Prospective Characterization of Circulating Tumor Cells in Hormone Sensitive Oligometastatic Prostate Cancer Patients on a Metastasis-Directed Therapy Trial

PURPOSE/OBJECTIVE(S)

Prospective data have shown that metastasis-directed therapy (MDT) can alter the natural history of oligometastatic disease. In hormone-sensitive prostate cancer (HSPC), the clinical effect of MDT has been validated by STOMP, ORIOLE and SABR-COMET phase II trials. Circulating tumor cells (CTCs) are likely the source for the formation of macroscopic metastases. CTCs may provide an approach for identifying subgroups of patients with oligometastatic HSPC (oligoHSPC) that would benefit most from MDT. Our main goal was to evaluate the feasibility of CTC detection and subtypes in oligoHSPC patients that may benefit from MDT.

MATERIALS/METHODS

ORIOLE randomized men with recurrent HSPC with 1-3 metastases to observation (Obs) vs. stereotactic ablative radiotherapy (SABR) MDT. Blood samples were prospectively collected at baseline (D0) and 6-mos (D180) and shipped for analysis on Epic Sciences liquid biopsy platform (Epic Sciences, San Diego, CA). Machine learning algorithms identified CTCs and characterized androgen receptor (AR) and PSMA expression. Association with clinical factors and outcomes were examined. Biochemical failure-free survival (BFFS) event was a PSA rise of at least 2 ng/mL and 25% above nadir. Progression-free survival (PFS) was a composite endpoint including BFFS event, radiologic progression (RECIST v1.1); symptomatic progression; initiation of ADT; or death. Comparisons of patient and tumor characteristics performed by two-sample t-tests. Survival curves were generated by the Kaplan-Meier method and evaluated by the log-rank test. Effect of SABR on post-SABR on CTC levels were calculated by McNemar test.

RESULTS

A total of 82 samples were collected in ORIOLE: 70 SABR (35 D0 and 35 D180) and 12 Obs (7 D0 and 5 D180). 30/42 men had CTCs detected on D0 (71%; AR+ = 7, PSMA+ = 13) and in 26/40 on D180 (65%; AR+ = 9, PSMA+ = 8). Median follow-up was 41.7-mos. There was no association between CTC presence or subtypes (AR+ or PSMA+) with Gleason score or PSA. PFS was significantly lower in the patients with AR+ vs. AR- CTCs on D0 in the SABR arm (p = 0.011, median PFS: AR+ = 9.3- vs. AR+ = 27.1-mos). The median BFFS trended towards a difference for AR+ = 12.9- vs. AR- = 29.2-mos (D180, p = 0.058). SABR had no effect on the presence or subtypes of CTC at D180.

CONCLUSION

Baseline and dynamic CTC levels and their subtypes in oligoHSPC from the ORIOLE randomized trial of MDT was examined. AR+ CTCs at baseline and 6-mos were correlated with clinical outcomes following SABR. Longer follow-up, further analysis and a greater number of patients are needed for a more comprehensive conclusion.

Identification of a Predictive Genomic Biomarker for Prostate Directed Therapy in Synchronous Low-Volume Metastatic Castration Sensitive Prostate Cancer

PURPOSE/OBJECTIVE(S)

Standard of care management for metastatic castration sensitive prostate cancer (mCSPC) includes androgen deprivation therapy (ADT) with docetaxel or second-generation anti-androgen therapy. Recently, randomized data has demonstrated radiotherapy to the prostate is associated with an improvement in overall survival among patients with low-volume metastatic disease. Tumor genomics represents an additional dimension to understand the clinical trajectory of patients with mCSPC. Herein we aim to evaluate a high-risk genomic signature for its ability to predict response to prostate directed therapy (PDT).

MATERIALS/METHODS

We performed a single institution retrospective review of men with low-volume mCSPC who underwent next-generation sequencing of their tumor. Patients were classified according to the presence of high-risk (HiRi) mutation including pathogenic mutations in either TP53, ATM, BRCA1/2, or Rb1. Our primary endpoint was to determine the effect of PDT on overall survival (OS) in patients with and without a HiRi mutation. Survival analysis was performed with the Kaplan-Meier method compared with log-rank test and multivariable cox regression. Interaction between HiRi mutation and PDT was evaluated.

RESULTS

A total of 101 patients with synchronous low-volume CSPC were included in our analysis with a median follow-up of 44 months. Approximately half of patients were found to have a HiRi pathogenic mutation (48.5%) with TP53 mutations accounting for 75.5% of HiRi mutations. On multivariable cox regression PDT was associated with improvement in OS (HR = 0.37, 95% CI 0.16-0.88; p = 0.03). When stratified by presence of HiRi mutation, PDT was not associated with any clinical outcome. Patients with HiRi mutations demonstrated a median OS of 73 vs 66.8 months (p = 0.28) for no PDT and PDT, respectively. Conversely, patients without a HiRi mutation demonstrated a significant improvement in median OS of 60 vs 105.3 months (p<0.01) for no PDT and PDT, respectively. The p-value for interaction for OS between PDT and HiRi mutation was statistically significant (p<0.01).

CONCLUSION

Here we have identified a high-risk genomic biomarker that appears predictive for response to PDT in men with synchronous low-volume mCSPC. Further work validating these results with prospective randomized data is warranted.

Transcriptomic and clinical heterogeneity of metastatic disease timing within metastatic castration-sensitive prostate cancer

BACKGROUND

Metastatic castration-sensitive prostate cancer (mCSPC) is commonly classified into high- and low-volume subgroups which have demonstrated differential biology, prognosis, and response to therapy. Timing of metastasis has similarly demonstrated differences in clinical outcomes; however, less is known about any underlying biologic differences between these disease states. Herein, we aim to compare transcriptomic differences between synchronous and metachronous mCSPC and identify any differential responses to therapy.

PATIENTS AND METHODS

We performed an international multi-institutional retrospective review of men with mCSPC who completed RNA expression profiling evaluation of their primary tumor. Patients were stratified according to disease timing (synchronous versus metachronous). The primary endpoint was to identify differences in transcriptomic profiles between disease timing. The median transcriptomic scores between groups were compared with the Mann-Whitney U test. Secondary analyses included determining clinical and transcriptomic variables associated with overall survival (OS) from the time of metastasis. Survival analysis was carried out with the Kaplan-Meier method and multivariable Cox regression.

RESULTS

A total of 252 patients were included with a median follow-up of 39.6 months. Patients with synchronous disease experienced worse 5-year OS (39% versus 79%; P < 0.01) and demonstrated lower median androgen receptor (AR) activity (11.78 versus 12.64; P < 0.01) and hallmark androgen response (HAR; 3.15 versus 3.32; P < 0.01). Multivariable Cox regression identified only high-volume disease [hazard ratio (HR) = 4.97, 95% confidence interval (CI) 2.71-9.10; P < 0.01] and HAR score (HR = 0.51, 95% CI 0.28-0.88; P = 0.02) significantly associated with OS. Finally, patients with synchronous (HR = 0.47, 95% CI 0.30-0.72; P < 0.01) but not metachronous (HR = 1.37, 95% CI 0.50-3.92; P = 0.56) disease were found to have better OS with AR and non-AR combination therapy as compared with monotherapy (P value for interaction = 0.05).

CONCLUSIONS

We have demonstrated a potential biologic difference between metastatic timing of mCSPC. Specifically, for patients with low-volume disease, those with metachronous low-volume disease have a more hormone-dependent transcriptional profile and exhibit a better prognosis than synchronous low-volume disease.

Advancements in the identification of EV derived mRNA biomarkers for liquid biopsy of clear cell renal cell carcinomas

OBJECTIVE

To propose EV-derived mRNA as a potential diagnostic biomarker detecting the presence of clear cell renal cell carcinoma (ccRCC). There is currently no kidney cancer specific screening or diagnostic technology. Therefore, one-third of kidney cancer diagnoses occur after the cancer has metastasized and is past curative measures MATERIALS AND METHODS: Urine, plasma, normal tumor adjacent tissue, and tumor tissue was collected from a limited population of ccRCC patients. Extracellular vesicle (EV) isolation was performed on each sample, followed by mRNA extraction from isolated EVs. NanoString nCounter technology was utilized to count the mRNA transcripts present in matched plasma, urine, tumor tissue, and normal tumor adjacent tissue samples.

RESULTS

770 mRNA transcripts related to gene's affecting cancer's progression and metastasis processes were evaluated. Four EV derived mRNA transcripts (ALOX5, RBL2, VEGFA, TLK2) were found specific to urine and tumor tissue samples.

CONCLUSION

Four candidate RCC-specific urine EV biomarkers were identified. However, due to the lack of a true negative control and urine collection techniques, further re-examination is necessary for validation. This study demonstrates the promise of defining disease-specific EV biomarkers in liquid biopsy patient samples.

Multidisciplinary total eradication therapy (TET) in men with newly diagnosed oligometastatic prostate cancer

To evaluate the outcomes of total eradication therapy (TET), designed to eradicate all sites of visible cancer and micrometastases, in men with newly diagnosed oligometastatic prostate cancer (OMPCa). Men with ≤ 5 sites of metastases were enrolled in a prospective registry study, underwent neoadjuvant chemohormonal therapy, followed by radical prostatectomy, adjuvant radiation (RT) to prostate bed/pelvis, stereotactic body radiation therapy (SBRT) to oligometastases, and adjuvant hormonal therapy (HT). When possible, the prostate-specific membrane antigen targeted ¹⁸F-DCFPyL PET/CT (¹⁸F-DCFPyL) scan was obtained, and abiraterone was added to neoadjuvant HT. Twelve men, median 55 years, ECOG 0, median PSA 14.7 ng/dL, clinical stages M0—1/12 (8%), M1a—3/12 (25%) and M1b—8/12 (67%), were treated. ¹⁸F-DCFPyL scan was utilized in 58% of cases. Therapies included prostatectomy 12/12 (100%), neoadjuvant [docetaxel 11/12 (92%), LHRH agonist 12/12 (100%), abiraterone + prednisone 6/12 (50%)], adjuvant radiation [RT 2/12 (17%), RT + SBRT 4/12 (33%), SBRT 6/12 (50%)], and LHRH agonist 12/12 (100%)]. 2/5 (40%) initial patients developed neutropenic fever (NF), while 0/6 (0%) subsequent patients given modified docetaxel dosing developed NF. Otherwise, TET resulted in no additive toxicities. Median follow-up was 48.8 months. Overall survival was 12/12 (100%). 1-, 2-, and 3-year undetectable PSA’s were 12/12 (100%), 10/12 (83%) and 8/12 (67%), respectively. Median time to biochemical recurrence was not reached. The outcomes suggest TET in men with newly diagnosed OMPCa is safe, does not appear to cause additive toxicities, and may result in an extended interval of undetectable PSA.

PET imaging of prostate-specific membrane antigen in prostate cancer: current state of the art and future challenges

BACKGROUND

Prostate-specific membrane antigen (PSMA) is a cell surface enzyme that is highly expressed in prostate cancer (PCa) and is currently being extensively explored as a promising target for molecular imaging in a variety of clinical contexts. Novel antibody and small-molecule PSMA radiotracers labeled with a variety of radionuclides for positron emission tomography (PET) imaging applications have been developed and explored in recent studies.

METHODS

A great deal of progress has been made in defining the clinical utility of this class of PET agents through predominantly small and retrospective clinical studies. The most compelling data to date has been in the setting of biochemically recurrent PCa, where PSMA-targeted radiotracers have been found to be superior to conventional imaging and other molecular imaging agents for the detection of locally recurrent and metastatic PCa.

RESULTS

Early data, however, suggest that initial lymph node staging before definitive therapy in high-risk primary PCa patients may be limited, although intraoperative guidance may still hold promise. Other examples of potential promising applications for PSMA PET imaging include non-invasive characterization of primary PCa, staging and treatment planning for PSMA-targeted radiotherapeutics, and guidance of focal therapy for oligometastatic disease.

CONCLUSIONS

However, all of these indications and applications for PCa PSMA PET imaging are still lacking and require large, prospective, systematic clinical trials for validation. Such validation trials are needed and hopefully will be forthcoming as the fields of molecular imaging, urology, radiation oncology and medical oncology continue to define and refine the utility of PSMA-targeted PET imaging to improve the management of PCa patients.

Differential carbohydrate expression in tumorigenic vs nontumorigenic prostate cell-lines

Death from prostate cancer is most frequently a result of metastatic disease. A key step in the process of metastasis is the attachment of circulatory tumor cells to target organ endothelium. This process is thought to be mediated by lectins, a class of cell surface proteins that bind two or more carbohydrate groups. Using fluorescent microscopy and fluorescein isothiocyanate (FITC) conjugated lectins, the presence of various carbohydrates was examined in the following tumorigenic and non-tumorigenic cell lines: rat prostate epithelial (EPYP-2, EPYP-1), rat prostate endothelial (YPEN-2, YPEN-1, YPEN-2PV), Dunning rat prostate cancer cell lines (MLL, ML, AT6.3, AT.1, AT2.1, GP9F3), and three tumorigenic human prostate cell lines (LNCaP, PC3, PC3 bone). The lectin Triticum vulgaris (WGA) was found to readily bind the carbohydrates N-acetylglucosamine and sialic acid on the plasma membrane of tumorigenic cell lines. Interestingly, WGA bound carbohydrates located to the nucleus and cytoplasm in non-tumorigenic cell lines, indicating that N-acetylglucosamine and sialic acid residues are preferentially expressed on the cell membrane of prostate cancer cells. Lectin staining patterns in cell lines of varying metastatic potential revealed no significant difference between highly metastatic vs. low metastatic cell lines. Observations revealed an absence of N-acetylgalactosamine and L-fucose in all rat Dunning, epithelial and endothelial cell lines as well as all human prostate cancer cell lines except for the androgen insensitive human prostate cancer cell line PC3, in which L-fucose residues were detected in the nucleus and on the plasma membrane. PC3 bone cells, which metastasized selectively to bone, demonstrated the presence of galactose residues whereas PC3 cells did not, suggesting that preference for target organ endothelium may be influenced by the expression of carbohydrate residues. These data indicate that differential carbohydrate expression may play an important role in prostate cancer biology.

Effect of CCL2 on survival of breast cancer MDA-MB-231 cells via inhibition of apoptosis

e22176

Background: The cytokine CCL2 (Chemokine (C-C) motif ligand 2 or monocyte chemo attractant protein-1 MCP-1) has been shown to play an important role in breast cancer progression by promoting angiogenesis and migration. CCL2 is over-expressed by breast cancer cells as well as by macrophages and mesenchymal stem cells in the tumor micro-environment. We studied the effects of CCL2 and IL-6 on survival of breast cancer MDA-MB-231 cells. Methods: Cytokine expression including of CCL2 and IL- 6 were analyzed in supernatants from MDA-MB-231 cells using cytokine antibody array (Human Antibody Array 3; Ray Biotech, Inc). Serum starved MDA-MB-231 cells were treated with CCL2 (75 ng/mL) and IL-6 (100 ng/mL; both from Apollo Cytokine Research). Cell viability in response to treatment was analyzed at serial time points by cell proliferation assay WST-1 (Roche Applied Science). Protein expression of genes of interest was studied by Western blot. Results: In contrast to primary breast tumor cells, MDA-MB-231 cells express minimal CCL2 at baseline. MDA-MB-231 cells also exhibit low expression of IL-6. Stimulation of MDA-MB-231 cells with either exogenous CCL2 or exogenous IL-6 did not increase levels of the other cytokine. In MDA-MB-231 cells, CCL2, alone and in combination with IL-6, promotes survival in serum starved conditions. Treatment of MDA-MB-231 cells with CCL2 leads to survivin up-regulation beginning at 48 hours as determined by immunoblotting analysis. CCL2 in combination with IL-6 inhibits the cleavage of PARP, lamin and caspase3. Conclusions: There is minimal endogenous expression of CCL2 in MDA-MB-231 cells. CCL2 from the tumor micro-environment promotes survival of MDA-MB-231 cells associated with up-regulation of survivin. IL-6 may play a syngeristic role with CCL2 in promoting survival of MDA-MB-231 cells. We plan to explore the role of survivin up-regulation in protecting cells from cell death. Our findings raise the possibility of utilizing neutralizing antibodies against CCL2 in therapy of breast cancer.

No significant financial relationships to disclose.

The bone marrow niche: habitat to hematopoietic and mesenchymal stem cells, and unwitting host to molecular parasites

In post-fetal life, hematopoiesis occurs in unique microenvironments or 'niches' in the marrow. Niches facilitate the maintenance of hematopoietic stem cells (HSCs) as unipotent, while supporting lineage commitment of the expanding blood populations. As the physical locale that regulates HSC function, the niche function is vitally important to the survival of the organism. This places considerable selective pressure on HSCs, as only those that are able to engage the niche in the appropriate context are likely to be maintained as stem cells. Since niches are central regulators of stem cell function, it is not surprising that molecular parasites like neoplasms are likely to seek out opportunities to harvest resources from the niche environment. As such, the niche may unwittingly participate in tumorigenesis as a leukemic or neoplastic niche. The niche may also promote metastasis or chemo-resistance of hematogenous neoplasms or solid tumors. This review focuses on what is known about the physical structures of the niche, how the niche participates in hematopoiesis and neoplastic growth and what molecules are involved. Further understanding of the interactions between stem cells and the niche may be useful for developing therapeutic strategies.

The role of sialomucin CD164 (MGC-24v or endolyn) in prostate cancer metastasis

BACKGROUND

The chemokine stromal derived factor-1 (SDF-1 or CXCL12) and its receptor CXCR4 have been demonstrated to be crucial for the homing of stem cells and prostate cancers to the marrow. While screening prostate cancers for CXCL12-responsive adhesion molecules, we identified CD164 (MGC-24) as a potential regulator of homing. CD164 is known to function as a receptor that regulates stem cell localization to the bone marrow.

RESULTS

Using prostate cancer cell lines, it was demonstrated that CXCL12 induced both the expression of CD164 mRNA and protein. Functional studies demonstrated that blocking CD164 on prostate cancer cell lines reduced the ability of these cells to adhere to human bone marrow endothelial cells, and invade into extracellular matrices. Human tissue microarrays stained for CD164 demonstrated a positive correlation with prostate-specific antigen levels, while its expression was negatively correlated with the expression of androgen receptor.

CONCLUSION

Our findings suggest that CD164 may participate in the localization of prostate cancer cells to the marrow and is further evidence that tumor metastasis and hematopoietic stem cell trafficking may involve similar processes.

Preliminary study of immunomagnetic quantification of circulating tumor cells in patients with advanced disease

OBJECTIVES

To enumerate the amount of circulating tumor cells (CTCs) in patients with advanced prostate cancer and to investigate the relationship between these numbers, prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSM) expression, and clinical parameters.

METHODS

Whole blood was collected in proprietary CellSave tubes. Mononuclear cell fractions were isolated using epithelial cell antibody-coated magnetic nanoparticles. On one half of each immunomagnetically enriched cell fraction, automated fluorescent microscopy was used to identify the epithelial tumor cells. From the remainder of each sample, RNA extraction, cDNA synthesis, and polymerase chain reaction amplification of PSA and PSM were performed.

RESULTS

Eighty-four patients with advanced prostate cancer submitted 130 samples for analysis. Intact CTCs were identified in 62% of samples; 83.3% of CTC-positive and 0% of CTC-negative samples were reverse transcriptase-polymerase chain reaction positive for PSA and PSM (P = 0.001). A significant positive correlation was found between the CTC number and PSA (r = 0.49), alkaline phosphatase (r = 0.47), and lactate dehydrogenase (r = 0.55) levels, and a significant negative correlation with hemoglobin (r = -0.35). The initial Gleason grade, prior therapy, current therapy, and type of metastasis (bone, soft tissue) did not correlate significantly with the CTC number.

CONCLUSIONS

The presence of intact CTCs and the expression of PSA and PSM demonstrated robust agreement. The tumor cell numbers reflected current disease status and correlated significantly with the clinical disease indicators of PSA, hemoglobin, and liver function tests. These findings warrant further investigation of the diagnostic and prognostic value of enumerating intact CTCs.

Prostate carcinoma skeletal metastases: cross-talk between tumor and bone

The majority of men with progressive prostate cancer develop metastases with the skeleton being the most prevalent metastatic site. Unlike many other tumors that metastasize to bone and form osteolytic lesions, prostate carcinomas form osteoblastic lesions. However, histological evaluation of these lesions reveals the presence of underlying osteoclastic activity. These lesions are painful, resulting in diminished quality of life of the patient. There is emerging evidence that prostate carcinomas establish and thrive in the skeleton due to cross-talk between the bone microenvironment and tumor cells. Bone provides chemotactic factors, adhesion factors, and growth factors that allow the prostate carcinoma cells to target and proliferate in the skeleton. The prostate carcinoma cells reciprocate through production of osteoblastic and osteolytic factors that modulate bone remodeling. The prostate carcinoma-induced osteolysis promotes release of the many growth factors within the bone extracellular matrix thus further enhancing the progression of the metastases. This review focuses on the interaction between the bone and the prostate carcinoma cells that allow for development and progression of prostate carcinoma skeletal metastases.

Delineation of prognostic biomarkers in prostate cancer

Prostate cancer is the most frequently diagnosed cancer in American men. Screening for prostate-specific antigen (PSA) has led to earlier detection of prostate cancer, but elevated serum PSA levels may be present in non-malignant conditions such as benign prostatic hyperlasia (BPH). Characterization of gene-expression profiles that molecularly distinguish prostatic neoplasms may identify genes involved in prostate carcinogenesis, elucidate clinical biomarkers, and lead to an improved classification of prostate cancer. Using microarrays of complementary DNA, we examined gene-expression profiles of more than 50 normal and neoplastic prostate specimens and three common prostate-cancer cell lines. Signature expression profiles of normal adjacent prostate (NAP), BPH, localized prostate cancer, and metastatic, hormone-refractory prostate cancer were determined. Here we establish many associations between genes and prostate cancer. We assessed two of these genes-hepsin, a transmembrane serine protease, and pim-1, a serine/threonine kinase-at the protein level using tissue microarrays consisting of over 700 clinically stratified prostate-cancer specimens. Expression of hepsin and pim-1 proteins was significantly correlated with measures of clinical outcome. Thus, the integration of cDNA microarray, high-density tissue microarray, and linked clinical and pathology data is a powerful approach to molecular profiling of human cancer.

Preclinical mechanisms of action of docetaxel and docetaxel combinations in prostate cancer

Docetaxel, a semisynthetic taxane, has exhibited significant single-agent activity against prostatic tumors. In phase I/II studies, single-agent docetaxel and the combination of docetaxel plus estramustine were effective in inducing prostate-specific antigen reductions of > or =50% in men with androgen-independent prostate cancer (AIPC). The underlying reason for docetaxel's clinical activity against prostate cancer has been a focus of ongoing research. Docetaxel is believed to have a twofold mechanism of antineoplastic activity: (1) inhibition of microtubular depolymerization, and (2) attenuation of the effects of bcl-2 and bcl-xL gene expression. Taxane-induced microtubule stabilization arrests cells in the G(2)M phase of the cell cycle and induces bcl-2 phosphorylation, thereby promoting a cascade of events that ultimately leads to apoptotic cell death. In preclinical studies, docetaxel had a higher affinity for tubulin and was shown to be a more potent inducer of bcl-2 phosphorylation than paclitaxel. Laboratory evidence also supports the clinical evaluation of docetaxel-based combinations that include agents such as trastuzumab and/or estramustine. The pathways for docetaxel-induced apoptosis appear to differ in androgen-dependent and androgen-independent prostate cancer cells. Further elucidation of these differences will be instrumental in designing targeted regimens for the treatment of localized and advanced prostate cancer.

E-cadherin expression in prostate cancer: a broad survey using high-density tissue microarray technology

E-cadherin is a calcium 2+-dependent cell-adhesion molecule that determines epithelial development in the embryo and maintains adult differentiated epithelium and homeostasis. Aberrant or decreased expression has been reported to be associated with prostate carcinoma progression. The degree of E-cadherin expression in prostate cancer remains controversial. Some studies have reported decreased expression of E-cadherin as tumors advance and metastasize. Other studies have not demonstrated this relationship. To address these variations, we undertook a study to systematically evaluate E-cadherin expression in a broad range of prostate tissue. Benign prostate, clinically localized prostate cancer, and hormone-refractory metastatic prostate cancer were analyzed under uniform conditions using high-density tissue microarrays (TMA). Formalin-fixed, paraffin-embedded prostate carcinoma from men with clinically localized prostate carcinoma and autopsy material from men who died of widely metastatic, hormone-refractory prostate carcinoma were arrayed into 6 high-density TMA blocks. Benign and atrophic prostate tissue and high-grade prostatic intraepithelial neoplasia (PIN) were also included from the clinically localized cases. Immunohistochemistry was performed using the immunoglobulin G1 mouse monoclonal antibody (HECD-1; Zymed, San Francisco, CA). Membranous staining was recorded as low (aberrant) or high (normal). E-cadherin expression was considered aberrant if less than 70% of the cells had strong membranous staining. A total of 1,220 prostate TMA samples were analyzed. High (normal) E-cadherin expression was seen in 87% of 757 benign, 80% of 41 high-grade PIN, 82% of 325 prostate carcinoma and 90% of 97 hormone-refractory prostate carcinoma TMA samples. Mean E-cadherin expression was determined for each of the 128 clinically localized prostate cancer cases. Aberrant E-cadherin expression showed a statistical trend toward an association with positive surgical margins (P =.012), higher Gleason score (P =.18), and prostate-specific antigen (PSA) failure (Kaplan-Meier analysis, log-rank P =.09). There was a statistically significant association between aberrant E-cadherin expression and larger tumor size (P =.01). No significant associations were seen with extraprostatic extension and seminal vesicle invasion. The current study shows a broad-spectrum approach to evaluating E-cadherin protein expression in prostate carcinoma. Clinically localized prostate tumors, treated with surgery alone, show a high level of E-cadherin expression. Aberrant expression was identified in tumors with positive surgical margins, higher Gleason score, and a higher rate of PSA failure. However, these trends were not statistically significant. A statically significant association between aberrant E-cadherin expression and larger tumor size was identified. In the metastatic hormone-refractory prostate tumors, E-cadherin expression was vastly expressed, and only rare cases had aberrant expression. Therefore, the findings of this study are most consistent with a transient down-regulation of E-cadherin in localized prostate cancer. Metastatic prostate cancer shows strong E-cadherin expression as determined by anti-E-cadherin antibody HECD-1.

Chemotherapy in patients with prostate specific antigen-only disease after primary therapy for prostate carcinoma: a phase II trial of oral estramustine and oral etoposide

BACKGROUND

A Phase II study was initiated to evaluate the effectiveness of an oral regimen of etoposide and estramustine in patients with early recurrent prostate carcinoma.

METHODS

Patients with early recurrent prostate carcinoma as indicated by an increasing prostate specific antigen (PSA) level and without any evidence of metastatic disease were treated with oral etoposide 50 mg/m2/day and estramustine 15 mg/kg/day in divided doses for 21 days, followed by a 7-day rest period. Patients received a maximum of four cycles.

RESULTS

Eighteen patients were entered in this study. The median serum PSA was 3.1 (range, 0.3-30.3) at the time of entry into the trial. Sixteen patients were assessable for response. Serum PSA declined to undetectable levels in 13 patients with 2 additional patients meeting the criteria for partial response; the median duration of response was 8.5 months (range, 1-18 months). Most patients developed gastrointestinal, cardiac, or hematologic complications. Grade 3 toxicities included neutropenia (one patient), deep venous thrombosis (three patients), and chest pain (one patient). One patient developed acute myelogenous leukemia (French-American-British, acute myelogenous leukemia M5) 23 months after initiating the chemotherapy.

CONCLUSIONS

The combination of oral etoposide and oral estramustine resulted in a high rate but only a short duration of response in patients with early recurrent prostate carcinoma. The regimen was poorly tolerated, and the toxicity was significant. This regimen should not be considered standard therapy for the treatment of early recurrent prostate carcinoma, but further exploration of treatment in this setting is warranted.

Establishment and characterization of a new human prostatic cancer cell line: DuCaP

BACKGROUND

The lack of appropriate, clinically relevant, cell-based model systems has limited prostate cancer research and the development of new therapeutic modalities. Here we report the isolation and characterization of a new adherent prostate cancer cell line, derived from the dura mater of a cancer patient.

METHODS

Prostate cancer tissue was harvested at autopsy from a metastatic lesion to the dura mater of a patient with hormone refractory prostate cancer. This tissue was xenografted into SCID mice and later harvested and plated on tissue culture dishes. For characterization, soft agar clonegenic assay, in vivo xenograft growth, in vitro doubling time, karyotype analysis, immunocytochemistry for cytokeratin-18, androgen receptor, and PAP (prostatic acid phosphatase) expression, RT PCR for PAP, PSMA (prostate specific membrane antigen), expression and northern and western blot analysis to determine expression of Rb and p53, were performed.

RESULTS

DuCap grows in vitro (passage 55), forms colonies in soft agar, produces tumors in SCID mice (xenograft passage 12), and is androgen sensitive. DNA content was hypertriploid. PSA was detected in mouse serum and media. Cells were AR, PAP and cytokeratin-18 positive by immunocytochemistry. PSMA and PAP were detected by RT-PCR. AR, P53, and Rb were expressed in Northern blot analysis. P53 protein was detected in Western blot analysis but Rb protein was not.

CONCLUSIONS

This cell line exhibits many phenotypic characteristics of clinical prostate carcinoma, including expression of PSA, PSMA, PAP and AR.

A phase II trial of estramustine and etoposide in hormone refractory prostate cancer: A Southwest Oncology Group trial (SWOG 9407)

BACKGROUND

The combination of oral estramustine and oral etoposide has generated response rates of 40-50% in patients with hormone refractory prostate cancer in single institution trials. This study tested this regimen in a multi-institutional setting.

METHODS

Fifty-five patients were accrued over a period of 4 months between 1 March 1996 and 1 July 1996. Two patients were not analyzable and two patients were ineligible. They were given an oral regimen consisting of estramustine 15 mg/kg/day (capped at 1120 mg per day) and etoposide 50 mg/M(2)/day, days 1-21 every 28 days. Patients received a median of two cycles of therapy.

RESULTS

Toxicities included 11 patients (20%) with grades 3 or 4 granulocytopenia, 5 patients (10%) with grades 3 or 4 edema, and 3 patients (6%) with a thrombotic event. There were two treatment-related deaths, one as a result of anemia and the other as a result of a myocardial infarction. Of the 32 men who received at least 2 cycles of therapy, 7 men (22%) demonstrated a partial response to this regimen as measured by prostate-specific antigen (PSA) criteria of a 50% decline from pretreatment values.

CONCLUSIONS

This trial demonstrates the toxicity of estramustine delivered in high dose. It also illustrates the difficulty of conducting phase II trials in prostate cancer in the cooperative group setting where the experience and comfort level of oncologists with new agents is less than that of the physicians at the institution where the therapy was developed. As the activity of this regimen with low-dose estramustine is defined, further multi-institutional studies may be warranted.

VCaP, a cell-based model system of human prostate cancer

OBJECTIVES

We report the isolation and characterization of a novel prostate cancer cell line derived from a vertebral metastatic lesion, Vertebral-Cancer of the Prostate (VCaP).

METHODS

Prostate cancer tissue was harvested at autopsy from a metastatic lesion to a lumbar vertebral body of a patient with hormone refractory prostate cancer. This tissue was aseptically xenografted into SCID mice and later harvested and plated on tissue culture dishes. For characterization, soft agar clonegenic assay, in vivo xenograft growth, in vitro doubling time, karyotype analysis, immunocytochemistry for cytokeratin-18 expression immunochemistry for PSA (prostate specific antigen), RT PCR for PAP (prostatic acid phosphatase) and northern blot and western blot analysis to determine expression of Rb and p53, were performed. Androgen receptor expression was measured by transient transfection with a luciferase reporter construct.

RESULTS

VCaP cells are immortal in vitro and can be passaged serially in vivo. They express large quantities of prostate specific antigen (PSA). This cell line also expresses prostatic acid phosphatase (PAP), cytokeratin-18 and the androgen receptor, and is androgen sensitive in vitro and in vivo.

CONCLUSIONS

This cell line was derived from a metastatic tumor to the vertebrae of a prostate cancer patient. It exhibits many of the characteristics of clinical prostate carcinoma, including expression of PSA, PAP, and AR. We believe that VCaP will be a useful addition to the existing models of prostate cancer, and enable more advanced study of the mechanisms of prostate cancer progression and metastasis.

Different docetaxel-induced apoptotic pathways are present in prostate cancer cell lines LNCaP and PC-3

OBJECTIVES

To investigate the molecular machinery of docetaxel (Taxotere)-initiated death signaling on prostate cancer cell lines LNCaP and PC-3. Taxotere is a member of the taxane family of chemotherapeutic agents. It has been shown to disrupt microtubule dynamics causing mitotic arrest, which leads to cell death. Taxotere has demonstrated induction of cell death in LNCaP and PC-3 cells. However, the pathways by which apoptosis occurs differ in each cell line.

METHODS

The prostate cancer cell lines, LNCaP and PC-3, were treated with 40 nM Taxotere for various lengths of time (0.5 to 24 hours). Western blot analysis was used for protein analysis.

RESULTS

LNCaP cells demonstrated caspase-3 and caspase-7 cleavage, and PC-3 cells demonstrated only caspase-8 and BH3-interacting domain death agonist cleavage. Only LNCaP cells were observed to express clusterin expression; PC-3 cells expressed a novel apoptosis inhibitor, survivin.

CONCLUSIONS

In this study, we demonstrated two distinctly different Taxotere-induced apoptotic pathways in LNCaP and PC-3 cells that may be of clinical importance when treating prostate cancer.

Preferential adhesion of prostate cancer cells to bone is mediated by binding to bone marrow endothelial cells as compared to extracellular matrix components in vitro

We have demonstrated previously that the preferential adhesion of prostate cancer cells to human bone marrow endothelial (HBME) cells may contribute to their preferential metastasis to bone. Although a subject of debate, it has been postulated that the endothelial cells of the bone marrow are fenestrated. It is unknown therefore whether prostate cancer cells adhere preferentially to the extracellular matrix (ECM) or the endothelial cells. It has also been demonstrated in other organ systems that the types of cell adhesion molecules on the surface of endothelial cells lining the organ microvasculature are determined, in part, by the ECM of the organ. We investigated how prostate cancer cell adhesion to HBME cells is affected by growing HBME cells on selected organ-derived ECM proteins in vitro. Growth of HBME cells and immortalized human aortic endothelial cells on bone, kidney, and placenta ECM proteins significantly increased their ability to bind PC-3 cells. This increased adhesion was not dose dependent and was not demonstrated with human dermal microvascular endothelial cells. Scanning electron microscopic analysis demonstrated that prostate cancer cells adhered directly to the endothelial cells and not to the underlying substrata. These results suggest that unidentified cell adhesion molecules are expressed or up-regulated on the apical surfaces of human aortic endothelial cells and HBME cells grown on bone, kidney, and placenta ECMs. These results also strongly demonstrate that the adhesion of prostate cancer cells to bone may be initiated by direct binding to endothelial cells rather than direct binding to exposed ECM components.

Prostate cancer cell adhesion to quiescent endothelial cells is not mediated by beta-1 integrin subunit

BACKGROUND

Previous studies have reported that tumor cells' adhesion to quiescent endothelial cell is mediated by beta-1 integrins. The aim of this study was to determine the role beta-1 integrins play in prostate cancer cell adhesion to human bone marrow endothelial cells (HBME) and human aortic endothelial cells (HAEC).

MATERIALS AND METHODS

A well described blocking antibody to beta-1 integrin subunit was used in adhesion assays to determine the role of beta-1 integrin subunit in the adhesion of PC-3 cells to both HBME cells and HAEC.

RESULTS

Antibody to the beta-1 integrin subunit failed to reduce PC-3 adhesion to HBME and HAEC, yet this same antibody significantly reduced adhesion of PC-3 cells to fibronectin coated wells.

CONCLUSIONS

The data suggest that metastasis of prostate cancer cells to bone may be mediated, in part, by preferential adhesion to HBME cells; but beta-1 integrins most likely are not involved in this interaction.

Treatment of androgen-independent prostate cancer using antimicrotubule agents docetaxel and estramustine in combination: an experimental study

BACKGROUND

Estramustine in combination with other chemotherapeutic agents has demonstrated synergy in hormone-refractory prostate cancer. Docetaxel has demonstrated antineoplastic activity in a variety of chemotherapeutic-unresponsive tumors. We evaluated the effects of estramustine and docetaxel in preclinical models of prostate cancer.

METHODS

Cell viability of PC-3 and MAT-LyLu (MLL) cells were assessed 48 hr after drug treatment. For in vivo studies, each flank of five animals in six groups was injected with 1 x 10(6) MLL cells: control, estramustine, docetaxel (low- and high-dose), and low- and high-dose docetaxel with estramustine. Animals were treated on days 4 and 11, and sacrificed on day 14.

RESULTS

The IC(50) value for docetaxel was 2 nM in the PC-3 cells and 40 nM in the MLL cells. The addition of 100 nM of estramustine did not alter the IC(50) value for PC-3 cells. In the MLL cells, however, the IC(50) value was lowered to 15 nM. In vivo, low-dose docetaxel with estramustine demonstrated antineoplastic activity similar to that of high-dose docetaxel alone, suggesting additive activity between the drugs.

CONCLUSIONS

These results demonstrate that when used in combination, docetaxel and estramustine can be more effective at lower dosages than when the individual drugs are used alone.

Genetic characterization of immortalized human prostate epithelial cell cultures. Evidence for structural rearrangements of chromosome 8 and i(8q) chromosome formation in primary tumor-derived cells

We have utilized a combination of conventional and spectral karyotyping (SKY) techniques and allelotype analysis to assess numerical and structural chromosome alterations in two cell lines derived from normal human prostatic epithelium, and three cell lines derived from human prostate primary tumor epithelium, immortalized with the E6 and E7 transforming genes of human papilloma virus (HPV) 16 or the large T-antigen gene of simian virus 40 (SV40). These studies revealed trisomy for chromosome 20 and rearrangements involving chromosomes 3, 4, 8, 9, 10, 16, 17, 18, 19, 21, or 22. In addition, the four HPV-immortalized cell lines exhibited extensive duplications or translocations involving the 11q chromosomal region. Interestingly, allelotyping data disclosed loss of 8p sequences in two of the three primary tumor-derived cell lines, and SKY data revealed that the loss of 8p sequences was directly due to i(8q) chromosome formation and/or other structural alterations of chromosome 8. This provides intriguing evidence that 8p loss in primary human prostate tumors may, in some cases, result from complex structural rearrangements involving chromosome 8. Moreover, the data reported here provide direct evidence that such complex structural rearrangements sometimes include i(8q) chromosome formation.

Decreased galectin-3 expression in prostate cancer

BACKGROUND

Galectin-3 is a carbohydrate-binding protein whose level of expression has been shown to be correlated with metastatic potential in a number of different tumor types. The purpose of this investigation was to examine galectin-3 expression in several tumorigenic and nontumorigenic prostate cell lines and prostate tissue samples.

METHODS

The expression of galectin-3 in cell lines and tissue samples was evaluated by tissue immunohistochemistry and Western blot analysis.

RESULTS

Human cell lines PC-3M, PC-3, DU-145, PrEC-1, and MCF10A demonstrated the presence of galectin-3. Galectin-3 was not detected in TSU-pr1 and LNCaP by Western blot analysis. We furthered our studies by examining a series of human prostate tissue samples for expression of galectin-3. Overall, approximately 60-70% of the normal tissue examined demonstrated heterogenous expression of galectin-3. In stage II tumors, however, there was a dramatic decrease in galectin-3 expression in both PIN and tumor sections, with only 10.5% (2/19) of these samples expressing this protein. Stage III tumors also demonstrated a decreased expression of galectin-3, although this downregulation was not as dramatic, with 35% of PIN samples and 52% of tumor tissue expressing galectin-3 (P < 0.01).

CONCLUSIONS

These data demonstrate that galectin-3 is downregulated in prostate cancer. The altered downregulation pattern of galectin-3 observed between tumor stages suggests different roles for galectin-3 in the progression of prostate cancer.

Cell adhesion and chemotaxis in prostate cancer metastasis to bone: a minireview

Bone metastasis is a common phenomenon in patients with advanced prostate cancer. The molecular and cellular mechanisms involved in this process are not well understood. Past reviews on this subject primarily focused on prostate tumor growth in the bone marrow and the effects this growth has on bone homeostasis (ie osteoblastic and osteolytic). Cell chemotaxis and adhesion are also important for site-specific metastasis. In this review we have focused on chemotactic and cell adhesion molecules potentially involved in prostate cancer metastasis to bone. In addition, recently developed animal models for prostate cancer metastasis to bone are discussed. Prostate Cancer and Prostatic Diseases (2000) 3, 6-12

Phenotypic characterization of immortalized normal and primary tumor-derived human prostate epithelial cell cultures

BACKGROUND

Cell lines can provide powerful model systems for the study of human tumorigenesis. However, the human prostate cancer cell lines studied most intensively by investigators (PC3, DU145, and LNCaP) were established from metastatic lesions, and it is unlikely that they accurately recapitulate the genetic composition or biological behavior of primary prostate tumors. Cell lines more appropriate for the study of human prostate primary tumors would be those derived from spontaneously immortalized cells; unfortunately, explanted prostate cells survive only short-term in culture, and rarely immortalize spontaneously. Therefore, we examined whether cell lines developed through viral gene-mediated immortalization of human normal or primary tumor prostate epithelium express aspects of the normal or malignant phenotypes, and could serve as appropriate models for normal or transformed human prostatic epithelium.

METHODS

To accomplish these goals, we assessed the phenotypic expression of cell cultures established through the immortalization of normal (1532N, 1535N, 1542N, and PrEC-T) or malignant (1532T, 1535T, and 1542T) human prostate epithelium with the E6 and E7 genes of HPV-16, or the large T antigen gene of SV40.

RESULTS

Examination of these cell lines for their proliferative rates and their abilities to grow with or without serum or androgen stimulation, to form colonies in soft agar, or to form tumors in vivo, suggests that they may serve as valid, useful tools for the elucidation of prostate tumorigenesis. Moreover, the observation of structural alterations involving chromosome 8, including gain of 8q in 3 of the 4 cell lines expressing aspects of the malignant phenotype, implies that these cell lines accurately recapitulate the genetic composition of primary prostate tumors.

CONCLUSIONS

Taken together, these data suggest that cell lines generated from immortalized normal or primary tumor epithelium may be useful for the elucidation of early transforming events in the prostate.

Inhibition of prostate specific antigen expression by genistein in prostate cancer cells

Recent studies have provided convincing evidence for the role of soy-isoflavones, particularly genistein, in the inhibition of prostate cancer cell growth. Prostate specific antigen (PSA) is a biological marker used to detect and monitor the treatment of prostate cancer patients. Previous studies have documented that isoflavones can inhibit the secretion of PSA in the androgen-dependent prostate cancer cell line, LNCaP, however, the effects of genistein on androgen-independent PSA expression has not been explored. In this study, we have utilized a prostate cancer cell line, VeCaP, which expresses PSA in an androgen-independent manner, to determine the effects of genistein on cell proliferation and PSA expression. Here we show that genistein inhibits cell growth similarly in both the LNCaP and VeCaP cell lines, but has differential effects on PSA expression. We demonstrate using concentrations of genistein that have been detected in the serum of humans consuming a soy-rich diet, that genistein decreases PSA mRNA, protein expression and secretion. Conversely, only high concentrations of genistein inhibited PSA expression in VeCaP cells. Additionally, we have demonstrated that genistein inhibits cell proliferation independent of PSA signaling pathways, providing further evidence to support the role of genistein as a chemopreventive/therapeutic agent for prostate cancer irrespective of androgen responsiveness.

Tumor necrosis factor-alpha-induced apoptosis in prostate cancer cells through inhibition of nuclear factor-kappaB by an IkappaBalpha "super-repressor"

Prostate cancer patients experiencing a relapse in disease often express high serum tumor necrosis factor-alpha (TNF-alpha) levels. Many androgen-insensitive prostate cancer cells are TNF-alpha insensitive because of the expression of antiapoptotic genes as part of the nuclear factor-kappaB (NF-kappaB) family of transcription factors. NF-kappaB stimulates gene transcription when expressed in the nucleus; however, in resting cells, this nuclear import is prevented by association with the cytoplasmic inhibitor IkappaBalpha. This cytoplasmic retention of NF-kappaB is uncoupled by many extracellular signals including low levels of TNF-alpha. During normal cell activation, nuclear translocation of NF-kappaB is preceded by phosphorylation and degradation of IkappaBalpha. When phosphorylation is blocked, IkappaBalpha remains intact, thereby blocking NF-kappaB translocation to the nucleus and subsequent activation of antiapoptotic genes that cause TNF-alpha insensitivity. We tested whether a "super-repressor" of NF-kappaB activity could be transfected into prostate cancer cells and make them TNF-alpha sensitive. PC-3 and LNCaP cells were stimulated with TNF-alpha (10 ng/ml) for 24 h in the presence or absence of the IkappaBalpha "super-repressor" (p6R-IkappaB(S32A + S36A)). NF-kappaB activity was measured by electrophoretic mobility shift assay and the steady state levels of the cytoplasmic IkappaBalpha protein were measured by Western blot. Secretory IL-6 and IL-6 mRNA were measured by ELISA. p6R-IkappaB(S32A + S36A) blocked the stimulation of NF-kappaB activity by TNF-alpha in prostate cancer cells. It also subsequently decreased IL-6 production by TNF-alpha. We conclude that these data demonstrate that inhibition of NF-kappaB selectively sensitizes previously insensitive prostate cancer cells to TNF-alpha.

Recent advances in chemotherapy for advanced prostate cancer

Recently, several important studies have validated prostate-specific antigen (PSA) as a reliable measure of response to chemotherapeutic treatment in advanced hormone-refractory prostate cancer. Furthermore, although chemotherapy in this setting has always been considered palliative, several analyses of recent clinical trials have demonstrated a significant association between declines in PSA values of 50% or more and prolonged survival. Mitoxantrone, in combination with prednisone, has been shown to provide significant palliation and improved quality of life. The use of combinations of chemotheraputic agents also seems to provide significantly superior objective and subjective responses compared with single-agent regimens. In particular, estramustine has been shown to synergize many of the agents used in prostate cancer treatment and has been demonstrated to provide significant palliation and decline in PSA levels in combination with vinblastine, vinorelbine, etoposide, paclitaxel, and docetaxel. The results of several important trials of the taxanes both as single agents and in combination with estramustine have been completed in the past year and have demonstrated that these agents are very effective in the treatment of hormone-refractory prostate cancer.

Oral chemotherapy in the treatment of hormone-refractory prostate cancer

Oral chemotherapy has become a major component of the treatment of advanced prostate cancer. The recognition that prostate cancer grows very slowly and must be treated continuously with active agents has led to the development of several therapeutic regimens. These regimens employ oral agents such as estramustine, cyclophosphamide, and etoposide, as they can be taken on a daily basis at home by the patients. These regimens have demonstrated activity in patients with hormone-refractory prostate cancer; declines in both prostate specific antigen and soft tissue lesions have been demonstrated.