Phenotypic and cytogenetic characterization of a cell line derived from primary prostatic carcinoma

Experimental in vitro, ex vivo and in vivo models in prostate cancer research

Androgen deprivation therapy has a central role in the treatment of advanced prostate cancer, often causing initial tumour remission before increasing independence from signal transduction mechanisms of the androgen receptor and then eventual disease progression. Novel treatment approaches are urgently needed, but only a fraction of promising drug candidates from the laboratory will eventually reach clinical approval, highlighting the demand for critical assessment of current preclinical models. Such models include standard, genetically modified and patient-derived cell lines, spheroid and organoid culture models, scaffold and hydrogel cultures, tissue slices, tumour xenograft models, patient-derived xenograft and circulating tumour cell eXplant models as well as transgenic and knockout mouse models. These models need to account for inter-patient and intra-patient heterogeneity, the acquisition of primary or secondary resistance, the interaction of tumour cells with their microenvironment, which make crucial contributions to tumour progression and resistance, as well as the effects of the 3D tissue network on drug penetration, bioavailability and efficacy.

Extrachromosomal Circular DNA: A New Target in Cancer

Genomic instability and amplification are intrinsically important traits determining the development and heterogeneity of tumors. The role of extrachromosomal circular DNA (eccDNA) in tumors has recently been highlighted. EccDNAs are unique genetic materials located off the chromosomal DNA. They have been detected in a variety of tumors. This review analyzes the mechanisms involved in the formation of eccDNAs and their genetic characteristics. In addition, the high-copy number and transcriptional levels of oncogenes located in eccDNA molecules contribute to the acceleration of tumor evolution and drug resistance and drive the development of genetic heterogeneity. Understanding the specific genomic forms of eccDNAs and characterizing their potential functions will provide new strategies for tumor therapy. Further research may yield new targets and molecular markers for the early diagnosis and treatment of human cancer.

Application of Prostate Cancer Models for Preclinical Study: Advantages and Limitations of Cell Lines, Patient-Derived Xenografts, and Three-Dimensional Culture of Patient-Derived Cells

Various preclinical models have been developed to clarify the pathophysiology of prostate cancer (PCa). Traditional PCa cell lines from clinical metastatic lesions, as exemplified by DU-145, PC-3, and LNCaP cells, are useful tools to define mechanisms underlying tumorigenesis and drug resistance. Cell line-based experiments, however, have limitations for preclinical studies because those cells are basically adapted to 2-dimensional monolayer culture conditions, in which the majority of primary PCa cells cannot survive. Recent tissue engineering enables generation of PCa patient-derived xenografts (PDXs) from both primary and metastatic lesions. Compared with fresh PCa tissue transplantation in athymic mice, co-injection of PCa tissues with extracellular matrix in highly immunodeficient mice has remarkably improved the success rate of PDX generation. PDX models have advantages to appropriately recapitulate the molecular diversity, cellular heterogeneity, and histology of original patient tumors. In contrast to PDX models, patient-derived organoid and spheroid PCa models in 3-dimensional culture are more feasible tools for in vitro studies for retaining the characteristics of patient tumors. In this article, we review PCa preclinical model cell lines and their sublines, PDXs, and patient-derived organoid and spheroid models. These PCa models will be applied to the development of new strategies for cancer precision medicine.

The Arf-like GTPase Arl8b is essential for three-dimensional invasive growth of prostate cancer in vitro and xenograft formation and growth in vivo

Cancer is a multistep process that requires cells to respond appropriately to the tumor microenvironment, both in early proliferative stages and in later invasive disease. Arl8b is a lysosome localized Arf-like GTPase that controls the spatial distribution of lysosomes via recruitment of kinesin motors. Common features of the tumor microenvironment such as acidic extracellular pH and various growthfactors stimulate lysosome trafficking to the cell periphery (anterograde), which is critical for tumor invasion by facilitating the release of lysosomal proteases to promote matrix remodeling. Herein we report for the first time that Arl8b regulates anterograde lysosome trafficking in response to hepatocyte growth factor, epidermal growth factor, and acidic extracellular pH. Depletion of Arl8b results in juxtanuclear lysosome aggregation, and this effect corresponds with both diminished invasive growth and proteolytic extracellular matrix degradation in a three-dimensional model of prostate cancer. Strikingly, we found that depletion of Arl8b abolishes the ability of prostate cancer cells to establish subcutaneous xenografts in mice. We present evidence that Arl8b facilitates lipid hydrolysis to maintain efficient metabolism for a proliferative capacity in low nutrient environments, suggesting a likely explanation for the complete inability of Arl8b-depleted tumor cells to grow in vivo. In conclusion, we have identified two mechanisms by which Arl8b regulates cancer progression: 1) through lysosome positioning and protease release leading to an invasive phenotype and 2) through control of lipid metabolism to support cellular proliferation. These novel roles highlight that Arl8b is a potential target for the development of novel anti-cancer therapeutics.

The histone deacetylase inhibitor cambinol prevents acidic pHe-induced anterograde lysosome trafficking independently of sirtuin activity

Common features of the solid tumor microenvironment, such as acidic extracellular pH and growth factors, are known to induce the redistribution of lysosomes from a perinuclear region to a position near the plasma membrane. Lysosome/plasma membrane juxtaposition facilitates invasion by allowing for the release of lysosomal proteases, including cathepsin B, which contribute to matrix degradation. In this study we identified the sirtuin 1/sirtuin 2 (SIRT1/2) inhibitor cambinol acts as a drug that inhibits lysosome redistribution and tumor invasion. Treatment of cells with cambinol resulted in a juxtanuclear lysosome aggregation (JLA) similar to that seen upon treatment with the PPARγ agonist, troglitazone (Tro). Like Tro, cambinol required the activity of ERK1/2 in order to induce this lysosome clustering phenotype. However, cambinol did not require the activity of Rab7, suggesting that this drug causes JLA by a mechanism different from what is known for Tro. Additionally, cambinol-induced JLA was not a result of autophagy induction. Further investigation revealed that cambinol triggered JLA independently of its activity as a SIRT1/2 inhibitor, suggesting that this drug could have effects in addition to SIRT1/2 inhibition that could be developed into a novel anti-cancer therapy.

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Cambinol prevents acidic pH_e-induced anterograde lysosome trafficking.

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Cambinol-mediated lysosome aggregation is not dependent on sirtuin activity.

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ERK1/2 activity is necessary for cambinol-driven juxtanuclear lysosome aggregation.

Acid ceramidase-mediated production of sphingosine 1-phosphate promotes prostate cancer invasion through upregulation of cathepsin B

Invasiveness is one of the key features of aggressive prostate cancer; however, our understanding of the precise mechanisms effecting invasion remains limited. The ceramide hydrolyzing enzyme acid ceramidase (AC), overexpressed in most prostate tumors, causes an aggressive and invasive phenotype through downstream effectors that have not yet been well characterized. Here, we demonstrate that AC, through generation of sphingosine-1-phosphate (S1P), promotes Ets1 nuclear expression and binding to the promoter region of matrix-degrading protease cathepsin B. Through confocal microscopy and flow cytometry, we found that AC overexpression promotes pericellular localization of cathepsin B and its translocation to the outer leaflet of the cell membrane. AC overexpressing cells have an increased abundance of cathepsin B-enriched invasive structures and enhanced ability to invade through a collagen matrix, but not in the presence of an inhibitor of cathepsin B. In human prostate tissues, AC and cathepsin B overexpression were strongly associated and may relate to poor outcome. These results demonstrate a novel pathway by which AC, through S1P, promotes an invasive phenotype in prostate cancer by causing overexpression and secretion of cathepsin B through activation and nuclear expression of Ets1. As prostate cancer prognosis is dramatically worse when invasion has occurred, this study provides critical insight into the progression toward lethal prostate cancer.

Autophagy is increased in prostate cancer cells overexpressing acid ceramidase and enhances resistance to C6 ceramide

Acid ceramidase (AC) overexpression has been observed in prostate cancer cell lines and primary tumors, and contributes to resistance to chemotherapy and radiation. The consequence of AC overexpression is the ability to convert ceramide, which is often produced as a proapoptotic response to stress, to sphingosine, which can then be converted to the prosurvival molecule sphingosine-1-phosphate. In addition to their ability to metabolize ceramide produced in response to stress, we show here that prostate cancer cell lines overexpressing AC also have increased lysosomal density and increased levels of autophagy. Furthermore, pretreatment with 3-methyladenine restores sensitivity of these cells to treatment with C(6) ceramide. We also observed increased expression of the lysosomal stabilizing protein KIF5B and increased sensitivity to the lysosomotropic agent LCL385. Thus, we conclude that AC overexpression increases autophagy in prostate cancer cells, and that increased autophagy enhances resistance to ceramide.

Endothelin-1 inhibits apoptosis in prostate cancer

Endothelin-1 (ET-1), produced by the prostate epithelia, likely plays an important role in the progression of prostate cancer. ET-1 can bind two receptor subtypes; generally, binding of the endothelin receptor A (ET(A)) induces a survival pathway, whereas binding of the endothelin receptor B (ET(B)) mediates clearance of circulating ET-1 as well as promotes apoptosis. In prostate carcinoma, hypermethylation of the ET(B) promoter results in repression of ET(B) expression, thereby eliminating the negative growth response that ET-1 binding elicits through this receptor. Therefore, activation of ET(A) exclusively provides a pathway for survival advantage. Our current studies examine the mechanisms by which activation of the ET(A) may allow growth/survival. ET-1 treatment of prostate tumor cells significantly decreased paclitaxel-induced apoptosis through activation of the ET(A) subtype. The anti-apoptotic effects of ET-1 are mediated, at least in part, through the Bcl-2 family. Although no significant changes in Bcl-2 expression occurred with ET-1 treatment, the pro-apoptotic family members Bad, Bax, and Bak all decreased significantly. Further analysis of the survival pathway demonstrated that phosphorylation of Akt occurs with ET-1 treatment in a time- and dose-dependent manner through phosphatidyinositol 3-kinase activation. These data support the combination of ET(A) antagonists and apoptosis-inducing therapies for prostate cancer treatment.

CELL LINES USED IN PROSTATE CANCER RESEARCH: A COMPENDIUM OF OLD AND NEW LINES—PART 1

PURPOSE

This is part 1 of a 2-part review. Research into the molecular mechanisms underlying the various aspects of prostate cancer (PCa) requires the use of in vivo and in vitro model systems. In the last few years many new cell lines have been established by investigators from primary tissue sources and clonal derivatives of previously established lines. Therefore, the purpose of this 2-part review is to catalogue the current human cell lines developed for PCa research, as reported in the literature. Part 1 includes tissue culture cell lines derived from metastases, primary tumors and nonadenocarcinomas that were established without the use of transgenes. It also includes a section describing lines that have been contaminated with other lines, shown not to be of prostatic origin or whose identity is being challenged.

MATERIALS AND METHODS

Prostate cell lines included in this review were identified by extensive searching of the literature using several strategies, including PubMed searches and book chapter reviews.

RESULTS

In total we describe the derivation, phenotype, genotype and characterization of molecular markers expressed by approximately 200 lines and sublines used in PCa research, including those derived from primary tumors, metastases and normal prostate tissue. We paid particular attention to the expression of prostate specific antigen, androgen receptor, cytokeratins and other molecular markers used to indicate the status of PCa and the prostatic lineage of a given line. In an attempt to provide PCa researchers with a resource of information regarding new and established cell lines we have also created an online database of these PCa cell lines freely accessible via the World Wide Web at http://www.CaPCellLines.com. The web based interface allows researchers to peruse and print information regarding cell lines, add new cell lines and update or add new information regarding established cell lines.

CONCLUSIONS

This compendium of cell lines currently used in PCa research combined with access to our on-line database provides researchers with a continually updated and valuable resource for investigating the molecular mechanisms of PCa.

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

Increased fatty acid synthase expression and activity during progression of prostate cancer in the TRAMP model

BACKGROUND

Fatty acid synthase (FAS) is the major enzyme required to convert carbohydrates to fatty acids. Recent evidence suggests that FAS activity is essential for prostate cancer growth and survival, since blocking the enzyme activity results in cell death. In this study, the role of FAS up-regulation during prostate tumor progression in the transgenic adenocarcinoma of mouse prostate (TRAMP) model was investigated. Sensitivity to FAS anti-metabolites was also analyzed in TRAMP prostate tumor cells and tissue to determine therapeutic potential of FAS inhibition in the treatment of prostate cancer.

METHODS

FAS expression was evaluated by immunohistochemistry of TRAMP tissues, including primary and metastatic lesions in mice of varying ages. FAS pathway activity was studied in vitro using TRAMP-derived cell lines and in vivo in TRAMP tissues. The sensitivity of TRAMP cell lines and tissues to the antimetabolite drugs (2R,3S)-2,3-epoxy-4-oxo-7,10-trans, transdodecadienamide (cerulenin) and C-75, which target FAS, was determined by FAS antimetabolite inhibition of 14C-acetate conversion to fatty acids, cell growth inhibition, and apoptosis analyses.

RESULTS

High FAS expression and activity in the TRAMP mouse prostate was evident at 12 weeks of age compared with nontransgenic littermates and further increased with age, tumor progression, and in metastatic lesions. FAS pathway inhibition resulted in a dose-dependent reduction in cell survival and decreased enzyme activity in these models.

CONCLUSIONS

These data suggest that the up-regulation of FAS expression play a role in tumorigenesis of the prostate in the TRAMP model and hence can provide valuable insight into human prostate cancer. Given the response of tumor cells to FAS antimetabolites, FAS may serve as a novel target for prostate cancer therapy.

Molecular characterization of human prostate carcinoma cell lines

BACKGROUND

This study presents a comprehensive survey and characterization of available prostate carcinoma cell lines, most of which have been widely used but are incompletely characterized.

METHODS

A total of 21 cell lines were investigated, including three "classical" (DU 145, LNCaP, and PC-3) and 18 "non-classical" lines (1013L, 22Rv1, ALVA-55, ALVA-101, ARCaP, CWR-R1, DuCaP, DuPro-1, LAPC-4, MDA PCa 1, MDA PCa 2a, MDA PCa 2b, NCI-H660, PC-346C, PC-93, PSK-1, UM-SCP-1, and VCaP). Cytogenetics, DNA profiling, expression of basal, luminal, and neuroendocrine differentiation markers, and mutation analyses of the TP53 and androgen receptor (AR) genes were performed.

RESULTS

Based on cytogenetics and DNA profiling analyses, out of the 18 "non-classical" lines, six were confirmed to be unique, eight (in four pairs) were confirmed to be related in origin, and four lines were identified as cross-contaminants. Of this latter group, PC-93 was found to be a derivative of HeLa, whereas DuPro-1, ALVA-55, and ALVA-101 were derivatives of PC-3. The 17 genuine prostate cell lines expressed keratin 8 (K8) and K18. Nine showed AR expression, of which five harbored mutations in the AR gene. Prostate-specific antigen and DD3 were exclusively detected in AR expressing cell lines. Seven lines expressed the basal cell marker K5, three of these lines showed co-expression of AR.

CONCLUSIONS

This study defines a collection of 17 genuine prostate carcinoma cell lines. This collection, although small, constitutes a variety of different types and stages of prostate cancer, while it also partly reflects the heterogeneous nature of this malignancy.

Promoter methylation of TSLC1 and tumor suppression by its gene product in human prostate cancer

We recently identified TSLC1, a tumor suppressor gene in human lung cancer. Gene silencing by promoter methylation has been observed frequently in adenocarcinoma of the lung, liver, and pancreas. Here, we demonstrate that TSLC1 expression is also absent or markedly reduced in 3 of 4 prostate cancer cell lines. Promoter sequences of TSLC1 were heavily methylated in PPC-1 cells that lacked TSLC1 expression, supporting the idea that promoter methylation is strongly correlated with complete loss of gene expression. Promoter sequences of TSLC1 were also methylated significantly in 7 of 22 (32%) primary prostate cancers. Hypermethylation of the promoter occurred not only in advanced tumors, but also in relatively early-stage tumors. Restoration of TSLC1 expression substantially suppressed tumor formation of PPC-1 cells in nude mice. These findings indicate that alteration of TSLC1 is involved in prostate cancer.

Karyotypic similarity identified by multiplex-FISH relates four prostate adenocarcinoma cell lines: PC-3, PPC-1, ALVA-31, and ALVA-41

Recently developed molecular cytogenetic techniques for karyotyping are providing new and important insights regarding the chromosomal changes that occur in solid tumors. We used multiplex-FISH to analyze four adenocarcinoma cell lines, PC-3, PPC-1, ALVA-31, and ALVA-41, in which the characterization of a large number of rearranged chromosomes was partially or substantially inconclusive by G-banding. Although the original descriptions of these lines depict them as distinct entities established from different patients, this study demonstrates that these four lines share numerous, highly rearranged chromosomes, strongly supporting the conclusion that they are derived from the same patient material. Our analysis indicates that PPC-1, ALVA-31, and ALVA-41 were derived from PC-3 through mechanisms involving clonal progression represented by sequential changes and clonal diversion represented by differing patterns of changes. Extensive cellular heterogeneity was detected in all four lines, and most rearrangements included segments derived from multiple chromosomes. Each line also showed a set of unique derivative chromosomes. However, a limited number of metaphase cells (approximately 10) was analyzed for each line, and numerous single-cell abnormalities were detected in all of them. Therefore, it is plausible that the number of clonal, shared, and/or unique rearrangements has been underestimated. These cell lines have been utilized as models for understanding the biology of prostate cancer and reportedly differ in their cell physiology. Rather than detracting from their value, a complete understanding of the interrelationships of these lines to one another may provide the opportunity to define the molecular changes that have led to their individual malignant phenotypes.

An apoptosis signaling pathway induced by the death domain of FADD selectively kills normal but not cancerous prostate epithelial cells

The adaptor protein FADD directly, or indirectly via another adaptor called TRADD, recruits caspase 8 to death receptors of the tumor necrosis factor receptor family. Consequentially, a dominant-negative mutant (FADD-DN, which consists only of the FADD death domain) that binds to receptors but cannot recruit caspase 8 has been widely used to inhibit apoptosis by various stimuli that work via death receptors. Here, we show that FADD-DN also has another cell type- and cancer-dependent activity because it induces apoptosis of normal human prostate epithelial cells but not normal prostate stromal cells or prostate cancer cells. This activity is independent of FADD-DN's ability to bind to three known interacting proteins, Fas, TRADD or RIP suggesting that it is distinct from FADD's functions at activated death receptors. FADD-DN induces caspase activation in normal epithelial cells as demonstrated using a Fluorescence Resonance Energy Transfer assay that measures caspase activity in individual living cells. However, caspase-independent pathways are also implicated in FADD-DN-induced apoptosis because caspase inhibitors were inefficient at preventing prostate cell death. Therefore, the death domain of FADD has a previously unrecognized role in cell survival that is epithelial-specific and defective in cancer cells. This FADD-dependent signaling pathway may be important in prostate carcinogenesis.

Increased fatty acid synthase as a therapeutic target in androgen-independent prostate cancer progression

BACKGROUND

Fatty acid synthase (FAS) performs the anabolic conversion of dietary carbohydrate or protein to fat. FAS expression is low in most normal tissues, but is elevated in many human cancers, including androgen-sensitive and androgen-independent prostate cancer.

METHODS

Immunohistochemical evaluation of FAS expression was performed in human prostate cancer specimens under various states of androgen ablation. In vitro and in vivo prostate cancer models were evaluated for FAS expression and activity under androgenic and androgen-depleted conditions, and were tested for sensitivity to antimetabolite drugs that target fatty acid synthesis.

RESULTS

While FAS expression in the prostate was androgen responsive, it persisted or was reactivated in human prostate carcinoma after androgen ablation, and was high in 82% of lethal tumors examined at autopsy. Similar patterns of FAS expression and fatty acid synthesis were seen in cell culture and xenograft models of human prostate cancer. Pharmacologic inhibition of FAS resulted in a dose-dependent reduction of tumor growth in these models, including fourfold inhibition of an androgen-independent human prostate cancer xenograft with little associated toxicity.

CONCLUSIONS

The data suggest that FAS expression/FA synthesis provides an important functional aspect of the malignant phenotype in prostate cancer, perhaps supporting cell growth or survival. FAS expression may be upregulated by alternate signaling pathways important for prostate cancer growth under androgen withdrawal. The re-emergence of FAS expression and activity during the development of androgen independence demonstrate that FAS may serve as a novel target for antimetabolite therapy in prostate cancer.

Widely used prostate carcinoma cell lines share common origins

BACKGROUND

Cross-contamination is a persistent problem in the establishment and maintenance of mammalian cell lines. The observation that the cell lines PC-3, ALVA-31, and PPC-1 all have a homozygous deletion of the alpha-catenin gene prompted us to investigate the uniqueness of these and several other widely used prostate carcinoma cell lines.

METHODS

The genetic backgrounds of the putative human prostate cell lines (ALVA-31, ALVA-41, BPH-1, DU 145, JCA-1, LAPC-4, LNCaP, NCI-H660, ND-1, PC-3, PC-3MM2, PC-346C, PPC-1, and TSU-Pr1) were analyzed by cytogenetics, mutation analysis, and DNA profiling.

RESULTS

Similarities between several groups of cell lines were found. ALVA-31, ALVA-41, PC-3, PC-3MM2, and PPC-1 all have a deletion of a C in codon 138 of the p53 gene and show almost identical DNA profiles. The ND-1 cell line has two p53 mutations that are identical to the mutations found in DU 145. These two cell lines also share a high number of structural chromosomal abnormalities and nearly identical DNA profiles. The cell lines TSU-Pr1 and JCA-1 share an identical p53 mutation in exon 5 and identical DNA profiles.

CONCLUSIONS

Several widely used prostate carcinoma cell lines apparently have identities in common. The knowledge that some of these cell lines are derivatives of one another prompts re-evaluation of previously obtained results.

Functional evidence for the presence of tumor suppressor gene on chromosome 10p15 in human prostate cancers

Loss of heterozygosity on chromosome 10p was observed frequently in human prostate cancers. Studies have demonstrated that the introduction of the short arm of human chromosome 10 into a human prostate cancer cell line, PPC-1, by microcell-mediated chromosome transfer (MMCT), suppressed the malignant phenotype, suggesting the presence of a prostate tumor suppressor gene(s) within a region of 17 cM at distal 10p. To narrow down the candidate region harboring the tumor suppressor gene, a series of 10p fragments were transferred into PPC-1 cells by MMCT using a panel of hamster-human hybrid cells containing various portions of 10p. Four of the six hybrid cells obtained showed decreased tumorigenicity when injected subcutaneously into athymic nude mice. Tumors developed only at six of 40 injection sites for these four hybrid cells. In contrast, the other two hybrid cells, as well as parental PPC-1 cells, were judged to be fully tumorigenic because tumors appeared at a total 26 of 32 sites for the two hybrid cells and 15 of 16 sites for PPC-1. Allelotyping of 10p combined with fluorescence in situ hybridization in these hybrid cells suggested that a prostate tumor suppressor gene was located within a fragment of approximately 1.2 Mb flanked by D10S1172 and D10S226 on 10p15.1.

In vitro models to study cellular differentiation and function in human prostate cancers

In Vitro Models to Study Cellular Differentiation and Function in Human Prostate Cancers. To augment the currently available models of human prostate cancer in vitro, we have established extended life-span epithelial cultures from biopsies of well-differentiated prostate cancers. The genetic identity of the target cells was assessed by allelotyping, using microsatellites located on chromosome 8p, and microdissection of tissues and primary cell cultures. Cells with an extended life span (PxE6) were derived by recombinant retrovirus infection to introduce the human papilloma virus E6 gene (epithelial cells). Immunophenotyping of the resultant cell strains confirmed retention of differentiated cell functions, and the genotype of the E6-expressing epithelial cells was stable, while SV40-immortalized cultures were more unstable, leading to tetraploidy. All PxE6 cells eventually senesced, but an immortalized epithelial culture, P4E6, was derived from one of the epithelial cultures. The properties of this cell line, which remains close to diploid, are similar to those of early prostate cancer cells, and it retains expression of many prostate-associated antigens, such as prostate-specific antigen (PSA).

Altered Ets transcription factor activity in prostate tumor cells inhibits anchorage-independent growth, survival, and invasiveness

The Ets family of transcription factors are important downstream targets in cellular transformation, as altering Ets activity has been found to reverse the transformed phenotype of Ras transformed mouse fibroblasts and of several human tumor cell lines. To determine whether Ets factors are important targets in the largely uncharacterized aberrant signaling in prostate cancer, we have altered Ets activity in the prostate tumor cell line PPC-1, by stable expression of either full-length Ets2, or a dominant inhibitor of Ets activity, the Ets2 DNA binding domain (Ets2DBD). Analysis of multiple independent clonal cell lines revealed that expression of either Ets2 or the Ets2DBD inhibited the anchorage-independent growth of PPC-1 cells up to 20-fold. In contrast to our previous findings with Ras-transformed NIH3T3 cells, PPC-1 cell lines expressing either Ets2 or the EtsDBD exhibited slower attached cell growth, increased Ets-dependent gene expression, and up to a 10-fold increase in apoptotic cell death. The p21cip gene was identified as a potential target of altered Ets signaling. Interestingly, the two distinct Ets2 constructs had strikingly different effects on in vitro invasiveness. Expression of the Ets2DBD almost completely blocked PPC-1 cell invasion through Matrigel, whereas over-expression of full-length Ets2 did not inhibit invasion. Overall, these results demonstrate that the balance of Ets factor activity can regulate multiple aspects of the transformed phenotype of PPC-1 prostate tumor cells, including anchorage-independent growth, survival, and invasiveness.

Phenotypic and genotypic characterization of commonly used human prostatic cell lines

OBJECTIVE

To investigate and catalogue systematically the phenotypic and genotypic characteristics of the commonly used prostatic cell lines using immunocytochemistry and polymerase chain reaction (PCR) of hypervariable sequences within the genome to provide a 'fingerprint' characteristic of each cell line. Materials and methods Malignant (LNCaP, LNCaP-r, PC-3, DU-145) and benign immortalized prostatic cell lines (PNT-1A, PNT-1B, BPH-1) were grown on four-well slides, fixed and subjected to indirect streptavidin-biotin immunocytochemistry. Twenty-three antibodies were used in the following groups: cytoskeletal elements: cytokeratins (CK)-5, -7, -8, -14 (two), -16, -18, -19 (three), -20, vimentin and desmin; MUC1 (three); cell adhesion molecules (E-cadherin, alpha-beta-and gamma-catenin); and prostatic associated proteins: prostate specific antigen (PSA), prostatic acid phosphatase (PAP) and androgen receptor (AR). For the PCR, genomic DNA was extracted from the cell lines and from SKOV3 and MCF7 (positive controls). PCR was performed on three variable regions which were then sequenced: AR exon 1 (CAG repeat polymorphism), and two areas of microsatellite instability (MSI): AR exon 8 and hypoxanthine-guanine phosphoribosyl transferase (HPRT) exon 3.

RESULTS

All cell lines were CK-8/18 positive and most also expressed CK-7 and -19. Heterogeneous CK-20 expression was detected for the first time in prostatic cell lines. All lines were positive for vimentin and negative for desmin. MUC1 was expressed in one malignant (DU-145) and all immortalized cell lines. E-cadherin expression was low or absent in three lines: PNT1A, 1B and PC-3. Only PC-3 failed to express alpha-catenin; beta- and gamma-catenin were expressed by all lines. PSA, PAP and AR were only expressed by LNCaP and LNCaP-r. On PCR, the CAG repeat lengths in exon 1 of the AR ranged from 19 to 27. Three pairs of cell lines had the same exon 1 CAG repeat length: LNCaP/PC-3 (26 repeats), BPH-1/DU-145 (19 repeats) and PNT1 A/1B (20 repeats). Exon 8 sequences were identical except for LNCaP, which showed a single base mutation, and HPRT exon 3 sequences were all identical. There was no evidence of generalized MSI in any of the cell lines examined.

CONCLUSIONS

The cell lines studied fell into three broad groups according to their phenotypic characteristics: (i) prostatic marker positive (LNCaP and LNCaP-r); (ii) high expression of most antigens (DU-145, PC-3 and BPH-1); and (iii) low or absent expression of most antigens (PNT1 A and 1B). Each of the cell lines derived from PC could be identified on the basis of exon 1 and 8 AR sequence variability. DU145 and BPH-1 had identical profiles of the three areas studied, but these cell lines are easily distinguished by their different phenotypic characteristics. PNT1A and 1B had identical genetic and similar phenotypic profiles, which is unsurprising given that they are subclones derived from the same parental line. Even so, these were separable on the basis of CK-19 immunostaining. Using a combination of geno- and phenotypic markers it was possible to derive a 'fingerprint' for each of the cell lines assessed, which will allow meaningful comparison between similar cell lines held in other laboratories.

Fas-mediated apoptosis in seven human prostate cancer cell lines: correlation with tumor stage

BACKGROUND

Apoptosis, or programmed cell death, can be mediated through an endogenous signaling pathway that emanates from a cell surface receptor known as Fas. Although best recognized for its role in the immune system, recent studies have also suggested a role for Fas in mediating apoptosis in the murine prostate. Little is known, however, regarding the role of Fas-signaling in the human prostate, and if this signaling pathway is abrogated in the development of prostate cancer (PC).

METHODS

In the current study, seven human PC cell lines were evaluated for their sensitivities to Fas-mediated apoptosis, using both morphologic and flow cytometric methods. Fas expression by each cell line was quantitated by immunofluorescence, and gene expression of three putative inhibitory molecules was analyzed.

RESULTS

The differential sensitivities of the cell lines to Fas-mediated apoptosis were found to correlate with the clinical stage of the parental tumors. Specifically, the three most sensitive cell lines were all derived from primary tumors, while the four most resistant cell lines were derived from distant metastases. Immunofluorescent analyses of the PC cell lines revealed that the observed resistance to apoptosis was not due to reduced expression of membrane-bound Fas. Likewise, this resistance did not correlate with increased gene expression of the inhibitory molecules FAP-1, ICE epsilon, and Ich-1S.

CONCLUSIONS

Our results using established PC cell lines support previous studies with prostatic tissue specimens, and suggest that the normal, differentiated prostatic epithelium, as well as locally invasive PCs, have the potential to undergo Fas-mediated apoptosis. Conversely, these studies suggest that metastatic PCs have a reduced apoptotic potential that is mediated by a novel mechanism.

Sensitivity of human prostatic carcinoma cell lines to low dose rate radiation exposure

PURPOSE

Low dose rate radioemitters, such as 125I, 103Pd, and 89Sr, have been used both for local and systemic treatment of prostate cancer. Most normal cells exposed to ionizing radiation characteristically activate cell cycle checkpoints, resulting in cell cycle arrest at the G1/S and G2/M transition points. Cancer cells are typically quite sensitive to radiation killing late in the G2 phase of the replicative cell cycle. Furthermore, most cancer cells accumulating at the G2/M transition point as a result of low dose rate radiation exposure appear to become sensitive to further low dose rate irradiation. For this reason, protracted exposure of cancer cells to low dose rate radiation has been proposed to result in increased cancer cell killing as compared with brief exposures of cancer cells to high dose rate radiation. Since many human prostatic carcinomas contain somatic genome alterations targeting genes which affect the cell cycle and radiation-associated cell cycle checkpoints, we evaluated the effects of low dose rate radiation exposure on the cell cycle and on clonogenic survival for various human prostatic carcinoma cell lines.

MATERIALS AND METHODS

Human prostatic carcinoma cells from the LNCaP, DU 145, PC-3, PPC-1, and TSU-Pr1 cell lines were exposed to low dose rate (0.25 Gy/hour) or high dose rate (60 Gy/hour) radiation in vitro and then assessed for radiation cytotoxicity by clonogenic survival assay. Cell cycle perturbations following protracted exposure to low dose rate radiation were evaluated using flow cytometry.

RESULTS

For LNCaP cells, low dose rate radiation exposure resulted in an accumulation of cells at both the G1/S and the G2/M cell cycle transition points. For DU 145, PC-3, PPC-1, and TSU-Pr1 cells, treatment with low dose rate radiation triggered G2/M cell cycle arrest, but not G1/S arrest. Unexpectedly, the cell cycle redistribution pattern phenotypes observed, G1/S and G2/M cell cycle arrest versus G2/M arrest alone, appeared to have little effect on low dose rate radiation survival. Furthermore, while PC-3, PPC-1, and TSU-Pr1 cells exhibited increased cytotoxic sensitivity to low dose rate versus fractionated high dose rate radiation treatment, DU 145 and LNCaP cells did not.

CONCLUSIONS

Radiation-associated pertubations in replicative cell cycle progression were not dominant determinants of low dose rate radiation killing efficacy in human prostate cancer cell lines in vitro.

Quantification of integrin subunits on human prostatic cell lines--comparison of nontumorigenic and tumorigenic lines

BACKGROUND

We set out to quantify integrin subunits on the surface of several prostate cell lines, including two nontumorigenic lines, in order to assess their role in tumorigenicity and metastasis.

METHODS

Flow cytometry was used to estimate the amounts of each subunit by changes in mean fluorescence intensity from control antibody. An in vitro Matrigel (Collaborative Biomedical Products, Bedford, MA) assay was used to determine invasiveness.

RESULTS

Profiles of each cell line were developed using the change in subunit mean fluorescence intensity normalized to the beta 1-subunit. The alpha 4-subunit is only expressed on nontumorigenic cells. These same cells were unable to invade Matrigel.

CONCLUSIONS

Comparison of nontumorigenic and cancerous lines suggests that a loss of the alpha 4-subunit correlates with the acquisition of tumorigenicity and perhaps metastatic potential. The ability to quantify expression of integrin subunits on prostate cell lines allows the determination of regulation by factors responsible for growth, tumorigenicity, and/or metastasis.

Involvement of CD44 and its variant isoforms in membrane-cytoskeleton interaction, cell adhesion and tumor metastasis

CD44s (standard form of CD44) is a transmembrane glycoprotein whose external domain displays extracellular matrix adhesion properties by binding both hyaluronic acid (HA) and collagen. The cytoplasmic domain of CD44s interacts with the cytoskeleton by binding directly to ankyrin. It has been shown that post-translational modifications, such as phosphorylation (by protein kinase C), acylation (by acyl-transferase) and GTP-binding enhanced CD44's interaction with cytoskeletal proteins. Most importantly, the interaction between CD44s and the cytoskeletal protein, ankyrin, is required for the modulation of CD44s cell surface expression and its adhesion function. Recently, a number of tumor cells and tissues have been shown to express CD44 variant (CD44v) isoforms. Using RT-PCR and DNA sequence analyses, we have found that unique CD44 splice variant isoforms are expressed in both prostate and breast cancer cell lines and carcinomas. Most importantly intracellular ankyrin is preferentially accumulated underneath the patched/capped structures of CD44 variant isoform in both breast and prostate cancer cells attached to HA-coated plates. We propose that selective expression of CD44v isoforms unique for certain metastatic carcinomas and their interaction with the cytoskeleton may play a pivotal role in regulating tumor cell behavior during tumor development and metastasis.

Neuroendocrine peptides stimulate adenyl cyclase in normal and malignant prostate cells

Elevations of intracellular cAMP in human prostate cancer cells have been shown to increase invasiveness and to promote neuronal differentiation. Since neuroendocrine peptides capable of activating adenyl cyclase are present in prostatic nerves and epithelial neuroendocrine cells, we investigated normal and malignant human prostate cells for changes in intracellular cAMP in response to the prostatic peptides vasoactive intestinal peptide (VIP), calcitonin (CT), and calcitonin gene-related peptide (CGRP). Normal prostate epithelial cells and LNCaP prostate cancer cells exhibited, respectively, 6- and 30-fold increases in intracellular cAMP in response to VIP. ALVA-31 and PPC-1 prostate cancer cells demonstrated 20- to 200-fold increases in cAMP in response to CGRP, while normal epithelial cells and LNCaP cells exhibited smaller (2- to 6-fold) responses. Only DU-145 cells increased cAMP substantially in response to CT. VIP receptor mRNA was identified by Northern blot analysis only in those cells that responded to VIP. CT receptor mRNA was identified only in DU-145 cells by polymerase chain reaction and Southern blot analysis. These results suggest that VIP and possibly CGRP receptors are likely to be present in both normal and malignant prostate cells. VIP or CGRP may regulate secretion of proteases by normal or prostate cancer cells and may influence epithelial cell differentiation.

Interaction of CD44 variant isoforms with hyaluronic acid and the cytoskeleton in human prostate cancer cells

CD44 is a glycosylated adhesion molecule which may undergo alternative splicing of 10 possible exons to generate variant isoforms. A number of CD44 variant isoforms expressed by tumor cells have been correlated with metastatic and proliferative behavior. In this study, we have characterized CD44 isoform expression on three prostate cancer cell lines: ALVA-31, PPC-1, and LNCaP. Using reverse transcriptase-polymerase chain reaction, we have found that ALVA-31 and PPC-1 cells express multiple CD44 isoforms, including CD44s (standard form), CD44E (epithelial form), and an exon 14-containing form. In addition, two smaller forms have been detected: one using an alternative donor splice site within exon 5, and a novel form omitting exon 5 entirely. The CD44 isoforms expressed by ALVA-31 and PPC-1 cells appear to be preferentially located on the cell surface. By contrast, LNCaP cells do not express any of the CD44 forms at the RNA or protein level. Both PPC-1 and ALVA-31 cells display tumorigenesis and invasiveness in nude mice, whereas LNCap cells exhibit a less malignant phenotype, suggesting a correlation between CD44 variant (CD44v) expression and aggressive prostate tumor behavior. Functional characterization reveals that CD44 mediates prostate cell adhesion to extracellular hyaluronic acid (HA). In addition, the CD44 cytoplasmic domain binds specifically to ankyrin, a membrane cytoskeletal protein. Double immunofluorescence labeling and confocal microscopic analyses indicate that HA binding induces the HA receptor (i.e., CD44) to form capped structures. Importantly, intracellular ankyrin is preferentially accumulated underneath HA receptor-capped structures. These results suggest that cytoskeletal proteins such as ankyrin are closely associated with CD44-mediated signaling events induced by HA. Finally, HA-mediated transmembrane interactions between CD44 isoforms and cytoskeletal proteins (i.e. ankyrin) may play a pivotal role in regulating tumor cell behavior during human prostate cancer development.

Cytidine methylation of regulatory sequences near the pi-class glutathione S-transferase gene accompanies human prostatic carcinogenesis

Hypermethylation of regulatory sequences at the locus of the pi-class glutathione S-transferase gene GSTP1 was detected in 20 of 20 human prostatic carcinoma tissue specimens studied but not in normal tissues or prostatic tissues exhibiting benign hyperplasia. In addition, a striking decrease in GSTP1 expression was found to accompany human prostatic carcinogenesis. Immunohistochemical staining with anti-GSTP1 antibodies failed to detect the enzyme in 88 of 91 prostatic carcinomas analyzed. In vitro, GSTP1 expression was limited to human prostatic cancer cell lines containing GSTP1 alleles with hypomethylated promoter sequences; a human prostatic cancer cell line containing only hypermethylated GSTP1 promoter sequences did not express GSTP1 mRNA or polypeptides. Methylation of cytidine nucleotides in GSTP1 regulatory sequences constitutes the most common genomic alteration yet described for human prostate cancer.

Detection by DNA fingerprinting of somatic changes during the establishment of a new prostate cell line

The establishment of a new prostate cell line (BM1604) from a human prostatic adenocarcinoma is reported. The line was rapidly established by culture of tissue on an extracellular matrix, previously laid down by culture of non-related cells. The method has been shown to work well, and other prostate lines have recently been cultured in this way. The cells have a doubling time of 28 h. DNA fingerprinting comparison of the genome from the tumour, the germline and the cells shows that somatic mutations have occurred in the tumour and that clonal selection has clearly occurred in establishment of the line. Many somatic mutations are apparent in the selected cells, which are now stable in culture. This method and the cells may be a useful addition to the limited material available for the in vitro study of prostate cells.

Use of fluorescent in situ hybridization for deoxyribonucleic acid ploidy analysis of prostatic adenocarcinoma

Fluorescent in situ hybridization using 2 chromosome specific centromere probes was evaluated as a method of ploidy analysis in touch preparations from 50 radical prostatectomy specimens. Tumors were classified as aneuploid by fluorescent in situ hybridization when nuclei had an abnormal copy number (aneusomic) for either chromosome centromere 8 or 12. Tetraploid tumors were defined as those with 4 copies (tetrasomic) of chromosome centromeres 8 and 12. The fluorescent in situ hybridization ploidy patterns were compared to the deoxyribonucleic acid (DNA) ploidy patterns subsequently obtained by flow cytometry on the same tissue following paraffin embedding. Concordant fluorescent in situ hybridization and flow cytometry ploidy classification was obtained in 82% of the cases (p < or = 0.0001). Of 7 aneuploid tumors 3 were identified by both methods. Trisomy 8 was detected by fluorescent in situ hybridization in 3 cases that were classified as DNA diploid (2 tumors) and DNA tetraploid (1 tumor). Conversely, flow cytometry detected aneuploidy (hypotetraploidy) in 1 tumor when the fluorescent in situ hybridization results were consistent with tetraploidy. Overall, fluorescent in situ hybridization was more sensitive in aneuploidy detection (6 of 7 cases) than flow cytometry (4 of 7). Of 19 tetraploid cases 5 had discordant fluorescent in situ hybridization and flow cytometry results. However, all 5 cases contained low levels of tetraploidy and the discrepant results were most likely due to the limits of precision of 1 or both methods. In conclusion, we demonstrated that fluorescent in situ hybridization ploidy analysis can be rapidly performed on fresh touch preparations of prostate tissue. This preliminary study demonstrates that the ploidy result determined by fluorescent in situ hybridization correlates well with that obtained by flow cytometry. More complete fluorescent in situ hybridization studies of prostate carcinoma will require additional probes for other chromosomes.

Cytogenetic survey of 32 cancers of the prostate

Cytogenetic studies after short-term culture were performed on 32 adenocarcinomas of the prostate from patients without prior treatment. The tumor specimens, ranging from stage B1 to D1, were obtained by radical prostatectomy or diagnostic biopsies. Fourteen tumors showed a normal diploid chromosome complement in all metaphases examined. Clonal chromosomal alterations were detected in 16 tumor samples and the remaining two cases contained double minute (dmin) chromosomes in some cells. The most frequent numerical changes included loss the Y chromosome and trisomy 7, both found in four cases. The only recurrent structural aberration was del(10)(q24), seen in three cases both as a sole anomaly and within multiple rearrangements. Six patients showed cytogenetically unrelated clones. The occurrence of the chromosomal changes found in this study shows no relationship to certain histopathologic characteristics of the tumors. The recurrent finding of del(10)(q24) as sole anomaly and the evidence for clonal evolution in one patient demonstrates that this change is an early karyotypic event which may be important for the pathogenesis in at least a subset of prostatic cancers.

Human primary prostate tumor cell line, ALVA-31: a new model for studying the hormonal regulation of prostate tumor cell growth

A new human prostate tumor cell line (ALVA-31) has been established from a biopsy specimen of primary tumor obtained during prostatectomy. The cell line has been maintained for more than 48 months in stable growth. The in vitro doubling time was determined to be approximately 26 hr. The chromosome number ranged from 24-112, with a modal number of 59 tested over several time points throughout continuous culture. Karyotypic analysis of late-passaged cells demonstrated approximately 70 human chromosomes, 8-14 markers, and two X chromosomes without a Y chromosome. Prostatic origin was confirmed by the expression of both prostate specific antigen and prostatic acid phosphatase, using specific antisera and immunoradiolabelling techniques. Prostate tumor xenografts were grown in intact male, castrate male, and female athymic mice; however, the rate of tumor growth was clearly dependent upon serum testosterone levels.

Establishment and characterization of a human primary prostatic adenocarcinoma cell line (ND-1)

A human primary prostatic adenocarcinoma cell line named ND-1 has been established in long term tissue culture. The cultured cells show growth in both monolayers and in soft agar suspension and produce subcutaneous tumors in nude mice. Cytogenetic analysis by G-banding demonstrated an aneuploid karyotype with a modal chromosome number of 62, and multiple marker chromosomes with 25-30% structural abnormalities. Ploidy analysis revealed that the majority of ND-1 cells (67%) had a DNA mass of 10.1 picogram and DNA index of 1.41. Nineteen percent of cells had a DNA mass of 21.3 picogram and DNA index of 3.0. Electron microscopic studies revealed common features of neoplastic epithelial cells such as numerous microvilli, junctional complexes, abnormal nuclei, nucleoli, and mitochondria. Due to the absence of a structurally normal Y chromosome, confirmation of the presence of a derived Y chromosome was achieved through the use of C-banding and through fluorescent in situ hybridization with a Y chromosome repeat probe. Tandem E PSA immunoenzymatic assay revealed that these ND-1 cells secrete small amounts of prostate specific antigen.

Chromosomal abnormalities and related events in prostate cancer

The amount of cytogenetic information on prostate cancer is relatively sparse when compared with that on other common adenocarcinomas. This is primarily due to frequent overgrowth in culture of the cancer cells by normal (diploid) cells. Although newly introduced techniques of in situ hybridization will undoubtedly reveal chromosome changes in a high percentage of primary and noncultured prostate cancers, such information is at present essentially limited to numeric changes, with structural changes (eg, translocations and deletions) not being readily or reliably ascertained with presently available in situ approaches. Future developments are likely to overcome these shortcomings and, thus, make possible detailed analysis of karyotypes in prostate cancer in a much higher proportion of these tumors than available up to now. The cytogenetic data on prostate cancer in the literature are reviewed in this article and, based on the frequent involvement of some chromosomes (nos. 2, 7, 8, 10, and 16) in and molecular data on prostate cancer, a suggested multistep process for the development of prostate cancer is presented. The steps in this process may not apply to all prostate cancers or in fact be the definitive ones, but the suggested scheme does indicate that a number of ordered genetic events are involved in the process of prostate cancer genesis. Epidemiologic and familial aspects of prostate cancer also have been discussed in this review as they might relate to the genetics of the disease.

Cytogenetic analysis of 57 primary prostatic adenocarcinomas

Cytogenetic analysis after short-term culture in vitro of primary tumor samples was attempted in 82 patients with prostatic cancer. Tumor material was obtained by radical prostatectomy or transurethral resection. Successful cytogenetic studies were performed on 57 tumors of which five were well, 30 moderately, and 22 poorly differentiated adenocarcinomas. Only normal karyotypes were found in 24 tumors. Structural nonclonal aberrations were detected in 18 and clonal karyotypic abnormalities in 15 tumors. The most common clonal numerical aberration was loss of the Y chromosome; a missing Y was found in six tumors, in three of these as the sole anomaly. Clonal structural chromosomal rearrangements, usually accompanied by numerical changes, were detected in 12 tumors. The rearrangements involved 18 of the 22 autosomes and the X chromosome. Chromosomes 1, 7, and 10 were most frequently affected. Deletions, duplications, inversions, insertions, and balanced as well as unbalanced translocations were represented. The breakpoints in chromosome 1 were scattered along both the short and long arms with no obvious clustering, whereas those in chromosomes 7 and 10 were clustered at bands 7q22 (two deletions and two duplications in four different tumors) and 10q24 (two translocations, one deletion, and one inversion in four tumors). One additional tumor displayed a derivative chromosome 10 with a breakpoint in 10q23, and one had monosomy 10. Altogether, these abnormalities resulted in loss of 10q24----qter in five tumors. Monosomy 8 and rearrangements of the short arm of chromosome 8 leading to loss of 8p21----pter were seen in four tumors. Double minute chromosomes were found in two tumors.

Establishment and characterization of a new human prostatic carcinoma cell line (DuPro-1)

A new human prostate adenocarcinoma cell line (DuPro-1) has been established from the athymic nude mouse supported xenograft DU5683. This was accomplished by embedding dispersed xenograft cells in 0.1 by 5.0 cm. spaghetti-like strands of Basement Membrane MATRIGEL [BMM (Collaborative Research, Inc.)], a unique technique facilitating the transition to tissue culture. Now passed over 30 times, the cells display anchorage and serum concentration independent growth with a doubling time of 22 to 24 hours. Cells exhibit pronounced morphological differences when grown on BMM coated culture dishes, assuming a pseudoglandular configuration, in contrast to typical homogeneous monolayer growth on plastic culture dishes. Light and electron microscopy show cohesive sheets of anaplastic epithelial cells, consistent with prostate carcinoma. Karyotypic analysis revealed all human chromosomes, near tetraploidy, 10 to 12 markers, and 3 to 4 X chromosomes, without a Y chromosome. Cells injected s.c. or embedded in BMM and implanted in the subrenal capsule space are equally tumorigenic in male and female athymic mice, suggesting that DuPro-1 cells are hormonally insensitive. Embedding cells in BMM may be useful in developing other tissue culture cell lines from neoplasms difficult to initiate in vitro. DuPro-1 should provide a valuable means to study the biology, immunology, and chemosensitivity of human prostate cancer.

Metastatic properties of the human prostatic cell line, PPC-1, in athymic nude mice

Limitation in the number of human prostatic cell lines has created a gap in knowledge regarding the in-vivo progression of this common cancer. The recently isolated primary prostatic carcinoma cell line, PPC-1, has been shown to be tumorigenic in athymic nude mice. These cells are now shown to form metastases to secondary sites in 10 of 12 animals in this initial study. Metastases were localized to lung and lymph nodes, and the tumor histology closely resembled that of the undifferentiated, rapidly dividing primary tumors. This is the first report describing the metastatic properties of a primary prostatic cancer cell line. PPC-1 cells are therefore likely to represent a good model system for the study of human prostate cancer progression.

Immunohistochemical evaluation of the expression of prostate tumor-association markers in the nude mouse human prostate carcinoma heterotransplant lines PC-82, PC-EW, and PC-EG

The biotin-avidin immunoperoxidase assay was used to evaluate the expression of several prostate carcinoma-associated markers in formalin-fixed paraffin-embedded tissue sections of three human prostate nude mouse heterotransplant lines PC-82, PC-EW, and PC-EG. In addition to monoclonal antibodies to PSA and PAP, monoclonal antibodies to five other potentially useful markers for prostate carcinomas (TURP-27, Leu-7, 7E11-C5, PSP-19, and PD41) were tested. Tissues from two or more transplant passages were evaluated. The human prostate target antigens were found to be expressed by one or more of the three heterotransplant lines. The PC-82 and PC-EW lines were the most efficient in terms of expression of multiple prostate carcinoma-associated markers and percentage of tumor cells positive for a given prostate antigen. The staining pattern of each marker, in terms of staining intensity, number of tumor cells stained, and staining location, i.e., membrane, cytoplasmic, or ductal secretions, was similar to what has been observed in tissue sections from human prostate carcinomas. The lack of an appropriate model for evaluating the preclinical potential of these Mabs (especially TURP-27, PSP-19, and PD41) makes the findings of this study of considerable importance, and suggests that these human prostate xenografts may be useful models for exploring the diagnostic and therapeutic potential of these anti-prostate carcinoma monoclonal antibodies.

Dunning rat prostate tumors and cultured cell lines fail to express human prostate carcinoma-associated antigens

The objective of this study was to determine if human prostate carcinoma-associated tumor markers were expressed by Dunning rat prostate carcinomas. Frozen and formalin-fixed paraffin-embedded tissues from 12 different sublines of Dunning tumors were evaluated for marker expression by immunoperoxidase staining by using a panel of 9 monoclonal antibodies, including antibodies against human PAP and PSA. None of the Dunning tumors were found to express any of the human prostate tumor markers. Both fixed and live immunofluorescent assays were performed on 5 cultured Dunning tumor cell lines, evaluated either as single cells or as monolayers. As with the Dunning tumor tissues, none of the cell cultures expressed any of the 9 human prostate tumor markers. The lack of antigen expression by the Dunning tumor tissues and cell lines suggests that these human prostate tumor markers are quite species specific. These results limit the use of the Dunning prostate tumors as models to explore the preclinical application of these human prostate carcinoma-associated monoclonal antibodies and their target antigens.