Gene-transfected Cells Research Articles

Reversal of Multidrug Resistance by Natural Substances from Plants

The multidrug resistance (MDR) proteins that belong to the ATP-binding cassette superfamily such as P-glycoprotein (P-gp) and MRP1, are present in a majority of human tumors and constitute an important cause of therapeutic failure. Selective inhibitors of the MDR-efflux proteins may improve the effectiveness of cancer chemotherapy. Their mechanism of action was believed to be a competition between resistance modifiers and drugs for the same binding site of P-gp. In our previous work we studied modulation of MDR in cancer cells expressing P-gp or MRP1 by selected carotenoids, flavonoids and extracts from medically important Chinese plants. Capsanthin and capsorubin, carotenoids isolated from paprika, were identified as potent P-gp inhibitors, while lycopene, lutein, antheraxanthin and violaxanthin induced moderate effects. Among flavonoids, effective modulators were rotenone, chrysin, phloretin and sakuranetin. Some chloroform extracts of Chinese herbs were also found to inhibit MDR efflux pumps. The effects of the modulators on P-gp activity were studied by measuring rhodamine 123 uptake in several cancer cells such as the human MDR1 gene-transfected mouse lymphoma cells (L1210) and human breast cancer cells MDA-MB-231 expressing the MRP1 pump (HTB26). Additionally, the ability to alter biophysical properties of lipid bilayers by selected carotenoids was studied by differential scanning calorimetry. The antiproliferative effects as well as the MDR reversal activity of the studied compounds, applied in combination with anticancer drugs, were also discussed.

Bone Regeneration with BMP-2 Gene-modified Mesenchymal Stem Cells Seeded on Nano-hydroxyapatite/Collagen/ Poly(L-Lactic Acid) Scaffolds

In this study, the capacity of bone morphogenetic protein 2 (BMP-2) gene-transfected bone marrow-derived mesenchymal stem cells (MSCs) in combination with nano-hydroxyapatite/collagen/poly(L-lactic acid) (nHAC/ PLA) to improve the repair of bone defects in rabbit was explored. MSCs from New Zealand White rabbits were cultured and injected with pIRES2-EGFPhBMP-2 or pIRES2-EGFP by electroporation. After the transfer efficiency was determined through the expression of EGFP, the MSCs were seeded on scaffolds to generate an in vitro 3D cell/scaffold construct. The adhesion and proliferation of the MSCs cultured in the scaffold was assessed by SEM. The cellular constructs obtained were allografted into the 15 mm critical-sized segmental bone defects in the radius of New Zealand White rabbits for 12 weeks. The bone regeneration was assessed by radiographical and histological analyses. In vitro, nHAC/PLA facilitated MSC adhesion and proliferation on the scaffold, and gene transfer efficiency reached a maximum of 35.5 ± 3.8%. In vivo, the implantation of BMP-2 transfected MSCs/nHAC/PLA construct significantly enhanced the formation of new bone in the segmental defect, compared to the control groups. This novel 3D BMP-2 transfected MSCs/nHAC/PLA construct has the potential for bone repair by genetic tissue engineering approach.

Construction of CYP2E1 recombinant adenovirus vector and its anti-tumor effects

To construct the human cytochrome P-450 CYP2E1 (CYP2E1) recombinant adenovirus vector and detect its anti-tumor effects in combination with chemotherapeutic drugs so as to provide rationales for gene directed enzyme prodrug therapy (GDEPT). CYP2E1 cDNA was cloned from human liver and a recombinant adenovirus vector constructed at a titer of 1 × 10(12) pfu/ml. Human bone marrow-derived mesenchymal stem cells (BMSCs) were separated, cultured, purified and detected. The tropism of BMSCs for cancer cells was detected by Transwell technique. These recombinant vectors were transferred into BMSCs and A375 cells and the expressions of EGFP and CYP2E1 detected by fluorescence microscope, RT-PCR and Western blot respectively. Inverted microscope, MTT and Annexin V-FITC/PI were employed to detect the anti-tumor effect of CYP2E1 recombinant adenovirus vectors in combination with chemotherapeutic prodrug dacarbazine (DTIC). The recombinant adenovirus vectors pAd5CMV-NpA-CYP2E1 and pAd5CMV-NpA-EGFP were constructed successfully. BMSCs were successfully separated and they could migrate in vitro through a polycarbonate filter toward K562 and A375 cells in the lower chamber. Fluorescence microscope was used to detect the expression of EGFP while both RT-PCR and Western blot revealed a high expression of CYP2E1 in gene-transfected group cells. The dead cell counts of co-culture group of gene-transfected BMSCs and wild type A375 cells were significantly higher than those of the control under inverted microscope. The results of MTT showed that the growth inhibition of gene-transfected group cells was increased with DTIC concentration in a concentration dependent manner. IC(50) of group BMSCs-CYP2E1 + A375 was (0.17 ± 0.13) mmol/L, and that of the control group was (0.65 ± 0.20) mmol/L (P < 0.01). The DTIC concentration at which BMSCs were relatively safe might be selected at 0.05 mmol/L. Annexin V-FITC/PI confirmed that the apoptosis rate of BMSCs-CYP2E1 + A375 group was significantly higher than that of the control group after a 48-hour treatment of 0.05 mmol/L DTIC (26.8 ± 2.0 vs 8.7 ± 1.3, P < 0.01). With an in vitro tropism for cancer cells, BMSCs transferred with CYP2E1 recombinant adenovirus vectors have anti-tumor effects probably synergistically with chemotherapeutic drugs.

PCMV–BMP-2–Transfected Cell–Mediated Gene Therapy in Anterior Cruciate Ligament Reconstruction in Rabbits

This study investigated the effect of plasmid cytomegalovirus (pCMV)-bone morphogenetic protein 2 (BMP-2) gene therapy on the healing of the tendon-bone interface after anterior cruciate ligament (ACL) reconstruction in rabbits. The pCMV-BMP-2 was synthesized from full-length human BMP-2 complementary deoxyribonucleic acid, followed by cloning into pCMV Script vector (Clontech Laboratories, Inc., San Jose, CA), and was delivered by a xenogeneic (rat kidney) cell line. The ACL was reconstructed by the transfer of extensor digital tendon in the proximal tibia. In the study group the pCMV-BMP-2 gene-transfected normal rat kidney cells mixed with calcium alginate gel were placed at the tendon-bone interface, whereas no pCMV-BMP-2 was used in the control group. The evaluations included radiography, bone mineral density, magnetic resonance imaging, biomechanical study, histologic examination, and immunohistochemical analysis. Bone mineral density showed no significant difference between the groups (P > .05). Magnetic resonance imaging showed significantly better contact between tendon and bone in the study group compared with the control group (P < .0001). In the biomechanical study, significantly higher failure load and maximal graft tension were noted in the study group compared with the control group (P = .034). The modes of graft failure were rupture of the tendon proper in 78% and graft pullout from the bone tunnel in 22% of specimens in the study group versus graft rupture in 22% and graft pullout in 78% in the control group (P = .018). On histologic examination, the study group showed significantly better integration between tendon and bone, as well as more bone tissue around the tendon graft, than the control group (P = .0004). On immunohistochemical analysis, the study group showed significantly higher expressions of von Willebrand factor, vascular endothelial growth factor, proliferation cell nuclear antigen, and BMP-2 than the control group (P < .05). The pCMV-BMP-2 gene therapy significantly improved the healing of tendon to bone and promoted angiogenesis and osteogenesis at the tendon-bone interface after ACL reconstruction in the rabbit model. Application of pCMV-BMP-2 gene therapy may be an effective adjunct therapy in ACL reconstruction.

Overexpression of HER2 signaling to WAVE2–Arp2/3 complex activates MMP-independent migration in breast cancer

The final signal for triggering the formation of lamellipodia that initiate directional migration of mammalian cells is binding of the Wiskott-Aldrich syndrome (WASP)/WASP family verproline-homologous protein 2 (WAVE2) to the actin-related protein 2 and 3 (Arp2/3) complex. This WAVE2-Arp2/3 signal is suggested to be enhanced in some breast cancers, facilitating invasion, and/or metastasis. Here, we demonstrated one cause of the enhanced signal using four breast cancer cell lines (SKBR3, AU565, MCF7, and MDA-MB-231). The WAVE2-Arp2/3 signal was estimated semi-quantitatively by counting the number of lamellipodia expressing both WAVE2 and Arp2 using high-power confocal laser microscopy. Higher expression of the WAVE2-Arp2/3 signal was detected in SKBR3 and AU565, which have HER2 gene amplification, than in the other two cell lines that lack HER2 gene amplification. Trastuzumab suppressed both the formation of lamellipodia and migration in a Boyden chamber experiment in SKBR3 and AU565. When the HER2 gene was transfected into MCF7, the number of both lamellipodia and migrated cells was increased. This enhancement of migration did not occur in the presence of extracellular matrix, and zymographic analysis showed no clear difference between HER2 gene-transfected cells and MCF7 cells. Immunohistochemical analysis of 115 cases of breast cancer revealed that coexpression of WAVE2 and Arp2 was significantly correlated with HER2-overexpression (P < 0.0001). These data indicate that an abnormal signal resulting from HER2 gene amplification activates lamellipodia formation in breast cancer cells, which initiates their metalloproteinase-independent migration.

Radiation quality-dependent bystander effects elicited by targeted radionuclides

The efficacy of radiotherapy may be partly dependent on indirect effects, which can sterilise malignant cells that are not directly irradiated. However, little is known of the influence of these effects in targeted radionuclide treatment of cancer. We determined bystander responses generated by the uptake of radioiodinated iododeoxyuridine ([*I]IUdR) and radiohaloanalogues of meta-iodobenzylguanidine ([*I]MIBG) by noradrenaline transporter (NAT) gene-transfected tumour cells. NAT specifically accumulates MIBG. Multicellular spheroids that consisted of 5% of NAT-expressing cells, capable of the active uptake of radiopharmaceutical, were sterilised by treatment with 20 kBqmL(-1) of the alpha-emitter meta-[211At]astatobenzylguanidine ([211At]MABG). Similarly, in nude mice, retardation of the growth of tumour xenografts containing 5% NAT-positivity was observed after treatment with [131I]MIBG. To determine the effect of subcellular localisation of radiolabelled drugs, we compared the bystander effects resulting from the intracellular concentration of [131I]MIBG and [131I]IUdR (low linear energy transfer (LET) beta-emitters) as well as [123I]MIBG and [123I]IUdR (high LET Auger electron emitters). [*I]IUdR is incorporated in DNA whereas [*I]MIBG accumulates in extranuclear sites. Cells exposed to media from [131I]MIBG- or [131I]IUdR-treated cells demonstrated a dose-response relationship with respect to clonogenic cell death. In contrast, cells receiving media from cultures treated with [123I]MIBG or [123I]IUdR exhibited dose-dependent toxicity at low dose but elimination of cytotoxicity with increasing radiation dose (i.e. U-shaped survival curves). Therefore radionuclides emitting high LET radiation may elicit toxic or protective effects on neighbouring untargeted cells at low and high dose respectively. It is concluded that radiopharmaceutical-induced bystander effects may depend on LET of the decay particles but are independent of site of intracellular concentration of radionuclide.

The Human Lung Cancer Drug Resistance-Related Gene BC006151 Regulates Chemosensitivity in H446/CDDP Cells

This study aimed to investigate the mechanism by which the human lung cancer drug resistance-related gene BC006151 regulates chemosensitivity by down-regulating BC006151 expression via antisense gene transfer in H446/(C)DDP cells. A retroviral vector containing the antisense BC006151 sequence was constructed and transfected into H446/(C)DDP cells. Transfection of the empty vector served as a negative control. The two groups of transfected cells were treated with various chemotherapeutic agents, after which morphological changes in cell ultrastructure were compared by transmission electron microscopy, cell proliferation and chemosensitivity to particular chemotherapeutic agents were compared by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method, the effects of chemotherapy on cell cycle and apoptosis were compared by flow cytometry, and Bcl-2 was evaluated by immunohistochemistry and Western blot analysis. Results showed that apoptotic body-like structures were identified by transmission electron microscopy in the antisense gene-transfected cells. MTT founded that these cells exhibited a significantly lower level of proliferation than the control cells (p<0.01), together with a markedly increased sensitivity to various chemotherapeutic agents (p<0.01). Flow cytometry analysis revealed that a G1 phase arrest accounted for the reduction in proliferation in the antisense gene-transfected cells; increased apoptosis was also detected (p<0.01). Both immunohistochemistry and western blot analysis confirmed that Bcl-2 expression was significantly down-regulated in the antisense gene-transfected cells compared to controls. In a word, down-regulation of BC006151 can significantly inhibit proliferation and increase apoptosis of H446/(C)DDP cells after chemotherapy, and this gene may play an important role in the development of multidrug resistance in lung cancer.

Influenza C Virus NS1 Protein Upregulates the Splicing of Viral mRNAs

Pre-mRNAs of the influenza A virus M and NS genes are poorly spliced in virus-infected cells. By contrast, in influenza C virus-infected cells, the predominant transcript from the M gene is spliced mRNA. The present study was performed to investigate the mechanism by which influenza C virus M gene-specific mRNA (M mRNA) is readily spliced. The ratio of M1 encoded by a spliced M mRNA to CM2 encoded by an unspliced M mRNA in influenza C virus-infected cells was about 10 times larger than that in M gene-transfected cells, suggesting that a viral protein(s) other than M gene translational products facilitates viral mRNA splicing. RNase protection assays showed that the splicing of M mRNA in infected cells was much higher than that in M gene-transfected cells. The unspliced and spliced mRNAs of the influenza C virus NS gene encode two nonstructural (NS) proteins, NS1(C/NS1) and NS2(C/NS2), respectively. The introduction of premature translational termination into the NS gene, which blocked the synthesis of the C/NS1 and C/NS2 proteins, drastically reduced the splicing of NS mRNA, raising the possibility that C/NS1 or C/NS2 enhances viral mRNA splicing. The splicing of influenza C virus M mRNA was increased by coexpression of C/NS1, whereas it was reduced by coexpression of the influenza A virus NS1 protein (A/NS1). The splicing of influenza A virus M mRNA was also increased by coexpression of C/NS1, though it was inhibited by that of A/NS1. These results suggest that influenza C virus NS1, but not A/NS1, can upregulate viral mRNA splicing.

Targeted Anti-Tumor Research of Mesenchymal Stem Cells Delivered Enzyme-Prodrug Gene CYP450.

Abstract 3582Poster Board III-519 ObjectiveCytochrome P450(CYP450-CYP1A2 /CYP2B6/CYP2C9) was transfected into human bone marrow-derived mesenchymal stem cells (hBMSCs), and the targed anti-tumor effect of BMSC-CYP450 cooperated with enzyme-prodrug(Dacarbazine (DTIC)/Cyclophosphamide (CPA)) was measured to provide laboratory data base for gene directed enzyme prodrug targeted anti-tumor therapy (GDEPT) which used BMSC as vehicles. MethodsWe respectively cloned CYP1A2/CYP2B6/CYP2C9 cDNA from human liver and constructed recombinant adenovirus vectors(pAd5CMV-NpA-CYP1A2/ pAd5CMV-NpA-CYP2B6/pAd5CMV-NpA-CYP2C9) which titer was 1×1012 pfu/mL. These hBMSCs were separated, cultured, purified, and detected by morphology, flow cytometry, osteogenic, adipogenic and chondrogenic induction, and RT-PCR(A surface marker for the identification of MSCs-the neural ganglioside GD2 gene). The tropism of BMSCs for cancer cells was detected by Transwell inserts technique. These recombinant vectors were transferred into BMSCs and A375/K562 cells, and the expression of EGFP and CYP1A2/CYP2B6/CYP2C9 was detected by fluorescence microscope, RT-PCR and Western blot respectively. Inverted microscope, MTT and Annexin V-FITC/PI detected the anti-tumor effect of CYP450 recombinant adenovirus vectors combined with chemotherapeutic prodrug DTIC/CPA in vitro. A human melanoma(A375) BALB/c nude mice model and a human myelocytic leukemia(K562) BALB/c nude mice model was constructed and detected by immuno-histochemistry analysis. The CYP1A2 gene tranfected BMSCs were injected into the A375 BALB/c nude mice model in combination with DTIC through caudal vein, while CYP2B6/CYP2C9 gene tranfected BMSCs were injected into K562 BALB/c nude mice model in combination with CPA in the same way. The measurement of tumors size, fluorescence microscope and TUNEL were used to detect anti-tumor effect of BMSCs-CYP1A2 cooperating with DTIC and BMSCs-CYP2B6/CYP2C9 with CPA in vivo. ResultsWe constructed the recombinant adenovirus vectors pAd5CMV-NpA-CYP1A2/pAd5CMV-NpA-CYP2B6/pAd5CMV-NpA-CYP2C9 and pAd5CMV-NpA-EGFP successfully. BMSCs was separated successfully, and it respectively showed that BMSCs can migrate through the polycarbonate filter toward K562 and A375 cells in the lower chamber in vitro. Fluorescence microscope detected the expression of EGFP, while both RT-PCR and Western blot detected high expression of CYP1A2/CYP2B6/CYP2C9 in gene-transfected group cells. Inverted microscope, MTT and Annexin V-FITC/PI confirmed that BMSCs transferred with CYP1A2/CYP2B6/CYP2C9 recombinant adenovirus vectors could activate DTIC/CPA and increase its anti-tumor effect(In the DTIC/CPA concentration(0.05 mmol/L/2.5 mmol/L) which BMSCs was relatively safe, the cell apoptosis was (38.38±2.27)% (P<0.01), (42.69±2.03)% (P<0.01) and (39. 51±1.94)% (P<0.01) in BMSCs-CYP1A2+A375 group, BMSCs-CYP2B6+K562 group and BMSCs-CYP2C9+K562 group respectively. ). A375 and K562 BALB/c nude mice model was constructed successfully. The sizes of the tumor in the nude mice treated with transfected BMSCs and DTIC/CPA were significantly smaller than control case and changed along with concentration(P< 0.01, P< 0.05).BMSCs was congregated to tumor site in fluorescence microscope. Apoptosis of tumor cells was conspicuously more in BMSCs-CYP1A2+A375/BMSCs-CYP2B6+K562/BMSCs-CYP2C9+K562 treatment group than in control group by TUNEL. ConclusionBMSCs had the tropism for cancer cells in vitro and vivo. DTIC can be catalyzed by CYP2E1/CYP1A2, while CPA by CYP2B6/CYP2C9 in vitro and vivo. BMSC-based enzyme prodrug system of CYP2E1/CYP1A2 and DTIC can induce A375 cells apoptosis, while BMSC-based enzyme prodrug system of CYP2B6/CYP2C9 and CPA can induce K562 cells apoptosis in vitro and targetedly in vivo. Disclosures:No relevant conflicts of interest to declare.

Transfected Single-Cell Imaging by Scanning Electrochemical Optical Microscopy with Shear Force Feedback Regulation

Gene-transfected single HeLa cells were characterized using a scanning electrochemical/optical microscope (SECM/OM) system with shear-force-based probe-sample distance regulation to simultaneously capture electrochemical, fluorescent, and topographic images. The outer and inner states of single living cells were obtained as electrochemical and fluorescent signals, respectively, by using an optical fiber-nanoelectrode probe. A focused ion beam (FIB) was used to mill the optical aperture and the ring electrode at the probe apex (the inner and outer radii of the ring electrode were 37 and 112 nm, respectively). To apply an appropriate shear force between the probe tip and the living cell surface, we optimized the amplitude of oscillation of the tuning fork to which the probe was attached. Field-programmable gate arrays (FPGA) were adopted to drastically increase the feedback speed of the tip-sample distance regulation, shorten the scanning time for imaging, and enhance the accuracy and quality of the living cell images. In employing these improvements, we simultaneously measured the cellular expression activity of both secreted alkaline phosphatase outside and GFP inside by using the SECM/OM with shear force distance regulation.

Survivin-3B Gene Decreases the Invasion-Inhibitory Effect of Colon Cancer Cells With 5-Fluorouracil

The expression of survivin molecules has been confirmed in many types of cancer cells, including colon cancer cells, and they are considered important antiapoptotic molecules. Recent studies have revealed the existence of different splicing forms of survivin molecules; however, no studies have examined their expression in gastrointestinal cancers. In 2004, we reported the existence of the survivin-3B gene, a novel splice variant of survivin. In this study, we investigated the relationship between human colon cancer and our recently cloned survivin-3B gene with a coding region of 594 bp. In the first examination, survivin-3B expression was analyzed by RT-PCR in human colon cancer and adjacent normal mucosal tissues. The associations of its expression status with clinicopathological parameters and the prognosis were also examined. Survivin-3B mRNA expression was observed in 37 (46.3%) of 80 primary colon cancers, but not in the adjacent normal colonic mucosal tissue. The rate of survivin-3B gene expression was significantly higher in colon cancer with serosal invasion. The 5-year survival rate of patients with survivin-3B gene-positive primary colon cancer was significantly poorer, at 48.7%, than that (75.4%) of survivin-3B gene-negative patients. In the second examination, after the introduction of the survivin-3B gene into cells of the colon cancer cell line DLD-1, 5-fluorouracil-induced changes in their invasive capacity was examined. The invasion-inhibitory effect of 5-fluorouracil on survivin-3B gene-transfected DLD-1 cells was significantly lower than their empty vector gene-transfected counterparts. We speculate that survivin-3B expression in colon cancer is an important factor involved in the invasive capacity of cancer cells in the presence of anticancer drug.

The lactate dehydrogenase-elevating virus capsid protein is a nuclear–cytoplasmic protein

Arteriviruses replicate in the cytoplasm and do not require the nucleus function for virus multiplication in vitro. However, nucleocapsid (N) protein of two arteriviruses, porcine reproductive respiratory syndrome virus and equine arteritis virus, has been observed to localize in the nucleus and nucleolus of virus-infected and N-gene-transfected cells in addition to their normal cytoplasmic distribution. In the present study, the N protein of lactate dehydrogenase-elevating virus (LDV) of mice was examined for nuclear localization. The subcellular localization of LDV-N was determined by tagging N with enhanced green fluorescence protein (EGFP) at the N- and C-terminus. Both N-EGFP and EGFP-N fusion proteins localized to the nucleus and nucleolus of gene-transfected cells. Labeled N also accumulated in the perinuclear region, the site of virus replication. The LDV-N sequence contains a putative ‘pat4’-type nuclear localization signal (NLS) consisting of 38-KKKK. To determine its functional significance, a series of deletion constructs of N were generated and individually expressed in cells. The results showed that the ‘pat4’ NLS was essential for nuclear translocation. In addition, the LDV-N interacted with the importin-α and -β proteins, suggesting that the LDV-N nuclear localization may occur via the importin-mediated nuclear transport pathway. These results provide further evidence for the nuclear localization of N as a common feature within the arteriviruses.

The effects of HBx gene on the expression of DNA repair enzymes hOGG1 and hMYHα mRNA in HepG2 cells

To observe the alteration in the expression of DNA repair enzymes hOGG1 and hMYHalpha and the change in 8-OHdG levels in the HBx gene-transfected cells HepG2/HBx and to explore the mechanisms of the HBV-associated hepatocellular carcinoma, the gene-transfected cells HepG2/HBx which stably expressed HBx was established, and the effect of HBx on the cell cycle and proliferation of HepG2 was examined. By using the beta-actin as the interior control, real-time polymerase chain reaction (Real-time qPCR) was employed to quantitatively detect the expression of DNA repair enzymes hOGG1 and hMYHalpha in the HepG2/HBx, the control cells HepG2 and HepG2 transfected with pcDNA3.1 vector (HepG2/pDNA3.1). The 8-OHdG levels were determined by HPLC/ECD in the established gene-transfected cells HepG2/HBx and the control cells HepG2 and HepG2/pcDNA3.1. Our results showed that the expression of DNA repair enzyme hMYHalpha in the HepG2/HBx (0.021+/-0.007) was significantly lower than that of HepG2 (0.099+/-0.041) (P<0.05) and HepG2/pDNA3.1 (0.121+/-0.005) (P<0.05). However, the no significant differences existed in the expression of DNA repair enzyme hOGG1 among the three cell strains (P>0.05). The 8-OHdG level in the HepG2/HBx was significantly higher than that in HepG2 and HepG2/pcDNA3.1 (P<0.05). It is concluded that HBx gene may inhibit the expression of DNA repair enzyme hMYHalpha mRNA to impair the ability to repair the intracellular DNA oxidative damage, to increase the oxidative DNA-adduct 8-OHdG and to affect the nucleotide excision repair function, thus participate in the occurrence and development of hepatocellular carcinoma.

Saturation of Multidrug-Resistant Protein 2 (Mrp2/Abcc2)-Mediated Hepatobiliary Secretion: Nonlinear Pharmacokinetics of a Heterocyclic Compound in Rats after Intravenous Bolus Administration

Multidrug-resistant protein 2 (MRP2/ABCC2), expressed on the canalicular membrane of hepatocytes, mediates the secretion of conjugated or nonconjugated compounds into bile and plays an important role in physiology and drug elimination. A heterocyclic compound, BPCPU [1-(1-(4-bromophenyl)-3-carbamoyl-1H-pyrazol-4-yl) urea], which was metabolically stable in vitro in rat liver microsomes and freshly isolated rat hepatocytes, demonstrated a saturable nonlinear pharmacokinetic profile in the rat. Polarized efflux was observed for this compound in Caco-2 cells, with a low K(m) = 1.06 +/- 0.06 microM. The Caco-2 efflux was dose-dependent and saturable. Coadministration of 25 microM MK571 ([3-[[3-[2-(7-chloroquinolin-2-yl)vinyl]phenyl]-(2-dimethylcarbamoylethylsulfanyl)methylsulfanyl] propionic acid]), an MRP inhibitor, blocked the polarized efflux in Caco-2 cells. In contrast, this compound did not inhibit calcein efflux in MRP2 gene-transfected Madin-Darby canine kidney cells, suggesting that it is a substrate, not an inhibitor, of the MRP2/ABCC2 transporter. To investigate the mechanism for the nonlinear pharmacokinetics, bile duct-cannulated rats were used to obtain time profiles of plasma concentration, biliary, and urinary excretion after intravenous administration at various doses. The plasma clearance increased remarkably with decreased dose, from 1.5 ml/min/kg at 5 mg/kg to 14.9 ml/min/kg at 0.05 mg/kg. A dose-dependent biliary excretion also was observed. The results revealed that saturation of hepatobiliary secretion played a role in the dose-dependent changes in total body clearance and biliary clearance. Saturating concentrations of the Mrp2/Abcc2 substrate, BPCPU, causing decreased hepatobiliary clearance could be the major cause for the nonlinear pharmacokinetics observed in rats.

Cytoplasmic expression and specific binding of the V H/V L single domain intrabodies in transfected NIH3T3 cells

Intracellularly expressed antibody fragments (intrabodies) have been utilized as powerful tools not only for clinical applications but also for the functional analysis of proteins inside the cell. Among several types of intrabodies developed so far, single domain types composed of only the variable regions (V H or V L) of antibodies are the smallest and thus the easiest to design. In this study, four types of single domain intrabodies were evaluated against a cytosolic protein, Wiskott–Aldrich syndrome protein (WASP), in gene-transfected NIH3T3 cells. These single domains were composed of the V H and V L region with or without their leader sequences. Although these single domains were expressed at similar levels in NIH3T3 cells, the binding activity to the cytosolic target was higher in the single domain constructs with leader sequences. These results suggest the usefulness of the single domain intrabody constructs to analyze the functional domains of cytosolic proteins in cells.

Discrepant Expression Between mRNA and Protein of HTLV-I Basic Leucine Zipper Factor (HBZ) Makes HTLV-I Infected CD4 Lymphocytes and Adult T Cell Leukemia Cells Less Susceptible to HBZ-Specific Cytotoxic T Lymphocytes

[Background]Adult T cell leukemia (ATL) is caused by human T-cell leukemia virus type 1 (HTLV-1) and still remains one of the chemotherapy-resistant leukemias. Accumulating the successful evidence of allogeneic hematopoietic stem cell transplantation (allo-HSCT), the immunotherapeutic strategy for ATL has become to look promising. The fact that more than half of primary ATL cells lack the immunogenic oncoprotien HTLV-1 Tax has been promoting researchers to find an alternative target antigen to develop the cellular immunotherapy for ATL. Recently, HTLV-1 basic leucine zipper factor (HBZ), which is encoded by the minus strand of HTLV-1 proviral genome and is transcribed from 3'-LTR, has been highlighted as the important molecule in ATL leukemogenesis. Since almost all ATL cells express HBZ mRNA, we attempted to verify whether HBZ can be a target of cellular immunotherapy for ATL.[Methods] At first, we synthesized a variety of HBZ-derived 9 amino acid peptides (9 mer) that are predicted to have high binding affinity to HLA-A*0201 molecule. CD8+ T lymphocytes from an HLA-A*0201+ healthy donor were stimulated with peptide-loaded autologous monocyte-derived mature dendritic cells repetitively. Thereafter, epitope specificity, HLA-restriction, and cytotoxic activity of induced cytotoxic T lymphocytes (CTLs) were determined by standard 51Cr-release assays. HBZ and Tax mRNA expression levels of target cells, including primary ATL cells, HTLV-1-infected cell lines, peripheral blood lymphocytes isolated from HTLV-1 carriers and HTLV-1-uninfected individuals, and K562-A*0201 and C1R-A*0201 cells transfected with HBZ gene, were simultaneously measured by real-time quantitative PCR (RQ-PCR). The relative expression levels of HBZ and Tax mRNA were determined by comparative Ct method, and the results were shown as the relative values to those of HTLV-1-infected cell line MT4. HBZ protein expression was determined by Western blotting using anti-HBZ serum which was produced by immunizing rabbits with purified six-His-tagged HBZ polypeptide corresponding to the bZIP domain of HBZ. The detection of HBZ-specific and Tax-specific CTLs was performed by tetramer assays.[Results] We identified an HBZ-derived 9-mer epitope, HBZ26–34 (GLLSLEEEL), with high binding affinity to HLA-A*0201 measured by using HLA-A*0201 gene-transfected T2 cell. We successfully established an HBZ26–34 peptide-specific CTL clone designated as HBZ-1. HBZ-1 exerted cytotoxicity against HBZ gene-transfected K562-A*0201 and C1R-A*0201 cells, but not against HLA-A*0201-positive HTLV-1-infected cells or ATL cells. HTLV-1 infection and HBZ gene transfection did not alter the HLA class I expression of target cells. Expression levels of HBZ mRNA appeared to be higher in ATL cells, HTLV-1-infected cell lines, and HBZ gene-transfected cells than those in HTLV-1 carrier cells. Abundant HBZ protein expression was detected in only HBZ gene-transfected K562-A*0201 and C1R-A*0201 cells, but HBZ protein expression levels in HTLV-1-infected cell lines and ATL cells appeared to be very low. We further examined Tax-specific and HBZ-specific CTLs in an HLA-A*0201-positive ATL patient who received allo-HSCT from the HLA-identical sibling donor. In this patient, Tax mRNA and HBZ mRNA were similarly expressed in ATL cells; however, only Tax-specific CTLs but not HBZ-specific CTLs were detected in both before and after allo-HSCT at full donor chimerism.[Conclusions] Although HBZ mRNA was apparently detected in all HTLV-1-infected cell lines and ATL cells, HBZ protein in these cells was insufficiently expressed to be recognized by HBZ-specific CTLs. Our observations in a transplanted patient with ATL also suggest that HBZ protein may be less immunogenic due to discrepant expression level between mRNA and protein.

Regulation of M1-receptor mRNA stability by smilagenin and its significance in improving memory of aged rats

The purpose of this work is to study the effect of smilagenin on the mRNA stability of muscarinic receptor subtype 1 (M(1); m1 mRNA) in aged rat brains and its significance in improving memory. The Y-maze avoidance task showed that oral administration of smilagenin significantly improved spatial memory performance in aged rats. Mechanistic studies showed that smilagenin was neither a ligand of the M receptors nor a cholinesterase inhibitor, while radioligand binding assays revealed that smilagenin significantly increased the M(1)-receptor density. The increase of M(1)-receptor density correlated with memory improvement. Real-time polymerase chain reaction (RT-PCR) revealed that the m1 mRNA in m1 gene-transfected CHO cells increased significantly, and the average half-life of m1 mRNA was approximately doubled by smilagenin treatment. These results suggest that smilagenin improves memory of aged rats at least partially by increasing the stability of m1 mRNA. However since the ChAT activity in the cortex of aged rats was also elevated by smilagenin, it cannot be excluded that the increase of intrinsic acetylcholine excretion also plays a role in the memory-improvement effect of smilagenin.

Uptake kinetics and biodistribution of 14C-d-luciferin—a radiolabeled substrate for the firefly luciferase catalyzed bioluminescence reaction: impact on bioluminescence based reporter gene imaging

Firefly luciferase catalyzes the oxidative decarboxylation of D: -luciferin to oxyluciferin in the presence of cofactors, producing bioluminescence. This reaction is used in optical bioluminescence-based molecular imaging approaches to detect the expression of the firefly luciferase reporter gene. Biokinetics and distribution of the substrate most likely have a significant impact on levels of light signal and therefore need to be investigated. Benzene ring (14)C(U)-labeled D-luciferin was utilized. Cell uptake and efflux assays, murine biodistribution, autoradiography and CCD-camera based optical bioluminescence imaging were carried out to examine the in vitro and in vivo characteristics of the tracer in cell culture and in living mice respectively. Radiolabeled and unlabeled D-luciferin revealed comparable levels of light emission when incubated with equivalent amounts of the firefly luciferase enzyme. Cell uptake assays in pCMV-luciferase-transfected cells showed slow trapping of the tracer and relatively low uptake values (up to 22.9-fold higher in firefly luciferase gene-transfected vs. nontransfected cells, p = 0.0002). Biodistribution studies in living mice after tail-vein injection of (14)C-D-luciferin demonstrated inhomogeneous tracer distribution with early predominant high radioactivity levels in kidneys (10.6% injected dose [ID]/g) and liver (11.9% ID/g), followed at later time points by the bladder (up to 81.3% ID/g) and small intestine (6.5% ID/g), reflecting the elimination routes of the tracer. Kinetics and uptake levels profoundly differed when using alternate injection routes (intravenous versus intraperitoneal). No clear trapping of (14)C-D-luciferin in firefly luciferase-expressing tissues could be observed in vivo. The data obtained with (14)C-D-luciferin provide insights into the dynamics of D: -luciferin cell uptake, intracellular accumulation, and efflux. Results of the biodistribution and autoradiographic studies should be useful for optimizing and adapting optical imaging protocols to specific experimental settings when utilizing the firefly luciferase and D: -luciferin system.

Tumour malignancy loss and cell differentiation are associated with induction ofgefgene in human melanoma cells

Gene therapy is a new method used to induce cancer cell differentiation. Our group previously showed that transfection of the gef gene from Escherichia coli, related to cell-killing functions, may be a novel candidate for cancer gene therapy. Its expression leads to cell cycle arrest unrelated to the triggering of apoptosis in MS-36 melanoma cells. To determine the basis of the antiproliferative effect of the gef gene in this cell line. Transmission electron microscopy, apoptosis analysis by confocal microscopy, flow cytometry and immunocytochemical analysis were used. Ultrastructural analysis showed a strikingly different morphology after treatment with dexamethasone and expression of the gef gene, with large accumulations of pigment throughout the cell cytoplasm and presence of melanosomes in different stages of development. High mitochondrial turnover and myeloid bodies, characteristics of neurone cells, were also observed. In addition, both immunocytochemical and indirect immunofluorescence analysis demonstrated a significant decrease in HMB-45, Ki-67 and CD44 antigen expression and an increase in S100 and p53 expression in gef gene-transfected MS-36 melanoma cells that were correlated with the duration of dexamethasone treatment. In the present work, we report that gef gene not only reduces cell proliferation in transfected melanoma MS-36TG cell line but also induces morphological changes clearly indicative of melanoma cell differentiation and a reduction in tumour malignancy. These findings support the hypothesis that the gef gene offers a new approach to differentiation therapy in melanoma.

Absolute quantification of multidrug resistance-associated protein 2 (MRP2/ABCC2) using liquid chromatography tandem mass spectrometry

The multidrug resistance-associated protein 2 (MRP2/ABCC2) plays an important role in hepatobiliary efflux of many drugs and drug metabolites and has been reported to account for dramatic interspecies differences in the aspects of pharmacokinetics. In the present study, an absolute quantification method was developed to quantitatively measure MRP2/ABCC2 using LC-MS/MS for detection of a selective tryptic peptide. A unique 16-mer tryptic peptide was identified by conducting capillary LC nanospray ESI-Q-TOF analysis of the immunoprecipitation-enriched samples of MRP2/ABCC2 following proteolysis with trypsin. The lower limit of quantification was established to be 31.25 pM with the linearity of the standard curve spanned to 2500 pM. Both the accuracy (relative error) and the precision (coefficient of variation) of the method were below 15%. Using this method, we successfully determined the absolute amount of MRP2/ABCC2 protein in MRP2/ABCC2 gene-transfected MDCK cells as well as the basal levels of canine Mrp2/Abcc2 protein in MDCK cells. Our findings also demonstrate that the sensitivity of this method exceeds the sensitivity of immunoblotting assay which was not able to detect the basal levels of canine Mrp2/Abcc2 in MDCK cells. The method could be directly applicable to many current research needs related to MRP2/ABCC2 protein.