Systematic elucidation and pharmacological targeting of tumor-infiltrating regulatory T cell master regulators

Due to their immunosuppressive role, tumor-infiltrating regulatory T cells (TI-Tregs) represent attractive immuno-oncology targets. Analysis of TI vs. peripheral Tregs (P-Tregs) from 36 patients, across four malignancies, identified 17 candidate master regulators (MRs) as mechanistic determinants of TI-Treg transcriptional state. Pooled CRISPR-Cas9 screening in vivo, using a chimeric hematopoietic stem cell transplant model, confirmed the essentiality of eight MRs in TI-Treg recruitment and/or retention without affecting other T cell subtypes, and targeting one of the most significant MRs (Trps1) by CRISPR KO significantly reduced ectopic tumor growth. Analysis of drugs capable of inverting TI-Treg MR activity identified low-dose gemcitabine as the top prediction. Indeed, gemcitabine treatment inhibited tumor growth in immunocompetent but not immunocompromised allografts, increased anti-PD-1 efficacy, and depleted MR-expressing TI-Tregs in vivo. This study provides key insight into Treg signaling, specifically in the context of cancer, and a generalizable strategy to systematically elucidate and target MR proteins in immunosuppressive subpopulations.

The 2019 Genitourinary Pathology Society (GUPS) White Paper on Contemporary Grading of Prostate Cancer

CONTEXT.—

Controversies and uncertainty persist in prostate cancer grading.

OBJECTIVE.—

To update grading recommendations.

DATA SOURCES.—

Critical review of the literature along with pathology and clinician surveys.

CONCLUSIONS.—

Percent Gleason pattern 4 (%GP4) is as follows: (1) report %GP4 in needle biopsy with Grade Groups (GrGp) 2 and 3, and in needle biopsy on other parts (jars) of lower grade in cases with at least 1 part showing Gleason score (GS) 4 + 4 = 8; and (2) report %GP4: less than 5% or less than 10% and 10% increments thereafter. Tertiary grade patterns are as follows: (1) replace "tertiary grade pattern" in radical prostatectomy (RP) with "minor tertiary pattern 5 (TP5)," and only use in RP with GrGp 2 or 3 with less than 5% Gleason pattern 5; and (2) minor TP5 is noted along with the GS, with the GrGp based on the GS. Global score and magnetic resonance imaging (MRI)-targeted biopsies are as follows: (1) when multiple undesignated cores are taken from a single MRI-targeted lesion, an overall grade for that lesion is given as if all the involved cores were one long core; and (2) if providing a global score, when different scores are found in the standard and the MRI-targeted biopsy, give a single global score (factoring both the systematic standard and the MRI-targeted positive cores). Grade Groups are as follows: (1) Grade Groups (GrGp) is the terminology adopted by major world organizations; and (2) retain GS 3 + 5 = 8 in GrGp 4. Cribriform carcinoma is as follows: (1) report the presence or absence of cribriform glands in biopsy and RP with Gleason pattern 4 carcinoma. Intraductal carcinoma (IDC-P) is as follows: (1) report IDC-P in biopsy and RP; (2) use criteria based on dense cribriform glands (>50% of the gland is composed of epithelium relative to luminal spaces) and/or solid nests and/or marked pleomorphism/necrosis; (3) it is not necessary to perform basal cell immunostains on biopsy and RP to identify IDC-P if the results would not change the overall (highest) GS/GrGp part per case; (4) do not include IDC-P in determining the final GS/GrGp on biopsy and/or RP; and (5) "atypical intraductal proliferation (AIP)" is preferred for an intraductal proliferation of prostatic secretory cells which shows a greater degree of architectural complexity and/or cytological atypia than typical high-grade prostatic intraepithelial neoplasia, yet falling short of the strict diagnostic threshold for IDC-P. Molecular testing is as follows: (1) Ki67 is not ready for routine clinical use; (2) additional studies of active surveillance cohorts are needed to establish the utility of PTEN in this setting; and (3) dedicated studies of RNA-based assays in active surveillance populations are needed to substantiate the utility of these expensive tests in this setting. Artificial intelligence and novel grading schema are as follows: (1) incorporating reactive stromal grade, percent GP4, minor tertiary GP5, and cribriform/intraductal carcinoma are not ready for adoption in current practice.

Practice patterns related to prostate cancer grading: results of a 2019 Genitourinary Pathology Society clinician survey

PURPOSE

To survey urologic clinicians regarding interpretation of and practice patterns in relation to emerging aspects of prostate cancer grading, including quantification of high-grade disease, cribriform/intraductal carcinoma, and impact of magnetic resonance imaging-targeted needle biopsy.

MATERIALS AND METHODS

The Genitourinary Pathology Society distributed a survey to urology and urologic oncology-focused societies and hospital departments. Eight hundred and thirty four responses were collected and analyzed using descriptive statistics.

RESULTS

Eighty percent of survey participants use quantity of Gleason pattern 4 on needle biopsy for clinical decisions, less frequently with higher Grade Groups. Fifty percent interpret "tertiary" grade as a minor/<5% component. Seventy percent of respondents would prefer per core grading as well as a global/overall score per set of biopsies, but 70% would consider highest Gleason score in any single core as the grade for management. Seventy five percent utilize Grade Group terminology in patient discussions. For 45%, cribriform pattern would affect management, while for 70% the presence of intraductal carcinoma would preclude active surveillance.

CONCLUSION

This survey of practice patterns in relationship to prostate cancer grading highlights similarities and differences between contemporary pathology reporting and its clinical application. As utilization of Gleason pattern 4 quantification, minor tertiary pattern, cribriform/intraductal carcinoma, and the incorporation of magnetic resonance imaging-based strategies evolve, these findings may serve as a basis for more nuanced communication and guide research efforts involving pathologists and clinicians.

Inhibition of the MYC-Regulated Glutaminase Metabolic Axis Is an Effective Synthetic Lethal Approach for Treating Chemoresistant Ovarian Cancers

Amplification and overexpression of the MYC oncogene in tumor cells, including ovarian cancer cells, correlates with poor responses to chemotherapy. As MYC is not directly targetable, we have analyzed molecular pathways downstream of MYC to identify potential therapeutic targets. Here we report that ovarian cancer cells overexpressing glutaminase (GLS), a target of MYC and a key enzyme in glutaminolysis, are intrinsically resistant to platinum-based chemotherapy and are enriched with intracellular antioxidant glutathione. Deprivation of glutamine by glutamine-withdrawal, GLS knockdown, or exposure to the GLS inhibitor CB-839 resulted in robust induction of reactive oxygen species in high GLS-expressing but not in low GLS-expressing ovarian cancer cells. Treatment with CB-839 rendered GLS^high cells vulnerable to the poly(ADP-ribose) polymerase (PARP) inhibitor, olaparib, and prolonged survival in tumor-bearing mice. These findings suggest consideration of applying a combined therapy of GLS inhibitor and PARP inhibitor to treat chemoresistant ovarian cancers, especially those with high GLS expression. SIGNIFICANCE: Targeting glutaminase disturbs redox homeostasis and nucleotide synthesis and causes replication stress in cancer cells, representing an exploitable vulnerability for the development of effective therapeutics. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/20/4514/F1.large.jpg.

Abstract A32: Characterizing patterns of cytokine coexpression with immune checkpoint markers in CD4 and CD8 tumor-infiltrating lymphocytes

In recent years, immunotherapy has become one of the most exciting and promising avenues to cancer treatment. Treatment with immune checkpoint inhibitors has managed to produce long-term remission of solid tumors in many patients. However, patients who respond well to such treatment are often a minority; this is particularly the case with some cancers such as renal cell carcinoma, non-small cell lung cancer, and glioblastoma, where many patients either derive no benefit or only a short-term benefit. In this analysis, we examined gene expression data from RNA sequencing experiments that compared tumor-infiltrating lymphocytes (TIL) with paired circulating lymphocytes from patients with renal cell carcinoma (RCC), bladder cancer (BLCA), prostate cancer (PRAD), and glioblastoma (GBM). Our analysis helped to characterize global CD4 and CD8 TIL gene expression patterns among these four cohorts. Further, using the expression profiles for known immune checkpoint markers PD-1, TIM-3, and LAG-3 in CD8 cells, we dichotomized the patient samples into potential checkpoint inhibitor responder and nonresponder groups. This model was then used to identify other genes that are associated with CD8 TIL exhaustion, which may lead to the identification of cytokines useful in discovering specific therapeutic targets.

Citation Format: Christopher M. Jackson, Wikum Dinalankara, John Choi, Thomas R. Nirschl, Christina M. Kochel, Ayush Pant, Denis Routkevitch, Laura Saleh, Christina Jackson, Alyza M. Skaist, Anuj Gupta, Linda A. Snyder, Edward M. Schaeffer, Ashley E. Ross, Ballentine Carter, Mohamad E. Allaf, Trinity J. Bivalacqua, Angelo M. DeMarzo, Jon D. Weingart, Chetan Bettegowda, Henry Brem, Drew M. Pardoll, Luigi Marchionni, Charles G. Drake, Michael Lim. Characterizing patterns of cytokine coexpression with immune checkpoint markers in CD4 and CD8 tumor-infiltrating lymphocytes [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr A32.

AXL Is a Putative Tumor Suppressor and Dormancy Regulator in Prostate Cancer

Prostate cancer bone metastasis remains lethal and incurable, and often arises years after elimination of the primary tumor. It is unclear what underlies the decades-long clinical latency before recurrence, but evidence points to the existence of dormant residual tumor cells that disseminated before the primary tumor was eliminated. To design therapies to prevent progression of disseminated tumor cells (DTC) into lethal metastases, it is crucial to understand the mechanism(s) underlying this dormancy. The current study functionally validated our previous observation that implicated the GAS6/AXL axis in mediating DTC dormancy in the bone marrow. AXL-null and AXL-overexpressing prostate cancer cell lines were generated to determine if AXL was necessary and/or sufficient for dormancy. Characterization of these cells in vitro and using in vivo mouse models of DTC growth demonstrated that AXL was indeed sufficient to induce dormancy, but was unable to maintain it long-term and was not absolutely required for a dormancy period. Clinically, AXL expression correlated with longer survival in prostate cancer patients, and AXL was not expressed by cancer cells in primary or metastatic tissue. These data point to a tumor-suppressive role for AXL in prostate cancer, and future work is required to determine if AXL is expressed on human bone marrow DTCs. IMPLICATIONS: The ability of AXL to initiate but not maintain dormancy, coupled with its dispensability, suggests that targeting AXL alone will not prevent lethal metastatic outgrowth, and likely a cooperative network of factors exists to mediate long-term cellular dormancy.

Abstract B026: Axl may support dormancy of disseminated tumor cells by inducing cell clustering and decreasing proliferation of metastatic prostate cancer cells

While the majority of prostate cancer (PCa) patients are cured by radical prostatectomy and/or radiation, 10-15% of these men eventually develop recurrent disease in the form of lethal metastases. The most common site for PCa metastasis is the bone marrow. The time from primary tumor removal to recurrence can range from 1-2 years to decades, and constitutes a period of minimal residual disease in which cancer cells remain in the body but are clinically undetectable. It is thought that these disseminated tumor cells (DTCs) are able to maintain a state of cellular dormancy in the bone marrow in which they are not proliferating or dying, and may be the seeds for lethal metastases. By understanding the mechanism(s) that regulate dormancy, we may be able to prevent metastasis altogether. Our group has previously found that the secreted bone marrow factor Gas6 and the expression of its receptor Axl are associated with dormant DTCs in xenograft mouse models. Thus, we hypothesize that Gas6 signaling through Axl mediates dormancy. In this study, we sought to functionally support this hypothesis both in vitro and in human PCa tissue. Overexpression of Axl in the C42B PCa cell line decreased proliferation in vitro, and this was independent of Gas6 when Axl was highly overexpressed. Axl overexpression also led to aggregation of C42B cells, suggestive of a possible role in circulating tumor cell (CTC) clustering to survive the circulation and inhabit the bone marrow. Furthermore, immunohistochemical staining of a PCa tissue microarray showed almost no Axl positivity in cancer cells, regardless of Gleason score and other clinical outcomes. Negative staining was also observed in sections from liver, lymph node, and tibial metastases. Consistent with this, Axl expression correlates with decreased incidence of biochemical recurrence and increased overall survival in the GRID and TCGA databases, respectively. These results indicate an antiproliferative role for Axl in PCa, and suggest its temporal expression during the natural history of PCa. Ongoing work includes assessing the expression of Axl on patient CTCs and DTCs, and using xenograft mouse models of metastasis to analyze the effects of Axl overexpression and knockout in PCa cell lines.

Citation Format: Haley D. Axelrod, Kenneth C. Valkenburg, Jessica L. Hicks, Angelo M. DeMarzo, Kenneth J. Pienta. Axl may support dormancy of disseminated tumor cells by inducing cell clustering and decreasing proliferation of metastatic prostate cancer cells [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr B026.

Abstract 53: Axl is sufficient but not necessary for disseminated prostate tumor cell dormancy

Prostate cancer (PCa) remains the second most common cancer among men in the U.S., and kills nearly 30,000 men each year. While the majority of patients with localized disease are cured by surgery and/or radiation, 10-15% of these patients will develop metastasis most commonly in the bone marrow. The time from primary tumor removal to recurrence can range from years to decades, and constitutes a period of minimal residual disease in which cancer cells remain in the body but are clinically undetectable. These disseminated tumor cells (DTCs) are seeds for lethal bone metastases and are thought to maintain a long-term state of dormancy in the bone marrow. Very little is known about the mechanism(s) by which dormancy is regulated, but further investigation may lead to therapeutic strategies aimed at preventing recurrent metastasis altogether. In this effort, we have previously found the secreted bone marrow factor Gas6 and the expression of its receptor Axl to be associated with dormant bone marrow DTCs in xenograft mouse models. We hypothesize that bone marrow Gas6 signals through Axl to induce dormancy in prostate DTCs, and explored the functional consequences of altering Axl expression in these models. To determine if Axl is sufficient to induce dormancy, we overexpressed it in the Axl-negative human PCa C42B cell line and monitored tumor growth by BLI after intracardiac injection in NSG mice. By the time half of the control overexpression injected mice developed tumors, less than 10% of mice injected with Axl overexpression cells developed tumor signal. This delay in tumorigenesis indicates a prolonged period of dormancy that is mediated by Axl expression. To determine if Axl is necessary for dormancy, we knocked out Axl in the Axl-positive human PCa PC3 cells using CRISPR and monitored growth after intracardiac injection in the same manner as the overexpression cells. Knockout of Axl did not increase the time to tumor signal compared to control cells. Loss of Axl also did not decrease the fraction of EdU negative, non-proliferative cells present in the bone marrow at one week post-injection. These data indicate that Axl is likely not necessary for DTC dormancy. Altogether this study suggests that Axl overexpression is sufficient to induce dormancy, but endogenous Axl is not required for dormancy. This is further supported by negative immunohistochemical staining of Axl on cancer cells within growing primary and metastatic tumors from a PCa tissue microarray. Axl also correlated with decreased incidence of biochemical recurrence (Decipher GRID) and increased overall survival (TCGA). Ongoing work includes assessing the expression of Axl on patient CTCs and DTCs, and correlating it with proliferation status.

Citation Format: Haley D. Axelrod, Kenneth C. Valkenburg, Jessica L. Hicks, Angelo M. DeMarzo, Kenneth J. Pienta. Axl is sufficient but not necessary for disseminated prostate tumor cell dormancy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 53.

Mutational profiles of breast cancer metastases from a rapid autopsy series reveal multiple evolutionary trajectories

Heterogeneity within and among tumors in a metastatic cancer patient is a well-established phenomenon that may confound treatment and accurate prognosis. Here, we used whole-exome sequencing to survey metastatic breast cancer tumors from 5 patients in a rapid autopsy program to construct the origin and genetic development of metastases. Metastases were obtained from 5 breast cancer patients using a rapid autopsy protocol and subjected to whole-exome sequencing. Metastases were evaluated for sharing of somatic mutations, correlation of copy number variation and loss of heterozygosity, and genetic similarity scores. Pathological features of the patients' disease were assessed by immunohistochemical analyses. Our data support a monoclonal origin of metastasis in 3 cases, but in 2 cases, metastases arose from at least 2 distinct subclones in the primary tumor. In the latter 2 cases, the primary tumor presented with mixed histologic and pathologic features, suggesting early divergent evolution within the primary tumor with maintenance of metastatic capability in multiple lineages. We used genetic and histopathological evidence to demonstrate that metastases can be derived from a single or multiple independent clones within a primary tumor. This underscores the complexity of breast cancer clonal evolution and has implications for how best to determine and implement therapies for early- and late-stage disease.

MYC Targeted Long Noncoding RNA DANCR Promotes Cancer in Part by Reducing p21 Levels

The MYC oncogene broadly promotes transcription mediated by all nuclear RNA polymerases, thereby acting as a positive modifier of global gene expression. Here, we report that MYC stimulates the transcription of DANCR, a long noncoding RNA (lncRNA) that is widely overexpressed in human cancer. We identified DANCR through its overexpression in a transgenic model of MYC-induced lymphoma, but found that it was broadly upregulated in many human cancer cell lines and cancers, including most notably in prostate and ovarian cancers. Mechanistic investigations indicated that DANCR limited the expression of cell-cycle inhibitor p21 (CDKN1A) and that the inhibitory effects of DANCR loss on cell proliferation could be partially rescued by p21 silencing. In a xenograft model of human ovarian cancer, a nanoparticle-mediated siRNA strategy to target DANCR in vivo was sufficient to strongly inhibit tumor growth. Our observations expand knowledge of how MYC drives cancer cell proliferation by identifying DANCR as a critical lncRNA widely overexpressed in human cancers.Significance: These findings expand knowledge of how MYC drives cancer cell proliferation by identifying an oncogenic long noncoding RNA that is widely overexpressed in human cancers. Cancer Res; 78(1); 64-74. ©2017 AACR.

Pharmacodynamic and pharmacokinetic neoadjuvant study of hedgehog pathway inhibitor Sonidegib (LDE-225) in men with high-risk localized prostate cancer undergoing prostatectomy

Purpose

To determine the pharmacodynamic effects of Sonidegib (LDE-225) in prostate tumor tissue from men with high-risk localized prostate cancer, by comparing pre-surgical core-biopsy specimens to tumor tissue harvested post-treatment at prostatectomy.

Methods

We conducted a prospective randomized (Sonidegib vs. observation) open-label translational clinical trial in men with high-risk localized prostate cancer undergoing radical prostatectomy. The primary endpoint was the proportion of patients in each arm who achieved at least a two-fold reduction in GLI1 mRNA expression in post-treatment versus pre-treatment tumor tissue. Secondary endpoints included the effect of pre-surgical treatment with Sonidegib on disease progression following radical prostatectomy, and safety.

Results

Fourteen men were equally randomized (7 per arm) to either neoadjuvant Sonidegib or observation for 4 weeks prior to prostatectomy. Six of seven men (86%) in the Sonidegib arm (and none in the control group) achieved a GLI1 suppression of at least two-fold. In the Sonidegib arm, drug was detectable in plasma and in prostatic tissue; and median intra-patient GLI1 expression decreased by 63-fold, indicating potent suppression of Hedgehog signaling. Sonidegib was well tolerated, without any Grade 3-4 adverse events observed. Disease-free survival was comparable among the two arms (HR = 1.50, 95% CI 0.26-8.69, P = 0.65).

Conclusions

Hedgehog pathway activity (as measured by GLI1 expression) was detectable at baseline in men with localized high-risk prostate cancer. Sonidegib penetrated into prostatic tissue and induced a >60-fold suppression of the Hedgehog pathway. The oncological benefit of Hedgehog pathway inhibition in prostate cancer remains unclear.

c-Myc Antagonises the Transcriptional Activity of the Androgen Receptor in Prostate Cancer Affecting Key Gene Networks

Prostate cancer (PCa) is the most common non-cutaneous cancer in men. The androgen receptor (AR), a ligand-activated transcription factor, constitutes the main drug target for advanced cases of the disease. However, a variety of other transcription factors and signaling networks have been shown to be altered in patients and to influence AR activity. Amongst these, the oncogenic transcription factor c-Myc has been studied extensively in multiple malignancies and elevated protein levels of c-Myc are commonly observed in PCa. Its impact on AR activity, however, remains elusive. In this study, we assessed the impact of c-Myc overexpression on AR activity and transcriptional output in a PCa cell line model and validated the antagonistic effect of c-MYC on AR-targets in patient samples. We found that c-Myc overexpression partially reprogrammed AR chromatin occupancy and was associated with altered histone marks distribution, most notably H3K4me1 and H3K27me3. We found c-Myc and the AR co-occupy a substantial number of binding sites and these exhibited enhancer-like characteristics. Interestingly, c-Myc overexpression antagonised clinically relevant AR target genes. Therefore, as an example, we validated the antagonistic relationship between c-Myc and two AR target genes, KLK3 (alias PSA, prostate specific antigen), and Glycine N-Methyltransferase (GNMT), in patient samples. Our findings provide unbiased evidence that MYC overexpression deregulates the AR transcriptional program, which is thought to be a driving force in PCa.

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c-MYC and AR share one third of chromatin binding with enhancer-like features.

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c-MYC can repress the expression of a subset prostate cancer biomarkers, including PSA.

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c-MYC and AR antagonize the expression of, Glycine N-Methyltransferase (GNMT), responsible for sarcosine biosynthesis.

Prostate cancer is a heterogeneous disease. The most frequently used biomarker in clinical setting, a well described androgen receptor target gene, PSA, still performs poorly in stratifying patients at real risk of death due to the disease. Despite this, therapeutic approaches focus on suppressing androgen receptor signaling. However, this is only one of the recurrent alterations found in patients. This study focuses on c-MYC and the effects of its deregulation in advanced prostate cancer. We find that there is an inverse relationship between established biomarkers expression, including PSA. This inverse relationship could be used in clinics to select beneficial therapeutic approaches for a subset of prostate cancer cases.

Characterization of 1577 primary prostate cancers reveals novel biological and clinicopathologic insights into molecular subtypes

BACKGROUND

Prostate cancer (PCa) molecular subtypes have been defined by essentially mutually exclusive events, including ETS gene fusions (most commonly involving ERG) and SPINK1 overexpression. Clinical assessment may aid in disease stratification, complementing available prognostic tests.

OBJECTIVE

To determine the analytical validity and clinicopatholgic associations of microarray-based molecular subtyping.

DESIGN, SETTING, AND PARTICIPANTS

We analyzed Affymetrix GeneChip expression profiles for 1577 patients from eight radical prostatectomy cohorts, including 1351 cases assessed using the Decipher prognostic assay (GenomeDx Biosciences, San Diego, CA, USA) performed in a laboratory with Clinical Laboratory Improvements Amendment certification. A microarray-based (m-) random forest ERG classification model was trained and validated. Outlier expression analysis was used to predict other mutually exclusive non-ERG ETS gene rearrangements (ETS(+)) or SPINK1 overexpression (SPINK1(+)).

OUTCOME MEASUREMENTS

Associations with clinical features and outcomes by multivariate logistic regression analysis and receiver operating curves.

RESULTS AND LIMITATIONS

The m-ERG classifier showed 95% accuracy in an independent validation subset (155 samples). Across cohorts, 45% of PCas were classified as m-ERG(+), 9% as m-ETS(+), 8% as m-SPINK1(+), and 38% as triple negative (m-ERG(-)/m-ETS(-)/m-SPINK1(-)). Gene expression profiling supports three underlying molecularly defined groups: m-ERG(+), m-ETS(+), and m-SPINK1(+)/triple negative. On multivariate analysis, m-ERG(+) tumors were associated with lower preoperative serum prostate-specific antigen and Gleason scores, but greater extraprostatic extension (p<0.001). m-ETS(+) tumors were associated with seminal vesicle invasion (p=0.01), while m-SPINK1(+)/triple negative tumors had higher Gleason scores and were more frequent in Black/African American patients (p<0.001). Clinical outcomes were not significantly different among subtypes.

CONCLUSIONS

A clinically available prognostic test (Decipher) can also assess PCa molecular subtypes, obviating the need for additional testing. Clinicopathologic differences were found among subtypes based on global expression patterns.

PATIENT SUMMARY

Molecular subtyping of prostate cancer can be achieved using extra data generated from a clinical-grade, genome-wide expression-profiling prognostic assay (Decipher). Transcriptomic and clinical analysis support three distinct molecular subtypes: (1) m-ERG(+), (2) m-ETS(+), and (3) m-SPINK1(+)/triple negative (m-ERG(-)/m-ETS(-)/m-SPINK1(-)). Incorporation of subtyping into a clinically available assay may facilitate additional applications beyond routine prognosis.

Paucity of PD-L1 expression in prostate cancer: innate and adaptive immune resistance

BACKGROUND

Primary prostate cancers are infiltrated with programmed death-1 (PD-1) expressing CD8+ T-cells. However, in early clinical trials, men with metastatic castrate-resistant prostate cancer did not respond to PD-1 blockade as a monotherapy. One explanation for this unresponsiveness could be that prostate tumors generally do not express programmed death ligand-1 (PD-L1), the primary ligand for PD-1. However, lack of PD-L1 expression in prostate cancer would be surprising, given that phosphatase and tensin homolog (PTEN) loss is relatively common in prostate cancer and several studies have shown that PTEN loss correlates with PD-L1 upregulation--constituting a mechanism of innate immune resistance. This study tested whether prostate cancer cells were capable of expressing PD-L1, and whether the rare PD-L1 expression that occurs in human specimens correlates with PTEN loss.

METHODS

Human prostate cancer cell lines were evaluated for PD-L1 expression and loss of PTEN by flow cytometry and western blotting, respectively. Immunohistochemical (IHC) staining for PTEN was correlated with PD-L1 IHC using a series of resected human prostate cancer samples.

RESULTS

In vitro, many prostate cancer cell lines upregulated PD-L1 expression in response to inflammatory cytokines, consistent with adaptive immune resistance. In these cell lines, no association between PTEN loss and PD-L1 expression was apparent. In primary prostate tumors, PD-L1 expression was rare, and was not associated with PTEN loss.

CONCLUSIONS

These studies show that some prostate cancer cell lines are capable of expressing PD-L1. However, in human prostate cancer, PTEN loss is not associated with PD-L1 expression, arguing against innate immune resistance as a mechanism that mitigates antitumor immune responses in this disease.

Abstract 2342: Characterization of inflammatory markers and mast cells in association with prostate cancer

Evidence suggests that there is a strong association between chronic inflammation and prostate cancer development and/or progression. While chronic inflammation is known to serve as an “enabling characteristic” in many cancers, the mechanism whereby it contributes to carcinogenesis and progression is still very controversial. This is particularly true for cells of the innate immune system, such as mast cells, that have been shown to possess both pro- and anti-tumor properties. The role of mast cells in prostate cancer is of particular interest, as evidence suggests that they influence cancer progression and immune modulation. The current study seeks to characterize mast cell density and mast cell-to-epithelial ratio in relation to prostate cancer recurrence using a unique set of tissue microarrays (TMAs) from a case-control study nested in a cohort of prostate cancer patients who underwent radical prostatectomy. These studies are aided by novel digital image analysis using a software framework integrating whole slide imaging, virtual microscopy, and ImageJ based analysis algorithms. Our preliminary results, obtained via analysis of a prostate cancer TMA containing matched cancer and benign tissues from 727 cases of radical prostatectomy patients, correlated with the literature in that the mast cell density (mast cell number/total tissue area) was significantly higher in cancer versus benign (p = 0.0016). We will expanded this study to determine if mast cell number correlates with epithelial area in the same cohort and to examine mast cell density in correlation to the presence, grade, or progression of prostate cancer. Furthermore, we will be examining this in a large full tissue slide cohort in relation to Gleason grade and stage. Finally, we are expanding this study to explore a possible role for mast cells in the racial disparity in prostate cancer incidence and prognosis.

Citation Format: Heidi Hempel, Ibrahim Kulac, Nathan S. Cuka, Toby C. Cornish, Elizabeth A. Platz, Angelo M. DeMarzo, Karen S. Sfanos. Characterization of inflammatory markers and mast cells in association with prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2342. doi:10.1158/1538-7445.AM2015-2342

USP22 regulates oncogenic signaling pathways to drive lethal cancer progression

Increasing evidence links deregulation of the ubiquitin-specific proteases 22 (USP22) deubitiquitylase to cancer development and progression in a select group of tumor types, but its specificity and underlying mechanisms of action are not well defined. Here we show that USP22 is a critical promoter of lethal tumor phenotypes that acts by modulating nuclear receptor and oncogenic signaling. In multiple xenograft models of human cancer, modeling of tumor-associated USP22 deregulation demonstrated that USP22 controls androgen receptor accumulation and signaling, and that it enhances expression of critical target genes coregulated by androgen receptor and MYC. USP22 not only reprogrammed androgen receptor function, but was sufficient to induce the transition to therapeutic resistance. Notably, in vivo depletion experiments revealed that USP22 is critical to maintain phenotypes associated with end-stage disease. This was a significant finding given clinical evidence that USP22 is highly deregulated in tumors, which have achieved therapeutic resistance. Taken together, our findings define USP22 as a critical effector of tumor progression, which drives lethal phenotypes, rationalizing this enzyme as an appealing therapeutic target to treat advanced disease.

Engineering a prostate-specific membrane antigen-activated tumor endothelial cell prodrug for cancer therapy

Heterogeneous expression of drug target proteins within tumor sites is a major mechanism of resistance to anticancer therapies. We describe a strategy to selectively inhibit, within tumor sites, the function of a critical intracellular protein, the sarcoplasmic/endoplasmic reticulum calcium adenosine triphosphatase (SERCA) pump, whose proper function is required by all cell types for viability. To achieve targeted inhibition, we took advantage of the unique expression of the carboxypeptidase prostate-specific membrane antigen (PSMA) by tumor endothelial cells within the microenvironment of solid tumors. We generated a prodrug, G202, consisting of a PSMA-specific peptide coupled to an analog of the potent SERCA pump inhibitor thapsigargin. G202 produced substantial tumor regression against a panel of human cancer xenografts in vivo at doses that were minimally toxic to the host. On the basis of these data, a phase 1 dose-escalation clinical trial has been initiated with G202 in patients with advanced cancer.

Expression status and prognostic significance of mammalian target of rapamycin pathway members in urothelial carcinoma of urinary bladder after cystectomy

BACKGROUND

Bladder urothelial carcinoma has high rates of mortality and morbidity. Identifying novel molecular prognostic factors and targets of therapy is crucial. Mammalian target of rapamycin (mTOR) pathway plays a pivotal role in establishing cell shape, migration, and proliferation.

METHODS

Tissue microarrays were constructed from 132 cystectomies (1994-2002). Immunohistochemistry was performed for Pten, c-myc, p27, phosphorylated (phos)Akt, phosS6, and 4E-BP1. Markers were evaluated for pattern, percentage, and intensity of staining.

RESULTS

Mean length of follow-up was 62.6 months (range, 1-182 months). Disease progression, overall survival (OS), and disease-specific survival (DSS) rates were 42%, 60%, and 68%, respectively. Pten showed loss of expression in 35% of bladder urothelial carcinoma. All markers showed lower expression in invasive bladder urothelial carcinoma compared with benign urothelium with the exception of 4E-BP1. Pten, p27, phosAkt, phosS6, and 4E-BP1 expression correlated with pathologic stage (pathological stage; P<.03). Pten, 4E-BP1, and phosAkt expression correlated with divergent aggressive histology and invasion. phosS6 expression inversely predicted OS (P=.01), DSS (P=.001), and progression (P=.05). c-myc expression inversely predicted progression (P=.01). In a multivariate analysis model that included TNM stage grouping, divergent aggressive histology, concomitant carcinoma in situ, phosS6, and c-myc expression, phosS6 was an independent predictor of DSS (P=.03; hazard ratio [HR], -0.19), whereas c-myc was an independent predictor of progression (P=.02; HR, -0.38). In a second model substituting organ-confined disease and lymph node status for TNM stage grouping, phosS6 and c-myc remained independent predictors of DSS (P=.03; HR, -0.21) and progression (P=.03; HR, -0.34), respectively.

CONCLUSIONS

We found an overall down-regulation of mTOR pathway in bladder urothelial carcinoma. phosS6 independently predicted DSS, and c-myc independently predicted progression.

Cell-autonomous intracellular androgen receptor signaling drives the growth of human prostate cancer initiating cells

BACKGROUND

The lethality of prostate cancer is due to the continuous growth of cancer initiating cells (CICs) which are often stimulated by androgen receptor (AR) signaling. However, the underlying molecular mechanism(s) for such AR-mediated growth stimulation are not fully understood. Such mechanisms may involve cancer cell-dependent induction of tumor stromal cells to produce paracrine growth factors or could involve cancer cell autonomous autocrine and/or intracellular AR signaling pathways.

METHODS

We utilized clinical samples, animal models and a series of AR-positive human prostate cancer cell lines to evaluate AR-mediated growth stimulation of prostate CICs.

RESULTS

The present studies document that stromal AR expression is not required for prostate cancer growth, since tumor stroma surrounding AR-positive human prostate cancer metastases (N = 127) are characteristically AR-negative. This lack of a requirement for AR expression in tumor stromal cells is also documented by the fact that human AR-positive prostate cancer cells grow equally well when xenografted in wild-type versus AR-null nude mice. AR-dependent growth stimulation was documented to involve secretion, extracellular binding, and signaling by autocrine growth factors. Orthotopic xenograft animal studies documented that the cellautonomous autocrine growth factors which stimulate prostate CIC growth are not the andromedins secreted by normal prostate stromal cells. Such cell autonomous and extracellular autocrine signaling is necessary but not sufficient for the optimal growth of prostate CICs based upon the response to anti-androgen plus/or minus preconditioned media.

CONCLUSIONS

AR-induced growth stimulation of human prostate CICs requires AR-dependent intracellular pathways. The identification of such AR-dependent intracellular pathways offers new leads for the development of effective therapies for prostate cancer.

Individual and cumulative effect of prostate cancer risk-associated variants on clinicopathologic variables in 5,895 prostate cancer patients

BACKGROUND

More than a dozen single nucleotide polymorphisms (SNPs) have been associated with prostate cancer (PCa) risk from genome-wide association studies (GWAS). Their association with PCa aggressiveness and clinicopathologic variables is inconclusive.

METHODS

Twenty PCa risk SNPs implicated in GWAS and fine mapping studies were evaluated in 5,895 PCa cases treated by radical prostatectomy at Johns Hopkins Hospital, where each tumor was uniformly graded and staged using the same protocol.

RESULTS

For 18 of the 20 SNPs examined, no statistically significant differences (P > 0.05) were observed in risk allele frequencies between patients with more aggressive (Gleason scores > or =4 + 3, or stage > or =T3b, or N+) or less aggressive disease (Gleason scores < or =3 + 4, and stage < or =T2, and N0). For the two SNPs that had significant differences between more and less aggressive disease rs2735839 in KLK3 (P = 8.4 x 10(-7)) and rs10993994 in MSMB (P = 0.046), the alleles that are associated with increased risk for PCa were more frequent in patients with less aggressive disease. Since these SNPs are known to be associated with PSA levels in men without PCa diagnoses, these latter associations may reflect the enrichment of low grade, low stage cases diagnosed by contemporary disease screening with PSA.

CONCLUSIONS

The vast majority of PCa risk-associated SNPs are not associated with aggressiveness and clinicopathologic variables of PCa. Correspondingly, they have minimal utility in predicting the risk for developing more or less aggressive forms of PCa.

TMPRSS2-ERG gene fusions are infrequent in prostatic ductal adenocarcinomas

Ductal adenocarcinoma of the prostate is an unusual subtype that may be associated with a more aggressive clinical course, and is less responsive to conventional therapies than the more common prostatic acinar adenocarcinoma. However, given its frequent association with an acinar component at prostatectomy, some have challenged the concept of prostatic ductal adenocarcinoma as a distinct clinicopathologic entity. We studied the occurrence of the TMPRSS2-ERG gene fusion, in 40 surgically resected ductal adenocarcinoma cases, and in their associated acinar component using fluorescence in situ hybridization. A group of 38 'pure' acinar adenocarcinoma cases matched with the ductal adenocarcinoma group for pathological grade and stage was studied as a control. Compared with the matched acinar adenocarcinoma cases, the TMPRSS2-ERG gene fusion was significantly less frequently observed in ductal adenocarcinoma (45 vs 11% of cases, P=0.002, Fisher's exact test). Here, of the ductal adenocarcinoma cases with the gene fusion, 75% were fused through deletion, and the remaining case was fused through translocation. The TMPRSS2-ERG gene fusion was also rare in the acinar component of mixed ductal-acinar tumors when compared with the pure acinar adenocarcinoma controls (5 vs 45%, P=0.001, Fisher's exact test). In 95% of the ductal adenocarcinoma cases in which a concurrent acinar component was analyzed, there was concordance for presence/absence of the TMPRSS2-ERG gene fusion between the different histologic subtypes. In the control group of pure acinar adenocarcinoma cases, 59% were fused through deletion and 41% were fused through translocation. The presence of the TMPRSS2-ERG gene fusion in some cases of prostatic ductal adenocarcinoma supports the concept that ductal adenocarcinoma and acinar adenocarcinoma may be related genetically. However, the significantly lower rate of the gene fusion in pure ductal adenocarcinoma cases underscores the fact that genetic and biologic differences exist between these two tumors that may be important for future therapeutic strategies.

The role of CD133 in normal human prostate stem cells and malignant cancer-initiating cells

Resolving the specific cell of origin for prostate cancer is critical to define rational targets for therapeutic intervention and requires the isolation and characterization of both normal human prostate stem cells and prostate cancer-initiating cells (CIC). Single epithelial cells from fresh normal human prostate tissue and prostate epithelial cell (PrEC) cultures derived from them were evaluated for the presence of subpopulations expressing stem cell markers and exhibiting stem-like growth characteristics. When epithelial cell suspensions containing cells expressing the stem cell marker CD133+ are inoculated in vivo, regeneration of stratified human prostate glands requires inductive prostate stromal cells. PrEC cultures contain a small subpopulation of CD133+ cells, and fluorescence-activated cell sorting-purified CD133+ PrECs self-renew and regenerate cell populations expressing markers of transit-amplifying cells (DeltaNp63), intermediate cells (prostate stem cell antigen), and neuroendocrine cells (CD56). Using a series of CD133 monoclonal antibodies, attachment and growth of CD133+ PrECs requires surface expression of full-length glycosylated CD133 protein. Within a series of androgen receptor-positive (AR+) human prostate cancer cell lines, CD133+ cells are present at a low frequency, self-renew, express AR, generate phenotypically heterogeneous progeny negative for CD133, and possess an unlimited proliferative capacity, consistent with CD133+ cells being CICs. Unlike normal adult prostate stem cells, prostate CICs are AR+ and do not require functional CD133. This suggests that (a) AR-expressing prostate CICs are derived from a malignantly transformed intermediate cell that acquires "stem-like activity" and not from a malignantly transformed normal stem cell and (b) AR signaling pathways are a therapeutic target for prostate CICs.

Phenotypic analysis of prostate-infiltrating lymphocytes reveals TH17 and Treg skewing

PURPOSE

Pathologic examination of prostate glands removed from patients with prostate cancer commonly reveals infiltrating CD4+ and CD8+ T cells. Little is known about the phenotype of these cells, despite accumulating evidence suggesting a potential role for chronic inflammation in the etiology of prostate cancer.

EXPERIMENTAL DESIGN

We developed a technique that samples the majority of the peripheral prostate through serial needle aspirates. CD4+ prostate-infiltrating lymphocytes (PIL) were isolated using magnetic beads and analyzed for subset skewing using both flow cytometry and quantitative reverse transcription-PCR. The transcriptional profile of fluorescence-activated cell sorted prostate-infiltrating regulatory T cells (CD4+, CD25+, GITR+) was compared with naïve, peripheral blood T cells using microarray analysis.

RESULTS

CD4+ PIL showed a paucity of TH2 (interleukin-4-secreting) cells, a surprising finding given the generally accepted association of these cells with chronic, smoldering inflammation. Instead, CD4+ PIL seemed to be skewed towards a regulatory Treg phenotype (FoxP3+) as well as towards the TH17 phenotype (interleukin-17+). We also found that a preponderance of TH17-mediated inflammation was associated with a lower pathologic Gleason score. These protein level data were reflected at the message level, as analyzed by quantitative reverse transcription-PCR. Microarray analysis of pooled prostate-infiltrating T(reg) revealed expected Treg-associated transcripts (FoxP3, CTLA-4, GITR, LAG-3) as well as a number of unique cell surface markers that may serve as additional Treg markers.

CONCLUSION

Taken together, these data suggest that TH17 and/or Treg CD4+ T cells (rather than TH2 T cells) may be involved in the development or progression of prostate cancer.

Effect of DNA methylation on identification of aggressive prostate cancer

OBJECTIVES

Biochemical (prostate-specific antigen) recurrence of prostate cancer after radical prostatectomy remains a major problem. Better biomarkers are needed to identify high-risk patients. DNA methylation of promoter regions leads to gene silencing in many cancers. In this study, we assessed the effect of DNA methylation on the identification of recurrent prostate cancer.

METHODS

We studied the methylation status of 15 pre-specified genes using methylation-specific polymerase chain reaction on tissue samples from 151 patients with localized prostate cancer and at least 5 years of follow-up after prostatectomy.

RESULTS

On multivariate logistic regression analysis, a high Gleason score and involvement of the capsule, lymph nodes, seminal vesicles, or surgical margin were associated with an increased risk of biochemical recurrence. Methylation of CDH13 by itself (odds ratio 5.50, 95% confidence interval [CI] 1.34 to 22.67; P = 0.02) or combined with methylation of ASC (odds ratio 5.64, 95% CI 1.47 to 21.7; P = 0.01) was also associated with an increased risk of biochemical recurrence. The presence of methylation of ASC and/or CDH13 yielded a sensitivity of 72.3% (95% CI 57% to 84.4%) and negative predictive value of 79% (95% CI 66.8% to 88.3%), similar to the weighted risk of recurrence (determined from the lymph node status, seminal vesicle status, surgical margin status, and postoperative Gleason score), a powerful clinicopathologic prognostic score. However, 34% (95% CI 21% to 49%) of the patients with recurrence were identified by the methylation profile of ASC and CDH13 rather than the weighted risk of recurrence.

CONCLUSIONS

The results of our study have shown that methylation of CDH13 alone or combined with methylation of ASC is independently associated with an increased risk of biochemical recurrence after radical prostatectomy even considering the weighted risk of recurrence score. These findings should be validated in an independent, larger cohort of patients with prostate cancer who have undergone radical prostatectomy.

Immunohistochemical differentiation of high-grade prostate carcinoma from urothelial carcinoma

The histologic distinction between high-grade prostate cancer and infiltrating high-grade urothelial cancer may be difficult, and has significant implications because each disease may be treated very differently (ie, hormone therapy for prostate cancer and chemotherapy for urothelial cancer). Immunohistochemistry of novel and established prostatic and urothelial markers using tissue microarrays (TMAs) were studied. Prostatic markers studied included: prostate-specific antigen (PSA), prostein (P501s), prostate-specific membrane antigen (PSMA), NKX3.1 (an androgen-related tumor suppressor gene), and proPSA (pPSA) (precursor form of PSA). "Urothelial markers" included high molecular weight cytokeratin (HMWCK), p63, thrombomodulin, and S100P (placental S100). TMAs contained 38 poorly differentiated prostate cancers [Gleason score 8 (n=2), Gleason score 9 (n=18), Gleason score 10 (n=18)] and 35 high-grade invasive urothelial carcinomas from radical prostatectomy and cystectomy specimens, respectively. Each case had 2 to 8 tissue spots (0.6-mm diameter). If all spots for a case showed negative staining, the case was called negative. The sensitivities for labeling prostate cancers were PSA (97.4%), P501S (100%), PSMA (92.1%), NKX3.1 (94.7%), and pPSA (94.7%). Because of PSA's high sensitivity on the TMA, we chose 41 additional poorly differentiated primary (N=36) and metastatic (N=5) prostate carcinomas which showed variable PSA staining at the time of diagnosis and performed immunohistochemistry on routine tissue sections. Compared to PSA, which on average showed 18.8% of cells with moderate to strong positivity, cases stained for P501S, PSMA, and NKX3.1 had on average 42.5%, 53.7%, 52.9% immunoreactivity, respectively. All prostatic markers showed excellent specificity. HMWCK, p63, thrombomodulin, and S100P showed lower sensitivities in labeling high-grade invasive urothelial cancer in the TMAs with 91.4%, 82.9%, 68.6%, and 71.4% staining, respectively. These urothelial markers were relatively specific with only a few prostate cancers showing scattered (<or=2%) weak-moderate positive cells. In summary, PSA can be used as the first screening marker for differentiating high-grade prostate adenocarcinoma from high-grade urothelial carcinoma. Immunohistochemistry for P501S, PSMA, NKX3.1, and pPSA are useful when high-grade prostate cancer is suspected based on the morphology or clinical findings, yet shows negative or equivocal PSA staining. HMWCK and p63 are superior to the novel markers thrombomodulin and S100P.

The N-Myc down regulated Gene1 (NDRG1) Is a Rab4a effector involved in vesicular recycling of E-cadherin

Cell to cell adhesion is mediated by adhesion molecules present on the cell surface. Downregulation of molecules that form the adhesion complex is a characteristic of metastatic cancer cells. Downregulation of the N-myc down regulated gene1 (NDRG1) increases prostate and breast metastasis. The exact function of NDRG1 is not known. Here by using live cell confocal microscopy and in vitro reconstitution, we report that NDRG1 is involved in recycling the adhesion molecule E-cadherin thereby stabilizing it. Evidence is provided that NDRG1 recruits on recycling endosomes in the Trans Golgi network by binding to phosphotidylinositol 4-phosphate and interacts with membrane bound Rab4aGTPase. NDRG1 specifically interacts with constitutively active Rab4aQ67L mutant protein and not with GDP-bound Rab4aS22N mutant proving NDRG1 as a novel Rab4a effector. Transferrin recycling experiments reveals NDRG1 colocalizes with transferrin during the recycling phase. NDRG1 alters the kinetics of transferrin recycling in cells. NDRG1 knockdown cells show a delay in recycling transferrin, conversely NDRG1 overexpressing cells reveal an increase in rate of transferrin recycling. This novel finding of NDRG1 as a recycling protein involved with recycling of E-cadherin will aid in understanding NDRG1 role as a metastasis suppressor protein.

Early Prostate Cancer Antigen Expression in Predicting Presence of Prostate Cancer in Men With Histologically Negative Biopsies

PURPOSE

Early prostate cancer antigen is a nuclear matrix protein that was recently shown to be expressed in prostate adenocarcinoma and adjacent benign tissue. Previous studies have demonstrated early prostate cancer antigen expression in benign prostate tissue up to 5 years before a diagnosis of prostate carcinoma, suggesting that early prostate cancer antigen could be used as a potential predictive marker.

MATERIALS AND METHODS

We evaluated early prostate cancer antigen expression by immunohistochemistry using a polyclonal antibody (Onconome Inc., Seattle, Washington) on benign biopsies from 98 patients. Biopsies were obtained from 4 groups that included 39 patients with first time negative biopsy (group 1), 24 patients with persistently negative biopsies (group 2), 8 patients with initially negative biopsies who were subsequently diagnosed with prostate carcinoma (group 3) and negative biopsies obtained from 27 cases where other concurrent biopsies contained prostate carcinoma (group 4). Early prostate cancer antigen staining was assessed by 2 of the authors who were blind to the group of the examined sections. Staining intensity (range 0 to 3) and extent (range 1 to 3) scores were assigned. The presence of intensity 3 staining in any of the blocks of a biopsy specimen was considered as positive for early prostate cancer antigen for the primary outcome in the statistical analysis. In addition, as secondary outcomes we evaluated the data using the proportion of blocks with intensity 3 early prostate cancer antigen staining, the mean of the product of staining intensity and staining extent of all blocks within a biopsy, and the mean of the product of intensity 3 staining and extent.

RESULTS

Primary outcome analysis revealed the proportion of early prostate cancer antigen positivity to be highest in group 3 (6 of 8, 75%) and lowest in group 2 (7 of 24, 29%, p=0.04 for differences among groups). A relatively higher than expected proportion of early prostate cancer antigen positivity was present in group 1 (23 of 39, 59%). Early prostate cancer antigen was negative in 41% of group 4 who were known to harbor prostate carcinoma. The proportion of early prostate cancer antigen positivity was statistically significantly lower in group 2 than in each of the other groups when compared pairwise. A lower proportion of early prostate cancer antigen positivity was encountered in older archival tissue blocks (p<0.0001) pointing to a potential confounding factor. Corrected for block age, group 3 was the only group to remain statistically significantly different in early prostate cancer antigen positivity compared to the reference group 2. Similar findings were obtained when adjustments for patient age were made and when analysis was based on secondary outcome measurements.

CONCLUSIONS

Our study showed a higher proportion of early prostate cancer antigen expression in initial negative prostate biopsy of patients who were diagnosed with prostate carcinoma on subsequent followup biopsies. We found a relatively high proportion of early prostate cancer antigen positivity (59%) in the group with first time negative biopsies and a potential 41% rate of false-negative early prostate cancer antigen staining in benign biopsies from cases with documented prostate carcinoma on concurrent cores. The lower early prostate cancer antigen positivity in cases with older blocks raises the question of a confounding effect of block age. Additional studies on the antigenic properties of early prostate cancer antigen in archival material are required to further delineate the usefulness of early prostate cancer antigen immunostaining on biopsy material.

Expanding the histologic spectrum of mucinous tubular and spindle cell carcinoma of the kidney

Mucinous tubular and spindle cell carcinomas (MTSCs) are polymorphic neoplasms characterized by small, elongated tubules lined by cuboidal cells and/or cords of spindled cells separated by pale mucinous stroma. Nonclassic morphologic variants and features of MTSC have not been well studied. We identified 17 previously unreported MTSCs from Surgical Pathology and consultative files of the authors and their respective institutions and studied their morphologic features. A total of 10/17 cases were considered "classic," as described above, with 5/10 showing at least focal (20% to 50%) tubular predominance without apparent mucinous matrix. Alcian blue staining revealed abundant (>50%) mucin in all classic cases. Seven of 17 MTSCs were classified as "mucin-poor," with little to no extracellular mucin appreciable by hematoxylin and eosin. Four of these cases showed equal tubular and spindled morphology, 2 cases showed spindle cell predominance (70%; 95%), and 1 case showed tubular predominance (90%). In 5/7 mucin-poor cases, staining for Alcian blue revealed scant (<10%) mucin in cellular areas with the other 2 cases having 30% mucin. Unusual histologic features identified in the 17 cases were: foamy macrophages (n=8), papillations/well formed papillae (n=6/n=1), focal clear cells in tubules (n=3), necrosis (n=3), oncocytic tubules (n=2; 40%, 5%), numerous small vacuoles (n=2), heterotopic bone (n=1), psammomatous calcification (n=1), and nodular growth with lymphocytic cuffing (n=1). An exceptional case contained a well-circumscribed, HMB45-positive angiomyolipoma within the MTSC. MTSCs may be "mucin-poor" and show a marked predominance of either of its principal morphologic components, which coupled with the presence of other unusual features such as clear cells, papillations, foamy macrophages, and necrosis, may mimic other forms of renal cell carcinoma. Pathologists must be aware of the spectrum of histologic findings within MTSCs to ensure their accurate diagnosis.

Epithelial architectural destruction is necessary for bone marrow derived cell contribution to regenerating prostate epithelium

PURPOSE

Using various nonphysiological tissue injury/repair models numerous studies have demonstrated the capacity of bone marrow derived cells to contribute to the repopulation of epithelial tissues following damage. To investigate whether this phenomenon might also occur during periods of physiological tissue degeneration/regeneration we compared the ability of bone marrow derived cells to rejuvenate the prostate gland in mice that were castrated and then later treated with dihydrotestosterone vs mice with prostate epithelium that had been damaged by lytic virus infection.

MATERIALS AND METHODS

Using allogenic bone marrow grafts from female donor transgenic mice expressing green fluorescent protein transplanted into lethally irradiated males we were able to assess the contributions of bone marrow derived cells to recovery of the prostatic epithelium in 2 distinct systems, including 1) surgical castration followed 1 week later by dihydrotestosterone replacement and 2) intraprostatic viral injection. Eight to 10-week-old male C57/Bl6 mice were distributed among bone marrow donor-->recipient/prostate injury groups, including 5 with C57/Bl6-->C57/Bl6/no injury, 3 with green fluorescent protein-->C57/Bl6/no injury, 3 with green fluorescent protein-->C57/Bl6/vehicle injection, 4 with green fluorescent protein-->C57/Bl6/virus injection and 3 each with green fluorescent protein-->C57/Bl6/castration without and with dihydrotestosterone, respectively. Prostate tissues were harvested 3 weeks after dihydrotestosterone replacement or 14 days following intraprostatic viral injection. Prostate tissue immunofluorescence was performed with antibodies against the epithelial marker cytokeratin 5/8, the hematopoietic marker CD45 and green fluorescent protein.

RESULTS

Mice that sustained prostate injury from vaccinia virus infection with concomitant severe inflammation and glandular disruption showed evidence of bone marrow derived cell reconstitution of prostate epithelium, that is approximately 4% of all green fluorescent protein positive cells in the epithelial compartment 14 days after injury expressed cytokeratin 5/8, similar to the proportion of green fluorescent protein positive cells in the prostate that no longer expressed the hematopoietic marker CD45. When prostatic degeneration/regeneration was triggered by androgen deprivation and reintroduction, no green fluorescent protein positive prostate epithelial cells were detected.

CONCLUSIONS

These findings are consistent with a requirement for inflammation associated architectural destruction for the bone marrow derived cell contribution to the regeneration of prostate epithelium.

In vivo therapeutic responses contingent on Fanconi anemia/BRCA2 status of the tumor

PURPOSE

BRCA2, FANCC, and FANCG gene mutations are present in a subset of pancreatic cancer. Defects in these genes could lead to hypersensitivity to interstrand cross-linkers in vivo and a more optimal treatment of pancreatic cancer patients based on the genetic profile of the tumor.

EXPERIMENTAL DESIGN

Two retrovirally complemented pancreatic cancer cell lines having defects in the Fanconi anemia pathway, PL11 (FANCC-mutated) and Hs766T (FANCG-mutated), as well as several parental pancreatic cancer cell lines with or without mutations in the Fanconi anemia/BRCA2 pathway, were assayed for in vitro and in vivo sensitivities to various chemotherapeutic agents.

RESULTS

A distinct dichotomy of drug responses was observed. Fanconi anemia-defective cancer cells were hypersensitive to the cross-linking agents mitomycin C (MMC), cisplatin, chlorambucil, and melphalan but not to 5-fluorouracil, gemcitabine, doxorubicin, etoposide, vinblastine, or paclitaxel. Hypersensitivity to cross-linking agents was confirmed in vivo; FANCC-deficient xenografts of PL11 and BRCA2-deficient xenografts of CAPAN1 regressed on treatment with two different regimens of MMC whereas Fanconi anemia-proficient xenografts did not. The MMC response comprised cell cycle arrest, apoptosis, and necrosis. Xenografts of PL11 also regressed after a single dose of cyclophosphamide whereas xenografts of genetically complemented PL11(FANCC) did not.

CONCLUSIONS

MMC or other cross-linking agents as a clinical therapy for pancreatic cancer patients with tumors harboring defects in the Fanconi anemia/BRCA2 pathway should be specifically investigated.

Combination of methylated-DNA precipitation and methylation-sensitive restriction enzymes (COMPARE-MS) for the rapid, sensitive and quantitative detection of DNA methylation

Hypermethylation of CpG island (CGI) sequences is a nearly universal somatic genome alteration in cancer. Rapid and sensitive detection of DNA hypermethylation would aid in cancer diagnosis and risk stratification. We present a novel technique, called COMPARE-MS, that can rapidly and quantitatively detect CGI hypermethylation with high sensitivity and specificity in hundreds of samples simultaneously. To quantitate CGI hypermethylation, COMPARE-MS uses real-time PCR of DNA that was first digested by methylation-sensitive restriction enzymes and then precipitated by methyl-binding domain polypeptides immobilized on a magnetic solid matrix. We show that COMPARE-MS could detect five genome equivalents of methylated CGIs in a 1000- to 10 000-fold excess of unmethylated DNA. COMPARE-MS was used to rapidly quantitate hypermethylation at multiple CGIs in >155 prostate tissues, including benign and malignant prostate specimens, and prostate cell lines. This analysis showed that GSTP1, MDR1 and PTGS2 CGI hypermethylation as determined by COMPARE-MS could differentiate between malignant and benign prostate with sensitivities >95% and specificities approaching 100%. This novel technology could significantly improve our ability to detect CGI hypermethylation.

Telomere lengths of translocation-associated and nontranslocation-associated sarcomas differ dramatically

Sarcomas can be divided into those with specific translocations displaying monotonous cytomorphology, and those with complex karyotypes and marked cellular pleomorphism. Telomeres contain terminal DNA sequence repeats that maintain chromosomal stability. Telomeres shorten with cell division and may become dysfunctional leading to chromosomal instability. Using a fluorescence in situ hybridization/immunofluorescence method to assess telomere lengths in archival tissues we analyzed these two types of sarcomas using paraffin-embedded primary tumor specimens. Tissues from nine sarcomas with characteristic translocations (two synovial sarcomas, two alveolar rhabdomyosarcomas, two desmoplastic round cell tumors, and one each of infantile fibrosarcoma, myxoid liposarcoma, cellular congenital mesoblastic nephroma) and nine without (four malignant fibrous histiocytomas, two leiomyosarcomas, one pleomorphic rhabdomyosarcoma, one dedifferentiated chondrosarcoma, and one malignant peripheral nerve sheath tumor) were analyzed. In all (nine of nine) cases with specific translocations, which generally have few karyotypic abnormalities, telomere lengths were similar to or reduced compared to surrounding nonneoplastic tissues. In contrast, telomeres in cases lacking specific translocations, which generally contain complex karyotypes, were often found to be dramatically lengthened and heterogeneous. In addition to markedly elongated telomeres, seven of nine (78%) complex cases exhibited large brightly stained regions corresponding to a specific type of promyelocytic leukemia nuclear body found in immortalized cells that maintain telomeres in a telomerase-independent manner [alternative lengthening of telomeres (ALT) pathway]. This phenotype is unlike that of epithelial neoplasms that typically display complex karyotypes with abnormally short telomeres maintained by the enzyme telomerase. The discovery of heterogeneous telomere lengths and evidence of the ALT pathway in the majority of sarcomas with complex karyotypes supports the existence of a telomere maintenance pathway incapable of full karyotypic stabilization in pleomorphic sarcomas. These findings provide additional molecular-genetic evidence supporting the dichotomous grouping of sarcomas into those with characteristic signature translocations without extensive additional karyotypic abnormalities, and those without such signature translocations that typically display very complex karyotypes, and point to telomere dysfunction as a plausible contributor to the chromosomal aberrations found in complex sarcomas.

Gene expression profiling identifies clinically relevant subtypes of prostate cancer

Prostate cancer, a leading cause of cancer death, displays a broad range of clinical behavior from relatively indolent to aggressive metastatic disease. To explore potential molecular variation underlying this clinical heterogeneity, we profiled gene expression in 62 primary prostate tumors, as well as 41 normal prostate specimens and nine lymph node metastases, using cDNA microarrays containing approximately 26,000 genes. Unsupervised hierarchical clustering readily distinguished tumors from normal samples, and further identified three subclasses of prostate tumors based on distinct patterns of gene expression. High-grade and advanced stage tumors, as well as tumors associated with recurrence, were disproportionately represented among two of the three subtypes, one of which also included most lymph node metastases. To further characterize the clinical relevance of tumor subtypes, we evaluated as surrogate markers two genes differentially expressed among tumor subgroups by using immunohistochemistry on tissue microarrays representing an independent set of 225 prostate tumors. Positive staining for MUC1, a gene highly expressed in the subgroups with "aggressive" clinicopathological features, was associated with an elevated risk of recurrence (P = 0.003), whereas strong staining for AZGP1, a gene highly expressed in the other subgroup, was associated with a decreased risk of recurrence (P = 0.0008). In multivariate analysis, MUC1 and AZGP1 staining were strong predictors of tumor recurrence independent of tumor grade, stage, and preoperative prostate-specific antigen levels. Our results suggest that prostate tumors can be usefully classified according to their gene expression patterns, and these tumor subtypes may provide a basis for improved prognostication and treatment stratification.

The diet, prostate inflammation, and the development of prostate cancer

Evidence that somatic inactivation of GSTP1, encoding the human pi-class glutathione S-transferase, may initiate prostatic carcinogenesis is reviewed along with epidemiological evidence implicating several environment and lifestyle factors, including the diet and sexually transmitted diseases, as prostate cancer risk factors. An integrated model is presented featuring GSTPI function as a 'caretaker' gene during the pathogenesis of prostate cancer, in which the early loss of GSTPI activity renders prostate cells vulnerable to genome damage associated with chronic prostatic inflammation and repeated exposure to carcinogens. The model predicts that the critical prostate carcinogens will be those that are substrates for GSTP1 detoxification and are associated with high prostate cancer risk diet and lifestyle habits.

Pathological and molecular aspects of prostate cancer

This review focuses on new findings and controversial issues in the the pathology and molecular biology of adenocarcinoma of the prostate. Since management of high-grade prostatic intraepithelial neoplasia on needle biopsy--the most common precursor lesion to prostate cancer--is the crucial issue with this lesion, we discuss the risk of cancer subsequent to this histological diagnosis and the issue of whether such neoplasia should be regarded as carcinoma-in-situ. We also look at prostate cancer itself, starting with its diagnosis, reporting on needle biopsy, and reviewing how the most frequently used grading system, the Gleason grading system, affects treatment. The molecular basis of prostate cancer includes inheritable and somatic genetic changes (tumour suppressor genes, loss of heterozygosity, gene targets and regions of chromosomal gain, CpG island promoter methylation, invasion and metastasis suppressor genes, telomere shortening, and genetic instability). Changed gene expression (eg, proliferation-related genes, changes in the androgen receptor, apoptosis and stress-response genes) have potential as biomarkers and therapeutic targets in prostate cancer.

Germline mutations and sequence variants of the macrophage scavenger receptor 1 gene are associated with prostate cancer risk

Deletions on human chromosome 8p22-23 in prostate cancer cells and linkage studies in families affected with hereditary prostate cancer (HPC) have implicated this region in the development of prostate cancer. The macrophage scavenger receptor 1 gene (MSR1, also known as SR-A) is located at 8p22 and functions in several processes proposed to be relevant to prostate carcinogenesis. Here we report the results of genetic analyses that indicate that mutations in MSR1 may be associated with risk of prostate cancer. Among families affected with HPC, we identified six rare missense mutations and one nonsense mutation in MSR1. A family-based linkage and association test indicated that these mutations co-segregate with prostate cancer (P = 0.0007). In addition, among men of European descent, MSR1 mutations were detected in 4.4% of individuals affected with non-HPC as compared with 0.8% of unaffected men (P = 0.009). Among African American men, these values were 12.5% and 1.8%, respectively (P = 0.01). These results show that MSR1 may be important in susceptibility to prostate cancer in men of both African American and European descent.

A phase I trial of CV706, a replication-competent, PSA selective oncolytic adenovirus, for the treatment of locally recurrent prostate cancer following radiation therapy

CV706 is a prostate-specific antigen (PSA)-selective, replication-competent adenovirus that has been shown to selectively kill human prostate cancer xenografts in preclinical models. To study the safety and activity of intraprostatic delivery of CV706, a Phase I dose-ranging study for the treatment of patients with locally recurrent prostate cancer after radiation therapy was conducted. Twenty patients in five groups were treated with between 1 x 10(11) and 1 x 10(13) viral particles delivered by a real-time, transrectal ultrasound-guided transperineal technique using a three-dimensional plan. The primary end point was the determination of treatment-related toxicity. Secondary objectives included evaluation of the antitumor activity of CV706 and monitoring for other correlates of antineoplastic action. In this study, CV706 was found to be safe and was not associated with irreversible grade 3 or any grade 4 toxicity. No grade >1 alterations in liver function tests associated with CV706 administration were observed. Posttreatment prostatic biopsies and detection of a delayed "peak" of circulating copies of virus provided evidence of intraprostatic replication of CV706. The study defined the timing of CV706 shedding into blood and urine as well as the appearance of circulating Ad5 neutralizing antibodies. Finally, this study documents the serum PSA response of treated patients and reveals a dose response showing that all five patients who achieved a > or =50% reduction in PSA were treated with the highest two doses of CV706. This study represents the first clinical translation of a prostate-specific, replication-restricted adenovirus for the treatment of prostate cancer. Taken together, this study documents that intraprostatic delivery of CV706 can be safely administered to patients, even at high doses, and the data also suggest that CV706 possesses enough clinical activity, as reflected by changes in serum PSA, to warrant additional clinical and laboratory investigation.

Cancer cells engineered to secrete granulocyte-macrophage colony-stimulating factor using ex vivo gene transfer as vaccines for the treatment of genitourinary malignancies

When irradiated and administered intradermally as vaccines, cancer cells engineered to secrete high levels of granulocyte-macrophage colony-stimulating factor (GM-CSF) by gene transfer elicit potent anticancer immune responses in a variety of animal tumor models. Upon vaccination, antigens present in the cancer cells are phagocytosed and processed by skin dendritic cells. These dendritic cells then prime anticancer immune responses by presenting antigenic peptides to T cells. The immune responses generated are capable of eradicating small but lethal cancer cell inocula with minimal toxicity in preclinical animal tumor studies. To develop this vaccination strategy for the treatment of human genitourinary cancers, we have conducted phase I clinical trials using human genitourinary cancer cells as sources of cancer cell antigens. In the first human clinical trial of genetically engineered cancer cell vaccines, a phase I clinical trial of kidney cancer cell vaccines (n = 18), kidney cancer cells were removed at surgery, propagated briefly in vitro, and then genetically modified to secrete high levels of GM-CSF via ex vivo transduction with the retrovirus MFG-GM-CSF. After irradiation, the kidney cancer cells were administered as vaccines to 18 patients with advanced kidney cancers. Vaccine treatment, which caused few side effects, nonetheless appeared to trigger anticancer immune responses manifest as conversion of delayed-type hypersensitivity (DTH) skin responses against irradiated autologous cancer cells after vaccination. Biopsies of vaccine sites yielded findings reminiscent of biopsies from preclinical animal model studies, with evidence of vaccine cell recruitment of dendritic cells, T cells, and eosinophils. One patient with measurable kidney cancer metastases treated at the highest vaccine dose level experienced a partial treatment response. The bioactivity of GM-CSF-secreting autologous cancer cell vaccines was confirmed in a phase I clinical trial for prostate cancer (n = 8). Vaccine cells were prepared from surgically harvested prostate tumors by ex vivo transduction with MFG-GM-CSF in a manner similar to that used for the kidney cancer trial. Vaccine treatment was well tolerated and associated with induction of anticancer immunity as assessed using DTH skin testing. In addition, new antiprostate cancer cell antibodies were detected in serum samples from treated men as a consequence of vaccination. These first clinical trials of GM-CSF-secreting cancer cell vaccines for the treatment of genitourinary cancers have demonstrated both safety and bioactivity, in that very few side effects have been seen and anticancer immune responses have been detected. Future clinical studies will be required to assess vaccine treatment efficacy, refine vaccination dose and schedule, define the appropriate clinical context for the use of such vaccines, and ascertain optimal combinations involving vaccines and other local or systemic anticancer treatments.

Genetic alterations in urinary bladder carcinosarcoma: evidence of a common clonal origin

The cellular origin of carcinosarcoma of the bladder is unknown. We addressed this issue by using microsatellite analysis for loss of heterozygosity (LOH) in both the carcinomatous and sarcomatous components of 6 bladder tumors. We tested 40 microsatellite markers from 19 human chromosomes and compared the genetic alterations between the two separately isolated components. The potential relevance of the E-cadherin pathway was also evaluated by immunohistochemistry. All 6 cases revealed identical LOH on chromosomal arms 9p, 9q, 8p, and 8q, corresponding to relatively early events in bladder carcinogenesis. Discordant losses between two alleles in the remaining chromosomes, associated with progression, were seen in all tumors with a trend toward a higher incidence in the more advanced tumors (N1M1 and N1Mx). E-cadherin was strongly expressed in the carcinomatous components (5 of 6), whereas most of sarcomatous elements displayed absence of the protein product (4 of 6). These results indicate that both the carcinomatous and sarcomatous components of carcinosarcoma are derived from a common stem cell. Downregulation of E-cadherin may define one of the pathways responsible for conversion of epithelial cells to the sarcomatous phenotype.

Induction of immunity to prostate cancer antigens: results of a clinical trial of vaccination with irradiated autologous prostate tumor cells engineered to secrete granulocyte-macrophage colony-stimulating factor using ex vivo gene transfer

Vaccination with irradiated granulocyte-macrophage colony-stimulating factor (GM-CSF)-secreting gene-transduced cancer vaccines induces tumoricidal immune responses. In a Phase I human gene therapy trial, eight immunocompetent prostate cancer (PCA) patients were treated with autologous, GM-CSF-secreting, irradiated tumor vaccines prepared from ex vivo retroviral transduction of surgically harvested cells. Expansion of primary cultures of autologous vaccine cells was successful to meet trial specifications in 8 of 11 cases (73%); the yields of the primary culture cell limited the number of courses of vaccination. Side effects were pruritus, erythema, and swelling at vaccination sites. Vaccine site biopsies manifested infiltrates of dendritic cells and macrophages among prostate tumor vaccine cells. Vaccination activated new T-cell and B-cell immune responses against PCA antigens. T-cell responses, evaluated by assessing delayed-type hypersensitivity (DTH) reactions against untransduced autologous tumor cells, were evident in two of eight patients before vaccination and in seven of eight patients after treatment. Reactive DTH site biopsies manifested infiltrates of effector cells consisting of CD45RO+ T-cells, and degranulating eosinophils consistent with activation of both Th1 and Th2 T-cell responses. A distinctive eosinophilic vasculitis was evident near autologous tumor cells at vaccine sites, and at DTH sites. B-cell responses were also induced. Sera from three of eight vaccinated men contained new antibodies recognizing polypeptides of 26, 31, and 150 kDa in protein extracts from prostate cells. The 150-kDa polypeptide was expressed by LNCaP and PC-3 PCA cells, as well as by normal prostate epithelial cells, but not by prostate stromal cells. No antibodies against prostate-specific antigen were detected. These data suggest that both T-cell and B-cell immune responses to human PCA can be generated by treatment with irradiated, GM-CSF gene-transduced PCA vaccines.

Effects of the steroid antagonist RU486 on dimerization of the human progesterone receptor

We previously reported, using a coimmunoprecipitation assay, that the B form (PR-B) of the human progesterone receptor from T47D human breast cancer cells dimerizes in solution with the A receptor (PR-A) and that the extent of dimerization correlates with receptor binding activity for specific DNA sequences [DeMarzo, A.M., Beck, C.A., Oñate, S.A., & Edwards, D.P. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 72-76]. This suggested that solution dimerization is an intermediate step in the receptor activation process. The present study has tested the effects of the progesterone antagonist RU486 on solution dimerization of progesterone receptors (PR). As determined by the coimmunoprecipitation assay, RU486 binding did not impair dimerization of receptors; rather, the antagonist promoted more efficient solution dimerization than the progestin agonist R5020. This enhanced receptor dimerization correlated with a higher DNA binding activity for transformed receptors bound with RU486. RU486 has been shown previously to produce two other alterations in the human PR when compared with R5020. PR-RU486 complexes in solution exhibit a faster sedimentation rate (6 S) on salt-containing sucrose density gradients than PR-R5020 complexes (4 S), and PR-DNA complexes have a faster electrophoretic mobility on gel-shift assays in the presence of RU486. We presently show that the 6 S PR-RU486 complex is a receptor monomer, not a dimer. The increased sedimentation rate and increased mobility on gel-shift assays promoted by RU486 were also observed with recombinant PR-A and PR-B separately expressed in insect cells from baculovirus vectors. These results suggest that RU486 induces a distinct conformational change both in PR monomers in solution and in dimers bound to DNA. We also examined whether conformational changes in PR induced by RU486 would prevent a PR polypeptide bound to RU486 from heterodimerization with another PR polypeptide bound to R5020. To evaluate this, PR-A and PR-B that were separately bound to R5020 or RU486 in whole cells were mixed in vitro. PR-A-RU486 was capable of dimerization with PR-B-R5020, and this was demonstrated for heterodimers both formed in solution and bound to specific DNA. The capability to form heterodimers in vitro raises the possibility that the antagonist action of RU486 in vivo could in part be imposed in a dominant negative fashion through heterodimerization between one receptor subunit bound to an agonist and another bound to RU486.

Mechanisms controlling steroid receptor binding to specific DNA sequences

Mammalian progesterone receptors activated by hormone binding in nuclei of intact cells exhibit substantially higher binding activity for specific DNA sequences than receptors bound with hormone and activated in cell-free cytosol. Differences in DNA-binding activity occur despite the fact that both activated receptor forms sediment at 4S on sucrose gradients and are apparently dissociated from the heat shock protein 90. This suggests that hormone-induced release of heat shock protein 90 from receptors is necessary, but not sufficient for maximal activation of DNA binding. This report is a review of studies from our laboratories that have examined the role of receptor interaction with other nuclear protein factor(s), and receptor dimerization in solution, as additional regulatory steps involved in the process of receptor activation and binding to specific gene sequences.

Ultrastructural localization of matrix vesicles and alkaline phosphatase in the Swarm rat chondrosarcoma: their role in cartilage calcification

Although it is generally acknowledged that matrix vesicles and alkaline phosphatase are required for cartilage calcification, their precise role in initiation or propagation of mineralization remains controversial. We have investigated this problem in a neoplastic model of chondrogenesis, the Swarm rat chondrosarcoma. During serial transplantation these malignant chondrocytes fail to undergo terminal differentiation and do not calcify. To facilitate the study of maturational events in this neoplasm we have developed an intraperitoneal model which grows as discrete free floating tumor nodules. The youngest cells are those on the exterior and maturation progresses towards the center. Ultrastructural examination of the tumor reveals the presence of numerous matrix vesicles in the interterritorial matrix of immature and mature cells. Histochemical localization of alkaline phosphatase reveals a distribution of enzyme activity which varies with the state of maturation of the cells. The most immature cells express large amounts of enzyme on their plasmalemma and in inter-territorial matrix vesicles. The older cells lose membrane activity but maintain activity in their matrix vesicles. These results suggest that while matrix vesicles and/or alkaline phosphatase may be necessary for calcification to proceed, their mere presence is by itself insufficient to initiate or maintain the process.