Regulation of IGF-1-dependent cyclin D1 and E expression by hEag1 channels in MCF-7 cells: The critical role of hEag1 channels in G1 phase progression

AbstractInsulin-like Growth Factor-1 (IGF-1) plays a key role in breast cancer development and cell cycle regulation. It has been demonstrated that IGF-1 stimulates cyclin expression, thus regulating the G1 to S phase transition of the cell cycle. Potassium (K+) channels are involved in the G1 phase progression of the cell cycle induced by growth factors. However, mechanisms that allow growth factors to cooperate with K+ channels in order to modulate the G1 phase progression and cyclin expression remain unknown. Here, we focused on hEag1 K+ channels which are over-expressed in breast cancer and are involved in the G1 phase progression of breast cancer cells (MCF-7). As expected, IGF-1 increased cyclin D1 and E expression of MCF-7 cells in a cyclic manner, whereas the increase of CDK4 and 2 levels was sustained. IGF-1 stimulated p21WAF1/Cip1 expression with a kinetic similar to that of cyclin D1, however p27Kip1 expression was insensitive to IGF-1. Interestingly, astemizole, a blocker of hEag1 channels, but not E4031, a blocker of HERG channels, inhibited the expression of both cyclins after 6–8h of co-stimulation with IGF-1. However, astemizole failed to modulate CDK4, CDK2, p21WAF1/Cip1 and p27Kip1 expression. The down-regulation of hEag1 by siRNA provoked a decrease in cyclin expression. This study is the first to demonstrate that K+ channels such as hEag1 are directly involved in the IGF-1-induced up-regulation of cyclin D1 and E expression in MCF-7 cells. By identifying more specifically the temporal position of the arrest site induced by the inhibition of hEag1 channels, we confirmed that hEag1 activity is predominantly upstream of the arrest site induced by serum-deprivation, prior to the up-regulation of both cyclins D1 and E

Influence of FCGRT gene polymorphisms on pharmacokinetics of therapeutic antibodies

The neonatal Fc receptor (FcRn) encoded by FCGRT is known to be involved in the pharmacokinetics (PK) of therapeutic monoclonal antibodies (mAbs). Variability in the expression of FCGRT gene and consequently in the FcRn protein level could explain differences in PK observed between patients treated with mAbs. We studied whether the previously described variable number tandem repeat (VNTR) or copy number variation (CNV) of FCGRT are associated with individual variations of PK parameters of cetuximab. VNTR and CNV were assessed on genomic DNA of 198 healthy individuals and of 94 patients treated with the therapeutic mAb. VNTR and CNV were analyzed by allele-specific PCR and duplex real-time PCR with Taqman® technology, respectively. The relationship between FCGRT polymorphisms (VNTR and CNV) and PK parameters of patients treated with cetuximab was studied. VNTR3 homozygote patients had a lower cetuximab distribution clearance than VNTR2/VNTR3 and VNTR3/VNTR4 patients (p = 0.021). We observed no affects of VNTR genotype on elimination clearance. One healthy person (0.5%) and 1 patient (1.1%) had 3 copies of FCGRT. The PK parameters of this patient did not differ from those of patients with 2 copies. The FCGRT promoter VNTR may influence mAbs’ distribution in the body. CNV of FCGRT cannot be used as a relevant pharmacogenetic marker because of its low frequency

Linear and cooperative signaling: roles for Stat proteins in the regulation of cell survival and apoptosis in the mammary epithelium

The mammary epithelium undergoes cyclical periods of cellular proliferation, differentiation and regression. These processes are under the control of the hormones secreted during pregnancy, lactation and involution. Signaling pathways have been identified that connect the hormonal stimuli with the transcription of genes responsible for the determination of the cellular fate. The kinetics of induction and deinduction have suggested that cytokine-activated Stat proteins play a crucial role. Stat5 is strongly activated towards the end of pregnancy, persists in an activated state during pregnancy and is rapidly inactivated after cessation of suckling. Stat3 activation is hardly detectable during lactation, but is strongly induced at the onset of involution. The phenotypes of mice in which these genes have been inactivated through homologous recombination corroborate some of the functional assignments deducted from the activation pattern. Stat3 activation seems to be a driving force in the induction of apoptosis early in the involution period

Aberrant signaling in T-cell acute lymphoblastic leukemia: biological and therapeutic implications

T-cell acute lymphoblastic leukemia (T-ALL) is a biologically heterogeneous disease with respect to phenotype, gene expression profile and activation of particular intracellular signaling pathways. Despite very significant improvements, current therapeutic regimens still fail to cure a portion of the patients and frequently implicate the use of aggressive protocols with long-term side effects. In this review, we focused on how deregulation of critical signaling pathways, in particular Notch, PI3K/Akt, MAPK, Jak/STAT and TGF-beta, may contribute to T-ALL. Identifying the alterations that affect intracellular pathways that regulate cell cycle and apoptosis is essential to understanding the biology of this malignancy, to define more effective markers for the correct stratification of patients into appropriate therapeutic regimens and to identify novel targets for the development of specific, less detrimental therapies for T-ALL

Regulation of RKIP Function by Helicobacter pylori in Gastric Cancer

Helicobacter pylori (H. pylori) is a gram-negative, spiral-shaped bacterium that infects more than half of the world’s population and is a major cause of gastric adenocarcinoma. The mechanisms that link H. pylori infection to gastric carcinogenesis are not well understood. In the present study, we report that the Raf-kinase inhibitor protein (RKIP) has a role in the induction of apoptosis by H. pylori in gastric epithelial cells. Western blot and luciferase transcription reporter assays demonstrate that the pathogenicity island of H. pylori rapidly phosphorylates RKIP, which then localizes to the nucleus where it activates its own transcription and induces apoptosis. Forced overexpression of RKIP enhances apoptosis in H. pylori-infected cells, whereas RKIP RNA inhibition suppresses the induction of apoptosis by H. pylori infection. While inducing the phosphorylation of RKIP, H. pylori simultaneously targets non-phosphorylated RKIP for proteasome-mediated degradation. The increase in RKIP transcription and phosphorylation is abrogated by mutating RKIP serine 153 to valine, demonstrating that regulation of RKIP activity by H. pylori is dependent upon RKIP’s S153 residue. In addition, H. pylori infection increases the expression of Snail, a transcriptional repressor of RKIP. Our results suggest that H. pylori utilizes a tumor suppressor protein, RKIP, to promote apoptosis in gastric cancer cells

Clinical Experience With an L-Proline–Stabilized 10 % Intravenous Immunoglobulin (Privigen®): Real-Life Effectiveness and Tolerability

PURPOSE: This retrospective study evaluated the effectiveness and tolerability in clinical practice of an L-proline–stabilized 10 % intravenous immunoglobulin (IVIG; Privigen®) in patients with primary (PID) or secondary immunodeficiency (SID). METHODS: Patients from 6 centers in Europe and the US were treated with individually determined regimens of Privigen® for ≥3 months. Serum immunoglobulin G (IgG) trough levels, annualized rates of infection, hospitalization and antibiotics use, and the incidence of adverse events (AEs) were analyzed. RESULTS: Of 72 patients, three infants with severe combined immunodeficiency (SCID) were analyzed separately. The remaining 69 patients (52.2 % male; median age 38 years [range: 0.1–90.0]) with PID (82.6 %) or SID (17.4 %) received a mean (±standard deviation) Privigen® dose of 532 ± 250 mg/kg/month resulting in trough serum IgG levels of 407–1,581 mg/dL (median: 954 mg/dL). Ten patients (14.5 %) experienced 11 serious bacterial infections over 22.0 ± 15.0 months of treatment (0.087 events/patient/year, upper one-sided 99 % confidence interval: 0.170), the most common being pneumonia (11.6 %). The rates for any infection and hospitalization were 1.082 events/patient/year and 3.63 days/patient/year, respectively. Two patients with severe disease accounted for 303 of 460 hospital days. Across all 72 patients, 13 (18.1 %) patients experienced AEs, including 10 (13.9 %) patients with AEs at least possibly related to Privigen®, including headache (8.3 %), fever, and chills (2.8 % each). No related serious AEs were reported. One infant with SCID died due to severe viral infection. CONCLUSIONS: Despite the heterogeneous population, effectiveness and tolerability of Privigen® in clinical practice closely matched those reported in clinical studies