Androgen deprivation is the standard systemic treatment for advanced prostate cancer (PCa), but most patients ultimately develop castration-resistance. We show here that MYB is transcriptionally activated by androgen deprivation or impairment of androgen receptor (AR) signaling. MYB gene silencing significantly inhibited PCa growth in vitro and in vivo. Microarray data revealed that c-Myb shares a substantial subset of DNA damage response (DDR) target genes with AR, suggesting that c-Myb may replace AR for the dominant role in the regulation of their common DDR target genes in AR inhibition-resistant or AR-negative PCa. Gene signatures comprising AR, MYB, and their common DDR target genes are significantly correlated with metastasis, castration-resistance, recurrence, and shorter overall survival in PCa patients. We demonstrated in vitro that silencing of MYB, BRCA1 or TOPBP1 synergized with poly (ADP-ribose) polymerase (PARP) inhibitor olaparib (OLA) to increase cytotoxicity to PCa cells. We further demonstrated that targeting the c-Myb-TopBP1-ATR-Chk1 pathway by using the Chk1 inhibitor AZD7762 synergizes with OLA to increase PCa cytotoxicity. Our results reveal new mechanism-based therapeutic approaches for PCa by targeting PARP and the c-Myb-TopBP1-ATR-Chk1 pathway.
To study the role of FAK signaling complexes in promoting metastatic properties of prostate cancer (PCa) cells, we selected stable, highly migratory variants, termed PC3 Mig-3 and DU145 Mig-3, from two well-characterized PCa cell lines, PC3 and DU145. These variants were not only increased migration and invasion in vitro, but were also more metastatic to lymph nodes following intraprostatic injection into nude mice. Both PC3 Mig-3 and DU145 Mig-3 were specifically increased in phosphorylation of FAK Y861. We therefore examined potential alterations in Src family kinases responsible for FAK phosphorylation and determined only Yes expression was increased. Overexpression of Yes in PC3 parental cells and src−/−fyn−/−yes−/− fibroblasts selectively increased FAK Y861 phosphorylation, and increased migration. Knockdown of Yes in PC3 Mig-3 cells decreased migration and decreased lymph node metastasis following orthotopic implantation of into nude mice. In human specimens, Yes expression was increased in lymph node metastases relative to paired primary tumors from the same patient, and increased pFAK Y861 expression in lymph node metastases correlated with poor prognosis. These results demonstrate a unique role for Yes in phosphorylation of FAK and in promoting PCa metastasis. Therefore, phosphorylated FAK Y861 and increased Yes expression may be predictive markers for PCa metastasis.
FAK; Yes; migration; metastasis; prostate cancer
The magnetic resonance spectroscopic imaging (MRSI) is the only technique that is currently available in the clinical practice to provide the metabolic status of prostate tissue at the cellular level with a great potential to improve the clinical patient care. Increasing the field strength from 1.5 to 3 T can theoretically provide proportionately higher signal-to-noise ratio (SNR) and improve spectral separation between prostatic metabolite peaks. The technique, however, has been limited to a few academic institutions that are equipped with a team of experts primarily due to due to serious technical challenges in optimizing the spectral quality. High quality shimming is key to the successful MRSI acquisition. Without optimization of the increased field inhomogeneity and radiofrequency (RF) dielectric effect at 3 T, the spectral peak broadening and residual signal from the periprostatic fat tissue may render the overall spectra non-diagnostic. The purpose of this technical note is to present the practical steps of successful acquisition of 3 T MRSI and to address several important technical challenges in minimizing the effect of the increased magnetic field and RF field inhomogeneity in order to obtain highest possible spectral quality based on our initial experience in using 3 T MRSI prototype software.
Prostate cancer; magnetic resonance spectroscopy; 3 T; magnetic field inhomogeneity; radiofrequency (RF) field inhomogeneity
On July 31, 2013, the Prostate Cancer Foundation assembled a working committee on the molecular biology and pathologic classification of neuroendocrine differentiation in prostate cancer. The committee consisted of genitourinary oncologists, urologists, urological surgical pathologists, basic scientists, and translational researchers, with expertise in this field. It was concluded that the proceedings of the meeting should be reported in 2 manuscripts appealing to different target audiences, one to focus on surgical pathology and the other to review the molecular aspects of this disease. New clinical and molecular data emerging from prostate cancers treated by contemporary androgen deprivation therapies, as well as primary lesions, have highlighted the need for refinement of diagnostic terminology to encompass the full spectrum of neuroendocrine differentiation. It is envisioned that specific criteria associated with the refined diagnostic terminology will lead to clinically relevant pathologic diagnoses that will stimulate further clinical and molecular investigation and identification of appropriate targeted therapies.
small cell carcinoma; Paneth cell like; large cell neuroendocrine carcinoma; carcinoid; prostate adenocarcinonma
Clinical features characteristic of small-cell prostate carcinoma (SCPC), (““anaplastic””) often emerge during the progression of prostate cancer. We sought to determine the efficacy of platinum-based chemotherapy in patients meeting at least one of seven prospectively defined “anaplastic” clinical criteria, including exclusive visceral or predominantly lytic bone metastases, bulky tumor masses, low PSA levels relative to tumor burden or short response to androgen deprivation therapy.
A 120-patient phase II trial of frontline carboplatin and docetaxel (CD) and second-line etoposide and cisplatin (EP) was designed to provide reliable clinical response estimates under a Bayesian probability model with early stopping rules in place for futility and toxicity.
Seventy-four of 113 (65.4%) and 24 of 71 (33.8%) were progression free after 4 cycles of CD and EP, respectively. Median overall survival (OS) was 16 months (95% CI, 13.6-19.0 months). Of the 7 “anaplastic” criteria, bulky tumor mass was significantly associated with poor outcome. Lactic acid dehydrogenase (LDH) strongly predicted for OS and rapid progression. Serum carcinoembryonic antigen (CEA) concentration strongly predicted OS but not rapid progression. Neuroendocrine markers did not predict outcome or response to therapy.
Our findings support the hypothesis that patients with “anaplastic” prostate cancer are a recognizable subset characterized by a high response rate of short duration to platinum-containing chemotherapies, similar to SCPC. Our results suggest that CEA is useful for selecting therapy in men with CRPC and consolidative therapies to bulky high-grade tumor masses should be considered in this patient population.
Small-cell; neuroendocrine; castration-resistant; prostate carcinoma; platinum chemotherapy
In this study we report that expression of glioma pathogenesis-related protein 1 (GLIPR1) regulated numerous apoptotic, cell cycle, and spindle/centrosome assembly-related genes, including AURKA and TPX2, and induced apoptosis and/or mitotic catastrophe (MC) in prostate cancer (PCa) cells, including p53-mutated/deleted, androgen-insensitive metastatic PCa cells. Mechanistically, GLIPR1 interacts with heat shock cognate protein 70 (Hsc70); this interaction is associated with SP1 and c-Myb destabilization and suppression of SP1-and c-Myb-mediated AURKA and TPX2 transcription. Inhibition of AURKA and TPX2 using siRNA mimicked enforced GLIPR1 expression in the induction of apoptosis and MC. Recombinant GLIPR1-ΔTM protein inhibited AURKA and TPX2 expression, induced apoptosis and MC, and suppressed orthotopic xenograft tumor growth. Our results define a novel GLIPR1-regulated signaling pathway that controls apoptosis and/or mitotic catastrophe in PCa cells and establishes the potential of this pathway for targeted therapies.
Glioma pathogenesis-related; protein 1 (GLIPR1); Hsc70; c-Myb; AURKA; TPX2; Prostate cancer
Small-cell prostate carcinoma (SCPC) morphology predicts for a distinct clinical behavior, resistance to androgen ablation, and frequent but short responses to chemotherapy. We sought to develop model systems that reflect human SCPC and can improve our understanding of its biology.
We developed a set of CRPC xenografts and examined their fidelity to their human tumors of origin. We compared the expression and genomic profiles of SCPC and large cell neuroendocrine carcinoma (LCNEC) xenografts to those of typical prostate adenocarcinoma xenografts. Results were validated immunohistochemically in a panel of 60 human tumors.
The reported SCPC and LCNEC xenografts retain high fidelity to their human tumors of origin and are characterized by a marked upregulation of UBE2C and other mitotic genes in the absence of AR, retinoblastoma (RB1) and cyclin D1 (CCND1) expression. We confirmed these findings in a panel of CRPC patients' samples. In addition, array comparative genomic hybridization of the xenografts showed that the SCPC/LCNEC tumors display more copy number variations than the adenocarcinoma counterparts. Amplification of the UBE2C locus and microdeletions of RB1 were present in a subset, but none displayed AR nor CCND1 deletions. The AR, RB1, and CCND1 promoters showed no CpG methylation in the SCPC xenografts.
Modeling human prostate carcinoma with xenografts allows in-depth and detailed studies of its underlying biology. The detailed clinical annotation of the donor tumors enables associations of anticipated relevance to be made. Futures studies in the xenografts will address the functional significance of the findings.
castration resistance prostate cancer; small cell neuroendocrine carcinoma; retinoblastoma; UBE2C; cyclin D1
Previously we reported caveolin-1 (Cav-1) overexpression in prostate cancer (PCa) cells and demonstrated that it promotes PCa progression. Here, we report that Cav-1 was overexpressed in 41.7% (15 of 36) of high-grade prostatic intraepithelial neoplasia (HGPIN) specimens obtained during radical prostatectomies. Positive correlations exist between Cav-1–positive (Cav-1+) HGPIN and Cav-1+ primary PCa (rho = 0.655, P< 0.0001) and between Cav-1 and c-Myc expression in HGPIN (rho = 0.41, P = 0.032). To determine whether Cav-1 cooperates with c-Myc in development of premalignant lesions and PCa in vivo, we generated transgenic mice with c-Myc overexpression driven by the ARR2PB promoter. In this ARR2PB–c-myc model, Cav-1 overexpression was found in mouse PIN (mPIN) lesions and PCa cells and was associated with a significantly higher ratio of proliferative to apoptotic labeling in mPIN lesions than in the Cav-1–negative epithelia adjacent to those lesions (10.02 vs 4.34; P = 0.007). Cav-1 overexpression was also associated with increased levels of P-Akt and VEGF-A, which were previously associated with Cav-1–induced PCa cell survival and positive-feedback regulation of cellular Cav-1 levels, respectively. In multiple PCa cell lines, Cav-1 protein (but not mRNA) was induced by c-Myc transfection, whereas VEGF siRNA transfection abrogated c-Myc–induced Cav-1 overexpression, suggesting a c-Myc–VEGF–Cav-1 signaling axis. Overall, our results suggest that Cav-1 is associated with c-Myc in the development of HGPIN and PCa. Further, Cav-1 overexpression in HGPIN is potentially a biomarker for early identification of patients who tend to develop Cav-1+ primary PCa.
Caveolin-1; c-Myc; prostatic intraepithelial neoplasia; prostate cancer; metaplasia
Prostate cancer; prostate surgery; comparative effectiveness; Gleason Score; interstitial implant; seeds; prostate biopsy; LDR brachytherapy
Small-cell carcinoma (SCC) of the prostate is an AR-negative variant of prostate cancer found at progression in 10–20% of castrate-resistant disease. Its finding predicts a distinct clinical course and a poor prognosis. Large-cell neuroendocrine carcinoma (LCNEC) is a much rarer variant that behaves similarly to SCC. The biological mechanisms that drive these disease variants are poorly understood.
Eight tumor fragments from the salvage pelvic exenteration specimen of a patient with castrate-resistant prostate carcinoma were subcutaneously implanted into 6- to 8-week-old male CB17 SCID mice. Serial tissue sections and tissue microarrays of the resulting MDA PCa 144 xenograft lines were used for histopathologic and immunohistochemical characterization of the xenografts and their tissue of origin. RNA from two representative xenograft sublines was used for gene-expression profiling.
All eight fragments formed tumors: four of the MDA PCa 144 xenograft sublines had morphologic characteristics of SCC and four, of LCNEC. All retained high fidelity to their parent tumor tissue, which remained stable through serial passages. Morphological transitions in the specimen of origin suggested LCNEC represents an intermediate step between adenocarcinoma and SCC. Over 2,500 genes were differentially expressed between the SCC (MDA PCa 144-13) and the LCNEC (MDA PCa 144-4) sublines and enriched in “Nervous System Development” Gene Ontology subtree.
The eight xenograft models described represent the spectrum of neuroendocrine carcinomas in prostate cancer and will be valuable preclinical tools to study the pathogenesis of and therapy targets for this increasingly recognized subset of lethal prostate cancer.
castrate-resistant; cancer; androgen-independent; neural development; array
Recent studies have revealed the presence of TMPRSS2-ERG gene fusion in both primary and metastatic prostatic cancers (PCAs). However, the relationship between primary and corresponding metastatic PCAs with respect to the status of this gene fusion remains unclear. Using fluorescence in situ hybridization, we evaluated the rearrangement of the ERG gene in the radical prostatectomy (RP) specimens and corresponding lymph node metastases from 19 patients with PCA. The mean age of the patients was 61 years and the median Gleason score in the RP specimens was 7 (4+3). PCA was unifocal in 6 cases and multifocal in 13 cases, including 10 with 2 foci and 3 with 3 foci. In the primary PCAs, rearrangement of the ERG gene was observed in 13 cases and associated with deletion of the 5’ ERG gene in 8 cases. In the metastases, the ERG rearrangement was present in 10 cases and associated with deletion of the 5’ ERG gene in 6 cases. In unifocal PCAs, the status of the ERG rearrangement was concordant between the primary PCA and metastasis in 5 of 6 cases. In multifocal PCA, despite a significant interfocal discordance, the status of the ERG rearrangement was concordant between the index (largest) primary tumor focus and metastasis in all 13 cases. Our study demonstrates a close relationship of the TMPRSS2-ERG gene fusion status between primary and metastatic PCA. The concordance of the ERG gene rearrangement status between the index primary tumor focus and metastasis suggests that metastasis most likely arises from the index tumor focus in multifocal PCA.
TMPRSS2-ERG gene fusion; prostate cancer; metastasis; multifocality
The interplay between androgen and Hedgehog (Hh) signaling pathways may be associated with prostate cancer progression and resistance to therapy.
Tissue microarrays from prostatectomy specimens were derived from 53 patients treated preoperatively with androgen ablation (AA) with or without chemotherapy, and from 26 stage- and grade-matched controls. A previously characterized androgen-regulated human prostate cancer xenograft was used to conduct parallel murine studies. Expression of markers of interest was determined on both untreated and castrated tumors.
Four-month exposure to AA or AA with chemotherapy led to a uniform increase in Hh signaling as compared to controls, paired with an inverse trend of androgen receptor (AR) and CYP17 expression in clinically derived specimens. Changes in the expression profiles of Hh signaling were observed in the epithelium and stroma, in response to genotoxic stress of androgen ablation and chemotherapy. A reduced expression of KI67and increased bcl2 expression was observed in the malignant epithelial compartment.
To our knowledge, this is the first clinical evidence that Hh signaling is induced by AA or the combination of AA and chemotherapy and, by inference, contributes to castrate-resistant progression of prostate cancer as supported by parallel human and murine studies. These data are in agreement with previous reports that implicate Hh signaling in castrate-resistant progression of prostate cancer. Based on these findings, we are pursuing parallel clinical and murine investigations to determine if Hh signaling inhibition combined with AA will be more effective than AA alone.
Prostate cancer; preoperative treatment; Hedgehog signaling; resistance to treatment; androgen ablation
Downregulation of the proapoptotic p53 target gene GLIPR1 occurs frequently in prostate cancer (PCa), but the functional meaning of this event is obscure. Here we report the discovery of functional relationship between GLIPR1 and c-Myc in PCa where c-Myc is often upregulated. We found that the expression of GLIPR1 and c-Myc were inversely correlated in human PCa. Restoration of GLIPR1 expression in PCa cells downregulated c-myc levels, inhibiting cell cycle progression. Downregulation was linked to a reduction in β-catenin/TCF4-mediated transcription of the c-myc gene, which were caused by GLIPR1-mediated redistribution of casein kinase 1α (CK1α) from the Golgi apparatus to the cytoplasm where CK1α could phosphorylate β-catenin and mediate its destruction. In parallel, GLIPR1 also promoted c-Myc protein ubiquitination and degradation by glycogen synthase kinase-3α- and/or CK1α-mediated c-Myc phosphorylation. Notably, genetic ablation of the mouse homolog of Glipr1 cooperated with c-myc overexpression to induce prostatic intraepithelial neoplasia (PIN) and PCa. Together, our findings provide evidence for CK1α-mediated destruction of c-Myc and identify c-Myc S252 as a crucial CK1α phosphorylation site for c-Myc degradation. Further, they reveal parallel mechanisms of c-myc downregulation by GLIPR1 that when ablated in the prostate are sufficient to drive c-Myc expression and malignant development.
GLIPR1; c-Myc; CK1α; oncoprotein destruction; prostate cancer
Persistent androgen signaling is implicated in castrate-resistant prostate cancer (CRPC) progression. This study aimed to evaluate androgen signaling in bone marrow–infiltrating cancer and testosterone in blood and bone marrow and to correlate with clinical observations.
Patients and Methods
This was an open-label, observational study of 57 patients with bone-metastatic CRPC who underwent transiliac bone marrow biopsy between October 2007 and March 2010. Patients received oral abiraterone acetate (1 g) once daily and prednisone (5 mg) twice daily. Androgen receptor (AR) and CYP17 expression were assessed by immunohistochemistry, testosterone concentration by mass spectrometry, AR copy number by polymerase chain reaction, and TMPRSS2-ERG status by fluorescent in situ hybridization in available tissues.
Median overall survival was 555 days (95% CI, 440 to 965+ days). Maximal prostate-specific antigen decline ≥ 50% occurred in 28 (50%) of 56 patients. Homogeneous, intense nuclear expression of AR, combined with ≥ 10% CYP17 tumor expression, was correlated with longer time to treatment discontinuation (> 4 months) in 25 patients with tumor-infiltrated bone marrow samples. Pretreatment CYP17 tumor expression ≥ 10% was correlated with increased bone marrow aspirate testosterone. Blood and bone marrow aspirate testosterone concentrations declined to less than picograms-per-milliliter levels and remained suppressed at progression.
The observed pretreatment androgen-signaling signature is consistent with persistent androgen signaling in CRPC bone metastases. This is the first evidence that abiraterone acetate achieves sustained suppression of testosterone in both blood and bone marrow aspirate to less than picograms-per-milliliter levels. Potential admixture of blood with bone marrow aspirate limits our ability to determine the origin of measured testosterone.
To study Wnt/beta-catenin in castrate-resistant prostate cancer (CRPC) and understand its function independently of the beta-catenin–androgen receptor (AR) interaction.
We performed beta-catenin immunocytochemical analysis, evaluated TOP-flash reporter activity (a reporter of beta-catenin–mediated transcription), and sequenced the beta-catenin gene in MDA PCa 118a, MDA PCa 118b, MDA PCa 2b, and PC-3 prostate cancer (PCa) cells. We knocked down beta-catenin in AR-negative MDA PCa 118b cells and performed comparative gene-array analysis. We also immunohistochemically analyzed beta-catenin and AR in 27 bone metastases of human CRPCs.
Beta-catenin nuclear accumulation and TOP-flash reporter activity were high in MDA PCa 118b but not in MDA PCa 2b or PC-3 cells. MDA PCa 118a and 118b cells carry a mutated beta-catenin at codon 32 (D32G). Ten genes were expressed differently (false discovery rate, 0.05) in MDA PCa 118b cells with downregulated beta-catenin. One such gene, hyaluronan synthase 2 (HAS2), synthesizes hyaluronan, a core component of the extracellular matrix. We confirmed HAS2 upregulation in PC-3 cells transfected with D32G-mutant beta-catenin. Finally, we found nuclear localization of beta-catenin in 10 of 27 human tissue specimens; this localization was inversely associated with AR expression (P = 0.056, Fisher’s exact test), suggesting that reduced AR expression enables Wnt/beta-catenin signaling.
We identified a previously unknown downstream target of beta-catenin, HAS2, in PCa, and found that high beta-catenin nuclear localization and low or no AR expression may define a subpopulation of men with bone-metastatic PCa. These findings may guide physicians in managing these patients.
beta-catenin; prostate cancer; androgen receptor; hyaluronan synthase
Individual cancers harbor a set of genetic aberrations that can be informative for identifying rational therapies currently available or in clinical trials. We implemented a pilot study to explore the practical challenges of applying high-throughput sequencing in clinical oncology. We enrolled patients with advanced or refractory cancer who were eligible for clinical trials. For each patient, we performed whole-genome sequencing of the tumor, targeted whole-exome sequencing of tumor and normal DNA, and transcriptome sequencing (RNA-Seq) of the tumor to identify potentially informative mutations in a clinically relevant time frame of 3 to 4 weeks. With this approach, we detected several classes of cancer mutations including structural rearrangements, copy number alterations, point mutations, and gene expression alterations. A multidisciplinary Sequencing Tumor Board (STB) deliberated on the clinical interpretation of the sequencing results obtained. We tested our sequencing strategy on human prostate cancer xenografts. Next, we enrolled two patients into the clinical protocol and were able to review the results at our STB within 24 days of biopsy. The first patient had metastatic colorectal cancer in which we identified somatic point mutations in NRAS, TP53, AURKA, FAS, and MYH11, plus amplification and overexpression of cyclin-dependent kinase 8 (CDK8). The second patient had malignant melanoma, in which we identified a somatic point mutation in HRAS and a structural rearrangement affecting CDKN2C. The STB identified the CDK8 amplification and Ras mutation as providing a rationale for clinical trials with CDK inhibitors or MEK (mitogenactivated or extracellular signal–regulated protein kinase kinase) and PI3K (phosphatidylinositol 3-kinase) inhibitors, respectively. Integrative high-throughput sequencing of patients with advanced cancer generates a comprehensive, individual mutational landscape to facilitate biomarker-driven clinical trials in oncology.
The arachidonic acid pathway is important in the development and progression of numerous malignant diseases, including prostate cancer. To more fully evaluate the role of individual cyclooxygenases (COXs), lipoxygenases (LOXs) and their metabolites in prostate cancer, we measured mRNA and protein levels of COXs and LOXs and their arachidonate metabolites in androgen-dependent (LNCaP) and androgen-independent (PC-3 and DU145) prostate cancer cell lines, bone metastasis-derived MDA PCa 2a and MDA PCa 2b cell lines and their corresponding xenograft models, as well as core biopsy specimens of primary prostate cancer and nonneoplastic prostate tissue taken ex vivo after prostatectomy. Relatively high levels of COX-2 mRNA and its product PGE2 were observed only in PC-3 cells and their xenografts. By contrast, levels of the exogenous 12-LOX product 12-HETE were consistently higher in MDA PCa 2b and PC-3 cells and their corresponding xenograft tissues than were those in LNCaP cells. More strikingly, the mean endogenous level of 12-HETE was significantly higher in the primary prostate cancers than in the nonneoplastic prostate tissue (0.094 vs. 0.010 ng/mg protein, respectively; p=0.019). Our results suggest that LOX metabolites such as 12-HETE are critical in prostate cancer progression and that the LOX pathway may be a target for treating and preventing prostate cancer.
arachidonic acid; cyclooxygenase; lipoxygenase; prostate cancer; xenograft; eicosanoid
Clinicians are increasingly willing to treat prostate cancer within the primary site in the presence of regional lymph node or even limited distant metastases. However, no formal study on the merits of this approach has been reported. We used a preoperative clinical discovery platform to prioritize pathways for assessment as therapeutic targets and to test the hypothesis that the primary site harbors potentially lethal tumors after aggressive treatment.
Patients and Methods
Patients with locally advanced or lymph node–metastatic prostate cancer underwent 1 year of androgen ablation and three cycles of docetaxel therapy, followed by prostatectomy. All specimens were characterized for stage by accepted criteria. Expression of select molecular markers implicated in disease progression and therapy resistance was determined immunohistochemically and compared with that in 30 archived specimens from untreated patients with high-grade prostate cancer. Marker expression was divided into three groups: intracellular signaling pathways, stromal-epithelial interaction pathways, and angiogenesis.
Forty patients were enrolled, 30 (75%) of whom underwent prostatectomy and two (5%) who underwent cystoprostatectomy. Twenty-nine specimens contained sufficient residual tumor for inclusion in a tissue microarray. Immunohistochemical analysis showed increased epithelial and stromal expression of CYP17, SRD5A1, and Hedgehog pathway components, and modulations of the insulin-like growth factor I pathway.
A network of molecular pathways reportedly linked to prostate cancer progression is activated after 1 year of therapy; biomarker expression suggests that potentially lethal cancers persist in the primary tumor and may contribute to progression.
The recently described transcriptomic switch to a mitosis program in castration-resistant prostate cancer (CRPC) suggests that mitotic proteins may be rationally targeted at this lethal stage of the disease. In this study, we showed upregulation of the mitosis-phase at the protein level in our cohort of 51 clinical CRPC cases and found centrosomal aberrations to also occur preferentially in CRPC compared with untreated, high Gleason–grade hormone-sensitive prostate cancer (P<0.0001). Expression profiling of chemotherapy-resistant CRPC samples (n = 25) was performed, and the results were compared with data from primary chemotherapy-naïve CRPC (n = 10) and hormone-sensitive prostate cancer cases (n = 108). Our results showed enrichment of mitosis-phase genes and pathways, with progression to both castration-resistant and chemotherapy-resistant disease. The mitotic centromere-associated kinesin (MCAK) was identified as a novel mitosis-phase target in prostate cancer that was overexpressed in multiple CRPC gene-expression datasets. We found concordant gene expression of MCAK between our parent and murine CRPC xenograft pairs and increased MCAK protein expression with clinical progression of prostate cancer to a castration-resistant disease stage. Knockdown of MCAK arrested the growth of prostate cancer cells suggesting its utility as a potential therapeutic target.
Preoperative treatment of prostate cancer (PCa) changes morphology of residual tumors so that the Gleason score is no longer valid.
To codify morphologic features of preoperatively treated PCa and identify potential classifiers predictive of outcome.
Design, setting, and participants
We performed a detailed morphologic evaluation of specimens obtained from 115 patients with high-risk PCa who had preoperative androgen ablation, alone or in combination with chemotherapy.
Included hierarchical clustering analysis of morphologic characteristics, associations with other pathologic parameters, and univariate and multivariate analyses in search for associations with disease outcome.
Results and limitations
Based on hierarchical clustering analysis, we categorized pretreated prostate cancer in three morphologically distinct groups: group A, characterized by a predominance of cell clusters, cell cords, and isolated cells; group B tumors, by intact and fused small glands; and group C tumors by any degree of cribriform growth pattern or intraductal tumor spread.
Univariate analysis identified associations between this grouping, pathologic tumor stage (p < 0.01) and residual tumor volume (p < 0.001). Presence of intraductal spread or cribriform pattern in biopsies was associated with group C tumors. The presence of cribriform or intraductal spread morphology and positive surgical margins were stronger predictors of biochemical relapse than pathologic stage on multivariate analysis. The number of specimens evaluated in this study was limited, and a prospective validation is warranted along with molecular studies to validate the proposed morphologic classifier.
If validated, this classification will introduce uniformity in the selection of tissue samples for biomarker studies, facilitate the comparison of trials among different institutions, and may provide a new prognostic tool for preoperatively treated PCa.
The genetic control of prostate cancer development is poorly understood. Large numbers of gene-expression datasets on different aspects of prostate tumorigenesis are available. We used these data to identify and prioritize candidate genes associated with the development of prostate cancer and bone metastases. Our working hypothesis was that combining meta-analyses on different but overlapping steps of prostate tumorigenesis will improve identification of genes associated with prostate cancer development.
A Z score-based meta-analysis of gene-expression data was used to identify candidate genes associated with prostate cancer development. To put together different datasets, we conducted a meta-analysis on 3 levels that follow the natural history of prostate cancer development. For experimental verification of candidates, we used in silico validation as well as in-house gene-expression data.
Genes with experimental evidence of an association with prostate cancer development were overrepresented among our top candidates. The meta-analysis also identified a considerable number of novel candidate genes with no published evidence of a role in prostate cancer development. Functional annotation identified cytoskeleton, cell adhesion, extracellular matrix, and cell motility as the top functions associated with prostate cancer development. We identified 10 genes--CDC2, CCNA2, IGF1, EGR1, SRF, CTGF, CCL2, CAV1, SMAD4, and AURKA--that form hubs of the interaction network and therefore are likely to be primary drivers of prostate cancer development.
By using this large 3-level meta-analysis of the gene-expression data to identify candidate genes associated with prostate cancer development, we have generated a list of candidate genes that may be a useful resource for researchers studying the molecular mechanisms underlying prostate cancer development.
CTLA-4 blockade is being explored in numerous clinical trials as an immune based therapy for different malignancies. Our group conducted the first pre-operative clinical trial with the anti-CTLA-4 antibody ipilimumab in 12 patients with localized urothelial carcinoma of the bladder.
Six patients were treated with 3mg/kg/dose of anti-CTLA-4 and six patients were treated with 10mg/kg/dose of antibody. Primary endpoints of the study were safety and immune monitoring.
Most drug-related adverse events consisted of grade 1/2 toxicities. All patients had measurable immunologic pharmacodynamic effects, consisting of an increased frequency of CD4+ICOShi T cells in tumor tissues and the systemic circulation. To determine if CD4+ICOShi T cells could be a correlative marker for clinical outcome after treatment with anti-CTLA-4, a cohort of metastatic melanoma patients was studied retrospectively for frequency of CD4+ICOShi T cells and survival. Data from this small cohort of patients indicated that an increased frequency of CD4+ICOShi T cells, sustained over a period of 12 weeks of therapy, correlates with increased likelihood of clinical benefit consisting of overall survival.
Our trial demonstrates that anti-CTLA-4 therapy has a tolerable safety profile in the pre-surgical setting and that a pre-operative model can be used to obtain biological data on human immune responses, which can efficiently guide the monitoring of patients treated in the metastatic disease setting.
Secondary analyses of two randomized, controlled phase III trials demonstrated that selenium and vitamin E could reduce prostate cancer incidence. To characterize pharmacodynamic and gene expression effects associated with use of selenium and vitamin E, we undertook a randomized, placebo-controlled phase IIA study of prostate cancer patients before prostatectomy and created a preoperative model for prostatectomy tissue interrogation.
Thirty-nine men with prostate cancer were randomly assigned to treatment with 200 μg of selenium, 400 IU of vitamin E, both, or placebo. Laser capture microdissection of prostatectomy biopsy specimens was used to isolate normal, stromal, and tumor cells. Gene expression in each cell type was studied with microarray analysis and validated with a real-time polymerase chain reaction (PCR) and immunohistochemistry. An analysis of variance model was fit to identify genes differentially expressed between treatments and cell types. A beta-uniform mixture model was used to analyze differential expression of genes and to assess the false discovery rate. All statistical tests were two-sided.
The highest numbers of differentially expressed genes by treatment were 1329 (63%) of 2109 genes in normal epithelial cells after selenium treatment, 1354 (66%) of 2051 genes in stromal cells after vitamin E treatment, and 329 (56%) of 587 genes in tumor cells after combination treatment (false discovery rate = 2%). Validation of 21 representative genes across all treatments and all cell types yielded Spearman correlation coefficients between the microarray analysis and the PCR validation ranging from 0.64 (95% confidence interval [CI] = 0.31 to 0.79) for the vitamin E group to 0.87 (95% CI = 0.53 to 0.99) for the selenium group. The increase in the mean percentage of p53-positive tumor cells in the selenium-treated group (26.3%), compared with that in the placebo-treated group (5%), showed borderline statistical significance (difference = 21.3%; 95% CI = 0.7 to 41.8; P = .051).
We have demonstrated the feasibility and efficiency of the preoperative model and its power as a hypothesis-generating engine. We have also identified cell type– and zone-specific tissue effects of interventions with selenium and vitamin E that may have clinical implications.
We assessed the expression of Matrix Metalloproteinase (MMP) to E-cadherin (M/E ratio) to determine the correlation of gene expression with pathologic variables and outcome in a cohort of African American (AA) prostate cancer patients.
Tumors from formalin-fixed, paraffin embedded RP specimens were examined. Gleason scores were 6, 7, and ≥8 in 7, 16, 13 tumors respectively. Pathologic stage was organ confined (pT2) in 18 and advanced (> pT2) in 18 tumors. A colorimetric mRNA insitu hybridization ( ISH ) assay was performed using biotinylated anti-sense oligonucleotide probes for MMP 2 and 9, as well as for E-cadherin gene transcripts. Immunohistochemistry (IHC) was performed utilizing specific monoclonal antibodies to detect the above genes. Image analysis was performed to determine the intensity of both mRNA and protein expression. Two reviewers analyzed ISH gene expression independently.
The M/E expression ratio was significantly increased at the invasive edge (but not the center) of tumors of higher Gleason score (p=0.02 and 0.0008) and pathologic stage (p=0.0001 and <0.0001) when examined by both ISH and IHC. Significant variability in ISH staining interpretation was noted within and among the two study reviewers. An M/E ratio > 2.5 was associated with biochemical recurrence after radical prostatectomy in addition to tumor pathologic stage subsequent to univariate statistical analysis.
The M/E ratio characterizes an important aspect of the molecular phenotype associated with the histologic progression of prostate cancer among African American prostate cancer patients. A larger comparative study is required to determine potential racial variation and prognostic significance of gene expression.
prostate cancer; matrix metalloproteinase; E-cadherin; African American; radical prostatectomy
In prostate cancer, androgen blockade strategies are commonly used to treat osteoblastic bone metastases. However, responses to these therapies are typically brief, and the mechanism underlying androgen-independent progression is not clear. Here, we established what we believe to be the first human androgen receptor–negative prostate cancer xenografts whose cells induced an osteoblastic reaction in bone and in the subcutis of immunodeficient mice. Accordingly, these cells grew in castrated as well as intact male mice. We identified FGF9 as being overexpressed in the xenografts relative to other bone-derived prostate cancer cells and discovered that FGF9 induced osteoblast proliferation and new bone formation in a bone organ assay. Mice treated with FGF9-neutralizing antibody developed smaller bone tumors and reduced bone formation. Finally, we found positive FGF9 immunostaining in prostate cancer cells in 24 of 56 primary tumors derived from human organ-confined prostate cancer and in 25 of 25 bone metastasis cases studied. Collectively, these results suggest that FGF9 contributes to prostate cancer–induced new bone formation and may participate in the osteoblastic progression of prostate cancer in bone. Androgen receptor–null cells may contribute to the castration-resistant osteoblastic progression of prostate cancer cells in bone and provide a preclinical model for studying therapies that target these cells.