferric ammonium citrate) produced contrary outcomes. Additionally, CYB561 activated the protein kinase B/mammalian target of rapamycin (Akt/mTOR) signaling pathway in BC cells. Down-regulation of CYB561 expression inhibited the Akt/mTOR signaling pathway activity. The application of an mTOR agonist (MHY1485) rescued this negative effect, as well as the inhibitory effect of CYB561 knockdown on cell proliferation. Importantly, the dual mTOR inhibitor MLN0128 (50 nM, 48 h) down-regulated CYB561 expression and the iron metabolism-related proteins transferrin receptor, divalent metal transporter 1, and ferritin heavy chain 1, whereas the mTOR agonist MHY1485 rescued the down-regulation of CYB561 knockdown on iron metabolism-related proteins. We conclude that CYB561 promotes the proliferation of BC cells by regulating iron metabolism through the activation of the Akt/mTOR signaling pathway.

Expression and clinical prognostic value of CYB561 in breast cancer

PURPOSE

The expression of cytochrome B561 (CYB561) and its role in breast cancer (BC) prognosis remain unclear. We analyzed the differential expression and prognostic value of CYB561 using online databases and a clinical cohort through bioinformatics and immunohistochemistry.

METHODS

The differential expression of CYB561 and its association with BC were analyzed using the tumor immune estimation resource (TIMER), gene expression profiling interaction analysis2 (GEPIA2), Human Protein Atlas, Cancer Cell Line Encyclopedia, and Kaplan-Meier Plotter website. Important pathways of CYB561 enrichment were explored using gene set enrichment analysis. Immunohistochemistry detected CYB561 expression in normal breast, breast hyperplasia, ductal carcinoma in situ (DCIS), para-cancer, and invasive BC groups. Association between CYB561 expression and BC prognosis was analyzed using Kaplan-Meier and Cox regression analyses.

RESULTS

CYB561 mRNA expression was higher in GEPIA and TIMER BC patients than in para-cancer tissues. CYB561 was expressed in the glandular epithelium and myoepithelium, with positive localization in the cytoplasm and cell membrane. CYB561 protein expression significantly differed among the groups. CYB561 expression was correlated with ERBB2/HER2 and infiltrating CD4+ T cells in GEPIA and TIMER BC patients and associated with HER2 status, histological grade, and molecular subtypes in the clinical cohort but not related to tumor-infiltrating lymphocytes. CYB561 mRNA overexpression predicted reduced recurrence-free survival and overall survival in BC. Patients with CYB561 expression had significantly reduced overall survival and increased risk of death.

CONCLUSION

CYB561 can serve as an effective clinical prognostic biomarker for BC.

Human heart rate: heritability of resting and stress values in twin pairs, and influence of genetic variation in the adrenergic pathway at a microribonucleic acid (microrna) motif in the 3'-UTR of cytochrome b561 [corrected]

OBJECTIVES

The goal of this study was to understand the role of genetic variation in the catecholamine biosynthetic pathway for control of human heart rate (HR).

BACKGROUND

Human HR is an integrated cardiovascular trait predictive of morbidity and survival. Because the autonomic pathway exerts rapid control over the heart, we probed the role of heredity in the control of HR, focusing on a component of the autonomic sympathetic pathway already predictive of outflow responses: cytochrome b561 (CYB561), the electron shuttle in catecholamine vesicle membranes for transmitter biosynthesis.

METHODS

We studied hereditary control of HR with the twin pair design, at rest and during environmental (cold) stress. Single nucleotide polymorphism disruption of a microribonucleic acid (microRNA) recognition motif in the human CYB561 3'-UTR was identified computationally, and its differential effect on gene expression was demonstrated in a transfected luciferase reporter/3'-UTR variant. We exposed stem cell-derived human embryoid bodies to the microRNA mimic or antagomir oligonucleotides, and we observed the effects on contraction rate in proto-hearts.

RESULTS

Substantial heritability (h(2)) was demonstrated by using twin pair variance components for both basal/resting HR (h(2) 50.9 ± 6.4% of trait variation, p = 2.47 × 10(-10)) and stress-augmented HR (h(2) 55.1 ± 5.9%, p = 8.79 × 10(-13)), and the 2 HR traits shared genetic determination (genetic covariance ρG 0.747 ± 0.058, p = 2.85 × 10(-9)). CYB561 displayed 1 common genetic variant in the transcript region: A+1485G (rs3087776), in the 3'-UTR, 1485 bp downstream of the termination codon, in a conserved region, with the A-allele ancestral in primates. In a twin/sibling sample (n = 576), A+1485G influenced HR, both at rest (p = 0.010) and after environmental stress (p = 0.002), with the minor (A) allele displaying a recessive effect with lower HR. The effect of A+1485G on HR was extended by meta-analysis into 2 additional population samples (total n = 2,579), and the influence remained directionally consistent and significant (p = 0.007). A+1485G disrupted a microRNA (human microribonucleic acid-1294 [hsa-miR-1294]) recognition motif in the 3'-UTR, as demonstrated by a transfected luciferase reporter/human 3'-UTR variant system in 2 different neuronal/neuroendocrine cell types. The microRNA effect was further documented by cotransfection of an hsa-miR-1294 mimic, yielding an exaggerated decline in expression of the A-allele (better match) reporter (p = 4.3 × 10(-5)). Similar findings of differential 3'-UTR allelic susceptibility to hsa-miR-1294 were noted during expression of the full-length human CYB561 messenger ribonucleic acid with its cognate 3'-UTR. Finally, exposure of stem cell-derived human embryoid bodies to hsa-miR-1294 mimic or antagomir oligonucleotides yielded directionally opposite effects on contraction rate in proto-hearts.

CONCLUSIONS

HR is a substantially heritable trait, with genetic influence by variation in the adrenergic pathway, here shown for messenger ribonucleic acid translational control at the CYB561 step of transmitter formation. The results have implications for potentially modifiable autonomic pathways that influence this risk trait in the population.