Search

Here, we report two cases showing tumor-like white matter lesions; one case was diagnosed as having inflammatory disease, and the other was diagnosed as having astrocytoma. Their outcomes were completely distinct despite similar pathology. Prior to biopsy, perfusion computed tomography (CT) and magnetic resonance imaging (MRI) were conducted. The two mass-forming lesions were distinct in edema level and vascularity patterns on CT and MRI. However, pathological examination of brain biopsy specimens revealed commonalities, including (1) proliferation of glial cells, (2) perivascular lymphocytic infiltration, and (3) appearance of numerous macrophages. Although atypical astrocytes proliferated in both cases, nuclear atypia was more distinct in case 2 than in case 1. The immunohistochemical results were the same for both cases: isocitrate dehydrogenase 1 (IDH1) R132H mutation was negative, and alpha thalassaemia mental retardation X-linked (ATRX) was retained. Faint immunoreactivity for p53 was observed in a few glial cells, and Ki-67 immunoreactive cells were markedly reduced in numbers (< 1%). Inflammatory reactions were evident in both cases: T cells dominantly infiltrated over B cells in the perivascular area in case 1, whereas both T and B cells infiltrated in case 2. Molecular analysis revealed wild-type IDH1 and IDH2 in both cases. However, a telomerase reverse transcriptase (TERT) sequence mutation was detected in case 2 but not in case 1. Eventually, case 1 was diagnosed as having inflammatory lesions, whereas case 2 was diagnosed as having diffuse astrocytoma associated with inflammatory reactions. The prognosis was favorable for case 1, whereas case 2 died 10 months following biopsy. These data indicated the diagnostic value of molecular analysis, for example, a TERT mutation, in association with the radiological findings. Although in case 2, histopathological evidence did not suggest high-grade glioma, the case met the new diagnostic criteria: "diffuse astrocytic glioma, IDH wild-type, with molecular features of glioblastoma, World Health Organization (WHO) grade IV," according to cIMPACT-NOW, update 3. Thus, interdisciplinary approaches are essential for accurate diagnosis of newly categorized white matter diseases.

The case of 70-year-old man with mantle cell lymphoma (MCL) carrying t(11;14) translocation that relapsed as nodal lymphoma combining MCL and classic Hodgkin lymphoma (cHL) 9 years after autologous peripheral blood stem cell transplant (auto-PBSCT) is reported. Lymph nodes contained two separate areas of MCL and cHL-like components. Hodgkin and Reed-Sternberg (HRS)-like cells were accompanied by a prominent histiocyte background. HRS-like cells were CD5- , CD15+ , CD20- , CD30+ , PAX5+ , Bob.1- , Oct2- and EBER+ . The MCL component expressed cyclin D1 and SOX11, whereas cyclin D1 and SOX11 expressions were reduced and lost, respectively, in HRS-like cells. Polymerase chain reaction results showed a single clonal rearrangement of the IGH gene in MCL and cHL-like components. CCND1 break apart fluorescence in situ hybridization showed split signals in both MCL and HRS-like cells, suggesting that MCL and cHL-like components were clonally related. Acquisition of p53 expression and Epstein-Barr virus (EBV)-positivity was seen in HRS-like cells. The patient died of disease progression with elevated hepatobiliary enzymes. The autopsy showed both MCL and cHL-like components around the bile ducts, splenic white pulp and bone marrow. The two components were phenotypically distinct, but genetically related, suggesting that transformation of MCL to HRS-like cells during the course of MCL in association with EBV infection.

The patient was a 74-year-old woman with rheumatoid arthritis who developed ataxia. MRI revealed T2-hyperintense lesions predominantly in the left middle cerebellar peduncle. Punctate or linear Gd enhancement was also observed on T1-weighted images. A brain biopsy was conducted and the pathology revealed a mild demyelinated lesion. Polymerase chain reaction (PCR) of biopsied brain tissues revealed the presence of JC virus (JCV) DNA, but JCV-infected oligodendroglia-like cells were not apparent on immunohistochemistry. Sensitive in-situ hybridization, however, detected three JCV-positive cells and the infiltration of CD4+ and CD8+ T cells and plasma cells was also observed. Immunosuppressants were tapered off and mirtazapine and mefloquine administered, resulting in a favorable outcome.

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disorder caused by opportunistic infection of JC polyomavirus (JCV). Today, increased attention has been focused on PML development in multiple sclerosis (MS) patients under disease-modifying therapies (DMT). Although in the acquired immunodeficiency syndrome (AIDS) era, PML was thought to be a rapidly progressive disease with poor prognosis, drug-associated PML is relatively slow in progress, and a favorable outcome may be expected with early diagnosis. However, early PML diagnosis on magnetic resonance imaging (MRI) is frequently difficult, and JCV DNA copy number in cerebrospinal fluid (CSF) is usually low. To facilitate early PML diagnosis on MRI, the pre-mortem images were compared with neuropathology of the post-mortem brain, and underlying pathology corresponding to the MRI findings was evaluated. As a result, PML lesions of the autopsied brain were divided into three parts, based on the disease extension patterns: (A) Progressive white matter lesion in the right frontoparietal lobe including the precentral gyrus. Huge demyelinated lesions were formed with fusions of numerous small lesions. (B) Central lesion including deep gray matters, such as the putamen and thalamus. The left thalamic lesion was contiguous with the pontine tegmentum. (C) Infratentorial lesion of brainstem and cerebellum. Demyelination in the pontine basilar region and in cerebellar white matter was contiguous via middle cerebellar peduncles (MCPs). In addition, (D) satellite lesions were scattered all over the brain. These observations indicate that PML lesions likely evolve with three steps in a tract-dependent manner: (1) initiation; (2) extension/expansion of demyelinating lesions; and (3) fusion. Understanding of the PML disease evolution patterns would enable confident early diagnosis on MRI, which is essential for favorable prognosis with good functional outcome.

Background Primary central nervous system lymphoma (PCNSL), a relatively rare brain tumor, bears a dire prognosis. On occasion, rapid progression of the tumor makes immediate diagnosis and initiation of therapy imperative. To achieve swift diagnosis, we adopt flow cytometry (FCM) in addition to conventional histopathology. The aim of this study is to reveal utility and drawbacks of FCM diagnosis for PCNSL. Methods Patients with suspected PCNSL on neuroradiological findings and received both FCM and histological diagnosis between August 2015 and April 2020 were retrospectively enrolled into the study. Tumor samples were collected by craniotomy with either of endoscope or microscope. The patients’ electronic medical records were investigated, and histological findings, results of FCM, and other clinical data were evaluated. Results Twenty seven patients met the eligibility criteria. Twenty three patients (11 males and 12 females) were diagnosed with PCNSL by histological confirmation, and 22 cases were B-cell type lymphoma and 1 was T-cell type. Median age at diagnosis was 65. FCM analysis showed lymphoma pattern in 20 cases, but in the other 3 lymphoma cases (FCM discordant: FCM-D) and 4 non-lymphomatous tumor cases, FCM results did not show lymphoma pattern (sensitivity: 86.4%, specificity: 100%). Analysis of FCM-D cases showed infiltration of T lymphocytes or astrocytes into the tumor tissue, indicating tumor microenvironmental reaction, were observed, and it is assumed that those reactions deceived FCM diagnosis. Conclusions Despite some disadvantages, diagnosis of PCNSL by FCM is rapid and reliable.

A 70-year-old woman with a human T-cell leukemia virus type 1 infection without any focal neurological symptoms showed age-related atherosclerotic changes in the white matter without any suspicious signal changes suggestive of progressive multifocal leukoencephalopathy (PML) based on the findings of MRI. Viral polymerase chain reaction (PCR) revealed 6,700 copies/mL of the JC virus genome in the cerebrospinal fluid (CSF). An immuno-pathological examination of the autopsied brain revealed JC virus capsid proteins, and in situ hybridization confirmed a JC virus infection, indicating that an active infection begins at the radiologically indistinguishable phase of PML. An early JC virus infection is probably associated with small, scattered demyelinating lesions around the cortico-medullary area of the cortex.

In the present study, we analyzed the inflammatory profiles of brain tissues obtained from patients with progressive multifocal leukoencephalopathy (PML) due to John Cunningham (JC) virus infection to identify potential prognostic factors. The study included seven patients (two men, five women) who had been pathologically diagnosed with PML, and all of whom were HIV negative. Fixed brain samples were analyzed via hematoxylin and eosin (HE) staining and Kluver–Barrera (KB) staining. We then performed immunohistochemistry (IHC) specific to JC virus capsid proteins (VP1 and VP2/3) and lymphocyte surface markers (CD4, CD8, CD138, and PD-1). The mean age at onset was 53.4, while the mean duration until biopsy/autopsy was 4.7 months. Four patients were included in the good prognosis (GP) group, while three were included in the poor prognosis (PP) group. Pathological analysis revealed a significantly larger number of CD4-positive T-cell infiltrations (P = .029) in the GP group, along with a preserved CD4:CD8 ratio. Larger numbers of CD138-positive plasma cells were also observed in the GP group (P = .029) than in the PP group. Linear regression analyses revealed a significant association between the numbers of CD138-positive plasma cells and PD-1-positive cells (R2 = 0.80). Viral loads in the cerebrospinal fluid, a controlled inflammatory response mediated by CD4- and CD8-positive T cells, and plasma cells are associated with PML prognosis. Our findings further indicate that regulatory plasma cells may regulate inflammatory T-cell activity via a PD-1/PD-L1 immuno-checkpoint pathway, thereby protecting the uninfected brain from excessive immune-mediated damage during an active JC virus infection.

A 37-year-old woman with systemic lupus erythematosus presented with gait disturbance and cognitive dysfunction. Brain magnetic resonance imaging (MRI) revealed small, punctate, T2-/fluid-attenuated inversion recovery-hyperintense and T1-hypointense lesions without gadolinium enhancement, which is atypical for progressive multifocal leukoencephalopathy (PML). On a pathological examination of biopsied brain tissues, JC virus-infected cells were hardly detected via immunohistochemistry but were certainly detected via in situ hybridization, conclusively verifying the PML diagnosis. After tapering off the immunosuppressant and mefloquine administration, the MRI findings revealed gradual improvement, and she has been stable for over 18 months. A punctate MRI pattern is not specific to natalizumab-associated PML but may be a ubiquitous early sign useful for the early diagnosis of PML.

BACKGROUND: Chemotherapy with high-dose methotrexate (HD-MTX) followed by whole brain radiotherapy (WBRT) is a conventional approach to treat primary central nervous system lymphomas (PCNSL), but some tumors relapse early leading to unfavorable outcome. Several biomarkers have been identified as prognostic factors in PCNSL, however, the correlation of both clinical factors including those related to MTX metabolism and B-cell differentiation and oncogenic biomarkers with response to and outcome by therapy is yet unclear. METHODS: We investigated 32 immunocompetent patients (19 males, 13 females) with PCNSL (all diffuse large B-cell type) treated with HD-MTX based therapy with or without WBRT since 2000 in our institution. Paraffin-embedded formalin-fixed tumor tissue sections were stained immunohistochemically with antibodies against following factors: B-cell differentiation markers (CD10, Bcl-6, Mum-1, CD138); MTX metabolism-related (MRP family, LRP, DHFR); cell cycle-related (p27KIP1, MIB-1); drug resistance-related (MGMT, MLH1, MSH2, MSH6, PMS2); and oncogenes (Myc, Bcl-2). Correlation between positivity of these factors and clinical outcomes were evaluated using logrank test and cox regression analysis. RESULTS: Among these factors, complete response to HD-MTX was significantly associated with longer progression-free survival (PFS)(P = 0.0012), while Bcl-6 expression as well as histological subtype (non-germinal center B-cell, non-GCB) was closely correlated with shorter PFS. Age (>60) (P = 0.006) and MSH2 expression (P = 0.017) were found to be better predictor for overall survival (OS), but in multivariate analysis, they were no longer significant. Other factors involved in MTX metabolism, DNA repair enzymes, and oncogenes did not affect outcome. CONCLUSIONS: Non-GCB subtype and Bcl-6 expression may be associated with worse outcome in patients with PCNSL treated with HD-MTX, while MTX-metabolism related factors did not influence prognosis. Further investigation is needed to assess Bcl-6 as a potential prognostic factor in PCNSL. SECONDARY CATEGORY: Clinical Neuro-Oncology.

The study aim to demonstrate the therapeutic tissue depth of photodynamic therapy (PDT) using the photosensitizer talaporfin sodium and semiconductor laser for malignant glioma from an autopsy finding. Three patients diagnosed with glioblastoma by pre-operative imaging (1 newly diagnosed patient and 2 patients with recurrence) were treated with intra-operative additional PDT and adjuvant therapy such as post-operative radiotherapy or chemotherapy. All three patients died of brain stem dysfunction owing to cerebrospinal fluid dissemination or direct invasion of the tumor cells from 13, 18, or 20 months after PDT. Antemortem magnetic resonance images demonstrated no tumor recurrence in the site of PDT, and autopsy was performed for the pathological analysis. Macroscopic observation demonstrated no tumor recurrence in two patients, but one patient demonstrated tumor recurrence in the therapeutic depth of PDT. Microscopic analysis demonstrated histopathological changes reaching depths of 9, 11, and 18 mm (mean: 12.7 mm) from the surface of the cavity of tumor resection, suggesting the therapeutic tissue depth of PDT to be in this range. This region demonstrated glial scarring with infiltration of T lymphocytes and macrophages, with slight degeneration of small vessel walls. However, viable tumor tissues were observed beyond or around the therapeutic tissue depth of PDT in two patients. PDT for glioblastoma prevented early local recurrence, which suggests the possibility that activation of the immune mechanisms was involved. The therapeutic tissue depth was suggested to be 9–18 mm from the surface of the cavity of tumor resection; however, the viable tumor tissues were demonstrated beyond this therapeutic range.

We report four cases of high-grade astrocytoma with a BRAF V600E mutation, ATRX inactivation, and CDKN2A/B homozygous deletion. Children to young adults aged 3–46 presented with a well demarcated contrast-enhancing mass in the supratentorial area. Pathological examination revealed packed growth of short spindle to round polygonal cells including some pleomorphic cells. The tumors had less ability to infiltrate into the adjacent brain parenchyma and presented a circumscribed growth pattern. Mitosis was readily found, accompanied by focal necrosis and/or microvascular proliferation. Tumors were histologically similar in part to pleomorphic xanthoastrocytoma (PXA) or anaplastic PXA, but did not fit criteria for either neoplasm. A BRAF V600E mutation and homozygous deletion of CDKN2A/B were observed, which is similar to the genetic features of PXA or epithelioid glioblastoma, but the additional loss of ATRX nuclear immunoreactivity and absence of TERT promoter mutation were unusual findings, indicating a novel genetic profile. Despite their malignant histological features, all patients had a favorable clinical course and remained alive for 6 months to 28 years under standard medical treatment for malignant glioma. In summary, high grade astrocytomas with BRAF V600E, ATRX, and CDKN2A/B alternations had unique clinicopathological features and may be a novel subset of high grade glioma.

One-third of lung malignancies demonstrate a proneural/neuroendocrine phenotype or type of differentiation. However, it has not been clearly elucidated how proneural/neuroendocrine differentiation is controlled in lung cancers. We recently demonstrated that the POU3F2 gene plays a significant role in proneural/neuroendocrine differentiation of lung cancers. Because class III POU genes (POU3F1, POU3F2, POU3F3, and POU3F4) and class IV POU genes (POU4F1, POU4F2, and POU4F3) share similar properties in neural development, we analyzed the association between class III/IV POU genes and a proneural/neuroendocrine phenotype in lung cancers using seven small cell lung cancer (SCLC) cell lines and twelve non-SCLC (NSCLC) cell lines. Class III/IV POU gene expression was generally restricted to SCLC cells. However, the forced expression of class III/IV POU genes in the NSCLC cell lines induced the expression of neuroendocrine-specific markers (neural call adhesion molecule 1, synaptophysin, and chromogranin A) and proneural transcription factors (achaete-scute homolog-like 1, NeuroD1, and thyroid transcription factor 1) in various degrees. Furthermore, each class III/IV POU gene induced other class III/IV POU genes, suggesting the mutual induction of class III/IV POU genes. These findings suggest that the expression of class III/IV POU genes is important for the proneural/neuroendocrine differentiation of lung cancer cells.

In lung tumors, the association between carcinoids and high-grade neuroendocrine tumors (HGNETs) is controversial. To understand the phenotypic similarities/differences between lung carcinoids and HGNETs, we comparatively investigated the expression of three kinds of developing neural transcription factors (DNTFs: BRN2, TTF1 and ASCL1) and multiple endocrine neoplasia type 1 (MEN1) as well as RB1 and P53 using 18 carcinoids and 16 HGNETs. The DNTFs were expressed in 10 of the 18 carcinoids and in all the HGNETs, while normal neuroendocrine cells, which are considered the major cell origin of lung carcinoids and small cell carcinomas, did not express DNTFs. Both the DNTF(-) and DNTF(+) carcinoids contained typical and atypical carcinoids. All the DNTF(-) carcinoids examined were formed in the bronchial wall. All the MEN1(-) carcinoids examined were classified into the DNTF(-) carcinoids, while all the HGNETs expressed MEN1. This finding suggests that DNTF(-) MEN1(-) carcinoids are unlikely to be precursors of HGNETs. Although the status of RB1 and P53 between carcinoids and HGNETs were apparently different, the DNTF(+) carcinoids of two male patients and one female patient revealed morphologies resembling HGNET cells and relatively high Ki67 indices. Further investigation of DNTF expression in carcinoids might provide important clues to understand the association between carcinoids and HGNETs.

Lobular carcinoma in situ (LCIS) clinically constitutes a risk factor for the subsequent development of either invasive lobular carcinoma (ILC) or invasive ductal carcinoma (IDC). In order to approach the possibility of this common precursor of both ILC and IDC, we investigated combined lobular and ductal carcinomas. Thirty-two cases of lobular carcinoma were picked up out of 773 cases of operated breast carcinomas. The histopathological detailed re-examination using immunostain of E-cadherin and β-catenin revealed a rather high frequency of combined lobular carcinomas than previous reports. Clinicopathologically, combined lobular carcinomas were younger and smaller than pure lobular carcinomas, and the cytological atypia was relatively low. These results suggested that combined lobular carcinomas could be detected in the earlier stage of breast cancer. Furthermore, the lobular and ductal components of combined carcinomas coexisted in the neighborhood and were distributed contiguously. The immunohistochemical phenotypes of both components were accorded in most combined cases. A genetic analysis using methylation-specific PCR on the HUMARA gene demonstrated that the same allele was inactivated in both lobular and ductal components in all detectable cases of combined carcinoma. Therefore, it is reasonable to assume that both lobular and ductal components of combined carcinomas are clonal and derived from the LCIS as the common precursor lesion, which may contradict the conventional concept that the lobular and ductal carcinomas arise from distinct differentiation pathways.

A 53-year-old man was admitted for sub-acute progressive dementia and Gerstmann syndrome. MRI demonstrated lesions in the white matter involving the left parietal lobe, accompanied by speckled or faint linear peripheral enhancement. Brain biopsy revealed JC virus infection in oligodendrocytes and balanced infiltration of CD8+ and CD4+ T lymphocytes. We diagnosed progressive multifocal leukoencephalopathy (PML) with controlled inflammation. The finding of CD4/CD8 T cells in the infected PML brain suggested therapeutically valuable immune system involvement, which we decided to preserve by withholding corticosteroids. We treated the patient with risperidone, cytarabine and mefloquine to suppress virus replication, but not with the corticosteroid that is conventionally used in inflammatory PML cases. The patient was discharged three months after admission, and one year later, his score on the Mini-Mental State Examination had recovered to 26/30, from 5/30 on admission.

Progressive multifocal leukoencephalopathy (PML) is caused by reactivation of latently infected JCV when hosts' immune system is impaired by HIV infection, hematologic diseases, collagen diseases, immunemodulatory therapy and so on. PML was rare but HIV infection and Natalizumab have made it much more common while the prognosis is much better than other PML. PML patients present with various signs and symptoms including hemiparesis, dementia, aphasia, visual disturbance, cranial nerve paresis, cerebellar signs and bladder bowel disturbance. Brain MRI reveals characteristic demyelinating lesions in the CNS white matter and CSF mild increase of protein with or without mild mononuclear pleocytosis. Detection of JCV genome from CSF is crucial for the clinical diagnosis of PML. PML was once thought to be fatal but some HIV infected PML patients showed halting progression or even recovery after introduction of HAART. In addition, anti-malarial drug mefloquine was found to be effective. Recovery of immunity may provoke some inflammatory responses known as immune reconstruction inflammatory syndrome (IRIS) which requires high dose corticosteroid. In Japan, we are providing free test of CSF-JCV genome and organized a unique system for surveillance and clinical research of PML. Using this system we hope to improve diagnosis and therapy of PML in Japan.

Primary central nervous system lymphoma (PCNSL) is a rare malignancy confined to the central nervous system (CNS), and majority of PCNSL is pathologically classified as diffuse large B-cell lymphoma (DLBCL). We have now performed whole-exome sequencing for 41 tumor tissues of DLBCL-type PCNSL and paired normal specimens and also RNA-sequencing for 30 tumors, revealing a very high frequency of nonsynonymous somatic mutations in PIM1 (100 %), BTG2 (92.7 %), and MYD88 (85.4 %). Many genes in the NF-κB pathway are concurrently mutated within the same tumors. Further, focal deletion or somatic mutations in the HLA genes are associated with poor prognosis. Copy number amplification and overexpression of genes at chromosome 7q35 were both found to predict short progression-free survival as well. Oncogenic mutations in GRB2 were also detected, the effects of which in cultured cells were attenuated by inhibitors of the downstream kinases MAP2K1 and MAP2K2. Individuals with tumors positive for MYD88 mutations also harbored the same mutations at a low frequency in peripheral blood mononuclear cells, suggesting that MYD88 mutation-positive precancerous cells originate outside of the CNS and develop into lymphoma after additional genetic hits that confer adaptation to the CNS environment.

Objective:To clarify the clinical, neuropathologic, and virologic characteristics of progressive multifocal leukoencephalopathy (PML) and its immune reconstitution inflammatory syndrome (IRIS) in a patient with fingolimod-treated MS.Methods:A case study.Results:A 34-year-old patient with MS using fingolimod for 4 years had a gradual progression of right hemiparesis and aphasia with a new subcortical white matter lesion in the precentral gyrus by initial MRI. Blood tests were normal, except for lymphopenia (160 cells/μL). One month after the cessation of fingolimod, brain MRI depicted a diffusely exacerbated hyperintensity on fluid-attenuated inversion recovery and diffusion-weighed imaging in the white matter with punctate gadolinium enhancement, suggesting PML-IRIS. A very low level of JC virus (JCV)-DNA (15 copies/mL) was detected in the CSF as judged by quantitative PCR. Brain tissues were biopsied from the left frontal lesion, which showed some small demyelinated foci with predominant loss of myelin-associated glycoprotein with infiltrations of lymphocytes and macrophages, but clear viral inclusion was not observed with hematoxylin-eosin staining. JCV-DNA was uniquely detectable in an active inflammatory demyelinating lesion by in situ hybridization, possibly suggesting an early phase of PML. DNA extracted from the brain sample was positive for JCV-DNA (151 copies/cell). It took 3 months to normalize the blood lymphocyte count. The patient was treated with 1 g of IV methylprednisolone for 3 days and a weekly oral dose (375 mg) of mefloquine, and her symptoms gradually improved.Conclusion:Low CSF JCV-DNA and unfound viral inclusions initially made her diagnosis difficult. The clinical course of fingolimod-associated PML may be associated with mild immune reconstitution.

Thyroid transcription factor 1 (TTF1) plays crucial roles in thyroid, lung, and developing brain morphogenesis. Because TTF1-expressing neoplasms are generated from organs and tissues that normally express TTF1, such as the thyroid follicular epithelium and peripheral lung airway epithelium, TTF1 is widely used as a cell lineage-specific and diagnostic marker for thyroid carcinomas and for lung adenocarcinomas with terminal respiratory unit (TRU) differentiation. However, among lung neuroendocrine tumors, small-cell carcinomas (small-cell lung cancers (SCLCs)), most of which are generated from the central airway, also frequently express TTF1 at high levels. To clarify how SCLCs express TTF1, we investigated the molecular mechanisms of its expression using cultivated lung cancer cells and focusing upon neural cell-specific transcription factors. Both SCLC cells and lung adenocarcinoma cells predominantly expressed isoform 2 of TTF1, and TTF1 promoter assays in SCLC cells revealed that the crucial region for activation of the promoter, which is adjacent to the transcription start site of TTF1 isoform 2, has potent FOX-, LHX-, and BRN2-binding sites. Transfection experiments using expression vectors for FOXA1, FOXA2, LHX2, LHX6, and BRN2 showed that BRN2 substantially upregulated TTF1 expression, whereas FOXA1/2 weakly upregulated TTF1 expression. BRN2 and FOXA1/2 binding to the TTF1 promoter was confirmed through chromatin immunoprecipitation experiments, and TTF1 expression in SCLC cells was considerably downregulated after BRN2 knockdown. Furthermore, the TTF1 promoter in SCLC cells was scarcely methylated, and immunohistochemical examinations using a series of primary lung tumors indicated that TTF1 and BRN2 were coexpressed only in SCLC cells. These findings suggest that TTF1 expression in SCLC is a cell lineage-specific phenomenon that involves the developing neural cell-specific homeoprotein BRN2.

Progressive multifocal leukoencephalopathy is a fatal viral-induced demyelinating disease that was once rare but has become more prevalent today. Over the past decades, much has been learned about the disease from molecular study of the etiological agent of the disease, JC virus. Recently, promyelocytic leukemia nuclear bodies (PML-NBs), punctuate structures for important nuclear functions in eukaryotic cells, were identified as an intranuclear target of JC virus infection. Neuropathologically, JC virus-infected glial cells display diffuse amphophilic viral inclusions by hematoxylin–eosin staining (full inclusions), a diagnostic hallmark of this disease. Recent results using immunohistochemistry, however, revealed the presence of punctate viral inclusions preferentially located along the inner nuclear periphery (dot-shaped inclusions). Dot-shaped inclusions reflect the accumulation of viral progeny at PML-NBs, which may be disrupted after viral replication. Structural changes to PML-NBs have been reported for a variety of human diseases, including cancers and neurodegenerative disorders. Thus, PML-NBs may provide clues to the further pathogenesis of JC virus-induced demyelinating disease. Here, we review what we have learned since the disease entity establishment, including a look at recent progress in understanding the relationship between JC virus, etiology and PML-NBs.