Case report: Clinically mild encephalitis/encephalopathy with a reversible splenial lesion: an autopsy case.

Clinically mild encephalitis/encephalopathy with a reversible splenial lesion is a clinicoradiological syndrome characterized by transient neuropsychiatric symptoms and hyperintensity of the splenium of the corpus callosum on diffusion-weighted MRI. Although intramyelinic edema and inflammatory cell infiltration can be predicted by MRI, the pathology of the splenium of the corpus callosum remains unknown. We encountered a case of clinically mild encephalitis/encephalopathy with a reversible splenial lesion and hypoglycemia in a patient who died of sepsis, and an autopsy was performed. The postmortem pathological findings included intramyelinic edema, myelin pallor, loss of fibrous astrocytes, microglial reactions, and minimal lymphocytic infiltration in the parenchyma. Based on these findings, transient demyelination following cytotoxic edema in the splenium of corpus callosum was strongly considered a pathogenesis of "clinically mild encephalitis/encephalopathy with a reversible splenial lesion" associated with hypoglycemia, and it could be generalized for the disease associated with the other causes. As cytotoxic edema could be the central pathology of the disease, the recently proposed term cytotoxic lesions of the corpus callosum may be applicable to this syndrome.

Three Types of Demyelination, Perivenous, Confluent, and Perineuronal Nets-Rich in a COVID-19 Patient With Meningoencephalomyelitis.

Neurologic symptoms are common in COVID-19, and a variety of neuropathological changes have been reported. One of the important neuropathological findings is demyelination. However, the underlying pathogenesis of demyelination remained poorly understood. We witnessed a case of COVID-19 with distinct types of demyelination in the cerebrum, medulla oblongata, and spinal canal, who died of sepsis. The postmortem examination showed the solitary massive demyelination in the medulla oblongata. The massive lesion was filled with components of perineuronal nets. In the spinal canal, confluent demyelination in bilateral lateral and dorsal funiculi was detected over the entire length from C1 to S5, which was maximum at the level of cervical spinal canal stenosis. Demyelination in the cerebrum was mainly perivenular, and augmented in the area of lacunar infarcts and dilated perivascular spaces. Considering the distribution patterns of the following three types of demyelination, the traces of viral spreading could be highlighted. Discontinuous perivenous demyelination in the cerebrum showed the result of hematogenous spreading. Longitudinal confluent demyelination of the spinal cord should be the picturesque of the trace of axonal spreading. The distribution of demyelination was possibly modified by the underlying diseases, diabetes mellitus, hypertension, and spinal canal stenosis.

SMARCB1- and vimentin-positive esophageal carcinoma with undifferentiated components, rhabdoid features, and a good prognosis: a case report.

BACKGROUND: Undifferentiated carcinoma of the esophagus with rhabdoid features is a very rare histologic finding that is occasionally associated with the loss of SWI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily B member 1 (SMARCB1); however, until now, few survey reports of this type of tumor have been published. In this study, we describe a case of esophageal carcinoma with undifferentiated components and rhabdoid features that was exclusively positive for vimentin and SMARCB1 in a patient with prolonged survival. CASE PRESENTATION: A 67-year-old man complained of a stomachache and loss of appetite persisting for 1 month. He was then admitted to the hospital. Diagnostic imaging studies revealed a transdiaphragmatic circular ulcerative tumor of the esophagogastric region. Biopsy specimens showed undifferentiated round cell carcinoma. The patient underwent lower esophageal resection and total gastrectomy with lymph node dissection. Microscopic analysis revealed that most of the primary tumor consisted of large undifferentiated round cells and scattered rhabdoid cells. The tumor invaded the muscular layer in the esophagus and the subserosal layer in the stomach, and metastasis was noted in only one lymph node. Immunohistochemical analysis revealed that the round and rhabdoid cells found in the primary tumor were diffusely positive for SMARCB1 and vimentin. The tumor displayed focal positivity for the anti-pan-cytokeratin antibody AE1/AE3. In the positive lymph node, round undifferentiated carcinoma cells were admixed with squamous carcinoma cells that were positive for cytokeratin 5/6 and 34ßE12. The MIB-1 index was 19.7% and 0.5% for the round cells from the primary tumor and epithelial cells from the metastatic lymph node lesion, respectively, and 70.1% for the round cells from the metastatic lymph node lesion. The patient has been alive for 10 years after surgery without tumor recurrence. CONCLUSIONS: We reported a rare case of esophageal carcinoma with undifferentiated components, rhabdoid features, and a good prognosis.

Activation of ERK/IER3/PP2A-B56γ-positive feedback loop in lung adenocarcinoma by allelic deletion of B56γ gene.

In order to investigate the involvement of the IER3/PP2A-B56γ/ERK-positive feedback loop, which leads to sustained phosphorylation/activation of ERK in carcinogenesis, we immunohistochemically examined the expression of IER3 and phosphorylated ERK in lung tumor tissues. IER3 was overexpressed in all cases of adenocarcinomas examined, but was not overexpressed in squamous cell carcinomas. Phosphorylated ERK (pERK) was also overexpressed in almost all adenocarcinomas. EGFR and RAS, whose gene product is located upstream of ERK, were sequenced. Activating mutation of EGFR, which is a possible cause of overexpression of IER3 and pERK, was found only in 5 adenocarcinomas (42%). No mutation of RAS was found. We further examined the sequences of all exons of B56γ gene (PPP2R5C) and IER3, but no mutation was found. Using a single nucleotide insertion in intron 1 of PPP2R5C, which was found in the process of sequencing, allelic deletion of PPP2R5C was examined. Eight cases were informative (67%), and the deletion was found in 4 of them (50%). Three cases having deletion of PPP2R5C did not have EGFR mutation. Finally, PPP2R5C deletion or EGFR mutation that could be responsible for IER3/pERK overexpression was found in at least 8 cases (67% or more). This is the first report of a high incidence of deletion of PPP2R5C in human carcinomas.

Myogenic cell response to muscle contraction with short electrical stimulation.

[Purpose] The present study aimed to determine the effects of short muscle strength exercise on hepatocyte growth factor expression and satellite cell activation. [Subjects] The study included 72 2-12-week-old male Sprague-Dawley rats. [Methods] The rat plantaris muscle was contracted with a 5-min electrical stimulation of the sciatic nerve, and then, the mRNA expressions of hepatocyte growth factor and myogenic regulatory factors in the plantaris muscle were determined, and the phosphorylation of the hepatocyte growth factor receptor (c-Met) was examined. [Results] The mRNA expressions of hepatocyte growth factor and myogenic regulatory factors increased after a short muscle contraction compared to that un-contraction. Immunofluorescence analysis showed the expression of hepatocyte growth factor protein and the possibility that downstream biological changes occurred in the hepatocyte growth factor-bound c-Met. [Conclusion] Our results demonstrated that activation of satellite cells induced hepatocyte growth factor expression during muscle contraction with a short 5-min electrical stimulation, which simulates short muscle strength exercise in physical therapy. The present study provides evidence for the use of short muscle strength exercise in physical therapy.

Cytologic features of nipple adenoma: a report of four cases of adenoma of the nipple.

We report four cases of adenoma of the nipple, a rare benign epithelial benign tumor occurring under the nipple and areola. Clinically, erosion findings of the nipple require discrimination from Paget's disease. In addition, a mass found in the nipple warrants discrimination from ductal carcinoma. Two cases underwent aspiration biopsy cytology and the other underwent tumor imprint cytology, respectively, revealing a large number of epithelial cell populations in the necrotic background material. These large cell clusters had a papillary or sheet structure and exhibited decreased cell cohesiveness at the cluster part. In addition, small clusters and solitary epithelial cells were also present. Furthermore, a two-cell pattern comprising both duct epithelial and myoepithelial cells was observed in the cell clusters. Two other cases underwent nipple brush cytology, revealing a few small papillary clusters with isolated epithelial cells in the hemorrhagic background. The clusters appeared as benign duct proliferative lesions such as papilloma, papillomatosis, and adenosis. An accurate diagnosis warrants the recognition of regular nuclei with bland chromatin and myoepithelial cells and the identification of the lesion location.

Inter-rater agreement of sputum cytology for lung cancer screening in Japan.

BACKGROUND: To compare lung cancer detection rate by sputum cytology, we need some assurance that the estimates do not vary widely if different observers evaluate the same specimens. The aim of this study was to determine inter-rater agreement of sputum cytology diagnoses. METHODS: Slides of sputum cytology from 150 subjects were selected from a pool of slides held by six of the laboratories that had participated in a population-based lung cancer screening program over the last ten years in Japan. The cytotechnologists in these laboratories had considerable experience with sputum cytology. Each case was re-evaluated six times. Cases that were diagnosed as the same category by all six laboratories were selected as consensus cases to serve as standardized sputum cytology cases. Thirty-seven cytotechnologists with various levels of experience in sputum cytology then re-evaluated these consensus cases. Inter-rater agreement was calculated by kappa statistics including Fleiss' kappa. RESULTS: All pairs of interlaboratory agreement for the 150 cases showed statistically significant kappa values, most pairs showing substantial agreement. Fleiss' kappa value across the six laboratories was 0.5. Fourteen cases were identified as the consensus cases, and the agreement among observers with less experience of sputum cytology showed significantly lower than the agreement among those with considerable experience (Fleiss' kappa value 0.27 vs. 0.45, P < 0.05). Moreover, cytotechnologists with less experience under-diagnosed the slides significantly more often than those with considerable experience. CONCLUSION: When the observers have considerable experience with sputum cytology, inter-observer agreement is good.

High-sensitivity cardiac troponin I detection for 2 types of drug-induced cardiotoxicity in patients with breast cancer.

BACKGROUND: Breast cancer treatment with trastuzumab, a monoclonal antibody that targets human epidermal growth factor receptor type 2 (HER2), has largely been successful in improving the prognosis of HER2-positive disease. However, a critical issue associated with trastuzumab treatment is its cardiotoxic adverse effects, including cardiac insufficiency. METHODS: We measured levels of cardiac troponin I, a marker of myocardial damage, with a highly sensitive method (hs-cTnI) using a fully automated chemiluminescent immunoassay system (ADVIA Centaur(®) XP) in breast cancer patients and examined the relationship between administration of trastuzumab and epirubicin and concentrations of hs-cTnI. RESULTS: The coefficient of variation for within-run repeatability was 1.34-5.93 %, using plasma pools and controls of 3 concentrations, and that for between-run reproducibility was 3.99-8.79 %, indicating high precision of the assay. In a dilutional linearity test with highly concentrated specimens, hs-cTnI values could be measured up to 50 ng/mL with linearity. No influence from coexisting substances was observed. The concentration of hs-cTnI was at or above the reference range (0.04 ng/mL) in 9 of 214 total breast cancer cases (4.2 %). The hs-cTnI concentration was at or above the reference range in 4 of 49 cases (8.2 %) that were administered trastuzumab, and in 5 of 165 cases (3.0 %) that were not. Trastuzumab did not cause elevation of hs-cTnI when not administered in combination with epirubicin. CONCLUSIONS: These results suggest that epirubicin and trastuzumab cause cardiotoxicity through different mechanisms. Epirubicin can cause myocardial necrosis, while trastuzumab can cause cardiomyopathy without myocardial necrosis.

Distinct allelic expression patterns of imprinted IGF2 in adenocarcinoma and squamous cell carcinoma of the lung.

The insulin-like growth factor 2 gene (IGF2) is an imprinting gene, which mediates cell growth and apoptosis. The loss of imprinting (LOI) of IGF2 has been associated with the development of cancer. In the present study, loss LOI of IGF2 in lung cancer was analyzed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in combination with DNA sequencing of samples collected by laser capture microdissection. The status of each sample was assigned as imprinting when PCR-RFLP revealed only one band or sequence with a single peak; otherwise, the case was classified as LOI. LOI was identified in eight out of 13 adenocarcinoma cases (62%), but was not detected in any of the nine squamous cell carcinoma cases (0%). These results suggest that IGF2 LOI is involved in the molecular pathogenesis of lung adenocarcinoma, but not squamous cell carcinoma, and that LOI may be detected through increased IGF2 expression levels.

Molecular characterization of various trichomonad species isolated from humans and related mammals in Indonesia.

Trichomonad species inhabit a variety of vertebrate hosts; however, their potential zoonotic transmission has not been clearly addressed, especially with regard to human infection. Twenty-one strains of trichomonads isolated from humans (5 isolates), pigs (6 isolates), rodents (6 isolates), a water buffalo (1 isolate), a cow (1 isolate), a goat (1 isolate), and a dog (1 isolate) were collected in Indonesia and molecularly characterized. The DNA sequences of the partial 18S small subunit ribosomal RNA (rRNA) gene or 5.8S rRNA gene locus with its flanking regions (internal transcribed spacer region, ITS1 and ITS2) were identified in various trichomonads; Simplicimonas sp., Hexamastix mitis, and Hypotrichomonas sp. from rodents, and Tetratrichomonas sp. and Trichomonas sp. from pigs. All of these species were not detected in humans, whereas Pentatrichomonas hominis was identified in humans, pigs, the dog, the water buffalo, the cow, and the goat. Even when using the high-resolution gene locus of the ITS regions, all P. hominis strains were genetically identical; thus zoonotic transmission between humans and these closely related mammals may be occurring in the area investigated. The detection of Simplicimonas sp. in rodents (Rattus exulans) and P. hominis in water buffalo in this study revealed newly recognized host adaptations and suggested the existence of remaining unrevealed ranges of hosts in the trichomonad species.

Analytical performance of newly developed multiplex human papillomavirus genotyping assay using Luminex xMAP™ technology (Mebgen™ HPV Kit).

Regional differences in human papillomavirus (HPV) genotypes and the presence of mixed HPV infections may affect adversely the efficacy of the HPV vaccine. Therefore, a simple and high-throughput HPV genotyping system is required. Recently, a novel HPV genotyping kit (the Mebgen™ HPV kit) was developed. This kit uses multiplex PCR and Luminex xMAP™ technology to detect 13 types of high-risk HPVs and an internal control in a 96-well format. In the present study, the analytical performance of the kit was examined using HPV plasmid DNA. All 13 types of HPVs were detected with a minimum detection sensitivity of 250 copies/test, and highly specific signals were observed. HPV 16 plasmid was detected in samples containing mixtures with other HPV-type plasmids in ratios ranging from 1:1 to 1:1000. No cross reactivity was observed with DNA from 27 types of other infectious microbes. A clinical evaluation was carried out using cervical samples from 356 patients with persistent abnormal smears diagnosed at mass public health screenings for cervical cancer. The samples were preserved in Tacas™ medium until analysis. HPV was detected in 162 (45.5%) samples including 110 (67.9%) with single infections and 52 (32.1%) with multiple infections. The type distribution of the 13 high-risk HPVs was as follows: 28.4% HPV 16, 11.7% HPV 18, 6.8% HPV 31, 3.1% HPV 33, 3.7% HPV 35, 9.3% HPV 39, 1.9% HPV 45, 8.6% HPV 51, 37.0% HPV 52, 9.3% HPV 56, 16.7% HPV 58, 3.7% HPV 59, and 1.9% HPV 68. To evaluate sample stability over time, changes in the detection of HPV DNA derived from HeLa and SiHa cells were measured in 3 types of liquid-based cytology media. HPV DNA was detected in Tacas and Thinprep™ samples after storage at 4°C or 30°C for 4 weeks and within 1 week of collection in Surepath™ samples. These results suggest that this newly developed HPV genotyping kit is suitable for use in both clinical applications and large-scale epidemiological studies.

Heat shock transcription factor HSF1 regulates the expression of the Huntingtin-interacting protein HYPK.

BACKGROUND: The Huntingtin-interacting protein HYPK possesses chaperone-like activity. We hypothesized that the expression of HYPK could be regulated by heat shock factor HSF1, a transcriptional regulator of chaperone genes. METHODS: HYPK expression in HeLa cells was assessed by RT-PCR and Western blot analysis. In vivo binding of HSF1 to the HYPK promoter was analyzed by chromatin immunoprecipitation assays. The requirement for HYPK in heat-shocked cells was examined using HYPK-knockdown cells. RESULTS: Levels of HYPK mRNA were slightly increased by heat treatment; however, the levels decreased in HSF1-silenced cells. The HYPK promoter was bound by HSF1 in a heat-inducible manner; however, its core promoter activity was notably suppressed upon heat shock. When cells were exposed to heat shock, silencing HYPK caused a decrease in cell viability. CONCLUSIONS: HYPK is a novel target gene of HSF1. HSF1 maintains HYPK expression in heat-shocked cells. GENERAL SIGNIFICANCE: The maintenance of HYPK expression by HSF1 is necessary for the survival of cells under thermal stress conditions.

Dynamic regulation of extracellular signal-regulated kinase (ERK) by protein phosphatase 2A regulatory subunit B56γ1 in nuclei induces cell migration.

Extracellular signal-regulated kinase (ERK) signalling plays a central role in various biological processes, including cell migration, but it remains unknown what factors directly regulate the strength and duration of ERK activation. We found that, among the B56 family of protein phosphatase 2A (PP2A) regulatory subunits, B56γ1 suppressed EGF-induced cell migration on collagen, bound to phosphorylated-ERK, and dephosphorylated ERK, whereas B56α1 and B56ß1 did not. B56γ1 was immunolocalized in nuclei. The IER3 protein was immediately highly expressed in response to costimulation of cells with EGF and collagen. Knockdown of IER3 inhibited cell migration and enhanced dephosphorylation of ERK. Analysis of the time course of PP2A-B56γ1 activity following the costimulation showed an immediate loss of phosphatase activity, followed by a rapid increase in activity, and this activity then remained at a stable level that was lower than the original level. Our results indicate that the strength and duration of the nuclear ERK activation signal that is initially induced by ERK kinase (MEK) are determined at least in part by modulation of the phosphatase activity of PP2A-B56γ1 through two independent pathways.

Hypolipidemic effect of Pleurotus eryngii extract in fat-loaded mice.

Pleurotus eryngii water extract (PEE), which showed the most significant inhibitory activity against pancreatic lipase in vitro among eight edible mushrooms, was investigated to determine the mechanism of its anti-lipase activity in vitro and its hypolipidemic effect in fat-loaded mice. The inhibitory effects of mushroom extracts on pancreatic lipase activity were examined using 4-methylumbelliferyl oleate (4-MUO) or trioleoylglycerol emulsified with lecithin, gum arabic or Triton X-100 as a substrate. For in vivo experiments, blood samples were taken after oral administration of corn oil and [(3)H]trioleoylglycerol with or without PEE to food-deprived mice. PEE inhibited hydrolysis of 4-MUO and trioleoylglycerol emulsified with lecithin or Triton X-100, but not that of trioleoylglycerol emulsified with gum arabic. PEE suppressed the elevations of plasma and chylomicron triacylglycerol levels after oral administration of corn oil, but had no effect on lipoprotein lipase activity. [(3)H]Trioleoylglycerol absorption was also decreased by administration of PEE. The results of in vitro studies suggest that PEE may prevent interactions between lipid emulsions and pancreatic lipase. The hypolipidemic effect of PEE in fat-loaded mice may be due to low absorption of fat caused by the inhibition of pancreatic lipase.

Occurrence of the Fimbria Gene hifA in clinical isolates of nonencapsulated Haemophilus influenzae.

The adherence of Haemophilus influenzae to epithelial cells plays a crucial role in infections. However, little is known about the occurrence of fimbriae. In this study, we examined the distribution of the fimbria gene (hifA) by PCR among 167 H. influenzae strains isolated from patients with respiratory infections. Almost all (163; 98%) of the isolates were nonencapsulated strains. The carriage rate of hifA by the nonencapsulated strains was 18.4%. Electron microscopy showed that fimbriae were abundantly present on the cell surface of hifA-positive strains tested. Only four (2.4%) isolates were encapsulated, all of which were type b and did not possess hifA. The present work suggests that fimbriae may play a considerable role as adhesins in nonencapsulated H. influenzae strains.

Loss of imprinting in IGF2 in colorectal carcinoma assessed by microdissection.

To ascertain the implications of loss of imprinting (LOI) of the insulin-like growth factor II gene (IGF2) for carcinogenesis, the precise frequency of LOI in colorectal carcinoma was examined using a laser capture microdissection method, and compared to the matched normal colorectal mucosa. LOI was examined by PCR-restriction fragment length polymorphism in combination with direct sequencing. The status was assigned as imprinting when PCR-RFLP showed only one band or sequence with a single peak, otherwise cases were classified as LOI. LOI was found in 13 of 24 informative cases of carcinoma (54%), which was higher than the ratios reported previously. LOI was also found in the normal colorectal mucosae in 14 cases (58%). The LOIs in carcinomas and in the normal mucosae were closely correlated: 10 of 13 LOI-positive carcinomas showed LOI in the matched normal mucosae. These results suggest that LOI of IGF2 in colorectal carcinoma and LOI in the background mucosa play important roles in carcinogenesis.

Adhesiveness of beta5 integrin variant lacking FNK767-769 is similar to that of the prototype containing FNKFNK764-769.

Little is known about the functions of two different beta5 integrins: repeated-FNK (FNKFNK764-769) and single-FNK (FNK764-766) amino acid sequences in the cytoplasmic domain. We examined whether they occurred as germ line mutations or somatic mutations associated with neoplastic transformation, and whether there were functional alterations. Out of six cultured cell lines, only KATO-III cells had the single-FNK beta5 sequence. The single-FNK beta5 was found in 9 out of 79 patients with colon carcinoma, but no somatic mutations were detected in cancerous tissues. CHO cells were transformed with expression vectors containing single-FNK or repeated-FNK beta5 cDNA, which were derived from KATO-III cells. CHO cells transfected with single-FNK and repeated-FNK showed similar adhesiveness to, and proliferative activity on, vitronectin substrates.

Berry splenic artery aneurysm rupture in association with segmental arterial mediolysis and portal hypertension.

A rare case of berry splenic artery aneurysm (SAA) rupture associated with segmental arterial mediolysis (SAM) and portal hypertension is reported. A 66-year-old woman, diagnosed as having liver cirrhosis and portal hypertension 6 years earlier, suddenly developed a lancinating pain in the upper abdomen and lost consciousness. She recovered consciousness while being transferred to hospital by ambulance. During the investigations, her level of consciousness suddenly deteriorated. Ultrasonography showed a massive intraperitoneal hemorrhage, and she died 5(1/2) h after admission. On gross examination at autopsy it was not possible to find the rupture point of the vessel because the pancreas was embedded in a massive hematoma. However, careful dissection of the pancreatic tail after fixation revealed a berry aneurysm measuring 0.8 cm in diameter in a branch adjacent to the bifurcation in the distal third of the main splenic artery. Microscopic examination detected a rupture of the aneurysm. The histology of the arterial wall proximal to the aneurysm showed typical SAM. In general, berry SAA caused by SAM is rare and unlikely to rupture. The SAA in the present case likely occurred and ruptured due to the combination of SAM and portal hypertension.

Protein phosphatase 2A regulatory subunit Bbeta promotes MAP kinase-mediated migration of A431 cells.

BACKGROUND/AIMS: Phosphatases are involved in regulation of MAP kinase (MAPK). A431 cells migrate on collagen after EGF stimulation using MAPK. To clarify the involvement of PP2A in this MAPK-dependent migration, the expression of an isoform of the B regulatory subunit was inhibited. METHODS: An antisense sequence corresponding to Bbeta cDNA was transfected into A431 cells. Their migratory activity on collagen was examined using Transwell, and MAPK phosphorylation and phosphatase activity were measured, and the results were compared with those obtained with mock-transfected cells. RESULTS: Antisense-transfected cells showed less Bbeta protein and phosphatase activity than mock-transfected controls. Migration of antisense-transfected cells showed a low response to EGF. The response of MAPK phosphorylation of antisense-transfected cells to EGF stimulation and adhesion to collagen in the presence or absence of EGF were markedly decreased. Phosphatase activity of PP2A-Bbeta also did not respond to EGF, collagen or EGF plus collagen, and remained at low levels. CONCLUSION: These results suggested that PP2A-Bbeta promotes cell migration through the MAPK cascade.

Overexpression of E2F1 associated with LOH at RB locus and hyperphosphorylation of RB in non-small cell lung carcinoma.

PURPOSE: E2F1 plays a critical role in cell proliferation, and its function is controlled by the retinoblastoma (RB) protein. We examined the expression of E2F1 and the aberration of RB gene and protein to elucidate what factors contribute to the overexpression of E2F1 in non-small cell lung carcinomas. METHODS: The expression level of E2F1 in tissues of non-small cell lung carcinomas was measured by means of quantitative reverse transcription-polymerase chain reaction and immunohistochemistry. For RB, we examined loss of heterozygosity (LOH) by PCR-restriction fragment length polymorphism and a variable number of tandem repeats, and protein expression by immunohistochemistry. RESULTS: Fifteen cases of carcinoma (46%) showed high transcription levels of E2F1 gene. Immunohistochemically, almost all (14 of 15) cases overexpressing E2F1 mRNA were positive for E2F1 protein. LOH at the RB locus was found in 13 of 30 informative cases. In 13 cases with LOH, ten showed overexpression of E2F1 mRNA and protein. Immunohistochemical positivity for phosphorylated RB protein was also closely correlated with overexpression of E2F1. CONCLUSIONS: Our results suggest that overexpression of E2F1, induced both by LOH at the RB locus and anomalous phosphorylation of the RB protein, is involved in the development of non-small cell lung carcinoma.