title: Negative regulation of UCP2 by TGFβ signaling characterizes low and intermediate-grade primary breast cancer.
abstract: The histological manifestation of growth-regulating and differentiation-inducing signals in cancer cells is considered as a key component for clinical outcome prediction and commonly defined as tumor differentiation grade. However, the molecular and functional framework underlying this clinical parameter remains poorly understood. Our correlative data display a significant association (P>0.001) between mitochondrial uncoupling protein 2 (UCP2) and tumor grade in primary breast cancer (n=234). Through mechanistic analyses, we show a synergistic link between UCP2 and established cellular pathways in conferring grade-associated functional phenotypes. Here, the application of well to moderately differentiated primary tumor cell lines has enabled direct observation of SMAD recruitment to the UCP2 promoter underlying repression of gene transcription. In contrast, poorly differentiated tumor cells, known to be TGFβ resistant, displayed aberrant UCP2 regulation, and consequently, gene overexpression, which reduced mitochondrial calcium and facilitated the maintenance of mitochondrial membrane potential, thereby significantly decreasing oxidative stress and inhibiting cell death. Conversely, UCP2 silencing in such cells rapidly led to the induction of apoptosis and cell differentiation, concurrent with reduced cell survival and proliferation, confirming gene-specific effects. Demonstration of a biologically driven role for UCP2 dysregulation in promoting multiple characteristics of tumor aggressiveness strongly endorses assessment of gene expression at clinical presentation to augment therapeutic decision-making and improve patient outcome through personalized targeting approaches.
authors.affiliation: California Pacific Medical Center Research Institute, San Francisco, CA 94107, USA.
authors.forename: A
authors.initials: A
authors.lastname: Sayeed
authors.forename: Z
authors.initials: Z
authors.lastname: Meng
authors.forename: G
authors.initials: G
authors.lastname: Luciani
authors.forename: L-C
authors.initials: LC
authors.lastname: Chen
authors.forename: J L
authors.initials: JL
authors.lastname: Bennington
authors.forename: S H
authors.initials: SH
authors.lastname: Dairkee
mesh_terms: D017209:Apoptosis; D001943:Breast Neoplasms / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D009367:Neoplasm Staging; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction; D051901:Smad4 Protein / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D000071246:Uncoupling Protein 2
chemical_list: D007473:Ion Channels; D024101:Mitochondrial Proteins; D034741:RNA, Small Interfering; D051901:Smad4 Protein; D016212:Transforming Growth Factor beta; C000604389:UCP2 protein, human; D000071246:Uncoupling Protein 2; D002118:Calcium