Biomedical subjects

C H Shu

Publications and source records attributed to C H Shu.

At least 19 recordsLinked to original sources

PubMed2001

Evaluation of GL331 in combination with paclitaxel: GL331's interference with paclitaxel-induced cell cycle perturbation and apoptosis.

Combination of selecting agents that act on different cellular mechanisms is a common strategy in cancer chemotherapy. GL331 is a new potent topoisomerase II (Topo II) poison; distinctly, paclitaxel is a microtubule-interfering cancer chemotherapeutic agent. In this study, we intended to evaluate the efficacy of combining GL331 with paclitaxel in cell killing and apoptotic induction in nasopharyngeal carcinoma NPC-TW01 cells. By MTT and internucleosomal DNA cleavage assays, we found that pretreatment or simultaneous treatment of NPC-TW01 cells with GL331 could significantly interfere with paclitaxel's cell killing and apoptosis-inducing activity. When the administration schedule was reversed, the cytotoxicity of GL331 was attenuated by paclitaxel pretreatment. The anti-cancer activity produced by combining GL331 with paclitaxel was obviously lower than the addition of the activities of two individual agents. NPC-TW01 cells were treated with GL331 and 3H-labeled paclitaxel simultaneously or with GL331 before 3H-labeled paclitaxel. In both conditions, GL331 did not reduce the [3H]paclitaxel level in the cells, suggesting that GL331's interference with paclitaxel's cell-killing and apoptosis-inducing efficacy did not result from any inhibition of cellular uptake or retention of paclitaxel. In addition, we found that GL331-induced perturbation of cell cycle progression dramatically over-rode the patterns of mitotic arrest induced by paclitaxel, and the mechanism could be the inhibition of cyclin B1/CDC2 kinase and MAD2 checkprotein activities.

Antineoplastic Agents, Phytogenic↗

PubMed2000

Activation of MAD 2 checkprotein and persistence of cyclin B1/CDC 2 activity associate with paclitaxel-induced apoptosis in human nasopharyngeal carcinoma cells.

Paclitaxel (Taxol) is a microtubule-interfering agent that induced persistent and transient G2/M arrest before apoptosis in human nasopharyngeal carcinoma (NPC) cells at high and low concentrations, respectively. In this study, we intended to explore the underlying molecular events and found that cellular cyclin B1/CDC 2 kinase activity was increased and persisted for >6 h upon paclitaxel treatment both at high and low concentrations. Furthermore, activation of MAD 2 checkprotein could account for the loss of cyclin B1 ubiquitination and the persistence of cyclin B1/CDC 2 activation in the cases. To investigate the involvement of cyclin B1 and MAD 2 activation in paclitaxel-induced apoptosis, we introduced affinity-purified anti-cyclin B1 and MAD 2 antibodies into NPC cells by electroporation before the further paclitaxel treatment. The antibodies against cyclin B1 and MAD 2 indeed attenuated paclitaxel-induced cytotoxicity and DNA fragmentation. Our study suggests that activation of cyclin B1/CDC 2 and MAD 2 were the M-phase events required for paclitaxel-induced apoptosis in NPC cells. The dys-regulated cyclin B1/CDC 2 activation could enhance the prometaphase progression, but activation of MAD 2 rendered cells inable to exit from the metaphase. Under this circumstance, cells were probably going to "mitotic catastrophe" and ultimately, destined to apoptosis.

Antibodies↗

PubMed2000

In vitro evaluation of GL331's cancer cell killing and apoptosis-inducing activity in combination with other chemotherapeutic agents.

GL331 is a novel podophyllotoxin-derived compound and is more efficacious than its congener VP-16 in killing several types of cancer cells, that has promoted considerable interest in its possibility of clinical use. In this study, we found that the higher cytotoxicity of GL331 in nasopharyngeal carcinoma NPC-TW01 cells was attributed to the elevated ability to induce apoptotic cell death. In addition to evaluation of GL331's single agent activity, the use of GL331 in combination with other established therapeutic agents was also evaluated. We found that GL331-induced cell cycle perturbation occurred upon initial 8-h exposure, and pretreatment of NPC-TW01 cells with GL331 for 8 h significantly interfered with the cytotoxicities of VP-16, cisplatin, 5-fluorouracil and adriamycin. When the schedule of drug administration was reversed, high-toxic concentrations of these agents revealed an antagonistic effect on GL331; however, their low-toxic doses had the additive or even more-than-additive effect on the cytotoxicity induced by GL331 at 0.1 microM or less, but for GL331 concentrations of greater than 1 microM, the effect became less than additive. These data suggest that overlapping mechanisms could be elicited by GL331 and other agents, and additional preclinical studies are needed to determine the optimal dose combination and administration schedule that will enhance, rather than interfere with, the efficacy of GL331 in combination with other anti-cancer agents.

Antineoplastic Agents, Phytogenic↗

PubMed2000

Salvage surgery for recurrent nasopharyngeal carcinoma.

OBJECTIVE: To evaluate the efficacy of salvage surgery in the treatment of recurrent nasopharyngeal carcinoma (NPC) at the primary site. STUDY DESIGN: A retrospective investigation of the outcome of salvage surgery for 28 patients with recurrent NPC after definite radiation therapy. METHODS: The nasopharynx was approached anteroposteriorly by the transmaxillary approach (maxillary swing, maxillectomy) or inferior approach (midline mandibulotomy or median labiomandibular glossotomy), or laterally by modified facial translocation or transpterygoid approach; intentional ligation of the internal carotid artery was performed after establishment of extracranial-intracranial (EC-IC) bypass in one patient; postoperative irradiation was given to the patients with positive pathological margins. RESULTS: Nine patients lived without disease for 20 to 93 months (mean interval, 52 mo) after surgery; among them, eight patients had T1 tumors that were resected totally by surgery via anteroposterior approaches and the other patient had postoperative irradiation to control the disease. Seven patients had local recurrence 8 to 21 months after treatment. Four patients developed distant metastases, including one patient with a T2b tumor that was totally resected through modified facial translocation approach with ligation of internal carotid artery. Eight patients died of other causes; internal carotid artery blowout was the cause of death in four of these eight patients. CONCLUSIONS: In most cases of recurrence, T1 nasopharyngeal tumors can be resected totally by anteroposterior approaches; for T2 or larger tumors, postoperative irradiation is usually necessary. Otherwise, facial translocation offers a better chance to completely resect the tumors. Internal carotid artery is better ligated if patients have received greater than 70 Gy irradiation or if the artery must be exposed during the surgery. We suggest that EC-IC bypass be used to avoid the possible complications (or cerebral ischemic stroke) caused by ligation of internal carotid artery. The transmaxillary approach is favored in the management of nasopharyngeal tumor recurrence with nasal cavity extension, and midline mandibulotomy is more suitable for resection of posterior margin of nasopharyngeal tumor recurrence. Facial translocation offers the widest operative field and is the most versatile approach for radical resection of nasopharyngeal tumor recurrence, but the surgeon should be skilled in the management of the facial nerves to reduce morbidity.

Adult↗

PubMed2000

Prevalence of the Taiwan variant of the Epstein-Barr virus in nasopharyngeal carcinoma patients and normal individuals.

BACKGROUND: Latent membrane protein 1 (LMP1) of Epstein-Barr virus (EBV) is a potentially oncogenic protein, able to inhibit differentiation and induce transformation of epithelial cells. The LMP1 gene sequence of EBV in nasopharyngeal carcinoma (NPC) differs from that of EBV in B95-8 cells. A change of nucleotide at the XhoI site results in loss of the restriction site in the EBV LMP1 gene from NPC, and this of EBV is designated as the Taiwan variant. In this study, we further investigated the Taiwan variant of EBV in nasopharyngeal biopsies and throat washings of NPC patients and normal controls. METHODS: DNA was extracted from nasopharyngeal biopsies of 22 NPC patients and 40 normal controls, and from throat washings of 28 NPC patients and 78 normal controls. The DNA was amplified by polymerase chain reaction (PCR) using LMP1 gene-specific primers, then the EBV variant was identified by analysis with the XhoI restriction enzyme. RESULTS: The LMP1 gene was detected in all NPC tumors, in only 25 of 40 normal nasopharyngeal biopsies, and in 12 of 28 and 44 of 78, respectively, throat washings of NPC patients and normal controls. The Taiwan variant was detected in 84.1% to 100% of EBV isolates. The distribution of Taiwan variant EBV was not statistically different between the NPC group and normal controls in either nasopharyngeal biopsies or throat washings. CONCLUSIONS: The results indicate that, based on XhoI restriction site analysis, the Taiwan variant of EBV is the predominant EBV strain in NPC patients and normal individuals in Taiwan.

Base Sequence↗

PubMed1999

Salvage surgery for recurrent nasopharyngeal carcinoma in anterior marginal miss after radiotherapy.

Nasopharyngeal carcinoma (NPC) is treated primarily by radiotherapy. Marginal miss after radiotherapy is a potential cause for treatment failure in NPC. Anterior marginal miss after irradiation results in recurrent tumors in the nasal cavity outside the nasopharynx. From 1991 to January 1997, 6 recurrent NPCs arising in the anterior marginal miss zone after radiotherapy were confirmed by pathologic and radiologic evaluation. One patient had infiltrating growth of the original NPC tumor into the anterior part of nasal septum, and the other 5 had microscopic extensions from the original NPC tumors into the nasal cavity that were beyond detection by endoscopy or CT scan. In some cases the tumors extended further to include the hard palate or the lacrimal sac. Medial maxillectomy and partial maxillectomy with or without resection of the hard palate were necessary to encompass the extent of the tumors. Surgical margins were free of cancer cells in 5 patients. No further treatment was given in these 5 patients. Another patient with tumor extending to the lacrimal sac received postoperative radiotherapy. Five of the 6 patients survived with no evidence of disease for 8 to 65 months. One patient had distant metastasis 14 months after surgery but was free from tumor at the primary site. Radical surgery can result in good and sustained local control for anterior marginal miss of NPC after radiotherapy.

Adult↗

PubMed1999

cAMP mediates transepithelial K+ and Na+ transport in a strial marginal cell line.

Because cytoplasmic cAMP has been reported to be the secondary messenger mediating K+ transport in marginal cells of freshly isolated stria vascularis, the possible role of cAMP in ion transport processes of an immortalized marginal cell line (MCPV-8) showing evidence of K+ and Na+ reabsorption was evaluated in this study. Confluent MCPV-8 monolayers were mounted into Ussing chambers and perfused on both sides with perilymph-like Ringer's solution. Transepithelial short-circuit current (I(SC)), resistance (R(T)) and open-circuit voltage (V(T)) were measured using voltage clamp technique. The following results were obtained. (1) Addition of forskolin (10(-4) M) to the basolateral perfusate increased I(SC) to 311 +/- 42%; no significant change in RT was observed. Addition of BaCl2 (2 mM) to the apical perfusate at the maximal response of forskolin blocked 50-60% of I(SC) and subsequent addition of amiloride (10(-5) M) to the apical perfusate further blocked I(SC) to a value close to 0. (2) To evaluate the effect of cellular cAMP on Ba2+-sensitive K+ current, amiloride-sensitive Na+ current was blocked first by addition of amiloride (10(-5) M) to the apical perfusate; subsequent addition of 3-isobutyl-1-methylxanthine (IBMX, 1 mM) or N6,2'-O-dibutyryladenosine 3',5'-cyclic monophosphate (dbcAMP, 1 mM) to the basolateral perfusate increased I(SC) to 175 +/- 13 and 411 +/- 32%, respectively. The stimulated I(SC) was blocked to close to 0 by addition of BaCl2 (2 mM) to the apical perfusate. N2,2'-O-Dibutyrylguanosine 3',5'-cyclic monophosphate (dbcGMP, 1 mM) had no effect on I(SC). (3) To assess the effect of cellular cAMP on amiloride-sensitive Na+ current, Ba2+-sensitive K+ current was blocked in advance by addition of BaCl2 to the apical perfusate; subsequent addition of IBMX or dbcAMP to the basolateral perfusate increased I(SC) to 219 +/- 21% and 388 +/- 39%, respectively. The stimulated I(SC) was blocked to close to 0 by addition of amiloride to the apical perfusate. dbcGMP had no effect on I(SC). Hence, these results suggest that cellular cAMP is the secondary messenger that mediates the transepithelial transport of both K+ and Na+ in MCPV-8 monolayers.

1-Methyl-3-isobutylxanthine↗

PubMed1999

A novel podophyllotoxin-derived compound GL331 is more potent than its congener VP-16 in killing refractory cancer cells.

PURPOSE: GL331 is a new homolog of VP-16, and has demonstrated more efficacious anti-cancer activity in both the in vitro and in vivo lymphoma systems. To extensively explore GL331's clinical value, we furthermore evaluate the cytotoxicity and apoptosis-inducing activity of GL331 in several human cell lines from cancers that are not normally treated with VP-16. METHODS: By MTT and clonogenic survival assays, the cytotoxicities of GL331 and VP-16 were evaluated in a variety of cell lines including nasopharyngeal, hepatocellular, gastric, colon, cervical, and neuroblastoma cancer types. Western blot analysis was performed to detect the MDR-1 level in these cell lines. By Annexin V-staining flow cytometry and detection of DNA ladders, the apoptosis-inducing activities of GL331 and VP-16 were also evaluated. RESULTS: GL331 showed more efficacy than its congener VP-16 in killing cancer cells. The estimated ID50 of GL331 were 2.5 to 17-fold lowerthan those of VP-16. GL331 possessed more cell-killing activity even in MDR-1-overexpressing cell lines such as HCC36 and SW620. Its higher cytotoxicity could be attributed by the elevated ability to induce apoptotic cell death. CONCLUSION: GL331's overriding drug resistance and higher cancer cell-killing activity suggest its superiority in clinical cancer therapy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1999

Chromosomal aberrations in nasopharyngeal carcinoma analyzed by comparative genomic hybridization.

To investigate the genomic imbalances associated with nasopharyngeal carcinoma (NPC), we have performed chromosome analysis by comparative genomic hybridization (CGH) on 51 tumors, including 25 primary and 26 recurrent tumors. The most common copy number increases occurred on chromosome arms 12p (59%), 1q (47%), 17q (47%), 11q (41%), and 12q (35%). The minimal overlapping regions were at 12p12-13, 1q21-22, 17q21, 17q25, 11q13, and 12q13. The most frequent losses were from chromosome arms 3p (53%), 9p (41%), 13q (41%), 14q (35%), and 11q (29%). The minimal overlapping regions were at 3p12-14, 3p25-26, 9p21-23, 13q21-32, 14q12-21, and 11q14-23. Compared with the primary cancers, no additional chromosomal change was found in the recurrent tumors; however, the most frequent gain in the recurrent NPCs was at 11q13 (53%) instead of 12p in the primary tumors. An increase of gene alterations correlated with clinical stage. Our results provide a first comprehensive view of the genomic changes associated with NPC and reveal several new sites of genomic imbalance, indicating the possible involvement of novel oncogenes/tumor suppressor genes in the carcinogenesis of NPC.

Adult↗

PubMed1999

Detection of IgA against Epstein-Barr virus BZLF-1 replication activator (ZEBRA) in sera of nasopharyngeal carcinoma patients with a recombinant ZEBRA protein.

BACKGROUND: Epstein-Barr virus (EBV) is closely associated with nasopharyngeal carcinoma (NPC). An EBV-encoded immediate-early antigen, BZLF-1 replication activator (ZEBRA) initiates EBV replication and expression in all NPC tumors. In this study, we investigated whether immunoglobulin A (IgA) against ZEBRA is present in the sera of patients with NPC, and whether it was able to be determined by enzyme-linked immunosorbent assay (ELISA) using a recombinant ZEBRA prepared from Escherichia coli. METHODS: A polymerase chain reaction-amplified cDNA fragment of the ZEBRA gene was inserted into the expression vector of E coli under the control of an IpL promoter. E coli bacteria containing the CI857 gene served as host to overexpress the ZEBRA protein by heat induction. Recombinant ZEBRA was collected by mechanical disruption of the bacteria, purified by column chromatography, and analyzed by SDS-PAGE and Western blot assay using sera from NPC patients. The recombinant ZEBRA was used to develop the ELISA to detect IgA against ZEBRA. RESULTS: The amount of ZEBRA produced comprised 30% of total E coli protein. Western blot assay confirmed that affinity of the recombinant ZEBRA to IgA antibody was preserved. IgA against ZEBRA was shown to be positive by ELISA in 36 of 40 NPC sera, but in only nine of 55 patients with other head and neck malignancies, and two of 35 normal individuals. For serologic diagnosis of NPC, the sensitivity of IgA/ZEBRA detected by ELISA was 90% and the specificity was 87.4%. CONCLUSIONS: A recombinant ZEBRA was produced at high levels in E coli and retained affinity to IgA against ZEBRA. The recombinant ZEBRA was successfully used to develop an ELISA for the detection of IgA against ZEBRA. The high sensitivity and specificity of IgA against ZEBRA show that the ELISA is feasible for serologic diagnosis of NPC.

Adult↗

PubMed1999

Malignant otitis externa.

BACKGROUND: Malignant otitis externa is an infrequent but severe infection of the external auditory canal, most often affecting elderly diabetic patients. Early diagnosis is necessary due to its high morbidity and mortality. METHODS: From 1990 to 1997, all patients with malignant otitis externa at the Veterans General Hospital-Taipei were reviewed retrospectively. The clinical features and the strategy of diagnosis and treatment are discussed. RESULTS: Twelve patients with an average age of 65.3 years were included. Eleven of these patients were diabetic. All had the presenting symptoms of otalgia and otorrhea at diagnosis. Bacterial cultures grew Pseudomonas aeruginosa in eight patients and methicillin-resistant Staphylococcus aureus in four patients. The mean duration of admission was 82 days. Appropriate antibiotics were given according to the results of bacterial culture and sensitivity test. 99Technetium scans and 67gallium scans were performed to evaluate the extent of involvement and monitor the effects of treatment. Eventually, four patients died due to renal failure, meningitis, pneumonia and upper gastrointestinal bleeding, respectively. CONCLUSIONS: Malignant otitis externa is a life-threatening infection arising from the external auditory canal. A high degree of suspicion for malignant otitis externa is mandatory. Vigorous local and systemic antimicrobial treatment should be initiated early in the course of the disease to achieve a satisfactory outcome. 99Technetium and 67gallium scans are important for the diagnosis and evaluation of the treatment results.

Adult↗

PubMed1998

Establishment and characterization of a strial marginal cell line maintaining vectorial electrolyte transport.

E6/E7 genes of human papilloma virus type 16 were used to immortalize a primary culture of marginal cells (MC) from gerbils. One of the cloned lines was selected which demonstrated preservation of the main characteristics of the MC, both morphologically and physiologically. Electron microscopic examination showed well-developed junctional complexes and apical microvilli which suggested its epithelial origin. Polymerase chain reaction (PCR) demonstrated the incorporation of E6/E7 genes with the genome. Reverse transcription PCR revealed the existence of mRNA of the IsK channel, a unique marker of MC among the inner ear cells, in this clone. Flow cytometric analysis of this cell line's DNA content was diploid. Numerous large domes formed after confluence of the cell monolayer. Electrophysiologic studies displayed evidence of apical K+ and Na+ channels which were blocked by Ba2+ (2 mM) and amiloride (10(-5) M), respectively. Existence of basolateral Na,K-ATPase and Na+/Cl-/K+ cotransporter was shown by blockage by ouabain (10(-3) M) and bumetanide (50 microM), individually. Injection of the cell line to nude mice failed to induce growth of tumors. This cell line was serum-, density- and anchorage-dependent when cultured in plastic dishes. In conclusion, this cell line shows characteristics of well-differentiated MC maintaining the major ionic transport processes, and provides us a good model to study the possible mechanisms and regulating factors of endolymph production.

Animals↗

PubMed1998

Effects of acute brainstem compression on auditory brainstem response in the guinea pig.

BACKGROUND: The purpose of this study was to establish the norm for parameters of auditory brainstem response (ABR) in the guinea pig and to investigate if acute brainstem compression results in significant changes to these parameters. METHODS: Thirty-six guinea pigs with positive Preyer's reflex were anesthetized. A craniectomy was performed to remove the right occipital bone and the dura mater was opened to expose the brain, cerebellum and cerebellopontine angle (CPA). A small inflatable balloon was placed into the CPA precisely and slowly. ABR was recorded before incision of the skin as a baseline value, after placement and after inflation of the balloon with water at 0.1-ml intervals. RESULTS: Five stable peaks were recorded in 27 experimental animals. When the balloon was inflated with 0.1 ml water, the absolute latency (AL) of peaks IV and V and the interpeak latency (IPL) of peaks III and IV, and IV and V were prolonged. The amplitude ratios (AR) of peaks II, III, IV and V to peak I decreased. Inflation of the balloon with 0.2 ml of water caused further elongation of ALs of peaks IV and V and decreases in each AR. When the balloon volume increased to 0.3 ml, peak V became unrecognizable and peaks III and IV showed significant elongation of AL; peaks I and II did not show significant change in ALs. Further increase of the balloon volume to 0.4 ml resulted in disappearance of peaks III, IV and V; AL of peak II was also elongated. However, the amplitude and AL of peak I remained unchanged. Similar changes were observed in IPLs. CONCLUSIONS: This study establishes the norm of parameters of ABR in guinea pigs and demonstrates that acute brainstem compression causes elongation of ALs and IPLs of peaks II, III, IV and V. This suggests that peaks II, III, IV and V come from the brainstem and that peak I is not generated from the brainstem in the guinea pig.

Animals↗

PubMed1997

Activation of CDC 25 phosphatase and CDC 2 kinase involved in GL331-induced apoptosis.

CDC 25 is a dual phosphatase responsible for dephosphorylation and, thus, activation of CDC 2 kinase in G2. Abnormal activation of cyclin B-associated CDC 2 kinase has been implicated in apoptosis induced by cancer chemotherapeutic agents such as paclitaxel (Taxol) and etoposide (VP-16). In this study, we found that the CDC 2 kinase could be transiently activated when nasopharyngeal carcinoma NPC-TW01 cells were treated for 3 h with a new anticancer agent, GL331. GL331 treatment also induced a concomitant increase in CDC 25A phosphatase activity and a reduced level of Tyr-15-phosphorylated CDC 2 in NPC-TW01 cells. Furthermore, subsequent apoptotic DNA fragmentation induced by GL331 could be interrupted by treatment of the cells with the cyclin B1-specific antisense oligonucleotides, suggesting that abnormal activation of cyclin B1-associated CDC 2 kinase and CDC 25A phosphatase was involved in GL331-induced apoptosis. Raf-1 has been shown to associate with CDC 25A and, thus, to stimulate its phosphatase activity. Our results revealed that GL331 could facilitate the association of CDC 25A with Raf-1, resulting in the cascade of CDC 25A phosphatase activation and CDC 2 kinase activation, as well as related signaling pathways, and ultimately causing apoptosis in cancer cells.

Antineoplastic Agents, Phytogenic↗

PubMed1997

Identification of a promoter for the latent membrane protein 1 gene of Epstein-Barr virus that is specifically activated in human epithelial cells.

Latent membrane protein 1 (LMP 1) is one of two Epstein-Barr virus (EBV)-encoded proteins that expressed in nasopharyngeal carcinoma (NPC) cells. Previous studies showed that a 3.5-kb transcript of the LMP 1 gene, in addition to the 2.8-kb transcript, was detected in a B95-8-EBV-containing, nude mice-passaged NPC tumor, C15. This indicated that a transcript was initiated from a region 5' to the putative promoter, ED-L1. We have isolated an EBV variant from a NPC tissue, and this virus strain contained a more pathogenic LMP 1 gene. DNA sequence analysis of the 5'-upstream region showed distinct variations as compared to that of B95-8 strain. To test if the LMP 1 gene of the NPC strain also contained an upstream promoter, we generated a series of deletion plasmids encompassing positions -1,030 to +20 of the LMP 1 promoter and tested for their abilities to drive the expression of the reporter gene in human epithelial cell lines, C-33A and NPC-TW076. We found that the region between -643 and -496 contained a promoter activity that was approximately five-fold higher than the putative promoter, ED-L1. This region between -643 and -496 was designated as ED-L1E. C-33A cells containing the genomic clone pT7(E) or the clone that had deleted a 94-bp ED-L1 sequence (delta94) was used to determine the transcription initiation sites by RNase protection assay. Results showed that a transcription initiation site was located at nucleotide 170,099 ("A") of EBV genome. The transcript was expressed in NPC biopsies and in human primary normal epithelial cells transfected with pT7(E) and delta94, respectively, as examined by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. Furthermore, the ED-L1E was not regulated by the EBV-encoded nuclear antigen 1-mediated transcriptional enhancer family of repeats (FR) in C-33A cells. Our results suggested that the ED-L1E was specifically activated in epithelial cells. The biological significance of the selective usage of the ED-L1E promoter was discussed.

B-Lymphocytes↗

PubMed1996

Protein tyrosine phosphatase activities are involved in apoptotic cancer cell death induced by GL331, a new homolog of etoposide.

GL331 is a semisynthetic topoisomerase II inhibitor derived from a plant toxin podophyllotoxin. In 72-h exposure assays, LD50 values of GL331 range from 0.5 to 2 microM, which are three- to ten-fold lower than those of its homologous compound etoposide (VP-16), depending on different cancer cell lines including nasopharyngeal, hepatocellular, gastric, cervical and colon cancer types. Apoptotic DNA ladders could be detected when cancer cells were treated with GL331 for 24 h even if the Bcl-2 and Bax protein levels were not altered during the period. Besides acting as topoisomerase II inhibitors, both GL331 and VP-16 decrease the cellular protein tyrosine kinase (PTK) activities in cancer cells. The activities of protein tyrosine phosphatase (PTP) are significantly increased after GL331 treatment but are not affected by VP-16. GL331-induced internucleosomal cleavage can be efficiently prevented by two inhibitors of PTP, sodium orthovanadate and zinc chloride, but not by okadaic acid, which inhibits serine/threonine phosphatase activity. These results indicate that GL331 may induce apoptotic cell death, and that activation of protein tyrosine phosphatases may be involved in this process.

Antineoplastic Agents, Phytogenic↗

PubMed1996

Kinetics of continuous GM-CSF production by recombinant Saccharomyces cerevisiae in an airlift bioreactor.

Continuous production of murine GM-CSF by recombinant Saccharomyces cerevisiae in an airlift bioreactor was studied at three different dilution rates. The reactor was initially fed with a selective medium to increase cell concentration, and then was fed with a rich, nonselective medium for GM-CSF production. Ethanol was used as the main carbon source to provoke GM-CSF expression. In continuous culture, GM-CSF production was maintained for over 150 h, even though the fraction of plasmid-carrying cells continuously dropped to lower than 20%. The stable GM-CSF production during the later phase of the continuous culture was attributed to increased specific cell productivity possibly resulting from an increase in the plasmid copy number in plasmid-carrying cells. This also indicated the possibility of natural selection of high-copy number cells in continuous culture. Plasmid stability was found to be growth rate (dilution rate) dependent; it increased with the dilution rate. Reactor productivity and specific productivity also increased with the dilution rate. A two-parameter kinetic equation was used to model the plasmid stability kinetics. The growth rate ratio between plasmid-carrying and plasmid-free cells increased from 0.996 to 0.998 while the segregational instability or the probability of plasmid loss from each cell division increased from 1.1% to 16% as the dilution rate decreased from 0.11 h-1 to 0.05 h-1. Oscillation of the dilution rate between 0.05 h-1 and 0.11 h-1 stabilized the plasmids and gave a higher productivity than that achieved without oscillation.

Animals↗

PubMed1995

Elimination of dose limiting toxicities of cisplatin, 5-fluorouracil, and leucovorin using a weekly 24-hour infusion schedule for the treatment of patients with nasopharyngeal carcinoma.

BACKGROUND: Cisplatin, 5-flourouracil (5-FU), and leucovorin (PFL) chemotherapy has been reported to be effective in the treatment of cancers but severe mucositis or neutropenia are dose limiting toxicities. This Phase II study evaluated the anticancer effect and the toxicities of a new weekly 24-hour infusional PFL chemotherapy in patients with nasopharyngeal carcinoma (NPC). METHODS: Forty-two patients with stage IV NPC were studied. Cisplatin 25 mg/m2/d, 5-FU 2200 mg/m2/d, and leucovorin 120 mg/m2/d were adminstered weekly by 24-hour intravenous continuous infusion in an outpatient setting. Clinical response and toxicity were evaluated weekly. RESULTS: The complete response rate (CR) was 30% and the partial response (PR) rate 60% in the localized previously untreated group. The CR rate was 22.7% and PR rate 45.5% in local recurrent/metastatic group. The overall response rate was 79%. Eighty-one percent of patients who had no previous chemotherapy and 67% of patients who had previous chemotherapy responded to weekly PFL. There were no dose limiting toxicities. No patient had grade 3 or 4 mucositis or neutropenia. Thirty-two patients (76%) had no oral mucositis. Seven patients (17%) had grade 1 mucositis and 3 patients (7%) had grade 2 mucositis. CONCLUSIONS: Elimination of dose limiting toxicities is possible using a weekly 24-hour infusion schedule of PFL chemotherapy while retaining significant anticancer activity as demonstrated in these patients with advanced NPC. To discover whether this schedule is superior to cisplatin and 5-FU or other PFL chemotherapy regimens requires further investigation.

Adult↗