Androgen-regulated stromal complement component 7 (C7) suppresses prostate cancer growth

The complement system is a major component of the innate immune system that works through the cytolytic effect of the membrane attack complex (MAC). Complement component 7 (C7) is essential for MAC assembly and its precisely regulated expression level is crucial for the cytolytic activity of MAC. We show that C7 is specifically expressed by the stromal cells in both mouse and human prostates. The expression level of C7 inversely correlates with clinical outcomes in prostate cancer. C7 is positively regulated by androgen signaling in the mouse prostate stromal cells. The androgen receptor directly transcriptionally regulates the mouse and human C7. Increasing C7 expression in the C57Bl/6 syngeneic RM-1 and Pten-Kras allografts suppresses tumor growth in vivo. Conversely, C7 haploinsufficiency promotes tumor growth in the transgenic adenocarcinoma of the mouse prostate (TRAMP) model. Interestingly, replenishing C7 in androgen-sensitive Pten-Kras tumors during androgen depletion only slightly enhances cellular apoptosis, highlighting the diverse mechanisms employed by tumors to counteract complement activity. Collectively, our research indicates that augmenting complement activity could be a promising therapeutic approach to impede the development of castration resistance in prostate cancer.

Pathological Effects of Apalutamide in Lower-risk Prostate Cancer: Results From a Phase II Clinical Trial

PURPOSE

Active surveillance is a safe and effective strategy for men with lower-risk prostate cancer who want to avoid local therapy; however, many patients on active surveillance progress to active treatment (eg, prostatectomy or radiation). We hypothesized that apalutamide would decrease active surveillance attrition rates through downstaging low-grade tumors.

MATERIALS AND METHODS

This was an open-label, single-arm, phase II study testing 90 days of oral apalutamide 240 mg daily in men with low- to intermediate-risk prostate cancer on active surveillance. The primary objective was to determine the percentage of patients with a negative biopsy immediately following treatment. Secondary objectives were to assess long-term clinical outcomes, quality of life, safety, and biomarkers of response/resistance.

RESULTS

Twenty-three patients enrolled and 22 completed 90 days of apalutamide with post-treatment biopsy. Fifteen (65%) had Grade Group 1 disease, and all others had Grade Group 2 disease. Seven (30%) had favorable- to intermediate-risk disease. Of 22 evaluable patients, 13 (59%) had no residual cancer on post-treatment biopsy. The median time to first positive biopsy was 364 days (95% CI: 91-742 days). The impact of apalutamide on quality of life was minimal and transient. Decipher risk classifier revealed a greater number of negative post-treatment biopsies in those with higher baseline genomic risk score (P = .01).

CONCLUSIONS

The negative repeat biopsy rate following 90 days of apalutamide was high in men with prostate cancer followed on active surveillance. Apalutamide was safe, well tolerated, and had minimal impact on quality of life. Randomized studies evaluating the effects of apalutamide in men enrolled on active surveillance are warranted.

Stromal FOXF2 suppresses prostate cancer progression and metastasis by enhancing antitumor immunity

Cancer-associated fibroblasts (CAFs) mediate an immunosuppressive effect, but the underlying mechanism remains incompletely defined. Here we show that increasing prostatic stromal Foxf2 suppresses the growth and progression of both syngeneic and autochthonous mouse prostate cancer models in an immunocompetent context. Mechanistically, Foxf2 moderately attenuates the CAF phenotype and transcriptionally downregulates Cxcl5, which diminish the immunosuppressive myeloid cells and enhance T cell cytotoxicity. Increasing prostatic stromal Foxf2 sensitizes prostate cancer to the immune checkpoint blockade therapies. Augmenting lung stromal Foxf2 also mediates an immunosuppressive milieu and inhibits lung colonization of prostate cancer. FOXF2 is expressed higher in the stroma of human transition zone (TZ) than peripheral zone (PZ) prostate. The stromal FOXF2 expression level in primary prostate cancers inversely correlates with the Gleason grade. Our study establishes Foxf2 as a stromal transcription factor modulating the tumor immune microenvironment and potentially explains why cancers are relatively rare and indolent in the TZ prostate.

Abstract 989: Spatial profiling of androgen receptor splice variant 7 transcriptional activity in prostate cancer metastases

Introduction: Androgen receptor splice variant 7 (AR-V7) is expressed in metastases from patients with castration resistant prostate cancer (CRPC) and shows a high level of inter- and intra-tumoral variability. However, the downstream activity generated by AR-V7 in tissue has not been shown. Whether AR-V7 is active in tissue or whether AR-V7 is a non-functioning biomarker with full-length AR is not known. To address this question, we constructed a tissue microarray (TMA) of 56 metastases from 27 patients with CRPC to analyze spatial gene expression using the GeoMx Digital Spatial Profiler. Immunostaining was performed to define epithelial, vascular, and stromal compartments. The stained tissues were then hybridized with barcoded tagged oligonucleotides targeting 2093 unique genes, which included those representing AR, AR-V cryptic exons, AR and neuroendocrine activity, and immune cell markers. One 500 um region of interest (ROI) was assessed per tissue core (approximately 1200 cells). A sequential section from the same TMA was then stained with AR-V7 and AR-C-terminal specific antibodies. ROIs for RNA and protein were selected to be similar between slides. In addition to DSP, each metastasis was assessed by RNA-seq on the bulk tissue.

Results: The most differentially expressed genes (FDR<0.05) based on association with AR-V7 staining were known downstream AR regulated genes including KLK2 and 3, FKBP5, NKX3.1, TMPRSS2, FASN, and TARP. Additionally, genes associated with proliferation and stemness, e.g., POLB, KRT1, SOX2, were significantly expressed. Since 93% of patients were on ADT at time of tissue collection and over 80% also had been treated with either abiraterone or enzalutamide, the increase in AR downstream genes would not be expected to occur from ligand activation of AR-FL. We also have previously shown that knock-down of AR-V7 in LNCaP95 cells results in loss of AR binding to AREs. In these metastases, then, activation of AR downstream genes would be a result of AR-V7 nuclear transport of AR-FL through AR-V7/AR-FL heterodimers or transcriptional activation by AR-V7 homodimers. Of further note, AR cryptic exons 1, 2, and 5 were also significantly expressed in AR-V7 positive ROIs (p< 0.0001). RNA-seq intron/exon junction reads were used to demonstrate that additional AR-Vs, most commonly AR-V9, were also expressed in tissues positive for AR-V7, suggesting that AR splicing is a common event in CRPC. Finally, expression of neuroendocrine (NE) genes INSM1 and TUBB2 were not expressed in AR-V7 positive ROIs (negatively correlated, p<0.001), indicating that AR-V7 and NE phenotypes cannot co-exist in the same cell.

Conclusion: AR-V7 continues to drive prostate cancer through activation of the AR-cistrome. Its expression is heterogenous in metastases along with NE cells, suggesting that in the presence of AR-V7 and NE markers, therapy needs to be directed at the N-terminus of AR and NE components.

Citation Format: Cynthia C. Sprenger, Ilsa Coleman, Michelle Kriner, Lauren Brady, Margaret Hoang, Martine Roudier, Mamatha Damodarasamy, Radhika Patel, Lawrence True, Peter Nelson, Michael Haffner, Stephen Plymate. Spatial profiling of androgen receptor splice variant 7 transcriptional activity in prostate cancer metastases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 989.

Abstract 2200: Multilineage plasticity in prostate cancer through expansion of stem-like luminal epithelial cells with elevated inflammatory signaling

Lineage plasticity is a well-established mechanism of resistance to targeted therapies in lung and prostate cancer, where tumors transition from adenocarcinoma to small-cell or neuroendocrine carcinoma. Single-cell analysis of a cohort of late stage castration-resistant human prostate cancers (CRPC) revealed a greater degree of plasticity than previously appreciated, with multiple distinct neuroendocrine (NEPC), mesenchymal (EMT-like), and other subpopulations detected within single biopsies. To explore the steps responsible for initiation of this process, we utilized two genetically engineered mouse models of prostate cancer that recapitulate progression from adenocarcinoma to neuroendocrine disease. Time course studies reveal expansion of stem-like luminal epithelial cells (Sca1+, Psca+, called L2) that, based on trajectories, gave rise to at least 4 distinct subpopulations, NEPC (Ascl1+), POU2F3 (Pou2f3+), TFF3 (Tff3+) and EMT-like (Vim+, Ncam1+). Such populations are also seen in human prostate and small cell lung cancers. Furthermore, transformed L2-like cells express stem-like and gastrointestinal endoderm-like transcriptional programs, indicative of reemerging developmental plasticity programs, as well as elevated Jak/Stat, interferon, and FGF pathways. Strikingly pharmacologic inhibition of Jak/Stat and FGFR results in reversal of plasticity states and subsequent sensitivity to androgen receptor inhibitors (ARSIs). In sum, while the magnitude of multilineage heterogeneity, both within and across patients, raises considerable treatment challenges, the identification of highly plastic luminal cells as the likely source of this heterogeneity provides a target for more focused therapeutic intervention.

Citation Format: Samir Zaidi, Jimmy Zhao, Joseph Chan, Roudier Martine, Kristine Wadosky, Anuradha Gopalan, Wouter Karthaus, Philip Watson, Lawrence True, Peter Nelson, Howard Scher, Michael Morris, Michael Haffner, David Goodrich, Dana Pe'er, Charles Sawyers. Multilineage plasticity in prostate cancer through expansion of stem-like luminal epithelial cells with elevated inflammatory signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2200.

Paracrine Wnt signaling is necessary for prostate epithelial proliferation

INTRODUCTION

The Wnt proteins play key roles in the development, homeostasis, and disease progression of many organs including the prostate. However, the spatiotemporal expression patterns of Wnt proteins in prostate cell lineages at different developmental stages and in prostate cancer remain inadequately characterized.

METHODS

We isolated the epithelial and stromal cells in the developing and mature mouse prostate by flow cytometry and determined the expression levels of Wnt ligands. We used Visium spatial gene expression analysis to determine the spatial distribution of Wnt ligands in the mouse prostatic glands. Using laser-capture microscopy in combination with gene expression analysis, we also determined the expression patterns of Wnt signaling components in stromal and cancer cells in advanced human prostate cancer specimens. To investigate how the stroma-derived Wnt ligands affect prostate development and homeostasis, we used a Col1a2-CreERT2 mouse model to disrupt the Wnt transporter Wntless specifically in prostate stromal cells.

RESULTS

We showed that the prostate stromal cells are a major source of several Wnt ligands. Visium spatial gene expression analysis revealed a distinct spatial distribution of Wnt ligands in the prostatic glands. We also showed that Wnt signaling components are highly expressed in the stromal compartment of primary and advanced human prostate cancer. Blocking stromal Wnt secretion attenuated prostate epithelial proliferation and regeneration but did not affect cell survival and lineage maintenance.

DISCUSSION

Our study demonstrates a critical role of stroma-derived Wnt ligands in prostate development and homeostasis.

Comparative genomics of primary prostate cancer and paired metastases: insights from 12 molecular case studies

Primary prostate cancer (PCa) can show marked molecular heterogeneity. However, systematic analyses comparing primary PCa and matched metastases in individual patients are lacking. We aimed to address the molecular aspects of metastatic progression while accounting for the heterogeneity of primary PCa. In this pilot study, we collected 12 radical prostatectomy (RP) specimens from men who subsequently developed metastatic castration‐resistant prostate cancer (mCRPC). We used histomorphology (Gleason grade, focus size, stage) and immunohistochemistry (IHC) (ERG and p53) to identify independent tumors and/or distinct subclones of primary PCa. We then compared molecular profiles of these primary PCa areas to matched metastatic samples using whole‐exome sequencing (WES) and amplicon‐based DNA and RNA sequencing. Based on combined pathology and molecular analysis, seven (58%) RP specimens harbored monoclonal and topographically continuous disease, albeit with some degree of intratumor heterogeneity; four (33%) specimens showed true multifocal disease; and one displayed monoclonal disease with discontinuous topography. Early (truncal) events in primary PCa included SPOP p.F133V (one patient), BRAF p.K601E (one patient), and TMPRSS2:ETS rearrangements (eight patients). Activating AR alterations were seen in nine (75%) mCRPC patients, but not in matched primary PCa. Hotspot TP53 mutations, found in metastases from three patients, were readily present in matched primary disease. Alterations in genes encoding epigenetic modifiers were observed in several patients (either shared between primary foci and metastases or in metastatic samples only). WES‐based phylogenetic reconstruction and/or clonality scores were consistent with the index focus designated by pathology review in six out of nine (67%) cases. The three instances of discordance pertained to monoclonal, topographically continuous tumors, which would have been considered as unique disease in routine practice. Overall, our results emphasize pathologic and molecular heterogeneity of primary PCa, and suggest that comprehensive IHC‐assisted pathology review and genomic analysis are highly concordant in nominating the ‘index’ primary PCa area. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Transcriptomic discriminators of response to apalutamide in patients with prostate cancer (PC) on active surveillance (AS)

267

Background: We previously reported the results of a Phase 2 study showing that a high proportion (59%) of men with PC being followed on AS will have a negative post-treatment biopsy after 90 days of apalutamide (Schweizer, et al. SUO Annual Meeting 2020). In order to identify candidate biomarkers for response, we conducted transcriptional profiling of tumor tissue obtained from men enrolled to the aforementioned trial. Methods: We analyzed FFPE tissue obtained from men enrolled to a Phase II study testing 90-days of apalutamide. Transcript profiles were assessed using Affymetrix Microarrays (Decipher Biosciences, Inc). Differences in signaling pathways were assessed between samples at baseline, day (D) 91 (post-treatment) and at D365. We also assessed differences in signaling pathways between patients that did vs. did not have a response (i.e. negative vs. persistent cancer on surveillance biopsy) at D91, which was the primary endpoint of the study. All comparisons were made using a Wilcoxon signed rank test unless otherwise indicated. Results: Samples from 22 subjects who completed 3-months of apalutamide and subsequently underwent post-treatment biopsy were available for analysis. From 19 Baseline and 15 post-treatment tissue samples, 25 passed pathology quality control (N = 12 at baseline, N = 8 at D91 and N = 5 at D365). Principal component analysis revealed distinct transcriptional profiles between tumor samples analyzed at baseline vs. D91. Surprisingly, D365 specimens still demonstrated a distinct profile compared to both baseline and D91 samples. Pathway analysis revealed up-regulation of angiogenesis signaling at D91 (P < 0.01) and D365 (P = 0.03) compared to baseline. As expected, estrogen (P < 0.01) and androgen receptor (P = 0.02) signaling were significantly lower at D91; however, only estrogen signaling was persistently suppressed at D365 (P = 0.03). Basal pathway signatures and markers associated with inflammatory response were also significantly upregulated at D91. There were no significant differences in Gleason grade group (GG) between responders and non-responders: 8/15 (53%) with GG1 vs. 5/7 (71%) with GG2 (Fisher’s exact P = 0.648). Decipher (P = 0.01) and Cuzick (P = 0.03) risk classifiers revealed an enrichment for responses in those with higher risk disease at baseline. There was also an enrichment for responses in those with higher nucleotide excision repair signature (P = 0.03) and those with signatures associated with TP53 mutations (P = 0.02). Conclusions: We observed significant transcriptional changes following 90 days of apalutamide, with evidence of persistent differences up to one year after enrollment. Higher baseline risk score was associated with improved responses to apalutamide treatment. Prospective studies evaluating the benefit of apalutamide in men on AS with higher risk transcriptional profiles are warranted. Clinical trial information: NCT02721979.

Novel, emerging and provisional renal entities: The Genitourinary Pathology Society (GUPS) update on renal neoplasia

The Genitourinary Pathology Society (GUPS) undertook a critical review of the recent advances in renal neoplasia, particularly focusing on the newly accumulated evidence post-2016 World Health Organization (WHO) classification. In the era of evolving histo-molecular classification of renal neoplasia, morphology is still key. However, entities (or groups of entities) are increasingly characterized by specific molecular features, often associated either with recognizable, specific morphologies or constellations of morphologies and corresponding immunohistochemical profiles. The correct diagnosis has clinical implications leading to better prognosis, potential clinical management with targeted therapies, may identify hereditary or syndromic associations, which may necessitate appropriate genetic testing. We hope that this undertaking will further facilitate the identification of these entities in practice. We also hope that this update will bring more clarity regarding the evolving classification of renal neoplasia and will further reduce the category of "unclassifiable renal carcinomas/tumors". We propose three categories of novel entities: (1) "Novel entity", validated by multiple independent studies; (2) "Emerging entity", good compelling data available from at least two or more independent studies, but additional validation is needed; and (3) "Provisional entity", limited data available from one or two studies, with more work required to validate them. For some entities initially described using different names, we propose new terminologies, to facilitate their recognition and to avoid further diagnostic dilemmas. Following these criteria, we propose as novel entities: eosinophilic solid and cystic renal cell carcinoma (ESC RCC), renal cell carcinoma with fibromyomatous stroma (RCC FMS) (formerly RCC with leiomyomatous or smooth muscle stroma), and anaplastic lymphoma kinase rearrangement-associated renal cell carcinoma (ALK-RCC). Emerging entities include: eosinophilic vacuolated tumor (EVT) and thyroid-like follicular renal cell carcinoma (TLFRCC). Finally, as provisional entities, we propose low-grade oncocytic tumor (LOT), atrophic kidney-like lesion (AKLL), and biphasic hyalinizing psammomatous renal cell carcinoma (BHP RCC).

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.

Abstract PO-017: Annotation-free 3D gland segmentation with generative image-sequence translation for prostate cancer risk assessment

1. Purpose We developed an annotation-free image-translation-based approach for 3D segmentation of prostate glands within 3D-histology datasets of whole biopsies stained with a low-cost and rapid-diffusing fluorescent analog of H&E. 2. Introduction The current diagnostic gold standard of histopathology provides a limited 2D view of complex 3D glandular structures in prostate specimens, which contributes to high interobserver variability and reduced prognostic accuracy. We have recently developed nondestructive 3D pathology methods based on open-top light-sheet (OTLS) microscopy. In order to train prognostic models based on 3D glandular morphology, we have developed an objective (biomarker-based) 3D gland-segmentation method that does not rely upon tedious and subjective manual annotations, and which can operate on images of tissue stained with a cheap and fast-diffusing (small molecule) fluorescent analog of H&E. 3. Methods We first convert H&E-analog images into synthetic 3D immunofluorescence (IF) images of cytokeratin-8 (CK8), a biomarker expressed by the luminal epithelial cells that surround all prostate glands. This conversion was performed by treating the 3D data as sequences of 2D images and adapting a generative adversarial network (GAN)-based video-synthesis model to perform image-sequence translation with high depth-wise continuity between frames. Based on the synthetic CK8 images, glands were then objectively segmented in 3D using a thresholding/morphology-based algorithm. This two-step method obviates the need for labor-intensive and subjective manual 3D annotations, as would be needed to train a single-step segmentation model. A 3D structural similarity (SSIM) index was assessed between synthetic and real CK8 images. In addition, based on ground-truth manual annotations of glands in ten 0.2-mm3 regions, we calculated voxel-based Dice coefficients to compare our segmentation accuracy vs. two baseline methods. 4. Results The synthetic CK8 images exhibited high fidelity (3D SSIM = 0.696) and optimal continuity with depth. Our segmentation accuracy outperformed two baseline methods, with Dice coefficients (averaged for 10 samples) of: 0.882 (our method), 0.725 (3D watershed), 0.643 (2D U-net). We are now applying our method to 3D histology datasets of whole biopsies (n &gt; 1000) acquired ex vivo from prostatectomy specimens (N ~ 200), where we are extracting 3D histomorphometric gland features to predict biochemical recurrence (BCR) post-prostatectomy in men with prostate cancer. 5. Conclusions Our annotation-free segmentation method relies upon generative synthetic 3D IF images from H&E-analog images in order to objectively segment the 3D prostate gland network. These accurate 3D segmentations are being extended to whole-biopsy 3D pathology datasets for prostate cancer risk assessment.

Citation Format: Weisi Xie, Adam Glaser, Nicholas Reder, Nadia Postupna, Chenyi Mao, Can Koyuncu, Patrick Leo, Robert Serafin, Hongyi Huang, Anant Madabhushi, Lawrence True, Jonathan T.C. Liu. Annotation-free 3D gland segmentation with generative image-sequence translation for prostate cancer risk assessment [abstract]. In: Proceedings of the AACR Virtual Special Conference on Artificial Intelligence, Diagnosis, and Imaging; 2021 Jan 13-14. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(5_Suppl):Abstract nr PO-017.

De novo induction of lineage plasticity from human prostate luminal epithelial cells by activated AKT1 and c-Myc

Neuroendocrine prostate cancer (NEPC) is an aggressive variant of prostate cancer that either develops de novo or arises from prostate adenocarcinoma as a result of treatment resistance. Although the prostate basal cells have been shown to directly generate tumor cells with neuroendocrine features when transduced with oncogenic signaling, the identity of the cell-of-origin for de novo NEPC remains unclear. We show that the TACSTD2^high human prostate luminal epithelia cells highly express SOX2 and are relatively enriched in the transition zone prostate. Both TACSTD2^high and TACSTD2^low luminal cells transduced by activated AKT and c-Myc can form organoids containing versatile clinically relevant tumor cell lineages with regard to the expression of AR and the neuroendocrine cell markers Synaptophysin and Chromogranin A. Tumor organoid cells derived from the TACSTD2^high luminal cells are more predisposed to neuroendocrine differentiation along passaging and are relatively more castration-resistant. Knocking down TACSTD2 and SOX2 both attenuate neuroendocrine differentiation of tumor organoid cells. This study demonstrates de novo neuroendocrine differentiation of the human prostate luminal epithelial cells induced by caAKT and c-Myc and reveals an impact of cellular status on initiation of lineage plasticity.

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.

Sporadic oncocytic tumors with features intermediate between oncocytoma and chromophobe renal cell carcinoma: comprehensive clinicopathological and genomic profiling

Morphology, clinical behavior, and genomic profiles of renal oncocytoma (RO) and its malignant counterpart chromophobe renal cell carcinoma (ChRCC) are distinctly different. However, there is a substantial group of sporadic oncocytic tumors with peculiar hybrid phenotypes as well as a perplexing degree of morphologic and immunohistochemical overlap between classic RO and ChRCC with eosinophilic cytoplasm. The aim of this study is to provide detailed characterization of these hybrid tumors.Thirty-eight sporadic oncocytic neoplasms with ambiguous morphology from two institutions were reviewed by 4 pathologists. CKIT positivity was used as a selection criterion. We correlated CK7 and S100A1 immunostaining and detailed morphologic features with cytogenetic profiles. DNA from the formalin-fixed paraffin-embedded tissues was extracted and analyzed using cytogenomic microarray analysis (CMA) to evaluate copy number alterations (CNA) and ploidy. CMA categorized cases into 3 groups: RO (N = 21), RO variant (N = 7), and ChRCC (N = 10). Cytogenetic RO had either no CNA (48%) or loss of chromosome 1p, X, or Y (52%). RO variant had additional chromosomal losses [-9q, -14 (n = 2), -13] and chromosomal gains [+1q (n = 2), +4, +7 (n = 2), +13, +19, +20, and +22]. ChRCCs were either hypodiploid with numerous monosomies (40%) or hypotetraploid with multiple relative losses (60%). RO, RO variant, and ChRCC groups differed significantly in tumor architecture (p < 0.01), stroma (p = 0.013), presence of nuclear wrinkling, perinuclear halos, and well-defined cell borders in >5% of cells (p < 0.01), focal cell clearing (p = 0.048) and CK7 expression (p < 0.02). Pathologic prediction of the cytogenetic subtype using only two categories (benign RO or malignant ChRCC) would overcall or undercall up to 40% of tumors that were ChRCC based on cytogenetics. This finding provides the rationale for an intermediate diagnostic category of the so-called hybrid tumors (hybrid oncocytic/chromophobe tumor [HOCT]). HOCT was a heterogeneous group enriched for cytogenetic RO variant. Other HOCTs have a profile of either RO or ChRCC. The genomic profile allows classification of oncocytic tumors with ambiguous morphology into RO, RO variant, and ChRCC. Several architectural and cytologic features combined with CK7 expression are significantly associated with cytogenetic RO, RO variant, or ChRCC tumors. Doubled hypodiploidy by whole-genome endoduplication is a common phenomenon in eosinophilic ChRCC.

Gene fusion analysis in renal cell carcinoma by FusionPlex RNA-sequencing and correlations of molecular findings with clinicopathological features

Translocation renal cell carcinoma (tRCC) affects younger patients and often presents as advanced disease. Accurate diagnosis is required to guide clinical management. Here we evaluate the RNA-sequencing FusionPlex platform with a 115-gene panel including TFE3 and TFEB for tRCC diagnosis and correlate molecular findings with clinicopathological features. We reviewed 996 consecutive RCC cases from our institution over the preceding 7 years and retrieved 17 cases with histological and immunohistochemical features highly suggestive of either TFE3 (n = 16) or TFEB (n = 1). Moderate to strong labeling for TFE3 was present in 15 cases; two cases with weak TFE3 expression were melan-A or cathepsin-K positive. RNA-sequencing detected gene rearrangements in eight cases: PRCC-TFE3 (3), ASPSCR1-TFE3 (2), LUC7L3-TFE3 (1), SFPQ-TFE3 (1), and a novel SETD1B-TFE3 (1). FISH assays of 11 tumors verified six positive cases concordant with FusionPlex analysis results. Two other cases were confirmed by RT-PCR. FusionPlex was superior to FISH by providing precise breakpoints for tRCC-related genes in a single assay and allowing identification of both known and novel fusion partners, thereby facilitating clinicopathological correlations as fusion partners can influence tumor appearance, immunophenotype, and behavior. Cases with partner genes PRCC and novel partner SETD1B were associated with prominent papillary architecture while cases with partner genes ASPSCR1 and LUC7L3 were associated with a predominantly nested/alveolar pattern. The case with SFPQ-TFE3 fusion was characterized by biphasic morphology mimicking TFEB-like translocation RCC. We recommend FusionPlex analysis of RCC in patients under age 50 or when the histologic appearance suggests tRCC.

Genomic Drivers of Poor Prognosis and Enzalutamide Resistance in Metastatic Castration-resistant Prostate Cancer

BACKGROUND

Metastatic castration-resistant prostate cancer (mCRPC) is the lethal form of the disease. Several recent studies have identified genomic alterations in mCRPC, but the clinical implications of these genomic alterations have not been fully elucidated.

OBJECTIVE

To use whole-genome sequencing (WGS) to assess the association between key driver gene alterations and overall survival (OS), and to use whole-transcriptome RNA sequencing to identify genomic drivers of enzalutamide resistance.

DESIGN, SETTING, AND PARTICIPANTS

We performed survival analyses and gene set enrichment analysis (GSEA) on WGS and RNA sequencing results for a cohort of 101 mCRPC patients.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

OS was the clinical endpoint for all univariate and multivariable survival analyses. Candidate drivers of enzalutamide resistance were identified in an unbiased manner, and mutations of the top candidate were further assessed for enrichment among enzalutamide-resistant patients using Fisher's exact test.

RESULTS AND LIMITATIONS

Harboring two DNA alterations in RB1 was independently predictive of poor OS (median 14.1 vs 42.0mo; p=0.007) for men with mCRPC. GSEA identified the Wnt/β-catenin pathway as the top differentially modulated pathway among enzalutamide-resistant patients. Furthermore, β-catenin mutations were exclusive to enzalutamide-resistant patients (p=0.01) and independently predictive of poor OS (median 13.6 vs 41.7mo; p=0.025).

CONCLUSIONS

The presence of two RB1 DNA alterations identified in our WGS analysis was independently associated with poor OS among men with mCRPC. The Wnt/β-catenin pathway plays an important role in enzalutamide resistance, with differential pathway expression and enrichment of β-catenin mutations in enzalutamide-resistant patients. Moreover, β-catenin mutations were predictive of poor OS in our cohort.

PATIENT SUMMARY

We observed a correlation between genomic findings for biopsy samples from metastases from men with metastatic castration-resistant prostate cancer (mCRPC) and clinical outcomes. This work sheds new light on clinically relevant genomic alterations in mCRPC and provides a roadmap for the development of new personalized treatment regimens in mCRPC.

Spatially Restricted Stromal Wnt Signaling Restrains Prostate Epithelial Progenitor Growth through Direct and Indirect Mechanisms

Cell-autonomous Wnt signaling has well-characterized functions in controlling stem cell activity, including in the prostate. While niche cells secrete Wnt ligands, the effects of Wnt signaling in niche cells per se are less understood. Here, we show that stromal cells in the proximal prostatic duct near the urethra, a mouse prostate stem cell niche, not only produce multiple Wnt ligands but also exhibit strong Wnt/β-catenin activity. The non-canonical Wnt ligand Wnt5a, secreted by proximal stromal cells, directly inhibits proliefration of prostate epithelial stem or progenitor cells whereas stromal cell-autonomous canonical Wnt/β-catenin signaling indirectly suppresses prostate stem or progenitor activity via the transforming growth factor β (TGFβ) pathway. Collectively, these pathways restrain the proliferative potential of epithelial cells in the proximal prostatic ducts. Human prostate likewise exhibits spatially restricted distribution of stromal Wnt/β-catenin activity, suggesting a conserved mechanism for tissue patterning. Thus, this study shows how distinct stromal signaling mechanisms within the prostate cooperate to regulate tissue homeostasis.

Clinical and Genomic Characterization of Treatment-Emergent Small-Cell Neuroendocrine Prostate Cancer: A Multi-institutional Prospective Study

Purpose The prevalence and features of treatment-emergent small-cell neuroendocrine prostate cancer (t-SCNC) are not well characterized in the era of modern androgen receptor (AR)-targeting therapy. We sought to characterize the clinical and genomic features of t-SCNC in a multi-institutional prospective study. Methods Patients with progressive, metastatic castration-resistant prostate cancer (mCRPC) underwent metastatic tumor biopsy and were followed for survival. Metastatic biopsy specimens underwent independent, blinded pathology review along with RNA/DNA sequencing. Results A total of 202 consecutive patients were enrolled. One hundred forty-eight (73%) had prior disease progression on abiraterone and/or enzalutamide. The biopsy evaluable rate was 79%. The overall incidence of t-SCNC detection was 17%. AR amplification and protein expression were present in 67% and 75%, respectively, of t-SCNC biopsy specimens. t-SCNC was detected at similar proportions in bone, node, and visceral organ biopsy specimens. Genomic alterations in the DNA repair pathway were nearly mutually exclusive with t-SCNC differentiation ( P = .035). Detection of t-SCNC was associated with shortened overall survival among patients with prior AR-targeting therapy for mCRPC (hazard ratio, 2.02; 95% CI, 1.07 to 3.82). Unsupervised hierarchical clustering of the transcriptome identified a small-cell-like cluster that further enriched for adverse survival outcomes (hazard ratio, 3.00; 95% CI, 1.25 to 7.19). A t-SCNC transcriptional signature was developed and validated in multiple external data sets with > 90% accuracy. Multiple transcriptional regulators of t-SCNC were identified, including the pancreatic neuroendocrine marker PDX1. Conclusion t-SCNC is present in nearly one fifth of patients with mCRPC and is associated with shortened survival. The near-mutual exclusivity with DNA repair alterations suggests t-SCNC may be a distinct subset of mCRPC. Transcriptional profiling facilitates the identification of t-SCNC and novel therapeutic targets.

The California Multidrug-Resistant Tuberculosis Consult Service: a partnership of state and local programs

Background: The US Centers for Disease Control and Prevention recommend expert consultation for multi-drug-resistant tuberculosis (MDR-TB) cases. In 2002, the California MDR-TB Service was created to provide expert MDR-TB consultations. We describe the characteristics, treatment outcomes and management of patients referred to the Service. Methods: Surveillance data were used for descriptive analysis of cases, with consultation during July 2002-December 2012. Clinical consultation data and modified World Health Organization indicators were used to assess the care and management of cases, with consultation from January 2009 to December 2012. Results: Of 339 MDR-TB patients, 140 received a consultation. The proportion of patients receiving a consultation increased from 12% in 2002 to 63% in 2012. There were 24 pre-extensively drug-resistant TB and 5 patients with extensively drug-resistant TB. The majority (n = 123, 88%) completed treatment, 5 (4%) died, 7 (5%) moved before treatment completion, 4 (3%) stopped treatment due to an adverse event and 1 (1%) had an unknown outcome. Indicator data showed that 86% underwent rapid molecular drug susceptibility testing, 98% received at least four drugs to which they had known or presumed susceptibility, and 93% culture converted within 6 months. Conclusions: Consultations with the MDR-TB Service increased over time. Results highlight successful treatment and indicator outcomes.

TWIST1-WDR5-Hottip Regulates Hoxa9 Chromatin to Facilitate Prostate Cancer Metastasis

TWIST1 is a transcription factor critical for development that can promote prostate cancer metastasis. During embryonic development, TWIST1 and HOXA9 are coexpressed in mouse prostate and then silenced postnatally. Here we report that TWIST1 and HOXA9 coexpression are reactivated in mouse and human primary prostate tumors and are further enriched in human metastases, correlating with survival. TWIST1 formed a complex with WDR5 and the lncRNA Hottip/HOTTIP, members of the MLL/COMPASS-like H3K4 methylases, which regulate chromatin in the Hox/HOX cluster during development. TWIST1 overexpression led to coenrichment of TWIST1 and WDR5 as well as increased H3K4me3 chromatin at the Hoxa9/HOXA9 promoter, which was dependent on WDR5. Expression of WDR5 and Hottip/HOTTIP was also required for TWIST1-induced upregulation of HOXA9 and aggressive cellular phenotypes such as invasion and migration. Pharmacologic inhibition of HOXA9 prevented TWIST1-induced aggressive prostate cancer cellular phenotypes in vitro and metastasis in vivo This study demonstrates a novel mechanism by which TWIST1 regulates chromatin and gene expression by cooperating with the COMPASS-like complex to increase H3K4 trimethylation at target gene promoters. Our findings highlight a TWIST1-HOXA9 embryonic prostate developmental program that is reactivated during prostate cancer metastasis and is therapeutically targetable. Cancer Res; 77(12); 3181-93. ©2017 AACR.

A Novel System for Estimating Residual Disease and Pathologic Response to Neoadjuvant Treatment of Prostate Cancer

BACKGROUND

Pathologic variables that characterize response of prostate carcinoma to current neoadjuvant therapy have not been characterized in detail. This study reports (i) the histological features of prostate cancer treated with abiraterone and enzalutamide and inter-pathologist variance in identifying these features, and (ii) the effect of the novel androgen deprivation agents on residual cancer volume.

METHODS

We reviewed sections of prostatectomies from 37 patients treated with neoadjuvant agents and 22 untreated patients, tabulated the frequency of nine features of cancer (intact cancer glands, isolated cancer cells, poorly formed glands, cribriform architecture, clear spaces, intraductal carcinoma, solid sheets of cancer cells, prominent nucleoli, and previously described ABC grouping) and two features of benign glands (prominent basal cells and coalescent corpora amylacea). We used several methods, including a novel metric (visual grid system), to estimate residual tumor volume.

RESULTS

The most highly reproducible features were ABC grouping (κ = 0.56-0.7), presence of intraductal carcinoma (κ = 0.34-0.72), cribriform architecture (κ = 0.42-0.68), solid sheets of tumor cells (κ = 0.44-0.56), and coalescent corpora amylacea (κ = 0.4-0.54). Among poorly reproducible features were prominent nucleoli (κ = 0.03-0.11), clear spaces (κ = 0.05-0.07), and poorly formed cancer glands (κ = 0.02-0.1). Determination of tumor mass was excellent regardless of the method used-maximum tumor size (κ = 0.9-0.94), tumor area (κ = 0.94-0.96), and grid-based tumor cellularity (κ = 0.9).

CONCLUSIONS

We propose using a set of parameters including maximum tumor size, tumor area/volume, cellularity, volume, and ABC grouping for evaluating radical prostatectomies post-neoadjuvant therapy. Prostate 76:1285-1292, 2016. © 2016 Wiley Periodicals, Inc.

Comparative Effectiveness of a Patient Centered Pathology Report for Bladder Cancer Care

PURPOSE

Patients have unprecedented access to their medical records. However, many documents, such as pathology reports, may be beyond the health literacy of most patients. We compared the effectiveness of bladder biopsy patient centered pathology reports with standard reports.

MATERIALS AND METHODS

Local bladder cancer experts reached consensus on the important elements of a bladder biopsy pathology report to inform prognosis and counseling. Patient focus groups identified the patient centered formats and language to convey these elements and constructed a pilot patient centered pathology report. A total of 40 patients undergoing bladder biopsy were block randomized to receive the standard report with or without the patient centered report. We assessed patient self-efficacy, and provider communication and empathy, and tested bladder cancer knowledge at pathology disclosure and 1 month later. We compared study groups with descriptive statistics.

RESULTS

Experts identified stage, grade and histology as the most important elements of a bladder biopsy pathology report. Patients prioritized 3 themes, including narrative format, tumor stage illustration and risk stratification for recurrence. A total of 39 patients completed initial and followup assessments. Patients with the patient centered pathology report had improved ability to identify cancer stage compared to those with the standard report. Initially 58% of patients with the standard report vs 20% with the patient centered report were unable to describe stage but at followup this incidence was 47% vs 15% (p = 0.02 and 0.03, respectively). Those with the patient centered report also trended toward improved identification of cancer grade. Provider communication trended toward improvement for the patient centered report. Ratings of patient self-efficacy did not differ by report.

CONCLUSIONS

Patient centered pathology reports are associated with greater patient knowledge about the bladder cancer diagnosis. The reports may aid patient-provider communication. This pilot study may serve as a model for the development of patient centered pathology reports for other cancers.

Cells Comprising the Prostate Cancer Microenvironment Lack Recurrent Clonal Somatic Genomic Aberrations

Prostate cancer-associated stroma (CAS) plays an active role in malignant transformation, tumor progression, and metastasis. Molecular analyses of CAS have demonstrated significant changes in gene expression; however, conflicting evidence exists on whether genomic alterations in benign cells comprising the tumor microenvironment (TME) underlie gene expression changes and oncogenic phenotypes. This study evaluates the nuclear and mitochondrial DNA integrity of prostate carcinoma cells, CAS, matched benign epithelium and benign epithelium-associated stroma by whole-genome copy-number analyses, targeted sequencing of TP53, and FISH. Array comparative genomic hybridization (aCGH) of CAS revealed a copy-neutral diploid genome with only rare and small somatic copy-number aberrations (SCNA). In contrast, several expected recurrent SCNAs were evident in the adjacent prostate carcinoma cells, including gains at 3q, 7p, and 8q, and losses at 8p and 10q. No somatic TP53 mutations were observed in CAS. Mitochondrial DNA (mtDNA) extracted from carcinoma cells and stroma identified 23 somatic mtDNA mutations in neoplastic epithelial cells, but only one mutation in stroma. Finally, genomic analyses identified no SCNAs, LOH, or copy-neutral LOH in cultured cancer-associated fibroblasts, which are known to promote prostate cancer progression in vivo

IMPLICATIONS

The gene expression changes observed in prostate cancer-adjacent stroma and the attendant contribution of the stroma to the development and progression of prostate cancer are not due to frequent or recurrent genomic alterations in the TME.

Abstract 1989: SRRM4 and the loss of REST may promote the emergence of the neuroendocrine /neuronal phenotype in castration resistant prostate cancer

Introduction: Recent findings suggest that neuroendocrine/neuronal (NE) differentiation may be associated with the development of metastatic castration-resistant prostate cancer (CRPC). Our objective was to characterize the NE phenotype in CRPC.

Methods: Using specimens obtained at rapid autopsy at the University of Washington, 2 tissue microarrays were made from (1) 155 metastatic sites from 50 autopsy patients who died from CRPC and (2) 24 LuCaP prostate cancer xenografts. NE markers, including Chromogranin A (CHGA), Synaptophysin (SYN), androgen receptor (AR), and prostate specific antigen (PSA) were analyzed by immunohistochemistry (IHC). To characterize the molecular features of the NE phenotype in CRPC, transcript levels in 78 corresponding metastatic sites and 24 LuCaP xenografts were determined by hybridization to whole genome microarrays.

Results: Co-expression of CHGA and SYN (by at least &gt;10% of cells) was observed in 22 of 155 sites (11 sites were AR-). PSA, a surrogate of AR activity, was absent in all NE CRPC tumors that did not express AR. Four of the 24 LuCaP xenografts displayed an NE phenotype (all were AR-). Gene expression data were generated from 78 laser captured metastases, and 24 LuCaP xenografts. Five metastatic sites were CHGA+, SYN+ and AR-, and 5 were CHGA+, SYN+ and AR+, 4 LuCaP xenografts were CHGA+, SYN+ and AR- by IHC. Only CHGA+, SYN+ sites had a NE transcript signature, with the CHGA+, SYN+ and AR- specimens expressing a greater number of genes associated with the NE phenotype. In addition, a decrease in the expression of REST was observed in the 10 CHGA+, SYN+ metastatic sites and LuCaP xenografts. SRRM4 transcript expression was associated with the NE signature in 5 of the 6 CHGA+, SYN+ patients and the LuCaP xenografts. Furthermore RT-PCR comparing the epithelial to the NE LuCaP xenografts correlated the expression of SRRM4 with a splice variant of REST that lacks the repressor domain and the NE phenotype.

Conclusions: Our data suggest that a) the CRPC NE phenotype can be defined by CHGA+, SYN+ dual positivity and is more common in CRPC than historically in hormone sensitive primary disease, b) NE status from different sites in the same patient can be heterogeneous c) the NE phenotype is not necessarily associated with the loss of AR activity, and d) the loss of REST expression or the splicing of REST through the activity of SRRM4 could promote the NE phenotype in CRPC. These molecular studies suggest that evolution from hormone sensitive, to castration resistant on to NE disease involves the loss of REST or the loss of REST repressor activity due to alternate splicing by SRRM4.

Citation Format: Xiaotun Zhang, Ilsa Coleman, Roger Coleman, Lisha Brown, Lori Kollath, Lisly Chéry, Jared Lucas, Eva Corey, Martine Roudier, Paul Lange, Celestia Higano, Lawrence True, Peter Nelson, Robert Vessella, Colm Morrissey. SRRM4 and the loss of REST may promote the emergence of the neuroendocrine /neuronal phenotype in castration resistant prostate cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1989. doi:10.1158/1538-7445.AM2014-1989

The critical role of the pathologist in determining eligibility for active surveillance as a management option in patients with prostate cancer: consensus statement with recommendations supported by the College of American Pathologists, International Society of Urological Pathology, Association of Directors of Anatomic and Surgical Pathology, the New Zealand Society of Pathologists, and the Prostate Cancer Foundation

CONTEXT

Prostate cancer remains a significant public health problem. Recent publications of randomized trials and the US Preventive Services Task Force recommendations have drawn attention to overtreatment of localized, low-risk prostate cancer. Active surveillance, in which patients undergo regular visits with serum prostate-specific antigen tests and repeat prostate biopsies, rather than aggressive treatment with curative intent, may address overtreatment of low-risk prostate cancer. It is apparent that a greater awareness of the critical role of pathologists in determining eligibility for active surveillance is needed.

OBJECTIVES

To review the state of current knowledge about the role of active surveillance in the management of prostate cancer and to provide a multidisciplinary report focusing on pathologic parameters important to the successful identification of patients likely to succeed with active surveillance, to determine the role of molecular tests in increasing the safety of active surveillance, and to provide future directions.

DESIGN

Systematic review of literature on active surveillance for low-risk prostate cancer, pathologic parameters important for appropriate stratification, and issues regarding interobserver reproducibility. Expert panels were created to delineate the fundamental questions confronting the clinical and pathologic aspects of management of men on active surveillance.

RESULTS

Expert panelists identified pathologic parameters important for management and the related diagnostic and reporting issues. Consensus recommendations were generated where appropriate.

CONCLUSIONS

Active surveillance is an important management option for men with low-risk prostate cancer. Vital to this process is the critical role pathologic parameters have in identifying appropriate candidates for active surveillance. These findings need to be reproducible and consistently reported by surgical pathologists with accurate pathology reporting.

Aggressive variants of castration-resistant prostate cancer

A subset of patients with advanced castration-resistant prostate cancer may eventually evolve into an androgen receptor (AR)-independent phenotype, with a clinical picture associated with the development of rapidly progressive disease involving visceral sites and hormone refractoriness, often in the setting of a low or modestly rising serum prostate-specific antigen level. Biopsies performed in such patients may vary, ranging from poorly differentiated carcinomas to mixed adenocarcinoma-small cell carcinomas to pure small cell carcinomas. These aggressive tumors often demonstrate low or absent AR protein expression and, in some cases, express markers of neuroendocrine differentiation. Because tumor morphology is not always predicted by clinical behavior, the terms "anaplastic prostate cancer" or "neuroendocrine prostate cancer" have been used descriptively to describe these rapidly growing clinical features. Patients meeting clinical criteria of anaplastic prostate cancer have been shown to predict for poor prognosis, and these patients may be considered for platinum-based chemotherapy treatment regimens. Therefore, understanding variants within the spectrum of advanced prostate cancer has important diagnostic and treatment implications.

Abstract 804: Disseminated tumor cell heterogeneity and dormancy in prostate cancer

Prostate cancer (PCa) can remain in the bone marrow for a prolonged period of time (&gt;5 years) while the patient shows no evidence of disease before the cancer eventually recurs. Dormant cancer cells can be detected in bone, the principal metastatic site of PCa, and these bone-homing cancer cells are known as disseminated tumor cells (DTC). Little information is available on the heterogeneity and dormancy of DTC in PCa. In this study, we isolated and compared the gene expression profile of individual DTC (n=45) from the bone marrow of 4 PCa patients with no evidence of disease and 5 patients with advanced disease. Using principle component analysis and cluster analysis of the 1000 most variable genes, we determined the heterogeneity of the DTC population within each patient. To identify a dormancy signature from DTC in the bone marrow and primary PCa cells, we carried out two gene expression analyses: DTC in patients with no evidence of disease vs. those with advanced disease, and primary PCa tissues from patients with a short vs. long dormancy period post radical prostatectomy (8-86 months). Genes associated in other cancers with cellular senescence, cell-cycle inhibition, and dormancy were analyzed. Candidate genes from both gene expression arrays were validated at the protein level by a tissue microarray consisting of 64 primary PCa cases that recurred after either a short or long dormancy period post radical prostatectomy (6-121 months).

The identification of heterogeneous gene signatures in DTC and novel proteins that promote dormancy will guide the development of possible biomarkers and therapeutic targets to prevent PCa recurrence, possibly by either eliminating DTC or inhibiting their escape from dormancy.

Citation Format: Hung-Ming Lam, Lisly Chéry, Ilsa Coleman, Bryce Lakely, Sandy Larson, Roger Coleman, Lisha Brown, Kathy Doan, Jennifer Noteboom, Xiaotun Zhang, Lawrence True, Peter Nelson, Bruce Montgomery, Paul Lange, Linda Snyder, Robert Vessella, Colm Morrissey. Disseminated tumor cell heterogeneity and dormancy in prostate cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 804. doi:10.1158/1538-7445.AM2013-804

Abstract 305: The biological and molecular characterization of clinically relevant prostate cancer xenograft lines (LuCaP series), including responses to therapy

Introduction:

Prostate cancer (PCa) is a heterogeneous disease, which results in an unpredictable and varied response to therapy. A limitation in unraveling the complexities of PCa and developing / evaluating novel therapeutic strategies has been the lack of pre-clinical models that closely replicate this heterogeneity. To overcome this limitation we have established over 3 dozen PCa xenograft lines (LuCaP series).

Methods:

Characterization of the xenograft lines derived from PCa primaries and metastases includes: (a) growth properties, (b) expression of 45 biomarkers by immunohistochemistry (IHC), (c) gene expression, (d) copy number gains and losses, (e) expression of the androgen receptor (AR) and its splice variants, (f) bone response (i.e. osteoblastic, osteolytic or mixed), and (g) response to therapy, i.e. androgen ablation, docetaxel and anti-IGF-1R.

Results:

Forty distinct xenograft lines comprise the current LuCaP panel. Four are neuroendocine, 12 are castration resistant (CR) sublines and 7 are abiraterone or MDV-3100 resistant sublines. Comprehensive characterization studies have been done on 24 lines. All lines histologically resemble the originating clinical specimen. Unsupervised gene expression array clustering analyses revealed (a) association between the xenograft and the originating clinical specimen, (b) pairing of androgen-sensitive lines with their CR sublines, (c) a distinction between adenocarcinoma and neuroendocrine phenotypes and (d) insignificant drift over a 2-5 year period of serial passage. Biomarker expression is quite heterogeneous and in most cases, protein expression correlated well with gene expression.

Importantly, 7 LuCaP models elicit an osteoblastic reaction in the bone, 5 models are PTEN negative, and 8 lines have the TMPRSS2:ERG fusion. The xenograft lines express different levels of AR with some expressing AR splice variants.

Heterogeneity was also observed in responses to therapy; prolonged survival (PS) following androgen ablation or docetaxel treatment ranged from 1 - 7 fold. Interestingly, LuCaP 86.2, expressing predominantly ARv567es, was among the least responsive to androgen ablation (PS 1.1) whereas it is one of the most responsive to docetaxel (PS &gt;4). Several novel anti-androgen therapies are currently under investigation as individual agents and in combination; heterogeneous responses are being observed. To explore mechanisms of resistance, we are also maintaining sublines that developed resistance to abiraterone and MDV-3100.

Conclusions: These LuCaP PCa xenograft lines are highly diverse and clinically relevant models to study PCa biology and to evaluate new treatment modalities. The diversity of phenotypes and responses to therapy most importantly suggests that misleading conclusions can be drawn from the use of only one or two models in preclinical evaluations.

Citation Format: Holly Nguyen, Eva Corey, Colm Morrissey, Peter Nelson, Xiaotun Zhang, Martine Roudier, Stephen Plymate, Lawrence True, Celestia Higano, Robert Montgomery, Paul Lange, Robert Vessella. The biological and molecular characterization of clinically relevant prostate cancer xenograft lines (LuCaP series), including responses to therapy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 305. doi:10.1158/1538-7445.AM2013-305

Treatment-induced damage to the tumor microenvironment promotes prostate cancer therapy resistance through WNT16B

Acquired resistance to anticancer treatments is a substantial barrier to reducing the morbidity and mortality that is attributable to malignant tumors. Components of tissue microenvironments are recognized to profoundly influence cellular phenotypes, including susceptibilities to toxic insults. Using a genome-wide analysis of transcriptional responses to genotoxic stress induced by cancer therapeutics, we identified a spectrum of secreted proteins derived from the tumor microenvironment that includes the Wnt family member wingless-type MMTV integration site family member 16B (WNT16B). We determined that WNT16B expression is regulated by nuclear factor of κ light polypeptide gene enhancer in B cells 1 (NF-κB) after DNA damage and subsequently signals in a paracrine manner to activate the canonical Wnt program in tumor cells. The expression of WNT16B in the prostate tumor microenvironment attenuated the effects of cytotoxic chemotherapy in vivo, promoting tumor cell survival and disease progression. These results delineate a mechanism by which genotoxic therapies given in a cyclical manner can enhance subsequent treatment resistance through cell nonautonomous effects that are contributed by the tumor microenvironment.

Lack of microsatellite instability in human prostate-cancer

DNA replication errors are especially frequent in repetitive DNA sequences, including microsatellites. Thus, microsatellites are sensitive indicators of the genetic instability observed in many types of human cancers, particularly colorectal cancer. We tested prostate carcinomas for the presence of microsatellite alleles not present in normal tissue from the same individuals. Analysis of 7 microsatellites in each of 30 patients revealed instability at only one microsatellite in one tumor. This level of microsatellite instability, considerably lower than that reported previously, may reflect differences in patient pools. We discuss the implications of the genetic stability of prostate cancers relative to other cancers.

Abstract C34: The biological and molecular characterization of 28 unique prostate cancer xenograft lines (LuCaP series), including responses to therapy

Introduction: Prostate cancer (PCa) is a heterogeneous disease which results in an unpredictable and wide range of responses to therapy. A significant limitation in unraveling the complexities of PCa and developing / evaluating novel therapeutic strategies is the lack of pre-clinical models that closely replicate the diversity of the disease seen in man. To overcome this limitation we have established over 2 dozen PCa xenograft lines (LuCaP series). This poster will provide a summary of the biological and molecular characterization of nearly all of these xenograft lines including their responses to therapy.

Methods: Characterization of the xenograft lines derived from primary PCa and PCa metastases includes: (a) basic histology, (b) serum PSA levels, (c) tumor doubling time, (d) expression of 38 biomarkers by immunohistology (IHC), (e) oligo array profiles, (f) expression of the androgen receptor (AR) and its splice variants, (g) bone response, and (h) response to therapy, i.e. androgen ablation, docetaxel and anti-IGF-1R.

Results: Of the 28 derived LuCaP xenograft lines, 24 are adenocarcinoma and 4 are neuroendocrine. Our results show that all lines histologically resemble the originating clinical specimen. Unsupervised gene expression array clustering analyses revealed (a) association between the xenograft and the originating clinical specimen, (b) pairing of androgen-sensitive lines with their castration-resistant offspring, (c) a distinction between adenocarcinoma and neuroendocrine phenotypes and (d) that gene expression profiles were not significantly altered by continuous passage in vivo for 2-8 years.

Importantly, seven of our models elicit an osteoblastic reaction in the bone, five models are PTEN negative, eight lines have the TMPRSS2:ERG fusion, and there are eight matched pairs of androgen-sensitive and castration-resistant xenografts.

As in the clinical scenario, the xenograft lines display considerable diversity. They express variable amounts of PSA (range from 0-1000 ng/ml/1 g), different levels of AR and express an AR splice variant after castration. IHC revealed considerable heterogeneity in all biomarkers evaluated. In most cases protein expression correlated well with gene expression.

Heterogeneity was also observed in responses to therapy; prolonged survival (PS) following androgen ablation or docetaxel each ranged from 1 - 7.3 fold. Interestingly, LuCaP 86.2, expressing predominantly ARv567es, was among the least responsive to androgen ablation (PS 1.1) whereas it is one of the most responsive to docetaxel (PS &gt;4). Several novel anti-androgen therapies are currently under investigation.

Conclusions: These 28 LuCaP PCa xenograft lines are highly diverse and clinically relevant models to study PCa biology and evaluate new treatment modalities. The diversity of phenotypes and responses to therapy most importantly suggests that misleading conclusions can be drawn from the use of only one or two PCa models in preclinical evaluations. Use of multiple models is extremely important in the evaluation of new therapeutic strategies, especially those targeting specific pathways.

Citation Format: Holly Nguyen, Martine Roudier, Lawrence True, Robert Vessella, Eva Corey, Colm Morrissey, Peter Nelson, Xiaotun Zhang, Stephen Plymate, Celestia Higano, Paul Lange. The biological and molecular characterization of 28 unique prostate cancer xenograft lines (LuCaP series), including responses to therapy [abstract]. In: Proceedings of the AACR Special Conference on Advances in Prostate Cancer Research; 2012 Feb 6-9; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(4 Suppl):Abstract nr C34.

Abstract 3242: The molecular and biological characterization of 25 unique prostate cancer xenograft lines, including response to therapy

Introduction: Prostate cancers (PCa) exhibit a wide range of molecular and biological profiles. In concert with this heterogeneity, there is a wide spectrum of responses to therapy. One of the significant limitations in unraveling the complexities of PCa and designing/evaluating novel therapeutic strategies has been the lack of pre-clinical models that closely replicate the diversity seen in man. To overcome this limitation we have developed 25 unique PCa xenograft lines (LuCaP series) where the initiating implants were derived from primary tumors, soft-tissue metastases and bone metastases. This presentation will provide details of a comprehensive molecular and biological characterization of these lines, including their responses to therapy.

Methods: Tumors were obtained either from radical prostatectomies or from our rapid autopsy program, which is designed specifically for the acquisition of metastatic foci. Tumor pieces were implanted into male, immune compromised mice. Characterization involves: (a) quantification of serum PSA levels, (b) basic histology, (c) tumor doubling time, (d) a panel of &gt;15 biomarkers assessed by immunohistochemistry, (e) gene expression array profiles, (f) chromosomal losses and gains, (g) expression of the TMPRSS2:ERG fusion gene, (h) presence of the androgen receptor (AR) and its splice variants, (i) bone remodeling perturbations associated with tumor growth in bone, and (j) response to therapy, including androgen ablation and docetaxel.

Results: Overall, 18% of the attempts to establish xenografts were successful resulting in 25 lines. As in the clinical scenario, these xenografts display a wide range of characterization profiles. While most are adenocarcinomas, 3 are neuroendocrine and all histologically resemble the originating clinical specimen. PSA serum levels can reach into the low thousands of ng/ml for a 1 g tumor. AR gene and protein expression is highly variable and &gt;50% of the lines express a constitutively active AR splice variant. The gene expression profiles show multiple clustering patterns that include a close association of the xenograft with the clinical specimen, pairing of androgen dependent lines with their castrate-resistant offspring and a distinction between adenocarcinoma and neuroendocrine histologies. Five of the lines are PTEN negative and 9 express the TMPRSS2:ERG gene fusion. The bone remodeling response ranges from osteoblastic to lytic. Responses to androgen ablation and docetaxel range from long duration to no response.

Conclusions: These 25 LuCaP PCa xenograft lines provide a highly diverse, yet clinically relevant, panel for the study of PCa biology. This diversity most importantly suggests that misleading conclusions can be drawn from use of only one or two PCa models. This is extremely important in the evaluation of new therapeutic strategies, especially those that target specific pathways.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3242.

Abstract 3302: Profiling prostate cancer metastases

Introduction: Prostate cancer (PCa) metastasizes to a number of sites, however, it has a propensity to metastasize to bone. There is considerable variation in sites of metastases, the phenotype of metastases, and bone response in PCa. Our objective was to detail the behavior of PCa metastases in a large cohort of patients who have died of PCa.

Methods: Tissue samples used in this study were obtained from seventy patients who had died from advanced PCa and who underwent a rapid autopsy, which was performed under the aegis of the Prostate Cancer Donor Program at the University of Washington. We evaluated the clinical history, sites of metastasis, pathology, biomarker expression and bone response for all 70 patients. We used laser capture microdissection to isolate mRNA from liver, lymph node and bone metastases and performed expression analyses on AgilentTM Oligo Arrays (n=32). Tissue microarrays were used to determine the number of neuroendocrine metastases, androgen receptor positivity, androgen-associated protein expression, and PCa proliferation rates (Ki-67) from 42 patients. Histomorphometry was used to evaluate bone response in ∼20 predetermined bone biopsy sites from 50 of the patients.

Results: PCa bone metastases occurred in 90% of our patients that died of PCa. Additionally, the majority of bone metastases were predominantly osteoblastic 71%, with 20% predominantly osteolytic and 9% with a mixed or no bone response. The predominant non-bone sites were lymph nodes, liver, lung and adrenal glands respectively. Seven of 42 patients had metastases with a neuroendocrine phenotype. Nuclear androgen receptor expression was high in bone and low in liver metastases and the correlation between nuclear AR and cytoplasmic PSA was 0.49. Proliferation rates were low in normal prostate increasing in Gleason 3 through 4, and higher in metastases. In a preliminary expression analysis we observed significantly higher expression of CD302, ZNF329, and TMEM79 in the PCa bone metastases compared to soft tissue metastases. Interestingly, bone histomorphometry revealed that the number of TRAcP positive osteoclasts was halved in bone cores from patients treated with bisphosphonates (n=459) compared to bone cores from non-bisphosphonate treated patients (n=284) (p=0.0003).

Conclusions: The heterogeneity of PCa metastases both within and between patients is a considerable obstacle in determining the appropriate treatment regime for each individual. Our data highlight these differences, while suggesting patients may be grouped into cohorts with consistent molecular signatures and clinical outcomes.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3302.

Linezolid in the treatment of multidrug-resistant tuberculosis

BACKGROUND

Linezolid is a new antibiotic with activity against Mycobacterium tuberculosis in vitro and in animal studies. Several small case series suggest that linezolid is poorly tolerated because of the side effects of anemia/thrombocytopenia and peripheral neuropathy. To characterize our clinical experience with linezolid, the California Department of Public Health Tuberculosis Control Branch's Multidrug-Resistant Tuberculosis (MDR-TB) Service reviewed cases in which the MDR-TB treatment regimens included linezolid therapy.

METHODS

Record review was performed for 30 patients treated with linezolid as part of an MDR-TB regimen. Data were collected on clinical and microbiological characteristics, linezolid tolerability, and treatment outcomes. The dosage of linezolid was 600 mg daily. Vitamin B6 at a dosage of 50-100 mg daily was used to mitigate hematologic toxicity.

RESULTS

During 2003-2007, 30 patients received linezolid for the treatment of MDR-TB. Patients had isolates resistant to a median of 5 drugs (range, 2-13 drugs). Of the 30 cases, 29 (97%) were pulmonary; of these 29, 21 (72%) had positive results of acid-fast bacilli smear, and 16 (55%) were cavitary. Culture conversion occurred in all pulmonary cases at a median of 7 weeks. At data censure (31 December 2008), 22 (73%) of 30 patients had successfully completed treatment. Five continued to receive treatment. There were no deaths. Three patients had a poor outcome, including 2 defaults and 1 treatment failure. Side effects occurred in 9 patients, including peripheral and optic neuropathy, anemia/thrombocytopenia, rash, and diarrhea. However, only 3 patients stopped linezolid treatment because of side effects.

CONCLUSIONS

Linezolid was well tolerated, had low rates of discontinuation, and may have efficacy in the treatment of MDR-TB.

Androgen receptor regulates a distinct transcription program in androgen-independent prostate cancer

The evolution of prostate cancer from an androgen-dependent state to one that is androgen-independent marks its lethal progression. The androgen receptor (AR) is essential in both, though its function in androgen-independent cancers is poorly understood. We have defined the direct AR-dependent target genes in both androgen-dependent and -independent cancer cells by generating AR-dependent gene expression profiles and AR cistromes. In contrast to what is found in androgen-dependent cells, AR selectively upregulates M-phase cell-cycle genes in androgen-independent cells, including UBE2C, a gene that inactivates the M-phase checkpoint. We find that epigenetic marks at the UBE2C enhancer, notably histone H3K4 methylation and FoxA1 transcription factor binding, are present in androgen-independent cells and direct AR-enhancer binding and UBE2C activation. Thus, the role of AR in androgen-independent cancer cells is not to direct the androgen-dependent gene expression program without androgen, but rather to execute a distinct program resulting in androgen-independent growth.