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Upon engagement of the B Cell Receptor (BCR) of WEHI 231 immature B cells, a drop in c-Myc expression is followed by activation of the cyclin-dependent kinase inhibitor (CKI) p27Kip1, which induces growth arrest and apoptosis. Here, we report inverse patterns of p27 and c-Myc protein expression follow BCR engagement. We present evidence demonstrating, for the first time, that the p27Kip1 gene is a target of transcriptional repression by c-Myc. Specifically, the changes in p27 protein levels correlated with changes in p27 mRNA levels, and gene transcription. Induction of p27 promoter activity followed BCR engagement of WEHI 231 cells, and this induction could be repressed upon co-transfection of a c-Myc expression vector. Inhibition of the TATA-less p27 promoter by c-Myc was also observed in Jurkat T cells, vascular smooth muscle, and Hs578T breast cancer cells, extending the observation beyond immune cells. Consistent with a putative Inr element CCAGACC (where +1 is underlined) at the start site of transcription in the p27 promoter, deletion of Myc homology box II reduced the extent of repression. Furthermore, enhanced repression was observed upon transfection of the c-Myc ‘super-repressor’, with mutation of Phe115 to Leu. The sequences mediating transcriptional activity and c-Myc repression were mapped to bp -20 to +20 of the p27 gene. Finally, binding of Max was shown to facilitate c-Myc binding and repression of p27 promoter activity. Overall, these studies identify the p27 CKI gene as a new target whereby c-Myc can control cell proliferation, survival and neoplastic transformation. Oncogene (2001) 20, 1688–1702. [ABSTRACT FROM AUTHOR]

NF-κB/Rel transcription factors regulate many genes involved in control of cellular proliferation, neoplastic transformation, and apoptosis, including the c-myc oncogene. Recently, we have observed that levels of NF-κB and aryl hydrocarbon receptor (AhR), which mediates malignant transformation by environmental carcinogens, are highly elevated and appear constitutively active in breast cancer cells. Rel factors have been found to functionally interact with other transcription factors. Here we demonstrate a physical and functional association between the RelA subunit of NF-κB and AhR resulting in the activation of c-myc gene transcription in breast cancer cells. RelA and AhR proteins were co-immunoprecipitated from cytoplasmic and nuclear extracts of non-malignant MCF-10F breast epithelial and malignant Hs578T breast cancer cells. In transient co-transfection, RelA and AhR gene products demonstrated cooperation in transactivation of the c-myc promoter, which was dependent on the NF-κB elements, and in induction of endogenous c-Myc protein levels. A novel AhR/RelA-containing NF-κB element binding complex was identified by electrophoretic mobility shift analysis of nuclear extracts from RelA and AhR co-transfected Hs578T cells. Thus, the RelA and AhR proteins functionally cooperate to bind to NF-κB elements and induce c-myc gene expression. These findings suggest a novel signaling mechanism whereby the Ah receptor can stimulate proliferation and tumorigenesis of mammary cells. Oncogene (2000) 19, 5498–5506. [ABSTRACT FROM AUTHOR]

Background: There is growing interest in the effect of postoperative analgesics on oncological outcomes after cancer surgery. We investigated the impact of tramadol after breast cancer surgery on recurrence and mortality and explored the mechanism by which tramadol affects cultured breast cancer cells in vitro.Methods: Electronic medical records of patients who underwent breast cancer surgery between November 2005 and December 2010 at Severance Hospital in Korea were reviewed. Cox regression analyses were used to identify factors related to postoperative recurrence and mortality. We performed the sensitivity test with propensity score matching to adjust for selection bias. In addition, we investigated the effects of tramadol on human breast adenocarcinoma (Michigan Cancer Foundation-7 [MCF-7]) cells via assessment of cell viability, clonogenic assay, and cell cycle analysis in vitro.Results: Of 2588 breast cancer patients, 36.4% had received tramadol. Those who received tramadol had a 0.71-fold decreased risk of recurrence and a 0.56-fold decrease in mortality. The MCF-7 cell viability assays showed that tramadol had an anti-proliferative effect by cell cycle arrest, suppressing colony formation, and regulation of oestrogen and progesterone receptors. Tramadol induced apoptosis of MCF-7 cells via extracellular signal-regulated kinases by decreasing of 5-hydroxytryptamine (HT)2B receptor and transient receptor potential vanilloid-1 expression.Conclusions: After breast cancer surgery, patients who received tramadol had a decreased risk of postoperative recurrence and mortality. The anti-tumour effect of tramadol appears to involve inhibition of proliferation, induction of apoptosis, and effects on 5-HT2B receptor and TRPV-1. [ABSTRACT FROM AUTHOR]