Biomedical subjects

Jun Chen

Publications and source records attributed to Jun Chen.

At least 379 records · Page 21Linked to original sources

PubMed2002

Arsenic trioxide as a novel anticancer agent against human transitional carcinoma--characterizing its apoptotic pathway.

Arsenic trioxide (As(2)O(3)) has been shown to be an active agent against acute promyelocytic leukemia. Little is known about its therapeutic efficacy in human transitional carcinomas. In this study, the arsenic-mediated apoptotic pathway in transitional carcinoma cells was investigated. Three bladder transitional carcinoma cell lines were used, including a parental sensitive line and two resistant daughter lines (cisplatin and As(2)O(3) resistant). The As(2)O(3)-mediated cytotoxicity to the three cell lines was studied in vitro in the presence or absence of buthionine sulfoximine (BSO), a chemotherapy modulator. In results, although a lesser extent of apoptosis was seen in cells treated with As(2)O(3) alone, more significant apoptotic events were observed in the combined treatment of As(2)O(3) and non-toxic concentrations of BSO (up to 10 microM). These included the accumulation of sub-G(1) fractions and internucleosomal DNA breakdown, which were preceded by production of reactive oxygen species, loss of mitochondrial membrane potential and activation of caspase-3. In conclusion, As(2)O(3) in the presence of BSO may be an active agent against both chemonaive and cisplatin-resistant transitional carcinomas. The As(2)O(3)-mediated cytotoxicity appeared to go through the conventional apoptotic pathway. Our results have clinical implications and warrant further investigation.

Antineoplastic Agents↗

PubMed2002

Induction of caspase-activated deoxyribonuclease activity after focal cerebral ischemia and reperfusion.

Deoxyribonucleic acid fragmentation at nucleosomal junctions is a hallmark of neuronal apoptosis in ischemic brain injury, for which the mechanism is not fully understood. Using the in vitro cell-free apoptosis assay, the authors found that caspase-3-dependent deoxyribonuclease activity caused internucleosomal DNA fragmentation in brain-cell extracts in a rat model of transient focal ischemia. This in vitro deoxyribonuclease activity was completely inhibited by purified inhibitor of caspase-activated deoxyribonuclease protein, the specific endogenous inhibitor of caspase-activated deoxyribonuclease, or by caspase-activated deoxyribonuclease immunodepletion. The induction of the deoxyribonuclease activity was correlated with caspase-3 activation and caspase-3-mediated degradation of inhibitor of caspase-activated deoxyribonuclease. Furthermore, inhibiting caspase-3-like protease activity prevented the endogenous induction of internucleosomal DNA fragmentation in the ischemic brain. These results suggest that caspase-3-dependent caspase-activated deoxyribonuclease activity plays an important role in mediating DNA fragmentation after focal ischemia.

Animals↗

PubMed2002

Cloning and characterization of rat caspase-9: implications for a role in mediating caspase-3 activation and hippocampal cell death after transient cerebral ischemia.

Delayed hippocampal neurodegeneration after transient global ischemia is mediated, at least in part, through the activation of terminal caspases, particularly caspase-3, and the subsequent proteolytic degradation of critical cellular proteins. Caspase-3 may be activated by the membrane receptor-initiated caspase-8-dependent extrinsic pathway and the mitochondria-initiated caspase-9-dependent intrinsic pathway; however, the precise role of these deduced apoptosis-signaling pathways in activating caspase-3 in ischemic neurons remains elusive. The authors cloned the caspase-9 gene from the rat brain and investigated its potential role in mediating ischemic neuronal death in a rat model of transient global ischemia. Caspase-9 gene expression and protease activity were extremely low in the adult brain, whereas they were developmentally upregulated in newborn rats, especially at postnatal 12 weeks, a finding consistent with the theory of an essential role for caspase-9 in neuronal apoptosis during brain development. After 15-minute transient global ischemia, caspase-9 was overexpressed and proteolytically activated in the hippocampal CA1 neurons at 8 to 72 hours of reperfusion. The temporal profile of caspase-9 activation coincided with that of cytochrome c release and caspase-3 activation, but preceded CA1 neuronal death. Immunoprecipitation experiments revealed that there was enhanced formation of Apaf-1/caspase-9 complex in the hippocampus 8 and 24 hours after ischemia. Furthermore, intracerebral ventricular infusion of the relatively specific caspase-9 inhibitor N-benzyloxycarbonyl-Leu-Glu-His-Asp-fluoro-methylketone before ischemia attenuated caspase-3-like activity and significantly enhanced neuronal survival in the CA1 sector. In contrast, inhibition of caspase-8 activity had no significant effect on caspase-3 activation or neuronal survival. These results suggest that the caspase-9-dependent intrinsic pathway may be the primary mechanism responsible for the activation of caspase-3 in ischemic hippocampal neurons.

Amino Acid Sequence↗

PubMed2002

VEGF expression in hypoxia and hyperglycemia: reciprocal effect on branching angiogenesis in epithelial-endothelial co-cultures.

Vascular endothelial growth factor (VEGF), an angiogenic factor for endothelial cells, is produced by glomerular and tubular epithelia. Using immunoelectron microscopy, VEGF expression by podocytes (GEC) and the proximal tubular epithelium of rat kidney was confirmed. To elucidate the mechanisms of VEGF production and its physiologic consequences, studies were performed in cultured GEC and proximal tubular epithelial cells (RPTEC). Both GEC and RPTEC expressed VEGF-120 and 164 mRNA, as detected by quantitative RT-PCR. Hypoxia resulted in an increase in mRNA abundance, more robust in RPTEC than in GEC, and an increase in VEGF expression by 1.9- and 1.6-fold, respectively. 30 mM D-glucose, but not 30 mM L-glucose, resulted in the elevation of VEGF mRNA in RPTEC, but not in GEC, although both cell types showed a comparable modest increase in VEGF expression. Combined treatment (hypoxia and 30 mM D-glucose) resulted in an increase of VEGF mRNA only in RPTEC; however, an enhanced protein expression was detectable in both cell types. To investigate the role of VEGF in branching angiogenesis, "sandwich" co-cultures were applied with endothelial cells and capillary tube formation was compared under the above conditions. Both RPTEC and GEC induced VEGF-dependent capillary tube formation by co-cultured endothelial cells and in both cell types hypoxia further augmented angiogenesis. In contrast, 30 mM D-glucose suppressed angiogenesis in co-cultures with both cell types despite increased mRNA for VEGF receptors 1 and 2. This study shows (1) that VEGF produced by GEC and RPTEC is necessary for branching angiogenesis and (2) that hypoxic environment stimulates VEGF production by both epithelial cell types and augments branching angiogenesis, whereas (3) hyperglycemic microenvironment, although also stimulatory for VEGF production, fails to augment angiogenesis.

Animals↗

PubMed2002

Enhancement of metabolic oxidative stress-induced cytotoxicity by the thioredoxin inhibitor 1-methylpropyl 2-imidazolyl disulfide is mediated through the ASK1-SEK1-JNK1 pathway.

We observed previously that glucose deprivation induces cytotoxicity, increases the intracellular levels of hydroperoxide, and activates the stress-activated protein kinase (SEK) pathway. In this study, we hypothesized that 1-methylpropyl 2-imidazolyl disulfide (IV-2), a thioredoxin (TRX) inhibitor, augments glucose deprivation-induced cytotoxicity by promoting c-Jun N-terminal kinase (JNK) activation. Human prostatic carcinoma DU-145 cells were exposed to glucose-free medium containing various concentrations of IV-2 (10-50 microM). Glucose deprivation alone or IV-2 alone induced minimal cytotoxicity within 7 h. However, the combination of glucose deprivation and IV-2 increased cell death in a dose-dependent manner. The cytotoxicity was suppressed by treatment with an antioxidant, N-acetyl-L-cysteine or overexpressing TRX. The combined glucose deprivation and IV-2 treatment also promoted glucose deprivation-induced JNK1 activation by disrupting the interaction between TRX and apoptosis signal-regulating kinase 1 (ASK1). Overexpression of the JNK1 dominant-negative mutant inhibited the activation of the SEK pathway and protected cells from glucose deprivation and IV-2-induced cytotoxicity. Therefore, IV-2 enhances glucose deprivation-induced cytotoxicity by promoting glucose deprivation-induced activation of the ASK1-SEK1-JNK1 pathway.

Acetylcysteine↗

PubMed2002

VEGF-induced mobilization of caveolae and increase in permeability of endothelial cells.

Glomerular epithelial cells (GEC) are a known site of vascular endothelial growth factor (VEGF) production. We established immortalized rat GEC, which retained the ability to produce VEGF. The isoforms expressed by GEC were defined as VEGF-205, -188, -120, and -164. The electrical resistance of endothelial cells cultured on GEC-conditioned matrix, an indicator of the permeability of monolayers to solutes, was significantly increased by the treatment with the neutralizing polyclonal antibodies to VEGF and decreased by VEGF-165. Transfection of endothelial cells with green fluorescence protein-caveolin construct and intravital confocal microscopy showed that VEGF results in a rapid appearance of transcellular elongated structures decorated with caveolin. Transmission electron microscopy of endothelial cells showed that caveolae undergo rapid internalization and fusion 30 min after application of VEGF-165. Later (36 h), endothelial cells pretreated with VEGF developed fenestrae and showed a decrease in electrical resistance. Immunoelectron microscopy of glomeruli confirmed VEGF localization to podocytes and in the basement membrane. In summary, immortalized GEC retain the ability to synthesize VEGF. Matrix-deposited and soluble VEGF leads to the enhancement of caveolae expression, their fission and fusion, formation of elongated caveolin-decorated structures, and eventual formation of fenestrae, both responsible for the increase in endothelial permeability.

Animals↗

PubMed2002

Endothelial dysfunction in ischemic acute renal failure: rescue by transplanted endothelial cells.

There is accumulating circumstantial evidence suggesting that endothelial cell dysfunction contributes to the "no-reflow" phenomenon in postischemic kidneys. Here, we demonstrated the vulnerability of in vitro, ex vivo, and in vivo endothelial cells exposed to pathophysiologically relevant insults, such as oxidative and nitrosative stress or ischemia. All of these stimuli compromised the integrity of the endothelial lining. Next, we performed minimally invasive intravital microscopy of blood flow in peritubular capillaries, which provided direct evidence of the existence of the no-reflow phenomenon, attributable, at least in part, to endothelial injury. In an attempt to ameliorate the hemodynamic consequences of lost endothelial integrity, we transplanted endothelial cells or surrogate cells expressing endothelial nitric oxide synthase into rats subjected to renal artery clamping. Implantation of endothelial cells or their surrogates expressing functional endothelial nitric oxide synthase in the renal microvasculature resulted in a dramatic functional protection of ischemic kidneys. These observations strongly suggest that endothelial cell dysfunction is the primary cause of the no-reflow phenomenon, which, when ameliorated, results in prevention of renal injury seen in acute renal failure.

Acute Kidney Injury↗

PubMed2002

Relationships between caveolae and eNOS: everything in proximity and the proximity of everything.

Caveolae, flask-shaped invaginations of the plasma membrane occupying up to 30% of cell surface in capillaries, represent a predominant location of endothelial nitric oxide synthase (eNOS) in endothelial cells. The caveolar coat protein caveolin forms high-molecular-weight, Triton-insoluble complexes through oligomerization mediated by interactions between NH2-terminal residues 61-101. eNOS is targeted to caveolae by cotranslational N-myristoylation and posttranslational palmitoylation. Caveolin-1 coimmunoprecipitates with eNOS; interaction with eNOS occurs via the caveolin-1 scaffolding domain and appears to result in the inhibition of NOS activity. The inhibitory conformation of eNOS is reversed by the addition of excess Ca2+/calmodulin and by Akt-induced phosphorylation of eNOS. Here, we shall dissect the system using the classic paradigm of a reflex loop: 1) the action of afferent elements, such as fluid shear stress and its putative caveolar sensor, on caveolae; 2) the ways in which afferent signals may affect the central element, the activation of the eNOS-nitric oxide system; and 3) several resultant well-established and novel physiologically important effector mechanisms, i.e., vasorelaxation, angiogenesis, membrane fluidity, endothelial permeability, deterrance of inflammatory cells, and prevention of platelet aggregation.

Animals↗

PubMed2002

Temporal and spatial expression of a novel zinc finger transcription factor, AJ18, in developing murine skeletal tissues.

Bone morphogenetic proteins (BMPs) are characterized by their ability to induce osteoblastic differentiation. However, the mechanism of osteo-induction by BMPs has yet to be determined. Using differential display we previously identified AJ18, a zinc finger transcription factor, as an immediate-early response gene to BMP-7. AJ18 was shown to bind to the osteoblast-specific element2 (OSE2) and to modulate transactivation by Runx2, a master gene in osteoblastic differentiation. Here we describe the temporal and spatial expression of AJ18 in developing mouse tissues. AJ18 mRNA expression was observed in most tissues, except liver, and was generally highest early in embryonic development, decreasing markedly after parturition. Consistent with immunohistochemical analysis, AJ18 mRNA expression was highest in the brain, kidney, and bone of 17 dpc (days post coitum) embryos. In endochondral bones of embryonic and 4-week-old mice, immunostaining for AJ18 was strong in the nuclei of proliferating and pre-hypertrophic chondrocytes, and osteoblasts, whereas there was low or no staining in hypertrophic chondrocytes. In teeth of embryonic and 4-week-old mice, nuclear staining was observed in precursor and mature ameloblasts, odontoblasts, and cementoblasts, respectively. In addition, in 4-week-old mice staining of AJ18 was observed within alveolar bone cells and periodontal ligament cells. In general, the spatial expression of AJ18 in skeletal and non-skeletal tissues of mouse embryos showed striking similarity to the expression of BMP-7 mRNA. Therefore, the expression of AJ18 is consistent with its perceived role as a transcriptional factor that regulates developmental processes downstream of BMP-7.

Amino Acid Sequence↗

PubMed2002

Hand assisted laparoscopic bilateral nephroureterectomy in 1 session without repositioning patients is facilitated by alternating inflation cuffs.

PURPOSE: Transitional cell carcinoma is common and often multifocal in patients with uremia. We report a novel approach of simultaneous laparoscopic bilateral nephroureterectomy without the need to reposition patients. MATERIALS AND METHODS: Seven patients with uremia and organ confined transitional cell carcinoma of the upper urinary tract underwent simultaneous laparoscopic bilateral nephroureterectomy. Inflatable cuffs of an air tourniquet device were placed beneath each side of the back. Alternatively inflating the cuffs and rotating the operation table facilitated position changes during surgery. The incision for the hand assisted device during laparoscopy was also used for resecting the distal ureters in an open manner. Data were compared with those on 7 patients treated with simultaneous open bilateral nephroureterectomy. RESULTS: All laparoscopic bilateral nephroureterectomies were accomplished successfully without complications except for heart failure and atlectasis in a patient with a history of myocardial ischemia. Mean blood loss (218 versus 457 ml.), parenteral narcotic requirement (25 versus 60 mg. morphine equivalent), solid food oral intake (39 versus 83 hours), postoperative hospital stay (9 versus 14 days) and convalescence to normal nonstrenuous activity (3.5 versus 5.4 weeks) were superior in the laparoscopic bilateral nephroureterectomy group. Mean operative time was about 5 hours in each group. CONCLUSION: Our data show that laparoscopic bilateral nephroureterectomy facilitated by inflatable cuffs can be performed at 1 stage with a clear operative field and no repositioning problems.

Adult↗

PubMed2002

Association of changes in the pattern of urinary calculi in Taiwanese with diet habit change between 1956 and 1999.

OBJECTIVE: Due to rapid economic development over the past four decades, urinary stone components may have changed in Taiwan. We studied the changes in urinary stone components over time and the possible association with dietary changes during the same period. MATERIALS AND METHODS: From 1956 to 1999, 9,715 urinary calculi were collected at a single institution and analyzed using polarizing microscopy. Dietary information was obtained from an official national report. Linear regression was used to analyze the possible correlation between the change in stone components with daily consumption of animal protein, vegetable protein, and lipid. RESULTS: Eleven distinct components were identified. Calcium oxalate (Jensen type I stone; found in sterile, acidic urine) was found most frequently (87.3%), and its incidence increased gradually with time. However, the incidence of Jensen type III stone (caused by metabolic abnormality) gradually decreased from 1956 to 1999. The male to female ratio among subjects was 2.3:1, and the modal age was in the forties. Female patients were more likely to suffer from type II stones (found in infected, alkaline urine), whereas type I and III stones were more prevalent in males. Among the dietary components, consumption of animal and vegetable proteins and lipid increased significantly during the same period, and appeared to be coincident with the increased incidence of type I stones during the study period. CONCLUSIONS: Patterns of urinary tract stones in Taiwan have progressively changed in the past four decades and are now similar to those in western populations. The incidence of type I stones has increased during the past four decades, which may reflect the Westernization of dietary habits in Taiwanese during the same period.

Adult↗

PubMed2002

Technical considerations in hand-assisted laparoscopic live donor nephrectomy: initial Taiwan experience from National Taiwan University Hospital.

This report describes the initial experience of laparoscopic live donor nephrectomy (lap-LDN) in Taiwan and discusses the technical considerations and modifications of our technique. From September to November 2000, three (one right and two left) lap-LDNs were performed at our institute. The right kidney was retrieved in one donor because of an early branching of the left renal artery. The details of our technique are described for both left and right LDN. The perioperative parameters were compared to those of the 10 immediately preceding cases of LDNs using the traditional open approach. All lap-LDNs and open LDNs were successful, and all 13 recipients had smooth recovery of renal function. The donors recuperated better in the lap-LDN group with resumption of oral intake on postoperative day (POD) 1 and discharge on POD 5 (vs POD 3.4 and 8.5, respectively, in the open group). The mean blood loss was lower and narcotic use was less in the lap-LDN group (75 vs 164 mL, 25 vs 47 mg morphine sulfate equivalent, respectively). The extraction wound was much shorter in the lap-LDN group (6.5-8 vs 23 cm). The warm ischemia time was slightly but not significantly shorter in the open group (4 vs 2.75 min), and the average operative time was shorter in the open group. The results of our initial experience suggest that for surgeons with laparoscopic surgery experience, lap-LDN is a feasible procedure that decreases donor discomfort, while improving the quality of graft kidneys and the safety of the donor.

Humans↗

PubMed2002

Is ureteral stenting necessary after uncomplicated ureteroscopic lithotripsy? A prospective, randomized controlled trial.

PURPOSE: We conducted a prospective, randomized controlled study to investigate the advantages and disadvantages of ureteral stenting after ureteroscopic lithotripsy. MATERIALS AND METHODS: A total of 60 patients who underwent ureteroscopic lithotripsy were equally randomized into a stented or a nonstented group. The inclusion criteria were stone 6 to 10 mm., absence of polyp or stricture in the ureter and no mucosal injury during ureteroscopy. The operation was performed with a 6Fr rigid ureteroscope without ureteral dilation and stones were fragmented with a 1.9Fr electrohydraulic lithotriptor without extraction. A 7Fr double pigtail stent was placed in the stented group for 3 days after ureteroscopy. Urinalysis, plain x-ray and renosonography were performed before and after lithotripsy in each patient. Subjective symptoms and pain score were recorded on admission to the hospital and 3 days postoperatively. RESULTS: The stone-free rate was 100% in each group and preoperative hydronephrosis equally resolved in both groups. Mean pain score plus or minus standard deviation improved significantly in the nonstented (6.33 +/- 1.81 preoperatively to 2.30 +/- 1.93 postoperatively, paired Student's t test p <0.0001) and stented (7.10 +/- 1.03 to 2.30 +/- 2.22, p < 0.0001) group. There was no statistical difference in pain reduction between the 2 groups (p = 0.18). The amount of extra parenteral analgesic used was similar in both groups. One patient in the nonstented group visited the emergency room for postoperative renal colic, 25 (83.3%) patients in the stented group complained of at least 1 irritative bladder symptom and only 4 (13.3%) in the nonstented group experienced bladder discomfort. CONCLUSIONS: After uncomplicated ureteroscopic electrohydraulic lithotripsy patients without ureteral stenting tend to have similar renal function recovery and satisfactory pain reduction with less irritative symptoms compared to those treated with a ureteral stent. We suggest that it is not necessary to place a ureteral stent routinely after uncomplicated ureteroscopic electrohydraulic lithotripsy for stones smaller than 1 cm.

Adult↗

PubMed2002

Changes in the oxidant-antioxidant balance in the kidney of rats with nephrolithiasis induced by ethylene glycol.

PURPOSE: We investigated the possible mechanism of increased free radicals, the role of antioxidant enzymes and their correlation with renal tubular damage in the kidney after feeding 0.75% ethylene glycol to male Wistar rats. MATERIALS AND METHODS: Rats were divided into 7 experimental groups according to the duration of ethylene glycol feeding (1, 3, 5, 7, 9, 21 or 42 days) and into age matched control groups. Chemiluminescence levels were examined in blood samples (renal artery and vein) and in the kidney. The activities of oxidase and antioxidant enzymes were measured in kidney homogenates. The nitroblue tetrazolium perfusion method and immunohistochemical stains with ED1 and CD45 were performed. Urinary levels of alpha and mu-glutathione S-transferase (GST) were also measured and expressed in gm. urinary creatinine. RESULTS: Chemiluminescence levels of renal venous blood samples were elevated on days 1, 3 and 7 (p <0.05), and those of the kidney were elevated only on days 3 and 42 (p <0.05) compared with controls. The infiltration of CD45 positive cells in the kidney increased on day 7 and a further increase in these positive cells was noted on day 21. Fused ED1 positive cells surrounding the calcium oxalate crystals and adjacent to the nitroblue tetrazolium positive area were found on day 42. Xanthine oxidase activity showed no significant change, whereas nicotinamide adenine dinucleotide dependent oxidase activity was higher on day 5 and nicotinamide adenine dinucleotide phosphate dependent activity was elevated in all experimental groups (p <0.05). The activities of catalase and manganese superoxide dismutase were elevated in the early stage. On day 42 almost all antioxidant enzyme activities were attenuated (p <0.05) except that of catalase. The urinary levels of alpha-GST were elevated from day 7 until day 42, whereas levels of mu-GST were elevated from day 3 until day 42 except day 5. CONCLUSIONS: The possible mechanism that causes free radical elevation in the kidney may be different in the course of nephrolithiasis after ethylene glycol treatment. Initially the systemic circulation may bring the toxic substance into the kidney and cause it to produce free radicals. In the late stage gradually infiltrating leukocytes and decreased antioxidant enzyme activities may cause the kidney to remain under excessive oxidative stress.

Animals↗

PubMed2002

One-stage correction of congenital complex penile curvature by tunica albuginea plications.

BACKGROUND AND PURPOSE: Congenital complex penile curvature has two deformity components: torsion and curvature of the penile shaft. Limited cases have been reported and were managed with an invasive Nesbit procedure. We introduce a novel simple surgical technique to correct the deformity in one stage. PATIENTS AND METHODS: Plications of the tunica albuginea were applied to treat five patients (median age, 28 yr) with congenital complex penile curvature. Mean follow-up duration was 14 months (range, 9-20 mo). In the first case, penile curvature was corrected first followed by the torsion. In the other four cases, the sequence was reversed. A parabolic curve was made from the subcoronal area crossing the dorsal midline and extending toward the penile base obliquely to the direction of counter-torsion. Along the curve, two points (one at the maximum convexity and the other depending on the type of curvature) were chosen for plications to correct torsion. The remaining curvature was corrected subsequently. RESULTS: It took five plications to accomplish a satisfactory result in the first case. In the other four cases, only three plications were needed to correct the deformity. In all five patients, penile deformities were corrected successfully with either residual torsion or curvature being no more than 5 degrees. All patients were satisfied with excellent cosmetic and functional results with no recurrent curvature or torsion. All patients had started successful sexual intercourse shortly more than 2 months after the operation without erectile problems. One patient reported a mild sensory impairment of the penile skin that resolved 2 months later. CONCLUSIONS: By correcting penile torsion and curvature in sequence with plications of the tunica albuginea, congenital complex penile curvature can be corrected in a one-stage operation with good cosmetic and functional results.

Adult↗

PubMed2002

[Correlation of protein kinase C isoform expression with multidrug resistance in KBV200 cells].

OBJECTIVE: To investigate the association of protein kinase C (PKC) isoforms and multidrug resistance (MDR) mechanism in KBV200 cells. METHODS: Western blotting was utilized to examine the expression and subcellular distribution of PKC isoforms were measured in KBV200 cells with MDR and drug-sensitive KB cells, and the fluorescence intensity of PKC isoforms was detected by flow cytometry (FCM). RESULTS: KBV200 cells possessed higher PKC activities, with increased percentage of membrane fraction. As compared with parental KB cells, the expression of PKCalpha was significantly increased in KBV200 cells, while PKCbeta and epsilon expressions remained unchanged, and PKCgamma and zeta failed to be detected. Fluorescence intensity of PKCalpha in KBV200 cells was increased. CONCLUSION: PKC might contribute to MDR phenotype in KBV200 cells, and of the isoforms so far detected, PKCalpha might play an important role in MDR phenotype.

Blotting, Western↗

PubMed2002

[Correlation of protein kinase C activity and its subcellular distrubution with multidrug resistance in KVB200 cells].

OBJECTIVE: To investigate the relationship between protein kinase C (PKC) and multidrug resistance (MDR) in cancer cell line KBV200. METHODS: MTT assay was used to evaluate the IC50 of vincristine (VCR) and adriamycin (ADR) in KB cell line and its VCR-resistant derivative KBV200 cells. PKC activities in the 2 cell lines were assayed by measuring the incorporation of (32)P from [gamma-(32)P] ATP into the peptide substrates. RESULTS: The IC50 values of VCR and ADR in KBV200 cells was 64.03 and 18.8 folds greater than those in KB cells. PKC activities of the membrane and cytosol fraction in KBV200 cells were increased compared with that in KB cells, with the total PKC activity 1.12-fold higher. Phorbol-12-myristate-13 -acetate increased PKC activity of the membrane fraction and IC50 values of KBV200 cells, while staurosporine worked to the opposite effects. CONCLUSION: PKC may contribute to MDR mechanism in KBV200 cells.

Antineoplastic Agents↗

PubMed2002

[Up-regulation of c-myc expression in MCF-7/Adr human breast cancer cells and its association with resistance against doxorubicin].

OBJECTIVE: To investigate the expression of c-myc in drug-resistant MCF-7/Adr human breast cancer cells and the counteractive effect of c-myc antisense oligonucleotide on their drug-resistance. METHODS: Flow cytometry was performed to examine c-myc expression in multi-drug resistant MCF-7/Adr cell line and its parental cell line MCF-7. The IC50 value of doxorubicin was evaluated by MTT assay. RESULTS: MCF-7/Adr cell line was shown to have a significantly higher expression rate of c-myc than its parent cell line MCF-7 (70.48% vs 46.02%). The IC50 value of doxorubicin was (22.00+/-1.92) micomol/L in MCF-7/Adr cells, which was significantly decreased to (9.60+/-1.04) micromol/L (P<0.05) after coincubation with 4 micromol/L c-myc antisense oligonecleotide. CONCLUSION: c-myc expression is up-regulated in MCF-7/Adr cells as compared with their parent cell line MCF-7. Inhibition of c-myc expression may partially reverse the resistance of MCF-7/Adr against doxorubicin, suggesting that c-myc may be involved in the mechanism of drug-resistance of tumor cells.

Antineoplastic Agents↗