Phase II study of irinotecan, 5-fluorouracil (5-FU) and leucovorin combination chemotherapy in taxane and cisplatin-based chemotherapy-refractory metastatic gastric cancer

e15599

Background: The role of the second line chemotherapy in advanced gastric cancer was not clear, but possibility of prolongation of survival is open question. Irinotecan is promising agents in gastric cancer and this phase II study evaluated the efficacy and safety of combination chemotherapy with irinotecan, high dose of 5-fluorouracil (5-FU) and leucovorin in taxane and cisplatin based chemotherapy refractory metastatic gastric cancer. Methods: Eligible criteria were as followed; histologic confirmed adenocarcinoma of stomach, previously treated with taxane and cisplatin, age≥18, Eastern Clinical Oncology Group (ECOG) performance status of 1 or less, adequate organ function. Irinotecan (150 mg/m2) as a 30-min infusion and leucovorin (200 mg/m2) as a 15-min infusion were given on day 1, followed by 5-FU 400 mg/m2bolus infusion then 5-FU 2,400 mg/m2 as a 48-hour continuous infusion. This cycle was repeated every 2 weeks until disease progression or unacceptable toxicities. Results: Thirty-four patients were enrolled. The median age was 57 years (range 27–73 years), and the ECOG performance status of all patients was 1. All patients were evaluable for safety and survival and twenty seven patients (79.4%) were evaluable for tumor response. The overall response rate was 18.5% (95% CI: 3.9–33.1). The median progression free survival and overall survival were 4.6 (95% CI: 2.4–6.9) and 9.3 months (95% CI: 5.2–13.4), respectively. Greater than grade 3 haematological toxicities were neutropenia in nine (26.5%), febrile neutropenia in one (2.9%) and thrombocytopenia in one patient (2.9%). The major non-haematological toxicity was asthenia, but most of patients showed grade 1 or 2. Greater than grade 3 non- haematological toxicities were elevated AST/ALT in four (11.8%), hyperbilirubinemia in two (5.9%), nausea in two patients (5.9%). Conclusions: This results showed that the combination chemotherapy with irinotecan, 5-FU and leucovorin was well tolerated and active in taxane and cisplatin refractory patients.

No significant financial relationships to disclose.

Phase II study of S-1 monotherapy in taxane, cisplatin refractory gastric cancer

4551

Background: S-1 is a fourth-generation oral fluoropyrimidine that was developed to mimic protracted continuous infusion of 5-fluorouracil (5-FU). In previous study, S-1 demonstrated promising activity which is comparable to combination chemotherapy in advanced gastric cancer. This phase II study evaluated the efficacy and safety of S-1 salvage chemotherapy, in patients with taxane and cisplatin refractory gastric cancer. The primary end point was progression free survival and secondary end points were overall survival, safety and clinical benefit. Methods: Patients were eligible if they had histologically documented gastric adenocarcinoma previously treated with taxane (docetaxel or paclitaxel) and cisplatin; age≥18; Eastern Clinical Oncology Group (ECOG) performance status of 2 or less; adequate organ function; no evidence of gastrointestinal obstruction or passage disturbance. S-1 treatment was performed according to BSA as followed; < BSA 1.25, 80 mg/day, 1.25 ≤ BSA < 1.5, 100 mg/day; BSA ≥ 1.5, 120 mg/day. Every dosage was delivered divided two times and administered for 4 weeks followed by 2 weeks of resting period. Treatment continued until progression of disease or life-threatening adverse events were occurred. Results: Fifty-four patients were enrolled in this study and of the patients, forty-eight patients were evaluable. A total 194 chemotherapy cycles were administered and median number of cycles was three. Four (8.3%) patients had a partial response and 18 (37.5%) patients had stable disease. The median progression free survival and overall survival were 3.8 and 10.2 months, respectively. Grade III/IV hematologic toxicities included neutropenia in 6 patients (12.5%) and there was no febrile neutropenia. Most of nonhematologic toxicities were diarrhea, asthenia, and mucositis, and there was no grade 3 or grade 4 except two patients, who developed grade 3 anorexia and diarrhea, respectively. The clinical benefit response was observed in 16 patients (33.3%). Conclusions: This results showed that S-1 monotherapy was active and safe salvage chemotherapy in patients with advanced gastric cancer previously treated with taxane and cisplatin.

No significant financial relationships to disclose.

Combination treatment with arsenic trioxide and sulindac enhances apoptotic cell death in lung cancer cells via activation of oxidative stress and mitogen-activated protein kinases

Arsenic trioxide (As2O3) has been introduced to the treatment of acute promyelocytic leukemia (APL), and has also been shown to induce apoptosis in a variety of solid tumor cell lines, including non-small cell lung cancer. However, the prohibitively high concentration required for the induction of apoptotic cell death in many solid tumor cells is unacceptable for clinical utilization due to the excessive toxicity associated with this dose. Sulindac is known to enhance the cellular responsiveness of tumors toward chemotherapeutic drugs. Herein, we demonstrated that combination treatment with As2O3 and sulindac resulted in a synergistic augmentation of cytotoxicity in H157 lung cancer cells, which was revealed by apoptotic induction as demonstrated by an increase in the sub-G0/G1 fraction. In addition, combination treatment with As2O3 and sulindac increased reactive oxygen species (ROS) and oxidative stress, as evidenced by the heme oxygenase-1 (HO-1) expression and mitogen-activated protein kinase (MAPK) phosphorylation. MAPK inhibitors blocked the induction of HO-1 by combination treatment. Inhibitors of p38 and JNK partially inhibited the augmented cell death whereas the ERK inhibitor showed poor inhibition. Combination treatment with As2O3 and sulindac induced oxidative DNA damage in a time-dependent fashion, which was evaluated by H2AX phosphorylation along with HO-1 induction.

35 IN VITRO DEVELOPMENT OF NUCLEAR TRANSFER EMBRYOS DERIVED FROM PORCINE EMBRYONIC GERM CELLS AND THEIR DESCENDENT NEURAL PRECURSOR CELLS

Due to an ease of reprogramming in the process of nuclear transfer (NT), undifferentiated stem cells may support greater development of cloned embryos compared with differentiated cell types. Hence, stem cells may be more suitable as nuclear donor cells for NT procedures than somatic cells. In pigs, comparative studies of NT using stem cells and their differentiated descendant cells have not yet been reported. Embryonic germ (EG) cells are undifferentiated stem cells isolated from cultured primordial germ cells (PGC) and can differentiate into several cell types. In this study, in vitro development of NT embryos using porcine EG cells and their derivative neural precursor (NP) cells was investigated. Porcine EG cells were isolated from cultured PGC collected from embryos on Day 23 of gestation (Shim et al. 1997 Biol. Reprod. 57, 1089–1095). Neural precursor cells, based on morphology of neural rosettes or neurospheres, were differentiated from porcine EG cells by sequential culture of the cells on gelatinized dishes in N2B27 medium with and without 10 µm retinoic acid for 7 days each. Since porcine EG cells and NP cells differentiated from the same EG cells were used in the present study, the genetic makeup of nuclear donor cells was identical, eliminating any genetic variation between undifferentiated and differentiated cells in the comparison. The efficiencies of NT using the two different cell populations were compared. The rates of fusion were not different between NT embryos from EG and NP cells. However, the rate of cleavage in NT embryos from EG cells was significantly higher (P < 0.05) than that from NP cells (141/247, 57.1% v. 105/228, 46.1%). Similarly, the rate of blastocyst development was significantly higher (P < 0.05) in NT using EG cells than that using NP cells (43/247, 17.4% v. 18/228, 7.9%). The effects on NT efficiency using either stem cells or their differentiated progeny is still controversial. The rates of blastocyst development using somatic stem cells were either reduced in mice (Sung et al. 2006 Nat. Genet. 38, 1323–1328) or remained the same in deer (Berg et al. 2007 Biol. Reprod. 77, 384–394) and cattle (Green et al. 2007 Biol. Reprod. 77, 395–406). However, the results obtained from the present study in pigs demonstrate a reduced capability for nuclear donor cells to be reprogrammed following the differentiation of porcine EG cells. This suggests that the effect on NT efficiency by using stem cells and their differentiated progeny may vary depending upon the species and cell types involved.

277 ESTABLISHMENT OF EMBRYONIC STEM CELL LINES DERIVED FROM A EGFP-TRANSGENIC MOUSE AND THEIR SURVIVAL IN THE COCHLEA OF C57BL/6 MICE

Embryonic stem (ES) cells isolated from inner cell mass cells of blastocyst-stage embryos are capable of differentiating into various cell lineages. Transplantation of these cells may potentially be a treatment for many degenerative diseases. Such cell therapy has often been tested using allografts of ES cells in mice. However, it has been difficult to locate transplanted ES cells and to avoid the rejection of allogeneic ES cells by the host. The aims of this study were to establish ES cell lines ubiquitously expressing enhanced green fluorescent protein (EGFP) and to test survival of ES cells in allografts into the cochlea of inbred C57BL/6 mice. Nine hatched blastocysts collected from a C57BL/6-green mouse that ubiquitously expresses transgene EGFP were plated onto an inactivated STO feeder layer. Two putative ES-like colonies were obtained from the plated blastocysts, and repeated subculture of these colonies produced two cell lines expressing EGFP. The cell lines possessed typical characteristics of ES cells, including densely packed colonies of the cells with prominent nucleoli, a high nuclear-cytoplasmic ratio, and high alkaline phosphatase activity. In suspension culture, these cells formed simple and cystic embryoid bodies. Undifferentiated EGFP-transgenic ES cells (106 cells per mouse) were injected into the cochlea of five C57BL/6 mice deafened by gentamycin treatment. Although no behavioral changes were noticed until four weeks after the transplantation, histological study revealed that grafted cells survived in the scala media of all injected mice. Incorporation of the cells expressing EGFP into the host was found along the auditory nerve fibers close to the organ of Corti. Such incorporation was also discovered in the area of the spiral ganglion neurons, cochlear sensory epithelia, and stria vascularis. Morphology and size of the cells varied depending on their sites of incorporation. The results from the present study demonstrate that, due to their survival in transplantation without allogeneic rejection as well as ubiquitous and stable expression of EGFP, ES cells from an EGFP-transgenic mouse may be a useful means of studying cell therapy.

Phase II study of paclitaxel, cisplatin, and 5-FU combination chemotherapy in patients with advanced gastric cancer

15052

Background: Taxane has been used widely in advanced gastric cancer, but toxicities are problematic. To avoid the bone marrow suppression, docetaxel could be replaced paclitaxel to reduce bone marrow suppression and to improve the efficacy, we planned to augmentation of the dose intensity. This phase II study evaluated the efficacy and safety of combination chemotherapy with paclitaxel, cisplatin, and 5-fluorouracil (5-FU) in advanced gastric cancer. Methods: Patients with histologically confirmed gastric adenocarcinoma, ECOG PS = 2, at least one measurable lesion and adequate organ functions were eligible. Paclitaxel (175 mg/m2) and cisplatin (75 mg/m2) were given as a 1-h intravenous infusion on day 1, followed by 5-FU (750 mg/m2) as a 24-h continuous infusion for 5 days. This cycle was repeated every 3 weeks. Results: Forty-five eligible patients (median age 56 years) were treated in this way. Of the 41 patients in whom efficacy was evaluable, an objective response rate (ORR) was seen in 20 (48.8%), a complete response in two, and a partial response in 18 patients. The median time to progression was 6.9 months (95% CI, 5.86–7.94), and the median overall survival was 13.1 months (95% CI, 8.83–17.37). The main hematological toxicity was neutropenia and greater than grade 3 neutropenia was observed in 67 cycles (25%). Febrile neutropenia developed in three patients (7.3%). The major non-hematological toxicities were asthenia and peripheral neuropathy, but grade 3 or 4 toxicity was not seen. Conclusions: The combination chemotherapy with paclitaxel, cisplatin, and 5-FU is a promising regimen, and was well tolerated in patients with advanced gastric cancer.

No significant financial relationships to disclose.

Utilization of an alternative Communication Device using the Anal Sphincter (CDAS)

The purpose of this study was to invent a new communication system for terminal amyotrophic lateral sclerosis (ALS) patients who are in a state of complete motor paralysis with intact sensory and cognitive functions whose speech are disrupted due to the weakness of muscles involved in speaking and/ or to tracheostomy and ventilator dependence.

23 HYPOMETHYLATION OF DNA IN NUCLEAR TRANSFER EMBRYOS FROM PORCINE EMBRYONIC GERM CELLS

Epigenetic modification including genome-wide DNA demethylation is essential for normal embryonic development. Insufficient demethylation of the somatic cell genome may cause various anomalies and prenatal loss in the development of nuclear transfer embryos. Species-specific differences in the epigenetic status of cloned donor genomes have been reported. A level of DNA methylation in porcine somatic cell nuclear transfer (SCNT) embryos was similar to that of normally fertilized embryos, but hypermethylation of DNA in bovine SCNT embryos was commonly observed (Kang et al. 2001 J. Biol. Chem. 276, 39 980-39 984). Even in the same species, the source of the nuclear donor often affects later development of nuclear transfer embryos. In this study, appropriateness of porcine embryonic germ (EG) cells as karyoplasts for nuclear transfer with respect to epigenetic modification was investigated. These cells follow the methylation status of the primordial germ cells from which they originated, so they may contain a less methylated genome than somatic cells. The rates of blastocyst development were similar among embryos from EG cell nuclear transfer (EGCNT), SCNT, and intracytoplasmic sperm injection (ICSI) (16/62, 25.8% vs. 56/274, 20.4% vs. 16/74, 21.6%, respectively). Genomic DNA samples from EG cells (n = 3), fetal fibroblasts (n = 4), and blastocysts from EGCNT (n = 8), SCNT (n = 14), and ICSI (n = 6) were isolated and treated with sodium bisulfite. The satellite region (GenBank Z75640) that involves 9 selected CpG sites was amplified by PCR, and the rates of DNA methylation in each site were measured by pyrosequencing technique (Biotage AB, Uppsala, Sweden). The average methylation degrees of CpG sites in EG cells, fetal fibroblasts, and blastocysts from EGCNT, SCNT, and ICSI were 17.9, 37.7, 4.1, 9.8, and 8.9%, respectively. The genome of porcine EG cells was less methylated than that of somatic cells (P &lt; 0.05), and DNA demethylation occurred in embryos from both EGCNT (P &lt; 0.05) and SCNT (P &lt; 0.01). However, the degree of DNA methylation in EGCNT embryos was approximately one-half that of SCNT (P &lt; 0.01) and ICSI (P &lt; 0.05) embryos; in SCNT and ICSI embryos, the genome was demethylated to the same degree. The present study demonstrated that porcine EG cell nuclear transfer results in hypomethylation of DNA in cloned embryos, yet leading to normal pre-implantation development. However, it would be interesting to further investigate whether such modification affects long-term survival of cloned embryos.

Backwash based methodology for the estimation of solids retention time in biological aerated filter

The concept of solids retention time (SRT) was used for describing the growth of biofilm in a biological aerated filter (BAF) system. The SRT profile was obtained from the change in solids accumulation, estimated from the head loss profile data before and after backwash using the Carmen-Kozeny equation. The SRT profile along the filter bed depth showed the SRT of about 2 days for the lower layer and about 6 days for the upper layer. The overall SRT was determined by the direct estimation of excess solids mass during backwash and of solids retained in the filter bed. The ideal characteristic SRT distribution was maintained by regular backwash, for organic removal and nitrification. The SRT for high organic removal and nitrification is demonstrated by the SRT distribution along the filter bed in this BAF process.

Phase II study of concurrent S-1/cisplatin and radiation therapy in locally advanced or metastatic esophageal cancer

14154

Background: Although 5-FU and cisplatin had been widely used as radiosensitizer, the toxicities such as mucositis or bone marrow suppression were problematic. In this study, 5-FU was replaced with S-1. The primary end point of this study was to define the safety and the secondary end point was to evaluate the pathologic response and clinical efficacy as the first line therapy in locally advanced or metastatic esophageal cancer. Methods: Patients with locally advanced or metastatic esophageal cancer without history of previous chemotherapy or radiotherapy were eligible. Cisplatin was given intravenously with 75 mg/m2 on day 1 every 3 weeks. S-1 was administered at the dose of 80 mg/m2/day orally divided two times for 2 weeks followed by 1 week rest. Radiotherapy was started concomittently at day 1, total dose of 5040 cGY for 6 weeks. During radiotherapy, patients received 2 cycles of chemotherapy. Results: From May 2004 to Aug 2005, 33 patients were enrolled into this study. 6 patients were dropped out due to poor compliance (3), economic problem (2) and TEF (1) during treatment. 27 patients were evaluable for response and toxicity. The median age was 66 years (range, 54–82). Clinical response was 77.8% (21 pts) and pathologic response was shown in 29.6% (8 pts). The improvement of dysphagia was shown in 22 patients (81.5%). There were 7 (25.9%) pts with grade 3 neuropenia. Grade 3–4 odynophagia during concurrent chemoradiotherapy was observed only one patient. Conclusions: The concurrent chemoradiotherapy combined with S-1 and cisplatin was well tolerated and effective in advanced esophageal cancer to relieve obstructive symptoms and tumor regression.

No significant financial relationships to disclose.

20 PRODUCTION OF NUCLEAR TRANSFER EMBRYOS FROM PORCINE FETAL FIBROBLAST CELLS CARRYING A TETRACYCLINE-INDUCIBLE TRANSGENE

Constitutive expression of A transgene often results in serious physiological disturbances in transgenic animals. For instance, systemic overexpression of human growth hormone in transgenic pigs has resulted in detrimental side effects in general health and reproductive performance. One of the solutions to such problem would be inducible expression of a transgene that may restrict production of foreign proteins from transgenic animals only when needed. In this study, a retrovirus vector was designed to express the green fluorescent protein (GFP) gene under the control of the tetracycline-inducible promoter. Transformation of porcine fetal fibroblast cells was achieved by infection of the cells with the vector and subsequent antibiotic selection. To induce transgene expression, transformed porcine fetal fibroblast cells were cultured in medium supplemented with doxycycline for 48 h. Induction of the GFP gene was verified by the emission of fluorescence from transformed cells. Nuclei of transformed cells with or without doxycycline treatment were transferred into enucleated oocytes, and the induction efficiency was analyzed by monitoring fluorescent emission during development of reconstituted embryos to the blastocyst stage. In addition, differences in the rates of blastocyst development between experimental groups were analyzed by Student's t-test. Blastocyst formation of nuclear transfer embryos using transformed cells with tetracycline-inducible retrovirus vector (12.0%, 128/1072) was not significantly different (P > 0.05) from that with non-inducible control vectors (13.7%, 41/300), suggesting that an introduction of tetracycline-inducible retrovirus vector was not particularly harmful to the development of nuclear transfer embryos. Also, the blastocyst development rate of nuclear transfer embryos after induction of transgene by doxycycline (12.1%, 99/815) was not significantly different (P > 0.05) from that of the non-induced counterparts (11.3%, 29/257), suggesting that the induction of transgene did not affect the development of transgenic clone embryos. In a majority of embryos, high expression of the GFP gene was observed in cloned embryos with transgene induction, whereas poor or no GFP expression was detected in non-induced controls. The results from this study suggest that tetracycline-inducible expression of transgenes in nuclear transfer embryos may be used for production of foreign proteins in transgenic animals in a more controlled manner than with conventional procedures. Further experiments on transfer of cloned embryos carrying such an inducible transgene to recipients may enable production of transgenic pigs with fewer side effects from unregulated expression of the transgene.

208 CYTOLYTIC ANALYSIS AND NUCLEAR TRANSFER OF hCD46-TRANSGENIC PORCINE EMBRYONIC GERM CELLS TO DEVELOP AND IN VITRO MODEL OF XENOTRANSPLANTATION

Pigs are considered the most likely source of organs for xenotransplantation due to their anatomical and physiological similarities to humans. Production of transgenic pigs including addition of human complement-regulatory protein genes and deletion of alpha-1,3-galactosyl transferase gene may overcome hyperacute rejection (HAR), the first and currently the most critical immunological hurdle in the development of xenogeneic organs for human transplantation. However, even after resolving HAR in pig-to-human xenotransplantation, a series of other transgenic pigs may be required to alleviate subsequent acute and chronic rejection and incompatibility of porcine proteins to human counterparts. The production of transgenic pigs is not only labor-intensive, time-consuming, and costly, but also the usefulness of such pigs in transplantation to humans is unpredictable. For these reasons, development of a reliable in vitro procedure to pre-evaluate effectiveness of the transgenic approach would be beneficial. This study was preformed to establish an in vitro model of xenotransplantation using porcine embryonic germ (EG) cells, undifferentiated stem cells derived from culture of primordial germ cells. Porcine EG cells were maintained in feeder-free state in DMEM containing 15% (v/v) fetal bovine serum and 1000 units/mL leukemia inhibitory factor. Human complement down-regulator hCD46 (also known as MCP, membrane cofactor protein) gene under the regulation of cytomegalovirus promoter was introduced into porcine EG cells. Transfected cells were selected by antibiotic treatment and confirmed by PCR. To test the resistance of hCD46-transgenic EG cells to human xenoreactive natural antibody and complement, EG cells were cultured for 1.5 days in DMEM containing 15% (v/v) normal human serum. The treatment with human serum did not affect the survival of hCD46-transgenic EG cells, whereas with the same treatment approximately one half of non-transfected EG cells failed to survive (P < 0.01). Transgenic EG cells presumably capable of overcoming HAR were used as nuclear donors for subsequent transfer of nuclei into enucleated oocytes. Among 110 reconstituted oocytes, 19 (17.3%) developed to the blastocyst stage. Analysis of individual nuclear transfer embryos by PCR indicated that 89.5% (17/19) of embryos contained transgene hCD46. The PCR-negative embryos might be due to an incomplete antibiotic selection of cells after transfection. Overall, the results of the present study demonstrate that the cell culture-based model of xenotransplantation may validate the usefulness of particular transgenic pigs prior to actual production. Further experiments on differentiation of transgenic EG cells into various cell types, cytolytic analysis of such cells to assess efficiency of xenotransplantation, and subsequent production and transfer of transgenic clone embryos to recipients may provide a useful new procedure to accelerate xenotransplantation research.

24 TRANSGENESIS AND NUCLEAR TRANSFER USING STEM CELLS FROM CULTURED PORCINE PRIMORDIAL GERM CELLS

Embryonic germ (EG) cells are undifferentiated stem cells isolated from cultured primordial germ cells (PGC). These cells share many characteristics with embryonic stem cells including their morphology and pluripotency. Undifferentiated porcine EG cell lines demonstrating capacities of both in vitro and in vivo differentiation have been established (Shim H et al. 1997 Biol. Reprod. 57, 1089–1095). Since EG cells can be cultured indefinitely in an undifferentiated state, whereas somatic cells in primary culture are often unstable and have limited lifespan, EG cells may provide an inexhaustible source of karyoplasts in nuclear transfer (NT). This would be particularly advantageous in maintaining nuclear donor cells carrying a transgene. In addition, genome-wide demethylation of DNA occurs in pre-implantation embryos as well as PGC. Nuclear transfer embryos using EG cells rather than somatic cells may be close to embryos from normal fertilization in their DNA methylation status. If combined with NT technique, EG cells may potentially be useful for genetic manipulation in pigs. In this study the efficiencies of transgenesis and NT using porcine fetal fibroblast and EG cells were compared. Two different techniques were used to perform NT. When conventional NT procedure (Roslin method) involving fusion of donor cells with enucleated oocytes was used, the rates of development to the blastocyst stage were 16.8% (59/351) and 14.1% (50/354) in EG and somatic cell NT, respectively. In piezo-driven micromanipulation (Honolulu method) involving direct injection of donor nuclei into enucleated oocytes, the rates of blastocyst formation in EG and somatic cell NT were 11.9% (15/126) and 7.5% (12/160), respectively. Although the differences between EG and somatic cell NT were statistically insignificant, the rates of blastocyst development in EG cell NT were comparable to the somatic cell counterpart regardless of NT methods used in the present study. To investigate if EG cells can be used for transgenesis in pigs, GFP gene was introduced into porcine EG cells. Nuclear transfer embryos using transfected EG cells gave rise to blastocysts (29/137, 21.2%), and all embryos that developed to the blastocyst stage expressed GFP, based on observation under fluorescence microscope. In this study, the possibility of using EG cells as karyoplast donors in NT procedure was tested. The results suggest that EG cell NT may be used as an alternative to somatic cell NT, and transgenic pig embryos may be produced using EG cells. This research was supported by a grant (SC14033) from Stem Cell Research Center of the 21st Century Frontier Research Program funded by the Ministry of Science and Technology, Republic of Korea.

331 MODIFIED SINGLE-STRANDED OLIGONUCLEOTIDE-RECOMBINASE COMPLEX MEDIATES GENE TARGETING IN MOUSE EMBRYOS

Gene targeting is an in situ manipulation of an endogenous gene in a precise manner by the introduction of exogenous DNA. The process of gene targeting involves a homologous recombination reaction between the targeted genomic sequence and an exogenous targeting vector. In elucidating the function of many genes, gene targeting has become the most important method of choice. Conventional gene targeting has been achieved through the use of embryonic stem cells. However, such a procedure is often long, tedious, and expensive and has been limited in the mouse only due to a lack of usable embryonic stem cells in other species. This study was carried out to develop a much simplified procedure of gene targeting using E. coli recombinase recA and modified single-stranded oligonucleotides. The new procedure was attempted to modify X-linked hypoxanthine phosphoribosyltransferase (HPRT) gene. The single-stranded oligonucleotide to target exon 3 of HPRT was 74 bases in length and included three phosphorothioate linkages at each terminus (also known as S-oligo) so as to be resistant against exonucleases when introduced into zygotes. The oligonucleotide sequence was homologous to the target gene except for a single nucleotide that induces a mismatch between the introduced oligonucleotide and endogenous HPRT gene. Although the exact mechanism is yet unknown, endogenous repairing of such a mismatch would give rise to the conversion of TAT to TAG stop codon, thereby losing the function of the target gene. Prior to an introduction into zygotes, modified single-stranded oligonucleotides were preincubated with recA recombinase to enhance the homologous recombination. The recA-oligonucleotide complex was microinjected into the pronuclei of zygotes. Individual microinjected embryos that developed to the blastocyst stage were analyzed for the expected nucleotide conversion using PCR and subsequent sequencing. The conversion of TAT to TAG stop codon was confirmed in two embryos among forty tested blastocysts, so that the frequency of gene targeting was approximately 5%. The result suggests that the gene targeting was feasible by this relatively easier direct method. Subsequent transfer of gene-targeted embryos to recipients to obtain transgenic mice missing the function of HPRT gene is underway. Further technical refinement and enhancement of homologous recombination frequency will be required for the practical use of this new approach for gene targeting in mice.

Comparison of influence of free ammonia and dissolved oxygen on nitrite accumulation between suspended and attached cells

The shortcut biological nitrogen removal (SBNR) hybrid (suspended cells combined with attached cells) process is an innovative technology that nitrosofies ammonium to nitrite and then denitrifies nitrite to nitrogen gas. Theoretically, this results in a 25% savings of the oxygen needed for nitrification and a 40% of savings in carbon source needed for denitrification. In this study, the influences of free ammonia (FA) and dissolved oxygen (DO) concentrations on nitrite accumulation were investigated to find the optimal operational factors for stable nitrite accumulation over a long period. The maximum specific utilization rates for ammonium (qa) and nitrite (qn) were determined for suspended and attached cells taken from a bench-scale SBNR reactor and a pilot-scale livestock wastewater treatment plant reactor. For the ammonium and nitrite oxidations in both reactors, the attached cells were more resistant to the FA concentration, but were more significantly influenced by the DO concentration than the suspended cells. In addition, the effect of the DO concentration was more significant than that of the FA concentration for both types of cells from both reactors. In this SBNR hybrid system, a simultaneous manipulation of DO concentration (<1.5 mg l(-1)) and FA concentration (10-20 mg l(-1)) was required for maintaining high levels of nitrite accumulation.

Separation of benzene, toluene, ethylbenzene, and xylenes by micellar electrokinetic capillary chromatography

The use of sodium dodecyl sulfate, urea, beta-cyclodextrin, and methanol as additives to the electrophoretic medium containing a Na2HPO4-boric acid buffer in the micellar electrokinetic capillary chromatography of benzene, toluene, ethylbenzene, and three isomers of xylene (collectively known as BTEX) was investigated. The results showed that with the addition of sodium dodecyl sulfate only, higher selectivity and sensitivity and shorter migration time could be achieved, which consequently resulted in better separation of BTEX studied. For this buffer system, good linearity (R2>0.99) was found over the range of 5 to 500 microg ml(-1) for individual BTEX compound and separation time of less than 5 min for BTEX was possible.

A novel c-Myc-responsive gene, JPO1, participates in neoplastic transformation

We have identified a novel c-Myc-responsive gene, named JPO1, by representational difference analysis. JPO1 responds to two inducible c-Myc systems and behaves as a direct c-Myc target gene. JPO1 mRNA expression is readily detectable in the thymus, small intestine, and colon, whereas expression is relatively low in spleen, bone marrow, and peripheral leukocytes. We cloned a full-length JPO1 cDNA that encodes a 47-kDa nuclear protein. To determine the role of JPO1 in Myc-mediated cellular phenotypes, stable Rat1a fibroblasts overexpressing JPO1 were tested and compared with transformed Rat1a-Myc cells. Although JPO1 has a diminished transforming activity as compared with c-Myc, JPO1 complements a transformation-defective Myc Box II mutant in the Rat1a transformation assay. This complementation provides evidence for a genetic link between c-Myc and JPO1. Similar to c-Myc, JPO1 overexpression enhances the clonogenicity of CB33 human lymphoblastoid cells in methylcellulose assays. These observations suggest that JPO1 participates in c-Myc-mediated transformation, supporting an emerging concept that c-Myc target genes constitute nodal points in a network of pathways that lead from c-Myc to various Myc-related phenotypes and ultimately to tumorigenesis.