Immortalization of human prostate epithelial cells by HPV 16 E6/E7 open reading frames

Characterisation of cell lines derived from prostate cancer patients with localised disease

BACKGROUND

Prostate cancer is a broad-spectrum disease, spanning from indolent to a highly aggressive lethal malignancy. Prostate cancer cell lines are essential tools to understanding the basic features of this malignancy, as well as in identifying novel therapeutic strategies. However, most cell lines routinely used in prostate cancer research are derived from metastatic disease and may not fully elucidate the molecular events underlying the early stages of cancer development and progression. Thus, there is a need for new cell lines derived from localised disease to better span the disease spectrum.

METHODS

Prostatic tissue from the primary site, and adjacent non-cancerous tissue was obtained from four patients with localised disease undergoing radical prostatectomy. Epithelial cell outgrowths were immortalised with human papillomavirus type 16 (HPV16) E6 and E7 to establish monoclonal cell lines. Chromosomal ploidy was imaged and STR profiles were determined. Cell morphology, colony formation and cell proliferation characteristics were assessed. Androgen receptor (AR) expression and AR-responsiveness to androgen treatment were analysed by immunofluorescence and RT-qPCR, respectively. RNA-seq analysis was performed to identify prostate lineage markers and expression of prostate cancer tumorigenesis-related genes.

RESULTS

Two benign cell lines derived from non-cancer cells (AQ0420 and AQ0396) and two tumour tissue derived cancer cell lines (AQ0411 and AQ0415) were immortalised from four patients with localised prostatic adenocarcinoma. The cell lines presented an epithelial morphology and a slow to moderate proliferative rate. None of the cell lines formed anchorage independent colonies or displayed AR-responsiveness. Comparative RNA-seq expression analysis confirmed the prostatic lineage of the four cell lines, with a distinct gene expression profile from that of the metastatic prostate cancer cell lines, PC-3 and LNCaP.

CONCLUSIONS

Comprehensive characterization of these cell lines may provide new in vitro tools that could bridge the current knowledge gap between benign, early-stage and metastatic disease.

Does Human Papillomavirus Play a Causative Role in Prostate Cancer? A Systematic Review Using Bradford Hill's Criteria

Globally, prostate cancer is the fifth most common cause of cancer-related death among men, and metastatic castration-resistant prostate cancer has a high cancer-related mortality rate. However, the aetiology of this disease is not yet fully understood. While human papillomavirus (HPV) has been associated with several types of cancer, including cervical, anal, and oropharyngeal cancers, studies investigating the relationship between HPV and prostate cancer have shown mixed results. This systematic review aimed to evaluate the causative association between HPV and prostate cancer using Bradford Hill's criteria. A comprehensive search of PubMed was conducted, and 60 out of 482 studies were included in the review. The included studies were evaluated based on nine Bradford Hill criteria, and information on the identification and transmission of the virus and potential oncogenic mechanisms was also extracted. The strength of association criterion was not met, and other criteria, such as consistency and coherence, were not fulfilled. However, biological plausibility was supported, and potential oncogenic mechanisms were identified. While some studies have reported the presence of HPV in prostate cancer tissues, the overall quality of evidence remains low, and the association between HPV and prostate cancer is weak. Nevertheless, the prostate is a potential reservoir for the transmission of HPV, and the HPV E6 and E7 oncoproteins and inflammation are likely to be involved in any oncogenic mechanisms. Further studies with a higher level of evidence are needed to establish a definitive link between HPV and prostate cancer.

Protective effects of conditioned media of immortalized stem cells from human exfoliated deciduous teeth on pressure ulcer formation

Pressure ulcers (PUs) are increasing with aging worldwide, but there is no effective causal therapy. Although mesenchymal stem cells (MSCs) promote cutaneous wound healing, the effects of the conditioned medium (CM) of MSCs on cutaneous PU formation induced by ischemia-reperfusion injury have been poorly investigated. To address this issue, herein, we first established an immortalized stem cell line from human exfoliated deciduous teeth (SHED). This cell line was revealed to have superior characteristics in that it grows infinitely and vigorously, and stably and consistently secretes a variety of cytokines. Using the CM obtained from the immortalized SHED cell line, we investigated the therapeutic potential on a cutaneous ischemia-reperfusion mouse model for PU formation using two magnetic plates. This is the first study to show that CM from immortalized SHEDs exerts therapeutic effects on PU formation by promoting angiogenesis and oxidative stress resistance through vascular endothelial growth factor and hepatocyte growth factor. Thus, the CM of MSCs has potent therapeutic effects, whereas these therapies have not been implemented in human medicine. To try to meet the regulatory requirements for manufacturing and quality control as much as possible, it is necessary to produce CM that is consistently safe and effective. The immortalization of stem cells could be one of the breakthroughs to meet the regulatory requirements and consequently open up a novel avenue to create a novel type of cell-free regenerative medicine, although further investigation into the quality control is warranted.

Evidence for a causal role by human papillomaviruses in prostate cancer - a systematic review

It is hypothesised that high risk for cancer human papillomaviruses (HPVs) have a causal role in prostate cancer.

In 26 case control studies, high risk HPVs have been identified in benign and prostate cancers. High risk HPVs were identified in 325 (22.6%) of 1284 prostate cancers and in 113 (8.6%) of 1313 normal or benign prostate controls (p = 0.001).

High risk HPVs of the same type have been identified in both normal and benign prostate tissues prior to the development of HPV positive prostate cancer. High risk HPVs can be associated with inflammatory prostatitis leading to benign prostate hyperplasia and later prostate cancer. Normal human prostate epithelial cells can be immortalised by experimental exposure to HPVs. HPVs are probably sexually transmitted.

The role of HPVs in prostate cancer is complex and differs from HPVs associated cervical cancer. HPV infections may initiate prostate oncogenesis directly and influence oncogenesis indirectly via APOBEC enzymes. HPVs may collaborate with other pathogens in prostate oncogenesis.

Although HPVs are only one of many pathogens that have been identified in prostate cancer, they are the only infectious pathogen which can be prevented by vaccination.

A causal role for HPVs in prostate cancer is highly likely.

Androgen receptor expression reduces stemness characteristics of prostate cancer cells (PC3) by repression of CD44 and SOX2

Studies have shown that a subgroup of tumor cells possess stemness characteristics having self-renewal capacity and the ability to form new tumors. We sought to identify the plausible stemness factor that determines the "molecular signature" of prostate cancer (PCa) cells derived from different metastases (PC3, PCa2b, LNCaP, and DU145) and whether androgen receptor (AR) influences the maintenance of stemness features. Here we show sex-determining region Y (SRY)-box 2 (SOX2) as a putative stem cell marker in PC3 PCa cells and not in DU145, PCa2b, or LNCaP cells. PCa2b and PC3 cells were derived from bone metastases. PCa2b cells which are positive for the AR failed to demonstrate the expression of either cluster of differentiation 44 (CD44) or SOX2. Knockdown (KD) of AR in these cells did not affect the expression of either CD44 or SOX2. Conversely, PC3 cells, which are negative for AR, expressed both CD44 and SOX2. However, the expression of AR downregulated the expression of both CD44 and SOX2 in PC3 cells. CD44 regulates SOX2 expression as KD of CD44 and reduces SOX2 levels considerably. SOX2 KD attenuated not only the expression of SNAIL and SLUG but also the migration and tumorsphere formation in PC3 cells. Collectively, our findings underscore a novel role of CD44 signaling in the maintenance of stemness and progression of cancer through SOX2 in AR-independent PC3 cells. SOX2 has a role in the regulation of expression of SNAIL and SLUG. SOX2 could be a potential therapeutic target to thwart the progression of SOX2-positive cancer cells or recurrence of androgen-independent PCa.

KIF7 attenuates prostate tumor growth through LKB1-mediated AKT inhibition

This study investigated kinesin family member 7 (KIF7) expression and function in prostate cancer (PCa). Our results showed that KIF7 was significantly downregulated in PCa, compared with normal, benign prostatic hyperplasia and prostate intraepithelial neoplasia tissues, partially through promoter hypermethylation. We further investigated the effects of KIF7 coiled coil (CC) domain and motor domain (MD) on PCa development in vitro and in vivo. Our results showed that KIF7-CC but not KIF7-MD significantly attenuated proliferation and colony formation, impeded migration and invasion, induced apoptosis and sensitized PCa cells to paclitaxel. Further analysis revealed that KIF7-CC enhanced LKB1 expression and phosphorylation at Ser⁴²⁸, which induced PTEN phosphorylation at Ser³⁸⁰/Thr^382/383 and consequently blocked AKT phosphorylation at Ser⁴⁷³. Downregulation of LKB1 significantly attenuated the suppressive effects of KIF7-CC on cell proliferation, colony formation and AKT phosphorylation. Furthermore, our in vivo studies showed that KIF7-CC reduced prostate tumorigenesis in cell-derived xenografts. Downregulation of LKB1 abrogated the anti-tumor effects of KIF7-CC in these xenografts. Taken together, these findings provide the first evidence to support the role of KIF7 as a negative regulator that inhibits PCa development partially through LKB1-mediated AKT inhibition.

Human Papilloma Virus Detection by INNOLiPA HPV in Prostate Tissue from Men of Northeast Mexico

Background:

Prostatic adenocarcinoma by Prosate cancer (PCa) is the most prevalent cancer and the second cause of cancer-related death among men in the Western world. Human papilloma virus (HPV) may be considered as a preventable risk factor. In this study, we assessed the frequencies of HPV infection in prostatic adenocarcinoma and benign prostatic hyperplasia (BPH) cases in Northeast Mexico.

Materials and Methods:

A total of 87 paraffin-embedded blocks (from 25 and 62 patients with definite diagnoses of BPH and adenocarcinoma, respectively) were selected and subjected to INNOLiPA HPV Genotyping to detect 28 high- and low-risk HPV types. The rates of infection were compared in the two studied groups.

Results:

INNOLiPA HPV demonstrated great sensitivity for HPV detection on paraffin-embedded tissue. Global prevalence was 14.9% (13/87). HPV infection was positive in 19.4% (12/62) of patients with adenocarcinoma and 4.0% (1/25) of patients with BPH. HPV-11, which is considered to be low risk, was more prevalent. Interestingly, one patient with BPH and six with prostate cancer showed examples considered to be high risk (HPV-18, -51, -52, and -66).

Conclusion:

A higher rate of HPV infection among Mexican patients with prostatic carcinoma than among those with BPH was observed. HPV infections may thus contribute to the risk of prostate cancer. Further studies are required to elucidate any roles of HPV infection in prostate disease in Mexico and the effect of prevention and treatment of HPV infection on prostatic adenocarcinoma.

Androgen Receptor-Mediated Growth Suppression of HPr-1AR and PC3-Lenti-AR Prostate Epithelial Cells

The androgen receptor (AR) mediates the developmental, physiologic, and pathologic effects of androgens including 5α-dihydrotestosterone (DHT). However, the mechanisms whereby AR regulates growth suppression and differentiation of luminal epithelial cells in the prostate gland and proliferation of malignant versions of these cells are not well understood, though they are central to prostate development, homeostasis, and neoplasia. Here, we identify androgen-responsive genes that restrain cell cycle progression and proliferation of human prostate epithelial cell lines (HPr-1AR and PC3-Lenti-AR), and we investigate the mechanisms through which AR regulates their expression. DHT inhibited proliferation of HPr-1AR and PC3-Lenti-AR, and cell cycle analysis revealed a prolonged G₁ interval. In the cell cycle, the G₁/S-phase transition is initiated by the activity of cyclin D and cyclin-dependent kinase (CDK) complexes, which relieve growth suppression. In HPr-1AR, cyclin D1/2 and CDK4/6 mRNAs were androgen-repressed, whereas CDK inhibitor, CDKN1A, mRNA was androgen-induced. The regulation of these transcripts was AR-dependent, and involved multiple mechanisms. Similar AR-mediated down-regulation of CDK4/6 mRNAs and up-regulation of CDKN1A mRNA occurred in PC3-Lenti-AR. Further, CDK4/6 overexpression suppressed DHT-inhibited cell cycle progression and proliferation of HPr-1AR and PC3-Lenti-AR, whereas CDKN1A overexpression induced cell cycle arrest. We therefore propose that AR-mediated growth suppression of HPr-1AR involves cyclin D1 mRNA decay, transcriptional repression of cyclin D2 and CDK4/6, and transcriptional activation of CDKN1A, which serve to decrease CDK4/6 activity. AR-mediated inhibition of PC3-Lenti-AR proliferation occurs through a similar mechanism, albeit without down-regulation of cyclin D. Our findings provide insight into AR-mediated regulation of prostate epithelial cell proliferation.

Viral infections in prostate carcinomas in Chilean patients

BACKGROUND

A few viruses have been detected in prostate cancer, however their role in the development of this malignancy has not been determined. The aim of this study was to analyze the presence and functionality of human papillomavirus (HPV) and polyomaviruses (BKPyV and JCPyV) in prostate carcinomas in Chilean patients.

METHODS

Sixty-nine primary prostate carcinomas were analyzed for the presence of HPV, BKPyV and JCPyV using standard polymerase chain reaction protocols. In addition, when samples were positive for HPyV, large T antigen (TAg) transcripts were analyzed using reverse transcriptase PCR.

RESULTS

HPV and JCPyV were not detected in any specimens (0/69, 0 %); whereas, BKPyV was detected in 6/69 PCas (8.7 %). We did not find a statistically significant association between the presence of BKPyV and age (p = 0.198) or Gleason score (p = 0.268). In addition, 2/6 (33 %) BKPyV positive specimens showed detectable levels of TAg transcripts.

CONCLUSIONS

There was no association between HPV or JCPyV presence and prostate cancer development. The presence of BKPyV in a small subset of prostate carcinomas in Chilean patients could indicate that this virus plays a potential role in prostate cancer development and requires further investigation.

Establishment and characterization of a highly tumorigenic African American prostate cancer cell line, E006AA-hT

Genuine racial differences in prostate cancer (PCa) biology have been considered among the potential reasons to explain PCa disparities. There is no animal model to represent all aspects of human PCa and, more specifically, to be used for PCa disparity research. The lack of a spontaneously transformed in vitro cell-based model system has been a significant impediment to investigating and understanding potential molecular mechanisms, and the hormonal, genetic, and epigenetic factors underlying the biological and clinical aggressiveness of PCa in African American (AA) men.

In this study, we established and characterized the E006AA-hT cell line as a highly tumorigenic subline of the previously characterized primary AA-PCa cell line, E006AA. Extensive characterization of the E006AA-hT cell line was accomplished using cytodifferentiation and prostate-specific markers, spectral karyotyping, cell line authentication assays, cell proliferation and migration assays, and in vitro tumorigenesis assays.

Spectral karyotyping of E006AA-hT showed a hypertriploid chromosome complement and shared cytogenetic changes similar to its parental cells such as diploid X, absence of Y-chromosomes, numerical gains in chromosomes 5,6,8,10,17,20,21, and marker chromosomes of unknown origin. In addition, E006AA-hT also presented numerous clonal and structural aberrations such as insertion, deletion, duplication, and translocations in chromosomes 1-5, 8, 9, 11, 13, 14, 17, and 18. The E006AA-hT cell line was shown to be highly tumorigenic and produced tumors at an accelerated growth rate in both athymic nude and triple-deficient SCID mice.

Silencing the mutated androgen receptor (AR-599 Ser>Gly) did not affect proliferation (loss-of-function), but decreased migration (gain-of-function) in E006AA-hT and its parental cell type. These data support that AR-point mutations may lead simultaneously to different “loss-of-function” and “gain-of-function” phenotypes in PCa cells. E006AA-Par and its subline as the only available spontaneously transformed low- and highly-tumorigenic primary AA-PCa cell lines could be used for basic and translational research aimed in supporting prostate cancer disparity research.

Osteopontin and MMP9: Associations with VEGF Expression/Secretion and Angiogenesis in PC3 Prostate Cancer Cells

Osteopontin and MMP9 are implicated in angiogenesis and cancer progression. The objective of this study is to gain insight into the molecular mechanisms underlying angiogenesis, and to elucidate the role of osteopontin in this process. We report here that osteopontin/αvβ3 signaling pathway which involves ERK1/2 phosphorylation regulates the expression of VEGF. An inhibitor to MEK or curcumin significantly suppressed the phosphorylation of ERK1/2 and expression of VEGF. MMP9 knockdown reduces the secretion but not the expression of VEGF. Moreover, MMP9 knockdown increases the release of angiostatin, a key protein that suppresses angiogenesis. Conditioned media from PC3 cells treated with curcumin or MEK inhibitor inhibited tube formation in vitro in human microvascular endothelial cells. Similar inhibitory effect on tube formation was found with conditioned media collected from PC3 cells expressing mutant-osteopontin at integrin-binding site and knockdown of osteopontin or MMP9. We conclude that MMP9 activation is associated with angiogenesis via regulation of secretion of VEGF and angiostatin in PC3 cells. Curcumin is thus a potential drug for cancer treatment because it demonstrated anti-angiogenic and anti-invasive properties.

Promising noninvasive cellular phenotype in prostate cancer cells knockdown of matrix metalloproteinase 9

Cell surface interaction of CD44 and MMP9 increases migration and invasion of PC3 cells. We show here that stable knockdown of MMP9 in PC3 cells switches CD44 isoform expression from CD44s to CD44v6 which is more glycosylated. These cells showed highly adhesive morphology with extensive cell spreading which is due to the formation of focal adhesions and well organized actin-stress fibers. MMP9 knockdown blocks invadopodia formation and matrix degradation activity as well. However, CD44 knockdown PC3 cells failed to develop focal adhesions and stress fibers; hence these cells make unstable adhesions. A part of the reason for these changes could be caused by silencing of CD44v6 as well. Immunostaining of prostate tissue microarray sections illustrated significantly lower levels of CD44v6 in adenocarcinoma than normal tissue. Our results suggest that interaction between CD44 and MMP9 is a potential mechanism of invadopodia formation. CD44v6 expression may be essential for the protection of non-invasive cellular phenotype. CD44v6 decrease may be a potential marker for prognosis and therapeutics.

Inactivation of ATM/ATR DNA damage checkpoint promotes androgen induced chromosomal instability in prostate epithelial cells

The ATM/ATR DNA damage checkpoint functions in the maintenance of genetic stability and some missense variants of the ATM gene have been shown to confer a moderate increased risk of prostate cancer. However, whether inactivation of this checkpoint contributes directly to prostate specific cancer predisposition is still unknown. Here, we show that exposure of non-malignant prostate epithelial cells (HPr-1AR) to androgen led to activation of the ATM/ATR DNA damage response and induction of cellular senescence. Notably, knockdown of the ATM gene expression in HPr-1AR cells can promote androgen-induced TMPRSS2: ERG rearrangement, a prostate-specific chromosome translocation frequently found in prostate cancer cells. Intriguingly, unlike the non-malignant prostate epithelial cells, the ATM/ATR DNA damage checkpoint appears to be defective in prostate cancer cells, since androgen treatment only induced a partial activation of the DNA damage response. This mechanism appears to preserve androgen induced autophosphorylation of ATM and phosphorylation of H2AX, lesion processing and repair pathway yet restrain ATM/CHK1/CHK2 and p53 signaling pathway. Our findings demonstrate that ATM/ATR inactivation is a crucial step in promoting androgen-induced genomic instability and prostate carcinogenesis.

Integrin αvβ3 and CD44 pathways in metastatic prostate cancer cells support osteoclastogenesis via a Runx2/Smad 5/receptor activator of NF-κB ligand signaling axis

BACKGROUND

Bone loss and pathological fractures are common skeletal complications associated with androgen deprivation therapy and bone metastases in prostate cancer patients. We have previously demonstrated that prostate cancer cells secrete receptor activator of NF-kB ligand (RANKL), a protein essential for osteoclast differentiation and activation. However, the mechanism(s) by which RANKL is produced remains to be determined. The objective of this study is to gain insight into the molecular mechanisms controlling RANKL expression in metastatic prostate cancer cells.

RESULTS

We show here that phosphorylation of Smad 5 by integrin αvβ3 and RUNX2 by CD44 signaling, respectively, regulates RANKL expression in human-derived PC3 prostate cancer cells isolated from bone metastasis. We found that RUNX2 intranuclear targeting is mediated by phosphorylation of Smad 5. Indeed, Smad5 knock-down via RNA interference and inhibition of Smad 5 phosphorylation by an αv inhibitor reduced RUNX2 nuclear localization and RANKL expression. Similarly, knockdown of CD44 or RUNX2 attenuated the expression of RANKL. As a result, conditioned media from these cells failed to support osteoclast differentiation in vitro. Immunohistochemistry analysis of tissue microarray sections containing primary prostatic tumor (grade2-4) detected predominant localization of RUNX2 and phosphorylated Smad 5 in the nuclei. Immunoblotting analyses of nuclear lysates from prostate tumor tissue corroborate these observations.

CONCLUSIONS

Collectively, we show that CD44 signaling regulates phosphorylation of RUNX2. Localization of RUNX2 in the nucleus requires phosphorylation of Smad-5 by integrin αvβ3 signaling. Our results suggest possible integration of two different pathways in the expression of RANKL. These observations imply a novel mechanistic insight into the role of these proteins in bone loss associated with bone metastases in patients with prostate cancer.

No evidence for infection of UK prostate cancer patients with XMRV, BK virus, Trichomonas vaginalis or human papilloma viruses

The prevalence of specific infections in UK prostate cancer patients was investigated. Serum from 84 patients and 62 controls was tested for neutralisation of xenotropic murine leukaemia virus-related virus (XMRV) Envelope. No reactivity was found in the patient samples. In addition, a further 100 prostate DNA samples were tested for XMRV, BK virus, Trichomonas vaginalis and human papilloma viruses by nucleic acid detection techniques. Despite demonstrating DNA integrity and assay sensitivity, we failed to detect the presence of any of these agents in DNA samples, bar one sample that was weakly positive for HPV16. Therefore we conclude that these infections are absent in this typical cohort of men with prostate cancer.

Human papillomavirus 16 or 18 infection and prostate cancer risk: a meta-analysis

OBJECTIVE

Whether the oncogenic human papillomavirus (HPV) infection, especially infection with the most common subtypes 16 or 18, is related to prostate carcinogenesis remains conflicting. A meta-analysis with updated data was performed to obtain a more precise estimate of the association between them.

METHODS

Eligible studies were retrieved via both computer searches and review of references. The relation of HPV-16 or HPV-18 infection to prostate cancer (PC) was quantified separately. Stratified analyses based on HPV detection methods and geographic regions were also performed. Estimates of OR with 95% CI were summarized using the fixed-effect or random-effect models as appropriate.

RESULTS

Twenty-five eligible studies were retrieved. All the 25 studies were assigned for exploring the relation of HPV-16 infection to PC, while 13 studies provided additional information on HPV-18 simultaneously. In the overall estimates, the pooled OR indicated no significant increase of PC risk related with either HPV-16 (OR 1.09; 95% CI 0.97-1.23; P(heterogeneity) = 0.135) or HPV-18 (OR 1.05; 95% CI 0.89-1.24; P(heterogeneity) = 0.314) infection. Further quantitative assay of stratified data could also not yield any significant result, except the stratified analysis on HPV-16 DNA detection, which revealed higher HPV-16 DNA prevalence in PC cases (OR 1.54; 95% CI 1.07-2.20; P(heterogeneity) = 0.130).

CONCLUSIONS

Even though the overall estimates did not provide a supportive evidence for the causal role of HPV in prostate carcinogenesis, higher HPV-16 DNA prevalence in PC cases from the stratified analysis still indicated a potential association between HPV infection and PC risk in our meta-analysis.

DNA fingerprinting tags novel altered chromosomal regions and identifies the involvement of SOX5 in the progression of prostate cancer

Identification of genomic alterations associated with the progression of prostate cancer may facilitate the better understanding of the development of this highly variable disease. Matched normal, premalignant high-grade prostatic intraepithelial neoplasia and invasive prostate carcinoma cells were procured by laser capture microdissection (LCM) from human radical prostatectomy specimens. From these cells, comparative DNA fingerprints were generated by a modified PCR-based technique called scanning of microdissected archival lesion (SMAL)-PCR. Recurrent polymorphic fingerprint fragments were used in tagging altered chromosomal regions. Altered regions were found at cytobands 1p31.3, 1q44, 2p23.1, 3p26.3, 3q22.3, 4q22.3, 4q35.2, 5q23.2, 8q22.3, 8q24.13, 9q21.3, 9q22.32, 10q11.21, 11p13, 12p12.1, 13q12.1, 16q12.2 and 18q21.31. Candidate genes in the surrounding area that may possibly harbor mutations that change normal prostatic cells to progress into their tumor stages were proposed. Of these fragments, a 420 bp alteration, absent in all 26 normal samples screened, was observed in 2 tumors. This fragment was cloned, sequenced and localized to chromosome 12p12.1. Within this region, candidate gene sex determining region Y-box 5 (SOX5) was proposed. Further studies of SOX5 in cell lines, xenografts and human prostate specimens, at both the RNA and protein levels, found overexpression of the gene in tumors. This overexpression was then subsequently found by fluorescent in situ hybridization to be caused by amplification of the region. In conclusion, our results suggest LCM coupled with SMAL-PCR DNA fingerprinting is a useful method for the screening and identification of chromosomal regions and genes associated with cancer development. Further, overexpression of SOX5 is associated with prostate tumor progression and early development of distant metastasis.

[Detection of papillomavirus DNA in the prostate: a virus with underestimated clinical relevance?]

BACKGROUND

Human papillomaviruses (HPV) are the most frequent pathogens of sexually transmitted diseases. They have been associated with an increased incidence of several anogenital tumors. Whether oncogenic HPV are involved in the pathogenesis of prostate cancer has been a subject of great controversy. This study's purpose was to investigate the association between HPV infection and prostate cancer (PCA).

MATERIAL AND METHODS

The study included 213 consecutive patients with an average age of 65.7 (+/-8.4) years. Within the framework of transrectal, ultrasonic-guided multibiopsy of the prostate, one additional core was examined by means of polymerase chain reaction (PCR) in relation to bacterial, fungal, and viral (including HPV) DNA, with subsequent DNA sequencing. The collected data were correlated with the histological results and with diverse clinical variables. The influence of several predictors for the existence of PCA was verified with a logistic regression model.

RESULTS

No general bacterial DNA (16S rDNA) was detected. Of the 213 patients, 145 (68.1%) showed HPV DNA. In 64% (n=137), high-risk HPV DNA were depicted; these were 18% of the total in each case of HPV genotypes 16 and 18. From our examinations, no significant positive correlation existed between the HPV evidence and the histologically verified PCA that was found in 23.5% of the patients (n=50; odds ratio 1.45; 95% confidence interval 0.71-2.91). The BK virus was not found in any of the cores confirmed through PCR.

CONCLUSION

Although no positive correlation between HPV infection and PCA existed in our study, data from the literature suggest an influence of the papillomavirus on PCA oncogenesis. Future studies should highlight to what extent HPV DNA is inserted in the genome of prostate cells and is able to cause subsequent malignant transformation of particular genes.

CDC25A functions as a novel Ar corepressor in prostate cancer cells

Androgen receptor (AR) is a ligand-dependent transcription factor and its activity is regulated by numerous AR coregulators. Aberrant expression of AR coregulators in prostate cancer cells has an important role in the development and progression of prostate cancer. We report here that CDC25A, a cell cycle-promoting phosphatase over-expressed in a number of cancers, functions as an AR coregulator suppressing the AR transcriptional activity. In this study, we found that CDC25A is upregulated in human prostate cancer and its expression level is positively associated with the Gleason score and disease metastasis. More importantly, we showed that CDC25A can physically interact with AR through its putative catalytic domain. In addition, ectopic expression of CDC25A in prostate cancer cell lines suppresses PSA and Probasin promoter activities significantly, indicating that CDC25A may function as an AR corepressor. This was further confirmed by knockdown of endogenous CDC25A expression using small interfering RNA (siRNA), which resulted in upregulation of PSA promoter activity. Moreover, a truncated mutant that does not interact with AR fails to suppress the PSA promoter activity, indicating that CDC25A downregulates androgen-responsive promoter by physically interacting with AR. Taken together, our results demonstrated a novel function of CDC25A in the regulation of androgen signaling in human prostate cancer cells.

p16INK4a downregulation is involved in immortalization of primary human prostate epithelial cells induced by telomerase

Prostate cancer is a major cause of cancer death among male population. Therefore, development of appropriate model systems is critical for understanding the molecular basis of prostate cancer progression. In this study, introduction of human telomerase (hTERT) into normal human prostate epithelial cells (PrECs) renders them higher telomerase activity, elongated telomere length and an extended proliferative lifespan. The immortal mass culture of PrEC-hTERT cell line with stabilized telomere length has been established using hTERT transfection. However, activation of hTERT alone appears to be insufficient for immortalization of PrEC cells because methylation of p16(INK4a) promoter has been found to be involved in the immortalization process. p53 was functionally intact and no mutations of p53 gene were identified in the immortalized PrECs. In addition, the immortal PrECs show a near diploid complement of chromosomes albeit a few reciprocal and non-reciprocal translocations are identified. They are anchorage dependent and do not form tumors in immunosuppressed host animals. Therefore, premalignantly transformed human PrECs provide a valuable model for prostate cancer research.

Involvement of human papillomavirus infections in prostate cancer progression

High-risk human papillomaviruses (HPVs) are sexually transmitted and have been associated with several human carcinomas especially cervical and colorectal. On the other hand, a small number of studies have examined the presence of high-risk HPV in human prostate cancer tissues. Currently, the presence and role of high-risk HPV infections in prostate carcinogenesis remain unclear because of the limited number of investigations. This raises the question whether high-risk HPV infections play any role in human prostate cancer development. However, other investigators and our group were able to immortalize normal and cancer prostate epithelial cells in vitro by E6/E7 of HPV type 16. In this paper, we propose the hypothesis that normal and cancer prostate epithelial cells are susceptible to persistent HPV infections; therefore, high-risk HPV infections play an important role in the progression of prostate cancer. We believe that an international collaboration of epidemiological studies and more molecular biology investigations are necessary to answer these important questions.

Corneal epithelial cell cultures as a tool for research, drug screening and testing

Understanding of visual system function and the development of new therapies for corneal diseases and damages depend upon comprehension of the biological roles of the tissue. The in vitro cultivation of corneal epithelial cells and cell lines derived from them has become a powerful tool to analyze and understand such issues. Currently, researchers have developed well-defined and precisely described culture protocols and a collection of corneal epithelial cell lines. These cell lines have been obtained through different experimental approaches: (1) the ectopic expression of oncogenes, (2) the inactivation of p16 and p53 pathways and hTERT expression, and (3) the spontaneous establishment after serial cultivation of cells. The advantages or disadvantages for these approaches are discussed. In conclusion, the availability of several culture protocols and immortalized cell lines that express corneal epithelial phenotype will be useful for investigating issues such as gene regulation and tissue development, or for validating alternative methods in toxicology.

Identification of a Novel Inhibitor of Differentiation-1 (ID-1) Binding Partner, Caveolin-1, and Its Role in Epithelial-Mesenchymal Transition and Resistance to Apoptosis in Prostate Cancer Cells

Recently, ID-1 (inhibitor of differentiation/DNA binding) is suggested as an oncogene and is reported to promote cell proliferation, invasion, and survival in several types of human cancer cells through multiple signaling pathways. However, how Id-1 interacts with these pathways and the immediate downstream effectors of the Id-1 protein are not known. In this study, using a yeast two-hybrid screening technique, we identified a novel Id-1-interacting protein, caveolin-1 (Cav-1), a cell membrane protein, and a positive regulator of cell survival and metastasis in prostate cancer. Using an immunoprecipitation method, we found that the helix-loop-helix domain of the Id-1 protein was essential for the physical interaction between Id-1 and Cav-1. In addition, we also demonstrated that the physical interaction between Id-1 and Cav-1 played a key role in the epithelial-mesenchymal transition and increased cell migration rate as well as resistance to taxol-induced apoptosis in prostate cancer cells. Furthermore, our results revealed that this effect was regulated by Id-1-induced Akt activation through promoting the binding activity between Cav-1 and protein phosphatase 2A. Our study demonstrates a novel Id-1 binding partner and suggests a molecular mechanism that mediates the function of Id-1 in promoting prostate cancer progression through activation of the Akt pathway leading to cancer cell invasion and resistance to anticancer drug-induced apoptosis.

Alterations in the expression of inhibitors of apoptosis during differentiation of prostate epithelial cells

OBJECTIVE

To investigate alterations in the apoptotic phenotype, specifically the inhibitors of apoptosis (IAP) family, in prostate epithelial cells after differentiation from an apoptotic-resistant basal cell to an apoptotic-susceptible secretory cell.

MATERIALS AND METHODS

Cells of the immortalized human prostate epithelial line HPr-1AR were cultured with and with no 5alpha-dihydrotestosterone (DHT) to drive differentiation. Western blotting and reverse transcription-polymerase chain reaction (RT-PCR) were used to determine changes in differentiation markers such as cytokeratins (CK) 14 and 18, and in XIAP, cIAP-1 and cIAP-2. Flow cytometry was used to assess viability and apoptosis, by propidium iodide DNA staining of the cells during differentiation.

RESULTS

Morphological changes and the increased CK-18 and decreased CK-14 expression confirmed differentiation of cells towards a secretory phenotype. Real-time PCR and Western blotting confirmed the expression of the IAPs in the HPr-1AR cells. There was a time-dependent decrease in the mRNA expression of XIAP, cIAP-1 and cIAP-2 after treatment with DHT. Differentiation also resulted in decreased cIAP-1 and XIAP protein expression, but cIAP-2 remained unchanged. Spontaneous apoptosis was significantly increased during cellular differentiation.

CONCLUSION

We show for the first time that differentiation of HPr-1AR prostate epithelial cells results in the development of a transient end-stage cell that might be explained by the loss of the IAP family of proteins.

Id-1 promotes TGF-beta1-induced cell motility through HSP27 activation and disassembly of adherens junction in prostate epithelial cells

Id-1 (inhibitor of differentiation or DNA binding-1) has been positively associated with cell proliferation, cell cycle progression, and invasiveness during tumorigenesis. In addition, Id-1 has been shown to modulate cellular sensitivity to TGF-beta1 (transforming growth factor beta1). Here we demonstrate a novel role of Id-1 in promoting TGF-beta1-induced cell motility in a non-malignant prostate epithelial cell line, NPTX. We found that Id-1 promoted F-actin stress fiber formation in response to TGF-beta1, which was associated with increased cell-substrate adhesion and cell migration in NPTX cells. In addition, this positive effect of Id-1 on TGF-beta1-induced cell motility was mediated through activation of MEK-ERK signaling pathway and subsequent phosphorylation of HSP27 (heat shock protein 27). Furthermore, Id-1 disrupted the adherens junction complex in TGF-beta1-treated cells through down-regulation of E-cadherin, redistribution of beta-catenin, along with up-regulation of N-cadherin. These lines of evidence reveal a novel tumorigenic role of Id-1 through reorganization of actin cytoskeleton and disassembly of cell-cell adhesion in response to TGF-beta1 in human prostate epithelial cells, and suggest that intracellular Id-1 levels might be a determining factor for switching TGF-beta1 from a growth inhibitor to a tumor promoter during prostate carcinogenesis.

MAD2ΔC induces aneuploidy and promotes anchorage-independent growth in human prostate epithelial cells

The mitotic arrest deficient 2 (MAD2) is suggested to play a key role in a functional mitotic checkpoint because of its inhibitory effect on anaphase-promoting complex/cyclosome (APC/C) during mitosis. The binding of MAD2 to mitotic checkpoint regulators MAD1 and Cdc20 is thought to be crucial for its function and loss of which leads to functional inactivation of the MAD2 protein. However, little is known about the biological significance of this MAD2 mutant in human cells. In this study, we stably transfected a C-terminal-deleted MAD2 gene (MAD2DeltaC) into a human prostate epithelial cell line, Hpr-1 and studied its effect on chromosomal instability, cell proliferation, mitotic checkpoint control and soft agar colony-forming ability. We found that MAD2DeltaC was able to induce aneuploidy through promoting chromosomal duplication, which was a result of an impaired mitotic checkpoint and cytokinesis, suggesting a crucial role of MAD2-mediated mitotic checkpoint in chromosome stability in human cells. In addition, the MAD2DeltaC-transfected cells displayed anchorage-independent growth in soft agar after challenged by 7,12-dimethylbenz[A]anthracene (DMBA), demonstrating a cancer-promoting effect of a defective mitotic checkpoint in human cells. Furthermore, the DMBA-induced transformation was accompanied by a complete loss of DNA damage-induced p53 response and activation of the MAPK pathway in MAD2DeltaC cells. These results indicate that a defective mitotic checkpoint alone is not a direct cause of tumorigenesis, but it may predispose human cells to carcinogen-induced malignant transformation. The evidence presented here provides a link between MAD2 inactivation and malignant transformation of epithelial cells.

Reversal of the malignant phenotype of cervical cancer CaSki cells through adeno-associated virus-mediated delivery of HPV16 E7 antisense RNA

Human papillomavirus (HPV) infection is the most important risk factor for the development of cervical cancer. The oncogene E7 from high-risk HPV strains has the ability to immortalize epithelial cells and increase cellular transformation in culture. In this study, we explored the possibility of preventing cervical cancer growth by inhibiting HPV16 E7 expression through gene transfer of an antisense construct. A recombinant adeno-associated virus (rAAV) vector was chosen for the transfer, based on its transfection efficiency, in vivo stability, and lack of detectable pathology. In vitro transfer of an rAAV vector expressing antisense HPV16 E7 (AAV-HPV16E7AS) inhibited cell proliferation, induced apoptosis, reduced cell migration, and restrained in vivo proliferation of HPV16/HPV18-positive cervical cancer CaSki cells. These results indicate that down-regulation of HPV16 E7 with antisense RNA is beneficial in reducing the tumorigenicity of CaSki cells, and rAAV vectors ought to be a new efficient approach for delivering the expression of therapeutic genes.

hTERT-immortalized prostate epithelial and stromal-derived cells: an authentic in vitro model for differentiation and carcinogenesis

Prostate cancer is the most commonly diagnosed type of cancer in men, and there is no available cure for patients with advanced disease. In vitro model systems are urgently required to permit the study of human prostate cell differentiation and malignant transformation. Unfortunately, human prostate cells are particularly difficult to convert into continuously growing cultures. We report here the successful immortalization without viral oncogenes of prostate epithelial cells and, for the first time, prostate stromal cells. These cells exhibit a significant pattern of authentic prostate-specific features. In particular, the epithelial cell culture is able to differentiate into glandular buds that closely resemble the structures formed by primary prostate epithelial cells. The stromal cells have typical characteristics of prostate smooth muscle cells. These immortalized cultures may serve as a unique experimental platform to permit several research directions, including the study of cell-cell interactions in an authentic prostate microenvironment, prostate cell differentiation, and most significantly, the complex multistep process leading to prostate cell transformation.

Tissue engineered cartilage using human articular chondrocytes immortalized by HPV-16 E6 and E7 genes

Chondrocytes are useful as a cell culture system for studying arthritic degeneration in tissue engineered cartilage. However, primary chondrocytes have short in vitro lifespan and rapid shift of collagen phenotype. In this study, we used a high dosage of retroviral vector LXSN16E6E7 to transduce human primary chondrocytes and obtained an actively proliferating cell line, designated hPi, which expresses HPV-16 E6/E7 mRNA in early passages. Parental primary chondrocytes cease to grow after five passages, whereas hPi could be propagated beyond 100 passages without requiring additional cell elements in defined medium. After 48 passages, hPi can also give many profiles similar to those of parental primary chondrocyte, including type II collagen in mRNA and protein level, aggrecan in mRNA level, lacunae in type I collagen matrices, and morphology with GAG-specific Alcian blue staining. hPi has shown neoplastic transformation, as examined by NOD-SCID mice tumorigenicity assays for 3 months. Our results indicated that human primary chondrocytes could be immortalized by transduction with HPV-16 E6/E7, preserving stable cartilage-specific differentiation markers. The established chondrocyte cell line could provide a novel model to engineer cartilage in vitro and in vivo for cartilage repair research and clinical application.

Epigenetic inactivation of CHFR in nasopharyngeal carcinoma through promoter methylation

Chromosomal instability (CIN) is a cytogenetic hallmark of human cancers. Increasing evidence suggests that impairment of mitotic checkpoint is causally associated with CIN. CHFR is one of the mitotic checkpoint regulators and it delays chromosome condensation in response to mitotic stress. Epigenetic inactivation of CHFR through promoter CpG hypermethylation may lead to CIN and has been reported in several human cancers. In this study, we investigated the CHFR gene expression in a panel of nasopharyngeal carcinoma (NPC), prostate, ovarian, and breast cancer cell lines. We found that the expression of CHFR mRNA was significantly decreased or undetectable in all eight NPC cell lines as well as three human NPC xenografts, whereas non-malignant nasopharyngeal cell lines and other cancer cell lines tested expressed CHFR at relatively high levels. Hypermethylation of CHFR promoter region was also strongly correlated with decreased CHFR expression in NPC cell lines and xenografts. Treatment with a methyltransferase inhibitor, 5-aza-2'-deoxycytidine, led to restoration of CHFR expression in NPC cell lines. More importantly, hypermethylation of CHFR promoter region was detected in 61.1% (22 out of 36) of primary NPC tumors while it was absent in non-malignant tissues. These findings suggest that downregulation of CHFR is a common event in NPC cells which may be due to hypermethylation of the gene promoter region.

Androgen receptor (AR) expression in AR-negative prostate cancer cells results in differential effects of DHT and IGF-I on proliferation and AR activity between localized and metastatic tumors

BACKGROUND

Two features of the progression from organ-confined to metastatic prostate cancer are dysregulation of the androgen receptor (AR) and a decrease in insulin-like growth factor-type-I receptor (IGF-IR) expression. The purpose of this study was to determine the effect of changes in IGF-IR expression on AR activity.

METHODS

M12 human prostate cells were stably transfected with an AR expression construct to produce the M12-AR parental (PAR) cell line. PAR cells were implanted orthotopically into nude mice and M12-AR primary (PRI) cell lines were derived from intraprostatic tumors and metastatic cell lines (MET) were derived from PRI tumors that had metastasized to diaphragm or lung.

RESULTS

Tumor formation in the prostate by PAR cells was decreased significantly compared to M12 controls. PAR, PRI, and MET cells expressed equivalent amounts of AR protein; however, IGF-IR expression was increased significantly in PAR and PRI cells. IGF-IR expression decreased in MET lines to the levels seen in M12 control cells. IGF-I significantly enhanced dihydrotestosterone (DHT)-stimulated, but not basal, AR transcriptional activity in PRI cells. In MET cells, IGF-I significantly suppressed DHT-stimulated transcriptional activity. In MET cells in which the IGF-IR was re-expressed from a retroviral vector, the effects of DHT and IGF-I on AR activity were similar to those seen in PRI cells.

CONCLUSIONS

This study demonstrates that the changes in IGF-IR expression exhibited by this model of metastatic progression cause significant alterations in AR signaling and suggest that this interaction may be an important aspect of the changes seen in AR function in disease progression in vivo.

Prostate Development and Carcinogenesis

The process involved in the development and carcinogenesis of the prostate gland is complex. During early prostate development, the androgenic hormone from embryonic testicles is required for ductal formation, growth, and branching morphogenesis of the prostate gland. From this early stage, interactions between the epithelium and mesenchyme become firmly established through paracrine influence (i.e., growth factors) from mesenchyme (stroma), in response to testosterone, acting on epithelium to stimulate its proliferation, morphogenetic differentiation, and function. In return, the epithelium also exerts its paracrine effects on mesenchyme by regulating the differentiation and specific organizational pattern of its stromal smooth muscle. In a normal adult prostate, the maintenance of normal glandular structure and function is dependent not only on the constant presence of testosterone, but also on a normal intact and stable stroma. This chapter will concentrate first on factors involved in the normal development of the prostate gland and then on the aberrant changes in the homeostatic balance arising either from within (i.e., mutations) or outside (i.e., changes in hormonal balance) that result in derangements of the prostate gland. Finally, environmental and genetic factors that lead to prostate carcinogenesis including activation of oncogenes and mutations of tumor suppressor genes are also discussed.

Down-regulation of Id-1 expression is associated with TGF beta 1-induced growth arrest in prostate epithelial cells

Transforming growth factor beta1 (TGF beta 1) plays important roles in the regulation of cell growth and differentiation in both normal and malignant prostate epithelial cells. Although certain pathways have been suggested, the mechanisms responsible for the action of TGF beta 1 are not well understood. In the present study, using a human papilloma virus 16 E6/E7 immortalized prostate epithelial cell line, HPr-1, we report that TGF beta 1 was able to suppress the expression of Id-1, a helix-loop-helix (HLH) protein, which plays important roles in the inhibition of cell differentiation and growth arrest. In addition, a decrease at both Id-1 mRNA and protein expression levels was associated with TGF beta 1-induced growth arrest and differentiation, indicating that Id-1 may be involved in TGF beta 1 signaling pathway. The fact that up-regulation of p21(WAF1), one of the downstream effectors of Id-1, was observed after exposure to TGF beta 1 further indicates the involvement of Id-1 in the TGF beta 1-induced growth arrest in HPr-1 cells. However, increased expression of p27(KIP1) was also observed in the TGF beta 1-treated cells, suggesting that in addition to down-regulation of Id-1, other factors may be involved in the TGF beta 1-induced cell growth arrest and differentiation in prostate epithelial cells. Our results provide evidence for the first time that TGF beta 1 may be one of the upstream regulators of Id-1.

Establishment and characterization of an immortalized human oviductal cell line

Human oviductal cells stimulate embryo development in vitro partly by the production of embryotrophic glycoproteins. The identity of these glycoproteins is not yet known mainly because oviductal samples are limited and that the cultured parental oviductal cells cannot produce sufficient amount of embryotrophic factors for characterization. In this study, human oviductal epithelial cells (OE) were immortalized by HPV 16 E6/E7 open reading frame (ORF) by retroviral expression. The characteristics of this immortalized cell line (OE-E6/E7) were compared to the parental OE. HPV 16 E6/E7 DNA was found only in OE-E6/E7 but not in OE. Human oviduct-specific glycoprotein, estrogen receptors, and cytokeratin were found in both cell types. Both OE and OE-E6/E7 possessed telomerase activities but the former had much lower activity. OE-E6/E7 also produced glycoproteins with chromatographic behavior similar to the embryotrophic glycoproteins derived from OE. These results showed that OE-E6/E7 retained a number of characteristics of OE. The development of preimplantation mouse embryo was significantly better after coculture with OE-E6/E7 when compared to medium alone culture in term of blastulation rates (52% vs. 32%) and blastocyst diameter (113.0 +/- 2.07 microm vs. 83.9 +/- 5.23 microm). This immortalized cell line can be used as a continuous and stable in vitro system for the study of the oviductal embryotrophic activity. Mol. Reprod. Dev. 59: 400-409, 2001.

Mutations within the tumour suppressor gene p53 are not confined to a late event in prostate cancer progression. a review of the evidence

Mutations in the p53 tumour suppressor gene are generally believed to be a late event in the progression of prostate cancer, and are associated with androgen independence, metastasis, and a worse prognosis. In this review, we examine the current literature available on p53 mutations and focus on stages A (T1) and B (T2) of prostate cancer. We report here that p53 mutations can be found in approximately one third of prostate cancers that are clinically localized to the prostate. In addition, high levels of p53 mutation are found in normal prostate tissue of prostate cancer patients, prostatic intraepithelial neoplasia, and benign prostatic hyperplasia. The limitations of techniques used to determine p53 mutations are discussed, as well as other modes of p53 loss in early stage prostate cancer.

Vitamin C augments chemotherapeutic response of cervical carcinoma HeLa cells by stabilizing P53

Human Papilloma Virus (HPV) is associated in most instances with cervical cancer. The HPV oncoproteins target P53 protein for degradation, leading to deregulation of cell cycle. We investigated whether stabilization of P53 in cervical cancer cells, by downregulating HPV transcription would restore the apoptotic ability of these cells. Our findings show that vitamin C downregulates the redox sensitive transcription factor AP-1 and decreases one of its transcription targets HPV E6, and stabilizes P53. This was associated with an increase in Bax and decrease in Bcl-2 and telomerase activity. Accumulation of P53 and its target gene bax then sensitized HeLa cells to cell-cycle arrest, cell death/apoptosis induced by cisplatin, and etoposide. Increasing drug sensitivity of cervical carcinoma cells by stabilizing P53 using vitamin C is a novel approach and has potential clinical relevance.

Telomerase activation, cellular immortalization and cancer

The maintenance of specialized nucleoprotein structures termed telomeres is essential for chromosome stability. Without new synthesis of telomeres at chromosome ends the chromosomes shorten with progressive cell division, eventually triggering either replicative senescence or apoptosis when telomere length becomes critically short. The regulation of telomerase activity in human cells plays a significant role in the development of cancer. Telomerase is tightly repressed in the vast majority of normal human somatic cells but becomes activated during cellular immortalization and in cancers. While the mechanisms for telomerase activation in cancers have not been fully defined, they include telomerase catalytic subunit gene (hTERT) amplification and trans-activation of the hTERT promoter by the myc oncogene product. Ectopic expression of hTERT is sufficient to restore telomerase activity in cells that lack the enzyme and can immortalize many cell types. Understanding telomerase biology will eventually lead to several clinically relevant telomerase-based therapies. These applications include inhibiting or targeting telomerase as a novel antineoplastic strategy and using cells immortalized by telomerase for therapeutic applications.

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).

Telomerase activation and incidence of HPV in human gastrointestinal tumors in North Indian population

The present study was initiated with the objective of finding out the role of possible factors in the etiology of gastrointestinal tract cancers. HPV-DNA was detected in 62.5% (25/40) of the patients by PCR. Telomerase activity as shown by TRAP-ELISA assay was detected in 82.5% (33/40) of the tumor samples and absent in 85.7% (30/35) of the normal samples taken from the same patients. As many as 53.6% (15/28) of the invasive cases were positive both for telomerase activity and for HPV, while 39.3% (11/28) of them, although indicating telomerase expression, showed no signal for HPV. This suggests that activation of telomerase could be by a pathway independent of HPV activation, although both parameters could act as diagnostic and prognostic markers for gastrointestinal tract cancers.

Retrovirus-mediated delivery of HPV16 E7 antisense RNA inhibited tumorigenicity of CaSki cells

OBJECTIVE

In cervical cancer, high-risk human papillomavirus (HPV) genes are expressed solely in cancerous cells and have been proposed to be the most important etiological factors for cervical cancer, thus making them suitable targets for gene therapy. In this study, we aim to inactivate the HPV16 E7 in CaSki cells and test the possibility of reducing the tumorigenicity of these cells.

METHODS

The full-length HPV16 E7 cDNA was cloned in the pBabe-puro or pWZL-Hygro retrovirus vector in reverse orientation and was stably transfected into CaSki cells by replication-defective retrovirus infection giving rise to CaSki-E7AS and CaSki-E7AS2X cells. Immunoprecipitation/Western analysis and real-time RT-PCR were performed to document the levels of HPV16 E7 gene product. Flow cytometry was performed to study changes in the cell cycle in response to reduced E7 protein. The expression of bcl-2, RB, and E2F-1 was studied using Western blot analysis. Tumorigenicity of CaSki, CaSki-E7AS, and CaSki-E7AS2X cells was assayed with subepidermal tumor growth in nude mice.

RESULTS

We have documented that the delivery of the antisense gene construct resulted in the reduction of HPV16 E7 protein expression and cell proliferation in CaSki cells. Furthermore, we demonstrated that these changes were accompanied by cell cycle arrest, up-regulation of RB, and down-regulation of E2F-1 and bcl-2 proteins. More importantly, dose-dependent transduction of the antisense HPV16E7 construct was able to inhibit and/or retard the tumorigenicity of CaSki cells in vivo.

CONCLUSIONS

Down-regulation of HPV16 E7 with antisense RNA is beneficial in reducing the tumorigenicity of CaSki cells and can potentially be useful for HPV-associated malignancy gene therapy.