Establishment of keratinocyte cell lines from human hair follicles.

The advent of organotypic skin models advanced the understanding of complex mechanisms of keratinocyte differentiation. However, these models are limited by both availability of primary keratinocytes and donor variability. Keratinocytes derived from cultured hair follicles and interfollicular epidermis were immortalized by ectopic expression of SV40 and hTERT. The generated keratinocyte cell lines differentiated into stratified epidermis with well-defined stratum granulosum and stratum corneum in organotypic human skin models. They behaved comparable to primary keratinocytes regarding the expression of differentiation-associated proteins, cell junction components and proteins associated with cornification and formed a barrier against biotin diffusion. Mechanistically, we found that SV40 large T-antigen expression, accompanied by a strong p53 accumulation, was only detectable in the basal layer of the in vitro reconstructed epidermis. Inhibition of DNA-methylation resulted in expression of SV40 large T-antigen also in the suprabasal epidermal layers and led to incomplete differentiation of keratinocyte cell lines. Our study demonstrates the generation of keratinocyte cell lines which are able to fully differentiate in an organotypic skin model. Since hair follicles, as source for keratinocytes, can be obtained by minimally invasive procedures, our approach enables the generation of cell lines also from individuals not available for skin biopsies.

Identification and Characterization of Metastatic Factors by Gene Transfer into the Novel RIP-Tag; RIP-tva Murine Model.

Metastatic cancer accounts for 90% of deaths in patients with solid tumors. There is an urgent need to better understand the drivers of cancer metastasis and to identify novel therapeutic targets. To investigate molecular events that drive the progression from primary cancer to metastasis, we have developed a bitransgenic mouse model, RIP-Tag; RIP-tva. In this mouse model, the rat insulin promoter (RIP) drives the expression of the SV40 T antigen (Tag) and the receptor for subgroup A avian leukosis virus (tva) in pancreatic ß cells. The mice develop pancreatic neuroendocrine tumors with 100% penetrance through well-defined stages that are similar to human tumorigenesis, with stages including hyperplasia, angiogenesis, adenoma, and invasive carcinoma. Because RIP-Tag; RIP-tva mice do not develop metastatic disease, genetic alterations that promote metastasis can be identified easily. Somatic gene transfer into tva-expressing, proliferating pancreatic ß premalignant lesions is achieved through intracardiac injection of avian retroviruses harboring the desired genetic alteration. A titer of >1 x 108 infectious units per ml is considered appropriate for in vivo infection. In addition, avian retroviruses can infect cell lines derived from tumors in RIP-Tag; RIP-tva mice with high efficiency. The cell lines can also be used to characterize the metastatic factors. Here we demonstrate how to utilize this mouse model and cell lines to assess the functions of candidate genes in tumor metastasis.

The raccoon polyomavirus genome and tumor antigen transcription are stable and abundant in neuroglial tumors.

UNLABELLED: Raccoon polyomavirus (RacPyV) is associated with 100% of neuroglial tumors in free-ranging raccoons. Other tumor-associated polyomaviruses (PyVs), including simian virus 40 (SV40), murine PyV, and Merkel cell PyV, are found integrated in the host genome in neoplastic cells, where they constitutively express splice variants of the tumor antigen (TAg) gene. We have previously reported that RacPyV exists only as an episome (nonintegrated) in neuroglial tumors. Here, we have investigated TAg transcription in primary tumor tissue by transcriptome analysis, and we identified the alternatively spliced TAg transcripts for RacPyV. We also determined that TAg was highly transcribed relative to host cellular genes. We further colocalized TAg DNA and mRNA by in situ hybridization and found that the majority of tumor cells showed positive staining. Lastly, we examined the stability of the viral genome and TAg transcription by quantitative reverse transcriptase PCR in cultured tumor cells in vitro and in a mouse xenograft model. When tumor cells were cultured in vitro, TAg transcription increased nearly 2 log-fold over that of parental tumor tissue by passage 17. Both episomal viral genome and TAg transcription were faithfully maintained in culture and in tumors arising from xenotransplantation of cultured cells in mice. This study represents a minimal criterion for RacPyV's association with neuroglial tumors and a novel mechanism of stability for a polyomavirus in cancer. IMPORTANCE: The natural cycle of polyomaviruses in mammals is to persist in the host without causing disease, but they can cause cancer in humans or in other animals. Because this is an unpredictable and rare event, the oncogenic potential of polyomavirus is primarily evaluated in laboratory animal models. Recently, raccoon polyomavirus (RacPyV) was identified in neuroglial tumors of free-ranging raccoons. Viral copy number was consistently high in these tumors but was low or undetectable in nontumor tissue or in unaffected raccoons. Unlike other oncogenic polyomaviruses, RacPyV was episomal, not integrated, in these tumors. To determine the stability of the viral genome and sustained transcription of the oncogenic tumor antigen genes, we cultured primary raccoon tumor cells and passaged them in mice, confirming the nonintegrated state of the virus and the maintenance of viral gene transcription throughout. RacPyV provides a naturally occurring and tractable model for a novel mechanism of polyomavirus-mediated oncogenesis.

The piggyBac transposon-mediated expression of SV40 T antigen efficiently immortalizes mouse embryonic fibroblasts (MEFs).

Mouse embryonic fibroblasts (MEFs) are mesenchymal stem cell (MSC)-like multipotent progenitor cells and can undergo self-renewal and differentiate into to multiple lineages, including bone, cartilage and adipose. Primary MEFs have limited life span in culture, which thus hampers MEFs' basic research and translational applications. To overcome this challenge, we investigate if piggyBac transposon-mediated expression of SV40 T antigen can effectively immortalize mouse MEFs and that the immortalized MEFs can maintain long-term cell proliferation without compromising their multipotency. Using the piggyBac vector MPH86 which expresses SV40 T antigen flanked with flippase (FLP) recognition target (FRT) sites, we demonstrate that mouse embryonic fibroblasts (MEFs) can be efficiently immortalized. The immortalized MEFs (piMEFs) exhibit an enhanced proliferative activity and maintain long-term cell proliferation, which can be reversed by FLP recombinase. The piMEFs express most MEF markers and retain multipotency as they can differentiate into osteogenic, chondrogenic and adipogenic lineages upon BMP9 stimulation in vitro. Stem cell implantation studies indicate that piMEFs can form bone, cartilage and adipose tissues upon BMP9 stimulation, whereas FLP-mediated removal of SV40 T antigen diminishes the ability of piMEFs to differentiate into these lineages, possibly due to the reduced expansion of progenitor populations. Our results demonstrate that piggyBac transposon-mediated expression of SV40 T can effectively immortalize MEFs and that the reversibly immortalized piMEFs not only maintain long-term cell proliferation but also retain their multipotency. Thus, the high transposition efficiency and the potential footprint-free natures may render piggyBac transposition an effective and safe strategy to immortalize progenitor cells isolated from limited tissue supplies, which is essential for basic and translational studies.

Inducible and coupled expression of the polyomavirus middle T antigen and Cre recombinase in transgenic mice: an in vivo model for synthetic viability in mammary tumour progression.

INTRODUCTION: Effective in vivo models of breast cancer are crucial for studying the development and progression of the disease in humans. We sought to engineer a novel mouse model of polyomavirus middle T antigen (PyV mT)-mediated mammary tumourigenesis in which inducible expression of this well-characterized viral oncoprotein is coupled to Cre recombinase (TetO-PyV mT-IRES-Cre recombinase or MIC). METHODS: MIC mice were crossed to the mouse mammary tumour virus (MMTV)-reverse tetracycline transactivator (rtTA) strain to generate cohorts of virgin females carrying one or both transgenes. Experimental (rtTA/MIC) and control (rtTA or MIC) animals were administered 2 mg/mL doxycycline beginning as early as eight weeks of age and monitored for mammary tumour formation, in parallel with un-induced controls of the same genotypes. RESULTS: Of the rtTA/MIC virgin females studied, 90% developed mammary tumour with complete penetrance to all glands in response to doxycycline and a T50 of seven days post-induction, while induced or un-induced controls remained tumour-free after one year of induction. Histological analyses of rtTA/MIC mammary glands and tumour revealed that lesions followed the canonical stepwise progression of PyV mT tumourigenesis, from hyperplasia to mammary intraepithelial neoplasia/adenoma, carcinoma, and invasive carcinoma that metastasizes to the lung; at each of these stages expression of PyV mT and Cre recombinase transgenes was confirmed. Withdrawal of doxycycline from rtTA/MIC mice with end-stage mammary tumours led to rapid regression, yet animals eventually developed PyV mT-expressing and -non-expressing recurrent masses with varied tumour histopathologies. CONCLUSIONS: We have successfully created a temporally regulated mouse model of PyV mT-mediated mammary tumourigenesis that can be used to study Cre recombinase-mediated genetic changes simultaneously. While maintaining all of the hallmark features of the well-established constitutive MMTV-PyV mT model, the utility of this strain derives from the linking of PyV mT and Cre recombinase transgenes; mammary epithelial cells are thereby forced to couple PyV mT expression with conditional ablation of a given gene. This transgenic mouse model will be an important research tool for identifying synthetic viable genetic events that enable PyV mT tumours to evolve in the absence of a key signaling pathway.

Expression of hepatitis B virus 1.3-fold genome plasmid in an SV40 T-antigen-immortalized mouse hepatic cell line.

AIM: To investigate the expression of the hepatitis B virus (HBV) 1.3-fold genome plasmid (pHBV1.3) in an immortalized mouse hepatic cell line induced by SV40 T-antigen (SV40T) expression. METHODS: Mouse hepatic cells were isolated from mouse liver tissue fragments from 3-5 d old Kunming mice by the direct collagenase digestion method and cultured in vitro. The pRSV-T plasmid was transfected into mouse hepatic cells to establish an SV40LT-immortalized mouse hepatic cell line. The SV40LT-immortalized mouse hepatic cells were identified and transfected with the pHBV1.3 plasmid. The levels of hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) in the supernatant were determined by an electrochemiluminescence immunoassay at 24, 48, 72 and 96 h after transfection. The expressions of HBsAg and hepatitis B c antigen (HBcAg) in the cells were investigated by indirect immunofluorescence analysis. The presence of HBV DNA replication intermediates in the transfected cells and viral particles in the supernatant of the transfected cell cultures was monitored using the Southern hybridization assay and transmission electronic microscopy, respectively. RESULTS: The pRSV-T plasmid was used to immortalize mouse hepatocytes and an SV40LT-immortalized mouse hepatic cell line was successfully established. SV40LT-immortalized mouse hepatic cells have the same morphology and growth characteristics as primary mouse hepatic cells can be subcultured and produce albumin and cytokeratin-18 in vitro. Immortalized mouse hepatic cells did not show the characteristics of tumor cells, as alpha-fetoprotein levels were comparable (0.58 ± 0.37 vs 0.61 ± 0.31, P = 0.37). SV40LT-immortalized mouse hepatic cells were then transfected with the pHBV1.3 plasmid, and it was found that the HBV genome replicated in SV40LT-immortalized mouse hepatic cells. The levels of HBsAg and HBeAg continuously increased in the supernatant after the transfection of pHBV1.3, and began to decrease 72 h after transfection. The expressions of HBsAg and HBcAg were observed in the pHBV1.3-transfected cells. HBV DNA replication intermediates were also observed at 72 h after transfection, including relaxed circular DNA, double-stranded DNA and single-stranded DNA. Furthermore, a few 42 nm Dane particles, as well as many 22 nm subviral particles with a spherical or filamentous shape, were detected in the supernatant. CONCLUSION: SV40T expression can immortalize mouse hepatic cells, and the pHBV1.3-transfected SV40T-immortalized mouse hepatic cell line can be a new in vitro cell model.

Host response to polyomavirus infection is modulated by RNA adenosine deaminase ADAR1 but not by ADAR2.

Adenosine deaminases acting on RNA (ADARs) catalyze the C-6 deamination of adenosine (A) to produce inosine (I), which behaves as guanine (G), thereby altering base pairing in RNAs with double-stranded character. Two genes, adar1 and adar2, are known to encode enzymatically active ADARs in mammalian cells. Furthermore, two size forms of ADAR1 are expressed by alternative promoter usage, a short (p110) nuclear form that is constitutively made and a long (p150) form that is interferon inducible and present in both the cytoplasm and nucleus. ADAR2 is also a constitutively expressed nuclear protein. Extensive A-to-G substitution has been described in mouse polyomavirus (PyV) RNA isolated late times after infection, suggesting modification by ADAR. To test the role of ADAR in PyV infection, we used genetically null mouse embryo fibroblast cells deficient in either ADAR1 or ADAR2. The single-cycle yields and growth kinetics of PyV were comparable between adar1(-/-) and adar2(-/-) genetic null fibroblast cells. While large T antigen was expressed to higher levels in adar1(-/-) cells than adar2(-/-) cells, less difference was seen in VP1 protein expression levels between the two knockout MEFs. However, virus-induced cell killing was greatly enhanced in PyV-infected adar1(-/-) cells compared to that of adar2(-/-) cells. Complementation with p110 protected cells from PyV-induced cytotoxicity. UV-irradiated PyV did not display any enhanced cytopathic effect in adar1(-/-) cells. Reovirus and vesicular stomatitis virus single-cycle yields were comparable between adar1(-/-) and adar2(-/-) cells, and neither reovirus nor VSV showed enhanced cytotoxicity in adar1(-/-)-infected cells. These results suggest that ADAR1 plays a virus-selective role in the host response to infection.

A combination of MSH2 DNA mismatch repair deficiency and expression of the SV40 large T antigen results in cisplatin resistance of mouse embryonic fibroblasts.

Mutations in the human mismatch repair (MMR) genes are associated with hereditary non-polyposis colorectal cancer as well as other sporadic cancers. MMR gene mutations have been implicated in the resistance of human tumours to cisplatin and several tumour-derived MMR-deficient cells show cisplatin resistance in vitro. In addition, hypoxia, a common feature of the tumour microenvironment, has been shown to influence tumour responses to conventional cancer treatments. We have examined the role of the mMSH2 MMR protein on repair of cisplatin-damaged DNA and cisplatin sensitivity in mMSH2-deficient murine fibroblasts and mMSH2-proficient controls under conditions of normoxia and hypoxia. Sensitivity to cisplatin was measured using the MTT assay and clonogenic survival. Repair of cisplatin-damaged DNA was measured using a host cell reactivation (HCR) assay employing a non-replicating recombinant virus expressing the ß-galactosidase reporter gene. Sensitivity to cisplatin was significantly less and HCR of the cisplatin-damaged reporter gene was significantly greater in SV40-transformed mMSH2-deficient cells (MS5-7) compared to mMSH2-proficient controls (BC1-6) under both normoxic and hypoxic conditions. In contrast, sensitivity to cisplatin was significantly greater and HCR was similar in primary mMSH2-deficient compared to mMSH2-proficient murine fibroblasts under both normoxic and hypoxic conditions. Sensitivity to cisplatin was also significantly greater and HCR was similar in primary mMSH2-deficient compared to mMSH2-proficient murine fibroblasts transfected with a control plasmid under both normoxic and hypoxic conditions. In contrast, sensitivity to cisplatin was less and HCR was similar in primary mMSH2-deficient compared to mMSH2-proficient murine fibroblasts transfected with a plasmid expressing SV40 large T antigen under both normoxic and hypoxic conditions. These results suggest that loss of MMR alone does not result in increased resistance to cisplatin in murine fibroblasts and that additional concomitant alterations in cells expressing the SV40 large T antigen are responsible for cisplatin resistance through a modulation of DNA repair capacity and/or apoptosis.

Transgenic expression of polyomavirus middle T antigen in the mouse prostate gives rise to carcinoma.

The middle T (MT) antigen of polyomavirus has provided fundamental insights into the regulation of mammalian cell growth in vitro and important animal models for the analysis of tumor induction. The mouse mammary tumor virus (MMTV)-MT model of breast cancer has been important for probing the cellular signaling pathways in mammary tumorigenesis. MT itself has no intrinsic enzymatic activity but, rather, transforms by binding to and activating key intracellular signaling molecules, phosphatidylinositol 3-kinase (PI3-kinase) being the best studied of these. Thus, MT mimics a constitutively activated receptor tyrosine kinase (RTK). Our recent work suggests that MT signaling, like that of RTKs, is often quite dependent on cellular context in vitro. Here, we examine contextual effects on signaling in animal models as well. In this study, we generated transgenic mice in which MT is expressed in the mouse prostate under the control of an (ARR)2-Probasin promoter. All male transgenic mice displayed mouse prostatic intraepithelial neoplasia (mPIN) in the ventral and dorsal/lateral prostate as early as 8 weeks of age. Notably, during the course of tumor development over time, invasive cancer, reactive stroma, and infiltration of inflammatory cells were seen. Transcriptional profiling analyses show regulation of multiple pathways, with marked upregulation of both the NF-κB and inflammatory pathways. Comparison of expression profiles of our MT prostate model with those from an MMTV-MT breast model (23) shows both tissue-specific and tissue-independent MT effects. The signature of genes regulated by MT in a tissue-independent manner may have prognostic value.

Molecular characterization of tumors from a transgenic mouse adrenal tumor model: comparison with human pheochromocytoma.

Adrenal neuroblastoma and pheochromocytoma have the same embryonic origin from neural crest cells and mainly arise from the adrenal medulla. Recently, transgenic mice exhibiting tumors in the bilateral adrenal medulla by the expression of SV40 T-antigen were developed. In this study, we investigated mRNA expression in adrenal tumors of transgenic mice and compared them with human pheochromocytoma by DNA microarray analysis. To compare mouse adrenal tumors and human pheochromacytoma, we found that the expressions of noradrenergic neuron-related genes, including dopa decarboxylase, phenylethanolamine-N-methyltransferase and chromogranin B, were up-regulated in humans but not in mice; however, the expression of neuroblastoma-related genes, including Mycn, paired-like homeobox 2b, gamma-aminobutyric acid A receptor beta3 subunit, islet 1 and kinesin family member 1A, was up-regulated in both species. From the gene expression profiles, the characterization of mouse adrenal tumor, may be similar to that of human adrenal neuroblastoma rather than pheochromacytomas. This mouse model would be a useful tool for the development of anti-cancer drugs and for understanding the etiology of adrenal neuroblastoma.

In vivo imaging of an inducible oncogenic tumor antigen visualizes tumor progression and predicts CTL tolerance.

Visualizing oncogene/tumor Ag expression by noninvasive imaging is of great interest for understanding processes of tumor development and therapy. We established transgenic (Tg) mice conditionally expressing a fusion protein of the SV40 large T Ag and luciferase (TagLuc) that allows monitoring of oncogene/tumor Ag expression by bioluminescent imaging upon Cre recombinase-mediated activation. Independent of Cre-mediated recombination, the TagLuc gene was expressed at low levels in different tissues, probably due to the leakiness of the stop cassette. The level of spontaneous TagLuc expression, detected by bioluminescent imaging, varied between the different Tg lines, depended on the nature of the Tg expression cassette, and correlated with Tag-specific CTL tolerance. Following liver-specific Cre-loxP site-mediated excision of the stop cassette that separated the promoter from the TagLuc fusion gene, hepatocellular carcinoma development was visualized. The ubiquitous low level TagLuc expression caused the failure of transferred effector T cells to reject Tag-expressing tumors rather than causing graft-versus-host disease. This model may be useful to study different levels of tolerance, monitor tumor development at an early stage, and rapidly visualize the efficacy of therapeutic intervention versus potential side effects of low-level Ag expression in normal tissues.

Precise conditional immortalization of mouse cells using tetracycline-regulated SV40 large T-antigen.

Cellular immortalization provides a way for expansion and subsequent molecular characterization of rare cell types. Ideally, immortalization can be achieved by the reversible expression of immortalizing proteins. Here, we describe the use of conditional immortalization based on a modified tetracycline-regulated system for the expression of SV40 large T-antigen in embryonic stem (ES) cells and mice. The modified system relies on a codon improved reverse tetracycline transactivator (irtTA) fused to the ligand-binding domain (LBD) of the androgen receptor (irtTA-ABD) or of a mutated glucocorticoid receptor (irtTA-GBD*). Induction of T-antigen is conferred only after addition of two ligands, one to activate the LBD (mibolerone for irtTA-ABD or dexamethasone for irtTA-GBD*) and one to activate the tetracycline transactivator (doxycycline). In ES cells, changes in gene expression upon large T induction were limited and reversible upon deinduction. Similarly, expression of T-antigen was very tightly regulated in mice. We have isolated and expanded bone marrow mesenchymal stem cells that could be genetically manipulated and maintained their differentiation properties after several passages of expansion under conditions that induce the expression of large T-antigen.

Simian virus 40 T/t antigens and lamin A/C small interfering RNA rescue the phenotype of an Epstein-Barr virus protein kinase (BGLF4) mutant.

The Epstein-Barr virus (EBV)-encoded viral protein kinase, EBV-PK (the BGLF4 gene product), is required for efficient nuclear viral egress in 293 cells. However, since EBV-PK phosphorylates a number of different viral and cellular proteins (including lamin A/C), the relative importance of each target during lytic viral replication remains unclear. We show here that an EBV PK mutant (PKmut; containing stop codons at residues 1 and 5 in EBV-PK) is highly defective for release of infectious virus from 293 cells but not 293T cells. Furthermore, the phenotype of the PKmut in 293 cells is substantially reversed by expression of the simian virus 40 (SV40) large (T) and small (t) T antigens. Efficient rescue requires the presence of both SV40 T/t proteins. We show that 293T cells have a much higher level of constitutive lamin A/C phosphorylation than do 293 cells over residues (S22 and S392) that promote phosphorylation-dependent nuclear disassembly and that both large T and small t contribute to enhanced lamin A/C phosphorylation. Finally, we demonstrate that knockdown of lamin A/C expression using small interfering RNA also rescues the PKmut phenotype in 293 cells. These results suggest that essential roles of EBV-PK during lytic viral replication include the phosphorylation and dispersion of lamin A/C.

Nuclear localization of Merkel cell polyomavirus large T antigen in Merkel cell carcinoma.

To clarify whether mutations in the large T gene encoded by Merkel cell polyomavirus affect the expression and function of large T antigen in Merkel cell carcinoma cases, we investigated the expression of large T antigen in vitro and in vivo. Immunohistochemistry using a rabbit polyclonal antibody revealed that large T antigen was expressed in the nuclei of Merkel cell carcinoma cells with Merkel cell polyomavirus infection. Deletion mutant analyses identified an Arg-Lys-Arg-Lys sequence (amino acids 277-280) as a nuclear localization signal in large T antigen. Sequence analyses revealed that there were no mutations in the nuclear localization signal in any of the eleven Merkel cell polyomavirus strains examined. Furthermore, stop codons were not observed in the upstream of the nuclear localization signal in any of the Merkel cell carcinoma cases examined. These data suggest that the nuclear localization signal is highly conserved and functional in Merkel cell carcinoma cases.

Archetype JC virus efficiently propagates in kidney-derived cells stably expressing HIV-1 Tat.

Pathogenic JCV with rearranged regulatory regions (PML-type) causes PML, a demyelinating disease, in the brains of immunocompromised patients. On the other hand, archetype JCV persistently infecting the kidney is thought to be converted to PML-type virus during JCV replication in the infected host under immunosuppressed conditions. In addition, Tat protein, encoded by HIV-1, markedly enhances the expression of a reporter gene under control of the JCV late promoter. In order to examine the influence of Tat on JCV propagation, we used kidney-derived COS-7 cells, which only permit archetype JCV, and established COS-tat cells, which express HIV-1 Tat stably. We found that the extent of archetype JCV propagation in COS-tat cells is significantly greater than in COS-7 cells. On the other hand, COS-7 cells express SV40 T antigen, which is a strong stimulator of archetype JCV replication. The expression of SV40 T antigen was enhanced by HIV-1 Tat slightly according to real-time RT-PCR, this was not closely related to JCV replication in COS-tat cells. The efficiency of JCV propagation depended on the extent of expression of functional Tat. To our knowledge, this is the first report of increased production of archetype JCV in a culture system using cell lines stably expressing HIV-1 Tat. We propose here that COS-tat cells are a useful tool for studying the role of Tat in archetype JCV replication in the development of PML.

Genistein and resveratrol, alone and in combination, suppress prostate cancer in SV-40 tag rats.

BACKGROUND: Chemoprevention utilizing dietary agents is an effective means to slow the development of prostate cancer. We evaluated the potential additive and synergistic effects of genistein and resveratrol for suppressing prostate cancer in the Simian Virus-40 T-antigen (SV-40 Tag) targeted probasin promoter rat model, a transgenic model of spontaneously developing prostate cancer. METHODS: Rats were fed genistein or resveratrol (250 mg/kg AIN-76A diet) alone and in combination, and a low-dose combination (83 mg genistein + 83 mg resveratrol/kg diet). Histopathology and mechanisms of action studies were conducted at 30 and 12 weeks of age, respectively. RESULTS: Genistein, resveratrol, and the high-dose combination treatments suppressed prostate cancer. The low-dose combination did not elicit protection against prostate cancer and was most likely below the effective dose for causing significant histopathological changes. Total genistein and resveratrol concentrations in the blood reached 2,160 and 211 nM, respectively in rats exposed to the single treatments. Polyphenol treatments decreased cell proliferation and insulin-like growth factor-1 (IGF-1) protein expression in the prostate. In addition, genistein as a single agent induced apoptosis and decreased steroid receptor coactivator-3 (SRC-3) in the ventral prostate (VP). CONCLUSIONS: Genistein and resveratrol, alone and in combination, suppress prostate cancer development in the SV-40 Tag model. Regulation of SRC-3 and growth factor signaling proteins are consistent with these nutritional polyphenols reducing cell proliferation and increasing apoptosis in the prostate.

Establishment of three novel human malignant pleural mesothelioma cell lines: morphological and cytogenetical studies and EGFR mutation status.

UNLABELLED: The incidence of mesothelioma is estimated to rise sharply worldwide, including Japan, in the next two decades. Molecular and proteomic studies are urgently required to elucidate the pathobiology of malignant mesothelioma. This paper describes the characterization of novel human malignant pleural mesothelioma cell lines representing the sarcomatoid, epithelioid and biphasic subtypes. MATERIALS AND METHODS: Established pleural effusion fluid cell lines were observed using phase-contrast microscopy and transmission electron microscopy. The immunoreactivity of the cells was evaluated using immunohistochemistiy, FACS analysis and Western blotting. The expression of SV40 large cell antigen and the EGFR mutation status were also analyzed. RESULTS: The cell lines had different morphological and immunophenotypic characteristics. All cell lines showed immunophenotypic marker expression of vimentin, mesothelin and N-cadherin, but no expression of CEA or E-cadherin. At the electron microscopic level, a cell surface rich in microvilli confirmed mesothelial origin of the cell lines. Karyotype analyses showed complex abnormalities in all cell lines. Neither EGFR mutations relevant to tyrosine kinase inhibitor responsiveness nor the expression of SV40 large cell antigen was detected in any of the cell lines. CONCLUSION: FACS analysis is more sensitive for evaluating mesothelin expression than immunohistochemistry of cut specimens. Irrespective of the expression of EGFR on FACS analysis, no EGFR mutation was detected. These three cell lines may be useful for studying cellular, molecular and genetic aspects of mesothelioma.

Establishment of a gastric epithelial progenitor cell line from a transgenic mouse expressing the simian virus 40 large T antigen gene in the parietal cell lineage.

OBJECTIVE: In this study the gastric mucosa of transgenic mice expressing the simian virus 40 large T antigen gene in the parietal cell lineage is used to establish and characterize a new epithelial progenitor cell line. In these mice, proliferation and amplification of preparietal cells preclude their maturation into acid-secreting parietal cells leading to achlorohydria, hyperplasia, dysplasia and eventually gastric adenocarcinoma. MATERIALS AND METHODS: Enzymatically dispersed gastric epithelial cells were cultured, cloned and screened using immunohistochemical methods, for expression of a variety of biomarkers of differentiated pit, parietal, enteroendocrine and neck/zymogenic cells. RESULTS: A biomarker-deficient cell line whose ultrastructural features resembled those of mouse gastric epithelial progenitor cells was established. Treatment with either hydrocortisone or oestrogen significantly enhanced proliferation of these cells, whereas retinoic acid inhibited their growth. No change in differentiation was detected with any of these treatments; however, when these cells were injected subcutaneously into nude mice, they proliferated to form tumours and undergo partial differentiation towards parietal cell lineage. CONCLUSION: This mouse gastric epithelial progenitor cell line could be useful as an in vitro model to study growth properties, proliferation and differentiation of a subpopulation of gastric epithelial progenitor cells and also to study gastric carcinogenesis.

Parafibromin tumor suppressor enhances cell growth in the cells expressing SV40 large T antigen.

Parafibromin (PF) is a 531-amino acid protein encoded by HRPT2, a putative tumor suppressor gene recently implicated in the autosomal-dominant hyperparathyroidism-jaw tumor familial cancer syndrome and sporadic parathyroid carcinoma. To investigate effects of PF's overexpression on cell proliferation, we performed assays in four different cell lines. The transient overexpression of PF inhibited cell growth in HEK293 and NIH3T3 cells, but enhanced cell growth in the SV40 large T antigen-expressing cell lines such as 293FT and COS7 cells. In 293FT cells, PF was found to interact with SV40 large T antigen and its overexpression promoted entry into the S phase, implying that the interaction enhanced progression through the cell cycle. The tumor suppressor protein PF acts as a positive regulator of cell growth similar to an oncoprotein in the presence of SV40 large T antigen.