Biomedical subjects

K W Kim

Publications and source records attributed to K W Kim.

At least 127 records · Page 7Linked to original sources

PubMed2000

Identification of angiogenic properties of insulin-like growth factor II in in vitro angiogenesis models.

Insulin-like growth factor II (IGF-II), highly expressed in a number of human tumours, has been recently known to promote neovascularization in vivo. Yet, the detailed mechanism by which IGF-II induces angiogenesis has not been well defined. In the present study, we explored an angiogenic activity of IGF-II in in vitro angiogenesis model. Human umbilical vein endothelial cells (HUVECs) treated with IGF-II rapidly aligned and formed a capillary-like network on Matrigel. In chemotaxis assay, IGF-II remarkably increased migration of HUVECs. A rapid and transient activation of p38 mitogen-activated protein kinase (p38 MAPK) and p125 focal adhesion kinase (p125FAK) phosphorylation was detected in HUVECs exposed to IGF-II. IGF-II also stimulated invasion of HUVECs through a polycarbonate filter coated with Matrigel. Quantitative gelatin-based zymography identified that matrix metalloproteinase-2 (MMP-2) activity generated from HUVECs was increased by IGF-II. This induction of MMP-2 activity was correlated with Northern blot analysis, showing in HUVECs that IGF-II increased the expression of MMP-2 mRNA, while it did not affect that of TIMP-2, a tissue inhibitor of MMP-2. These results provide the evidence that IGF-II directly induces angiogenesis by stimulating migration and morphological differentiation of endothelial cells, and suggest that IGF-II may play a crucial role in the progression of tumorigenesis by promoting the deleterious neovascularization.

Cell Movement↗

PubMed2000

A phase II study of a daily x4 schedule of vinorelbine plus cisplatin for advanced non-small cell lung cancer.

BACKGROUND: Because dose intensity may be important as a determinant response to vinorelbine, we explored the possibility of increasing the dose intensity of vinorelbine on a daily x4 schedule. METHODS: Between February 1998 and March 1999, 31 patients with previously untreated advanced non-small cell lung cancer were enrolled. Vinorelbine 15 mg/m2 and cisplatin 20 mg/ m2 were administered intravenously daily for 4 days and repeated every 21 days. RESULTS: A total 96 cycles were administered (median 3, range 1-6); 42% of vinorelbine and 39% of cisplatin injections were dose-reduced or delayed owing to toxicity. The actual dose intensity (DI) of vinorelbine was 17.7 mg/m2/week and that of cisplatin was 24 mg/m2/week. These figures represent 88 and 90% of the theoretical DI, respectively. The overall response rate was 40% (12/30, one CR). The main toxicity was myelosuppression: granulocytopenia WHO grade 3 and 4 in 24 patients (77%) and thrombocytopenia grade 3 in two patients (6%). The non-hematological toxicity was mild and tolerable. After a median follow-up of 7.5 months (range 3-21 months), the median progression-free survival and overall survival times were 5 months (95% CI, 3.8-6.2) and 8 months (95% CI, 4.5-11.5), respectively. CONCLUSIONS: This regimen has a comparable therapeutic activity in patients with advanced lung cancers. However, despite supportive care there were excessive hematological toxicities. In view of increased toxicity and similar efficacy, this regimen is not indicated outside a clinical trial.

Adult↗

PubMed2000

Contralateral EEG slowing and amobarbital distribution in Wada test: an intracarotid SPECT study.

PURPOSE: To relate the occurrence of contralateral electroencephalogram slowing (CES) to amobarbital distribution, we performed electroencephalogram (EEG) monitoring and intracarotid single photon emission computed tomography (SPECT) during an intracarotid amobarbital procedure (IAP). METHODS: IAP was performed on 22 patients with temporal lobe epilepsy. CES was defined as the occurrence of significant EEG slowing on the contralateral hemisphere (>50% of the ipsilateral hemisphere slowing) after amobarbital injection. To map the distribution of the amobarbital, we injected a mixture of amobarbital and (99m)technetium-ethylcysteinate dimer (99mTc-ECD) into the internal carotid artery and performed a brain SPECT 2 h later. In the SPECT images, regions of interest were determined by ipsilateral and contralateral anterior cerebral artery territories (iACA, cACA), ipsilateral and contralateral middle cerebral artery territories (iMCA, cMCA), and ipsilateral and contralateral posterior cerebral artery territories (iPCA, cPCA), as well as ipsilateral and contralateral anterior and posterior mesial temporal regions (iAMT, cAMT, iPMT, cPMT). The perfusion of amobarbital was interpreted visually in each region. RESULTS: Amobarbital was distributed in the iMCA in all the patients; in the iACA in 20 (90.9%) patients; in the iAMT in 14 (63.5%); and in the iPCA and iPMT in only two (9.1%). CES was observed in 13 (59.1%) patients. Cross-perfusion of amobarbital in limited areas of the cACA were observed in only four of 13 patients. Wada retention memory scores (WRMS) showed no significant difference between the CES- (n = 9) and CES+ (n = 13) groups. CONCLUSIONS: Amobarbital rarely perfused the iPCA territory and the iPMT region and was rarely delivered to the contralateral hemisphere. The occurrence of CES was not related to the cross-perfusion of amobarbital. CES appears to be produced by a transient functional disconnection from the ipsilateral hemisphere.

Adolescent↗

PubMed2000

Hepatic cavernous hemangioma: temporal peritumoral enhancement during multiphase dynamic MR imaging.

PURPOSE: To determine whether temporal parenchymal enhancement around hepatic cavernous hemangiomas can be correlated with the rapidity of intratumoral contrast material enhancement and/or tumor volume at dynamic magnetic resonance (MR) imaging. MATERIALS AND METHODS: Dynamic MR images obtained in 94 patients with 167 hemangiomas were retrospectively reviewed for peritumoral enhancement. Tumor volume was estimated by using the longest dimension on nonenhanced images. Speed of intratumoral contrast material enhancement was determined with early nonequilibrium phase images and was categorized as rapid (>75% of tumor volume), intermediate (25%-75% of tumor volume), or slow (<25% of tumor volume). RESULTS: Thirty-two of the 167 hemangiomas (19%) had temporal peritumoral enhancement, which was more common in hemangiomas with rapid enhancement (20 of 49 [41%]) than in those with intermediate (12 of 62 [19%]) and slow (0 of 56 [0%]) enhancement (P: <.001). The mean diameter of the hemangiomas with peritumoral enhancement was not significantly different from that of hemangiomas without peritumoral enhancement (P: >.05). Hemangiomas with rapid enhancement (mean diameter, 16 mm +/- 8), however, were significantly smaller than those with intermediate enhancement (mean diameter, 33 mm +/- 34) (P: <.001). CONCLUSION: Temporal peritumoral enhancement on dynamic MR images of hepatic hemangiomas correlates well with the speed of intratumoral contrast material enhancement and was most commonly encountered in rapidly enhancing small lesions. There was no statistically significant relationship, however, between peritumoral enhancement and tumor volume.

Adult↗

PubMed2000

Nontumorous hepatic arterial-portal venous shunts: MR imaging findings.

PURPOSE: To determine the magnetic resonance (MR) imaging findings of small nontumorous hepatic arterial-portal venous (arterioportal) shunts in the liver. MATERIALS AND METHODS: MR images in 25 patients with 38 small nontumorous arterioportal shunts verified with surgery or follow-up imaging were included in this study. The causes of arterioportal shunts were iatrogenic causes in 11 patients and/or cirrhotic changes in the remaining patients. Nonenhanced T1- and T2-weighted images and multiphase contrast material-enhanced dynamic images were retrospectively reviewed and compared with conventional hepatic arteriograms to determine the MR characteristics related to the focal hemodynamic changes. RESULTS: On arterial-dominant-phase dynamic MR images, 29 (76%) of the 38 arteriographically suggested nontumorous arterioportal shunts displayed abnormal findings distinguished against the surrounding hepatic parenchyma, including wedge-shaped (n = 14), nodular (n = 9), or irregularly outlined (n = 6) areas of focal contrast enhancement. The signal intensity on nonenhanced T1- and T2-weighted images of the corresponding areas appeared unremarkable except for three wedge-shaped high-signal-intensity areas (three [8%] of 38) on T2-weighted images accompanied by prolonged contrast enhancement. Most (24 [83%] of 29) areas of abnormal signal intensity were located at the periphery of the liver parenchyma. CONCLUSION: A small nontumorous arterioportal shunt should be considered one of the causes of focal parenchymal hyperperfusion abnormalities on contrast-enhanced dynamic MR images of the liver in the absence of abnormal signal intensity on static MR images.

Adult↗

PubMed2000

Significance of Pro12Ala mutation in peroxisome proliferator-activated receptor-gamma2 in Korean diabetic and obese subjects.

Peroxisome proliferator-activated receptors (PPARs) are a nuclear hormone receptor superfamily of ligand-activated transcription factors, and the PPARgamma subtype regulates adipocyte differentiation, lipid metabolism, and insulin sensitivity. There have been several reports on the relationship between the PPARgamma2 Pro12Ala genotype and obesity or diabetes in Caucasians. The objective of this study was to examine the relationship between this mutation and obesity or diabetes in Korean subjects. Two hundred and twenty-nine Korean subjects, including 111 obese subjects (body mass index, >25 kg/m2) were included in this study. One hundred and eleven subjects had normal glucose tolerance, 60 had impaired glucose tolerance, and 58 had diabetes mellitus. We evaluated these subjects for the Pro12Ala mutation in the PPARgamma gene using PCR-restriction fragment length polymorphism. Allele frequencies of the Pro12Ala missense mutation of PPARgamma2 were not different among Korean subjects with normal glucose tolerance (qAla = 0.045), those with impaired glucose tolerance (qAla = 0.033), and those with diabetes mellitus (qAla = 0.043; P > 0.05). Allele frequencies of PPARgamma2 Ala in obese subjects (qAla = 0.036) were not significantly different from those in nonobese subjects (qAla = 0.047). These results suggest that the Pro12Ala mutation in PPARgamma is not associated with either diabetes or obesity and may not be an important determinant of obesity or diabetes in Korean subjects.

Alanine↗

PubMed2000

Muscarinic receptors controlling the carbachol-activated nonselective cationic current in guinea pig gastric smooth muscle cells.

Muscarinic receptor subtypes controlling the nonselective cationic current in response to carbachol (ICCh) were studied in circular smooth muscle cells of the guinea pig gastric antrum using putative muscarinic agonists and antagonists. Both oxotremorine-M (an M2-selective agonist) and CCh dose-dependently activated the cationic current with EC50 values of 0.21 +/- 0.01 microm and 0.97 +/- 0.06 microM, respectively. In contrast, pilocarpine and McN-A 343 (an M1-selective and a putative M4 agonist) were weak partial agonists. In response to 10/microM CCh, 4-DAMP, methoctramine and pirenzepine dose-dependently inhibited ICCh and had IC50 values of 1.91 +/- 0.2 nM, 0.46 +/- 0.07 microM and 8.33 +/- 0.4 microM, respectively. 4-DAMP, methoctramine and pirenzepine shifted the concentration-response curves of ICCh to the right without significantly reducing the maximal current. Values of the apparent dissociation constant pA2 obtained from Schild plot analysis were 9.24, 7.72 and 6.62 for 4-DAMP, methoctramine and pirenzepine, respectively. Also, pertussis toxin completely blocked ICCh generation. These results suggest that the M2-subtype plays a crucial role in the activation of the ICCh, and a block of the M3-subtype reduces the sensitivity of the M2-mediated response with no significant reduction of maximum response.

Animals↗

PubMed2000

Arthroplasty of the hip in patients with aplastic anemia.

BACKGROUND: Patients with aplastic anemia are now living longer and therefore are at increased risk for the development of osteonecrosis of the hip. However, studies on the results of arthroplasty for the treatment of osteoarthritis of the hip in patients with aplastic anemia are lacking. METHODS: Twenty-six primary hip prostheses (one bipolar prosthesis fixed with cement, two bipolar prostheses fixed without cement, three hybrid total hip prostheses, and twenty total hip prostheses fixed without cement) were implanted, between March 1990 and May 1992, in nineteen patients who had been diagnosed with aplastic anemia. A specific prospective protocol was followed for the perioperative transfusion of platelets and blood. Twenty-five hips were replaced because of osteonecrosis of the femoral head, and one was replaced because of a femoral neck fracture. The patients were followed prospectively, with preoperative and serial postoperative Harris hip ratings as well as radiographs, for a minimum of six years or until death. RESULTS: No patient had excessive perioperative bleeding or a postoperative infection. After a mean duration of follow-up of seventy-nine months (range, seventy-two to ninety-five months), two patients had died with the original implant in place. No patients were lost to follow-up. The mean Harris hip score was 55 points (range, 42 to 68 points) preoperatively and 87 points (range, 56 to 95 points) at the time of the latest follow-up. At the time of this writing, no hip had been revised. One patient with a bipolar prosthesis had radiographic evidence of femoral loosening and will probably require revision. A second patient had some medial protrusion of a bipolar prosthesis, with mild symptoms. All of the acetabular components that had been fixed without cement and all of the other femoral components appeared to be stable on radiographs after a minimum of seventy-two months of follow-up. CONCLUSIONS: Total hip arthroplasty can be performed safely in patients with aplastic anemia. In the present intermediate-term study, the durability of implant fixation was maintained and the clinical results demonstrated a sustained increase in function of the hip.

Adult↗

PubMed2000

Background nonselective cationic current and the resting membrane potential in rabbit aorta endothelial cells.

The ion channel conductances that regulate the membrane potential was investigated by using a perforated patch-clamp technique in rabbit aorta endothelial cells (RAECs). The whole-cell current/voltage (I-V) relation showed a slight outward rectification under physiological ionic conditions. The resting membrane potential was -23.3 +/- 1.1 mV (mean +/- SEM, n = 19). The slope conductances at the potentials of -80 and 50 mV were 31.0 +/- 4.0 and 62.8 +/- 7.1 pS pF(-1), respectively (n = 15). Changes in the extracellular and intracellular Cl(-) concentrations did not affect the reversal potential on I-V curves. The background nonselective cationic (NSC) current was isolated after the K(+) current was suppressed. The relative permeabilities calculated from the changes in reversal potentials using the constant-field theory were P(K):P(Cs):P(Na):P(Li) = 1:0.87:0.40:0.27 and P(Cs):P(Ca) = 1:0.21. Increases in the external Ca(2+) decreased the background NSC current in a dose-dependent manner. The concentration for half block by Ca(2+) was 1.1 +/- 0.3 mM (n = 7). Through the continuous recording of the membrane potential in a current-clamp mode, it was found that the background NSC conductance is the major determinant of resting membrane potential. Taken together, it could be concluded that the background NSC channels function as the major determinant for the resting membrane potential and can be responsible for the background Ca(2+) entry pathway in freshly isolated RAECs.

Animals↗

PubMed2000

Zinc as a paracrine effector in pancreatic islet cell death.

Because of a huge amount of Zn2+ in secretory granules of pancreatic islet beta-cells, Zn2+ released in certain conditions might affect the function or survival of islet cells. We studied potential paracrine effects of endogenous Zn2+ on beta-cell death. Zn2+ induced insulinoma/islet cell death in a dose-dependent manner. Chelation of released endogenous Zn2+ by CaEDTA significantly decreased streptozotocin (STZ)-induced islet cell death in an in vitro culture system simulating in vivo circumstances but not in the conventional culture system. Zn2+ chelation in vivo by continuous CaEDTA infusion significantly decreased the incidence of diabetes after STZ administration. N-(6-methoxy-quinolyl)-para-toluene-sulfonamide staining revealed that Zn2+ was densely deposited in degenerating islet cells 24 h after STZ treatment, which was decreased by CaEDTA infusion. We show here that Zn2+ is not a passive element for insulin storage but an active participant in islet cell death in certain conditions, which in time might contribute to the development of diabetes in aged people.

Biological Transport↗

PubMed2000

Production of hydrogen peroxide by serum and its involvement in cell proliferation in ROS 17/2.8 osteoblasts.

The effects of hydrogen peroxide, which fetal bovine serum (FBS) releases, on proliferation have been studied in ROS 17/2.8 osteoblasts. Cell proliferation, when activated by FBS, was inhibited by catalase in ROS 17/2.8 osteoblasts, but did not in primary osteoblast-like cells. Serum-induced extracellular signal-regulated kinase(ERK) activity was reduced by the pretreated catalase in ROS 17/2.8 osteoblasts. In addition, the present studies demonstrate that addition of FBS led to an increase of fluorescence of dihydrorhodamine 123, indicating formation of free radicals including hydrogen peroxide in ROS 17/2.8 osteoblasts, but not in primary osteoblast-like cells. These phenomena may account for the generation of reactive oxygen species during cellular proliferation in ROS 17/2.8 osteoblasts.

Animals↗

PubMed2000

Toxic amebic colitis coexisting with intestinal tuberculosis.

A patient with a fulminant amebic colitis coexisting with intestinal tuberculosis had a sudden onset of crampy abdominal pain, mucoid diarrhea, anorexia, fever and vomiting with signs of positive peritoneal irritation. Fulminant amebic colitis occurring together with intestinal tuberculosis is an uncommon event and may present an interesting patho-etiological relationship. The diagnosis was proven by histopathologic examination of resected specimen. Subtotal colectomy including segmental resection of ileum, about 80 cm in length, followed by exteriorization of both ends, was performed in an emergency basis. Despite all measures, the patient died on the sixth postoperative day. The exact relationship of fulminant amebic colitis and intestinal tuberculosis is speculative but the possibility of a cause and effect relationship exists. Fulminant amebic colitis may readily be confused with other types of inflammatory bowel disease, such as idiopathic ulcerative colitis, Crohn's disease, perforated diverticulitis and appendicitis with perforation. This report draws attention to the resurgence of tuberculosis and amebiasis in Korea, and the need for the high degree of caution required to detect it.

Diagnosis, Differential↗

PubMed2000

Test-bolus injection for optimization of arterial phase imaging during contrast-enhanced hepatic MR imaging.

Contrast enhancement during the dynamic MR imaging is important for the detection and characterization of focal liver lesions. The purpose of this study was to determine whether or not a timing examination with a injection of a 1.0-mL bolus of gadopentetate dimeglumine into the antecubital vein followed by rapid dynamic scanning and measurement of signal intensity of the aorta could help to obtain proper arterial-dominant phase images for the characterization of focal hepatic lesions during subsequent multiphase dynamic MR imaging. The imaging delay to acquisition of the first gadolinium-enhanced image for multiphase dynamic MR imaging was set to equal the time to peak aortic enhancement during the test examination. The first contrast-enhanced images of 80 patients with 160 focal liver lesions (hepatocellular carcinoma, n = 79; cavernous hemangioma, n = 51; metastatic tumor, n = 30) were then retrospectively reviewed. Peak aortic enhancement occurred between 10 and 28 seconds (mean, 16.5 seconds +/- 3.1) after starting the infusion of contrast material in 80 patients during the test-examination. Depending on the findings of intrahepatic vascular enhancement on the full-scale dynamic images, hepatic arterial phase (n = 11, 14%) or sinusoid phase (n = 65, 81%) imaging was obtained during the first gadolinium-enhanced acquisition in 76 (95%) of 80 patients. Three different lesions were well characterized and easily distinguished from each other (p < .0001) on the first-phase images depending on their enhancement pattern. In the majority of patients, timing examination with test-bolus injection was helpful in obtaining qualified images for the characterization of various focal lesions.

Adult↗

PubMed2000

A case of minute intraductal papillary mucinous tumor of the pancreas presenting with recurrent acute pancreatitis.

Intraductal papillary mucinous tumor (IPMT) of the pancreas, a lesion consisting of mucin-producing cells with neoplastic potential, is characterized by duct ectasia, mucin hypersecretion, often extensive papillary intraductal growth, varying degrees of cytologic atypia, and relatively indolent growth. The clinical presentation of IPMT of the pancreas is characterized by chronic or recurrent attacks of abdominal discomfort often in association with low level pancreatic enzyme elevations. Less commonly these lesions may be detected as asymptomatic radiographic abnormalities. Interestingly, a case of a minute IPMT (2 mm in height and 7 mm in length, adenoma) in the main pancreatic duct presenting with acute pancreatitis in a 55 year-old man has been reported in the Japanese literature. Recently, we also experienced a case of a minute IPMT in a branch pancreatic duct causing repeated bouts of acute pancreatitis in a 75 year-old man. A filling defect at the neck of the main pancreatic duct seen on an endoscopic retrograde pancreatogram performed after recovery of the second attack of acute pancreatitis led the patient to undergo an exploratory laparotomy. After a near-total pancreatectomy was carried out, a minute (3 x 7 mm) IPMT of borderline malignancy was discovered in a branch duct at the head portion near the pancreatic neck without any lesions in the main pancreatic duct. Surprisingly, despite the resective surgery the patient died of carcinomatosis 8.5 months after the operation. We herein report a case of a minute but aggressive IPMT of the pancreas with a review of the literature.

Acute Disease↗

PubMed2000

Focal lesions in cirrhotic liver: comparing MR imaging during arterial portography with Gd-enhanced dynamic MR imaging.

The purpose of this study was to document the additional value of MR imaging during arterial portography (MRAP) in patients examined with intravenous contrast-enhanced dynamic MR imaging for the assessment of focal lesions in patients with cirrhosis or chronic viral hepatitis. The MR images of 24 patients with 39 hepatocellular carcinomas and 18 benign hepatocellular nodules examined with dynamic MR imaging and MRAP within a 14-day interval were retrospectively reviewed. For 39 hepatocellular carcinomas, MRAP revealed 37 perfusion defects (95%), while dynamic MR imaging demonstrated 35 occurrences of nodular contrast-enhancement (90%) on arterial dominant phases. Among the 11 benign nodules misinterpreted as hepatocellular carcinoma due to their high signal intensities on arterial-dominant phases of dynamic MR imaging, eight (73%) showed intratumoral portal venous perfusion on MRAP and were regarded as benign nodules. As a result of its high sensitivity and its potential ability to enable differentiation of benign and malignant hepatocellular nodules, MRAP can be added to dynamic MR imaging for planning future management in patients with equivocal hepatocellular nodules in the cirrhotic liver.

Adult↗

PubMed2000

Induction of apoptosis by ursolic acid through activation of caspases and down-regulation of c-IAPs in human prostate epithelial cells.

Previous results indicate that ursolic acid (UA), a pentacyclic triterpene acid, has strong cytotoxic activity and effectively induces growth arrest in a variety of systems. However, the molecular mechanisms underlying anti-tumorigenic or chemopreventive activities of UA are poorly understood. To further determine the mechanism of UA, we investigated the effects of UA on the growth of human prostate epithelial cells. Upon treatment with UA, a concentration-dependent inhibition of cell viability was observed and cells developed many of the hallmark features of apoptosis, including condensation of chromatin and DNA fragmentation. These apoptotic effects of UA were accompanied by proteolytic cleavage of specific target proteins such as PARP, beta-catenin and Rad51 proteins suggesting the possible involvement of caspases. Western blotting and in vitro assay demonstrated that processing/activation of at least four caspases (caspase-1, -3, -8 and -9) accompanies the generation of UA-mediating apoptotic cell death. In addition to activation of caspases, the down-regulation of c-IAPs family proteins, which suppress the apoptotic death signaling by the direct inhibition of activated caspases, was also observed. However, UA did not affect both the level of p53 expression and the alteration of the balance between Bcl-2 and Bax expression. These data suggest that apoptotic signals evoked by UA treatment may converge caspases activation through down-regulation of c-IAPs family and without mitochondrial dysfunction.

Antineoplastic Agents, Phytogenic↗

PubMed1999

Association between apolipoprotein E polymorphism and Alzheimer's disease in Koreans.

We analyzed the aplolipoprotein E (APOE) genotypes of 110 probable AD patients and 226 cognitively normal controls in Koreans. The APOE epsilon4 allele was more prevalent in both early- and late-onset AD patients (P < 0.01) than in controls. The odds for the APOE epsilon4-heterozygous subjects were 2.7 (95% CI = 1.6-4.5), and those for the APOE epsilon4-homozygous subjects were 17.4 (95% CI = 2.0-147.3). But the odds were not uniform across age groups, and were higher in women than in men. Although the APOE epsilon2 allele frequency did not differ by diagnosis, the patients carrying an APOE epsilon2 allele showed delayed age-at-onset (P = 0.02). In conclusion, the APOE e4 allele increased the risk for AD in dose-dependent manner, and the APOE epsilon4-conferred AD risk was age- and sex-dependent in Koreans.

Age of Onset↗

PubMed1999

Egr-1 mediates transcriptional activation of IGF-II gene in response to hypoxia.

We have previously reported that the exposure of human HepG2 cells to hypoxic conditions results in the overexpression of human insulin-like growth factor II (IGF-II) mRNA whose size is 6.0 kb. This particular size of IGF-II mRNA is transcribed under the control of the IGF-II P3 promoter. In the present study, to delineate the molecular mechanism for the activation of the IGF-II gene, we examined the induction of P3 promoter activity in HepG2 cells by hypoxia in the transient expression system. In this system, hypoxia induced a linear increase within 24 h in the expression of luciferase that was driven by the IGF-II P3 promoter. To further delineate which factors mediate this response, the expression pattern of regulators of the P3 promoter, Egr-1, Sp1, and WT1, were analyzed by reverse transcription-PCR and Northern blot analysis. We found that hypoxia increased the expression of Egr-1 but not of Sp1. In contrast, the level of WT1, a repressor of IGF-II expression, was markedly decreased during hypoxia. The mRNA stability assay revealed that the induction of transcription is the mechanism of underlying Egr-1 mRNA elevation. We then investigated the effects of hypoxia on the DNA binding activity of Egr-1. Both electrophoretic mobility shift assay and supershift assay demonstrated that the DNA binding activity of the Egr-1 protein was increased by hypoxia. In addition, the level of Egr-1 protein was also increased under the hypoxia as determined by Western blot analysis. Cotransfection of HepG2 cells with an Egr-1 expression vector and an IGF-II P3 promoter-luciferase reporter plasmid showed that the transcription of IGF-II was activated by Egr-1 in a dose-dependent manner. Moreover, the elevation of IGF-II P3 promoter activity was induced synergistically by the cotreatment of hypoxia with Egr-1 overexpression. Deletion of sequences in the IGF-II P3 promoter containing Egr-1 binding sites did not respond to hypoxic stress. Taken together, these data strongly indicate that hypoxia-induced IGF-II expression in HepG2 cells is due to the enhanced activity of Egr-1 on the IGF-II P3 promoter and that the Egr-1 binding site in the IGF-II P3 promoter is essential for the transcriptional regulation of IGF-II under hypoxic conditions.

Carcinoma, Hepatocellular↗