Immunohistochemical analysis of Fas ligand expression in sarcomas. Sarcomas express high level of FasL in vivo

Fas ligand (FasL) and its receptor, Fas, play a key role in the regulation of apoptosis within the immune system. Several prior experimental studies of Fas ligand expression in tumors have suggested a mechanism that enables tumors to evade immune destruction by inducing apoptosis in activated lymphocytes near the tumor cells. Many types of carcinomas have been shown to express FasL, but at present nothing is known about the range of sarcomas capable of expressing FasL in vivo. The aim of this study was to determine the in vivo patterns of FasL expression in human sarcomas. Archival paraffin-embedded tissues of 57 sarcomas and 30 carcinomas were analyzed by immunohistochemistry for the expression of FasL. FasL immunoreactivity was seen in 39 of 57 (68%) sarcomas, including 10 of 10 rhabdomyosarcomas, 5 of 5 malignant schwannomas, 2 of 2 Ewing's sarcomas, 8 of 11 malignant fibrous histiocytomas, 4 of 5 angiosarcomas, 2 of 5 synovial sarcomas, 2 of 5 liposarcomas, 3 of 5 leiomyosarcomas, 2 of 6 osteosarcomas, and 1 of 3 chondrosarcomas. All carcinomas tested (10 gastric adenocarcinomas, 10 hepatocellular carcinomas, and 10 renal cell carcinomas) were positive for FasL. These results demonstrate that FasL expression in sarcomas, although less frequent than in carcinomas, is widespread among the sarcoma types, and suggest that FasL might contribute to the immune escape of sarcomas through killing Fas-bearing lymphocytes.

Changes in natural killer cell activity and prostaglandin E2 levels during the progression of diethylnitrosamine-induced hepatocarcinogenesis in Fischer 344 rats

The sequential changes of natural killer cell (NK) activity and prostaglandin E2 (PGE2) during hepatocarcinogenesis induced by diethylnitrosamine (DEN) in male Fischer 344 rats were investigated. DEN at a concentration of 40 ppm was administered in drinking water for 10 weeks. At weeks 5, 10, 20 and 30, rats were autopsied and the development of glutathione S-transferase placental form positive foci (GST-P+ foci) at weeks 5 and 10 and hepatocellular tumors at weeks 20 and 30 were examined. The labeling index of bromodeoxyuridine (BrdU) an indicator of DNA synthesis, was also sequentially checked. GST-P+ foci were found to increase with age. Hepatocellular nodules increased until week 20, but by week 30 when the incidence of hepatocellular carcinoma was 100%, the incidence of nodules had decreased. BrdU positive cells also increased with age, and by week 30 when the incidence of hepatocellular carcinoma was 100%, the number of BrdU-positive cells had decreased. NK cell activity increased until week 10, but at week 20, was less than in the untreated control group. The level of PGE2 increased until week 5, but at week 10, levels were not significantly different from those seen in the untreated control group. On the basis of these results, we concluded that NK activity is closely related to the progression of hepatocarcinogenesis, but PGE2 levels show no significant change.

Radiological features of focal nodular hyperplasia of the liver in children

BACKGROUND

Focal nodular hyperplasia (FNH) is an unusual hepatic tumour in children and should be distinguished from other hepatic lesions.

OBJECTIVE

To describe the imaging characteristics of FNH in children.

MATERIALS AND METHODS

We examined five patients (three boys and two girls, mean age 9.4 years) with pathologically confirmed FNH. The diagnosis was obtained by tumour resection (n = 4) and percutaneous needle biopsy (n = 1). One patient with multiple FNHs showed recurrent lesions after tumour resection. All patients were studied with US (including colour and power Doppler US [n = 3]) and CT. Dynamic enhanced CT scans were available in three patients. MRI (n = 2) or coeliac angiography (n = 1) was performed in three patients.

RESULTS

Seven of eight FNH lesions in five patients were demonstrated by imaging. The average size of the lesions was 6.5 cm. Six lesions detected on US showed variable echogenicity with a central hyperechoic scar (n = 2). On Doppler examination, central or peripheral hypervascular areas were seen (n = 3). Six lesions detected on contrast-enhanced CT showed high attenuation (n = 4) or iso-attenuation (n = 2). On early phase scans, all the lesions (n = 3) showed high attenuation. Irregular linear or ovoid central scars were detected in two patients on CT. MR demonstrated three lesions in two patients, one of which had not been detected by US or CT. A central low signal intensity scar (n = 1) was seen on T2-weighted MRI. Coeliac angiography performed in one patient showed a hypervascular mass with homogeneous staining.

CONCLUSION

FNH in children shows a wide spectrum of imaging findings on various radiological examinations and the typical central scar was not always seen on imaging studies. Dynamic enhanced CT obtained in the early phase and colour Doppler studies may be helpful in the diagnosis of FNH by allowing characterisation of tumour vascularity. FNH should be included in the differential diagnosis of liver mass in children.

Maternal or paternal exposure to radiation increases susceptibility to the induction of glutathione S-transferase-positive hepatic foci in offspring rats

Experiments were conducted to determine whether gamma-ray-induced genetic damage in parental rats can lead to the development of cancer in their offspring rats using glutathione S-transferase-positive (GST-P+) hepatic foci with or without the addition of diethylnitrosamine (DEN), a carcinogen. A single 1 Gy whole-body exposure of gamma-rays was given to pregnant rats at day 14 and during postnatal week 3, DEN was intraperitoneally injected twice in 1 week. Female pups from irradiated maternal and paternal rats were also used. Twelve weeks after birth, the rats were sacrificed. GST-P+ foci in animals subjected only to radiation were not different to those of normal control pups, but the incidence of GST-P+ foci was 2.4 times higher in pups treated with DEN alone at 3 weeks after birth than in those irradiated after the onset of pregnancy. In DEN-combined groups, irradiation of post-pregnant or maternal and paternal rats with gamma-rays before mating significantly increased both the incidence and area of GST-P+ foci when compared to those of rats treated with DEN alone. The proliferating cell nuclear antigen (PCNA) labeling index was significantly higher in the offspring of rats subjected to radiation alone or radiation combined with DEN than in normal control pups. Using a rat-liver model, the results of this study indicate that although the dose did not induce phenotypic malformation, exposure to radiation during the embryonic or pre-embryonic stage increases susceptibility to carcinogens.

Overexpression of cyclin D1 and cdk4 in tumorigenesis of sporadic hepatoblastomas

Abnormality of the cyclin D1/cdk4/p16INK4a/pRb pathway during tumorigenesis has recently been reported. Hepatoblastoma is a rare malignant liver tumor of childhood, but underlying abnormalities of cell-cycle regulating protein remain to be elucidated. The expression of cyclin D1, cdk4, p16 and retinoblastoma gene product (pRb) was studied by immunohistochemistry in 17 paraffin-embedded tissues consisting of both tumor and corresponding non-neoplastic tissues. Tumor tissues showed overexpression of cyclin D1 (13/17, 76%) and cdk4 (15/17, 88%). Eleven cases showed co-overexpression of both cyclin D1 and cdk4. No abnormal p16 or pRb expression was noted. In the group with a high score (+4) for cyclin D1 expression, a positive correlation with tumor recurrence was noted (P = 0.043). These data suggest that overexpressed cyclin D1 and cdk4 protein might play an important role in the tumorigenesis of hepatoblastoma and that in the group with high cyclin D1 expression, tumor recurrence may be more frequent.

Time course of cell cycle-related protein expression in diethylnitrosamine-initiated rat liver

BACKGROUND/AIMS

Cell cycle control and the relationship that exists between cellular proliferation, the expression of cell cycle control proteins and cancer have been reported. This study was designed to decipher the timing of cell cycle control protein expression during the initiation of diethylnitrosamine-induced rat hepatocarcinogenesis.

METHODS

Three-week-old female Sprague-Dawley rats were intraperitoneally injected twice in 1 week with diethylnitrosamine; after the second injection, all animals were sacrificed at 1, 2 and 24 h, and 3 and 7 days. The expression of cell cycle-related proteins such as CDK2 and 4, cyclin proteins (D1, E and cdc2), proliferating cell nuclear antigen, tumor suppressor proteins (p53 and Rb), CDK inhibitory proteins (p21waf1 and p27Kip1), and apoptosis-inhibiting protein (bcl-2) following diethylnitrosamine treatment was examined.

RESULTS

The peak induction time of each cell cycle-related protein during DEN-induced cellular proliferation was diverse, and expressions of CDK2, CDK4, cdc2, p53, bcl-2, p21Waf1 and p27Kip1 appear to be of the greatest interest.

CONCLUSIONS

Data generated from this study may provide information about cell cycle-related protein expression in the initiation stage of hepatocarcinogenic signaling pathways stimulated by a genotoxic agent such as diethylnitrosamine.

Frequent somatic mutations in serine/threonine kinase 11/Peutz-Jeghers syndrome gene in left-sided colon cancer

We analyzed somatic mutation and loss of heterozygosity (LOH) in the serine/threonine kinase 11 (STK11)/Peutz-Jeghers syndrome gene in 49 colorectal tumors in three different stages of a dysplasia-carcinoma sequence. We detected LOH in 10 of 19 (52.6%) informative colorectal cancers at loci D19S886 and/or D19S883, but no LOH was observed in 25 informative adenomas. We detected a total of 9 somatic mutations [7 of 13 (53.8%) left-sided colon cancers and 2 of 7 (28.6%) left-sided adenomas with high-grade dysplasia], but no mutations were detected in right-sided colon tumors. Of the nine mutations, one was a frameshift mutation (the same mutation detected in Peutz-Jeghers syndrome family previously), and the other eight were missense mutations. This results indicate that STK11 is a tumor suppressor gene and that genetic changes of STK11 play an important role in left-sided colon cancer carcinogenesis.

Fas ligand is expressed in normal skin and in some cutaneous malignancies

Fas, a cell surface receptor and member of the tumour necrosis factor receptor superfamily, induces apoptosis upon oligomerization by its ligand (Fas ligand: FasL). Detailed studies have revealed that Fas is broadly expressed in normal human tissues, but relatively little is known about the range of cell types capable of expressing FasL. The aim of this study was to determine the in vivo patterns of expression of Fas and FasL in human skin tissues. Immunohistochemistry was performed using paraffin-embedded samples of normal and neoplastic skin tissues. In normal skin, FasL was expressed in the epidermis, sebaceous glands, sweat glands and outer root sheath of the hair. In squamous cell carcinomas (SCC), all cases analysed expressed FasL at high levels, whereas 60% of basal cell carcinomas (BCC) were positive for FasL. Expression of Fas in normal skin was observed in the basal and spinous layers of the epidermis, the outer root sheath of the hair, and the sebaceous glands. Expression of Fas was observed in all the SCC tested and none of the BCC tested. Expression of FasL by normal cells and tumour cells in skin tissue, demonstrated for the first time in the present study, may provide an important clue to understanding skin physiology, and immune evasion of skin tumours.

Association of Helicobacter pylori infection with gastric adenocarcinoma

Gastric adenocarcinoma is the most prevalent cancer in South Korea, and Helicobacter pylori (H. pylori) infection is also common. This study was performed to examine the association between H. pylori infection and gastric cancer, taking into account various other factors. To investigate the association between gastric adenocarcinoma and H. pylori infection, determined by urease-positive reaction in the CLO test, a total of 175 paired specimens (175 tumor and 175 tissues adjacent to tumor) of stomach cancer patients and a total of 113 control specimens were obtained. The positive H. pylori infection rates were 78.9% (138/175) among the patients in specimens of tumor or tissues adjacent to the tumor and 41.6% (47/113) among controls in the CLO test. A positive correlation between H. pylori infection and gastric cancer was observed (age-adjusted odds ratio, 7.0; MH chi2=34.5 with P<0.0005). These data suggest that stomach cancer patients in Korea have high infection rates of H. pylori regardless of site specificity, and this infection might be causally associated with stomach cancer.

Differential expression of protein kinase C isoforms in diethylnitrosamine-initiated rat liver

Although protein kinase C (PKC), a family of 12 related isoforms, plays an important role in carcinogenesis, little is known about the specific role of each isoform in the initiation stage of hepatocarcinogenesis. The subcellular distribution of PKC isoforms in the early stages of diethylnitrosamine (DEN)-initiated hepatocarcinogenesis was therefore examined. Three-week-old female Sprague-Dawley rats were intraperitoneally injected twice in 1 week with DEN; all animals were sacrificed at 1, 2 and 24 h and 3 and 7 days after the second injection. PKCalpha and -beta expression in both cytosolic and particulate fractions decreased as a result of 1 h of DEN treatment and this effect lasted for 7 days. In both fractions, PKCepsilon expression showed a marked increase by DEN treatment, while the expression of PKCdelta and -zeta was almost unchanged. These results suggest that differential expression of PKC isoforms may play an important role in the early stage of DEN-initiated hepatocarcinogenesis in rats.

Nuclear overexpression of bcl-2 oncoprotein during the progression of human stomach cancer

We unexpectedly observed strong nuclear overexpression of bcl-2 protein in advanced stomach cancer. As far as we know, such expression has not yet been reported. To investigate the significance of nuclear expression of bcl-2 protein in gastric carcinoma, we immunohistochemically analyzed bcl-2 overexpression in a gastric carcinogenic sequence, including 19 tubular adenomas (TA), 20 early carcinomas (EGC), and 20 advanced carcinomas (AGC). While TA displayed a specific granular and supranuclear cytoplasmic staining pattern, adenocarcinomas showed a strong nuclear staining pattern. Nuclear staining of bcl-2 was observed in 50% of AGC, 30% of EGC, and 10% of TA; cytoplasmic staining, on the other hand, was observed in all TA, 5% of EGC, and 10% of AGC. Nuclear bcl-2 overexpression differed according to the histologic type of AGC, occurring in 67% of the diffuse type and 25% of the moderately-to-well differentiated type. In the diffuse type, nuclear bcl-2 positive AGC predominated. In metastatic lesions, the pattern of bcl-2 immunostaining was almost identical to that seen in primary tumor. These results suggest that nuclear expression of bcl-2 may be related to malignant transformation in the stomach and is frequently associated with diffuse type advanced gastric adenocarcinomas.

A distinct region of chromosome 19p13.3 associated with the sporadic form of adenoma malignum of the uterine cervix

Adenoma malignum (AM) is known to be one of the malignant tumors that is commonly associated with Peutz-Jeghers syndrome. Recently, the genetic locus of Peutz-Jeghers syndrome was mapped to the telomeric region of chromosome 19p. We analyzed nine sporadic cases of AM with high-density loss of heterozygosity to study the region of chromosome 19p13.2-13.3 using eight microsatellite markers. Our deletion mapping data revealed a distinct region with 100% loss of heterozygosity frequency at marker D19S216. This result indicates that a putative tumor suppressor gene for AM is located at D19S216 on chromosomal band 19p13.3 and plays an important role in AM tumorigenesis.

Increased susceptibility of the c-Myc overexpressing cell line, SNU-16, to TNF-alpha

Tumor necrosis factor-alpha (TNF-alpha) is a macrophage-derived multifunctional cytokine that acts as a cytostatic or cytotoxic agent in many tumor cells. However, the molecular mechanisms by which tumor cells become sensitive to the cytotoxic action of TNF-alpha are not clear. In this study we demonstrated that the cytotoxicity of TNF-alpha markedly increased in c-Myc overexpressing tumor cells. The stomach cancer cell line, SNU-16, in which c-Myc expression is high due to gene amplification, showed programmed cell death detected by DNA fragmentation and morphological changes. An antisense c-myc S-oligonucleotide specifically inhibited the TNF-alpha-induced apoptosis of SNU-16 cells, provided that the oligonucleotide was added 4 h prior to TNF-alpha treatment. Western immunoblot analysis of p53 and Bax showed that in this cell line, TNF-alpha increased the level of these proteins in a time-dependent manner and that this effect lasted for 12 h. Taken together these data indicate that the deregulation of c-Myc plays an important role in sensitizing tumor cells to TNF-alpha. Furthermore, TNF-alpha-induced apoptosis in the SNU-16 cell line showed increased expression of p53 and Bax protein levels following TNF-alpha treatment. Therefore, we suggest that TNF-alpha-induced apoptosis, which is cytotoxic to tumor cells, is coupled with a p53 and Bax apoptotic pathway.

Benzo[a]pyrene diol-epoxide-I-DNA and oxidative DNA adducts associated with gastric adenocarcinoma

BPDE-I-DNA and oxidative DNA adducts (8-OHdG) were investigated in stomach tissues (tumor and tumor-adjacent) of patients (N = 211) with gastric adenocarcinoma and in normal stomach tissues (N = 113). In each stomach specimen, the levels of BPDE-I-DNA adducts were quantitatively measured by enzyme linked immunosorbent assay (ELISA) and oxidative DNA damage was measured by HPLC-ECD. Higher levels of total BPDE-I-DNA adduct were observed in tumor (4.20 +/- 0.59 fmol/microg DNA) and tumor-adjacent (3.68 +/- 0.62 fmol/microg DNA) tissues than in normal stomach tissues (2.80 +/- 0.53 fmol/microg DNA) but were not significant. In males, BPDE-I-DNA adduct was significantly higher in tumor tissues (4.25 +/- 0.42 fmol/microg DNA) than in normal tissues (2.83 +/- 0.59 fmol/microg DNA) (P < 0.05). In smokers, BPDE-I-DNA adduct was slightly higher in tumor tissues (4.92 +/- 0.82 fmol/microg DNA) than in tumor-adjacent tissues (3.99 +/- 0.92 fmol/microg DNA). Gastric cancer patients had significantly higher levels of 8-OHdG in their tumor-adjacent (7.54 +/- 0.43 residues/10(5) dG) and tumor tissues (6.29 +/- 0.39 residues/10(5) dG) than in normal tissues (2.86 +/- 0.11 residues/10(5) dG) (P < 0.001). Smokers showed higher levels of 8-OHdG in both tumor (6.44 +/- 0.62 residues/10(5) dG) and tumor-adjacent (8.12 +/- 0.68 residues/10(5) dG) tissues than in non-smokers (5.80 +/- 0.47 and 7.11 +/- 0.57 residues/10(5) dG, respectively). 8-OHdG levels were significantly increased in positive tissues with Helicobacter pylori (H. pylori) infection compared with negative tissues (P < 0.01). Also, the frequency of H. pylori infection was higher in tumor-adjacent tissues (73%) than in tumor (42%) or normal tissues (44%). These results demonstrate that there are higher levels of 8-OHdG and BPDE-I-DNA adducts in tumor and tumor-adjacent tissues than in normal tissues and that these higher levels might be related to gastric tumorigenesis, although benzo[a]pyrene could be a minor contributing component in the environment.

Species, strain and sex differences in susceptibility to gamma radiation combined with diethylnitrosamine

Our previous data suggested that in Sprague-Dawley (SD) rats, a short-term in vivo radiation carcinogenesis model can be established using glutathione S-transferase placental form (GST-P) positive hepatic foci induced by diethylnitrosamine (DEN) after gamma radiation. In the present study, differences between species, strain and sexes in susceptibility to radiation or radiation combined with DEN were examined. Newborn Fischer 344 (F344) and SD rats, and N:GP(S) mice were irradiated with whole body single 3Gy of gamma rays with or without intraperitoneally-injected DEN (15 mg/kg body weight) within 1 h of irradiation. Three weeks later, 0.05% phenobarbital was given in drinking water as a promoter, and at week 21 after birth, all animals were sacrificed. In both the radiation alone and radiation combined with DEN groups, F344 rats were more susceptible than SD rats to the induction of GST-P+ foci. In F344 rats, no significant difference in foci induction was seen between the sexes in both radiation alone and radiation combined with DEN groups, but in SD rats, female rats were more susceptible than males. In the case of mice, lung tumor incidence was examined, and in the radiation alone group, no differences between the sexes were seen; in the radiation combined with DEN group, however, females were more susceptible than males. These results suggested that susceptibility to radiation carcinogenesis could be potentiated by chemical carcinogens and showed wide variation between species, strains and sexes, of experimental animals.

Loss of heterozygosity and somatic mutations of the VHL tumor suppressor gene in sporadic cerebellar hemangioblastomas

Cerebellar hemangioblastoma is a benign central nervous system neoplasm with characteristic proliferation of vascular and stromal cells. There is increasing evidence that the stromal cell population may represent the neoplastic component of hemangioblastoma, whereas the vascular component may be composed of reactive, nonneoplastic cells. Therefore, successful genetic testing for loss of heterozygosity requires selective analysis of target cell populations. Here, tissue microdissection was used to selectively analyze the stromal cell component of 20 archival sporadic cerebellar hemangioblastomas for loss of heterozygosity at the Von-Hippel Lindau (VHL) gene and somatic VHL gene mutations. Allelic deletions at the VHL gene locus were detected in the stromal cell component with one or more markers (D3S1038, D3S1110, and/or 104/105) in 10 of 19 (52.6%) informative cases. In all cases, heterozygosity at the VHL gene locus was retained in the vascular component. In two cases, aberrant bands in exon 2 of the VHL gene were demonstrated in the stromal cells by PCR-based single-strand conformation polymorphism analysis, and somatic missense mutations were successfully characterized in two of the sporadic hemangioblastomas by direct sequencing. The results suggest that allelic losses and mutations of the VHL tumor suppressor gene play a role in sporadic cerebellar hemangioblastoma tumorigenesis. Furthermore, because the genetic changes were detected in selectively procured stromal cell areas, the data provide strong evidence that the stromal cell represents a neoplastic component of hemangioblastoma.

Thymic epithelial tumor progression in an SV40T transgenic mouse model. Cortical thymoma-thymic carcinoma sequence

There have been several reports that thymoma in human is a progressive disease, and that thymoma and thymic carcinoma form a continuum. We established a stable line of SV40T transgenic mice, which consistently produced thymic epithelial tumours progressing to thymic carcinoma within a predictable time span. Using this animal model and a morphological approach, thymic epithelial tumour progression was studied with reference to sequential changes at different time points in animals aged from 3 to 32 weeks. At all ages, SV40T was expressed in the nuclei of thymic epithelial cells; in these transgenic mice we observed the entire spectrum from cortical type thymoma to thymic carcinoma. Thymic size tended to increase with ageing in SV40T TG mice. While younger mice had predominantly cortical (organoid) or cortical thymoma, older mice had well-differentiated thymic carcinoma (WDTC) or poorly differentiated thymic carcinoma. When SV40T TG mice (248 line) reached a certain age, carcinoma of the thymus was present in all of them. Cortical-type thymoma became malignant within a predictable time span, suggesting a cortical thymoma-carcinoma sequence. When the mice were 9 weeks of age, the thymuses formed gross masses compatible with cortical thymoma. At 14 weeks of age, WDTC appeared against the background of cortical thymoma. Poorly differentiated thymic carcinoma was found after 15 weeks and affected all animals over 23 weeks of age. Most thymic carcinomas coexisted in varying proportions with cortical-type thymoma. Medullary thymomas did not develop in the mice, and no transition from medullary-type thymomas to thymic carcinomas was observed. In this SV40T transgenic mouse model, thymic carcinoma is clearly preceded by cortical-type thymoma. These transgenic mice may provide an interesting model for the progression from cortical thymoma to WDTC and/or high-grade carcinoma.

Blockade of nitric oxide synthesis reduces myocardial oxygen consumption in vivo

BACKGROUND

Although cardiac myocytes and coronary vascular endothelium are known to express a constitutive form of NO synthase, the in vivo effects of tonic endogenous production of NO on myocardial O2 consumption and contractile performance remain unclear.

METHODS AND RESULTS

The effects of blockade of NO synthase were determined in intact dogs. Myocardial O2 consumption decreased systematically over a wide range of hemodynamic demand after the systemic administration of N omega-nitro-L-arginine methyl ester (L-NAME) or N omega-nitro-L-arginine. Decreases after doses of 1 and 10 mg/kg L-NAME averaged 23 +/- 3.8% and 34 +/- 7.2% at a heart rate of 90 bpm in open-chest animals. Similar reductions occurred after the administration of L-NAME and N omega-nitro-L-arginine in chronically instrumented animals and were unaffected by beta-adrenergic blockade. Intracoronary infusion of L-NAME in chronically instrumented animals reduced both myocardial O2 consumption and regional segment shortening, even at a dose that did not increase systemic arterial pressure.

CONCLUSIONS

The blockade of NO synthesis reduces myocardial O2 consumption in vivo. The decrease in O2 consumption is accompanied by a decrease in segment shortening. It involves a direct myocardial action of NO, is unaffected by beta-blockade, and is consistent with in vitro studies indicating that low levels of NO augment contractile performance by inhibition of a cGMP-dependent phosphodiesterase.

Epstein-Barr virus-associated primary gastrointestinal lymphoma in non-immunocompromised patients in Korea

We examined 81 cases of primary gastrointestinal lymphomas in Korea, including 64 gastric lymphomas and 17 intestinal lymphomas, for EBV expression by EBER-1 in situ hybridization (ISH) and EBNA-1 PCR. In EBER-1 positive cases, we performed immunohistochemistry for latent membrane protein-1 (LMP-1) and EBV diffuse early antigen (EA(D)) to compare EBV latent gene expression and lytic process. EBER-1 was detected in 15 of 81 cases of lymphomas. EBER-1 expression showed three different patterns on tumour cells; diffuse 4/81 (5%), localized 4/81 (8%), and a few scattered pattern 7/81 (9%). We regarded diffuse pattern and localized pattern as EBER-1 positive group (8/81: 10%). Diffuse pattern of EBER-1 was shown in all three T-cell lymphomas and one B-cell lymphoma. A localized pattern was seen all in B-cell lymphomas. The EBER-1 expression was 11% in the stomach (7/64) and 6% in the intestine (1/17). Five of the eight EBER-1 positive gastric lymphomas were histologically diffuse large B-cell lymphomas, and the other three were peripheral T-cell lymphoma, unspecified, one angiocentric lymphoma, and one intestinal T-cell lymphoma by REAL classification. Eight MALT type gastric B-cell lymphomas showed no EBV association. EBV nuclear antigen (EBNA-1) was detected in 15 of 45 resected cases (33%) by PCR. EBER-1 positive cases were all EBNA-1 positive. Twelve EBNA-positive/EBER-negative cases consisted of seven cases showing a few scattered EBER-1 positive lymphocytes. LMP-1 and diffuse early antigen (EA(D)) was detected in five and three cases, respectively. Although follow-up information in our series was incomplete, it seemed that there was no significant difference in their staging or prognosis between EBER-positive cases and EBER-negative group. It is concluded that EBV is associated with some lymphomas among Koreans without overt pre-existing immunodeficiency, especially in T-cell lymphomas.

Overexpression of tissue inhibitors of metalloproteinase-1 and -2 in the stroma of gastric cancer

The fundamental event of cancer invasion and metastasis is the complicated interaction of cancer cells with host cells, in which event, a number of proteases and their inhibitors are involved. Matrix metalloproteinases are the potent proteases in degrading the basement membrane and extra cellular matrix and are inhibited by specific endogeneous inhibitors, tissue inhibitors of metalloproteinases-1(TIMP-1) and TIMP-2. The expression of mRNA for TIMP-1 and -2 was investigated by Northern blot analysis in specimens taken from 27 patients with primary gastric adenocarcinoma; 25 samples from the primary site, six from the metastatic lymph nodes and two from the peritoneal fluids. The expression for TIMP-1 and -2 was compared in primary gastric cancer tissues, metastatic lymph nodes and normal gastric mucosae. TIMP-1 mRNA was overexpressed in 24 (96%) out of 25 primary cancer tissues compared with the paired normal mucosae, while TIMP-2 was in 10 (40%). In six specimens of metastatic lymph nodes, TIMP-1 and -2 were overexpressed in 6 (100%) and 4 (67%) specimens, respectively. Of two specimens prepared from the peritoneal fluids, all specimens overexpressed TIMP-1 compared with the those of primary cancer tissues, while one (50%) specimen overexpressed TIMP-2. Immunohistochemical staining was done to investigate the localization of TIMP-1 and -2, demonstrating that the immunoreactivity for TIMP-1 and -2 was clearly detected in the cytoplasm of the stromal cells. These results suggest that both TIMP-1 and -2 are overexpressed by stromal cells in most of primary and some metastatic gastric cancer tissues and that TIMP-1 and TIMP-2, produced by stromal cells, may play an important role in inhibiting the proteolytic activity of matrix metalloproteinases originated from cancer cells, in gastric cancer.

Primary malignant lymphomas of the stomach. Pathological and clinical analyses of 38 resected cases

The stomach is the most frequent site of extranodal lymphoma and primary gastric lymphoma might be distinguished from the nodal lymphoma by its different pathogenesis and prognosis. Based on the Isaacson's classification, clinico-pathologic reviews of 38 resected primary gastric lymphomas were done. Immunohistochemical stainings for PCNA, B and T cell markers, bcl-2 and p53 were performed. Eighteen were of low grade and 20 were of high grade. There were significant differences between low and high graders in the aspect of the size, depth of lesion, gross type, immunophenotype, staining intensity for PCNA, expressions of bcl-2 and p53. The overall 2-year survival rate was 85.3%. Factors with prognostic significance on survival by univariate analyses included immunophenotype, histologic grading and PCNA staining pattern. After multivariate analyses, immunophenotype proved to be a significant factor. We think that the histologic grading by Isaacson's classification and the immunohistochemical stainings performed were useful in pathologic and/or clinical aspects. The excellent survival rate in this study was partly due to the selection of resectable cases. However, earlier diagnosis and appropriate treatment might have contributed to the improved prognosis of gastric lymphoma in recent years.

Differential diagnosis of adenoid cystic carcinoma from pleomorphic adenoma of the salivary gland on fine needle aspiration cytology

OBJECTIVE

To evaluate the distinguishing morphologic features of pleomorphic adenoma and adenoid cystic carcinoma on fine needle aspiration cytology.

STUDY DESIGN

A retrospective study was undertaken to compare the cytomorphology of 9 adenoid cystic carcinomas with that of 12 pleomorphic adenomas of the salivary gland among histologically proven cases.

RESULTS

The most consistent finding for differentiating adenoid cystic carcinoma from pleomorphic adenoma in our study was the amount of cytoplasm of individual tumor cells. Plasmacytoid appearance is a reliable finding for pleomorphic adenoma, and it enables us to rule out adenoid cystic carcinoma. All 12 cases of pleomorphic adenoma showed tumor cells containing abundant cytoplasm in clusters and isolated cells, with plasma cell-like appearance in 9 cases, especially in isolated cells. In contrast with pleomorphic adenoma, most adenoid cystic carcinomas showed little cytoplasm. Hyaline spherical globules were found in four of nine adenoid cystic carcinomas but were not found in any case of pleomorphic adenoma. It was specific but not sensitive to adenoid cystic carcinoma. Fibrillary chondromyxoid ground substance and a mixture of epithelial cells with stroma were found in two-thirds of the pleomorphic adenomas in our cases. The pattern of cell clusters was helpful to differentiate pleomorphic adenoma from adenoid cystic carcinoma. Large, loose clusters with a spindle cell core suggested pleomorphic adenoma. Small, dense trabeculae with a smooth margin and dense clusters containing clear, round spaces were more suggestive of adenoid cystic carcinoma. Overall cellularity, proportion of isolated cells, orientation of cellular clusters and degree of cellular overlapping gave almost no help in making the distinction between the lesions.

CONCLUSION

A plasmacytoid appearance of individual tumor cells with abundant cytoplasm was a reliable finding in pleomorphic adenoma for differentiating it from adenoid cystic carcinoma. Practically, nuclear features were not enough to distinguish the two lesions in isolated cases.

Development of thymic carcinoma in transgenic mice expressing SV40 T antigen

We produced transgenic mice using SV40 Tag gene under the control of its own enhancer and promoter. Three transgenic lines (SNU-SVT125, 127, 248) consistently developed thymic carcinoma as well as choroid plexus carcinoma and dysplastic renal tubule. In SNU-SVT248 line, SV40 Tag transgene was expressed at thymus, spleen and kidney. Thymic epithelium showed high level expression of SV40 Tag in immunohistochemistry. Histopathological and electron microscopic analysis revealed that poorly differentiated carcinoma was derived from type 2 to 4 thymic epithelial cell. Our transgenic mice would provide a model for studies on the pathogenesis of thymic carcinoma and on the regulation of thymopoiesis by epithelial cells.

T cell lymphoma in transgenic mice expressing the human Hsp70 gene

In the course of studying the role of hsp70 in the differentiation of pancreatic beta cells, transgenic founder mice were generated with the human hsp70 gene fused to the human insulin gene promoter. One resulted in a transgenic line that consistently developed diabetes mellitus, but unexpectedly three other independent transgenic founders developed generalized malignant lymphoma within 10 months after birth. Immunochemical and RT-PCR analyses revealed that the transgene was expressed in the lymphoma cells. Flow cytometric analyses revealed that the tumor was originated from T lymphocytes. Our results provide the first experimental evidence that hsp70 is involved in the tumorigenesis of T cells most likely through the blockage of apoptotic signals.

CT findings in malignant tumors of thymic epithelium

OBJECTIVE

Differentiation of invasive thymoma from thymic carcinoma is important because of their different clinical behaviors. Retrospectively, we evaluated the CT findings of invasive thymomas and thymic carcinomas to determine the differential points between them.

MATERIALS AND METHODS

We reviewed the CT scans of 12 patients with invasive thymoma and 10 patients with thymic carcinoma that were confirmed by surgery or percutaneous needle aspiration. We analyzed CT scans, paying special attention to homogeneity, attenuation, invasion of adjacent mediastinal structures, pleural implants, mediastinal nodes, and extramediastinal metastases.

RESULTS

Most of the invasive thymomas and thymic carcinomas were homogeneous and isodense with chest wall muscle. Irregular infiltration into the adjacent organ suggesting invasion was seen in 11 patients (92%) with invasive thymoma and 8 patients (80%) with thymic carcinoma. Pleural implants were observed in four patients (33%) with invasive thymoma and one patient (10%) with thymic carcinoma. Mediastinal lymphadenopathy was seen in one patient (8%) with invasive thymoma and four patients (40%) with thymic carcinoma. Metastases to the lung, adrenal glands, or liver were observed in four patients (40%) with thymic carcinoma but none with invasive thymoma.

CONCLUSION

Despite the similarities of CT findings between invasive thymoma and thymic carcinoma, there are some differential points. Thymic carcinomas were infiltrating tumor and were more commonly associated with mediastinal nodes and extrathymic metastases, but less commonly associated with pleural implants than invasive thymoma.