ABSTRACT
Patient-derived xenografts (PDX) remain valuable models for understanding the biology and for developing novel therapeutics. To expand current PDX models of childhood leukemia, we have developed new PDX models from Hispanic patients, a subgroup with a poorer overall outcome. Of 117 primary leukemia samples obtained, successful engraftment and serial passage in mice were achieved in 82 samples (70%). Hispanic patient samples engrafted at a rate (51/73, 70%) that was similar to non-Hispanic patient samples (31/45, 70%). With a new algorithm to remove mouse contamination in multi-omics datasets including methylation data, we found PDX models faithfully reflected somatic mutations, copy-number alterations, RNA expression, gene fusions, whole-genome methylation patterns, and immunophenotypes found in primary tumor (PT) samples in the first 50 reported here. This cohort of characterized PDX childhood leukemias represents a valuable resource in that germline DNA sequencing has allowed the unambiguous determination of somatic mutations in both PT and PDX.
ABSTRACT
Subcutaneous patient-derived xenografts (PDXs) are an important tool for childhood cancer research. Here, we describe a resource of 68 early passage PDXs established from 65 pediatric solid tumor patients. Through genomic profiling of paired PDXs and patient tumors (PTs), we observe low mutational similarity in about 30% of the PT/PDX pairs. Clonal analysis in these pairs show an aggressive PT minor subclone seeds the major clone in the PDX. We show evidence that this subclone is more immunogenic and is likely suppressed by immune responses in the PT. These results suggest interplay between intratumoral heterogeneity and antitumor immunity may underlie the genetic disparity between PTs and PDXs. We further show that PDXs generally recapitulate PTs in copy number and transcriptomic profiles. Finally, we report a gene fusion LRPAP1-PDGFRA. In summary, we report a childhood cancer PDX resource and our study highlights the role of immune constraints on tumor evolution.
Subject(s)
Neoplasms , Animals , Child , Humans , Heterografts , Neoplasms/genetics , Neoplasms/pathology , Transcriptome/genetics , Mutation , Disease Models, Animal , Genomics/methods , Xenograft Model Antitumor AssaysABSTRACT
High levels of alcohol intake alter brain gene expression and can produce long-lasting effects. FK506-binding protein 51 (FKBP51) encoded by Fkbp5 is a physical and cellular stress response gene and has been associated with alcohol consumption and withdrawal severity. Fkbp5 has been previously linked to neurite outgrowth and hippocampal morphology, sex differences in stress response, and epigenetic modification. Presently, primary cultured Fkbp5 KO and WT mouse neurons were examined for neurite outgrowth and mitochondrial signal with and without alcohol. We found neurite specification differences between KO and WT; particularly, mesh-like morphology was observed after alcohol treatment and confirmed higher MitoTracker signal in cultured neurons of Fkbp5 KO compared to WT at both naive and alcohol-treated conditions. Brain regions that express FKBP51 protein were identified, and hippocampus was confirmed to possess a high level of expression. RNA-seq profiling was performed using the hippocampus of naïve or alcohol-injected (2 mg EtOH/Kg) male and female Fkbp5 KO and WT mice. Differentially expressed genes (DEGs) were identified between Fkbp5 KO and WT at baseline and following alcohol treatment, with female comparisons possessing a higher number of DEGs than male comparisons. Pathway analysis suggested that genes affecting calcium signaling, lipid metabolism, and axon guidance were differentially expressed at naïve condition between KO and WT. Alcohol treatment significantly affected pathways and enzymes involved in biosynthesis (Keto, serine, and glycine) and signaling (dopamine and insulin receptor), and neuroprotective role. Functions related to cell morphology, cell-to-cell signaling, lipid metabolism, injury response, and post-translational modification were significantly altered due to alcohol. In summary, Fkbp5 plays a critical role in the response to acute alcohol treatment by altering metabolism and signaling-related genes.
Subject(s)
Alcohol-Related Disorders , Ethanol , Female , Male , Animals , Mice , Ethanol/pharmacology , Lipid Metabolism , Injections , Alcohol Drinking , GlycineABSTRACT
Many chronic pain conditions show sex differences in their epidemiology. This could be attributed to sex-dependent differential expression of genes (DEGs) involved in nociceptive pathways, including sensory neurons. This study aimed to identify sex-dependent DEGs in estrous female versus male sensory neurons, which were prepared by using different approaches and ganglion types. RNA-seq on non-purified sensory neuronal preparations, such as whole dorsal root ganglion (DRG) and hindpaw tissues, revealed only a few sex-dependent DEGs. Sensory neuron purification increased numbers of sex-dependent DEGs. These DEG sets were substantially influenced by preparation approaches and ganglion types [DRG vs trigeminal ganglia (TG)]. Percoll-gradient enriched DRG and TG neuronal fractions produced distinct sex-dependent DEG groups. We next isolated a subset of sensory neurons by sorting DRG neurons back-labeled from paw and thigh muscle. These neurons have a unique sex-dependent DEG set, yet there is similarity in biological processes linked to these different groups of sex-dependent DEGs. Female-predominant DEGs in sensory neurons relate to inflammatory, synaptic transmission and extracellular matrix reorganization processes that could exacerbate neuro-inflammation severity, especially in TG. Male-selective DEGs were linked to oxidative phosphorylation and protein/molecule metabolism and production. Our findings catalog preparation-dependent sex differences in neuronal gene expressions in sensory ganglia.
Subject(s)
Sensory Receptor Cells/physiology , Transcriptome/genetics , Animals , Female , Ganglia, Spinal/physiology , Gene Expression/genetics , Inflammation/genetics , Male , Mice , Mice, Inbred C57BL , Oxidative Phosphorylation , Sex Characteristics , Trigeminal Ganglion/physiologyABSTRACT
INTRODUCTION: Comprehensive mRNA sequencing is a powerful tool for conducting unbiased, quantitative differential gene expression analysis. However, the reliability of these data is contingent on the extraction of high-quality RNA from samples. Preserving RNA integrity during extraction can be problematic, especially in tissues such as skin with dense, connective matrices and elevated ribonuclease expression. This is a major barrier to understanding the influences of altered gene expression in many preclinical pain models and clinical pain disorders where skin is the site of tissue injury. OBJECTIVE: This study developed and evaluated extraction protocols for skin and other tissues to maximize recovery of high-integrity RNA needed for quantitative mRNA sequencing. METHODS: Rodent and human tissue samples underwent one of the several different protocols that combined either RNA-stabilizing solution or snap-freezing with bead milling or cryosectioning. Indices of RNA integrity and purity were assessed for all samples. RESULTS: Extraction of high-integrity RNA is highly dependent on the methods used. Bead-milling skin collected in RNA-stabilizing solution resulted in extensive RNA degradation. Snap-freezing in liquid nitrogen was required for skin and highly preferable for other tissues. Skin also required cryosectioning to achieve effective penetration of RNA-stabilizing solution to preserve RNA integrity, whereas bead milling could be used instead with other tissues. Each method was reproducible across multiple experimenters. Electrophoretic anomalies that skewed RNA integrity value assignment required manual correction and often resulted in score reduction. CONCLUSION: To achieve the potential of quantitative differential gene expression analysis requires verification of tissue-dependent extraction methods that yield high-integrity RNA.
ABSTRACT
Oncoprotein staphylococcal nuclease and tudor domain containing 1 (SND1) regulates gene expression at a posttranscriptional level in multiple cancers, including hepatocellular carcinoma (HCC). Staphylococcal nuclease (SN) domains of SND1 function as a ribonuclease (RNase), and the tudor domain facilitates protein-oligonucleotide interaction. In the present study, we aimed to identify RNA interactome of SND1 to obtain enhanced insights into gene regulation by SND1. RNA interactome was identified by immunoprecipitation (IP) of RNA using anti-SND1 antibody from human HCC cells followed by RNA immunoprecipitation sequencing (RIP-Seq). Among RNA species that showed more than 10-fold enrichment over the control, we focused on the tumor suppressor protein tyrosine phosphatase nonreceptor type 23 (PTPN23) because its regulation by SND1 and its role in HCC are not known. PTPN23 levels were down-regulated in human HCC cells versus normal hepatocytes and in human HCC tissues versus normal adjacent liver, as revealed by immunohistochemistry. In human HCC cells, knocking down SND1 increased and overexpression of SND1 decreased PTPN23 protein. RNA binding and degradation assays revealed that SND1 binds to and degrades the 3'-untranslated region (UTR) of PTPN23 messenger RNA (mRNA). Tetracycline-inducible PTPN23 overexpression in human HCC cells resulted in significant inhibition in proliferation, migration, and invasion and in vivo tumorigenesis. PTPN23 induction caused inhibition in activation of tyrosine-protein kinase Met (c-Met), epidermal growth factor receptor (EGFR), Src, and focal adhesion kinase (FAK), suggesting that, as a putative phosphatase, PTPN23 inhibits activation of these oncogenic kinases. Conclusion: PTPN23 is a novel target of SND1, and our findings identify PTPN23 as a unique tumor suppressor for HCC. PTPN23 might function as a homeostatic regulator of multiple kinases, restraining their activation.
ABSTRACT
Humans show sex differences related to alcohol use disorders (AUD). Animal model research has the potential to provide important insight into how sex differences affect alcohol consumption, particularly because female animals frequently drink more than males. In previous work, inbred strains of the selectively bred alcohol-preferring (P) and non-preferring (NP) rat lines revealed a highly significant quantitative trait locus (QTL) on rat chromosome 4, with a logarithm of the odds score of 9.2 for alcohol consumption. Recently, interval-specific congenic strains (ISCS) were developed by backcrossing the congenic P.NP line to inbred P (iP) rats to further refine the chromosome 4 QTL region. Two ISCS sub-strains, ISCS-A and ISCS-B, were obtained with a narrowed QTL, where the smallest region of overlap consisted of 8.9 Mb in ISCS-B. Interestingly, we found that females from both ISCS lines consumed significantly less alcohol than female iP controls (p < 0.05), while no differences in alcohol consumption were observed between male ISCS and iP controls. RNA-sequencing was performed on the nucleus accumbens of alcohol-naïve female ISCS-B and iP rats, which revealed differentially expressed genes (DEG) with greater than 2-fold change and that were functionally relevant to behavior. These DEGs included down-regulation of Oxt, Asb4, Gabre, Gabrq, Chat, Slc5a7, Slc18a8, Slc10a4, and Ngfr, and up-regulation of Ttr, Msln, Mpzl2, Wnt6, Slc17a7, Aldh1a2, and Gstm2. Pathway analysis identified significant alterations in gene networks controlling nervous system development and function, as well as cell signaling, GABA and serotonin receptor signaling and G-protein coupled receptor signaling. In addition, ß-estradiol was identified as the most significant upstream regulator. The expression levels of estrogen-responsive genes that mapped to the QTL interval and have been previously associated with alcohol consumption were measured using RT-qPCR. We found that expression of the Adcyap1r1 gene, encoding the pituitary adenylate cyclase-activating polypeptide type 1 (PAC1) receptor, was upregulated in female ISCS-B compared to female iP controls, while no differences were exhibited in males. In addition, sequence variants in the Adcyap1r1 promoter region showed a differential response to estrogen stimulation in vitro. These findings demonstrate that rat chromosome 4 QTL contains genetic variants that respond to estrogen and are associated with female alcohol consumption.
ABSTRACT
Antibody responses are accomplished through several critical B cell-intrinsic processes, including somatic hypermutation (SHM), class-switch DNA recombination (CSR), and plasma cell differentiation. In recent years, epigenetic modifications or factors, such as histone deacetylation and microRNAs (miRNAs), have been shown to interact with B-cell genetic programs to shape antibody responses, while the dysfunction of epigenetic factors has been found to lead to autoantibody responses. Analyzing genome-wide miRNA and mRNA expression in B cells in response to epigenetic modulators is important for understanding the epigenetic regulation of B-cell function and antibody response. Here, we demonstrate a protocol for inducing B cells to undergo CSR and plasma cell differentiation, treating these B cells with histone deacetylase (HDAC) inhibitors (HDIs), and analyzing mRNA and microRNA expression. In this protocol, we directly analyze complementary DNA (cDNA) sequences using next-generation mRNA sequencing (mRNA-seq) and miRNA-seq technologies, mapping of the sequencing reads to the genome, and quantitative reverse transcription (qRT)-PCR. With these approaches, we have defined that, in B cells induced to undergo CSR and plasma cell differentiation, HDI, an epigenetic regulator, selectively modulates miRNA and mRNA expression and alters CSR and plasma cell differentiation.
Subject(s)
B-Lymphocytes/immunology , Genome-Wide Association Study/methods , Histone Deacetylase Inhibitors/pharmacology , MicroRNAs/metabolism , RNA, Messenger/metabolism , Animals , Cell Differentiation/physiology , Humans , Mice , MicroRNAs/genetics , RNA, Messenger/genetics , Recombination, GeneticABSTRACT
Activation of IGF signaling is a major oncogenic event in diverse cancers, including hepatocellular carcinoma (HCC). In this setting, the insulin-like growth factor binding protein IGFBP7 inhibits IGF signaling by binding the IGF1 receptor (IGF1R), functioning as a candidate tumor suppressor. IGFBP7 abrogates tumors by inhibiting angiogenesis and inducing cancer-specific senescence and apoptosis. Here, we report that Igfbp7-deficient mice exhibit constitutively active IGF signaling, presenting with proinflammatory and immunosuppressive microenvironments and spontaneous liver and lung tumors occurring with increased incidence in carcinogen-treated subjects. Igfbp7 deletion increased proliferation and decreased senescence of hepatocytes and mouse embryonic fibroblasts, effects that were blocked by treatment with IGF1 receptor inhibitor. Significant inhibition of genes regulating immune surveillance was observed in Igfbp7-/- murine livers, which was associated with a marked inhibition in antigen cross-presentation by Igfbp7-/- dendritic cells. Conversely, IGFBP7 overexpression inhibited growth of HCC cells in syngeneic immunocompetent mice. Depletion of CD4+ or CD8+ T lymphocytes abolished this growth inhibition, identifying it as an immune-mediated response. Our findings define an immune component of the pleiotropic mechanisms through which IGFBP7 suppresses HCC. Furthermore, they offer a genetically based preclinical proof of concept for IGFBP7 as a therapeutic target for immune management of HCC. Cancer Res; 77(15); 4014-25. ©2017 AACR.
Subject(s)
Carcinoma, Hepatocellular/pathology , Insulin-Like Growth Factor Binding Proteins/deficiency , Liver Neoplasms/pathology , Animals , Blotting, Western , Carcinoma, Hepatocellular/genetics , Carcinoma, Hepatocellular/immunology , Disease Models, Animal , Flow Cytometry , Fluorescent Antibody Technique , Immunohistochemistry , Insulin-Like Growth Factor Binding Proteins/genetics , Insulin-Like Growth Factor Binding Proteins/immunology , Liver Neoplasms/genetics , Liver Neoplasms/immunology , Mice , Mice, Inbred C57BL , Mice, Knockout , Mice, SCID , Real-Time Polymerase Chain ReactionABSTRACT
Methylation is one of the essential epigenetic modifications to the DNA, which is responsible for the precise regulation of genes required for stable development and differentiation of different tissue types. Dysregulation of this process is often the hallmark of various diseases like cancer. Here, we outline one of the recent sequencing techniques, Methyl-Binding DNA Capture sequencing (MBDCap-seq), used to quantify methylation in various normal and disease tissues for large patient cohorts. We describe a detailed protocol of this affinity enrichment approach along with a bioinformatics pipeline to achieve optimal quantification. This technique has been used to sequence hundreds of patients across various cancer types as a part of the 1,000 methylome project (Cancer Methylome System).
Subject(s)
Computational Biology/methods , Epigenesis, Genetic , Sequence Analysis, DNA , DNA , DNA Methylation , HumansABSTRACT
UNLABELLED: Astrocyte elevated gene-1 (AEG-1) and c-Myc are overexpressed in human hepatocellular carcinoma (HCC) functioning as oncogenes. AEG-1 is transcriptionally regulated by c-Myc, and AEG-1 itself induces c-Myc by activating the Wnt/ß-catenin-signaling pathway. We now document the cooperation of AEG-1 and c-Myc in promoting hepatocarcinogenesis by analyzing hepatocyte-specific transgenic mice expressing either AEG-1 (albumin [Alb]/AEG-1), c-Myc (Alb/c-Myc), or both (Alb/AEG-1/c-Myc). Wild-type and Alb/AEG-1 mice did not develop spontaneous HCC. Alb/c-Myc mice developed spontaneous HCC without distant metastasis, whereas Alb/AEG-1/c-Myc mice developed highly aggressive HCC with frank metastasis to the lungs. Induction of carcinogenesis by N-nitrosodiethylamine significantly accelerated the kinetics of tumor formation in all groups. However, in Alb/AEG-1/c-Myc, the effect was markedly pronounced with lung metastasis. In vitro analysis showed that Alb/AEG-1/c-Myc hepatocytes acquired increased proliferation and transformative potential with sustained activation of prosurvival and epithelial-mesenchymal transition-signaling pathways. RNA-sequencing analysis identified a unique gene signature in livers of Alb/AEG-1/c-Myc mice that was not observed when either AEG-1 or c-Myc was overexpressed. Specifically, Alb/AEG-1/c-Myc mice overexpressed maternally imprinted noncoding RNAs (ncRNAs), such as Rian, Meg-3, and Mirg, which are implicated in hepatocarcinogenesis. Knocking down these ncRNAs significantly inhibited proliferation and invasion by Alb/AEG-1/c-Myc hepatocytes. CONCLUSION: Our studies reveal a novel cooperative oncogenic effect of AEG-1 and c-Myc that might explain the mechanism of aggressive HCC. Alb/AEG-1/c-Myc mice provide a useful model to understand the molecular mechanism of cooperation between these two oncogenes and other molecules involved in hepatocarcinogenesis. This model might also be of use for evaluating novel therapeutic strategies targeting HCC.
Subject(s)
Liver Neoplasms, Experimental/etiology , Membrane Proteins/physiology , Proto-Oncogene Proteins c-myc/physiology , Albumins/analysis , Animals , Carcinogenesis , Cells, Cultured , Epithelial-Mesenchymal Transition , Liver Neoplasms, Experimental/pathology , Lung Neoplasms/secondary , Membrane Proteins/analysis , Mice , Mice, Transgenic , Proto-Oncogene Proteins c-myc/analysis , RNA-Binding ProteinsABSTRACT
Workload Management System for Nursing (WMSN) is a core Army Medical Department business system that has provided near real-time, comprehensive nursing workload and manpower data for decision making at all levels for over 25 years. The Army Manpower Requirements and Documentation Agency populates data from WMSN into the Manpower Staffing Standards System (Inpatient module within Automated Staffing Assessment Model). The current system, Workload Management System for Nursing Internet (WMSNi), is an interim solution that requires additional functionalities for modernization and integration at the enterprise level. The expanding missions and approved requirements for WMSNi support strategic initiatives on the Army Medical Command balanced scorecard and require continued sustainment for multiple personnel and manpower business processes for both inpatient and outpatient nursing care. This system is currently being leveraged by the TRICARE Management Activity as an interim multiservice solution, and is being used at 24 Army medical treatment facilities. The evidenced-based information provided to Army decision makers through the methods used in the WMSNi will be essential across the Army Medical Command throughout the system's life cycle.
Subject(s)
Military Nursing , Outcome Assessment, Health Care , Personnel Staffing and Scheduling , Workload , Decision Making , Feedback , Humans , United StatesABSTRACT
Since the beginning of the Overseas Contingency Operation, more than 45,000 ill and wounded service members have been evacuated from the battlefield to Landstuhl Regional Medical Center (LRMC) in western Europe. LRMC is a stopover for these service members, where they are further assessed, treated, and stabilized before they return to the United States. This process requires coordination between different military services, health care teams, and modes of transportation. These processes can be complicated given the severity of the wounded. Nurses at LRMC have learned how to streamline services, providing efficient, comprehensive care for wounded service members and their families.
Subject(s)
Attitude of Health Personnel , Job Satisfaction , Military Nursing/organization & administration , Nursing Staff, Hospital/psychology , Adaptation, Psychological , Afghan Campaign 2001- , Air Ambulances , Burnout, Professional/psychology , Clinical Competence , Germany , Hospitals, Military , Humans , Iraq War, 2003-2011 , Military Nursing/education , Military Personnel , Nurse's Role/psychology , Nursing Methodology Research , Nursing Staff, Hospital/education , Nursing Staff, Hospital/organization & administration , Total Quality Management , Transportation of Patients , Trauma Centers , United States , Wounds and Injuries/nursingABSTRACT
PURPOSE: SEMA3B and SEMA3F are 2 closely related genes lying 80 kb apart on chromosome 3 that have been shown to suppress tumor formation in vivo and in vitro. Each gene has a single nucleotide polymorphism that results in a nonsynonymous coding change, rs2071203 (SEMA3B) and rs1046956 (SEMA3F), as well as noncoding single nucleotide polymorphisms. MATERIALS AND METHODS: We performed a case-control study of 789 prostate cancer cases and 907 controls from 3 races/ethnicities to determine possible associations of 10 variants with prostate cancer risk or prognosis. RESULTS: The risk of prostate cancer increased more than 2-fold in Hispanic men with TT alleles at rs2071203 in SEMA3B and with CC alleles for rs2072054 at the 5' end of SEMA3F (OR 2.13, 95% CI 1.12-4.04, p = 0.02 and OR 2.55, 95% CI 1.34-4.84, p = 0.0045, respectively). These 2 single nucleotide polymorphisms were also associated with a poor prognosis in Hispanic men (2.71 and 3.48-fold increased risk). A frequent G-C-G-G-A-T-C-C-T-G haplotype encompassing 10 SNPs was associated with an increased risk of prostate cancer and poor prognosis in Hispanic samples (OR 2.72, 95% CI 1.20-6.12, p = 0.016 and OR 3.32, 95% CI 1.21-9.10, p = 0.02). In nonHispanic white men the T-C-G-A-A-T-C-C haplotype was associated with a high Gleason score (OR 1.44, 95% CI 1.06-1.96, p = 0.021). CONCLUSIONS: These data indicate that polymorphisms in SEMA3B and SEMA3F are associated with prostate cancer risk and poor prognosis in Hispanic and nonHispanic white men.
Subject(s)
Black or African American , Hispanic or Latino , Membrane Glycoproteins/genetics , Membrane Proteins/genetics , Nerve Tissue Proteins/genetics , Polymorphism, Single Nucleotide , Prostatic Neoplasms/genetics , Semaphorins/genetics , White People , Adult , Aged , Aged, 80 and over , Case-Control Studies , Humans , Male , Middle Aged , Prognosis , Risk FactorsABSTRACT
Prostate cancer is the second leading cause of cancer deaths among American men. The loss of Y chromosome has been frequently observed in primary prostate cancer as well as other types of cancer. Earlier, we showed that introduction of the human Y chromosome suppresses the in vivo tumorigenicity of the prostate cancer cell line PC-3. To further characterize the Y chromosome, we have developed a high-density bacterial artificial chromosome (BAC) microarray containing 178 BAC clones from the human Y chromosome. BAC microarray was used for array comparative genomic hybridization on prostate cancer samples and cell lines. The most prominent observation on prostate cancer specimens was a deletion at Yp11.2 containing the TSPY tandem gene array. Out of 36 primary prostate tumors analyzed, 16 (44.4%) samples exhibited loss of TSPY gene copies. Notably, we observed association between the number of TSPY copies in the blood and the incidence of prostate cancer. Moreover, PC-3 hybrids with an intact Yp11.2 did not grow tumors in nude mice, whereas PC-3 hybrids with a deletion at Yp11.2 grew tumors in nude mice.
Subject(s)
Cell Cycle Proteins/genetics , Chromosomes, Human, Y/genetics , Prostatic Neoplasms/genetics , Aged , Cell Line, Tumor , Gene Dosage , Humans , Male , Middle Aged , Multigene Family , Neoplasm Staging , Nucleic Acid Hybridization , Oligonucleotide Array Sequence Analysis/methods , Oligonucleotide Array Sequence Analysis/standards , Prostatic Neoplasms/pathology , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
The loss of the Y chromosome is a frequent numerical chromosomal abnormality observed in human prostate cancer. In cancer, loss of specific genetic material frequently accompanies simultaneous inactivation of tumor suppressor genes. It is not known whether the Y chromosome harbors such genes. To address the role of genes on the Y chromosome in human prostate cancer, we transferred a tagged Y chromosome into PC-3, a human prostate cancer cell line lacking a Y chromosome. A human Y chromosome was tagged with the hisD gene and transferred to PC-3 by microcell-mediated chromosome transfer. Tumorigenicity of these PC-3 hybrids was tested in vivo and in vitro, and the results were compared with those of the polymerase chain reaction analyses conducted on the PC-3 hybrids using Y chromosome-specific markers. Among 60 mice injected with 12 different PC-3 hybrids (five mice per hybrid), tumor growth was apparent in only one mouse, whereas tumors grew in all mice injected with the parental PC-3 cells. An in vitro assay showed that the Y chromosome did not suppress anchorage-independent growth of PC-3 cells. We found that addition of the Y chromosome suppressed tumor formation by PC-3 in athymic nude mice, and that this block of tumorigenesis was independent of the in vitro growth properties of the cells. This observation suggests the presence of a gene important for prostate tumorigenesis on the Y chromosome.