PTP1B Suppresses Prolactin Activation of Stat5 in Breast Cancer Cells

Abstract

Basal levels of nuclear localized, tyrosine phosphorylated Stat5 are present in healthy human breast epithelia. In contrast, Stat5 phosphorylation is frequently lost during breast cancer progression, a finding that correlates with loss of histological differentiation and poor patient prognosis. Identifying the mechanisms underlying loss of Stat5 phosphorylation could provide novel targets for breast cancer therapy. Pervanadate, a general tyrosine phosphatase inhibitor, revealed marked phosphatase regulation of Stat5 activity in breast cancer cells. Lentiviral-mediated shRNA allowed specific examination of the regulatory role of five tyrosine phosphatases (PTP1B, TC-PTP, SHP1, SHP2, and VHR), previously implicated in Stat5 regulation in various systems. Enhanced and sustained prolactin-induced Stat5 tyrosine phosphorylation was observed in T47D and MCF7 breast cancer cells selectively in response to PTP1B depletion. Conversely, PTP1B overexpression suppressed prolactin-induced Stat5 tyrosine phosphorylation. Furthermore, PTP1B knockdown increased Stat5 reporter gene activity. Mechanistically, PTP1B suppression of Stat5 phosphorylation was mediated, at least in part, through inhibitory dephosphorylation of the Stat5 tyrosine kinase, Jak2. PTP1B knockdown enhanced sensitivity of T47D cells to prolactin phosphorylation of Stat5 by reducing the EC(50) from 7.2 nmol/L to 2.5 nmol/L. Immunohistochemical analyses of two independent clinical breast cancer materials revealed significant negative correlations between levels of active Stat5 and PTP1B, but not TC-PTP. Collectively, our data implicate PTP1B as an important negative regulator of Stat5 phosphorylation in invasive breast cancer.

Scribble is required for pregnancy-induced alveologenesis in the adult mammary gland

“…S3H). Unlike EpH4 cells, T-47D, a human breast-cancer-derived cell line, is commonly used for investigating PRL-induced signaling and biology in monolayer conditions (Johnson et al, 2010;Gallego et al, 2001). T-47D cells stably expressing shSCRIB displayed a marked decrease in STAT5 phosphorylation starting at 15 min of PRL stimulation compared to control cells (Fig.…”

Serotonin suppresses β-casein expression via PTP1B activation in human mammary epithelial cells

“…Therefore, we focused on PTP1B and SOCS-3 expression, which regulate the phosphorylation of STAT5 in mammary epithelial cells [18,19]. Treatment with 5-HT alone enhanced PTP1B expression and this increase was significantly inhibited by the PKA inhibitor (KT5720) (Fig.…”

“…*p < 0.05 using one-way ANOVA followed by a TukeyeKramer test for the indicated comparison. suppress STAT5 tyrosine phosphorylation in the Jak2/STAT5 pathway in mammary epithelial cells [18,19]. Therefore, to determine whether 5-HT treatment increased PTP1B and SOCS-3 expression in MCF-12A cells and whether the cAMP/PKA pathway was involved in the regulation of SOCS-3 and PTP1B expression, SOCS-3 and PTP1B protein levels in the cells treated with 5-HT and/ or a PKA inhibitor (KT5720, 5 mM) were measured.…”

“…ERK1/2, a member of the mitogenactivated protein kinase family (MAPK) family, and Akt, which is involved in phosphoinositide 3-kinase (PI3K)/Akt signaling, was found to inhibit the Jak2/STAT5 pathway via interleukin-6 in human melanoma cells [17]. Furthermore, suppressor of cytokine signaling-3 (SOCS-3) and protein-tyrosine phosphatase 1B (PTP1B), which inhibit STAT5 phosphorylation, were identified as negative regulators of the PRL/Jak2/STAT5 pathway in human mammary epithelium [18,19], and these regulators were shown to be induced by increased intracellular cAMP [20,21]. These reports imply that effectors such as PKA, ERK1/2, Akt, SOCS-3, or PTP1B might function through 5-HT-mediated suppression of b-casein or STAT5 phosphorylation in MCF-12A cells.…”

Decoding directional genetic dependencies through orthogonal CRISPR/Cas screens

“…In addition, a number of genetic interactions observed in our screen have already been described in the literature, including the activation of the MYC gene by the MYB transcription factor [53][54][55] , the synergistic interaction between MYB and ETS1 in transcriptional regulation of their shared targets [56][57][58] , dephosphorylation of STAT5B by the phosphatase PTPN1 (also known as PTP1B) [59][60][61] ,and the accepted interaction between PTPN1 and BCR-ABL 62 . Together, these validated and published data confirm the usefulness of this technology to uncover directional genetic interactions between known and unknown factors in cancer cells.…”