Immunohistochemical detection of CDKN2, retinoblastoma and p53 gene products in primary astrocytic tumors

The expressions of p16(INK4), retinoblastoma (RB) and p53 protein were immunohistochemically examined in 70 primary astrocytic tumors. In 58 patients with high grade astrocytoma (18 anaplastic astrocytomas and 40 glioblastomas), 30 (51.1%) and 15 (25.9%) cases were undetectable for p16(INK4) and pRB, respectively, but their lack occurred infrequently in 12 low grade astrocytomas. The expression of p16(INK4) was inversely correlated with that of PRB, especially in glioblastomas. Accumulation of p53 was detected in 32 (45.7%) of 70 cases without any dependence on the grade. A deregulation of three tumor suppressor gene products most often occurs singly. Only patients with negative staining for pRB were significantly associated with a shorter survival time. Our findings suggest that loss of functional pRB at the G1/S check point may represent an important step in glioblastoma development and have a stronger negative impact on clinical outcome than p16(INK4) or p53 aberrations.

Direct clipping of a large basilar trunk aneurysm via the posterior petrosal (extended retrolabyrinthine presigmoid) approach--case report

A 53-year-old female presented with an unruptured, large basilar trunk aneurysm manifesting only as headache with no neurological deficits, including absence of cranial nerve dysfunction. Cerebral angiography disclosed a large aneurysm with a wide neck arising from the midbasilar artery. We treated the aneurysm surgically via the posterior petrosal approach. Five angled clips were applied sequentially to the aneurysm and the basilar artery was successfully reconstructed. Electrophysiological monitoring was continued during the operation and showed no changes. Following the operation, the patient suffered from transient right abducens nerve palsy, which persisted for 3 months. Postoperative angiography showed that the aneurysm was obliterated, and the patency of the basilar artery was preserved.

Ventral T-1 neurinoma removed via hemilaminectomy without costotransversectomy--case report

A 39-year-old male presented with a spinal neurinoma originating from the T-1 anterior root and located ventral to the spinal cord. The tumor was removed by hemilaminectomy with only partial facetectomy without costotransversectomy. No stabilization was necessary, and no complications secondary to surgery occurred. Costotransversectomy is not necessary for neurinoma ventral to the spinal cord within the spinal canal at T-1 level because the transverse process protrudes more laterally and the spinal canal of the T-1 vertebra is wider than at other thoracic levels.

Increased telomerase activity and absence of p53 mutation in oligoastrocytomas induced by N-ethyl-N-nitrosourea in rats

The question of whether the changes in telomerase activity and/or the alteration of the p53 gene are involved in the development of oligo-astrocytomas induced by N-ethyl-N-nitrosourea (ENU) in rats was addressed. Telomerase activity levels of oligo-astrocytomas, including early neoplastic lesions, were significantly increased as compared to the normal controls, correlating with the degree of malignancy. In contrast, no mutations of p53 exons 5-7 were found in early neoplastic lesions or oligo-astrocytomas. These results indicate that the activation of telomerase occurs during astrocytoma carcinogenesis and contributes to the development of brain tumors, but the alterations of p53, at least on exons 5-7, may not be involved in this process.

Genomic alterations of human gliomas detected by restriction landmark genomic scanning

Alterations of genomic DNA in eight primary astrocytic tumors and two glioma cell lines were examined using a recently developed two-dimensional gel electrophoresis method called restriction landmark genomic scanning (RLGS). RLGS allows us to detect amplifications, deletions, and methylation in genomic DNA in one procedure without requiring any polymorphic markers. Approximately 2000 spots (landmark sites) in tumor specimens were compared with those in normal brain tissue. The 10 spots with intensified signal were reproducibly detected in at least 50% of primary tumors, implying amplification of corresponding DNA sequences. Conversely, 12 spots with reduced signal were observed in more than 50% of all tumors, suggesting inactivation by allelic loss, homozygous deletion, or CpG island methylation. These results suggest that common genetic alterations are closely correlated with the genesis or progression of human gliomas.

Analyses of human gliomas by restriction landmark genomic scanning

The 16 primary gliomas were examined for changes in genomic DNA using a recently developed 2-dimensional gel electrophoresis method called restriction landmark genomic scanning (RLGS). This approach allows detection of DNA amplification, deletion, methylation and potentially other genetic rearrangements represented as decreases and increases in spot/fragment intensity on an autoradiogram. Approximately 2,000 landmark sites in tumor DNA were compared with those of DNA isolated from normal brain tissues. Seven spots showing intensified signal were consistently detected in at least 50% of tumors, implying activation of corresponding DNA sequences, and 8 additional spots having reduced signal were observed, again in more than 50% of all tumors, suggesting inactivation by the loss of 1 allele or homozygous deletion. Decreased signal may also infer relative CpG island methylation state. Of those spots consistently identified in tumors, 2 amplified and 4 reduced spots were found to be characteristic of low- and high-grade tumors, while the remaining 5 amplified and 4 reduced spots were associated with high-grade gliomas only, suggesting a link of specific mutations to degree of malignancy. A separate subset of glioblastomas evaluated, however, showed no alterations in these 'hot spots' which were detected in even low grade astrocytomas. The results demonstrate the genetic heterogeneity of glioblastoma and implicate the progression of neoplasia via differing genetic pathways.

Genomic alterations in human glioma cell lines detected by restriction landmark genomic scanning

Restriction landmark genomic scanning (RLGS) is a 2-dimensional gel analysis capable of detecting amplifications, deletions and rearrangements in genomic DNA. Using RLGS, we examined genomic DNA from each of 6 human-derived malignant glioma cell lines and from normal brain tissue samples. RLGS allows us to screen genomic DNAs as approximately 2,000 landmark sites in one procedure without any polymorphic markers. The resulting 2,000 spots in tumor samples were compared with those in normal brain. Six spots common to 5 of the 6 cell lines showed intensified signal, suggesting amplification of a tumor-specific DNA fragment. In addition, 25 spots common to 5 of the 6 lines showed a decrease in signal intensity, conversely indicating allelic loss of homozygous deletion. These results imply the existence of consistent genetic alterations in human glioma.

Shortened telomere length and increased telomerase activity in hamster pancreatic duct adenocarcinomas and cell lines

Recently, shortened telomere length and increased telomerase activity have been demonstrated in various human cancers. In the study reported here, we ascertained whether gene changes are characteristic of pancreatic cancers. Hamster duct carcinomas and cell lines were investigated by Southern blot analysis for telomere restriction fragment (TRF) length and by the telomeric repeat amplification protocol (TRAP) assay for telomerase activity. Comparison with normal pancreas and spleen revealed shortened TRF length and markedly increased telomerase activity in primary pancreatic duct carcinomas induced by the rapid-production model as well as in a transplantable carcinoma and the cell lines. The enzyme level was 86.0-215.7 times the low levels found in control pancreas and spleen tissues. Late-passage Syrian hamster embryo cells, known to be immortalized and tumorigenic, had shorter TRFs than the original cells in primary culture did. These results indicate that hamster pancreatic duct carcinoma cells are immortalized, with the potential for proliferation ad infinitum, and provide a model for basic therapeutic research into the substances targeting telomerase.

p53 mutation and absence of mdm2 amplification and Ki-ras mutation in 4-hydroxyamino quinoline 1-oxide induced transplantable osteosarcomas in rats

Previously, we reported the establishment of two transplantable osteosarcomas, one induced by local application of a carcinogen, 4-hydroxyamino quinoline 1-oxide(4-HAQO), and another which developed spontaneously in rats, and their subdivision into four lines with high and low metastatic potential to the lung. In the present study, mutations of p53 and Ki-ras genes were investigated by PCR and SSCP followed by direct sequencing, and the amplification of the mdm2 gene was assessed by Southern blot analysis. Mutations of p53 in exon 7 were detected in 4-HAQO-induced transplantable osteosarcomas, but not their spontaneous counterparts, irrespective of the metastatic potentials. Direct sequencing revealed a CGC to CAC transition with an amino acid change of Arg to His, at codon 246. Neither Ki-ras mutations nor mdm2 amplification were detected in any of the transplantable tumors. The results suggest that while p53 mutations occurred during osteosarcoma development by 4-HAQO without mdm2 amplification and Ki-ras mutation does not contribute to osteosarcoma development in rats.

Infrequent Ki-ras and an absence of p53 mutations in hepatocellular carcinomas induced by a choline deficient L-amino acid defined diet in rats

Mutations of Ki-ras and p53 genes in hepatocellular carcinomas (HCCs) induced by the choline deficient L-amino acid defined (CDAA) diet in rats were investigated by polymerase chain reaction (PCR), single strand conformation polymorphism (SSCP) analysis followed by direct sequencing. Male Fischer 344 rats, 6 weeks old, were continuously given a CDAA diet for 70 weeks and then sacrificed. Macroscopically detectable nodules which were histologically confirmed to be well-differentiated HCCs were dissected free from the surrounding tissue and subjected to gene mutation analysis along with samples of non-tumor areas. Conformational change in the Ki-ras gene was detected in 1 out of 7 HCCs, involving a GGC to GTC transversion at codon 13. No p53 mutations were detected in 7 HCCs and also neither Ki-ras nor p53 mutations were found in non-tumor areas. The results suggest that neither Ki-ras nor p53 genes play an important role in hepatocarcinogenesis caused by long term expose to a CDAA diet in rats.

Increased telomerase activity in hyperplastic nodules and hepatocellular carcinomas induced by a choline-deficient L-amino acid-defined diet in rats

Activation of telomerase has been reported in several human cancers, including hepatocellular carcinomas (HCCs). We investigated telomerase activity during hepatocarcinogenesis induced by a choline-deficient L-amino acid-defined (CDAA) diet in rats. Male F344 rats were given a CDAA diet or a choline-supplemented L-amino acid-defined (CSAA) diet from 6 weeks of age for 75 weeks, and subgroups were killed 10 weeks, 50 weeks and 75 weeks after the beginning of the experiment. Hyperplastic nodules and HCCs were noted in rats fed a CDAA diet for 50 weeks and 75 weeks, respectively. Normal control liver specimens were obtained from 6-week-old rats. Telomerase activity was assessed by using a telomeric repeat amplification protocol (TRAP). Normal liver and background parenchyma of rats fed either of the diets for 10 weeks or 50 weeks showed weak telomerase activity. In contrast, markedly increased levels were demonstrated in hyperplastic nodules and HCCs. These results suggest that increased telomerase activity may be a biological feature of preneoplastic lesions that evolve to HCCs in rat liver.

Enhancement of N-nitrosodiethylamine-initiated hepatocarcinogenesis caused by a colchicine-induced cell cycle disturbance in partially hepatectomized rats

The effects of a colchicine-induced M-phase block of regeneration after partial hepatectomy on early-stage liver carcinogenesis were studied in rats. When administered 1 or 3 days after N-diethylnitrosamine initiation and partial hepatectomy, colchicine increased the mitotic index of regenerating hepatocytes at days 4-6 without evidence of liver cell necrosis. When the protocol was combined with a selection procedure (E. Cayama et al., Nature (Lond.), 275: 60-62, 1978), a significant increase in the size but not number of gamma-glutamyltranspeptidase-positive foci at week 5 was observed in a colchicine dose-dependent manner. This was associated with an elevated incorporation of 5-bromo-2-deoxyuridine into the gamma-glutamyltranspeptidase-positive cells. In a longer-term experiment, the numbers, sizes, and 5-bromo-2-deoxyuridine labeling index of persistent nodules were increased significantly in colchicine-treated rats at week 9. This was associated with significant increases in the incidences and numbers of hepatocellular carcinomas at week 42. The above results raise the interesting possibility that a cell cycle disturbance in the early stage of liver carcinogenesis provides a persisting growth advantage for initiated cells, resulting in enhanced growth of foci and persistent nodules that evolve into hepatocellular carcinomas.

Shortened telomere length in hepatocellular carcinomas and corresponding background liver tissues of patients infected with hepatitis virus

The telomere length in 20 surgically resected human hepatocellular carcinomas (HCCs) and adjacent non-cancerous livers with hepatitis virus infection were investigated. All the HCC samples examined demonstrated shorter telomere length than the corresponding non-cancerous liver tissues, the respective average values being 5.4 kbp and 8.8 kbp (P < 0.001). The shortening of telomere length was most prominent in HCCs larger than 30 mm in diameter, and in both tumors and non-cancerous livers it was more marked with hepatitis B virus as compared with hepatitis C virus infection. These results indicate that telomere shortening is associated with not only progression, but also development of HCC, and there is a possible difference in the nature of the association in patients with hepatitis viruses of B and C types.

Telomere changes in human hepatocellular carcinomas and hepatitis virus infected noncancerous livers

BACKGROUND

Telomeres, at the ends of eukaryotic chromosomes, are defined functionally as necessary for chromosome stability. Chromosome instability induced in part by loss of telomeric DNA has been considered to play a significant role in the development of human cancers. However, little is known about the status of telomeres per se during human hepatocellular carcinoma (HCC) development.

METHODS

The study was conducted to determine the length of terminal restriction fragments (TRFs) at the telomeric ends in 23 HCCs and 23 corresponding noncancerous liver tissues from the same patients harboring hepatitis virus infections, and in 5 samples of noncancerous livers without the hepatitis virus. The latter samples had been obtained as controls at surgery for metastatic liver tumors.

RESULTS

All 23 HCCs demonstrated reduction in TRF length compared with the corresponding noncancerous liver tissues with viral infection. The TRF in the latter cases also demonstrated a significant shortening as compared with the virus free control tissue, the degree being calculated to represent an average of 42 cell divisions. Reduction in TRF length in HCC samples tended to increase with the tumor diameter, although this failed to show statistical significance.

CONCLUSIONS

These results indicate that telomere shortening occurs during HCC development. The fact that this change is already evident in noncancerous liver tissues from patients with viral hepatitis suggests that it may play an important role in the associated generation of tumors.

Disturbance of the cell cycle with colchicine enhances the growth advantage of diethylnitrosamine-initiated hepatocytes in rats

The effect of cell cycle disturbance due to colchicine on the induction of enzyme-altered foci during liver regeneration in rats was studied. For initiation, diethylnitrosamine (DEN) at a dose of 10 mg/kg was injected intraperitoneally and partial hepatectomy (PH) was performed 4 h thereafter. Colchicine at doses of 0, 0.1, 0.25 and 0.5 mg/kg was injected intraperitoneally 1 and 3 days after the initiation, followed by application of selection pressure consisting of 2-acetylaminofluorene (AAF) and carbon tetrachloride (CCl4) administration. As end point lesions, gamma-glutamyltransferase (GGT)-positive enzyme-altered foci were assayed at week 5. There was no significant effect of colchicine on numbers of foci. However, a significant, dose-dependent increase in the area of GGT-positive lesions in the groups treated with colchicine was observed. Bromodeoxyuridine labeling indices were higher in foci induced in colchicine-treated rats than in the untreated rats. In a separate experiment, serum glutamic pyruvic transaminase was not increased significantly after DEN and colchicine treatment, and the mitotic index at 6 days after PH was increased in the liver of colchicine-treated rats. These results suggest that the cell cycle disturbance induced by colchicine causes more pronounced selective growth of cells initiated by DEN and colchicine, and this experimental model may be useful for analyzing the mechanisms underlying that growth advantage and the effects of cell cycle abnormalities in liver carcinogenesis.

Anastomosis of occipital artery to posterior cerebral artery with interposition of superficial temporal artery using occipital interhemispheric transtentorial approach: case report

BACKGROUND

Superficial temporal artery (STA)-superior cerebellar artery (SCA) anastomosis, and STA-posterior cerebral artery (PCA) anastomosis are considered suitable as surgical procedures for the treatment of patients with significant stenosis or occlusion in the rostral portion of the basilar artery and patients with significant stenosis or occlusion of the posterior cerebral artery, respectively. However, several authors have reported frequent and serious complications of these surgical procedures, including temporal lobe retraction edema and hematoma. In this study, we introduce a new surgical revascularization using an occipital interhemispheric transtentorial approach for the treatment of severe stenosis of the rostral portion of the basilar artery.

CASE REPORT

A 47-year-old man with hypertension noted the sudden onset of nuchal pain followed by vertigo, diplopia, drunken gait, and motor weakness on his right side. Angiography performed on the day of the onset disclosed severe stenosis of the basilar artery. The stenotic portion extended just distal to the anterior-inferior cerebellar artery (AICA) to just proximal to the SCA, and in addition, a pseudolumen was visualized just distal to the left AICA. The patient underwent right occipital artery (OA) to left PCA anastomosis with interposition of the STA using an occipital interhemispheric transtentorial approach. Marked improvement in dysarthria, diplopia, ataxia gait, and visual disturbance were noted and he was able to walk without aid 3 days after operation. A postoperative angiogram of the right OA obtained 25 days after operation demonstrated visualization of the left PCA via the anastomosed OA and STA graft.

CONCLUSIONS

OA-PCA anastomosis with interposition of STA graft using an occipital interhemispheric transtentorial approach can be substituted for STA-SCA anastomosis and STA-PCA anastomosis for treatment of stenosis/occlusion of the rostral portion of the basilar artery.