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Supplementary Figure S1. CyTOF analysis of biological samples from Ptenpc-/-Smad4pc-/- mice (Related to Figure 2). Supplementary Figure S2. Strategy used for MDSCs Isolation (Related to Figure 3). Supplementary Figure S3. Treatment scheme for Gr-1 antibody, peptibody, and Cxcr2 inhibitor SB225002. Supplementary Figure S4. IHC staining of Ki67, CD45, Vimentin, Smooth muscle actin (SMA) and Trichrome staining of mouse prostate tissues treated with IgG control or Gr1 antibody. Supplementary Figure S5. The top 10 differentially expressed genes in Ptenpc-/-Smad4pc-/- tumors as compared to Ptenpc-/- tumors, identified by microarray analysis (n=5). Figure S6. Top 10 activated oncogenic signatures identified by GSEA analysis in Ptenpc-/- Smad4pc-/- tumors as compared to Ptenpc-/- tumors (n=5). Figure S7. Clustering of primary prostate tumors from Wallace et al into MDSC-high and MDSC-low subtypes.

Overlapped genes between Genes upregulated in Ptenpc-/-Smad4pc-/- tumors as compared to Ptenpc-/- tumors ({greater than or equal to}2 fold) and genes upregulated in GFP+ tumors cells from Ptenpc-/-Smad4pc-/- mice as compared to Tomato+ cells ({greater than or equal to}4 fold).

Comparison of copy number changes in MDA PCa 150 PDXs

Ranked expression of genes in MDA PCa 146-10 vs MDA PCa 146-12

Purpose:Advances in prostate cancer lag behind other tumor types partly due to the paucity of models reflecting key milestones in prostate cancer progression. Therefore, we develop clinically relevant prostate cancer models.Experimental Design:Since 1996, we have generated clinically annotated patient-derived xenografts (PDXs; the MDA PCa PDX series) linked to specific phenotypes reflecting all aspects of clinical prostate cancer.Results:We studied two cell line–derived xenografts and the first 80 PDXs derived from 47 human prostate cancer donors. Of these, 47 PDXs derived from 22 donors are working models and can be expanded either as cell lines (MDA PCa 2a and 2b) or PDXs. The histopathologic, genomic, and molecular characteristics (androgen receptor, ERG, and PTEN loss) maintain fidelity with the human tumor and correlate with published findings. PDX growth response to mouse castration and targeted therapy illustrate their clinical utility. Comparative genomic hybridization and sequencing show significant differences in oncogenic pathways in pairs of PDXs derived from different areas of the same tumor. We also identified a recurrent focal deletion in an area that includes the speckle-type POZ protein-like (SPOPL) gene in PDXs derived from seven human donors of 28 studied (25%). SPOPL is a SPOP paralog, and SPOP mutations define a molecular subclass of prostate cancer. SPOPLdeletions are found in 7% of The Cancer Genome Atlas prostate cancers, which suggests that our cohort is a reliable platform for targeted drug development.Conclusions:The MDA PCa PDX series is a dynamic resource that captures the molecular landscape of prostate cancers progressing under novel treatments and enables optimization of prostate cancer–specific, marker-driven therapy.

Supplementary Methods

Legend of Supplementary Figures

Supplementary Results

Summary Background Taxane–platinum combinations have shown promising activity in metastatic castration-resistant prostate cancers in single-group clinical studies but not in randomised trials. Distinct biological subsets of the disease might derive the greatest benefit from the addition of platinum. We aimed to determine whether adding carboplatin to cabazitaxel would improve the outcomes of men with metastatic castration-resistant prostate cancer. Methods We did a phase 1–2, open label, randomised study at two centres in men with progressive metastatic castration-resistant prostate cancer. In phase 1, patients received intravenous cabazitaxel 20–25 mg/m2 and intravenous carboplatin area under the curve (AUC) 3–4 mg/mL per min every 21 days. The maximum tolerated dose was defined as the highest dose cohort studied in which one of six or fewer patients experienced a dose-limiting toxicity. In phase 2, patients were randomly assigned (1:1) centrally by a computerised algorithm to intravenous cabazitaxel 25 mg/m2 with or without intravenous carboplatin AUC 4 mg/mL per min. All patients received growth factor support and oral prednisone 10 mg daily. The primary endpoints were the maximum tolerated dose of the combination in phase 1 and investigator-assessed progression-free survival in phase 2. This trial is registered at ClinicalTrials.gov , number NCT01505868 . Findings Between Aug 17, 2012, and May 11, 2015, nine patients completed phase 1 as planned, and 160 were randomly assigned to cabazitaxel (n=79) or cabazitaxel plus carboplatin (n=81) in phase 2. During phase I, grade 3 adverse events were anaemia (n=2), fatigue (n=1), thrombocytopenia (n=1), hypomagnesaemia (n=1), diarrhoea (n=1), hypokalaemia (n=1), anorexia (n=1), and dehydration (n=1), and no grade 4 adverse events occurred. No dose-limiting toxicities were observed, therefore, a maximum tolerated dose of cabazitaxel of 25 mg/m2 and carboplatin of AUC 4 mg/mL per min was selected for phase 2. At a median follow-up of 31·0 months (IQR 20·5–37·1), the combination improved the median progression-free survival from 4·5 months (95% CI 3·5–5·7) to 7·3 months (95% CI 5·5–8·2; hazard ratio 0·69, 95% CI 0·50–0·95, p=0·018). In the phase 2 study, the most common grade 3–5 adverse events were fatigue (7 [9%] of 79 in the cabazitaxel group vs 16 [20%] of 81 in the combination group), anaemia (3 [4%] vs 19 [23%]), neutropenia (3 [4%] vs 13 [16%]), and thrombocytopenia (1 [1%] vs 11 [14%]). There were no treatment-related deaths. Interpretation Carboplatin added to cabazitaxel showed improved clinical efficacy compared with cabazitaxel alone for men with metastatic castration-resistant prostate cancer. Although adverse events were more common with the combination, the treatment was safe and generally well tolerated. Our data suggest that taxane–platinum combinations have a clinically beneficial role in advanced prostate cancer and a randomised phase 3 study is planned. Funding Sanofi Genzyme, University of Texas MD Anderson Cancer Center Prostate Cancer Moon Shot Program, Solon Scott III Prostate Cancer Research Fund, National Institutes of Health, and National Cancer Institute.

Purpose: Advances in prostate cancer lag behind other tumor types partly due to the paucity of models reflecting key milestones in prostate cancer progression. Therefore, we develop clinically relevant prostate cancer models. Experimental Design: Since 1996, we have generated clinically annotated patient-derived xenografts (PDXs; the MDA PCa PDX series) linked to specific phenotypes reflecting all aspects of clinical prostate cancer. Results: We studied two cell line–derived xenografts and the first 80 PDXs derived from 47 human prostate cancer donors. Of these, 47 PDXs derived from 22 donors are working models and can be expanded either as cell lines (MDA PCa 2a and 2b) or PDXs. The histopathologic, genomic, and molecular characteristics (androgen receptor, ERG, and PTEN loss) maintain fidelity with the human tumor and correlate with published findings. PDX growth response to mouse castration and targeted therapy illustrate their clinical utility. Comparative genomic hybridization and sequencing show significant differences in oncogenic pathways in pairs of PDXs derived from different areas of the same tumor. We also identified a recurrent focal deletion in an area that includes the speckle-type POZ protein-like (SPOPL) gene in PDXs derived from seven human donors of 28 studied (25%). SPOPL is a SPOP paralog, and SPOP mutations define a molecular subclass of prostate cancer. SPOPLdeletions are found in 7% of The Cancer Genome Atlas prostate cancers, which suggests that our cohort is a reliable platform for targeted drug development. Conclusions: The MDA PCa PDX series is a dynamic resource that captures the molecular landscape of prostate cancers progressing under novel treatments and enables optimization of prostate cancer–specific, marker-driven therapy.

To evaluate the pathologic features after radical prostatectomy to determine if the length of positive surgical margin (PSM) and the highest Gleason grade within the tumor at the PSM could risk stratify patients for biochemical recurrence (BCR). We performed a retrospective, matched, cohort study to identify patients with pathologically organ-confined (pT2) tumors and negative nodes (pN0/Nx), receiving no adjuvant therapy. Specimens underwent single pathologist review. BCR-free survival was estimated using the Kaplan–Meier method and compared between subgroups using two-sided log-rank test. Using Classification and Regression Tree analysis (CART), we identified an optimal cutoff for the PSM length which differentiated risk for BCR. Cox proportional hazards regression models were fit to assess the association between variables and BCR-free survival. Two-hundred PSM patients were matched to 200 patients with negative surgical margins (NSM). Median follow-up was 64 months. 5 year BCR-free survival was 90% (95% CI 84–97%) in the NSM group and 70% (95% CI 63–79%) in the PSM group. There was an increased risk of BCR with any PSM. Multivariable analysis demonstrated an association with length of PSM ( > 1 mm vs. ≤ 1 mm, HR 2.29; 95% CI 1.2–4.5) and having a highest Gleason grade of the cancer focus at the margin ≥ 4 (HR 6.8; 95% CI 1.6–29). We demonstrated that patients with pathologic T2 tumors with PSM > 1 mm or a Gleason grade of tumor focus at the margin ≥ 4 are at elevated risk for BCR. However, this study suggests that patients with pT2 tumors with positive surgical margins have a relatively low risk of biochemical recurrence and adjuvant radiation may be over treating this sub population. The subsets at greatest risk for BCR may benefit from more frequent PSA monitoring to direct salvage therapies.

White adipose tissue (WAT) overgrowth in obesity is linked with increased aggressiveness of certain cancers. Adipose stromal cells (ASCs) can become mobilized from WAT, recruited by tumours and promote cancer progression. Mechanisms underlying ASC trafficking are unclear. Here we demonstrate that chemokines CXCL1 and CXCL8 chemoattract ASC by signalling through their receptors, CXCR1 and CXCR2, in cell culture models. We further show that obese patients with prostate cancer have increased epithelial CXCL1 expression. Concomitantly, we observe that cells with ASC phenotype are mobilized and infiltrate tumours in obese patients. Using mouse models, we show that the CXCL1 chemokine gradient is required for the obesity-dependent tumour ASC recruitment, vascularization and tumour growth promotion. We demonstrate that αSMA expression in ASCs is induced by chemokine signalling and mediates the stimulatory effects of ASCs on endothelial cells. Our data suggest that ASC recruitment to tumours, driven by CXCL1 and CXCL8, promotes prostate cancer progression., Adipose stromal cells (ASC) have been shown to migrate to tumours and promote tumour growth. Using animal models and human tissue samples, the authors show here that ASC recruitment to prostate cancers is mediated by the chemokine CXCL1, which is secreted from tumour cells, and acts on CXCR1 on ASCs.

Purpose: Morphologically heterogeneous prostate cancers that behave clinically like small-cell prostate cancers (SCPC) share their chemotherapy responsiveness. We asked whether these clinically defined, morphologically diverse, “aggressive variant prostate cancer (AVPC)” also share molecular features with SCPC. Experimental Design: Fifty-nine prostate cancer samples from 40 clinical trial participants meeting AVPC criteria, and 8 patient-tumor derived xenografts (PDX) from 6 of them, were stained for markers aberrantly expressed in SCPC. DNA from 36 and 8 PDX was analyzed by Oncoscan for copy number gains (CNG) and losses (CNL). We used the AVPC PDX to expand observations and referenced publicly available datasets to arrive at a candidate molecular signature for the AVPC. Results: Irrespective of morphology, Ki67 and Tp53 stained ≥10% cells in 80% and 41% of samples, respectively. RB1 stained Conclusions: Clinically defined AVPC share molecular features with SCPC and are characterized by combined alterations in RB1, Tp53, and/or PTEN. Clin Cancer Res; 22(6); 1520–30. ©2015 AACR.

The signaling mechanisms between prostate cancer cells and infiltrating immune cells may illuminate novel therapeutic approaches. Here, utilizing a prostate adenocarcinoma model driven by loss of Pten and Smad4, we identify polymorphonuclear myeloid-derived suppressor cells (MDSC) as the major infiltrating immune cell type, and depletion of MDSCs blocks progression. Employing a novel dual reporter prostate cancer model, epithelial and stromal transcriptomic profiling identified CXCL5 as a cancer-secreted chemokine to attract CXCR2-expressing MDSCs, and, correspondingly, pharmacologic inhibition of CXCR2 impeded tumor progression. Integrated analyses identified hyperactivated Hippo–YAP signaling in driving CXCL5 upregulation in cancer cells through the YAP–TEAD complex and promoting MDSC recruitment. Clinicopathologic studies reveal upregulation and activation of YAP1 in a subset of human prostate tumors, and the YAP1 signature is enriched in primary prostate tumor samples with stronger expression of MDSC-relevant genes. Together, YAP-driven MDSC recruitment via heterotypic CXCL5–CXCR2 signaling reveals an effective therapeutic strategy for advanced prostate cancer. Significance: We demonstrate a critical role of MDSCs in prostate tumor progression and discover a cancer cell nonautonomous function of the Hippo–YAP pathway in regulation of CXCL5, a ligand for CXCR2-expressing MDSCs. Pharmacologic elimination of MDSCs or blocking the heterotypic CXCL5–CXCR2 signaling circuit elicits robust antitumor responses and prolongs survival. Cancer Discov; 6(1); 80–95. ©2015 AACR. This article is highlighted in the In This Issue feature, p. 1

BACKGROUND: Prostate cancer patients who have a detectable prostate-specific antigen (PSA) postprostatectomy may harbor pre-existing metastatic disease. To our knowledge, none of the commercially available genomic biomarkers have been investigated in such men. OBJECTIVE: To evaluate if a 22-gene genomic classifier can independently predict development of metastasis in men with PSA persistence postoperatively. DESIGN, SETTING, AND PARTICIPANTS: A multi-institutional study of 477 men who underwent radical prostatectomy (RP) between 1990 and 2015 from three academic centers. Patients were categorized as detectable PSA (n = 150) or undetectable (n = 327) based on post-RP PSA nadir ≥0.1 ng/ml. OUTCOME MEASUREMENTS AND STATISITICAL ANALYSIS: Cumulative incidence curves for metastasis were constructed using Fine-Gray competing risks analysis. Penalized Cox univariable and multivariable (MVA) proportional hazards models were performed to evaluate the association of the genomic classifier with metastasis. RESULTS AND LIMITATIONS: The median follow-up for censored patients was 57 mo. The median time from RP to first postoperative PSA was 1.4 mo. Detectable PSA patients were more likely to have higher adverse pathologic features compared with undetectable PSA patients. On MVA, only genomic high-risk (hazard ratio [HR]: 5.95, 95% confidence interval [CI]: 2.02–19.41, p = 0.001), detectable PSA (HR: 4.26, 95% CI: 1.16–21.8, p = 0.03), and lymph node invasion (HR: 12.2, 95% CI: 2.46–70.7, p = 0.003) remained prognostic factors for metastasis. Among detectable PSA patients, the 5-yr metastasis rate was 0.90% for genomic low/intermediate and 18% for genomic high risk (p < 0.001). Genomic high risk remained independently prognostic on MVA (HR: 5.61, 95% CI: 1.48–22.7, p = 0.01) among detectable PSA patients. C-index for Cancer of the Prostate Risk Assessment Postsurgical score, Gandaglia nomogram, and the genomic classifier plus either Cancer of the Prostate Risk Assessment Postsurgical score or Gandaglia were 0.69, 0.68, and 0.82 or 0.81, respectively. Sample size was a limitation. CONCLUSIONS: Despite patients with a detectable PSA harboring significantly higher rates of aggressive clinicopathologic features, Decipher independently predicts for metastasis. Prospective validation of these findings is warranted and will be collected as part of the ongoing randomized trial NRG GU-002. PATIENT SUMMARY: Decipher independently predicted metastasis for patients with detectable prostate-specific antigen after prostatectomy.

Cytochrome P450 17α-hydroxylase/17,20-lyase (CYP17A1) is a validated treatment target for the treatment of metastatic castration-resistant prostate cancer (CRPC). Abiraterone acetate (AA) inhibits both 17α-hydroxylase (hydroxylase) and 17,20-lyase (lyase) reactions catalyzed by CYP17A1 and thus depletes androgen biosynthesis. However, coadministration of prednisone is required to suppress the mineralocorticoid excess and cortisol depletion that result from hydroxylase inhibition. VT-464, a nonsteroidal small molecule, selectively inhibits CYP17A1 lyase and therefore does not require prednisone supplementation. Administration of VT-464 in a metastatic CRPC patient presenting with high tumoral expression of both androgen receptor (AR) and CYP17A1, showed significant reduction in the level of both dehydroepiandrosterone (DHEA) and serum PSA. Treatment of a CRPC patient-derived xenograft, MDA-PCa-133 expressing H874Y AR mutant with VT-464, reduced the increase in tumor volume in castrate male mice more than twice as much as the vehicle (P

Background In the Prostate Cancer Prevention Trial, finasteride selectively suppressed low-grade prostate cancer and significantly reduced the incidence of prostate cancer in men treated with finasteride compared with placebo. However, an apparent increase in high-grade disease was also observed among men randomized to finasteride. We aimed to determine why and hypothesized that there is a grade-dependent response to finasteride. Methods From 2007 to 2012, we randomized dynamically by intranet-accessible software 183 men with localized prostate cancer to receive 5 mg finasteride or placebo daily in a double-blind study during the 4–6 weeks preceding prostatectomy. As the primary end point, the expression of a predefined molecular signature (ERβ, UBE2C, SRD5A2, and VEGF) differentiating high- and low-grade tumors in Gleason grade (GG) 3 areas of finasteride-exposed tumors from those in GG3 areas of placebo-exposed tumors, adjusted for Gleason score (GS) at prostatectomy, was compared. We also determined androgen receptor (AR) levels, Ki-67, and cleaved caspase 3 to evaluate the effects of finasteride on the expression of its downstream target, cell proliferation, and apoptosis, respectively. The expression of these markers was also compared across grades between and within treatment groups. Logistic regression was used to assess the expression of markers. Findings We found that the predetermined molecular signature did not distinguish GG3 from GG4 areas in the placebo group. However, AR expression was significantly lower in the GG4 areas of the finasteride group than in those of the placebo group. Within the finasteride group, AR expression was also lower in GG4 than in GG3 areas, but not significantly. Expression of cleaved caspase 3 was significantly increased in both GG3 and GG4 areas in the finasteride group compared to the placebo group, although it was lower in GG4 than in GG3 areas in both groups. Interpretation We showed that finasteride's effect on apoptosis and AR expression is tumor grade dependent after short-term intervention. This may explain finasteride's selective suppression of low-grade tumors observed in the PCPT., Highlights • We studied 183 men with early prostate cancer receiving 5 mg finasteride or placebo daily for 4–6 weeks preprostatectomy. • Expression of androgen receptor and cleaved caspase 3 was dependent on tumor grade. • Finasteride's demonstrated effects in tissue may explain earlier seminal findings in the Prostate Cancer Prevention Trial. This study advances the fields of prostate cancer biology and prostate cancer treatment because it demonstrates effects of finasteride in prostatectomy tissues that offer an explanation for the mixed results of the 18,882-subject randomized and controlled Prostate Cancer Prevention Trial (PCPT). Initial results showing a 25% reduction in prevalence in prostate cancer in men in the finasteride group while revealing an apparent increase in high-grade disease among those in the same group suggested a grade-associated response to finasteride. The results of this present study indicate finasteride's effects are grade dependent, which may explain the split findings of the PCPT.

Meeting abstracts Myeloid-derived suppressor cells (MDSCs) represent a phenotypically heterogeneous population of immature myeloid cells that play a tumor-promoting role by maintaining a state of immunological anergy and tolerance. Similar to other solid tumor types, Prostate cancer (PCa) is

5013 Background: The AVPC are a subset of prostate cancers that share the clinical, therapy response and molecular profiles of the small cell prostate carcinomas, a histological variant of the disease that responds poorly to androgen receptor directed therapies. The AVPC are characterized by a molecular signature of combined tumor suppressor defects (≥ 2 alterations in Tp53, RB1 and/or PTEN by immunohistochemistry or genomic analyses). We conducted a randomized phase II study of cabazitaxel (CAB) plus or minus carboplatin (CARB) in men with CRPC and asked whether the AVPC-MS predicted for platinum benefit. Methods: 160 men with metastatic CRPC were randomized 1:1 to receive IV CAB (25 mg/m2) or CAB/CARB (25 mg/m2; AUC4) Q21 days with growth factor support until disease progression, unacceptable toxicity or for up to 10 cycles. Imaging occurred every 2 cycles. The primary endpoint was progression free survival (PFS). 73 tumor samples obtained within 1 year of registration from 65 of the 160 patients (pts) were stained for Tp53, RB1, PTEN, AR-N terminus, AR-C terminus and Ki67. DNA of sufficient quantity for sequencing was extracted from 27 tumors and 70 plasma samples. Results: At a median follow up of 21.6 months (mo), median PFS (mPFS) in the overall population (n = 160) is 4.6 mo (95%CI 3.5, 5.8) with CAB vs 7.4 mo (95% CI 5.6, 8.3) with CAB/CARB (p = 0.004). Men with AVPC-MS-positive tumors had a mPFS of 4.5 mo (95%CI 1.5, NA) with CAB [n = 9] vs 8.0mo (95%CI 6.11-9.7) with CAB/CARB [n = 23] (p = 0.0036) whereas men with AVPC-MS-negative tumors had a mPFS of 6.8mo (95%CI 5.2, NA) with CAB [n = 12] vs 5.4mo (95%CI 3.72, NA) with CAB/CARB [n = 12] (p = 0.1445). Analysis of plasma DNA samples is ongoing and will be presented at the meeting. Conclusions: The AVPC-MS identifies a subset of men platinum-sensitive CRPC tumors. These findings should serve as the foundation for a therapeutically relevant classification of prostate cancer. Clinical trial information: NCT01505868.

Bone is the most common site of prostate cancer (PCa) progression to a therapy-resistant, lethal phenotype. We found that blockade of fibroblast growth factor receptors (FGFRs) with the receptor tyrosine kinase inhibitor dovitinib has clinical activity in a subset of men with castration-resistant PCa and bone metastases. Our integrated analyses suggest that FGF signaling mediates a positive feedback loop between PCa cells and bone cells and that blockade of FGFR1 in osteoblasts partially mediates the antitumor activity of dovitinib by improving bone quality and by blocking PCa cell-bone cell interaction. These findings account for clinical observations such as reductions in lesion size and intensity on bone scans, lymph node size, and tumor-specific symptoms without proportional declines in serum prostate-specific antigen concentration. Our findings suggest that targeting FGFR has therapeutic activity in advanced PCa and provide direction for the development of therapies with FGFR inhibitors.

Background Human T-lymphotropic virus (HTLV)-1-associated infective dermatitis (ID) is a rare severe chronic eczema, considered as a harbinger for the development of cutaneous adult T-cell leukemia/lymphoma (ATLL) and/or HTLV-1-associated myelopathy (HAM)/tropical spastic paraparesis (TSP). The pathogenesis of ID remains unclear. High numbers of peripheral blood CD4+ CD25+ FoxP3+ regulatory T cells (Tregs) have been reported in ATLL and HAM/TSP. Objective To investigate the status of Tregs, unknown to date, and the histopathological features of ID. Methods We studied 16 skin biopsies from 15 Peruvian adults and children with ID by immunohistochemistry. Results Histopathological patterns were seborrheic dermatitis-like and lichenoid. Intraepidermal lymphocytes were conspicuous. The infiltrate was composed of a CD3+ T cell infiltrate with a predominance of CD8+ over CD4+ cells. CD4+ CD25+ FoxP3+ Tregs were rare and their numbers were significantly lower than those reported in other inflammatory dermatoses. Conclusion Tregs have an essential role in maintaining immune homeostasis of skin. Treg dysregulation ends in severe clinical manifestations. The clinical presentation of ID, with lesions resembling those seen in patients with atopic dermatitis and with mutations in the FoxP3 gene, is in agreement with a common Treg-deficient skin environment in these disorders, possibly secondary to HTLV-1 infection.

Androgen deprivation is the standard treatment for advanced prostate cancer (PCa), but most patients ultimately develop resistance and tumor recurrence. We found that MYB is transcriptionally activated by androgen deprivation therapy or genetic silencing of the androgen receptor (AR). MYB silencing inhibited PCa growth in culture and xenografts in mice. Microarray data revealed that c-Myb and AR shared a subset of target genes that encode DNA damage response (DDR) proteins, suggesting that c-Myb may supplant AR as the dominant regulator of their common DDR target genes in AR inhibition-resistant or AR-negative PCa. Gene signatures including AR, MYB, and their common DDR-associated target genes positively correlated with metastasis, castration resistance, tumor recurrence, and decreased survival in PCa patients. In culture and in xenograft-bearing mice, a combination strategy involving the knockdown of MYB, BRCA1, or TOPBP1 or the abrogation of cell cycle checkpoint arrest with AZD7762, an inhibitor of the checkpoint kinase Chk1, increased the cytotoxicity of the poly[adenosine 5'-diphosphate (ADP)-ribose] polymerase (PARP) inhibitor olaparib in PCa cells. Our results reveal new mechanism-based therapeutic approaches for PCa by targeting PARP and the DDR pathway involving c-Myb, TopBP1, ataxia telangiectasia mutated- and Rad3-related (ATR), and Chk1.

Patients with metastatic prostate cancer (PCa) have effective therapy options, but none of them are curative. Thus, their mortality rates are persistently high. Essential to furthering our progress in PCa research and therapy development is a spectrum of models that reflect the heterogeneity of the disease at each tumor site as well as the different histological variants of PCa (e.g., adenocarcinoma, small cell carcinoma). To address this challenge, we developed a strategy to establish PCa patient-derived xenografts (PDXs), using PCa tissue specimens taken from PCa sites demonstrating clinical progression. This approach provided a diverse repository of PDXs that can be linked prospectively with clinical progression and led to the identification of clinically relevant therapy targets and have proven valuable for testing drugs. We studied the first 50 PDXs developed under our program to a) define the histopathological features of paired human PCa and corresponding PDXs applying the clinically defined morphological characterization groupings of human cancer to the PDX tumors; b) assess the expression of genes known to play roles in PCa pathogenesis (e.g., androgen receptor, PTEN, ETS gene fusions) in PDXs and the human tumors of origin using immunohistochemistry and fluorescence in situ hybridization and c) perform array comparative genomic hybridization to 42 PDXs. We found that the histopathological and molecular pattern of these PDXs maintain the fidelity with the human tumor of origin. Furthermore, of the 50 cases studied, 32 (64%) were adenocarcinomas, and 16 (32%) were small cell carcinomas, poorly differentiated neuroendocrine carcinomas or mixed adenocarcinoma/ small cell carcinomas. In our cohort, we also have one sarcomatoid tumor and one ductal adenocarcinoma. Of the 32 adenocarcinomas in this cohort, 26 were AR-positive (81%), and 11 of the 27 AR-positive adenocarcinomas (41%) had aberrant expression of genes frequently involved in recurrent rearrangement (e.g., ERG, ETV1, ETV5). Also, SCCs and poorly differentiated neuroendocrine carcinomas did not express AR and were negative for ERG. This distribution recapitulates that of human PCa in the general population. Comparative genomic hybridization demonstrated gains and losses previously reported in PCa with a defined cluster of genomic aberrations. Significant differences in oncogenic pathways activation in pairs of PDXs derived from different areas of the same tumor suggesting divergent cellular progression. Finally, using this platform, we identified a focal deletion of speckle-type POZ protein-like (SPOPL) gene in 7/28 PDX. SPOPL is a MATH-BTB protein that shares an overall 85% sequence identity with SPOP (a SPOPL paralog). SPOP was recently reported to be mutated in about 8% of PCa and to define a molecular subclass of PCa. No mutations were found in SPOP in our cohort. In support of our findings, deletions on SPOPL were also found in about 7% of the PCa in TCGA data suggesting that our cohort is a reliable platform for discovery. In conclusion, we have developed a dynamic repository of clinically annotated samples that can be used as a discovery platform. Furthermore, these clinically annotated samples can be linked prospectively to clinical progression/response to therapy and thus will help define therapeutic targets for subpopulations of men and to identify likely responders to previous and upcoming therapies. Citation Format: Nallasivam Palanisamy, Jun Yang, Xinhai Wan, Elsa M. li Ning Tapia, John C. Araujo, Eleni Efstathiou, Estefania Labanca, Louis Pisters, Ana Aparicio, Ritu Bhalla, Scott Tomlins, Lakshmi P. Kunju, Arul Chinnaiyan, Christopher J. Logothetis, Patricia Troncoso, Nora M. Navone. Analyses of a prostate cancer patient-derived xenografts series, a resource for translational research. [abstract]. In: Proceedings of the AACR Special Conference: Patient-Derived Cancer Models: Present and Future Applications from Basic Science to the Clinic; Feb 11-14, 2016; New Orleans, LA. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(16_Suppl):Abstract nr A03.

5002Background: AA added to medical castration augments cytoreduction in LHRPC though wide range of persistent cancer is observed. To build on these findings we conducted a study examining AA+ LHRH...

5020Background: Clinically defined AVPC is associated with platinum-sensitivity and a molecular profile of combined (≥2) alterations in PTEN, Tp53 and/or RB1 (Aparicio et al. Clin Cancer Res 2013;1...

5055 Background: AVPCa shares clinical features with small cell carcinoma (SCC) such as resistance to androgen signaling inhibition and frequent visceral metastases. A prospective clinical trial of...

5005 Background: Biological heterogeneity may have important implications for development of novel therapeutic approaches for LHRPC. This study examined clinical and biological heterogeneity of res...

149 Background: Unusually aggressive PC behavior is linked to small cell carcinoma (SCC) morphology. We observed SCC clinical features in association with morphologically heterogeneous PC and, in a prospective clinical trial (NCT00514540), also with chemotherapy responsiveness. Our previous studies in patient derived xenografts (PDX) revealed a distinct molecular profile for SCC. Here we sought to support the hypothesis that clinically defined aggressive variant PCs also share relevant biology with SCC. Methods: 59 PC samples, and 8 PDX, from 42 men registered to NCT00514540 were stained for RB, p53, AR, NKX3-1, ASCL1, AURKA, UBE2C and Ki67. Labeling indices (LI) were calculated as the ratio of positive epithelial cells to total of epithelial cells, at 200x. We determined copy number alterations (CNA) by Onco Scan® in 36 of 59 samples and 8 PDX lines. We used Western Blot and qRT-PCR to expand pathway analyses and their associations in PDX models. Results: Donor patients were similar to non-donor patients except for higher ECOG PS and LDH values. Strong positive correlations between nuclear AR (AR-N) and NKX3.1, AR-N and RB, AR-N and nuclear AURKA (AURKA-N), NKX3.1 and RB, p53 and nuclear UBE2C (UBE2C-N), Ki67 and UBE2C-N, Ki67 and cytoplasmic UBE2C (UBE2C-C) as well as a strong negative correlation between NKX3.1 and Ki 67 were observed. Frequent copy number losses were found for PTEN (largely gene-specific) and RB1 (often associated with regional-CNA). Gene-specific AURKA amplifications were not observed. Only RB1 CNA showed a positive correlation with its LI. Samples were segregated by quantity of CNA. PDX models shared these features and showed that only AR-negative tumors expressed pro-neural transcription factors, albeit heterogeneously. Conclusions: Our results support the hypothesis that clinically defined aggressive variant PC (including SCC and non-SCC morphologies) are characterized by frequent Rb, p53 and PTEN alterations, aberrant expression of mitotic, neural development and AR-signaling pathways, and high rates of CNA. Ongoing studies will confirm whether these molecular features distinguish this variant from the more common bone-homing, bone-forming, AR-driven adenocarcinomas of the prostate.

Castrate-resistant progression and bone metastases (BM) are hallmarks of advanced prostate cancer (PCa) for which there is no definitive cure. We previously reported that human PCa BM highly express fibroblast growth factor (FGF)-9 (J Clin Invest. 2008;118:2697). We now discovered that human PCa xenografts growing in the bone of mice induce bone cells to express components of the FGF/FGF receptor (FGFR) complex, Fgfr1, Fgfr2 and Fgf-2, as assessed by mouse-specific RT-PCR in bone bearing MDA PCa 118b tumors and in the contralateral bone (P20 weeks in a subset of patients (∼25%). Dovitinib inhibits vascular endothelial growth factor receptors (VEGFRs) 1-3, with IC50s (∼10 nM) similar to those of FGFR1-3. To assess the relative antitumor activity of FGFR blockade (with respect to VEGFR), we tested a TKI, AZD4547 (AstraZeneca), which inhibits FGFR1-3 (IC50s Citation Format: Xinhai Wan, Paul Corn, Jun Yang, Eleni Efstathiou, Elsa M. Li Ning Tapia, Fen Wang, Wallace McKeehan, Christopher Logothetis, Patricia Troncoso, Nora M. Navone. Fibroblast growth factor receptor blockade in prostate cancer bone metastases. [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 2436. doi:10.1158/1538-7445.AM2013-2436

Background: The Prostate Cancer Prevention Trial (PCPT) showed a relative reduction of 24.8% in cumulative incidence of prostate cancer (PC) in finasteride-treated men (18.4 v 24.4%; p Methods: This 4-site presurgical trial was in men with clinically organ-confined PC (cT1c/T2; GS 6 or 7; prostate-specific antigen [PSA] Results: In all, 210 patients consented, 204 were randomized, 183 were evaluable for detailed pathologic outcomes, and 163 were evaluable for PSA and hormone levels. Median age was 60 (45-73) yr. Median treatment time was 28 (10-43) days. Median prostate total tumor volume (TV) was 0.9 (0-10.4) cc, and peripheral zone TV, 0.6 (0-9.3) cc. Biopsy (Bx) GS, GS upgrade between Bx and RP, specimen GS/GG, total cancer foci, zonal origin of dominant cancer, and median total and PZ TV were similar in the 2 treatment arms (A v B). Post-treatment, median PSA was significantly lower (3.2 v 5.2 ng/mL; p Conclusions: No significant difference in GS distribution was observed between the two groups after short-term exposure to finasteride or placebo. Modulation of PSA, T, and DHT levels occurred in a statistically significant uneven distribution by study arm. Molecular signature characterization has been completed, and the planned analysis of associations is under way. The findings are expected to provide insight into the reported grade effect attributed to finasteride. (This work was supported in part by NCI contract N01-CN-35159.) Citation Format: Jeri Kim, John W. Davis, Eric A. Klein, Cristina Magi-Galluzzi, Yair Lotan, John F. Ward, Louis L. Pisters, Joseph W. Basler, Curtis A. Pettaway, Elsa M. Li Ning Tapia, Xuemei Wang, Kim-Anh Do, Jack Lee, Lana A. Vornik, Joe Tangrea, Howard L. Parnes, Scott M. Lippman, Ian M. Thompson, Powel H. Brown, Patricia Troncoso, Christopher J. Logothetis. A double-blind randomized controlled multisite trial evaluating tissue effects of preoperative finasteride in clinically organ-confined prostate cancer: Pathologic outcomes. [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 LB-195. doi:10.1158/1538-7445.AM2013-LB-195

58 Background: Cabozantinib (cabo) is a multi-TKI against c-Met and VEGFR2. Cabo elicits striking changes in bone scans (BS), reductions in soft-tissue mets, and improves bone pain in mCRPC. This unique response is unlinked from PSA and suggests that targets of Cabo reside in the bone microenvironment. To explore the underlying mechanisms of Cabo activity, we examined changes in soluble c-Met, angiogenic factors, bone specific alkaline phosphatase (BAP), and tumor specific c-Met signaling in men on Cabo. Methods: A phase II cohort of docetaxel pretreated men with mCRPC received Cabo. Response was assessed q6 wks by BS and CT scan. Blood and trans-iliac bone marrow biopsies (BMs) were collected pretreatment and at wk 6. Soluble c-Met was measured by ELISA, angiogenic factors by multiplex immunoassay, and tumor c-Met/phospho c-Met expression by IHC. Results: 21 patients with bony mets were evaluated; 38% also had soft tissue mets. 13/21 (62%) pts experienced an improvement (PRs + CRs) in BS and 2/8 (25%) achieved a PR in soft tissue mets. 12/20 (60%) pts had reductions in BAP on therapy (median reduction 48.5%). VEGFR2 levels decreased in response to therapy (p5% tumor involvement (median 80%) were evaluable for 10 patients, 9 of whom also had a 6 wk BM. High intensity, tumor-specific expression of c-Met was detectable in 8/10 (80%) of pretreatment tumors (median involvement 60%) and increased in 4/9 (45%) pts at 6 wks (median increase 30%). Activated phospho c-Met was detectable in 9/10 (90%) of pretreatment tumors (median involvement 80%) and decreased in 5/9 (56%) pts (median reduction 30%) at 6 wks. Conclusions: The results of our study suggest that changes in soluble markers of c-Met, bone turnover, and angiogenesis are linked to Cabo activity. Analyses of BMs demonstrate high c-Met activation in pretreatment mets and suggest Cabo-mediated inhibition at 6 wks. These data support the hypothesis that c-Met contributes to “driver” signaling networks in mCRPC and suggest that biomarkers of stromal cell function should be prioritized for further study.