Androgen receptor gene status in plasma DNA associates with worse outcome on enzalutamide or abiraterone for castration-resistant prostate cancer: a multi-institution correlative biomarker study

Evolution of the Liquid Biopsy in Metastatic Prostate Cancer

We reviewed the literature for the biologic, prognostic, and predictive significance of circulating prostate cancer tumor cells (CTCs), and circulating tumor DNA in the blood of metastatic castration resistant prostate cancer patients. CTCs demonstrate robust prognostic value independent of PSA in predicting overall survival. The CTC androgen receptor variant receptor 7 phenotype predicts resistance to androgen receptor synthesis inhibitors and sensitivity to taxane based chemotherapy in metastatic castration resistant prostate cancer patients who are candidates for second line therapy. Research is rapidly pivoting toward circulating tumor DNA analysis because the approach is sensitive, prognostic, cost effective, and it can elucidate mechanisms of systemic therapy.

Evaluation of Commercial Circulating Tumor DNA Test in Metastatic Prostate Cancer

PURPOSE

Circulating tumor DNA (ctDNA) sequencing provides a minimally invasive method for tumor molecular stratification. Commercial ctDNA sequencing is increasingly used in the clinic, but its accuracy in metastatic prostate cancer is untested. We compared the commercial Guardant360 ctDNA test against an academic sequencing approach for profiling metastatic prostate cancer.

PATIENTS AND METHODS

Plasma cell-free DNA was collected between September 2016 and April 2018 from 24 patients with clinically progressive metastatic prostate cancer representing a range of clinical scenarios. Each sample was analyzed using Guardant360 and a research panel encompassing 73 prostate cancer genes. Concordance of somatic mutation and copy number calls was evaluated between the two approaches.

RESULTS

Targeted sequencing independently confirmed 94% of somatic mutations identified by Guardant360 at an allele fraction greater than 1%. AR amplifications and mutations were detected with high concordance in 14 patients, with only three discordant subclonal mutations at an allele fraction lower than 0.5%. Many somatic mutations identified by Guardant360 at an allele fraction lower than 1% seemed to represent subclonal passenger events or non-prostate-derived clones. Most of the non-AR gene amplifications reported by Guardant360 represented single copy gains. The research approach detected several clinically relevant DNA repair gene alterations not reported by Guardant360, including four germline truncating BRCA2/ATM mutations, two somatic ATM stop gain mutations, one BRCA2 biallelic deletion, 11 BRCA2 stop gain reversal mutations in a patient treated with olaparib, and a hypermutator phenotype in a patient sample with 42 mutations per megabase.

CONCLUSION

Guardant360 accurately identifies somatic ctDNA mutations in patients with metastatic prostate cancer, but low allele frequency mutations should be interpreted with caution. Test utility in metastatic prostate cancer is currently limited by the lack of reporting on actionable deletions, rearrangements, and germline mutations.

Current status of liquid biopsies for the detection and management of prostate cancer

In recent years, new therapeutic options have become available for prostate cancer (PC) patients, generating an urgent need for better biomarkers to guide the choice of therapy and monitor treatment response. Liquid biopsies, including circulating tumor cells (CTCs), circulating nucleic acids, and exosomes, have been developed as minimally invasive assays allowing oncologists to monitor PC patients with real-time cellular or molecular information. While CTC counts remain the most extensively validated prognostic biomarker to monitor treatment response, recent advances demonstrate that CTC morphology and androgen receptor characterization can provide additional information to guide the choice of treatment. Characterization of cell-free DNA (cfDNA) is another rapidly emerging field with novel technologies capable of monitoring the evolution of treatment relevant alterations such as those in DNA damage repair genes for poly (ADP-ribose) polymerase (PARP) inhibition. In addition, several new liquid biopsy fields are emerging, including the characterization of heterogeneity, CTC RNA sequencing, the culture and xenografting of CTCs, and the characterization of extracellular vesicles (EVs) and circulating microRNAs. This review describes the clinical utilization of liquid biopsies in the management of PC patients and emerging liquid biopsy technologies with the potential to advance personalized cancer therapy.

Genomic correlates of clinical outcome in advanced prostate cancer

Heterogeneity in the genomic landscape of metastatic prostate cancer has become apparent through several comprehensive profiling efforts, but little is known about the impact of this heterogeneity on clinical outcome. Here, we report comprehensive genomic and transcriptomic analysis of 429 patients with metastatic castration-resistant prostate cancer (mCRPC) linked with longitudinal clinical outcomes, integrating findings from whole-exome, transcriptome, and histologic analysis. For 128 patients treated with a first-line next-generation androgen receptor signaling inhibitor (ARSI; abiraterone or enzalutamide), we examined the association of 18 recurrent DNA- and RNA-based genomic alterations, including androgen receptor (AR) variant expression, AR transcriptional output, and neuroendocrine expression signatures, with clinical outcomes. Of these, only RB1 alteration was significantly associated with poor survival, whereas alterations in RB1, AR, and TP53 were associated with shorter time on treatment with an ARSI. This large analysis integrating mCRPC genomics with histology and clinical outcomes identifies RB1 genomic alteration as a potent predictor of poor outcome, and is a community resource for further interrogation of clinical and molecular associations.

A bypass mechanism of abiraterone-resistant prostate cancer: Accumulating CYP17A1 substrates activate androgen receptor signaling

BACKGROUND

Intratumoral steroidogenesis and its potential relevance in castration-resistant prostate cancer (CRPC) and in cytochrome P450, family 17, subfamily A, polypeptide 1 (CYP17A1)-inhibitor treated hormone-naïve and patients with CRPC are not well established. In this study, we tested if substrates for de novo steroidogenesis accumulating during CYP17A1 inhibition may drive cell growth in relevant preclinical models.

METHODS

PCa cell lines and their respective CRPC sublines were used to model CRPC in vitro. Precursor steroids pregnenolone (Preg) and progesterone (Prog) served as substrate for de novo steroid synthesis. TAK700 (orteronel), abiraterone, and small interfering RNA (siRNA) against CYP17A1 were used to block CYP17A1 enzyme activity. The antiandrogen RD162 was used to assess androgen receptor (AR) involvement. Cell growth was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. AR-target gene expression was quantified by reverse transcription polymerase chain reaction (RT-PCR). Nuclear import studies using cells with green fluorescent protein (GFP)-tagged AR were performed to assess the potential of precursor steroids to directly activate AR.

RESULTS

Preg and Prog stimulated cell proliferation and AR target gene expression in VCaP, DuCaP, LNCaP, and their respective CRPC sublines. The antiandrogen RD162, but not CYP17A1 inhibition with TAK700, abiraterone or siRNA, was able to block Preg- and Prog-induced proliferation. In contrast to TAK700, abiraterone also affected dihydrotestosterone-induced cell growth, indicating direct AR binding. Furthermore, Prog-induced AR translocation was not affected by treatment with TAK700 or abiraterone, while it was effectively blocked by the AR antagonist enzalutamide, further demonstrating the direct AR activation by Prog.

CONCLUSION

Activation of the AR by clinically relevant levels of Preg and Prog accumulating in abiraterone-treated patients may act as a driver for CRPC. These data provide a scientific rationale for combining CYP17A1 inhibitors with antiandrogens, particularly in patients with overexpressed or mutated-AR.

Serum testosterone level is a useful biomarker for determining the optimal treatment for castration-resistant prostate cancer

OBJECTIVE

Our aim was to evaluate the usefulness of serum testosterone to guide treatment decision for castration-resistant prostate cancer (CRPC).

METHODS

We conducted a retrospective analysis of 115 patients with CRPC treated with either abiraterone (n = 43) or enzalutamide (n = 72). A serum testosterone level was measured at time of starting of abiraterone or enzalutamide. We determined whether serum testosterone influenced the outcomes of androgen receptor (AR)-targeted therapy.

RESULTS

In the very-low testosterone group (<5 ng/dl), the rate of prostate-specific antigen (PSA) response was significantly higher among patients treated with abiraterone compared to enzalutamide (62 vs. 32%, respectively; P = 0.033), with no difference in the low testosterone group (5-<50 ng/dl) (93 vs. 81%, respectively; P = 0.429). During the median follow-up of 26 months, PSA progression-free survival was significantly longer in the low testosterone group than in the very-low testosterone group (12.2 vs. 4.5 months, P<0.001). In the very-low testosterone group, enzalutamide use (HR 3.07, 95% CI 1.36-6.94; P = 0.007), primary androgen deprivation therapy <12 months (HR 2.50, 95% CI 1.23-5.08; P = 0.011) and bone metastases (HR 2.60, 95% CI 1.20-5.64; P = 0.015) were significantly associated with PSA progression.

CONCLUSION

Patients with a serum testosterone level ≥5 ng/dl were more likely to receive therapeutic benefits from AR-targeted therapy compared to those with serum testosterone levels <5 ng/dl. However, even for those with a very low serum testosterone level, the efficacy of abiraterone was slightly higher than that of enzalutamide. Therefore, serum testosterone level is a useful biomarker for informing treatment selection for CRPC.

Monitoring dynamic cytotoxic chemotherapy response in castration-resistant prostate cancer using plasma cell-free DNA (cfDNA)

Objective

Cell-free DNA (cfDNA) is an attractive cancer biomarker, as it is thought to reflect a component of the underlying genetic makeup of the tumor and is readily accessible in serial fashion. Because chemotherapy regimens are expected to act rapidly on cancer and cfDNA is cleared from the blood within minutes, we hypothesized that cfDNA would reflect immediate effects of treatment. Here, we developed a method for monitoring long cfDNA fragments, and report dynamic changes in response to cytotoxic chemotherapy.

Results

Peripheral blood was obtained from 15 patients with metastatic castration-resistant prostate cancer (CRPC) immediately before and after cytotoxic chemotherapy infusion. cfDNA was extracted and quantified for long interspersed nuclear elements (LINE1; 297 bp) using qPCR. Targeted deep sequencing was performed to quantify the frequency of mutations in exon 8 of the androgen receptor (AR), a mutational hotspot region in CRPC. Single nucleotide mutations in AR exon 8 were found in 6 subjects (6/15 = 40%). Analytical variability was minimized by pooling independent PCR reactions for each library. In 5 patients, tumor-derived long cfDNA levels were found to change immediately after infusion. Detailed analysis of one subject suggests that cytotoxic chemotherapy can produce rapidly observable effects on cfDNA.

Electronic supplementary material

The online version of this article (10.1186/s13104-019-4312-2) contains supplementary material, which is available to authorized users.

Clinical determinants for successful circulating tumor DNA analysis in prostate cancer

BACKGROUND

Plasma-based cell-free DNA is an attractive biospecimen for assessing somatic mutations due to minimally-invasive real-time sampling. However, next generation sequencing (NGS) of cell-free DNA (cfDNA) may not be appropriate for all patients with advanced prostate cancer (PC).

METHODS

Blood was obtained from advanced PC patients for plasma-based sequencing. UW-OncoPlex, a ∼2 Mb multi-gene NGS panel performed in the CLIA/CAP environment, was optimized for detecting cfDNA mutations. Tumor tissue and germline samples were sequenced for comparative analyses. Multivariate logistic regression was performed to determine the clinical characteristic associated with the successful detection of somatic cfDNA alterations (ie detection of at least one clearly somatic PC mutation).

RESULTS

Plasma for cfDNA sequencing was obtained from 93 PC patients along with tumor tissue (N = 67) and germline (N = 93) controls. We included data from 76 patients (72 prostate adenocarcinoma; 4 variant histology PC) in the analysis. Somatic DNA aberrations were detected in 34 cfDNA samples from patients with prostate adenocarcinoma. High PSA level, high tumor volume, and castration-resistance were significantly associated with successful detection of somatic cfDNA alterations. Among samples with somatic mutations detected, the cfDNA assay detected 93/102 (91%) alterations found in tumor tissue, yielding a clustering-corrected sensitivity of 92% (95% confidence interval 88-97%). All germline pathogenic variants present in lymphocyte DNA were also detected in cfDNA (N = 12). Somatic mutations from cfDNA were detected in 30/33 (93%) instances when PSA was >10 ng/mL.

CONCLUSIONS

Disease burden, including a PSA >10 ng/mL, is strongly associated with detecting somatic mutations from cfDNA specimens.

Circulating tumor DNA in advanced prostate cancer: transitioning from discovery to a clinically implemented test

The genomic landscape of metastatic castration-resistant prostate cancer (mCRPC) differs from that of the primary tumor and is dynamic during tumor progression. The real-time and repeated characterization of this process via conventional solid tumor biopsies is challenging. Alternatively, circulating cell-free DNA (cfDNA) containing circulating tumor DNA (ctDNA) can be obtained from patient plasma using minimally disruptive blood draws and is amenable to sequential analysis. ctDNA has high overlap with the genomic sequences of biopsies from metastases and has the advantage of being representative of multiple metastases. The availability of techniques with high sensitivity and specificity, such as next-generation sequencing (NGS) and digital PCR, has greatly contributed to the development of the cfDNA field and enabled the detection of genomic alterations at low ctDNA fractions. In mCRPC, a number of clinically relevant genomic alterations have been tracked in ctDNA, including androgen receptor (AR) aberrations, which have been shown to be associated with an adverse outcome to novel antiandrogen therapies, and alterations in homologous recombination repair (HRR) genes, which have been associated with a response to PARP inhibitors. Several clinical applications have been proposed for cfDNA analysis, including its use as a prognostic tool, as a predictive biomarker, to monitor tumor response and to identify novel mechanisms of resistance. To date, the cfDNA analysis has provided interesting results, but there is an urgent need for these findings to be confirmed in prospective clinical trials.

Circulating tumor DNA alterations in patients with metastatic castration-resistant prostate cancer

BACKGROUND

Because cell-free DNA (cfDNA) analysis facilitates the noninvasive genomic profiling of metastatic castration-resistant prostate cancer (mCRPC), the authors evaluated the association between cfDNA alterations and outcomes and evolution with therapy.

METHODS

Patients with mCRPC underwent cfDNA genomic profiling using Guardant360, which examines major cancer-associated genes. Clinical factors, therapy information, failure-free survival, and overall survival (OS) were obtained for select patients. The association between genomic alterations and outcomes was investigated.

RESULTS

Of 514 men with mCRPC, 482 (94%) had ≥1 circulating tumor DNA (ctDNA) alteration. The most common recurrent somatic mutations were in TP53 (36%), androgen receptor (AR) (22%), adenomatous polyposis coli (APC) (10%), neurofibromin 1 (NF1) (9%), epidermal growth factor receptor (EGFR), catenin beta-1 (CTNNB1), and AT-rich interactive domain-containing protein 1A (ARID1A) (6% each); and BRCA1, BRCA2, and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) (5% each) The most common genes with increased copy numbers were AR (30%), MYC (20%), and BRAF (18%). Clinical outcomes were available for 163 patients, 46 of whom (28.8%) were untreated for mCRPC. A higher number of ctDNA alterations, AR alterations, and amplifications of MYC and BRAF were associated with worse failure-free survival and/or OS. On multivariable analysis, MYC amplification remained significantly associated with OS. Prior therapy and serial profiling demonstrated the evolution of alterations in AR and other genes.

CONCLUSIONS

ctDNA frequently was detected in this large cohort of "real-world" patients with mCRPC, and the alterations appeared to be similar to previously reported tumor tissue alterations. A higher number of alterations, and AR and MYC alterations, appear to compromise clinical outcomes, suggesting a role for immune checkpoint inhibitors and novel AR and BET inhibitors in selected patients.

Genetic Alterations Detected in Cell-Free DNA Are Associated With Enzalutamide and Abiraterone Resistance in Castration-Resistant Prostate Cancer

PURPOSE

Androgen receptor (AR) gene alterations, including ligand-binding domain mutations and copy number (CN) gain, have yet to be fully established as predictive markers of resistance to enzalutamide and abiraterone in men with metastatic castration-resistant prostate cancer (mCRPC). The goal of this study was to validate AR gene alterations detected in cell-free DNA (cfDNA) as markers of enzalutamide and abiraterone resistance in patients with mCRPC.

METHODS

Patients with mCRPC (N = 62) were prospectively enrolled between 2014 and 2018. Blood was collected before therapies-enzalutamide (n = 25), abiraterone (n = 35), or enzalutamide and abiraterone (n = 2)-and at disease progression. We used deep next-generation sequencing to analyze cfDNA for sequence variants and CN status in AR and 45 additional cancer-associated genes. Primary end points were prostate-specific antigen response, progression-free survival (PFS), and overall survival (OS).

RESULTS

Elevated tumor-specific cfDNA (circulating tumor DNA) was associated with a worse prostate-specific antigen response (hazard ratio [HR], 3.17; 95% CI, 1.11 to 9.05; P = .031), PFS (HR, 1.76; 95% CI, 1.03 to 3.01; P = .039), and OS (HR, 2.92; 95% CI, 1.40 to 6.11; P = .004). AR ligand-binding domain missense mutations (HR, 2.51; 95% CI, 1.15 to 5.72; P = .020) were associated with a shorter PFS in multivariable models. AR CN gain was associated with a shorter PFS; however, significance was lost in multivariable modeling. Genetic alterations in tumor protein p53 (HR, 2.70; 95% CI, 1.27 to 5.72; P = .009) and phosphoinositide 3-kinase pathway defects (HR, 2.62; 95% CI, 1.12 to 6.10; P = .026) were associated with a worse OS in multivariable models.

CONCLUSION

These findings support the conclusion that high circulating tumor DNA burden is associated with worse outcomes to enzalutamide and abiraterone in men with mCRPC. Tumor protein p53 loss and phosphoinositide 3-kinase pathway defects were associated with worse OS in men with mCRPC. AR status associations with outcomes were not robust, and additional validation is needed.

Research status and progress of the RNA or protein biomarkers for prostate cancer

Prostate cancer is a kind of male malignancy. Recently, a large number of studies have reported many potential biomarkers for the diagnosis and prognosis of prostate cancer. In this literature review, we have collected a number of potential biomarkers for prostate cancer reported in the last 5 years. Among them, some are undergoing Phase III clinical trials, and others have been approved by the US Food and Drug Administration. However, most are still in the period of basic research. The review will contribute to future research to find the biomarkers to guide clinicians to make personalized treatment decisions for each prostate cancer patient.

Expression of AR-V7 and ARv567es in Circulating Tumor Cells Correlates with Outcomes to Taxane Therapy in Men with Metastatic Prostate Cancer Treated in TAXYNERGY

PURPOSE

Biomarkers aiding treatment optimization in metastatic castration-resistant prostate cancer (mCRPC) are scarce. The presence or absence of androgen receptor (AR) splice variants, AR-V7 and ARv567es, in mCRPC patient circulating tumor cells (CTC) may be associated with taxane treatment outcomes.Experimental Design: A novel digital droplet PCR (ddPCR) assay assessed AR-splice variant expression in CTCs from patients receiving docetaxel or cabazitaxel in TAXYNERGY (NCT01718353). Patient outcomes were examined according to AR-splice variant expression, including prostate-specific antigen (PSA)50 response and progression-free survival (PFS).

RESULTS

Of the 54 evaluable patients, 36 (67%) were AR-V7+, 42 (78%) were ARv567es+, 29 (54%) were double positive, and 5 (9%) were double negative. PSA50 response rates at any time were numerically higher for AR-V7- versus AR-V7+ (78% vs. 58%; P = 0.23) and for ARv567es- versus ARv567es+ (92% vs. 57%; P = 0.04) patients. When AR-V mRNA status was correlated with change in nuclear AR from cycle 1 day 1 to day 8 (n = 24), AR-V7+ patients (n = 16) had a 0.4% decrease versus a 12.9% and 26.7% decrease in AR-V7-/ARv567es- (n = 3) and AR-V7-/ARv567es+ (n = 5) patients, respectively, suggesting a dominant role for AR-V7 over ARv567es. Median PFS was 12.02 versus 8.48 months for AR-V7- versus AR-V7+ (HR = 0.38; P = 0.01), and 12.71 versus 7.29 months for ARv567es- versus ARv567es+ (HR = 0.37; P = 0.02). For AR-V7+, AR-V7-/ARv567es+, and AR-V7-/ARv567es- patients, median PFS was 8.48, 11.17, and 16.62 months, respectively (P = 0.0013 for trend).

CONCLUSIONS

Although detection of both CTC-specific AR-V7 and ARv567es by ddPCR influenced taxane outcomes, AR-V7 primarily mediated the prognostic impact. The absence of both variants was associated with the best response and PFS with taxane treatment.See related commentary by Dehm et al., p. 1696.

TP53 Outperforms Other Androgen Receptor Biomarkers to Predict Abiraterone or Enzalutamide Outcome in Metastatic Castration-Resistant Prostate Cancer

PURPOSE

To infer the prognostic value of simultaneous androgen receptor (AR) and TP53 profiling in liquid biopsies from patients with metastatic castration-resistant prostate cancer (mCRPC) starting a new line of AR signaling inhibitors (ARSi).Experimental Design: Between March 2014 and April 2017, we recruited patients with mCRPC (n = 168) prior to ARSi in a cohort study encompassing 10 European centers. Blood samples were collected for comprehensive profiling of CellSearch-enriched circulating tumor cells (CTC) and circulating tumor DNA (ctDNA). Targeted CTC RNA sequencing (RNA-seq) allowed the detection of eight AR splice variants (ARV). Low-pass whole-genome and targeted gene-body sequencing of AR and TP53 was applied to identify amplifications, loss of heterozygosity, mutations, and structural rearrangements in ctDNA. Clinical or radiologic progression-free survival (PFS) was estimated by Kaplan-Meier analysis, and independent associations were determined using multivariable Cox regression models.

RESULTS

Overall, no single AR perturbation remained associated with adverse prognosis after multivariable analysis. Instead, tumor burden estimates (CTC counts, ctDNA fraction, and visceral metastases) were significantly associated with PFS. TP53 inactivation harbored independent prognostic value [HR 1.88; 95% confidence interval (CI), 1.18-3.00; P = 0.008], and outperformed ARV expression and detection of genomic AR alterations. Using Cox coefficient analysis of clinical parameters and TP53 status, we identified three prognostic groups with differing PFS estimates (median, 14.7 vs. 7.51 vs. 2.62 months; P < 0.0001), which was validated in an independent mCRPC cohort (n = 202) starting first-line ARSi (median, 14.3 vs. 6.39 vs. 2.23 months; P < 0.0001).

CONCLUSIONS

In an all-comer cohort, tumor burden estimates and TP53 outperform any AR perturbation to infer prognosis.See related commentary by Rebello et al., p. 1699.

Clinical utility of androgen receptor gene aberrations in circulating cell-free DNA as a biomarker for treatment of castration-resistant prostate cancer

The therapeutic landscape of castration-resistant prostate cancer (CRPC) has rapidly expanded. There is a need to develop noninvasive biomarkers to guide treatment. We established a highly sensitive method for analyzing androgen receptor gene (AR) copy numbers (CN) and mutations in plasma circulating cell-free DNA (cfDNA) and evaluated the AR statuses of patients with CRPC. AR amplification was detectable in VCaP cell line (AR amplified) genomic DNA (gDNA) diluted to 1.0% by digital PCR (dPCR). AR mutation were detectable in LNCaP cell line (AR T878A mutated) gDNA diluted to 0.1% and 1.0% by dPCR and target sequencing, respectively. Next, we analyzed AR status in cfDNA from 102 patients. AR amplification and mutations were detected in 47 and 25 patients, respectively. As a biomarker, AR aberrations in pretreatment cfDNA were associated with poor response to abiraterone, but not enzalutamide. In serial cfDNA analysis from 41 patients, most AR aberrations at baseline diminished with effective treatments, whereas in some patients with disease progression, AR amplification or mutations emerged. The analysis of AR in cfDNA is feasible and informative procedure for treating patients with CRPC. cfDNA may become a useful biomarker for precision medicine in CRPC.

The interplay of circulating tumor DNA and chromatin modification, therapeutic resistance, and metastasis

Peripheral circulating free DNA (cfDNA) is DNA that is detected in plasma or serum fluid with a cell-free status. For cancer patients, cfDNA not only originates from apoptotic cells but also from necrotic tumor cells and disseminated tumor cells that have escaped into the blood during epithelial-mesenchymal transition. Additionally, cfDNA derived from tumors, also known as circulating tumor DNA (ctDNA), carries tumor-associated genetic and epigenetic changes in cancer patients, which makes ctDNA a potential biomarker for the early diagnosis of tumors, monitory and therapeutic evaluations, and prognostic assessments, among others, for various kinds of cancer. Moreover, analyses of cfDNA chromatin modifications can reflect the heterogeneity of tumors and have potential for predicting tumor drug resistance.

Plasma Androgen Receptor and Docetaxel for Metastatic Castration-resistant Prostate Cancer

Plasma androgen receptor (AR) gain identifies metastatic castration-resistant prostate cancer (mCRPC) patients with worse outcome on abiraterone/enzalutamide, but its relevance in the context of taxane chemotherapy is unknown. We aimed to evaluate whether docetaxel is active regardless of plasma AR and to perform an exploratory analysis to compare docetaxel with abiraterone/enzalutamide. This multi-institutional study was a pooled analysis of AR status, determined by droplet digital polymerase chain reaction, on pretreatment plasma samples. We evaluated associations between plasma AR and overall/progression-free survival (OS/PFS) and prostate-specific antigen (PSA) response rate in 163 docetaxel-treated patients. OS was significantly shorter in case of AR gain (hazard ratio [HR]=1.61, 95% confidence interval [CI]=1.08-2.39, p=0.018), but not PFS (HR=1.04, 95% CI 0.74-1.46, p=0.8) or PSA response (odds ratio=1.14, 95% CI=0.65-1.99, p=0.7). We investigated the interaction between plasma AR and treatment type after incorporating updated data from our prior study of 73 chemotherapy-naïve, abiraterone/enzalutamide-treated patients, with data from 115 first-line docetaxel patients. In an exploratory analysis of mCRPC patients receiving first-line therapies, a significant interaction was observed between plasma AR and docetaxel versus abiraterone/enzalutamide for OS (HR=0.16, 95% CI=0.06-0.46, p<0.001) and PFS (HR=0.31, 95% CI=0.12-0.80, p=0.02). Specifically, we reported a significant difference for OS favoring abiraterone/enzalutamide for AR-normal patients (HR=1.93, 95% CI=1.19-3.12, p=0.008) and a suggestion favoring docetaxel for AR-gained patients (HR=0.53, 95% CI=0.24-1.16, p=0.11). These data suggest that AR-normal patients should receive abiraterone/enzalutamide and AR-gained could benefit from docetaxel. This treatment selection merits prospective evaluation in a randomized trial. PATIENT SUMMARY: We investigated whether plasma androgen receptor (AR) predicted outcome in metastatic castration-resistant prostate cancer (mCRPC) patients treated with docetaxel, and we performed an exploratory analysis in patients treated with docetaxel or AR-directed drugs as first-line mCRPC therapy. We showed that plasma AR normal favored hormonal treatment, whilst plasma AR-gained patients may have had a longer response to docetaxel, suggesting that plasma AR status could be a useful treatment selection biomarker.

Application of cell-free DNA for genomic tumor profiling: a feasibility study

PURPOSE

Access to genomic tumor material is required to select patients for targeted therapies. However, tissue biopsies are not always feasible and therefore circulating cell-free DNA (cfDNA) has emerged as an alternative. Here we investigate the utility of cfDNA for genomic tumor profiling in the phase I setting.

STUDY DESIGN

Peripheral blood was collected from patients with advanced solid cancers eligible for phase I treatment. Patients failing the initial tissue biopsy due to inaccessible lesions or insufficient tumor cellularity (<10%) were included in the study. Genomic profiling of cfDNA including whole exome sequencing (WES) and somatic copy number alterations (SCNAs) analysis (OncoScan).

RESULTS

Plasma cfDNA was pro- and retrospectively profiled from 24 and 20 patients, respectively. The median turnaround time was 29 days (N= 24, range 13-87 days) compared to tissue re-analyses of median 60 days (N= 6, range 29-98). Selected cancer-associated alterations (SCAAs) were identified in 70% (31/44) of patients, predominantly by WES due to the low sensitivity of OncoScan on cfDNA. Primarily, inaccessible cases of prostate and lung cancers could benefit from cfDNA profiling. In contrast, breast cancer patients showed a low level of tumor-specific cfDNA which might be due to cancer type and/or active treatment at the time of plasma collection.

CONCLUSION

Plasma cfDNA profiling using WES is feasible within a clinically relevant timeframe and represents an alternative to invasive tissue biopsies to identify possible treatment targets. Especially, difficult-to-biopsy cancers can benefit from cfDNA profiling, but tumor tissue remains the gold standard for molecular analyses.

Biological Evolution of Castration-resistant Prostate Cancer

CONTEXT

Recent studies focused on the molecular characterization of metastatic prostate cancer have identified genomic subsets and emerging resistance patterns. Detection of these alterations in patients has potential implications for therapy selection and prognostication.

OBJECTIVE

The primary objective is to review the current landscape of clinical and molecular biomarkers in advanced prostate cancer and understand how they may reflect underlying tumor biology. We also discuss how these features may potentially impact earlier stages of the disease.

EVIDENCE ACQUISITION

A literature search was performed of recent clinical biomarker/genomic studies focused on advanced metastatic prostate cancer as well as relevant preclinical studies investigating how these alterations influence therapy response or resistance.

EVIDENCE SYNTHESIS

Metastatic castration-resistant prostate cancer is commonly driven by androgen receptor signaling even after progression on potent hormonal agents, but other alterations may also be present or emerge during therapy resistance such as DNA repair gene aberrations or combined loss of tumor suppressor genes. Biological implications of these changes are context dependent, which may affect their detection and interpretation.

CONCLUSIONS

Molecular changes occur during prostate cancer progression and treatment resistance. Detection of genomic alterations has potential to influence therapy choice. Additional studies are warranted to elucidate the evolution of these changes and their impact in earlier stages of the disease.

PATIENT SUMMARY

We review the biology of advanced prostate cancer, and highlight opportunities and challenges for using biological or molecular assays to help guide individualized treatment decisions for patients.

Treatment of Advanced Prostate Cancer

The therapeutic landscape of prostate cancer has been transformed over the last decade by new therapeutics, advanced functional imaging, next-generation sequencing, and better use of existing therapies in early-stage disease. Until 2004, progression on androgen deprivation therapy for metastatic disease was treated with the addition of secondary hormonal manipulation; in the last decade, six systemic agents have been approved for the treatment of castration-resistant prostate cancer. We review clinical trials and survival benefit for these therapies and assess how the understanding of the disease shifted as these therapies were developed. We also discuss advances in noncastrate disease states, identification of biomarkers for prognosis and treatment selection, and opportunities in locoregional therapy to delay androgen deprivation therapy.

Plasma DNA Analysis in Prostate Cancer: Opportunities for Improving Clinical Management

BACKGROUND

Molecular characterization of tumors could be important for clinical management. Plasma DNA obtained noninvasively as a liquid biopsy could be widely applicable for clinical implementation in biomarker-based treatment strategies.

CONTENT

Prostate cancer is a disease with variable clinical outcomes and molecular features and therefore presents multiple opportunities for biomarker-based treatment optimization. Tissue analysis may not be representative of the lethal clone in localized disease or of intrapatient, intermetastases heterogeneity; fresh tissue is often challenging to obtain by biopsy of metastasis, whereas archival samples may not represent current disease and may be of insufficient quality. Plasma DNA is of variable tumor-to-normal fraction that requires accurate estimation using sensitively measured genomic events. In plasma with sufficient tumor content, the spectrum of genomic aberrations closely resembles tissue and could be used to molecularly characterize patients in real time. In this review we discuss the opportunities for improving clinical management by using plasma DNA analysis in different clinical scenarios across the disease spectrum, from detection of prostate cancer and disease relapse to treatment response prediction, response assessment, and interrogation of treatment resistance in metastatic prostate cancer. Combinational strategies may incorporate other modalities, including circulating tumor cells, circulating microRNA, and extracellular vesicles analysis, which could help to achieve more accurate characterization.

SUMMARY

There are many opportunities for plasma DNA analyses to change clinical management. However, there are challenges that need to be addressed to clinically implement a test, including the development of accurate, fit for purpose, and technically reproducible assay, followed by prospective validation in a large cohort of patients.

Androgen receptor splice variant-7 expression emerges with castration resistance in prostate cancer

BACKGROUND

Liquid biopsies have demonstrated that the constitutively active androgen receptor splice variant-7 (AR-V7) associates with reduced response and overall survival from endocrine therapies in castration-resistant prostate cancer (CRPC). However, these studies provide little information pertaining to AR-V7 expression in prostate cancer (PC) tissue.

METHODS

Following generation and validation of a potentially novel AR-V7 antibody for IHC, AR-V7 protein expression was determined for 358 primary prostate samples and 293 metastatic biopsies. Associations with disease progression, full-length androgen receptor (AR-FL) expression, response to therapy, and gene expression were determined.

RESULTS

We demonstrated that AR-V7 protein is rarely expressed (<1%) in primary PC but is frequently detected (75% of cases) following androgen deprivation therapy, with further significant (P = 0.020) increase in expression following abiraterone acetate or enzalutamide therapy. In CRPC, AR-V7 expression is predominantly (94% of cases) nuclear and correlates with AR-FL expression (P ≤ 0.001) and AR copy number (P = 0.026). However, dissociation of expression was observed, suggesting that mRNA splicing remains crucial for AR-V7 generation. AR-V7 expression was heterogeneous between different metastases from a patient, although AR-V7 expression was similar within a metastasis. Moreover, AR-V7 expression correlated with a unique 59-gene signature in CRPC, including HOXB13, a critical coregulator of AR-V7 function. Finally, AR-V7-negative disease associated with better prostate-specific antigen (PSA) responses (100% vs. 54%, P = 0.03) and overall survival (74.3 vs. 25.2 months, hazard ratio 0.23 [0.07-0.79], P = 0.02) from endocrine therapies (pre-chemotherapy).

CONCLUSION

This study provides impetus to develop therapies that abrogate AR-V7 signaling to improve our understanding of AR-V7 biology and to confirm the clinical significance of AR-V7.

FUNDING

Work at the University of Washington and in the Plymate and Nelson laboratories is supported by the Department of Defense Prostate Cancer Research Program (W81XWH-14-2-0183, W81XWH-12-PCRP-TIA, W81XWH-15-1-0430, and W81XWH-13-2-0070), the Pacific Northwest Prostate Cancer SPORE (P50CA97186), the Institute for Prostate Cancer Research, the Veterans Affairs Research Program, the NIH/National Cancer Institute (P01CA163227), and the Prostate Cancer Foundation. Work in the de Bono laboratory was supported by funding from the Movember Foundation/Prostate Cancer UK (CEO13-2-002), the US Department of Defense (W81XWH-13-2-0093), the Prostate Cancer Foundation (20131017 and 20131017-1), Stand Up To Cancer (SU2C-AACR-DT0712), Cancer Research UK (CRM108X-A25144), and the UK Department of Health through an Experimental Cancer Medicine Centre grant (ECMC-CRM064X).

Tumor fraction in cell-free DNA as a biomarker in prostate cancer

BACKGROUND

Tumor content in circulating cell-free DNA (cfDNA) is a promising biomarker, but longitudinal dynamics of tumor-derived and non-tumor-derived cfDNA through multiple courses of therapy have not been well described.

METHODS

CfDNA from 663 plasma samples from 140 patients with castration-resistant prostate cancer (CRPC) was subject to sparse whole genome sequencing. Tumor fraction (TFx) estimated using the computational tool ichorCNA was correlated with clinical features and responses to therapy.

RESULTS

TFx associated with the number of bone metastases (median TFx = 0.014 with no bone metastases, 0.047 with 1-3 bone metastases, 0.190 for 4+ bone metastases; P < 0.0001) and with visceral metastases (P < 0.0001). In multivariable analysis, TFx remained associated with metastasis location (P = 0.042); TFx was positively correlated with alkaline phosphatase (P = 0.0227) and negatively correlated with hemoglobin (Hgb) (P < 0.001), but it was not correlated with prostate specific antigen (PSA) (P = 0.75). Tumor-derived and non-tumor-derived cfDNA track together and do not increase with generalized tissue damage from chemotherapy or radiation at the time scales examined. All new treatments that led to ≥30% PSA decline at 6 weeks were associated with TFx decline when baseline TFx was >7%; however, TFx in patients being subsequently maintained on secondary hormonal therapy was quite dynamic.

CONCLUSION

TFx correlates with clinical features associated with overall survival in CRPC, and TFx decline is a promising biomarker for initial therapeutic response.

TRIAL REGISTRATION

Dana-Farber/Harvard Cancer Center (DF/HCC) protocol no. 18-135.

FUNDING

Wong Family Award in Translational Oncology, Dana Farber Cancer Institute Medical Oncology grant, Gerstner Family Foundation, Janssen Pharmaceuticals Inc., and Koch Institute Support (core) grant P30-CA14051 from the National Cancer Institute (NCI).

Liquid biopsy approach in the management of prostate cancer

Liquid biopsies examine tumor cells or tumor genomic content in circulating fluids. In advanced prostate cancer which metastasizes frequently to the bone, it is difficult to evaluate underlying and evolving genomic heterogeneity of skeletal metastases for effecting clinical care for which reason liquid biopsies offer an alternate approach. In this review, we will summarize the current state of a wide variety of liquid biopsy-based biomarker assays currently being investigated and developed for managing prostate cancer. We will also highlight technical and clinical challenges and opportunities for translating liquid biopsies into clinical applications.

Enzalutamide therapy for advanced prostate cancer: efficacy, resistance and beyond

The androgen receptor drives the growth of metastatic castration-resistant prostate cancer. This has led to the development of multiple novel drugs targeting this hormone-regulated transcription factor, such as enzalutamide – a potent androgen receptor antagonist. Despite the plethora of possible treatment options, the absolute survival benefit of each treatment separately is limited to a few months. Therefore, current research efforts are directed to determine the optimal sequence of therapies, discover novel drugs effective in metastatic castration-resistant prostate cancer and define patient subpopulations that ultimately benefit from these treatments. Molecular studies provide evidence on which pathways mediate treatment resistance and may lead to improved treatment for metastatic castration-resistant prostate cancer. This review provides, firstly a concise overview of the clinical development, use and effectiveness of enzalutamide in the treatment of advanced prostate cancer, secondly it describes translational research addressing enzalutamide response vs resistance and lastly highlights novel potential treatment strategies in the enzalutamide-resistant setting.

Enzalutamide-resistant castration-resistant prostate cancer: challenges and solutions

The new-generation hormonal agent enzalutamide has been approved for the treatment of metastatic castration-resistant prostate cancer (CRPC), in both post- and predocetaxel setting, due to the significant improvement in overall survival. More recently, enzalutamide also showed impressive results in the treatment of men with nonmetastatic CRPC. Unfortunately, not all patients with CRPC are responsive to enzalutamide, and even in responders, benefits are limited by the development of drug resistance. Adaptive resistance of metastatic prostate cancer to enzalutamide treatment can be due to the activation of both androgen receptor (AR)-dependent pathways (expression of constitutively active AR splice variants, AR point mutations, gene amplification and overexpression) and mechanisms independent of AR signaling pathway (altered steroidogenesis, upregulation of the glucocorticoid receptor, epithelial–mesenchymal transition, neuroendocrine transformation, autophagy and activation of the immune system). In this review, we focus on resistance mechanisms to enzalutamide, exploring how we could overcome them through novel therapeutic options.

Plasma androgen receptor and serum chromogranin A in advanced prostate cancer

Recently, mixed forms between adenocarcinoma and neuroendocrine prostate cancer (NEPC) have emerged that are characterized by persistent androgen receptor (AR)-signalling and elevated chromogranin A (CgA) levels. The main aim of this study was to analyze castration-resistant prostate cancer (CRPC) patients treated with abiraterone or enzalutamide, assessing progression-free/overall survival (PFS/OS) in association with circulating AR and CgA. AR aberrations were analyzed by droplet digital PCR in pre-treatment plasma samples collected from two biomarker protocols [197 patients from a retrospective study (REC 2192/2013) and 59 from a prospective trial (REC 6798/2015)]. We subdivided patients into three groups according to CgA by receiver-operating characteristic (ROC) curves. In the primary cohort, plasma AR gain and mutations (p.L702H/p.T878A) were detected in 78 (39.6%) and 16 (8.1%) patients, respectively. We observed a significantly worse PFS/OS in patients with higher-CgA than in patients with normal-CgA, especially those with no AR-aberrations. Multivariable analysis showed AR gain, higher-CgA and LDH levels as independent predictors of PFS [hazard ratio (HR) = 2.16, 95% confidence interval (95% CI) 1.50-3.12, p < 0.0001, HR = 1.73, 95% CI 1.06-2.84, p = 0.026, and HR = 2.13, 95% CI 1.45-3.13, p = 0.0001, respectively) and OS (HR = 1.72, 95% CI 1.15-2.57, p = 0.008, HR = 3.63, 95% CI 2.13-6.20, p < 0.0001, and HR = 2.31, 95% CI 1.54-3.48, p < 0.0001, respectively). These data were confirmed in the secondary cohort. Pre-treatment CgA detection could be useful to identify these mixed tumors and would seem to have a prognostic role, especially in AR-normal patients. This association needs further evaluation in larger prospective cohorts.

Developments in urologic oncology "OncoForum": The best of 2017

OBJECTIVE

To put forth new findings of urologic oncology with impact on clinical practice presented during 2017 in the main annual meetings.

METHODS

This document reviews abstracts on prostate, kidney and bladder cancer presented at the congresses of 2016 (EAU, AUA, ASCO, ESMO and ASTRO) and publications with the highest impact in this period valued with the highest scores by the OncoForum committee.

RESULTS

Among patients at high risk of recurrent renal cell carcinoma after nephrectomy, adjuvant sunitinib compared to placebo showed a benefit in patients at higher risk of recurrence. In cisplatin-ineligible advanced urothelial cancer, pembrolizumab elicits clinically meaningful, durable responses. Among patients with localized prostate cancer, treatment for disease progression was less frequent (absolute difference, 26.2 percentage pontis) and adverse events was more frequent with surgery than with observation. Among patients with locally advanced or merastatic prostate cancer, androgen-deprivation therapy plus abiraterone and prednisolone resulted in fewer deaths and fewer treatment-failure events (P<.001). Among patients with metastatic castration-resistant prostate cancer previously treated with abiraterone acetate, enzalutamide median radiographic progression free survival was 8,1 months and enzalutamide median overall survival was not reached.

CONCLUSIONS

Among patients at high risk of recurrent renal cell carcinoma after nephrectomy, adjuvant sunitinib showed a benefit across subgroups including patients at higher risk of recurrence. Among patients with localized prostate cancer, surgery was not associated with significantly lower all-cause or porstate-cancer mortality than observation. Among patients with locally advanced or merastatic prostate cancer, androgen-deprivation therapy plus abiraterone and prednisolone was associated with significantly higher rates of overall and failure-free survival than androgen-deprivation therapy alone. In patients with metastatic castration-resistant prostate cancer previously treated with abiraterone enzalutamide remained active.

Phase II pilot study of the prednisone to dexamethasone switch in metastatic castration-resistant prostate cancer (mCRPC) patients with limited progression on abiraterone plus prednisone (SWITCH study)

BACKGROUND

Despite most metastatic castration-resistant prostate cancer (mCRPC) patients benefit from abiraterone acetate plus prednisone 5 mg bid (AA + P), resistance eventually occurs. Long-term use of prednisone has been suggested as one of the mechanisms driving resistance, which may be reversed by switching to another steroid.

METHODS

SWITCH was a single-arm, open-label, single-stage phase II study. The primary objective was to evaluate the antitumour activity of abiraterone acetate plus dexamethasone 0.5 mg daily (AA + D) in mCRPC patients progressing to AA + P. Clinically stable mCRPC patients who had prostate-specific antigen (PSA) and/or limited radiographic progression after at least 12 weeks on AA + P, were eligible. The primary endpoint was measured as the proportion of patients achieving a PSA decline of  ≥ 30% (PSA30) from baseline after 6 weeks on AA + D. Secondary endpoints included: PSA50 response rate at 12 weeks, time to biochemical and radiological progression, overall survival, safety profile evaluation, benefit from subsequent treatment lines and the identification of biomarkers of response (AR copy number, TMPRSS2-ERG status and PTEN expression).

RESULTS

Twenty-six patients were enrolled. PSA30 and PSA50 were 46.2% and 34.6%, respectively. Median time to biochemical and radiological progression were 5.3 and 11.8 months, respectively. Two radiological responses were observed. Median overall survival was 20.9 months. Patients with AR gain detected in plasma circulating tumour DNA did not respond to switch, whereas patients with AR normal status benefited the most. No significant toxicities were observed and PSA50 response rate to subsequent taxane was 50%.

CONCLUSIONS

In selected clinical stable mCRPC patients with limited disease progression on AA + P, a steroid switch from prednisone to dexamethasone can lead to PSA and radiological responses.

Recent Advances in Liquid Biopsy in Patients With Castration Resistant Prostate Cancer

Management of localized and advanced prostate cancer benefits from several therapeutic options with a surprising improvement in terms of clinical outcome. The selection of patients more likely to benefit from a specific approach still remains a key issue as well as the early identification of patients with aggressive disease which could benefit from a more aggressive treatment strategy. The lack of reliable bio-marker in castration resistant setting able to monitor response to treatment and early inform about tumor progression is an emerging issue. Accordingly, circulating DNA and circulating tumor cells appears a promising and attractive approach despite to date practical applications of these techniques are few and not validated. The aim of this review of the literature is to explore current knowledge on liquid biopsy in prostate cancer focusing on possible future applications.

Assessment of the Validity of Nuclear-Localized Androgen Receptor Splice Variant 7 in Circulating Tumor Cells as a Predictive Biomarker for Castration-Resistant Prostate Cancer

Importance

A blood test to determine whether to treat patients with metastatic castration-resistant prostate cancer (mCRPC) with an androgen receptor signaling (ARS) inhibitor or taxane is an unmet medical need.

Objective

To determine whether a validated assay for the nuclear-localized androgen receptor splice variant 7 (AR-V7) protein in circulating tumor cells can determine differential overall survival among patients with mCRPC treated with taxanes vs ARS inhibitors.

Design, Setting, and Participants

This blinded correlative study conducted from December 31, 2012, to September 1, 2016, included 142 patients with histologically confirmed mCRPC and who were treated at Memorial Sloan Kettering Cancer Center, The Royal Marsden, or the London Health Sciences Centre. Blood samples were obtained prior to administration of ARS inhibitors or taxanes as a second-line or greater systemic therapy for progressing mCRPC.

Main Outcomes and Measures

Overall survival after treatment with an ARS inhibitor or taxane in relation to pretherapy AR-V7 status.

Results

Among the 142 patients in the study (mean [SD] age, 69.5 [9.6] years), 70 were designated as high risk by conventional prognostic factors. In this high-risk group, patients positive for AR-V7 who were treated with taxanes had superior overall survival relative to those treated with ARS inhibitors (median overall survival, 14.3 vs 7.3 months; hazard ratio, 0.62; 95% CI, 0.28-1.39; P = .25). Patients negative for AR-V7 who were treated with ARS inhibitors had superior overall survival relative to those treated with taxanes (median overall survival, 19.8 vs 12.8 months; hazard ratio, 1.67; 95% CI, 1.00-2.81; P = .05).

Conclusions and Relevance

This study suggests that nuclear-localized AR-V7 protein in circulating tumor cells can identify patients who may live longer with taxane chemotherapy vs ARS inhibitor treatment.

Abiraterone Alone or in Combination With Enzalutamide in Metastatic Castration-Resistant Prostate Cancer With Rising Prostate-Specific Antigen During Enzalutamide Treatment

Purpose Enzalutamide resistance could result from raised androgens and be overcome by combination with abiraterone acetate. PLATO ( ClinicalTrials.gov identifier: NCT01995513) interrogated this hypothesis using a randomized, double-blind, placebo-controlled design. Patients and Methods In period one, men with chemotherapy-naïve metastatic castration-resistant prostate cancer received open-label enzalutamide 160 mg daily. Men with no prostate-specific antigen (PSA) increase at weeks 13 and 21 were treated until PSA progression (≥ 25% increase and ≥ 2 ng/mL above nadir), then randomly assigned at a one-to-one ratio in period two to abiraterone acetate 1,000 mg daily and prednisone 5 mg twice daily with either enzalutamide or placebo (combination or control group, respectively) until disease progression as defined by the primary end point: progression-free survival (radiographic or unequivocal clinical progression or death during study). Secondary end points included time to PSA progression and PSA response in period two. Results Of 509 patients enrolled in period one, 251 were randomly assigned in period two. Median progression-free survival was 5.7 months in the combination group and 5.6 months in the control group (hazard ratio, 0.83; 95% CI, 0.61 to 1.12; P = .22). There was no difference in the secondary end points. Grade 3 hypertension (10% v 2%) and increased ALT (6% v 2%) or AST (2% v 0%) were more frequent in the combination than the control group. Conclusion Combining enzalutamide with abiraterone acetate and prednisone is not indicated after PSA progression during treatment with enzalutamide alone; hypertension and elevated liver enzymes are more frequent with combination therapy.

Genomic alterations in plasma DNA from patients with metastasized prostate cancer receiving abiraterone or enzalutamide

In patients with metastatic castrate-resistant prostate cancer (mCRPC), circulating tumor DNA (ctDNA) analysis offers novel opportunities for the development of non-invasive biomarkers informative of treatment response with novel agents targeting the androgen-receptor (AR) pathway, such as abiraterone or enzalutamide. However, the relationship between ctDNA abundance, detectable somatic genomic alterations and clinical progression of mCRPC remains unexplored. Our study aimed to investigate changes in plasma DNA during disease progression and their associations with clinical variables in mCRPC patients. We analyzed ctDNA in two cohorts including 94 plasma samples from 25 treatment courses (23 patients) and 334 plasma samples from 125 patients, respectively. We conducted whole-genome sequencing (plasma-Seq) for genome-wide profiling of somatic copy number alterations and targeted sequencing of 31 prostate cancer-associated genes. The combination of plasma-Seq with targeted AR analyses identified prostate cancer-related genomic alterations in 16 of 25 (64%) treatment courses in the first cohort, in which we demonstrated that AR amplification does not always correlate with poor abiraterone and enzalutamide therapy outcome. As we observed a wide variability of ctDNA levels, we evaluated ctDNA levels and their association with clinical parameters and included the second, larger cohort for these analyses. Employing altogether 428 longitudinal plasma samples from 148 patients, we identified the presence of bone metastases, increased lactate dehydrogenase and prostate-specific antigen (PSA) as having the strongest association with high ctDNA levels. In summary, ctDNA alterations are observable in the majority of patients with mCRPC and may eventually be useful to guide clinical decision-making in this setting.

Circulating Tumour DNA in Muscle-Invasive Bladder Cancer

Circulating tumour DNA (ctDNA) is an attractive tool in cancer research, offering many advantages over tissue samples obtained using traditional biopsy methods. There has been increasing interest in its application to muscle-invasive bladder cancer (MIBC), which is recognised to be a heterogeneous disease with overall poor prognosis. Using a range of platforms, studies have shown that ctDNA is detectable in MIBC and may be a useful biomarker in monitoring disease status and guiding treatment decisions in MIBC patients. Currently, with no such predictive or prognostic biomarkers in clinical practice to guide treatment strategy, there is a real unmet need for a personalised medicine approach in MIBC, and ctDNA offers an exciting avenue through which to pursue this goal. In this article, we present an overview of work to date on ctDNA in MIBC, and discuss the inherent challenges present as well as the potential future clinical applications.

Constitutively active androgen receptor splice variants AR-V3, AR-V7 and AR-V9 are co-expressed in castration-resistant prostate cancer metastases

BACKGROUND

A significant subset of prostate cancer (PC) patients with a castration-resistant form of the disease (CRPC) show primary resistance to androgen receptor (AR)-targeting drugs developed against CRPC. As one explanation could be the expression of constitutively active androgen receptor splice variants (AR-Vs), our current objectives were to study AR-Vs and other AR aberrations to better understand the emergence of CRPC.

METHODS

We analysed specimens from different stages of prostate cancer by next-generation sequencing and immunohistochemistry.

RESULTS

AR mutations and copy number variations were detected only in CRPC specimens. Genomic structural rearrangements of AR were observed in 5/30 metastatic CRPC patients, but they were not associated with expression of previously known AR-Vs. The predominant AR-Vs detected were AR-V3, AR-V7 and AR-V9, with the expression levels being significantly higher in CRPC cases compared to prostatectomy samples. Out of 25 CRPC metastases that expressed any AR variant, 17 cases harboured expression of all three of these AR-Vs. AR-V7 protein expression was highly heterogeneous and higher in CRPC compared to hormone-naïve tumours.

CONCLUSIONS

AR-V3, AR-V7 and AR-V9 are co-expressed in CRPC metastases highlighting the fact that inhibiting AR function via regions common to all AR-Vs is likely to provide additional benefit to patients with CRPC.

Concurrent regulation of LKB1 and CaMKK2 in the activation of AMPK in castrate-resistant prostate cancer by a well-defined polyherbal mixture with anticancer properties

BACKGROUND

Zyflamend, a blend of herbal extracts, effectively inhibits tumor growth using preclinical models of castrate-resistant prostate cancer mediated in part by 5'-adenosine monophosphate-activated protein kinase (AMPK), a master energy sensor of the cell. Clinically, treatment with Zyflamend and/or metformin (activators of AMPK) had benefits in castrate-resistant prostate cancer patients who no longer responded to treatment. Two predominant upstream kinases are known to activate AMPK: liver kinase B1 (LKB1), a tumor suppressor, and calcium-calmodulin kinase kinase-2 (CaMKK2), a tumor promotor over-expressed in many cancers. The objective was to interrogate how Zyflamend activates AMPK by determining the roles of LKB1 and CaMKK2.

METHODS

AMPK activation was determined in CWR22Rv1 cells treated with a variety of inhibitors of LKB1 and CaMKK2 in the presence and absence of Zyflamend, and in LKB1-null HeLa cells that constitutively express CaMKK2, following transfection with wild type LKB1 or catalytically-dead mutants. Upstream regulation by Zyflamend of LKB1 and CaMKK2 was investigated targeting protein kinase C-zeta (PKCζ) and death-associated protein kinase (DAPK), respectively.

RESULTS

Zyflamend's activation of AMPK appears to be LKB1 dependent, while simultaneously inhibiting CaMKK2 activity. Zyflamend failed to rescue the activation of AMPK in the presence of pharmacological and molecular inhibitors of LKB1, an effect not observed in the presence of inhibitors of CaMKK2. Using LKB1-null and catalytically-dead LKB1-transfected HeLa cells that constitutively express CaMKK2, ionomycin (activator of CaMKK2) increased phosphorylation of AMPK, but Zyflamend only had an effect in cells transfected with wild type LKB1. Zyflamend appears to inhibit CaMKK2 by DAPK-mediated phosphorylation of CaMKK2 at Ser511, an effect prevented by a DAPK inhibitor. Alternatively, Zyflamend mediates LKB1 activation via increased phosphorylation of PKCζ, where it induced translocation of PKCζ and LKB1 to their respective active compartments in HeLa cells following treatment. Altering the catalytic activity of LKB1 did not alter this translocation.

DISCUSSION

Zyflamend's activation of AMPK is mediated by LKB1, possibly via PKCζ, but independent of CaMKK2 by a mechanism that appears to involve DAPK.

CONCLUSIONS

Therefore, this is the first evidence that natural products simultaneously and antithetically regulate upstream kinases, known to be involved in cancer, via the activation of AMPK.

Utility of cell-free nucleic acid and circulating tumor cell analyses in prostate cancer

Prostate cancer is characterized by bone metastases and difficulty of objectively measuring disease burden. In this context, cell-free circulating tumor DNA (ctDNA) and circulating tumor cell (CTC) quantitation and genomic profiling afford the ability to noninvasively and serially monitor the tumor. Recent data suggest that ctDNA and CTC quantitation are prognostic for survival. Indeed, CTC enumeration using the CellSearch® platform is validated as a prognostic factor and warrants consideration as a stratification factor in randomized trials. Changes in quantities of CTCs using CellSearch also are prognostic and may be employed to detect a signal of activity of new agents. Molecular profiling of both CTCs and ctDNA for androgen receptor (AR) variants has been associated with outcomes in the setting of novel androgen inhibitors. Serial profiling to detect the evolution of new alterations may inform drug development and help develop precision medicine. The costs of these assays and the small quantities in which they are detectable in blood are a limitation, and novel platforms are required to address this challenge. The presence of multiple platforms to assay CTCs and ctDNA also warrants the consideration of a mechanism to allow comparison of data across platforms. Further validation and the continued development and standardization of these promising modalities will facilitate their adoption in the clinic.

Plasma DNA and Metastatic Castration-Resistant Prostate Cancer: The Odyssey to a Clinical Biomarker Test

Comprehensive plasma DNA analysis identifies clinically actionable genomic aberrations. Cancers harboring disruption of TP53 or BRCA2 or ATM detected in plasma have significantly worse outcomes on novel AR targeting. Cancer Discov; 8(4); 392-4. ©2018 AACR.See related article by Annala et al., p. 444.

Development and Application of Liquid Biopsies in Metastatic Prostate Cancer

PURPOSE OF REVIEW

Metastatic prostate cancer is a lethal and highly heterogeneous malignancy, associated with a broad spectrum of potentially actionable molecular alterations. In the past decade, disease profiling has expanded to include not only traditional tumor tissue, but also liquid biopsies of cells and genetic material circulating in the blood. These liquid biopsies offer a minimally invasive, repeatable source of tumor material for longitudinal disease profiling but also raise new technical and biological challenges. Here we will summarize recent advances in liquid biopsy strategies and the role they have played in biomarker development and disease management.

RECENT FINDINGS

Technologies for analysis of circulating tumor cells (CTCs) continue to evolve rapidly, and the latest high content scanning platforms have underscored the phenotypic heterogeneity of CTC populations. Among liquid biopsies, CTC enumeration remains the most extensively validated prognostic marker to date, but other clinically relevant phenotypes like androgen receptor (AR) localization or presence of AR-V7 splice variant are important new predictors of therapy response. Serial genomic profiling of CTCs or circulating tumor DNA (ctDNA) is helping to define primary and acquired resistance mechanisms and helping to guide patient selection for targeted therapies such as poly(adenosine diphosphate [ADP] ribose) polymerase (PARP) inhibition. The era of liquid biopsy-based biomarkers has arrived, driven by powerful new enrichment and analysis techniques. As new blood-based markers are identified, their biological significance as disease drivers must be elucidated to advance new therapeutic strategies, and their clinical impact must be translated through assay standardization, followed by analytical and clinical validation. These efforts, already ongoing on multiple fronts, constitute the critical steps toward more effective precision management of advanced prostate cancer.

Recent advances in the management of metastatic prostate cancer: optimizing use of existing therapies, while searching for novel interventions

PURPOSE OF REVIEW

Summarizes recent advances in the treatment of metastatic castration-sensitive and castration-resistant prostate cancer.

RECENT FINDINGS

New randomized data suggest a survival advantage to early abiraterone in castration-sensitive metastatic prostate cancer. Prospective and retrospective studies are examining sequencing of existing cytotoxic and androgen-receptor-targeted therapies in both castration-sensitive and castration-resistant disease. Genomic analysis of both circulating tumor cells and circulating tumor nucleic acids is being examined as a potential method for selecting existing therapies and identifying novel therapeutic targets. Finally, immunotherapy combinations are being evaluated in the setting of advanced prostate cancer.

SUMMARY

In this review, we hope to summarize the recent data supporting the use of early abiraterone in castration-sensitive metastatic prostate cancer and discuss how this data might be incorporated with previous trials showing a survival advantage to early docetaxel. We present recent series examining sequencing of approved therapies as well as trials evaluating novel biomarkers and genomic analyses designed to help choose from among approved therapies or evaluate drugs in development. Lastly, we review ongoing trials examining novel immunotherapy combinations in advanced prostate cancer.

Targeting Bromodomain and Extra-Terminal (BET) Family Proteins in Castration-Resistant Prostate Cancer (CRPC)

Purpose: Persistent androgen receptor (AR) signaling drives castration-resistant prostate cancer (CRPC) and confers resistance to AR-targeting therapies. Novel therapeutic strategies to overcome this are urgently required. We evaluated how bromodomain and extra-terminal (BET) protein inhibitors (BETi) abrogate aberrant AR signaling in CRPC.Experimental Design: We determined associations between BET expression, AR-driven transcription, and patient outcome; and the effect and mechanism by which chemical BETi (JQ1 and GSK1210151A; I-BET151) and BET family protein knockdown regulates AR-V7 expression and AR signaling in prostate cancer models.Results: Nuclear BRD4 protein expression increases significantly (P ≤ 0.01) with castration resistance in same patient treatment-naïve (median H-score; interquartile range: 100; 100-170) and CRPC (150; 110-200) biopsies, with higher expression at diagnosis associating with worse outcome (HR, 3.25; 95% CI, 1.50-7.01; P ≤ 0.001). BRD2, BRD3, and BRD4 RNA expression in CRPC biopsies correlates with AR-driven transcription (all P ≤ 0.001). Chemical BETi, and combined BET family protein knockdown, reduce AR-V7 expression and AR signaling. This was not recapitulated by C-MYC knockdown. In addition, we show that BETi regulates RNA processing thereby reducing alternative splicing and AR-V7 expression. Furthermore, BETi reduce growth of prostate cancer cells and patient-derived organoids with known AR mutations, AR amplification and AR-V7 expression. Finally, BETi, unlike enzalutamide, decreases persistent AR signaling and growth (P ≤ 0.001) of a patient-derived xenograft model of CRPC with AR amplification and AR-V7 expression.Conclusions: BETi merit clinical evaluation as inhibitors of AR splicing and function, with trials demonstrating their blockade in proof-of-mechanism pharmacodynamic studies. Clin Cancer Res; 24(13); 3149-62. ©2018 AACR.

Optimizing the treatment of metastatic castration-resistant prostate cancer: a Latin America perspective

Prostate cancer is a significant burden and cause of mortality in Latin America. This article reviews the treatment options for patients with metastatic castration-resistant prostate cancer (mCRPC) and provides consensus recommendations to assist Latin American prostate cancer specialists with clinical decision making. A multidisciplinary expert panel from Latin America reviewed the available data and their individual experience to develop clinical consensus opinions for the use of life-prolonging agents in mCRPC, with consideration given to factors influencing patient selection and treatment monitoring. There is a lack of level 1 evidence for the best treatment sequence or combinations in mCRPC. In this context, consensus recommendations were provided for the use of taxane-based chemotherapies, androgen receptor axis-targeted agents and targeted alpha therapy, for patients in Latin America. Prostate-specific antigen (PSA) changes alone, during treatment, should be treated with caution; PSA may not be a suitable biomarker for radium-223. Bone scans and computed tomography are the standard imaging modalities in Latin America. Imaging should be prompted during treatment where symptomatic decline and/or significant worsening of laboratory evaluations are reported, or where a course of therapy has been completed and another antineoplastic agent is under consideration. Recommendations and guidance for treatment options in Latin America are provided in the context of country-level variable access to approved agents and technologies for treatment monitoring. Patients should be treated with the purpose of prolonging overall survival and preserving quality of life through increasing the opportunity to administer all available life-prolonging therapies when appropriate.

Association among metabolic syndrome, inflammation, and survival in prostate cancer

BACKGROUND

Metabolic syndrome (MS) and inflammation (INF) alterations are among the factors involved in cancer progression. The study aimed to assess the relationship between MS and INF and its effect on progression-free/overall survival (PFS/OS) in metastatic castration-resistant prostate cancer (mCRPC) treaed with abiraterone or enzalutamide.

METHODS

We, retrospectively, evaluated patients with mCRPC in 7 Italian Institutes between March 2011 and October 2016. MS was defined by modified adult treatment panel-III criteria. INF was characterized by at least one of these criteria: neutrophil to lymphocyte ratio ≥ 3, elevated erythrocyte sedimentation rate or C-reactive protein.

RESULTS

Eighty-three of 551 (15.1%) patients met MS criteria at baseline and 34 (6.2%) during treatment. MS patients (MS+) presented a greater INF profile compared to MS- (P<0.0001). Median PFS was 3.7 for MS+ vs. 8.7 months for MS- (hazard ratio [HR] = 2.77; 95% CI: 2.12-3.61; P<0.0001). Median OS was 6.9 and 19 months in MS+ and MS-, respectively (HR = 3.43; 95% CI: 2.56-4.58; P<0.0001). We also demonstrated INF led to shorter PFS and OS (4.5 vs. 8.5 months, HR = 1.48, 95% CI: 1.15-1.90, P = 0.002, and 11.2 vs. 18.8 months, HR =1.66, 95% CI: 1.26-2.18, P = 0.0003, respectively). The combination of MS with INF provided the identification of high-risk prognostic group (MS+/INF+ vs. MS-/INF-) with worse PFS (3.7 vs. 9 months, HR = 2.7, 95% CI: 1.88-3.89, P<0.0001) and OS (6.3 vs. 20.4 months, HR = 4.04, 95% CI: 2.75-5.93, P<0.0001). Multivariable analysis confirmed that MS was independently associated with PFS (HR = 2.07; 95% CI: 1.03-4.18; P = 0.041) and OS (HR = 4.87; 95% CI: 2.36-10.03; P<0.0001). The absence of INF as an independent predictor of survival underlined the correlation between MS/INF.

CONCLUSIONS

Pretreatment identification of MS and INF alterations might represent an available and easy tool for better prognostication of patients with mCRPC. A prospective evaluation is warranted.

The potential of AR-V7 as a therapeutic target

INTRODUCTION

The androgen receptor variant AR-V7 is gaining attention as a potential predictive marker for as well as one of the resistance mechanisms to the most current anti-androgen receptor (AR) therapies in castration-resistant prostate cancer (CRPC). Accordingly, development of next-generation drugs that directly or indirectly target AR-V7 signaling is urgently needed. Areas covered: We review proposed mechanisms of drug resistance in relation to AR-V7 status, the mechanisms of generation of AR-V7, and its transcriptome, cistrome, and interactome. Pharmacological agents that interfere with these processes are being developed to counteract pan AR and AR-V7-specific signaling. Also, we address the current status of the preclinical and clinical studies targeting AR-V7 signaling. Expert opinion: AR-V7 is considered a true therapeutic target, however, it remains to be determined if AR-V7 is a principal driver or merely a bystander requiring heterodimerization with co-expressed full-length AR or other variants to drive CRPC progression. While untangling AR-V7 biology, multiple strategies are being developed to counteract drug resistance, including selective blockade of AR-V7 signaling as well as inhibition of pan-AR signaling. Ideally anti-AR therapies will be combined with agents preventing activation and enrichment of AR negative tumor cells that are otherwise depressed by AR activity axis.

Circulating Tumor DNA Genomics Correlate with Resistance to Abiraterone and Enzalutamide in Prostate Cancer

Primary resistance to androgen receptor (AR)-directed therapies in metastatic castration-resistant prostate cancer (mCRPC) is poorly understood. We randomized 202 patients with treatment-naïve mCRPC to abiraterone or enzalutamide and performed whole-exome and deep targeted 72-gene sequencing of plasma cell-free DNA prior to therapy. For these agents, which have never been directly compared, time to progression was similar. Defects in BRCA2 and ATM were strongly associated with poor clinical outcomes independently of clinical prognostic factors and circulating tumor DNA abundance. Somatic alterations in TP53, previously linked to reduced tumor dependency on AR signaling, were also independently associated with rapid resistance. Although detection of AR amplifications did not outperform standard prognostic biomarkers, AR gene structural rearrangements truncating the ligand binding domain were identified in several patients with primary resistance. These findings establish genomic drivers of resistance to first-line AR-directed therapy in mCRPC and identify potential minimally invasive biomarkers.Significance: Leveraging plasma specimens collected in a large randomized phase II trial, we report the relative impact of common circulating tumor DNA alterations on patient response to the most widely used therapies for advanced prostate cancer. Our findings suggest that liquid biopsy analysis can guide the use of AR-targeted therapy in general practice. Cancer Discov; 8(4); 444-57. ©2018 AACR.See related commentary by Jayaram et al., p. 392This article is highlighted in the In This Issue feature, p. 371.