Genomic Hallmarks and Structural Variation in Metastatic Prostate Cancer.

While mutations affecting protein-coding regions have been examined across many cancers, structural variants at the genome-wide level are still poorly defined. Through integrative deep whole-genome and -transcriptome analysis of 101 castration-resistant prostate cancer metastases (109X tumor/38X normal coverage), we identified structural variants altering critical regulators of tumorigenesis and progression not detectable by exome approaches. Notably, we observed amplification of an intergenic enhancer region 624 kb upstream of the androgen receptor (AR) in 81% of patients, correlating with increased AR expression. Tandem duplication hotspots also occur near MYC, in lncRNAs associated with post-translational MYC regulation. Classes of structural variations were linked to distinct DNA repair deficiencies, suggesting their etiology, including associations of CDK12 mutation with tandem duplications, TP53 inactivation with inverted rearrangements and chromothripsis, and BRCA2 inactivation with deletions. Together, these observations provide a comprehensive view of how structural variations affect critical regulators in metastatic prostate cancer.

Transcriptional profiling identifies an androgen receptor activity-low, stemness program associated with enzalutamide resistance.

The androgen receptor (AR) antagonist enzalutamide is one of the principal treatments for men with castration-resistant prostate cancer (CRPC). However, not all patients respond, and resistance mechanisms are largely unknown. We hypothesized that genomic and transcriptional features from metastatic CRPC biopsies prior to treatment would be predictive of de novo treatment resistance. To this end, we conducted a phase II trial of enzalutamide treatment (160 mg/d) in 36 men with metastatic CRPC. Thirty-four patients were evaluable for the primary end point of a prostate-specific antigen (PSA)50 response (PSA decline ≥50% at 12 wk vs. baseline). Nine patients were classified as nonresponders (PSA decline <50%), and 25 patients were classified as responders (PSA decline ≥50%). Failure to achieve a PSA50 was associated with shorter progression-free survival, time on treatment, and overall survival, demonstrating PSA50's utility. Targeted DNA-sequencing was performed on 26 of 36 biopsies, and RNA-sequencing was performed on 25 of 36 biopsies that contained sufficient material. Using computational methods, we measured AR transcriptional function and performed gene set enrichment analysis (GSEA) to identify pathways whose activity state correlated with de novo resistance. TP53 gene alterations were more common in nonresponders, although this did not reach statistical significance (P = 0.055). AR gene alterations and AR expression were similar between groups. Importantly, however, transcriptional measurements demonstrated that specific gene sets-including those linked to low AR transcriptional activity and a stemness program-were activated in nonresponders. Our results suggest that patients whose tumors harbor this program should be considered for clinical trials testing rational agents to overcome de novo enzalutamide resistance.

DNA Repair Gene Alterations and PARP Inhibitor Response in Patients With Metastatic Castration-Resistant Prostate Cancer.

Background: PARP inhibition is a promising therapeutic strategy for the treatment of men with metastatic castration-resistant prostate cancer whose tumors harbor homologous recombination DNA repair gene alterations. However, questions remain for many practicing clinicians about which patients are ideally suited for PARP inhibitor treatment. This report details our institutional experience using PARP inhibitor therapy in patients whose tumors harbored specific DNA repair gene alterations. Patients and Methods: We performed a retrospective chart review to identify patients at Oregon Health & Science University who were treated with PARP inhibition. We identified 8 patients and determined the impact of the specific DNA repair gene alterations on tumor response and time on treatment with PARP inhibition. Results: A number of DNA repair gene alterations were identified. Three patients had pathogenic BRCA2 mutations and one had a BRCA2 mutation of uncertain significance. Conversely, the 4 other patients' tumors harbored alterations in other DNA repair genes, none of which were clearly pathogenic. A statistically significant difference in benefit was seen between patients whose tumors harbored BRCA2 gene alterations and those whose tumors did not, as measured by >50% decline in prostate-specific antigen levels (100% vs 0%; P=.03) and duration on therapy (31.4 vs 6.4 weeks; P=.03). Conclusions: Our results demonstrate that not all DNA repair alterations are equally predictive of PARP inhibitor response. Importantly, all responding patients had tumors harboring BRCA2 DNA repair alterations, including one without a known pathogenic mutation. Conversely, among the 4 nonresponders, several DNA repair alterations in genes other than BRCA2 were identified that were not clearly pathogenic. This demonstrates the need to carefully examine the functional relevance of the DNA repair alterations identified, especially in genes other than BRCA2, when considering patients for PARP inhibitor treatment.

CT-Guided Bone Biopsies in Metastatic Castration-Resistant Prostate Cancer: Factors Predictive of Maximum Tumor Yield.

PURPOSE: To evaluate the success rate of CT-guided bone biopsies in metastatic castration-resistant prostate cancer (mCRPC) and to investigate associated technical, imaging, and clinical parameters affecting diagnostic yields. MATERIALS AND METHODS: Eighty CT-guided bone biopsy specimens were obtained from 72 men (median age, 68 y; range, 49-89 y) enrolled in a multicenter trial to identify mechanisms of resistance in mCRPC. Successful biopsy was determined by histologic confirmation of tumor cells and successful isolation of RNA for molecular analysis. RESULTS: The overall success rate of CT-guided bone biopsies was 69% (55/80) based on histology and 64% (35/55) based on isolation of molecular material for RNA sequencing. Biopsies performed in lesions with areas of radiolucency had significantly higher diagnostic yields compared with lesions of predominantly dense sclerosis (95% vs 33%; P = .002) and lesions of predominantly subtle sclerosis (95% vs 65%; P = .04). Success rates increased in lesions with density ≤ 475 HU (79% for ≤ 475 HU vs 33% for > 475 HU; P = .001) and in lesions with ill-defined margins (76% for ill-defined margins vs 36% for well-circumscribed margins; P = .005). Alkaline phosphatase was the only clinical parameter to correlate significantly with diagnostic yield (83% for > 110 U/L vs 50% for ≤ 110 U/L; P = .001). CONCLUSIONS: Image-guided bone tumor biopsies can be successfully used to acquire cellular and molecular material for analyses in patients with osteoblastic prostate cancer metastases. Diagnostic yields are significantly increased in lesions with areas of radiolucency, density ≤ 475 HU, ill-defined margins, and interval growth and in patients with alkaline phosphatase > 110 U/L.

The role of membrane glycoprotein plasma cell antigen 1/ectonucleotide pyrophosphatase phosphodiesterase 1 in the pathogenesis of insulin resistance and related abnormalities.

Insulin resistance is a major feature of most patients with type 2 diabetes mellitus (T2D). A number of laboratories have observed that PC-1 (membrane [corrected] glycoprotein plasma cell antigen 1; also termed [corrected] ectonucleotide pyrophosphatase phosphodiesterase 1 or ENPP1) [corrected] is either overexpressed or overactive in muscle, adipose tissue, fibroblasts, and other tissues of insulin-resistant individuals, both nondiabetic and diabetic. Moreover, PC-1 (ENPP1) overexpression [corrected] in cultured cells in vitro and in transgenic mice in vivo, [corrected] impairs insulin stimulation of insulin receptor (IR) activation and downstream signaling. PC-1 binds to the connecting domain of the IR alpha-subunit that is located in residues 485-599. The connecting domain transmits insulin binding in the alpha-subunit to activation of tyrosine kinase activation in the beta-subunit. When PC-1 is overexpressed, it inhibits insulin [corrected]induced IR beta-subunit tyrosine kinase activity. In addition, a polymorphism of PC-1 (K121Q) in various ethnic populations is closely associated with insulin resistance, T2D, and cardio [corrected] and nephrovascular diseases. The product of this polymorphism has a 2- to 3-fold increased binding affinity for the IR and is more potent than the wild-type PC-1 protein (K121K) in inhibiting the IR. These data suggest therefore that PC-1 is a candidate protein that may play a role in human insulin resistance and T2D by its overexpression, its overactivity, or both.

Chromium supplementation in non-obese non-diabetic subjects is associated with a decline in insulin sensitivity.

BACKGROUND: The use of chromium supplements is widespread for the prevention and treatment of diabetes mellitus but there are conflicting reports on efficacy, possibly reflecting discrepant effects across different populations. In the present studies, we test the hypothesis that chromium supplementation raises serum chromium levels and correspondingly improves insulin sensitivity. METHODS: A double blind placebo-controlled randomized trial was conducted on 31 non-obese, normoglycemic subjects. After baseline studies, the subjects were randomized to placebo or chromium picolinate 500 µg twice a day. The primary endpoint was change in insulin sensitivity as measured by euglycemic hyperinsulinemic clamp. Pre-specified secondary endpoints included fasting lipids, blood pressure, weight, body composition measured by DXA scan. RESULTS: After 16 weeks of chromium picolinate therapy there was no significant change in insulin sensitivity between groups (p=0.83). There was, however, a strong association between serum chromium and change in insulin resistance (ß = -0.83, p=0.01), where subjects with the highest serum chromium had a worsening of insulin sensitivity. This effect could not be explained by changes in physiological parameters such as body weight, truncal fat and serum lipids with chromium therapy. CONCLUSIONS: Chromium therapy did not improve insulin sensitivity in non-obese normoglycemic individuals. Further, subjects who have high serum chromium levels paradoxically had a decline in insulin sensitivity. Caution therefore should be exercised in recommending the use of this supplement. TRIAL REGISTRATION: The study was registered on the NIH registry (clinicaltrials.gov) and the identifier is NCT00846248.

Transcriptional profiling of matched patient biopsies clarifies molecular determinants of enzalutamide-induced lineage plasticity.

The androgen receptor (AR) signaling inhibitor enzalutamide (enza) is one of the principal treatments for metastatic castration-resistant prostate cancer (CRPC). Several emergent enza clinical resistance mechanisms have been described, including lineage plasticity in which the tumors manifest reduced dependency on the AR. To improve our understanding of enza resistance, herein we analyze the transcriptomes of matched biopsies from men with metastatic CRPC obtained prior to treatment and at progression (n = 21). RNA-sequencing analysis demonstrates that enza does not induce marked, sustained changes in the tumor transcriptome in most patients. However, three patients' progression biopsies show evidence of lineage plasticity. The transcription factor E2F1 and pathways linked to tumor stemness are highly activated in baseline biopsies from patients whose tumors undergo lineage plasticity. We find a gene signature enriched in these baseline biopsies that is strongly associated with poor survival in independent patient cohorts and with risk of castration-induced lineage plasticity in patient-derived xenograft models, suggesting that tumors harboring this gene expression program may be at particular risk for resistance mediated by lineage plasticity and poor outcomes.

Synthesis of aryl-heteroaryl ureas (AHUs) based on 4-aminoquinoline and their evaluation against the insulin-like growth factor receptor (IGF-1R).

The insulin-like growth factor receptor (IGF-1R) is a receptor tyrosine kinase (RTK) involved in all stages of the development and propagation of breast and other cancers. The inhibition of IGF-1R by small molecules remains a promising strategy to treat cancer. Herein, we explore SAR around previously characterized lead compound (1), which is an aryl-heteroaryl urea (AHU) consisting of 4-aminoquinaldine and a substituted aromatic ring system. A library of novel AHU compounds was prepared based on derivatives of the 4-aminoquinoline heterocycle (including various 2-substituted derivatives, and naphthyridines). The compounds were screened for in vitro inhibitory activity against IGF-1R, and several compounds with improved activity (3-5 microM) were identified. Furthermore, a computational docking study was performed, which identifies a fairly consistent lowest energy mode of binding for the more-active set of inhibitors in this series, while the less-active inhibitors do not adopt a consistent mode of binding.

Copy Number Loss of 17q22 Is Associated with Enzalutamide Resistance and Poor Prognosis in Metastatic Castration-Resistant Prostate Cancer.

PURPOSE: The purpose of this study was to measure genomic changes that emerge with enzalutamide treatment using analyses of whole-genome sequencing and RNA sequencing. EXPERIMENTAL DESIGN: One hundred and one tumors from men with metastatic castration-resistant prostate cancer (mCRPC) who had not been treated with enzalutamide (n = 64) or who had enzalutamide-resistant mCRPC (n = 37) underwent whole genome sequencing. Ninety-nine of these tumors also underwent RNA sequencing. We analyzed the genomes and transcriptomes of these mCRPC tumors. RESULTS: Copy number loss was more common than gain in enzalutamide-resistant tumors. Specially, we identified 124 protein-coding genes that were more commonly lost in enzalutamide-resistant samples. These 124 genes included eight putative tumor suppressors located at nine distinct genomic regions. We demonstrated that focal deletion of the 17q22 locus that includes RNF43 and SRSF1 was not present in any patient with enzalutamide-naïve mCRPC but was present in 16% (6/37) of patients with enzalutamide-resistant mCRPC. 17q22 loss was associated with lower RNF43 and SRSF1 expression and poor overall survival from time of biopsy [median overall survival of 19.3 months in 17q22 intact vs. 8.9 months in 17q22 loss, HR, 3.44 95% confidence interval (CI), 1.338-8.867, log-rank P = 0.006]. Finally, 17q22 loss was linked with activation of several targetable factors, including CDK1/2, Akt, and PLK1, demonstrating the potential therapeutic relevance of 17q22 loss in mCRPC. CONCLUSIONS: Copy number loss is common in enzalutamide-resistant tumors. Focal deletion of chromosome 17q22 defines a previously unappreciated molecular subset of enzalutamide-resistant mCRPC associated with poor clinical outcome.

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/ß-catenin pathway as the top differentially modulated pathway among enzalutamide-resistant patients. Furthermore, ß-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/ß-catenin pathway plays an important role in enzalutamide resistance, with differential pathway expression and enrichment of ß-catenin mutations in enzalutamide-resistant patients. Moreover, ß-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.

Nordihydroguaiaretic acid (NDGA), an inhibitor of the HER2 and IGF-1 receptor tyrosine kinases, blocks the growth of HER2-overexpressing human breast cancer cells.

We have reported that nordihydroguaiaretic acid (NDGA) inhibits the tyrosine kinase activities of the IGF-1 receptor (IGF-1R) and the HER2 receptor in breast cancer cells. Herein, we studied the effects of NDGA on the growth of estrogen receptor (ER) positive MCF-7 cells engineered to overexpress HER2 (MCF-7/HER2-18). These cells are an in vitro model of HER2-driven, ER positive, tamoxifen resistant breast cancer. NDGA was equally effective at inhibiting the growth of both parental MCF-7 and MCF-7/HER2-18 cells. Half maximal effects for both cell lines were in the 10-15 microM range. The growth inhibitory effects of NDGA were associated with an S phase arrest in the cell cycle and the induction of apoptosis. NDGA inhibited both IGF-1R and HER2 kinase activities in these breast cancer cells. In contrast, Gefitinib, an epidermal growth factor receptor inhibitor but not an IGF-1R inhibitor, was more effective in MCF-7/HER2-18 cells than in the parental MCF-7 cells and IGF binding protein-3 (IGFBP-3) was more effective against MCF-7 cells compared to MCF-7/HER2-18. MCF-7/HER2-18 cells are known to be resistant to the effects of the estrogen receptor inhibitor, tamoxifen. Interestingly, NDGA not only inhibited the growth of MCF-7/HER2-18 on its own, but it also demonstrated additive growth inhibitory effects when combined with tamoxifen. These studies suggest that NDGA may have therapeutic benefits in HER2-positive, tamoxifen resistant, breast cancers in humans.

A pilot dose-escalation study of the effects of nordihydroguareacetic acid on hormone and prostate specific antigen levels in patients with relapsed prostate cancer.

OBJECTIVE: To assess the tolerability of the effects of nordihydroguareacetic acid (NDGA) and its effect on prostate-specific antigen (PSA) kinetics in patients with relapsed prostate cancer, as among the many biological effects of NDGA is the inhibition of the insulin-like growth factor 1 receptor (IGF-1R) tyrosine kinase. PATIENTS AND METHODS: Eligible patients were those with an increasing PSA level after definitive local therapy, in either the non-castrate (androgen-dependent prostate cancer, ADPC) or the castrate state (castration-resistant prostate cancer, CRPC) with no evidence of metastatic disease by bone scan or computed tomography of the abdomen or pelvis. Treatment consisted of continuous oral daily dosing according to a planned dose escalation of 750, 1250, 1750, 2250 and 2500 mg of NDGA. PSA levels were measured every 28 days. Serial levels of testosterone, dihydrotestosterone, oestradiol and sex hormone-binding globulin were measured at baseline and monthly while on study therapy. RESULTS: Fifteen patients were enrolled, including 11 with ADPC and four with CRPC. There were asymptomatic increases in transaminase in six patients, two of which were grade 3, all occurring at >or=3 months. The increases in transaminase resolved after stopping NDGA but recurred with repeated dosing. Doses of NDGA up to 2500 mg/day caused no other toxicities. A median (range) of 5.5 (1-13) cycles were delivered. Of the 11 patients with ADPC, one had a decline in PSA level of >50% of the baseline value and one a decline of <50%. Three patients with ADPC had a greater than three-fold increase in PSA doubling time while on therapy, one from 11 to 46 months (750 mg), one from 9.5 to 49.5 months (1750 mg), and one from 5.9 to 46.2 months (2500 mg). There were no reductions in PSA level in patients with CRPC. There were no significant effects on levels of testosterone, dihydrotestosterone, oestradiol or sex hormone-binding globulin. CONCLUSIONS: Continuous daily dosing with NDGA is reasonably well tolerated but is associated with transaminitis in some patients, that occurs after several months on therapy. There were apparent effects on the rate of increase in PSA. Further study is required to determine the optimum pharmacokinetics and antitumour effects of this therapy.

Technical evaluation of in vivo abdominal fat and IMCL quantification using MRI and MRSI at 3 T.

OBJECTIVES: The objectives of this study were to develop protocols that measure abdominal fat and calf muscle lipids with magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS), respectively, at 3 T and to examine the correlation between these parameters and insulin sensitivity. MATERIALS AND METHODS: Ten nondiabetic subjects [five insulin-sensitive (IS) subjects and five insulin-resistant (IR) subjects] were scanned at 3 T. Visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were segmented semiautomatically from abdominal imaging. Intramyocellular lipids (IMCL) in calf muscles were quantified with single-voxel MRS in both soleus and tibialis anterior muscles and with magnetic resonance spectroscopic imaging (MRSI). RESULTS: The average coefficient of variation (CV) of VAT/(VAT+SAT) was 5.2%. The interoperator CV was 1.1% and 5.3% for SAT and VAT estimates, respectively. The CV of IMCL was 13.7% in soleus, 11.9% in tibialis anterior and 2.9% with MRSI. IMCL based on MRSI (3.8+/-1.2%) were significantly inversely correlated with glucose disposal rate, as measured by a hyperinsulinemic-euglycemic clamp. VAT volume correlated significantly with IMCL. IMCL based on MRSI for IR subjects was significantly greater than that for IS subjects (4.5+/-0.9% vs. 2.8+/-0.5%, P=.02). CONCLUSION: MRI and MRS techniques provide a robust noninvasive measurement of abdominal fat and muscle IMCL, which are correlated with insulin action in humans.

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.

Diarylureas are small-molecule inhibitors of insulin-like growth factor I receptor signaling and breast cancer cell growth.

In breast and certain other cancers, receptor tyrosine kinases, including the insulin-like growth factor I receptor (IGF-IR), play an important role in promoting the oncogenic process. The IGF-IR is therefore an important target for developing new anti-breast cancer therapies. An initial screening of a chemical library against the IGF-IR in breast cancer cells identified a diaryl urea compound as a potent inhibitor of IGF-IR signaling. This class of compounds has not been studied as inhibitors of the IGF-IR. We studied the effectiveness of one diaryl urea compound, PQ401, at antagonizing IGF-IR signaling and inhibiting breast cancer cell growth in culture and in vivo. PQ401 inhibited autophosphorylation of the IGF-IR in cultured human MCF-7 cells with an IC50 of 12 micromol/L and autophosphorylation of the isolated kinase domain of the IGF-IR with an IC50 <1 micromol/L. In addition, PQ401 inhibited the growth of cultured breast cancer cells in serum at 10 micromol/L. PQ401 was even more effective at inhibiting IGF-I-stimulated growth of MCF-7 cells (IC50, 6 micromol/L). Treatment of MCF-7 cells with PQ401 was associated with a decrease in IGF-I-mediated signaling through the Akt antiapoptotic pathway. Twenty-four hours of treatment with 15 micromol/L PQ401 induced caspase-mediated apoptosis. In vivo, treatment with PQ401 (i.p. injection thrice a week) reduced the growth rate of MCNeuA cells implanted into mice. These studies indicate that diaryl urea compounds are potential new agents to test in the treatment of breast and other IGF-I-sensitive cancers.

Androgen receptor amplification is concordant between circulating tumor cells and biopsies from men undergoing treatment for metastatic castration resistant prostate cancer.

Increased AR activity has been shown to be preserved in spatially distinct metastatic tumors from the same patient suggesting the requirement for lineage-specific dependencies for metastatic castration resistant prostate cancer (mCRPC). Amplification of the AR gene is a common mechanism by which mCRPC increase AR activity. To determine whether AR amplification in circulating tumor cells (CTC) could complement metastatic tissue biopsies in men undergoing treatment for mCRPC, we developed a novel two-step assay to isolate CTCs and subsequently analyzed AR amplification status in CTCs and matched biopsy tissue from the same patient by fluorescence in situ hybridization (FISH). AR gene status in CTCs showed strong concordance with AR gene status in matched tissue samples in 24 of 25 patients (Correlation: 96%; Kappa: 0.83; Sensitivity: 100%, Specificity: 83%). Our work demonstrates that AR amplification is conserved between CTCs and biopsies and that CTCs can serve as non-invasive surrogate to document AR amplification in mCRPC.

Real-Time Transferrin-Based PET Detects MYC-Positive Prostate Cancer.

Noninvasive biomarkers that detect the activity of important oncogenic drivers could significantly improve cancer diagnosis and management of treatment. The goal of this study was to determine whether 68Ga-citrate (which avidly binds to circulating transferrin) can detect MYC-positive prostate cancer tumors, as the transferrin receptor is a direct MYC target gene. PET imaging paired with 68Ga-citrate and molecular analysis of preclinical models, human cell-free DNA (cfDNA), and clinical biopsies were conducted to determine whether 68Ga-citrate can detect MYC-positive prostate cancer. Importantly, 68Ga-citrate detected human prostate cancer models in a MYC-dependent fashion. In patients with castration-resistant prostate cancer, analysis of cfDNA revealed that all patients with 68Ga-citrate avid tumors had a gain of at least one MYC copy number. Moreover, biopsy of two PET avid metastases showed molecular or histologic features characteristic of MYC hyperactivity. These data demonstrate that 68Ga-citrate targets prostate cancer tumors with MYC hyperactivity. A larger prospective study is ongoing to demonstrate the specificity of 68Ga-citrate for tumors with hyperactive MYC.Implications: Noninvasive measurement of MYC activity with quantitative imaging modalities could substantially increase our understanding of the role of MYC signaling in clinical settings for which invasive techniques are challenging to implement or do not characterize the biology of all tumors in a patient. Moreover, measuring MYC activity noninvasively opens the opportunity to study changes in MYC signaling in patients under targeted therapeutic conditions thought to indirectly inhibit MYC. Mol Cancer Res; 15(9); 1221-9. ©2017 AACR.

Concordance of Circulating Tumor DNA and Matched Metastatic Tissue Biopsy in Prostate Cancer.

BACKGROUND: Real-time knowledge of the somatic genome can influence management of patients with metastatic castration-resistant prostate cancer (mCRPC). While routine metastatic tissue biopsy is challenging in mCRPC, plasma circulating tumor DNA (ctDNA) has emerged as a minimally invasive tool to sample the tumor genome. However, no systematic comparisons of matched "liquid" and "solid" biopsies have been performed that would enable ctDNA profiling to replace the need for direct tissue sampling. METHODS: We performed targeted sequencing across 72 clinically relevant genes in 45 plasma cell-free DNA (cfDNA) samples collected at time of metastatic tissue biopsy. We compared ctDNA alterations with exome sequencing data generated from matched tissue and quantified the concordance of mutations and copy number alterations using the Fisher exact test and Pearson correlations. RESULTS: Seventy-five point six percent of cfDNA samples had a ctDNA proportion greater than 2% of total cfDNA. In these patients, all somatic mutations identified in matched metastatic tissue biopsies were concurrently present in ctDNA. Furthermore, the hierarchy of variant allele fractions for shared mutations was remarkably similar between ctDNA and tissue. Copy number profiles between matched liquid and solid biopsy were highly correlated, and individual copy number calls in clinically actionable genes were 88.9% concordant. Detected alterations included AR amplifications in 22 (64.7%) samples, SPOP mutations in three (8.8%) samples, and inactivating alterations in tumor suppressors TP53 , PTEN , RB1 , APC , CDKN1B , BRCA2 , and PIK3R1 . In several patients, ctDNA sequencing revealed robust changes not present in paired solid biopsy, including clinically relevant alterations in the AR, WNT, and PI3K pathways. CONCLUSIONS: Our study shows that, in the majority of patients, a ctDNA assay is sufficient to identify all driver DNA alterations present in matched metastatic tissue and supports development of DNA biomarkers to guide mCRPC patient management based on ctDNA alone.

Analysis of Circulating Cell-Free DNA Identifies Multiclonal Heterogeneity of BRCA2 Reversion Mutations Associated with Resistance to PARP Inhibitors.

Approximately 20% of metastatic prostate cancers harbor mutations in genes required for DNA repair by homologous recombination repair (HRR) such as BRCA2 HRR defects confer synthetic lethality to PARP inhibitors (PARPi) such as olaparib and talazoparib. In ovarian or breast cancers, olaparib resistance has been associated with HRR restoration, including by BRCA2 mutation reversion. Whether similar mechanisms operate in prostate cancer, and could be detected in liquid biopsies, is unclear. Here, we identify BRCA2 reversion mutations associated with olaparib and talazoparib resistance in patients with prostate cancer. Analysis of circulating cell-free DNA (cfDNA) reveals reversion mutation heterogeneity not discernable from a single solid-tumor biopsy and potentially allows monitoring for the emergence of PARPi resistance.Significance: The mechanisms of clinical resistance to PARPi in DNA repair-deficient prostate cancer have not been described. Here, we show BRCA2 reversion mutations in patients with prostate cancer with metastatic disease who developed resistance to talazoparib and olaparib. Furthermore, we show that PARPi resistance is highly multiclonal and that cfDNA allows monitoring for PARPi resistance. Cancer Discov; 7(9); 999-1005. ©2017 AACR.See related commentary by Domchek, p. 937See related article by Kondrashova et al., p. 984See related article by Goodall et al., p. 1006This article is highlighted in the In This Issue feature, p. 920.