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PDF file - 440KB, Immunohistochemical analyses of RHBDF1 and HIF1a expression in breast cancer clinical specimens (S1). RHBDF1 action on HIF1a stability does not involve HIF1a mRNA levels (S2). Prediction of transmembrane topology and phosphorylation sites of RHBDF1 (S3). Effects of peptide VR56 on the expression of HIF1a targeted genes and breast cancer cell viability (S4). Inhibitory effect of RHBDF1 gene silencing in MCF7 cells on HIF1a stability (S5). Western blotting analysis showing involvement of RACK1 and RHBDF1 in HIF1a stabilization in breast cancer cell MCF7 or T47D (S6).

PDF file - 93KB, RHBDF1 expression and clinicopathological features of invasive breast cancer (IBC).

PDF file - 63KB, Amino acid sequences of peptides resembling potential phosphorylation sites on the RHBDF1 protein.

Intermittent oxygen deficiency in cancers promotes prolonged inflammation, continuous angiogenesis, and increased drug resistance. Hypoxia-inducible factor-1 (HIF1) has a pivotal role in the regulation of cellular responses to oxygen deficiency. The α-subunit of HIF1 (HIF1α) is degraded in normoxia but stabilized in hypoxia. However, the molecular mechanism that controls oxygen-independent degradation of HIF1α has remained elusive. Human rhomboid family-1 (RHBDF1) is a member of a large family of nonprotease rhomboids whose function is basically unknown. We report here that RHBDF1 expression in breast cancer is highly elevated and is strongly correlated with escalated disease progression, metastasis, poor prognosis, and poor response to chemotherapy. We show that RHBDF1 interaction with the receptor of activated protein-C kinase-1 (RACK1) in breast cancer cells prevents RACK1-assisted, oxygen-independent HIF1α degradation. In addition, we show that the HIF1α-stabilizing activity of RHBDF1 diminishes when the phosphorylation of a tyrosine residue on the RHBDF1 molecule is inhibited. These findings are consistent with the view that RHBDF1 is a critical component of a molecular switch that regulates HIF1α stability in cancer cells in hypoxia and that RHBDF1 is of potential value as a new target for cancer treatment. Cancer Res; 74(10); 2719–30. ©2014 AACR.

PDF file - 148KB

Intermittent oxygen deficiency in cancers promotes prolonged inflammation, continuous angiogenesis, and increased drug resistance. Hypoxia-inducible factor-1 (HIF1) has a pivotal role in the regulation of cellular responses to oxygen deficiency. The α-subunit of HIF1 (HIF1α) is degraded in normoxia but stabilized in hypoxia. However, the molecular mechanism that controls oxygen-independent degradation of HIF1α has remained elusive. Human rhomboid family-1 (RHBDF1) is a member of a large family of nonprotease rhomboids whose function is basically unknown. We report here that RHBDF1 expression in breast cancer is highly elevated and is strongly correlated with escalated disease progression, metastasis, poor prognosis, and poor response to chemotherapy. We show that RHBDF1 interaction with the receptor of activated protein-C kinase-1 (RACK1) in breast cancer cells prevents RACK1-assisted, oxygen-independent HIF1α degradation. In addition, we show that the HIF1α-stabilizing activity of RHBDF1 diminishes when the phosphorylation of a tyrosine residue on the RHBDF1 molecule is inhibited. These findings are consistent with the view that RHBDF1 is a critical component of a molecular switch that regulates HIF1α stability in cancer cells in hypoxia and that RHBDF1 is of potential value as a new target for cancer treatment. Cancer Res; 74(10); 2719–30. ©2014 AACR.

The transfer of Cd(II) assisted by dithizone (DzH2) present in methyl isobutyl ketone (MIBK) at water–MIBK interface was systematically investigated by novel electrolyte dropping electrode (EDE) using cyclic voltammetry (CV) and square wave voltammetry (SWV). The protonation of DzH2 at polarized liquid–liquid interface was studied. The stoichiometry of resulting metal ligand complex was formulated. Transfer peak current was proportional to the bulk concentration of the Cd(II) varied between 1 μM to 0.1 mM and the maximum value of relative standard deviation was about 3.17%. The presented procedure was successfully applied for determination of Cd(II) in real samples.

The transfer of Pb(II) facilitated by 1,10-phenanthroline (phen) presented in the methyl isobutyl ketone (MIBK) across the polarized water|MIBK interface was systematically investigated by novel electrolyte dropping electrode using cyclic voltammetry and square wave voltammetry. The protonation of 1,10-phenanthroline in polarized water|MIBK interface was explored. The dependence of the half-wave potential on PbCl2 and phen concentration was investigated and the stoichiometry of resulting metal ligand complex was formulated. Different concentrations of PbCl2 was determined online and the transfer peak current was proportional to the bulk concentration of the Pb2+ varied between 8 μM to 0.5 mM and 0.5 to 1 mM, and the linear regression coefficients were 0.9953 and 0.9995, respectively. The standard deviations (RSD) were 4.33, 5.80, 4.13, 3.88, 2.23, 3.39, 1.38, 2.42, 2.00, 2.73 and 2.37% for 8 times successive determinations of Pb2+ for the concentrations of 0.008, 0.05, 0.1, 0.2, 0.3, 0.35, 0.4, 0.5, 0.8, 0.9 and 1 mM, respectively. The long time stability of the electrolyte dropping electrode was tested and the result showed that this novel method was simple, rapid and efficient.