Ku proteins interact with activator protein-2 transcription factors and contribute to ERBB2 overexpression in breast cancer cell lines.
Nolens, Grégory ; Pignon, Jean-Christophe ; Koopmansch, Benjamin et al
in Breast Cancer Research [=BCR] (2009), 11(6),
INTRODUCTION: Activator protein-2 (AP-2) alpha and AP-2 gamma transcription factors contribute to ERBB2 gene overexpression in breast cancer. In order to understand the mechanism by which the ERBB2 gene ... [more ▼]
INTRODUCTION: Activator protein-2 (AP-2) alpha and AP-2 gamma transcription factors contribute to ERBB2 gene overexpression in breast cancer. In order to understand the mechanism by which the ERBB2 gene is overexpressed we searched for novel AP-2 interacting factors that contribute to its activity. METHODS: Ku proteins were identified as AP-2 alpha interacting proteins by glutathione serine transferase (GST)-pull down followed by mass spectrometry. Transfection of the cells with siRNA, expression vectors and reporter vectors as well as chromatin immunoprecipitation (ChIP) assay were used to ascertain the implication of Ku proteins on ERBB2 expression. RESULTS: Nuclear proteins from BT-474 cells overexpressing AP-2 alpha and AP-2 gamma were incubated with GST-AP2 or GST coated beads. Among the proteins retained specifically on GST-AP2 coated beads Ku70 and Ku80 proteins were identified by mass spectrometry. The contribution of Ku proteins to ERBB2 gene expression in BT-474 and SKBR3 cell lines was investigated by downregulating Ku proteins through the use of specific siRNAs. Depletion of Ku proteins led to downregulation of ERBB2 mRNA and protein levels. Furthermore, reduction of Ku80 in HCT116 cell line decreased the AP-2 alpha activity on a reporter vector containing an AP-2 binding site linked to the ERBB2 core promoter, and transfection of Ku80 increased the activity of AP-2 alpha on this promoter. Ku siRNAs also inhibited the activity of this reporter vector in BT-474 and SKBR3 cell lines and the activity of the ERBB2 promoter was further reduced by combining Ku siRNAs with AP-2 alpha and AP-2 gamma siRNAs. ChIP experiments with chromatin extracted from wild type or AP-2 alpha and AP-2 gamma or Ku70 siRNA transfected BT-474 cells demonstrated Ku70 recruitment to the ERBB2 proximal promoter in association with AP-2 alpha and AP-2 gamma. Moreover, Ku70 siRNA like AP-2 siRNAs, greatly reduced PolII recruitment to the ERBB2 proximal promoter. CONCLUSIONS: Ku proteins in interaction with AP-2 (alpha and gamma) contribute to increased ERBB2 mRNA and protein levels in breast cancer cells. [less ▲]Detailed reference viewed: 51 (16 ULg)
Androgen receptor controls EGFR and ERBB2 gene expression at different levels in prostate cancer cell lines.
Pignon, Jean-Christophe ; Koopmansch, Benjamin ; Nolens, Grégory et al
in Cancer Research (2009), 69(7), 2941-2949
EGFR or ERBB2 contributes to prostate cancer (PCa) progression by activating the androgen receptor (AR) in hormone-poor conditions. Here, we investigated the mechanisms by which androgens regulate EGFR ... [more ▼]
EGFR or ERBB2 contributes to prostate cancer (PCa) progression by activating the androgen receptor (AR) in hormone-poor conditions. Here, we investigated the mechanisms by which androgens regulate EGFR and ERBB2 expression in PCa cells. In steroid-depleted medium (SDM), EGFR protein was less abundant in androgen-sensitive LNCaP than in androgen ablation-resistant 22Rv1 cells, whereas transcript levels were similar. Dihydrotestosterone (DHT) treatment increased both EGFR mRNA and protein levels and stimulated RNA polymerase II recruitment to the EGFR gene promoter, whereas it decreased ERBB2 transcript and protein levels in LNCaP cells. DHT altered neither EGFR or ERBB2 levels nor the abundance of prostate-specific antigen (PSA), TMEPA1, or TMPRSS2 mRNAs in 22Rv1 cells, which express the full-length and a shorter AR isoform deleted from the COOH-terminal domain (ARDeltaCTD). The contribution of both AR isoforms to the expression of these genes was assessed by small interfering RNAs targeting only the full-length or both AR isoforms. Silencing of both isoforms strongly reduced PSA, TMEPA1, and TMPRSS2 transcript levels. Inhibition of both AR isoforms did not affect EGFR and ERBB2 transcript levels but decreased EGFR and increased ERBB2 protein levels. Proliferation of 22Rv1 cells in SDM was inhibited in the absence of AR and ARDeltaCTD. A further decrease was obtained with PKI166, an EGFR/ERBB2 kinase inhibitor. Overall, we showed that ARDeltaCTD is responsible for constitutive EGFR expression and ERBB2 repression in 22Rv1 cells and that ARDeltaCTD and tyrosine kinase receptors are necessary for sustained 22Rv1 cell growth. [less ▲]Detailed reference viewed: 51 (22 ULg)
Androgens regulation of the ERBB1 and ERBB2 oncogene expression in human prostate cancer cells
Pignon, Jean-Christophe ; ; Waltregny, David et al
in Acta Clinica Belgica (2006), 61(2, MAR-APR), 95-95Detailed reference viewed: 32 (15 ULg)