Intravitreal injection of erythropoietin protects against retinal vascular regression at the early stage of diabetic retinopathy in streptozotocin-induced diabetic rats.

A single intravitreal injection of erythropoietin (EPO) (50 ng/eye) or phosphate-buffered saline was administered to 5-week-old Sprague-Dawley rats at the onset of diabetes mellitus (DM) to determine and evaluate the protective effect of EPO on retinal microvessels. DM was induced by an intraperitoneal injection of streptozotocin (STZ; 60 mg/kg body weight). Morphological changes in microvessels in flat retinal preparations were evaluated during the subsequent 4 weeks by three-dimensional imaging of all blood vessels stained with fluorescein isothiocyanate-conjugated tomato lectin, following immunofluorescence techniques.

Expression of human ABCB5 confers resistance to taxanes and anthracyclines.

Human ABCB5, an ATP-binding cassette (ABC) transporter gene, has two major mRNA species. One transcript encodes an 812 amino acid polypeptide, ABCB5β, with a transmembrane domain and a nucleotide-binding domain. We isolated the cDNA of another ABCB5 mRNA that encodes a 1257 amino acid polypeptide.

Novel regulatory role for Kaposi's sarcoma-associated herpesvirus-encoded vFLIP in chemosensitization to bleomycin.

Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8) is associated with malignancy. KSHV-derived vFLIP is structurally related to cellular FLIP and binds to NEMO/IκB kinase (IKKγ) to activate NF-κB signaling. NF-κB activation is postulated to confer chemoresistance to various anticancer drugs.

DNA ligand designed to antagonize EBNA1 represses Epstein-Barr virus-induced immortalization.

Epstein-Barr virus (EBV) transforms human B lymphocytes into immortalized cells in vitro and is associated with various malignancies in vivo. EBNA1, which is expressed in the majority of EBV-infected cells, recognizes specific DNA sequences at the cis-acting latent origin of plasmid replication (oriP) element of the EBV genome. EBNA1 plays a critical role in the viral episome maintenance and transactivates viral transforming genes in latently infected cells.

In vivo expansion of MDR1-transduced cells accompanied by a post-transplantation chemotherapy regimen with mitomycin C and methotrexate.

Background: A recurrent breast cancer patient received high-dose chemotherapy, a transplant of multidrug resistance 1 (MDR1)-transduced cells and four different protocols of post-transplantation chemotherapy. We report the analysis of MDR1-transduced cells in this patient.

Methods: MDR1 transgene levels in the peripheral blood mononuclear cells of the patient were evaluated by polymerase chain reaction (PCR).

BCRP/ABCG2 confers anticancer drug resistance without covalent dimerization.

In previous studies, we demonstrated that the breast cancer resistance protein (BCRP, ABCG2) forms an S-S homodimer. The BCRP-C603S mutant substituting Ser for Cys-603 in the third extracellular domain formed both a 70-75-kDa monomer and 140-150-kDa dimer, suggesting that Cys-603 is an important residue in the covalent bridge. These results also suggested the involvement of other Cys residues in dimer formation.

Pharmacological interaction with sunitinib is abolished by a germ-line mutation (1291T>C) of BCRP/ABCG2 gene.

Sunitinib malate (Sutent, SU11248) is a small-molecule multitargeted tyrosine kinase inhibitor (TKI) used for the treatment of renal cell carcinoma and imatinib-resistant gastrointestinal stromal tumors. Some TKIs can overcome multidrug resistance conferred by ATP-binding cassette transporter, P-glycoprotein (P-gp)/ABCB1, multidrug resistance-associated protein 1 (MRP1)/ABCC1, and breast cancer resistance protein (BCRP)/ABCG2. Here, we analyzed the effects of sunitinib on P-gp and on wild-type and germ-line mutant BCRPs.

Functional availability of gamma-herpesvirus K-cyclin is regulated by cellular CDK6 and p16INK4a.

Viral K-cyclin derived from Kaposi's sarcoma-associated herpesvirus is homologous with mammalian D-type cyclins. Here, we demonstrated the regulatory mechanisms for K-cyclin function and degradation in human embryonic kidney HEK293 and primary effusion lymphoma JSC-1 cell lines. Proteasome inhibitor MG132 treatment induced an accumulation of ubiquitinated K-cyclin in these cells, and co-expression of CDK6 prevented K-cyclin ubiquitination.

Substrate-dependent bidirectional modulation of P-glycoprotein-mediated drug resistance by erlotinib.

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) inhibit the function of certain adenosine triphosphate (ATP)-binding cassette transporters, including P-glycoprotein/ABCB1 and breast cancer resistance protein (BCRP)/ABCG2. We previously reported an antagonistic activity of gefitinib towards BCRP. We have now analyzed the effects of erlotinib, another EGFR-TKI, on P-glycoprotein and BCRP.

Pharmacological interplay between breast cancer resistance protein and gefitinib in epidermal growth factor receptor signaling.

Background: It has been previously shown that gefitinib reverses breast cancer resistance protein (BCRP)-mediated drug resistance. Here, the impact of BCRP on gefitinib-mediated inhibition in epidermal growth factor receptor (EGFR) signaling is evaluated.

Materials And Methods: Sensitivity to gefitinib was determined by growth inhibition assay, and intracellular gefitinib levels were measured with HPLC.

Functions of the breast cancer resistance protein (BCRP/ABCG2) in chemotherapy.

The breast cancer resistance protein, BCRP/ABCG2, is a half-molecule ATP-binding cassette transporter that facilitates the efflux of various anticancer agents from the cell, including 7-ethyl-10-hydroxycamptothecin, topotecan and mitoxantrone. The expression of BCRP can thus confer a multidrug resistance phenotype in cancer cells, and its transporter activity is involved in the in vivo efficacy of chemotherapeutic agents. Thus, the elucidation of the substrate preferences and structural relationships of BCRP is essential to understanding its in vivo functions during chemotherapeutic treatments.

Increased bone resorption may play a crucial role in the occurrence of osteopenia in patients with type 2 diabetes: Possible involvement of accelerated polyol pathway in its pathogenesis.

In order to investigate the underlying mechanism of alterations in bone mineral metabolism in patients with type 2 diabetes, we determined circulating levels of bone functional markers along with urinary excretion of sorbitol (SOR) and bone mineral density (BMD), and also examined their mutual interrelationship. A total of 151 male type 2 diabetic patients were examined in this study. Forty-eight age-matched male healthy subjects were also studied as the controls.

Retroviral integration site analysis and the fate of transduced clones in an MDR1 gene therapy protocol targeting metastatic breast cancer.

A clinical study of an MDR1 gene therapy protocol targeting metastatic breast cancer has been conducted in which the patients received high-dose chemotherapy, a transplant of MDR1-transduced autologous CD34(+) cells, and docetaxel. We herein report the molecular results of a 6-year follow-up of an individual in this study (patient 1). HaMDR-transduced cells, which had been initially detected in the peripheral blood of this individual, were found to have gradually decreased.

Pilot study of MDR1 gene transfer into hematopoietic stem cells and chemoprotection in metastatic breast cancer patients.

A major problem in high-dose chemotherapy with autologous hematopoietic stem cell transplantation is insufficient function of reconstituted bone marrow that limits the efficacy of post-transplantation chemotherapy. Because transduction of hematopoietic stem cells with the multidrug resistance 1 (MDR1) gene might circumvent this problem, we conducted a pilot study of MDR1 gene therapy against metastatic breast cancer. Peripheral blood stem cells were harvested, and one-third of the cells were transduced with MDR1 retrovirus.

Inhibition of the mitogen-activated protein kinase pathway results in the down-regulation of P-glycoprotein.

The multidrug resistance gene 1 (MDR1) product, P-glycoprotein (P-gp), pumps out a variety of anticancer agents from the cell, including anthracyclines, Vinca alkaloids, and taxanes. The expression of P-gp therefore confers resistance to these anticancer agents. In our present study, we found that FTI-277 (a farnesyltransferase inhibitor), U0126 [an inhibitor of mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK)], and 17-allylamino-17-demethoxygeldanamycin (an inhibitor of heat shock protein 90) reduced the endogenous expression levels of P-gp in the human colorectal cancer cells, HCT-15 and SW620-14.

The identification of two germ-line mutations in the human breast cancer resistance protein gene that result in the expression of a low/non-functional protein.

Purpose: We examined the effects of the nine nonsynonymous germ-line mutations/SNPs in the breast cancer resistance protein (BCRP/ABCG2) gene on the expression and function of the protein.

Materials And Methods: We generated cDNAs for each of these mutants (G151T, C458T, C496G, A616C, T623C, T742C, T1291C, A1768T, and G1858A BCRP) and compared the effects of their exogenous expression in PA317 cells with a wild-type control.

Results: PA/F208S cells (T623C BCRP-transfectants) expressed marginal levels of a BCRP protein species (65kDa), which is slightly smaller than wild-type (70kDa), but this mutant did not appear on the cell surface or confer drug resistance.

Flavonoids inhibit breast cancer resistance protein-mediated drug resistance: transporter specificity and structure-activity relationship.

Purpose: ATP-binding cassette (ABC) transporters, such as P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and multidrug resistance-related protein 1 (MRP1), confer resistance to various anticancer agents. We previously reported that some flavonoids have BCRP-inhibitory activity. Here we show the reversal effects of an extensive panel of flavonoids upon BCRP-, P-gp-, and MRP1-mediated drug resistance.

Estrogen-mediated post transcriptional down-regulation of P-glycoprotein in MDR1-transduced human breast cancer cells.

The human multidrug resistance gene 1 (MDR1) encodes the plasma membrane P-glycoprotein (P-gp/ABCB1) that functions as an efflux pump for various anticancer agents. We recently reported that estrogens down-regulate the expression of breast cancer resistance protein (BCRP/ABCG2). In our present study we demonstrate that estrogens also down-regulate P-gp expression in the MDR1-transduced, estrogen receptor alpha (ER-alpha)-positive human breast cancer cells, MCF-7/MDR and T-47D/MDR.

A T3587G germ-line mutation of the MDR1 gene encodes a nonfunctional P-glycoprotein.

The human multidrug resistance gene 1 (MDR1) encodes a plasma membrane P-glycoprotein (P-gp) that functions as an efflux pump for various structurally unrelated anticancer agents. We have identified two nonsynonymous germ-line mutations of the MDR1 gene, C3583T MDR1 and T3587G MDR1, in peripheral blood cell samples from Japanese cancer patients. Two patients carried the C3583T MDR1 allele that encodes H1195Y P-gp, whereas a further two carried T3587G MDR1 that encodes I1196S P-gp.

Functional SNPs of the breast cancer resistance protein-therapeutic effects and inhibitor development.

Breast cancer resistance protein (BCRP) is a half-molecule ATP-binding cassette transporter that pumps out various anticancer agents such as 7-ethyl-10-hydroxycamptothecin, topotecan and mitoxantrone. We have previously identified three polymorphisms within the BCRP gene, G34A (substituting Met for Val-12), C376T (substituting a stop codon for Gln-126) and C421A (substituting Lys for Gln-141). C421A BCRP-transfected murine fibroblast PA317 cells showed markedly decreased protein expression and low-level drug resistance when compared with wild-type BCRP-transfected cells.

Breast cancer resistance protein: molecular target for anticancer drug resistance and pharmacokinetics/pharmacodynamics.

Breast cancer resistance protein (BCRP) is a half-molecule ATP-binding cassette transporter that forms a functional homodimer and pumps out various anticancer agents, such as 7-ethyl-10-hydroxycamptothecin, topotecan, mitoxantrone and flavopiridol, from cells. Estrogens, such as estrone and 17beta-estradiol, have been found to restore drug sensitivity levels in BCRP-transduced cells by increasing the cellular accumulation of such agents. Furthermore, synthetic estrogens, tamoxifen derivatives and phytoestrogens/flavonoids have now been identified that can effectively circumvent BCRP-mediated drug resistance.