Infrequent RAS oncogene mutations in human prostate cancer

Integrative Molecular Analyses of the MD Anderson Prostate Cancer Patient-derived Xenograft (MDA PCa PDX) Series

PURPOSE

Develop and deploy a robust discovery platform that encompasses heterogeneity, clinical annotation, and molecular characterization and overcomes the limited availability of prostate cancer models. This initiative builds on the rich MD Anderson (MDA) prostate cancer (PCa) patient-derived xenograft (PDX) resource to complement existing publicly available databases by addressing gaps in clinically annotated models reflecting the heterogeneity of potentially lethal and lethal prostate cancer.

EXPERIMENTAL DESIGN

We performed whole-genome, targeted, and RNA sequencing in representative samples of the same tumor from 44 PDXs derived from 38 patients linked to donor tumor metadata and corresponding organoids. The cohort includes models derived from different morphologic groups, disease states, and involved organ sites (including circulating tumor cells), as well as paired samples representing heterogeneity or stages before and after therapy.

RESULTS

The cohort recapitulates clinically reported alterations in prostate cancer genes, providing a data resource for clinical and molecular interrogation of suitable experimental models. Paired samples displayed conserved molecular alteration profiles, suggesting the relevance of other regulatory mechanisms (e.g., epigenomic) influenced by the microenvironment and/or treatment. Transcriptomically, models were grouped on the basis of morphologic classification. DNA damage response-associated mechanisms emerged as differentially regulated between adenocarcinoma and neuroendocrine prostate cancer in a cross-interrogation of PDX/patient datasets.

CONCLUSIONS

We addressed the gap in clinically relevant prostate cancer models through comprehensive molecular characterization of MDA PCa PDXs, providing a discovery platform that integrates with patient data and benchmarked to therapeutically relevant consensus clinical groupings. This unique resource supports robust hypothesis generation and testing from basic, translational, and clinical perspectives.

KRAS, BRAF, PIK3CA mutation frequency of radical prostatectomy samples and review of the literature

OBJECTIVE

The molecular basis of prostate cancer is highly heterogeneous. Our study aimed to perform the mutation analysis of KRAS, BRAF, PIK3CA, and immunohistochemical (IHC) evaluation of EGFR, HER2, p16, and PTEN to demonstrate new areas for targeted therapies.

METHODS

A total of 24 prostatectomy samples diagnosed with adenocarcinoma were analyzed by microarray hybridization. Also, these samples were IHC stained for EGFR, HER2, P16, and PTEN. The cases were divided into two groups based on low and high Gleason scores. All findings were compared with the clinicopathological parameters of the patients.

RESULTS

While KRAS mutation was in 3/24 (12.5%) of our cases, BRAF and PIK3CA mutations were not detected. There was no significant difference between the groups in terms of KRAS mutation frequency. HER2 was immunohistochemically negative in all samples. There was no correlation between EGFR, P16 immunopositivity, and clinicopathological features.

CONCLUSION

KRAS mutation frequency is similar to those in Asian populations. BRAF and PIK3CA mutation frequencies have been reported in the literature in the range of 0-15% and 0-10.4%, respectively, consistent with our study findings. HER2 immunoexpression is a controversial issue in the literature. EGFR and p16 expressions may not correlate with the stage.

Interaction between prostate cancer cells and prostate fibroblasts promotes accumulation and proteolytic processing of basement membrane proteins

BACKGROUND

Tumor microenvironment or stroma has the potency to regulate the behavior of malignant cells. Fibroblast-like cells are abundant in tumor stroma and they are also responsible for the synthesis of many extracellular matrix components. Fibroblast-cancer cell interplay can modify the functions of both cell types.

METHODS

We applied mass spectrometry and proteomics to unveil the matrisome in 3D spheroids formed by DU145 prostate cancer cells, PC3 prostate cancer cells, or prostate-derived fibroblasts. Similarly, DU145/fibroblast and PC3/fibroblast coculture spheroids were also analyzed. Western blot analysis and immunofluorescence were used to confirm the presence of specific proteins in spheroids. Cancer dissemination was studied by utilizing "out of spheroids" migration and invasion assays.

RESULTS

In the spheroid model cancer cell-fibroblast interplay caused remarkable changes in the extracellular matrix and accelerated the invasion of DU145 cells. Fibroblasts produced structural matrix proteins, growth factors, and matrix metalloproteinases. In cancer cell/fibroblast cocultures basement membrane components, including laminins (α3, α5, β2, and β3), heparan sulfate proteoglycan (HSPG2 gene product), and collagen XVIII accumulated in a prominent manner when compared with spheroids that contained fibroblasts or cancer cells only. Furthermore, collagen XVIII was intensively processed to different endostatin-containing isoforms by cancer cell-derived cathepsin L.

CONCLUSIONS

Fibroblasts can promote carcinoma cell dissemination by several different mechanisms. Extracellular matrix and basement membrane proteins provide attachment sites for cell locomotion promoting adhesion receptors. Growth factors and metalloproteinases are known to accelerate cell invasion. In addition, cancer cell-fibroblast interplay generates biologically active fragments of basement membrane proteins, such as endostatin.

MAZ promotes prostate cancer bone metastasis through transcriptionally activating the KRas-dependent RalGEFs pathway

Background

Clinically, prostate cancer (PCa) exhibits a high avidity to metastasize to bone. Myc-associated zinc-finger protein (MAZ) is a well-documented oncogene involved in the progression and metastasis of multiple cancer types, even in PCa. However, the clinical significance and biological roles of MAZ in bone metastasis of PCa remain unclear.

Methods

MAZ expression was examined in PCa tissues with bone metastasis, PCa tissues without bone metastasis and metastatic bone tissues by real-time PCR and immunohistochemistry (IHC), respectively. Statistical analysis was performed to evaluate the clinical correlation between MAZ expression and clinicopathological features and bone metastasis-free survival in PCa patients. Biological roles of MAZ in bone metastasis of PCa were investigated both in vitro by transwell assay, and in vivo by a mouse model of left cardiac ventricle inoculation. The bioinformatics analysis, western blot, pull-down assays, chromatin immunoprecipitation (ChIP) and luciferase reporter assays were applied to demonstrate and examine the relationship between MAZ and its potential downstream signalling pathway. TaqMan copy number assay was performed to identify the underlying mechanism responsible for MAZ overexpression in PCa tissues.

Results

MAZ expression is elevated in PCa tissues with bone metastasis compared with that in PCa tissues without bone metastasis, and is further increased in metastatic bone tissues. High expression of MAZ positively correlates with poor overall and bone metastasis-free survival in PCa patients. Upregulating MAZ elevates, while silencing MAZ represses the invasion and migration abilities of PCa cells in vitro and bone metastasis ability in vivo. Our results further reveal that MAZ promotes bone metastasis of PCa dependent on KRas signalling, although MAZ transcriptionally upregulates KRas and HRas expression, where the Ral guanine nucleotide exchange factor (RalGEF) signaling is responsible for the different roles of KRas and HRas in mediating the pro-bone metastasis of MAZ in PCa. Finally, our results indicate that recurrent gains contribute to MAZ overexpression in a small portion of PCa tissues.

Conclusion

These results indicate that the MAZ/Kras/ RalGEF signalling axis plays a crucial role in promoting PCa cell bone metastasis, suggesting a potential therapeutic utility of MAZ in bone metastasis of PCa.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1374-x) contains supplementary material, which is available to authorized users.

Arsenic Alters Exosome Quantity and Cargo to Mediate Stem Cell Recruitment Into a Cancer Stem Cell-Like Phenotype

Inorganic arsenic is a human carcinogen that can target the prostate. Accumulating evidence suggests arsenic can disrupt stem cell (SC) dynamics during the carcinogenic process. Previous work demonstrated arsenic-transformed prostate epithelial (CAsE-PE) cells can recruit prostate SCs into rapidly acquiring a cancer SC (CSC) phenotype via the secretion of soluble factors. Exosomes are small, membrane-derived vesicles that contain lipids, RNA, and proteins, and actively contribute to cancer initiation and progression when taken up by target cells. Here we hypothesized that CAsE-PE cells are recruiting SCs to a CSC-like phenotype via exosomal signaling. CAsE-PE cells secreted 700% more exosomes than parental RWPE-1 cells. CAsE-PE exosomes were enriched with oncogenic factors, including oncogenes (KRAS, NRAS, VEFGA, MYB, and EGFR), inflammation-related (cyclooxygenase-2, interleukin 1B (IL1B), IL6, transforming growth factor-β, and tumor necrosis factor-A), and apoptosis-related (CASP7, CASP9, and BCL2) transcripts, and oncogenesis-associated microRNAs. When compared with SCs cultured in exosome-depleted conditioned medium (CM), SCs cultured in CM containing CAsE-PE-derived exosomes showed increased (198%) matrix metalloproteinase activity and underwent an epithelial-to-mesenchymal transition in morphology, suggesting an exosome-mediated transformation. KRAS plays an important role in arsenic carcinogenesis. Although KRAS transcript (>24 000%) and protein (866%) levels were elevated in CAsE-PE exosomes, knock-down of KRAS in these cells only partially mitigated the CSC-like phenotype in cocultured SCs. Collectively, these results suggest arsenic impacts both exosomal quantity and cargo. Exosomal KRAS is only minimally involved in this recruitment, and additional factors (eg, cancer-associated miRNAs) likely also play a role. This work furthers our mechanistic understanding of how arsenic disrupts SC dynamics and influences the tumor microenvironment during carcinogenesis.

An aberrant SREBP-dependent lipogenic program promotes metastatic prostate cancer

Lipids, either endogenously synthesized or exogenous, have been linked to human cancer. Here we found that PML is frequently co-deleted with PTEN in metastatic human prostate cancer (CaP). We demonstrated that conditional inactivation of Pml in the mouse prostate morphs indolent Pten-null tumors into lethal metastatic disease. We identified MAPK reactivation, subsequent hyperactivation of an aberrant SREBP prometastatic lipogenic program, and a distinctive lipidomic profile as key characteristic features of metastatic Pml and Pten double-null CaP. Furthermore, targeting SREBP in vivo by fatostatin blocked both tumor growth and distant metastasis. Importantly, a high-fat diet (HFD) induced lipid accumulation in prostate tumors and was sufficient to drive metastasis in a nonmetastatic Pten-null mouse model of CaP, and an SREBP signature was highly enriched in metastatic human CaP. Thus, our findings uncover a prometastatic lipogenic program and lend direct genetic and experimental support to the notion that a Western HFD can promote metastasis.

Deregulated PP1α phosphatase activity towards MAPK activation is antagonized by a tumor suppressive failsafe mechanism

The mitogen-activated protein kinase (MAPK) pathway is frequently aberrantly activated in advanced cancers, including metastatic prostate cancer (CaP). However, activating mutations or gene rearrangements among MAPK signaling components, such as Ras and Raf, are not always observed in cancers with hyperactivated MAPK. The mechanisms underlying MAPK activation in these cancers remain largely elusive. Here we discover that genomic amplification of the PPP1CA gene is highly enriched in metastatic human CaP. We further identify an S6K/PP1α/B-Raf signaling pathway leading to activation of MAPK signaling that is antagonized by the PML tumor suppressor. Mechanistically, we find that PP1α acts as a B-Raf activating phosphatase and that PML suppresses MAPK activation by sequestering PP1α into PML nuclear bodies, hence repressing S6K-dependent PP1α phosphorylation, 14-3-3 binding and cytoplasmic accumulation. Our findings therefore reveal a PP1α/PML molecular network that is genetically altered in human cancer towards aberrant MAPK activation, with important therapeutic implications.

Combined targeting of Arf1 and Ras potentiates anticancer activity for prostate cancer therapeutics

Background

Although major improvements have been made in surgical management, chemotherapeutic, and radiotherapeutic of prostate cancer, many prostate cancers remain refractory to treatment with standard agents. Therefore, the identification of new molecular targets in cancer progression and development of novel therapeutic strategies to target them are very necessary for achieving better survival for patients with prostate cancer. Activation of small GTPases such as Ras and Arf1 is a critical component of the signaling pathways for most of the receptors shown to be upregulated in advanced prostate cancer.

Methods

The drug effects on cell proliferation were measured by CellTiter 96® AQueous One Solution Cell Proliferation Assay. The drug effects on cell migration and invasion were determined by Radius™ 24-well and Matrigel-coated Boyden chambers. The drug effects on apoptosis were assessed by FITC Annexin V Apoptosis Detection Kit with 7-AAD and Western blot with antibodies against cleaved PARP and Caspase 3. A NOD/SCID mouse model generated by subcutaneous injection was used to assess the in vivo drug efficacy in tumor growth. ERK activation and tumor cell proliferation in xenografts were examined by immunohistochemistry.

Results

We show that Exo2, a small-molecule inhibitor that reduces Arf1 activation, effectively suppresses prostate cancer cell proliferation by blocking ERK1/2 activation. Exo2 also has other effects, inhibiting migration and invasion of PCa cells and inducing apoptosis. The Ras inhibitor salirasib augments Exo2-induced cytotoxicity in prostate cancer cells partially by enhancing the suppression of ERK1/2 phosphorylation. In a xenograft mouse model of prostate cancer, Exo2 reduces prostate tumor burden and inhibits ERK1/2 activation at a dose of 20 mg/kg. Synergistic treatment of salirasib and Exo2 exhibits a superior inhibitory effect on prostate tumor growth compared with either drug alone, which may be attributed to the more efficient inhibition of ERK1/2 phosphorylation.

Conclusion

This study suggests that simultaneous blockade of Arf1 and Ras activation in prostate cancer cells is a potential targeted therapeutic strategy for preventing prostate cancer development.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-017-0583-4) contains supplementary material, which is available to authorized users.

MicroRNA-34a regulates WNT/TCF7 signaling and inhibits bone metastasis in Ras-activated prostate cancer

Aberrant activation of Ras and WNT signaling are key events that have been shown to be up-regulated in prostate cancer that has metastasized to the bone. However, the regulatory mechanism of combinatorial Ras and WNT signaling in advanced prostate cancer is still unclear. TCF7, a WNT signaling-related gene, has been implicated as a critical factor in bone metastasis, and here we show that TCF7 is a direct target of miR-34a. In samples of prostate cancer patients, miR-34a levels are inversely correlated with TCF7 expression and a WNT dependent gene signature. Ectopic miR-34a expression inhibited bone metastasis and reduced cancer cell proliferation in a Ras-dependent xenograft model. We demonstrate that miR-34a can directly interfere with the gene expression of the anti-proliferative BIRC5, by targeting BIRC5 3′UTR. Importantly, BIRC5 overexpression was sufficient to reconstitute anti-apoptotic signaling in cells expressing high levels of miR-34a. In prostate cancer patients, we found that BIRC5 levels were positively correlated with a Ras signaling signature expression. Our data show that the bone metastasis and anti-apoptotic effects found in Ras signaling-activated prostate cancer cells require miR-34a deficiency, which in turn aids in cell survival by activating the WNT and anti-apoptotic signaling pathways thereby inducing TCF7 and BIRC5 expressions.

Transcriptional Repressor DAXX Promotes Prostate Cancer Tumorigenicity via Suppression of Autophagy

The DAXX transcriptional repressor was originally associated with apoptotic cell death. However, recent evidence that DAXX represses several tumor suppressor genes, including the DAPK1 and DAPK3 protein kinases, and is up-regulated in many cancers argues that a pro-survival role may predominate in a cancer context. Here, we report that DAXX has potent growth-enhancing effects on primary prostatic malignancy through inhibition of autophagy. Through stable gene knockdown and mouse subcutaneous xenograft studies, we demonstrate that DAXX promotes tumorigenicity of human ALVA-31 and PC3 prostate cancer (PCa) cells in vivo. Importantly, DAXX represses expression of essential autophagy modulators DAPK3 and ULK1 in vivo, revealing autophagy suppression as a mechanism through which DAXX promotes PCa tumorigenicity. Furthermore, DAXX knockdown increases autophagic flux in cultured PCa cells. Finally, interrogation of the Oncomine(TM) database suggests that DAXX overexpression is associated with malignant transformation in several human cancers, including prostate and pancreatic cancers. Thus, DAXX may represent a new cancer biomarker for the detection of aggressive disease, whose tissue-specific down-regulation can serve as an improved therapeutic modality. Our results establish DAXX as a pro-survival protein in PCa and reveal that, in the early stages of tumorigenesis, autophagy suppresses prostate tumor formation.

Novel In Vivo model for combinatorial fluorescence labeling in mouse prostate

BACKGROUND

The epithelial layer of prostate glands contains several types of cells, including luminal and basal cells. Yet there is paucity of animal models to study the cellular origin of normal or neoplastic development in the prostate to facilitate the treatment of heterogenous prostate diseases by targeting individual cell lineages.

METHODS

We developed a mouse model that expresses different types of fluorescent proteins (XFPs) specifically in prostatic cells. Using an in vivo stochastic fluorescent protein combinatorial strategy, XFP signals were expressed specifically in prostate of Protein Kinase D1 (PKD1) knock-out, K-Ras(G) (12) (D) knock-in, and Phosphatase and tensin homolog (PTEN) and PKD1 double knock-out mice under the control of PB-Cre promoter.

RESULTS

In vivo XFP signals were observed in prostate of PKD1 knock-out, K-Ras(G) (12) (D) knock-in, and PTEN PKD1 double knock-out mice, which developed normal, hyperplastic, and neoplastic prostate, respectively. The patchy expression pattern of XFPs in neoplasia tissue indicated the clonal origin of cancer cells in the prostate.

CONCLUSIONS

The transgenic mouse models demonstrate combinatorial fluorescent protein expression in normal and cancerous prostatic tissues. This novel prostate-specific fluorescent labeled mouse model, which we named Prorainbow, could be useful in studying benign and malignant pathology of prostate.

An increase in integrin-linked kinase non-canonically confers NF-κB-mediated growth advantages to gastric cancer cells by activating ERK1/2

Background

Increased activity or expression of integrin-linked kinase (ILK), which regulates cell adhesion, migration, and proliferation, leads to oncogenesis. We identified the molecular basis for the regulation of ILK and its alternative role in conferring ERK1/2/NF-κB-mediated growth advantages to gastric cancer cells.

Results

Inhibiting ILK with short hairpin RNA or T315, a putative ILK inhibitor, abolished NF-κB-mediated the growth in the human gastric cancer cells AGS, SNU-1, MKN45, and GES-1. ILK stimulated Ras activity to activate the c-Raf/MEK1/2/ERK1/2/ribosomal S6 kinase/inhibitor of κBα/NF-κB signaling by facilitating the formation of the IQ motif-containing GTPase-activating protein 1 (IQGAP1)–Ras complex. Forced enzymatic ILK expression promoted cell growth by facilitating ERK1/2/NF-κB signaling. PI3K activation or decreased PTEN expression prolonged ERK1/2 activation by protecting ILK from proteasome-mediated degradation. C-terminus of heat shock cognate 70 interacting protein, an HSP90-associated E3 ubiquitin ligase, mediated ILK ubiquitination to control PI3K- and HSP90-regulated ILK stabilization and signaling. In addition to cell growth, the identified pathway promoted cell migration and reduced the sensitivity of gastric cancer cells to the anticancer agents 5-fluorouracil and cisplatin. Additionally, exogenous administration of EGF as well as overexpression of EGFR triggered ILK- and IQGAP1-regulated ERK1/2/NF-κB activation, cell growth, and migration.

Conclusion

An increase in ILK non-canonically promotes ERK1/2/NF-κB activation and leads to the growth of gastric cancer cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12964-014-0069-3) contains supplementary material, which is available to authorized users.

Silencing KRAS overexpression in arsenic-transformed prostate epithelial and stem cells partially mitigates malignant phenotype

Inorganic arsenic is a human carcinogen that likely targets the prostate. Chronic arsenic exposure malignantly transforms the RWPE-1 human prostate epithelial line to chronic arsenic exposed-prostate epithelial (CAsE-PE) cells, and a derivative normal prostate stem cell (SC) line, WPE-stem to arsenic-cancer SCs (As-CSCs). The KRAS oncogene is highly overexpressed in CAsE-PE cells and activation precedes transformation, inferring mechanistic significance. As-CSCs also highly overexpress KRAS. Thus, we hypothesize KRAS activation is key in causing and maintaining an arsenic-induced malignant phenotype, and hence, KRAS knockdown (KD) may reverse this malignant phenotype. RNA interference using shRNAmirs to obtain KRAS KD was used in CAsE-PE and As-CSC cells. Cells analyzed 2 weeks post transduction showed KRAS protein decreased to 5% of control after KD, confirming stable KD. KRAS KD decreased phosphorylated ERK, indicating inhibition of RAS/ERK signaling, a proliferation/survival pathway activated with arsenic transformation. Secreted metalloproteinase (MMP) activity was increased by arsenic-induced malignant transformation, but KRAS KD from 4 weeks on decreased secreted MMP-9 activity by 50% in As-CSCs. Colony formation, a characteristic of cancer cells, was decreased in both KRAS KD transformants. KRAS KD also decreased the invasive capacity of both cell types. KRAS KD decreased proliferation in As-CSCs, consistent with loss of rapid tumor growth. Genes predicted to impact cell proliferation (eg, Cyclin D1, p16, and p21) changed accordingly in both KD cell types. Thus, KRAS silencing impacts aspects of arsenic-induced malignant phenotype, inducing loss of many typical cancer characteristics particularly in As-CSCs.

Polyisoprenylated methylated protein methyl esterase as a putative drug target for androgen-insensitive prostate cancer

Prostate cancer (CaP) is the most frequently diagnosed cancer in US men, with an estimated 236,590 new cases and 29,720 deaths in 2013. There exists the need to identify biomarkers/therapeutic targets for the early/companion diagnosis and development of novel therapies against the recalcitrant disease. Mutation and overexpression-induced abnormal activities of polyisoprenylated proteins have been implicated in CaP. Polyisoprenylated methylated protein methyl esterase (PMPMEase) catalyses the only reversible and terminal reaction of the polyisoprenylation pathway and may promote the effects of G proteins on cell viability. In this review, the potential role of PMPMEase to serve as a new drug target for androgen-insensitive CaP was determined. Specific PMPMEase activities were found to be 3.5- and 4.5-fold higher in androgen-sensitive 22Rv1 and androgen-dependent LNCaP and 1.5- and 9.8-fold higher in castration-resistant DU 145 and PC-3 CaP cells compared to normal WPE1-NA22 prostate cells. The PMPMEase inhibitor, L-28, induced apoptosis with EC50 values ranging from 1.8 to 4.6 μM. The PMPMEase activity in the cells following treatment with L-28 followed a similar profile, with IC50 ranging from 2.3 to 130 μM. L-28 disrupted F-actin filament organisation at 5 μM and inhibited cell migration 4-fold at 2 μM. Analysis of a CaP tissue microarray for PMPMEase expression revealed intermediate, strong, and very strong staining in 94.5% of the 92 adenocarcinoma cases compared to trace and weak staining in the normal and normal-adjacent tissue controls. The data are an indication that effective targeting of PMPMEase through the development of more potent agents may lead to the successful treatment of metastatic CaP.

Gene signatures ESC, MYC and ERG-fusion are early markers of a potentially dangerous subtype of prostate cancer

Background

Good prognostic tools for predicting disease progression in early stage prostate cancer (PCa) are still missing. Detection of molecular subtypes, for instance by using microarray gene technology, can give new prognostic information which can assist personalized treatment planning. The detection of new subtypes with validation across additional and larger patient cohorts is important for bringing a potential prognostic tool into the clinic.

Methods

We used fresh frozen prostatectomy tissue of high molecular quality to further explore four molecular subtype signatures of PCa based on Gene Set Enrichment Analysis (GSEA) of 15 selected gene sets published in a previous study. For this analysis we used a statistical test of dependent correlations to compare reference signatures to signatures in new normal and PCa samples, and also explore signatures within and between sample subgroups in the new samples.

Results

An important finding was the consistent signatures observed for samples from the same patient independent of Gleason score. This proves that the signatures are robust and can surpass a normally high tumor heterogeneity within each patient. Our data did not distinguish between four different subtypes of PCa as previously published, but rather highlighted two groups of samples which could be related to good and poor prognosis based on survival data from the previous study.The poor prognosis group highlighted a set of samples characterized by enrichment of ESC, ERG-fusion and MYC + rich signatures in patients diagnosed with low Gleason score,. The other group consisted of PCa samples showing good prognosis as well as normal samples. Accounting for sample composition (the amount of benign structures such as stroma and epithelial cells in addition to the cancer component) was important to improve subtype assignments and should also be considered in future studies.

Conclusion

Our study validates a previous molecular subtyping of PCa in a new patient cohort, and identifies a subgroup of PCa samples highly interesting for detecting high risk PCa at an early stage. The importance of taking sample tissue composition into account when assigning subtype is emphasized.

A novel method for somatic transgenesis of the mouse prostate using the Sleeping Beauty transposon system

BACKGROUND

In vivo ectopic gene expression is a common approach for prostate research through the use of transgenes in germline transgenic mice. For some other organs, somatic transgenesis with the Sleeping Beauty transposon system has allowed in vivo ectopic gene expression with higher throughput and lower cost than germline transgenic approaches.

METHODS

Mouse e16 urogenital sinuses (UGSs) were co-injected with plasmids expressing the Sleeping Beauty transposase and plasmids with control or activated BRAF expressing transposons. Following electroporation, the transduced UGSs were grown as allografts in mouse hosts for 8 weeks, and the resulting allografts were evaluated for several endpoints.

RESULTS

Transposon-transduced UGS allografts developed into prostatic tissue with normal tissue structure and cellular differentiation. Integration of transposon vectors into the genomes of transduced allografts was confirmed using linker-mediated PCR, sequencing, and in situ PCR. Transduction of UGS allografts with transposons expressing activated BRAF resulted in ectopic BRAF expression that was detectable at both the mRNA and protein levels. Prostatic ducts over-expressing activated BRAF also had ectopic activation of the ERK1/2 mitogen activated kinases and increased epithelial cell proliferation.

CONCLUSIONS

The Sleeping Beauty transposon system can be used to achieve somatic transgenesis of prostatic allografts. This new method for achieving ectopic gene expression in the prostate will complement other existing approaches such as ectopic gene expression in cell lines and in germline transgenic mice. Advantages of this new approach include preservation of stromal-epithelial interactions not possible with cell lines, and higher throughput and lower cost than traditional germline transgenic approaches.

ETV4 promotes metastasis in response to activation of PI3-kinase and Ras signaling in a mouse model of advanced prostate cancer

Combinatorial activation of PI3-kinase and RAS signaling occurs frequently in advanced prostate cancer and is associated with adverse patient outcome. We now report that the oncogenic Ets variant 4 (Etv4) promotes prostate cancer metastasis in response to coactivation of PI3-kinase and Ras signaling pathways in a genetically engineered mouse model of highly penetrant, metastatic prostate cancer. Using an inducible Cre driver to simultaneously inactivate Pten while activating oncogenic Kras and a fluorescent reporter allele in the prostate epithelium, we performed lineage tracing in vivo to define the temporal and spatial occurrence of prostate tumors, disseminated tumor cells, and metastases. These analyses revealed that though disseminated tumors cells arise early following the initial occurrence of prostate tumors, there is a significant temporal lag in metastasis, which is temporally coincident with the up-regulation of Etv4 expression in primary tumors. Functional studies showed that knockdown of Etv4 in a metastatic cell line derived from the mouse model abrogates the metastatic phenotype but does not affect tumor growth. Notably, expression and activation of ETV4, but not other oncogenic ETS genes, is correlated with activation of both PI3-kinase and Ras signaling in human prostate tumors and metastases. Our findings indicate that ETV4 promotes metastasis in prostate tumors that have activation of PI3-kinase and Ras signaling, and therefore, ETV4 represents a potential target of therapeutic intervention for metastatic prostate cancer.

Autophagy mediates survival of pancreatic tumour-initiating cells in a hypoxic microenvironment

Involvement of dysregulated autophagy in cancer growth and progression has been shown in different tumour entities, including pancreatic ductal adenocarcinoma (PDA). PDA is an extremely aggressive tumour characterized by a small population of highly therapy-resistant cancer stem cells (CSCs) capable of self-renewal and migration. We examined whether autophagy might be involved in the survival of CSCs despite nutrition and oxygen deprivation typical for the hypoxic tumour microenvironment of PDA. Immunohistochemistry revealed that markers for hypoxia, CSCs and autophagy are co-expressed in patient-derived tissue of PDA. Hypoxia starvation (H/S) enhanced clonogenic survival and migration of established pancreatic cancer cells with stem-like properties (CSC(high)), while pancreatic tumour cells with fewer stem cell markers (CSC(low)) did not survive these conditions. Electron microscopy revealed more advanced autophagic vesicles in CSC(high) cells, which exhibited higher expression of autophagy-related genes under normoxic conditions and relative to CSC(low) cells, as found by RT-PCR and western blot analysis. LC3 was already fully converted to the active LC3-II form in both cell lines, as evaluated by western blot and detection of accumulated GFP-LC3 protein by fluorescence microscopy. H/S increased formation of autophagic and acid vesicles, as well as expression of autophagy-related genes, to a higher extent in CSC(high) cells. Modulation of autophagy by inhibitors and activators resensitized CSC(high) to apoptosis and diminished clonogenicity, spheroid formation, expression of CSC-related genes, migratory activity and tumourigenicity in mice. Our data suggest that enhanced autophagy levels may enable survival of CSC(high) cells under H/S. Interference with autophagy-activating or -inhibiting drugs disturbs the fine-tuned physiological balance of enhanced autophagy in CSC and switches survival signalling to suicide.

Prognostic determinants in prostate cancer

Clinical outcomes in prostate cancer are heterogeneous, and given the high prevalence of the disease, there is a pressing need to identify clinically useful markers of prognosis. Many clinical, pathological, molecular, and genetic factors have been investigated in this capacity, although relatively few are routinely used. With a growing understanding of the molecular pathogenesis of prostate cancer, there is the potential that the next generation of makers will prove sufficiently robust to guide the optimal management of men with prostate cancer. Here, we review the various clinical and molecular prognostic determinants in prostate cancer.

Targeting of pancreatic and prostate cancer stem cell characteristics by Crambe crambe marine sponge extract

Cancer stem cells (CSCs) are suggested as reason for resistance of tumors toward conventional tumor therapy including pancreatic and advanced prostate cancer. New therapeutic agents are urgently needed for targeting of CSCs. Marine sponges harbor novel and undefined compounds with antineoplastic activity but their potential to eliminate CSC characteristics is not examined so far. We collected 10 marine sponges and one freshwater sponge by diving at the seaside and prepared crude methanolic extracts. The effect to established pancreatic and prostate CSC lines was evaluated by analysis of apoptosis, cell cycle, side population, colony and spheroid formation, migratory potential in vitro and tumorigenicity in vivo. While each sponge extract at a 1:10 dilution efficiently diminished viability, Crambe crambe marine sponge extract (CR) still strongly reduced viability of tumor cells at a dilution of 1:1,000 but was less toxic to normal fibroblasts and endothelial cells. CR inhibited self-renewal capacity, apoptosis resistance, and proliferation even in gemcitabine-selected pancreatic cancer cells with acquired therapy resistance and enhanced CSC characteristics. CR pretreatment of tumor cells diminished tumorigenicity of gemcitabine-resistant tumor cells in mice and totally abolished tumor take upon combination with gemcitabine. Our data suggest that CR contains substances, which render standard cancer therapy more effective by targeting of CSC characteristics. Isolation of bioactive metabolites from CR and evaluation in mice are required for development of new CSC-specific chemotherapeutic drugs from a marine sponge.

Characterization of KRAS rearrangements in metastatic prostate cancer

Using an integrative genomics approach called amplification breakpoint ranking and assembly analysis, we nominated KRAS as a gene fusion with the ubiquitin-conjugating enzyme UBE2L3 in the DU145 cell line, originally derived from prostate cancer metastasis to the brain. Interestingly, analysis of tissues revealed that 2 of 62 metastatic prostate cancers harbored aberrations at the KRAS locus. In DU145 cells, UBE2L3-KRAS produces a fusion protein, a specific knockdown of which attenuates cell invasion and xenograft growth. Ectopic expression of the UBE2L3-KRAS fusion protein exhibits transforming activity in NIH 3T3 fibroblasts and RWPE prostate epithelial cells in vitro and in vivo. In NIH 3T3 cells, UBE2L3-KRAS attenuates MEK/ERK signaling, commonly engaged by oncogenic mutant KRAS, and instead signals via AKT and p38 mitogen-activated protein kinase (MAPK) pathways. This is the first report of a gene fusion involving the Ras family, suggesting that this aberration may drive metastatic progression in a rare subset of prostate cancers.

SIGNIFICANCE

This is the first description of an oncogenic gene fusion of KRAS, one of the most studied proto-oncogenes. KRAS rearrangement may represent the driving mutation in a rare subset of metastatic prostate cancers, emphasizing the importance of RAS-RAF-MAPK signaling in this disease.

SmgGDS is up-regulated in prostate carcinoma and promotes tumour phenotypes in prostate cancer cells

SmgGDS is a guanine nucleotide exchange factor with the unique ability to activate multiple small GTPases, implicating it in cancer development and progression. Here, we investigated the role of SmgGDS in prostate cancer by studying the expression of SmgGDS in benign and malignant prostatic tissues. We also probed SmgGDS function in three prostate carcinoma cell lines using small interfering RNA (siRNA). Immunohistochemical analysis revealed that SmgGDS levels were elevated in prostatic intraepithelial neoplasia (PIN), prostate carcinoma, and metastatic prostate carcinoma. In addition, expression of SmgGDS positively correlated with that of cyclooxygenase-2 (COX-2), a protein believed to promote the development of prostate carcinoma. Reduction of SmgGDS expression in prostate carcinoma cells inhibited proliferation and migration, irrespective of androgen receptor status. These effects were accompanied by a reduction in COX-2 expression and in activity of NF-kappaB, a known regulator of COX-2. Taken together, these findings suggest that SmgGDS promotes the development and progression of prostate cancer, possibly associated with NF-kappaB-dependent up-regulation of COX-2.

Targeting prostate cancer based on signal transduction and cell cycle pathways

Prostate cancer remains a leading cause of death in men despite increased capacity to diagnose at earlier stages. After prostate cancer has become hormone independent, which often occurs after hormonal ablation therapies, it is difficult to effectively treat. Prostate cancer may arise from mutations and dysregulation of various genes involved in regulation signal transduction (e.g., PTEN, Akt, etc.,) and the cell cycle (e.g., p53, p21(Cip1), p27(Kip1), Rb, etc.,). This review focuses on the aberrant interactions of signal transduction and cell cycle genes products and how they can contribute to prostate cancer and alter therapeutic effectiveness.

Analysis of pathway activity in primary tumors and NCI60 cell lines using gene expression profiling data

To determine cancer pathway activities in nine types of primary tumors and NCI60 cell lines, we applied an in silica approach by examining gene signatures reflective of consequent pathway activation using gene expression data. Supervised learning approaches predicted that the Ras pathway is active in approximately 70% of lung adenocarcinomas but inactive in most squamous cell carcinomas, pulmonary carcinoids, and small cell lung carcinomas. In contrast, the TGF-beta, TNF-alpha, Src, Myc, E2F3, and beta-catenin pathways are inactive in lung adenocarcinomas. We predicted an active Ras, Myc, Src, and/or E2F3 pathway in significant percentages of breast cancer, colorectal carcinoma, and gliomas. Our results also suggest that Ras may be the most prevailing oncogenic pathway. Additionally, many NCI60 cell lines exhibited a gene signature indicative of an active Ras, Myc, and/or Src, but not E2F3, beta-catenin, TNF-alpha, or TGF-beta pathway. To our knowledge, this is the first comprehensive survey of cancer pathway activities in nine major tumor types and the most widely used NCI60 cell lines. The "gene expression pathway signatures" we have defined could facilitate the understanding of molecular mechanisms in cancer development and provide guidance to the selection of appropriate cell lines for cancer research and pharmaceutical compound screening.

Combinatorial activities of Akt and B-Raf/Erk signaling in a mouse model of androgen-independent prostate cancer

Androgen independence is responsible for most prostate cancer lethality, yet currently there are no effective clinical treatments. We have been investigating the mechanisms underlying androgen-independent prostate cancer in Nkx3.1;Pten mutant mice, which display salient features of the disease, including a requirement for wild-type androgen receptor (AR) signaling. We now demonstrate that the Akt and Erk MAP kinase signaling pathways are activated in androgen-independent lesions of these mice. Forced activation of either Akt or Erk signaling in an androgen-responsive prostate cancer cell line promotes hormone-independent but AR-dependent growth in culture. Although these pathways act additively in culture, they act synergistically in vivo to promote tumorigenicity and androgen independence in the context of the prostate microenvironment. We propose that androgen independence emerges by means of epithelial-stromal competition, in which activation of Akt and Erk promotes AR activity in the prostate epithelium while counteracting antagonistic effects of the stroma.

Molecular pathology of prostate cancer

The incidence of prostate cancer has increased in Japan recently and is developing into a life-threatening disease for many Japanese men. This is a result of several convergent factors including the adoption of a Western lifestyle, the widespread use of prostate-specific antigen (PSA) testing, and an increased population of advanced years in Japanese men. Although there is much information to date relating to molecular events underlying the etiology of prostate cancer, it is still unclear as to how and when these genetic alterations occur in each step of tumorigenesis. One fruitful area of investigation has been in the analysis of chromosomal abnormalities commonly observed in prostate cancer. However, no single candidate gene has been definitely identified in cancer initiation and/or progression; in addition, less research has been devoted to understanding the molecular events that underlie tumor histogenesis in terms of likely precursor lesions, such as prostatic intraepithelial neoplasia (PIN). This article reviews the current knowledge of the molecular pathology of prostate cancer, including its histogenesis, genetic and epigenetic alterations, and hereditary factors.

Molecular markers of prostate cancer outcome

Molecular markers have the potential to serve not only as prognostic factors but may be targets for new therapeutic strategies and predictors of response in a range of cancers. Prostate cancer development and progression is predicated on a series of genetic and epigenetic events within the prostate cell and its milieu. Within this review, we identify candidate molecules involved in diverse processes such as cell proliferation, death and apoptosis, signal transduction, androgen receptor (AR) signalling, cellular adhesion and angiogenesis that are linked to outcome in prostate cancer. Current markers with potential prognostic value include p53, Bcl-2, p16INK4A, p27Kip1, c-Myc, AR, E-cadherin and vascular endothelial growth factor. Evolving technology permits the identification of an increasing number of molecular markers with prognosis and predictive potential. We also review the use of gene microarray analysis in gene discovery as a means of identifying and cosegregating novel markers of prostate cancer outcome. By integrating selected markers into prospective clinical trials, there is potential for us to provide specific targeted therapy tailored for an increasing number of patients.

Androgen-induced differentiation and tumorigenicity of human prostate epithelial cells

Androgen ablation is the primary treatment modality for patients with metastatic prostate cancer; however, the role of androgen receptor signaling in prostate cancer development remains enigmatic. Using a series of genetically defined immortalized and tumorigenic human prostate epithelial cells, we found that introduction of the androgen receptor induced differentiation of transformed prostate epithelial cells to a luminal phenotype reminiscent of organ-confined prostate cancer when placed in the prostate microenvironment. Moreover, androgen receptor expression converted previously androgen-independent, tumorigenic prostate epithelial cells into cells dependent on testosterone for tumor formation. These observations indicate that androgen receptor expression is oncogenic and addictive for the human prostate epithelium.

Phase II trial of perillyl alcohol (NSC 641066) administered daily in patients with metastatic androgen independent prostate cancer

OBJECTIVE

We conducted a phase II multicenter trial of perillyl alcohol in patients with advanced hormone refractory prostate cancer (HRPC). The primary endpoint was to evaluate the 6-month progression-free survival given the potential cytostatic nature of the drug. Secondary objectives included assessing acute and chronic toxicities, as well as measuring objective response rates.

METHODS

Patients with metastatic androgen-independent prostate cancer that failed at least one prior chemotherapeutic or experimental regimen were eligible. Perillyl alcohol was administered orally at 1200 mg/m2/dose four times daily and continued until disease progression or development of unacceptable toxicity.

RESULTS

Fifteen patients were eligible. Six patients received less than one cycle (4 weeks) of drug, four of which stopped because of drug intolerance. Only six patients received more than two cycles of therapy and were considered evaluable for response. Main toxicity included grade 1-2 gastrointestinal intolerance (nausea/vomiting in 60% of the patients) and fatigue (47%). One patient developed a grade 4 hypokalemia that was felt likely attributable to the drug. No objective responses were seen. All patients either progressed or withdrew from the study secondary to drug intolerance before the 6-month time period.

CONCLUSION

Perillyl alcohol administered at this dose and formulation did not have any objective clinical activity in this patient population.

Signaling inhibitors in the treatment of prostate cancer

Inhibiting androgen receptor (AR) activation through medical or surgical castration and blockade of AR-androgen binding is the cornerstone of treatment for advanced prostate cancer. However, in most cases tumor growth eventually becomes androgen independent. Alternative mechanisms of AR activation, some of which involve growth factor receptor signaling, have been demonstrated in prostate cancer models, and it is likely that a number of autocrine and paracrine growth factor ligand-receptor interactions such as those of epidermal growth factors, fibroblast growth factors, and insulin-like growth factors contribute to the androgen independent phenotype by promoting cell proliferation and survival. Blocking activation and signaling through growth factor receptors and upstream signaling proteins has emerged as a credible approach to cancer treatment. Successful application of this approach in prostate cancer using a growing array of small molecule kinase inhibitors, antibodies, and antisense oligonucleotides will be greatly accelerated by elucidation of the key signaling pathways that maintain the androgen independent phenotype.

Nonandrogenic mediators of prostatic growth

Prostate growth and development are primarily under the control of androgens; however, other factors can also influence prostatic growth through alternative pathways. This article discusses some of the major nonandrogenic mediators of prostate growth. Information on the pathways by which these factors exert their effects is also reviewed.

Vascular endothelial growth factor and its correlation with angiogenesis and p53 expression in prostate cancer

BACKGROUND

Previously it was demonstrated that in prostate tumors, angiogenesis measured as microvessel density (MVD) is associated with tumor stage as well as WHO grade and is an independent predictor of clinical outcome. Vascular endothelial growth factor (VEGF) is a major inducer of angiogenesis. There is some evidence that P53 mutations cause overexpression of VEGF. We studied VEGF expression, p53 overexpression, and P53 mutations in prostate cancer (PCA) to investigate the role of VEGF as an angiogenic marker and the possible deregulation of VEGF as a result of P53 mutations in PCA.

METHODS

Immunohistochemical staining with a polyclonal VEGF antibody was performed in 55 paraffin-embedded PCA, in which MVD had previously been determined, as well as in 5 prostatic adenomas (PA) and 20 adjacent normal prostate tissues. In addition, 37 PCA and 5 PAs were examined for p53 expression by immunohistochemistry. Temperature gradient gel electrophoresis (TGGE) was performed in 13 of these PCA to screen for P53 mutations. VEGF expression, p53 expression, and mutations were then correlated with tumor stage, grade, MVD, and clinical outcome.

RESULTS

While PA and normal prostate tissue generally showed no or only low VEGF expression, there was a significant increase in VEGF expression with tumor stage, grade, and MVD in PCA. During clinical follow-up (mean, 31.9 months), 9 of 55 patients had tumor progression. Significant differences in VEGF expression were found between patients with tumor progression and those without (P = 0.0004). Of the 37 PCA evaluated for p53 expression, 12 exhibited p53 overexpression. TGGE revealed P53 mutations in 3 of 13 PCA. However, there was no correlation between VEGF expression, p53 overexpression, and P53 mutation, respectively.

CONCLUSIONS

VEGF seems to be an important, clinically relevant inducer of angiogenesis in PCA. VEGF expression was shown to correlate positively with tumor stage, grade, MVD, and clinical outcome. However, regulation of VEGF in PCA appears to be independent of p53 expression.

Comparative studies of prostate cancer in Japan versus the United States. A review

This article reviews the available data on prostate cancer in Japan compared with that in the United States, with emphasis on epidemiologic, pathologic, and molecular aspects. Previous studies have demonstrated ethnic/racial differences in the incidence of prostate cancer between the two countries. Recent investigations indicate that different genetic alterations or polymorphisms are related to carcinogenesis in the prostate. Comparative geographic-pathologic autopsy studies suggest that different promoting factors including genetic, epigenetic, and environmental influences may be responsible for ethnic variations in the postinduction progression of prostate cancer.

Prostate tumours from an Asian population: examination of bax, bcl-2, p53 and ras and identification of bax as a prognostic marker

Molecular studies have suggested that ethnicity may play a significant role in prostate tumorigenesis, but no information exists for groups other than Caucasian or Japanese patients. We examined 62 archival samples of prostate tumours from Asians of non-Japanese origin for the over-expression of p53, for the possible presence of mutated ras genes, for the overexpression of the bcl-2 and bax proteins, as well as directly for the presence of apoptotic cells by the TUNEL methodology. Gene lesions of both ras (0%) and p53 (3%) were rare. While bcl-2 expression was not observed in any sample, bax expression was noted in 76% of samples and was associated with a significantly worse patient prognosis both overall (P< 0.005) and specifically in Chinese patients (P< 0.02). Apoptotic cells were found in 61% of samples, and were significantly associated with the presence of bax expression (P = 0.002), but not patient survival. These results suggest that prostate tumours from non-Japanese Asians are genetically distinct from prostate tumour found in both Japanese and Caucasian patients, and that treatment modalities may need to be tailored for specific population groups.

Loss of heterozygosity (LOH), malignancy grade and clonality in microdissected prostate cancer

The aim of the present study was to find out whether increasing malignancy of prostate carcinoma correlates with an overall increase of loss of heterozygosity (LOH), and whether LOH typing of microdissected tumour areas can help to distinguish between multifocal or clonal tumour development. In 47 carcinomas analysed at 25 chromosomal loci, the overall LOH rate was found to be significantly lower in grade 1 areas (2.2%) compared with grade 2 (9.4%) and grade 3 areas (8.3%, P = 0.007). A similar tendency was found for the mean fractional allele loss (FAL, 0.043 for grade 1, 0.2 for grade 2 and 0.23 for grade 3, P = 0.0004). Of 20 tumours (65%) with LOH in several microdissected areas, 13 had identical losses at 1-4 loci within two or three areas, suggesting clonal development of these areas. Markers near RB, DCC, BBC1, TP53 and at D13S325 (13q21-22) showed higher loss rates in grades 2 and 3 (between 25% and 44.4%) compared with grade 1 (0-6.6%). Tumour-suppressor genes (TSGs) near these loci might, thus, be important for tumour progression. TP53 mutations were detected in 27%, but BBC1 mutations in only 7%, of samples with LOH. Evaluation of all 25 loci in every tumour made evident that each prostate cancer has its own pattern of allelic losses.

Immunohistochemical analysis of rasGTPase activating protein (rasGAP) in prostate cancer

The ras protooncogene plays a key role in the signal transduction cascade of activated growth factors, and is known to be activated or overexpressed in multiple tumor types, including prostate cancer. rasGTPase activating protein (rasGAP), a major downregulator of ras activity, has been shown to be underexpressed in human trophoblastic tumors, and presumably acts as a tumor suppressor gene product in these neoplasms. To assess the role that rasGAP plays in the development of prostate cancer, we performed immunohistochemical analyses with anti rasGAP antibodies of 125 human prostate tumors from Israel. Staining results were correlated with Gleason grade. In the majority of tumors (99/125-79%) there was either no staining or the tumor and surrounding benign glands had a similar pattern of staining. In up to 16% of the tumors, cytoplasmic, tumor-specific loss of expression was noted, presumably indicative of the role of rasGAP as a tumor suppressor gene. Unexpectedly, in up to 21% of the tumors, nuclear staining was demonstrated, and in about 20% of these, there was an accompanying loss of expression in the non neoplastic cytoplasm. Neither cytoplasmic nor nuclear staining correlated with Gleason grade. These findings of nuclear staining by anti-rasGAP are intriguing, since it is the first time that nuclear translocation of rasGAP is demonstrated, which might indicate that in this subset of tumors, rasGAP acts as a direct acting oncogene. The data indicate that rasGAP may play a dual regulatory role in prostate proliferation and that nuclear expression of it may be associated with malignant transformation of these cells.

Immunohistochemical and mutational analysis of the p53 tumour suppressor gene and the bcl-2 oncogene in primary testicular germ cell tumours

The role of p53 in testicular germ cell tumours is still contradictory based on the finding of immunohistochemical overexpression at the protein level, but lack of mutations at the DNA level. In addition, p53 wild-type activity has been demonstrated in cell culture experiments. Overexpression of the proto-oncogene bcl-2 might block p53-induced apoptosis and might inhibit p53 functional activity. To clarify the apparent paradox with respect to p53 overexpression and lack of mutations, an immunohistochemical and mutational analysis of p53 and bcl-2 in TGCT was performed. Ten normal testes, 52 CIS and 151 clinical stage I nonseminomatous GCTs were included in our study. A commercially available anti-p53 polyclonal rabbit antibody and an anti-bcl-2-mouse monoclonal antibody were used to stain the 5pm sections. Staining was assessed by counting at least 500 cells from the area of the most intense staining in each tumour cell type, and this was scored semiquantitatively for intensity of staining on a 4 point scale. In addition, 30 primary GCTs were included in the mutational analysis: areas with p53 overexpression were identified and microdissected prior to DNA extraction. p53 exons 5-8 were amplified by polymerase chain reaction (PCR) followed by single strand conformation polymorphism analysis. Templates demonstrating band shifts on SSCP were subjected to direct DNA sequence analysis. None of the normal testes, 32/52 (62%) CIS, and 142/151 (94%) germ cell tumours exhibited p53 overexpression. p53 expression was significantly lower in mature teratomas (0.8 +/- 0.2) than in other germ cell tumour components (2.8 +/- 1.2, p > 0.001). PCR-SSCP did not reveal any missense mutations or deletions for the p53 gene. Bcl-2 protein expression was observed in none of the normal testes, in none of the CIS, and in 14/151 (9.3%) germ cell tumours. 13/14 germ cell tumours demonstrated bcl-2 expression only in the glandular and stromal elements of their teratomatous components whereas all other components were negative for bcl-2. Our results--p53 overexpression, lack of p53 mutations, undetectable bcl-2--are consistent with recent in vitro studies. High susceptibility of testicular cancer to drug-induced apoptosis appears to be the result of wild-type p53 and lack of bcl-2. Radiation and chemotherapeutic insensitivity of mature teratomas might be the result of bcl-2 overexpression and lack of p53 overexpression. Therefore, chemoresistance to DNA damaging agents might be reflected by the expression of p53 and bcl-2 and it might be useful to evaluate p53 and bcl-2 in primary tumours and metastatic lesions in order to identify patients early with primary or secondary chemoresistance.

Comparison of ras activation in prostate carcinoma in Japanese and American men

BACKGROUND

Comparative studies of point mutations in K-, N-, and H-ras oncogenes were performed on prostate carcinoma from Japanese and American patients to clarify the racial difference.

METHODS

We probed for mutations in 70 Japanese and 31 American specimens using polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) analysis and immunohistochemistry for ras p21.

RESULTS

Within the 70 Japanese specimens, eight mutations in codon 12 of K-ras (five GGT-->GTT transversions and three CGT-->GAT transitions) and one mutation in codon 12 of the N-ras gene (a GGT-->GTT transversion) were confirmed, whereas the American samples yielded only one definable mutation, a GGT-->GAT transition, in codon 12 of K-ras.

CONCLUSIONS

The frequency of ras gene mutations in clinical carcinoma in Japanese men was higher than that in American men. It is suggested that there may be fundamental differences in the etiology of prostate carcinoma in Japan and the United States, perhaps based on genetics and/or environmental factors.

Protein expression of p53, bcl-2, and KI-67 (MIB-1) as prognostic biomarkers in patients with surgically treated, clinically localized prostate cancer

BACKGROUND

Protein expression in the primary tumor of the tumor suppressor gene p53 and the proto-oncogene bcl-2 have been shown to be prognostic biomarkers of cancer recurrence after radical prostatectomy in patients with clinically localized prostate cancer. Cancer cell proliferation as measured by immunohistochemical markers such as the MIB-1 antibody for Ki-67 has recently been suggested to be of prognostic value in prostate cancer. The goal of this study was to determine the clinical use of p53, Ki-67 (MIB-1), and bcl-2 immunohistochemical protein expression in the primary tumor as combined predictors of disease progression after radical prostatectomy (RP).

METHODS

Protein expressions of p53, Ki-67, and bcl-2 were evaluated in archival paraffin-embedded RP specimens from 162 patients monitored from 1 to 10 years (mean, 4.5 years) and correlated to stage, grade, race, and serologic (prostate-specific antigen) recurrence after operation.

RESULTS

Expression was detected in 112 (69.1%), 44 (27.2%), and 62 (38.3%) of 162 patients for p53 (1+ or greater), bcl-2 (1+ or greater), and Ki-67 (2+ or greater), respectively. Biomarker expressions were not correlated to age and race; however, all increased with increasing stage and grade. The degree of expression by percentage of malignant cells staining correlated to recurrence for p53 and Ki-67 but not for bcl-2. All three markers were correlated to raw and Kaplan-Meier recurrence by means of univariate analysis with recurrence estimates at 6 years of 60.7% versus 24.2%, 84.2% versus 38.6%, and 72.4% versus 30.6% comparing positive versus negative expression of p53, bcl-2, and Ki-67, respectively. p53 and bcl-2 remained as independent prognostic markers by Cox multivariate regression analysis. Although Ki-67 did not remain an independent marker, it added prognostic use in certain subsets of patients.

CONCLUSIONS

p53, bcl-2, and Ki-67 (MIB-1) appear to be important biomarkers to predict recurrence in patients with clinically localized prostate cancer after RP, and all three biomarkers deserve further study.

Intravenous vs. intraprostatic administration of N-methyl-N-nitrosourea to induce prostate cancer in rats

To develop an improved model of human prostate cancer, 16-wk-old Wistar rats were treated orally for 18 days with the antiandrogen, flutamide (50 mg/kg body weight [BW]/day), followed by 3 days of s.c. testosterone (100 mg/kg BW). There were the only treatments the control animals received (Group 1, n = 10). On the day after the third testosterone injection, N-methyl-N-nitorsourea (MNU) was administered via the tail vein at a dose of 50 mg/kg BW (Groups 2, n = 40 and 3, n = 20); in some rats, a second dose was delivered by the same route 22 wk later (Group 3). A smaller dose of MNU (15 mg/kg BW) was administered intraprostatically (Group 4, n = 20) to a fourth group. In Groups 2, 3, and 4, silastic capsules containing testosterone were implanted s.c. approximately every 6 wk beginning 1 wk post-MNU. Accessory sex gland tumors arose in MNU-treated rats in Group 2 (12/40, 30%). Group 3 (8/20, 40%), and Group 4 (8/20, 40%); 90% were macroscopic (25/28). There were no neoplasms in these organs in the control rats (Group 1, 0/10). These accessory sex gland neoplasms were adenocarcinomas or undifferentiated carcinomas which appeared to be derived from the prostate based on location and histological characteristics, although the size and spread of some of the tumors precluded definitive localization of the tissue of origin. The incidence of these neoplasms was similar in rats given a single dose of MNU intraprostatically or two doses of MNU i.v., but the animals treated intraprostatically maintained higher body weights and developed fewer extraneous tumors. The average (+/- SD) latent period for clinical or postmortem detection of prostate neoplasia after MNU was shortest in the rats given two i.v. doses (39 +/- 3 wk) compared with the single i.v. dose (45 +/- 6 wk) or an intraprostatic dose (56 +/- 7 wk). In 57% of the cases (16/28), the prostate tumors metastasized to distant sites. An activating point mutation was detected in codon 12 of the Ki-ras oncogene in the MNU-induced primary prostate tumors (8/10 examined), and metastases arising from these prostate tumors (2/3) but was absent in normal prostate tissue (0/6). This study demonstrates that two systemic doses of MNU increase the incidence and decrease the latency of prostate neoplasms compared with a single dose, and that a single dose of MNU injected intraprostatically induces prostate adenocarcinoma without many of the other tumors and weight loss typically found after i.v. administration.

Alteration of the tumor suppressor gene p53 in a high fraction of hormone refractory prostate cancer

PURPOSE

We studied the role of p53 tumor suppressor gene alteration in prostate cancer progression by demonstrating a difference in abnormal p53 findings between early and hormone refractory disease.

MATERIALS AND METHODS

The study included p53 immunohistochemistry of 26 archival transurethral resection specimens from patients with radiation recurrent and hormone refractory disease, 27 untreated primary tumors and 8 untreated metastatic lesions. p53 mutation analysis of tumor deoxyribonucleic acid (DNA) from microdissected specimens was done by cold single strand conformational polymorphism and DNA sequencing.

RESULTS

Elevated p53 protein was present in 16 of 17 hormone refractory specimens (94%), 4 of 8 untreated metastatic tumors (50%) and 6 of 27 primary untreated tumors (22%). DNA analysis of representative specimens with elevated p53 confirmed p53 gene alterations in 9 of 11 cases (82%).

CONCLUSIONS

Our study revealed a clear progression of increased p53 alteration from untreated primary to hormone refractory disease (p < 0.00005).

Increased p53 protein does not correlate to p53 gene mutations in microdissected human testicular germ cell tumors

PURPOSE

To determine if primary testicular germ cell tumors that overexpress p53 tumor suppressor gene protein have p53 gene mutations.

MATERIALS AND METHODS

We examined 30 primary testicular tissues from 26 patients representing two groups. Group one consisted of eleven cases (6 nonseminomatous germ cell tumors and 5 seminomas) in which tissue samples for DNA analysis were microdissected from paraffin block regions with elevated immunohistochemical staining for p53 protein. Group two consisted of 19 testis tumor tissues which had been fresh frozen and were chosen to correspond to archival tissue specimens exhibiting elevated levels of p53 protein. The DNA was extracted from these tissues and subjected to exon specific amplification by polymerase chain reaction (PCR) and cold single-strand conformation polymorphism (Cold SSCP) analysis.

RESULTS

In these cases with elevated p53 protein, no p53 gene exon 5-8 mutations were detected except 1 seminoma with a codon 140 silent mutation (no protein alteration).

CONCLUSIONS

Testicular tumors appear to exhibit elevated levels of wild-type p53 protein, the significance of which is yet to be elucidated.