Naturally occurring dominant-negative Stat5 suppresses transcriptional activity of estrogen receptors and induces apoptosis in T47D breast cancer cells

Abstract

Signal transducer and activator of transcription (Stat) 5 regulates growth, differentiation, and survival of mammary and hematopoietic cells. The role of Stat5 in breast cancer has not been established, although Stat5 is critical for some hematopoietic malignancies. We detected for the first time that Stat5b is constitutively activated in human breast cancer cell lines, and analysed the role of Stat5 in estrogen receptor(ER)-positive breast cancer cell lines using dominant-negative variants of Stat5. Two distinct carboxyl-truncated Stat5a derivatives were generated. Stat5aD740 corresponded to a naturally occurring alternative splice variant, and Stat5aD713 was analogous to an 80 kDa Stat5a product of a nuclear protease. Stat5aD740 and Stat5aD713 displayed comparable dominant-negative properties and suppressed transcriptional activity of wildtype Stat5a and Stat5b equally well. Cotransfection experiments revealed that Stat5aD740 completely blocked transcriptional activity of endogenous estrogen receptor in T47D and MCF7 cells, and of both ERa and ERb in COS-7 cells. Stat5aD740 was selected for adenoviral delivery, and high-efficiency expression of tyrosine phosphorylated Stat5aD740 was achieved in infected cells. Adenoviral-mediated Stat5aD740 induced apoptosis in T47D cells but not in caspase-3-negative MCF7 cells. The present study indicates that overexpression of a dominantnegative variant of Stat5 suppresses ER transcriptional activity and induces apoptosis in estrogen-responsive breast cancer tissue culture cells.

Lactogens protect rodent and human beta cells against glucolipotoxicity-induced cell death through Janus kinase‐2 (JAK2)/signal transducer and activator of transcription-5 (STAT5) signalling

“…5a). To assess the role of p-STAT5 activation in the pro-survival effect of PRL, we used a dominant negative mutant of Stat5 (DNStat5) that inhibits both STAT5a and STAT5b action [33]. The DNStat5 mutant blocked the induction of cyclinD2 by oPRL, a known PRL target gene activated by STAT5 [22], confirming the functional effectiveness of the DNStat5 mutant (Fig.…”

“…Adenovirus transduction Adenovirus (Adv) constructs containing cDNAs of dominant negative (DN) Stat5a [33], or encoding the proteins Cre recombinase or green fluorescent protein (GFP), were prepared and transduced at a multiplicity of infection of 80-100 pfu/cell as previously described [26,31]. GLT-treatment (as described above) and immunostaining for CRE were performed 24 h after Adv transduction.…”

EGF stimulates cyclooxygenase-2 expression through the STAT5 signaling pathway in human lung adenocarcinoma A549 cells

“…cDNA of a carboxyl-truncated STAT5a variant, Stat5a△740, which displays a dominantnegative (DN) effect on both Stat5a and Stat5b-mediated transcription, was used to block the EGF-induced STAT5 signaling (24). The adenovirus containing the DN-STAT5 (Ad-CMV5Stat5a△740) plasmid, wild-type (WT)-STAT5 (AdWT-STAT5) and the control adenovirus (control) were provided by Dr Xiaofei Qin (China Medical University).…”

Crosstalk between steroid receptors and the c-Src-receptor tyrosine kinase pathways: implications for cell proliferation

“…The demonstration that IGF-1, EGF and HER family members can activate steroid receptor transcriptional activity in the absence of ligand, and that steroids and growth factors rapidly stimulate the same intracellular signaling pathways, suggests that there may be some common stimulated pathways for cell proliferation and tumor growth. Interestingly, experiments with several pharmacological inhibitors as well as dominant-negative signaling molecules suggest that the MAPK, PI3K, c-Src and STAT pathways all play critical roles in mediating both steroid and growth factor stimulation of cancer cells (Castoria et al, 1999(Castoria et al, , 2001Yue et al, 2002;Kloth et al, 2003;Stoica et al, 2003;Yamashita et al, 2003). Both steroids and growth factors stimulate expression of several genes critical for cell cycle progression, including cyclin D1, cyclin E, and cdk inhibitors p21 and p27, and ongoing expression profiling of breast cancer cells and breast tumors may provide some information on larger subsets of genes that are common for both steroid and growth factorstimulated growth (Sotiriou et al, 2003;Frasor et al, 2004).…”