Effectiveness and safety of two 18-gauge needle types on native and allograft renal biopsies.

Percutaneous biopsy is a key diagnostic tool for both native and allograft kidney diseases. Adequacy criteria vary, but at a minimum, a biopsy should allow the pathologist to reach a diagnosis and provide prognostic information such as the degree of interstitial fibrosis and tubular atrophy (IF/TA) and percentage of glomerulosclerosis. Whereas most studies use glomerular counts as a surrogate for biopsy adequacy, the amount and preservation of tubulointerstitium is equally important, considering IF/TA is a major prognostic parameter for most medical renal diseases. Many studies have compared the diagnostic adequacy of different gauge needles; however few have investigated performance differences between same gauge needles. In this study, we retrospectively analyzed 235 renal biopsies performed at a single center in Canada over 2years to compare the utilization, safety, diagnostic and prognostic performance of two 18-gauge needles in native and allograft kidney biopsies. We found no significant difference in needle utilization between native and allograft kidneys, or between trainees and staff radiologists. The total tissue yielded area, glomerular counts, percentage of inadequate biopsies and number of passes were similar; however the number of cases in which IF/TA evaluation was deemed not possible was higher for biopsies using disposable instrument needles (4.3% vs. 0%; p=0.01). These also showed greater number of tissue fragments (median 4 for reusable vs 3 for disposable; p=0.04). We postulate that the increased tissue fragmentation might have impaired the pathologists ability to accurately assess interstitial fibrosis and tubular atrophy in biopsies obtained with the disposable instrument needles.

Excision of HIV-1 DNA by gene editing: a proof-of-concept in vivo study.

A CRISPR/Cas9 gene editing strategy has been remarkable in excising segments of integrated HIV-1 DNA sequences from the genome of latently infected human cell lines and by introducing InDel mutations, suppressing HIV-1 replication in patient-derived CD4+ T-cells, ex vivo. Here, we employed a short version of the Cas9 endonuclease, saCas9, together with a multiplex of guide RNAs (gRNAs) for targeting the viral DNA sequences within the 5'-LTR and the Gag gene for removing critically important segments of the viral DNA in transgenic mice and rats encompassing the HIV-1 genome. Tail-vein injection of transgenic mice with a recombinant Adeno-associated virus 9 (rAAV9) vector expressing saCas9 and the gRNAs, rAAV:saCas9/gRNA, resulted in the cleavage of integrated HIV-1 DNA and excision of a 978 bp DNA fragment spanning between the LTR and Gag gene in the spleen, liver, heart, lung and kidney as well as in the circulating lymphocytes. Retro-orbital inoculation of rAAV9:saCas9/gRNA in transgenic rats eliminated a targeted segment of viral DNA and substantially decreased the level of viral gene expression in circulating blood lymphocytes. The results from the proof-of-concept studies, for the first time, demonstrate the in vivo eradication of HIV-1 DNA by CRISPR/Cas9 on delivery by an rAAV9 vector in a range of cells and tissues that harbor integrated copies of viral DNA.

Effects of a prebiotic, Immunogen®, on feed utilization, body composition, immunity and resistance to Aeromonas hydrophila infection in the common carp Cyprinus carpio (Linnaeus) fingerlings.

This study evaluated the effects of a commercial prebiotic, Immunogen, on feed utilization, growth rate, immunity promotion and carcass composition of the common carp Cyprinus carpio fingerlings. The fingerlings were adopted for 2 weeks and then reared in triplicate groups in 250-l tanks (n = 15 per tank with average initial weights of 11.12 ± 0.55 g). The fish fed on five isonitrogenous and isoenergetic experimental diets containing different levels of Immunogen (0, 0.5, 1, 1.5 and 2.5 g prebiotic/kg diet) to apparent satiation thrice a day for 8 weeks. Weight gain showed no differences among the groups fed different Immunogen levels. Both feed efficiency ratio and protein efficiency ratio significantly (p < 0.05) increased with increasing Immunogen levels from 0.5 to 1.5 g/kg diet. The highest protein content (p < 0.05) was found in the fish fed a diet containing 2.5 g/kg prebiotic. Haematological parameters and plasma total protein concentration were also significantly higher (p < 0.05) in the fingerlings fed diets containing 1.5 and 2.5 g/kg prebiotic in relation to the control. The control fish contained the highest mean of total bacterial counts. The lowest mean (p < 0.05) of total bacterial counts was observed in the fish fed the diet containing 2.5 g/kg Immunogen. The present study reveals that a dietary Immunogen supplementation from 1 to 1.5 g/kg is capable to improve the feed efficiency and growth performance of C. carpio fingerlings as well as their resistance to A. hydrophila infection.

Effects of a probiotic, protexin, on the growth performance and hematological parameters in the Oscar (Astronotus ocellatus) fingerlings.

This study examined the effects of a probiotic, protexin, on the growth performance and hematological parameters in an ornamental fish, the Oscar Astronotus ocellatus fingerlings. A completely randomized experimental design was applied with three experimental diets each with three replicates. A commercial food, BioMar, was supplemented with protexin at levels of 0.15, 0.5, and 1.0 g kg(-1) dry food and fed three times a day for 60 days. The control diet was prepared with no protexin supplementation. The experimental fish were biometried every 15 days to compare their growth rates at each treatment. For hematological assays, blood samples were prepared every 30 days to measure such parameters as red and white blood cells, hemoglobin, hematocrit, and percentages of lymphocytes, monocytes, neutrophiles, basophiles, and eosinophiles. Based on the results, the fingerlings fed a 0.15 g kg(-1) supplemented food were significantly different from the fish in the other treatments and in the control, with the highest mean of both final weight (35.07 ± 1.19) and body weight gain (30.17 ± 1.08). Significant differences in both hemoglobin concentration and mean red and white blood cells were found between the experimental groups and the control within 2 months. The highest hemoglobin concentration and also red and white blood cells was observed in the fish-fed 0.15 dietary protexin in both months. The results of this study show that the probiotic, protexin, at a level of 0.15 g kg(-1) dry food could have measurable effects on the growth and hematological parameters in the Oscar A. ocellatus fingerlings.

Intraoperative 'no go' donor hepatectomies in living donor liver transplantation.

Donor safety is the paramount concern of living donor liver transplantation (LDLT). Although LDLT is employed worldwide, there is little data on rates and causes of 'no go' hepatectomies-patients brought to the operating room for possible donor hepatectomy whose procedure was aborted. We performed a single-center, retrospective review of all patients brought to the operating room for donor hepatectomy between October 2000 and November 2008. Of 257 right lobe donors, the donor operation was aborted in 12 cases (4.7%). The main reasons for stopping the operation were aberrant ductal or vascular anatomy (seven cases), unsuitable liver quality (three cases) or unexpected intraoperative events (two cases). Over the median period of follow-up of 23 months, there were no long-term complications of patients with aborted donor procedures. This report focuses exclusively on an important issue: the frequency and causes of no go decisions at a single large volume North American LDLT center. The rate of no go donor hepatectomies should be as low as possible without compromising donor safety--however, even with rigorous preoperative evaluation the rate of donor abortions will be significant. The default surgical position should always be to abort the donor operation if there is an unexpected finding that places the donor at increased risk.

Observation of the fastest chemical processes in the radiolysis of water.

Elementary processes associated with ionization of liquid water provide a framework for understanding radiation-matter interactions in chemistry and biology. Although numerous studies have been conducted on the dynamics of the hydrated electron, its partner arising from ionization of liquid water, H2O+, remains elusive. We used tunable femtosecond soft x-ray pulses from an x-ray free electron laser to reveal the dynamics of the valence hole created by strong-field ionization and to track the primary proton transfer reaction giving rise to the formation of OH. The isolated resonance associated with the valence hole (H2O+/OH) enabled straightforward detection. Molecular dynamics simulations revealed that the x-ray spectra are sensitive to structural dynamics at the ionization site. We found signatures of hydrated-electron dynamics in the x-ray spectrum.

A 39-kD DNA-binding protein from mouse brain stimulates transcription of myelin basic protein gene in oligodendrocytic cells.

The MB1 regulatory sequence of the myelin basic protein (MBP) gene spanning between nucleotides -14 to -50 with respect to the transcription start site is critical for cell type-specific transcription of the MBP gene, which encodes the major protein component of myelin sheath in cells derived from the central nervous system (CNS). This regulatory sequence has the ability to interact with a developmentally controlled DNA-binding protein from mouse brain that stimulates transcription of MBP promoter in an in vitro system (Haas, S., J. Gordon, and K. Khalili. 1993. Mol. Cell. Biol. 13:3103-3112). Here, we report the purification of a 39-kD protein from mouse brain tissue at the peak of myelination and MBP production that binds to the MB1 regulatory motif. Following partial amino acid sequence analysis, we have identified a complementary DNA encoding a 39-kD DNA-binding protein called pur alpha. Expression of pur alpha cDNA in the prokaryotic and eukaryotic cells resulted in the synthesis of a protein with characteristics similar to the purified brain-derived 39-kD protein in band shift competition assays. Cotransfection of the recombinant pur alpha expressor plasmid with MBP promoter construct indicated that Pur alpha stimulates transcription of the MBP promoter in oligodendrocytic cells, and that the nucleotide sequence required for binding of the 39-kD Pur alpha to DNA within the MB1 region is crucial for this activity. Moreover, transient expression of Pur alpha caused elevation in the level of endogenous MBP RNA in oligodendrocytic cells. Thus, Pur alpha, a sequence-specific DNA-binding protein upon binding to MB1 regulatory region may play a significant role in determining the cell type-specific expression of MBP in brain.

Inhibition of IGF-I receptor in anchorage-independence attenuates GSK-3beta constitutive phosphorylation and compromises growth and survival of medulloblastoma cell lines.

We have previously reported that insulin-like growth factor-I (IGF-I) supports growth and survival of mouse and human medulloblastoma cell lines, and that IGF-I receptor (IGF-IR) is constitutively phosphorylated in human medulloblastoma clinical samples. Here, we demonstrate that a specific inhibitor of insulin-like growth factor-I receptor (IGF-IR), NVP-AEW541, attenuated growth and survival of mouse (BsB8) and human (D384, Daoy) medulloblastoma cell lines. Cell cycle analysis demonstrated that G1 arrest and apoptosis contributed to the action of NVP-AEW54. Interestingly, very aggressive BsB8 cells, which derive from cerebellar tumors of transgenic mice expressing viral oncoprotein (large T-antigen from human polyomavirus JC) became much more sensitive to NVP-AEW541 when exposed to anchorage-independent culture conditions. This high sensitivity to NVP-AEW54 in suspension was accompanied by the loss of GSK-3beta constitutive phosphorylation and was independent from T-antigen-mediated cellular events (Supplementary Materials). BsB8 cells were partially rescued from NVP-AEW541 by GSK3beta inhibitor, lithium chloride and were sensitized by GSK3beta activator, sodium nitroprusside (SNP). Importantly, human medulloblastoma cells, D384, which demonstrated partial resistance to NVP-AEW541 in suspension cultures, become much more sensitive following SNP-mediated GSK3beta dephosphorylation (activation). Our results indicate that hypersensitivity of medulloblastoma cells in anchorage-independence is linked to GSK-3beta activity and suggest that pharmacological intervention against IGF-IR with simultaneous activation of GSK3beta could be highly effective against medulloblastomas, which have intrinsic ability of disseminating the CNS via cerebrospinal fluid.

Interaction of retinoblastoma protein family members with large T-antigen of primate polyomaviruses.

The retinoblastoma gene product pRb and other members of the Rb family of pocket proteins have a central role in the regulation of cell cycle progression. Soon after its discovery, pRb was found to interact with the transforming oncoproteins of DNA tumor viruses and this led to rapid advances in our understanding of the mechanisms of viral transformation and cell cycle progression. DNA viruses of the polyomavirus family have small, circular, double-stranded DNA genomes contained within non-enveloped icosahedral capsids and are highly tumorigenic in experimental animals. At least three types of polyomavirus infect humans: JC virus (JCV), BK virus (BKV) and Simian Vacuolating virus-40. The early region of these viruses encodes the transforming proteins large T-antigen and small t-antigen, which are involved in viral replication and also promote transformation of cells in culture and oncogenesis in vivo. Binding of T-antigen to pRb promotes the activation of the E2F family of transcription factors, which induce the expression of cellular genes required for S phase. In the context of lytic infection, this cell cycle progression is necessary for viral replication because polyomaviruses rely on S phase-specific host factors for their DNA synthesis. In the context of cellular transformation and tumorigenesis, T-antigen/pRB interaction is an indispensable event.

Role of the interaction between large T antigen and Rb family members in the oncogenicity of JC virus.

Human polyomaviruses (JC virus, BK virus and simian virus 40) are causative agents of some human diseases and, interestingly, are involved in processes of cell transformation and oncogenesis. These viruses need the cell cycle machinery of the host cell to complete their replication; so they evolved mechanisms that can interfere with the growth control of infected cells and force them into DNA replication. The retinoblastoma family of proteins (pRb), which includes pRb/p105, p107 and pRb2/p130, acts as one of the most important regulators of the G1/S transition of the cell cycle. Rb proteins represent an important target for viral oncoproteins. Early viral T antigens can bind all members of the pRb family, promoting the activation of the E2F family of transcription factors, thus inducing the expression of genes required for the entry to the S phase. The interaction between early viral antigens and cell cycle regulators represents an important mechanism through which viruses deregulate cell cycle and lead to cell transformation. In this review, we will discuss the effects of the interaction between large T antigen and Rb proteins in JC virus-mediated oncogenesis.

Stimulation of alpha 1 (I) procollagen gene expression in NIH-3T3 cells by the human T cell leukemia virus type 1 (HTLV-1) Tax gene.

The mechanisms that regulate the expression of genes encoding extracellular matrix proteins in fibroblasts and other mesenchymal cells have remained elusive. Studies from several laboratories have indicated that Tax, a trans-regulatory protein from the human T cell leukemia virus type I not only augments viral gene expression but also triggers the expression of various cellular genes. Here, we examined the hypothesis that the expression of collagen genes may also be modulated by Tax. NIH-3T3 cells were simultaneously transfected with a Tax expressor plasmid and a chimeric construct containing regulatory sequences (-804 to +42 bp) of the alpha 1(I) procollagen gene (COL1A1) promoter. The results indicated that the promoter activity of the -804 to bp COL1A1 fragment increased up to 12-fold in cells expressing Tax. Deletion analysis revealed that the region of COL1A1 encompassing nucleotides -174 to -84 contained the Tax-responsive elements. A gene segment encompassing nucleotides -187 to -67, which contained this region, proved sufficient to confer Tax inducibility (2.5-fold) to a herpes simplex virus thymidine kinase promoter. Stably transfected NIH-3T3 cell clones that constitutively produce Tax displayed elevated levels of alpha 1(I) procollagen and fibronectin transcripts and increased production and accelerated processing of type I procollagen. These findings suggest that retroviral proteins may be involved in the pathogenesis of idiopathic diseases accompanied by collagen overproduction.

Nuclear proteins in mouse brain cells bind specifically to the myelin basic protein regulatory region.

Expression of myelin basic protein (MBP) in mice is regulated in a cell- and stage-specific manner during brain development. The MBP control region contains multiple cis-acting elements, shown by in vivo and in vitro assays, which are responsible for its unique pattern of transcription. Using synthetic DNA fragments spanning the MBP control region, we have analyzed nuclear proteins obtained from newborn (2-3 d), young adult (18-30 d), and adult (60 d) animals; these nuclear proteins form DNA-protein complexes with the MBP regulatory region. Brain extracts from young adult and adult mice showed enhanced binding activities with the sequences supporting transcriptional activation in glial cells. Deletion analysis of the proximal activating sequence located at position -14 to -50 with respect to the RNA initiation site resulted in identification of a small region, located between nucleotides -14 to -37, which is required for formation of the complexes. Southwestern assay revealed a major 39-kD protein from young adult brain extract that recognizes the sequences between nucleotides -14 to -37. An additional minor 37-kD protein, derived from young adult brain extract, was also found to be associated with this proximal activating region. Of particular interest is the observation that the minor 37-kD protein became more abundant in the extract derived from adult brain, whereas the major 39-kD protein became less abundant. The possible role of these proteins in cell/stage-specific transcription of MBP is discussed.

A developmentally regulated DNA-binding protein from mouse brain stimulates myelin basic protein gene expression.

Transcription of the myelin basic protein (MBP) gene is regulated in a cell-type-specific and developmental stage-specific manner during myelin formation in the murine central nervous system. The 5'-flanking region of the MBP gene contains several regulatory elements that differentially contribute to the cell-type-specific transcription of MBP in cells derived from the central nervous system. The proximal element, termed MB1, which is located between nucleotides -14 and -50 with respect to the RNA start site, has previously been shown to have characteristics of a cell-type-specific enhancer element. In this study, we used band shift and UV cross-linking assays to identify DNA-binding proteins in mouse brain nuclear extract which interact with the MB1 element. Fractionation of these extracts has allowed the identification of a 38- to 41-kDa nuclear protein, derived from mouse brain tissue at the peak of myelination, which specifically binds the MB1 DNA sequence. Fractions enriched in the MB1-binding protein have been shown to stimulate transcription of the MBP promoter in extract derived from HeLa cells. MB1 binding protein activity is expressed in a tissue-specific and development stage-specific pattern which coincides with the pattern of MBP transcription, suggesting that this protein may be a biologically relevant transcription factor for the MBP gene in vivo.

Identification and characterization of a novel GGA/C-binding protein, GBP-i, that is rapidly inducible by cytokines.

Immunosuppressive states with accompanying alterations in cytokine profiles have been postulated to play a vital role in the reactivation of viruses from latency. Cytokines regulate gene expression by activating transcription factors via well-characterized signal transduction pathways. In this study, we report the identification of a novel inducible protein, GBP-i, that binds to a double-stranded GGA/C-rich region of the transcriptional control region of the human papovavirus JC virus (JCV), specifically within the origin of viral DNA replication. GBP-i is distinct from previously characterized GC-box-binding proteins with respect to both its sequence specificity and its electrophoretic mobility on native and denaturing gels. GBP-i responds within 90 min to phorbol myristate acetate stimulation; however, unlike typical phorbol myristate acetate-inducible factors, this rapid induction is regulated primarily at the transcriptional level. Further, the induction of GBP-i appears to be widespread and mediated by many inflammatory cytokines, including interleukin-1 beta, tumor necrosis factor alpha, gamma interferon, and transforming growth factor beta. Interestingly, the induced protein acts as a transcriptional repressor in its native context in the JCVL promoter. However, when its binding sequence is transposed to a heterologous promoter, GBP-i appears to function as a transcriptional activator. The data presented here suggest a role for GBP-i in cytokine-mediated induction of viral and cellular genes.

Reciprocal interaction between two cellular proteins, Puralpha and YB-1, modulates transcriptional activity of JCVCY in glial cells.

Cross communication between regulatory proteins is an important event in the control of eukaryotic gene transcription. Here we have examined the structural and functional interaction between two cellular regulatory proteins, YB-1 and Puralpha, on the 23-bp sequence element derived from the enhancer-promoter of the human polyomavirus JCV. YB-1 and Puralpha are single-stranded DNA binding proteins which recognize C/T- and GC/GA-rich sequences, respectively. Results from band shift studies demonstrated that while both proteins interact directly with their DNA target sequences within the 23-bp motif, each protein can regulate the association of the other one with the DNA. Affinity chromatography and coimmunoprecipitation provide evidence for a direct interaction between Puralpha and YB-1 in the absence of the DNA sequence. Ectopic expression of YB-1 and Puralpha in glial cells synergistically stimulated viral promoter activity via the 23-bp sequence element. Results from mutational studies revealed that residues between amino acids 75 and 203 of YB-1 and between amino acids 85 and 215 of Puralpha are important for the interaction between these two proteins. Functional studies with glial cells indicated that the region within Puralpha which mediates its association with YB-1 and binding to the 23-bp sequence is important for the observed activation of the JCV promoter by the Puralpha and YB-1 proteins. The results of this study suggest that the cooperative interaction between YB-1 and Puralpha mediates the synergistic activation of the human polyomavirus JCV genome by these cellular proteins. The importance of these findings for cellular and viral genes which are regulated by Puralpha and YB-1 is discussed.

Double-stranded RNA unwinding and modifying activity is detected ubiquitously in primary tissues and cell lines.

A double-stranded RNA unwinding and modifying activity was found to be present in a wide range of tissues and cell types. The level of activity did not vary significantly with respect to the state of cell differentiation, cell cycle, or transformation. Thus, the unwinding and modifying activity, localized in the nucleus in somatic cells and capable of converting many adenosine residues to inosine, appears to be one of the housekeeping genes.

An audit of imaging test utilization for the management of lymphoma in an oncology hospital: implications for resource planning?

The purpose of this study was to assist with resource planning by examining the pattern of physician utilization of imaging procedures for lymphoma patients in a dedicated oncology hospital. The proportion of imaging tests ordered for routine follow up with no specific clinical indication was quantified, with specific attention to CT scans. A 3-month audit was performed. The reasons for ordering all imaging procedures (X-rays, CT scans, ultrasound, nuclear scan and MRI) were determined through a retrospective chart review. 411 lymphoma patients had 686 assessments (sets of imaging tests) and 981 procedures (individual imaging tests). Most procedures were CT scans (52%) and chest radiographs (30%). The most common reasons for ordering imaging were assessing response (23%), and investigating new symptoms (19%). Routine follow up constituted 21% of the assessments (142/686), and of these, 82% were chest radiographs (116/142), while 24% (34/142) were CT scans. With analysis restricted to CT scans (296 assessments in 248 patients), the most common reason for ordering CT scans were response evaluation (40%), and suspicion of recurrence and/or new symptom (23%). Follow-up CT scans done with no clinical indication comprised 8% (25/296) of all CT assessments. Staging CT scans were under-represented at 6% of all assessments. Imaging with CT scans for follow up of asymptomatic patients is infrequent. However, scans done for staging new lymphoma patients were unexpectedly low in frequency, due to scans done elsewhere prior to referral. This analysis uncovered utilization patterns, helped resource planning and provided data to reduce unnecessary imaging procedures.

Puralpha: a multifunctional single-stranded DNA- and RNA-binding protein.

Puralpha is a ubiquitous, sequence-specific DNA- and RNA-binding protein which is highly conserved in eukaryotic cells. Puralpha has been implicated in diverse cellular functions, including transcriptional activation and repression, translation and cell growth. Moreover, this protein has been shown to be involved in regulating several human viruses which replicate in the central nervous system (CNS), including human immunodeficiency virus type I (HIV-1) and JC virus (JCV). Puralpha exerts part of its activity by interacting with cellular proteins, including pRb, E2F, cyclin A, Sp1 and members of the Y-box family of proteins, including YB-1 and MSY1, as well as viral proteins such as polyomavirus large T-antigen and HIV-1 Tat. The ability of Puralpha to interact with its target DNA sequence and to associate with several viral and cellular proteins is modulated by RNA. Puralpha has also been shown to be involved in cell growth and proliferation. Its association with pRb, E2F and cyclin A coupled with its fluctuating levels throughout the cell cycle, position Puralpha as a crucial factor in the cell cycle. Moreover, microinjection studies demonstrate that Puralpha causes either a G(1) or G(2) arrest depending on the cell cycle time of injection. The gene encoding Puralpha has been localized to a human locus which is frequently deleted in myelogenous leukemias and other cancers and Puralpha gene deletions have been detected in many cases of lymphoid cancers. The following review details the structural characteristics of Puralpha, its family members and the involvement of this protein in regulating various cellular and viral genes, viral replication and cell growth.

Retinoblastoma-related protein pRb2/p130 and suppression of tumor growth in vivo.

BACKGROUND: The RB/p105 and p107 genes of the retinoblastoma family are tumor suppressor genes whose proteins are inactivated by interaction with T-antigen proteins encoded by polyomaviruses (e.g., simian virus 40 and human JC virus), which have been found to be highly tumorigenic in animals. A variety of indirect evidence suggests that another member of the retinoblastoma gene family, RB2/p130, is also a tumor suppressor gene. To investigate the putative tumor suppressor activity of RB2/p130 more directly, we utilized a tetracycline-regulated gene expression system to control expression of the encoded protein pRb2/p130 in JC virus-induced hamster brain tumor cells and to study the effects of pRb2/p130 on the growth of such tumor cells in nude mice. The ability of pRb2/p130 to interact with JC virus T antigen was also studied. METHODS: Northern blot hybridization analyses were performed on samples of total cellular RNA to measure RB2/p130 and beta-actin messenger RNA levels. Immunoprecipitation and western blot analyses were used to determine T-antigen and pRb2/p130 protein levels and to assess the phosphorylation status of these proteins. Tumor cells were injected subcutaneously into nude mice, and tumor growth, with or without induced expression of pRb2/p130, was monitored. RESULTS: Induction of pRb2/p130 expression brought about a 3.2-fold, or 69% (95% confidence interval = 64%-73%), reduction in final tumor mass in nude mice. We also demonstrated that JC virus T antigen binds hypophosphorylated pRb2/p130 and that stimulation of pRb2/p130 expression overcomes cellular transformation mediated by this antigen. CONCLUSION: Our findings support the hypothesis that RB2/p130 is a tumor suppressor gene.