Endocrine-resistance develops in ~ 40% of breast cancer patients after tamoxifen (TAM) therapy. Although microRNAs are dysregulated in breast cancer, their contribution to endocrine-resistance is not yet understood. Previous microarray analysis identified miR-29a and miR-29b-1 as repressed by TAM in MCF-7 endocrine-sensitive breast cancer cells but stimulated by TAM in LY2 endocrine-resistant breast cancer cells. Here we examined the mechanism for the differential regulation of these miRs by TAM in MCF-7 versus TAM-resistant LY2 and LCC9 breast cancer cells and the functional role of these microRNAs in these cells. Knockdown studies revealed that ERα is responsible for TAM regulation of miR-29b-1/a transcription. We also demonstrated that transient overexpression of miR-29b-1/a decreased MCF-7, LCC9, and LY2 proliferation and inhibited LY2 cell migration and colony formation but did not sensitize LCC9 or LY2 cells to TAM. Furthermore, TAM reduced DICER1 mRNA and protein in LY2 cells, a known target of miR-29. Supporting this observation, anti-miR-29b-1 or anti-miR-29a inhibited the suppression of DICER by 4-OHT. These results suggest miR-29b-1/a has tumor suppressor activity in TAM-resistant cells and does not appear to play a role in mediating TAM resistance.

Aberrant microRNA expression contributes to breast cancer progression and endocrine resistance. We reported that although tamoxifen stimulated miR-29b-1/a transcription in tamoxifen (TAM)-resistant breast cancer cells, ectopic expression of miR-29b-1/a did not drive TAM-resistance in MCF-7 breast cancer cells. However, miR-29b-1/a overexpression significantly repressed TAM-resistant LCC9 cell proliferation, suggesting that miR-29b-1/a is not mediating TAM resistance but acts as a tumor suppressor in TAM-resistant cells. The target genes mediating this tumor suppressor activity were unknown. Here, we identify miR-29b-1 and miR-29a target transcripts in both MCF-7 and LCC9 cells. We find that miR-29b-1 and miR-29a regulate common and unique transcripts in each cell line. The cellspecific and common downregulated genes were characterized using the MetaCore Gene Ontology (GO) enrichment analysis algorithm. LCC9-sepecific miR-29b-1/a-regulated GO processes include oxidative phosphorylation, ATP metabolism, and apoptosis. Extracellular flux analysis of cells transfected with anti-or pre-miR-29a confirmed that miR-29a inhibits mitochondrial bioenergetics in LCC9 cells. qPCR,luciferase reporter assays, and western blot also verified the ATP synthase subunit genes ATP5G1 and ATPIF1 as bone fide miR29b-1/a targets. Our results suggest that miR-29 repression of TAMresistant breast cancer cell proliferation is mediated in part through repression of genes important in mitochondrial bioenergetics. microRNAs (miRNA, miRs) are 22 nt non-coding RNAs that recognize and bind complementary seed sequences in the 3′-UTR region of a target messenger RNA (mRNA) 1, 2 . This results in translational repression and/or transcriptional degradation of the target gene. By targeting several mRNAs, miRNAs regulate several cellular and biological processes including cell cycle, cell proliferation and cell differentiation, apoptosis, cellular respiration and glycolysis (reviewed in refs 3-6). Aberrant miRNA expression mediates disease initiation and progression in breast and other cancers 7 . Seventy percent of breast tumors express estrogen receptor alpha (ERα) implying eligibility for endocrine therapies including selective estrogen receptor modulators (SERMs), e.g., Tamoxifen (TAM), and aromatase inhibitors (AI), e.g., letrozole. The efficacy of endocrine therapy is limited by relapse in ~40% of patients 8,9 . Endocrine resistance is mediated by multiple mechanisms depending on the type of therapy used (reviewed in refs 10-14). Alterations in miRNA expression are also implicated in endocrine-resistance (reviewed in refs 15 and 16).Previously, we reported miR-29b-1 and miR-29a were downregulated by TAM in TAM-sensitive (TAM-S) MCF-7 BC cells and upregulated in TAM-resistant (TAM-R) LCC2, LCC9, and LY2 BC cells 17 . There are four miR-29 family members in the human genome: miR-29b-2 and miR-29c (chromosome 1q32.2) and miR-29b-1 and miR-29a (chromosome 7q32.3). miR-29b-1 and miR-29a are separated by ~652 bp on the same pri-miRNA transcript [18][1...

Anacardic acid (AnAc), a potential dietary agent for preventing and treating breast cancer, inhibited the proliferation of estrogen receptor α (ERα) positive MCF-7 and MDA-MB-231 triple negative breast cancer cells. To characterize potential regulators of AnAc action, MCF-7 and MDA-MB-231 cells were treated for 6 h with purified AnAc 24:1n5 congener followed by next generation transcriptomic sequencing (RNA-seq) and network analysis. We reported that AnAc-differentially regulated miRNA transcriptomes in each cell line and now identify AnAc-regulated changes in mRNA and lncRNA transcript expression. In MCF-7 cells, 80 AnAc-responsive genes were identified, including lncRNA MIR22HG. More AnAc-responsive genes (886) were identified in MDA-MB-231 cells. Only six genes were commonly altered by AnAc in both cell lines: SCD, INSIG1, and TGM2 were decreased and PDK4, GPR176, and ZBT20 were increased. Modeling of AnAc-induced gene changes suggests that AnAc inhibits monounsaturated fatty acid biosynthesis in both cell lines and increases endoplasmic reticulum stress in MDA-MB-231 cells. Since modeling of downregulated genes implicated NFκB in MCF-7, we confirmed that AnAc inhibited TNFα-induced NFκB reporter activity in MCF-7 cells. These data identify new targets and pathways that may account for AnAc’s anti-proliferative and pro-apoptotic activity.

Objective: Our objective was to determine the extent surgical disciplines categorize, define, and study errors, then use this information to provide recommendations for both current practice and future study. Summary of Background Data: The report ''To Err is Human'' brought the ubiquity of medical errors to public attention. Variability in subsequent literature suggests the true prevalence of error remains unknown. Methods: In January 2020, PubMed, the Cochrane Database of Systematic Reviews, and the Cochrane Central Register of Controlled Trials were searched. Only studies with Oxford Level of Evidence Level 3 or higher were included. Results: Of 3064 studies, 92 met inclusion criteria: 6 randomized controlled trials, 4 systematic reviews, 24 cohort, 10 before-after, 35 outcome/audit, 5 cross sectional and 8 case-control studies. Over 15,933,430 patients and 162,113 errors were represented. There were 6 broad error categories, 13 different definitions of error, and 14 study methods. Conclusions: Reported prevalence of error varied widely due to a lack of standardized categorization, definitions, and study methods. Future research should focus on immediately recognizing errors to minimize harm.

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