Prostein expression on circulating tumor cells as a prognostic marker in metastatic castration-resistant prostate cancer

BACKGROUND

Identification of emerging molecular biomarkers on circulating tumor cells (CTCs) represents an attractive feature of liquid biopsy that facilitates precision and tailored medicine in the management of metastatic castration-resistant prostate cancer (mCRPC). Prostein is an androgen-regulated transmembrane protein with high prostate specificity. Prostein-positive circulating tumor cell (CTC) was recently suggested to have diagnostic potential; however, no study has been conducted to evaluate its prognostic value in mCRPC.

METHODS

CTCs from mCRPC patients were enumerated using the CellSearch System. Prostein-positive CTCs were identified by immunostaining results. The relationships between prostein expression on CTCs and PSA response rate, PSA progression-free survival (PSA-PFS), radiographic progression-free survival (PFS), and overall survival (OS) were tested by Fisher's exact test or evaluated using Kaplan-Meier and multivariate Cox analyses.

RESULTS

Prostein-positive CTCs were identified in 31 of 87 baseline samples from mCRPC patients and 16 of 51 samples collected at the first follow-up visit. PSA response rates were significantly lower in baseline prostein-positive patients (0%, 0/31) than in prostein-negative patients (19.6%, 11/56) (p = 0.007). The 31 prostein-positive patients had significantly shorter PSA-PFS (p < 0.001), radiographic PFS (p < 0.001), and OS (p = 0.018), compared to the 56 prostein-negative patients at baseline. The association with PSA-PFS maintained its significance (p = 0.028) in multivariate analyses. Analyzing prostein expression at the first follow-up as well as the conversion of prostein expression from baseline to follow-up samples not only confirmed the association with PSA-PFS, but also demonstrated prognostic significance with OS.

CONCLUSION

Our study provides the first evidence to support the potential of prostein expression on CTCs to serve as a novel prognostic marker in mCRPC patients. Future large-scale prospective studies are needed to validate our findings.

Pharmacogenetic and clinical risk factors for bevacizumab-related gastrointestinal hemorrhage in prostate cancer patients treated on CALGB 90401 (Alliance)

The objective of this study was to discover clinical and pharmacogenetic factors associated with bevacizumab-related gastrointestinal hemorrhage in Cancer and Leukemia Group B (Alliance) 90401. Patients with metastatic castration-resistant prostate cancer received docetaxel and prednisone ± bevacizumab. Patients were genotyped using Illumina HumanHap610-Quad and assessed using cause-specific risk for association between single nucleotide polymorphisms (SNPs) and gastrointestinal hemorrhage. In 1008 patients, grade 2 or higher gastrointestinal hemorrhage occurred in 9.5% and 3.8% of bevacizumab (n = 503) and placebo (n = 505) treated patients, respectively. Bevacizumab (P < 0.001) and age (P = 0.002) were associated with gastrointestinal hemorrhage. In 616 genetically estimated Europeans (n = 314 bevacizumab and n = 302 placebo treated patients), grade 2 or higher gastrointestinal hemorrhage occurred in 9.6% and 2.0% of patients, respectively. One SNP (rs1478947; HR 6.26; 95% CI 3.19-12.28; P = 9.40 × 10-8) surpassed Bonferroni-corrected significance. Grade 2 or higher gastrointestinal hemorrhage rate was 33.3% and 6.2% in bevacizumab-treated patients with the AA/AG and GG genotypes, versus 2.9% and 1.9% in the placebo arm, respectively. Prospective validation of these findings and functional analyses are needed to better understand the genetic contribution to treatment-related gastrointestinal hemorrhage.

Xaluritamig, a STEAP1 × CD3 XmAb 2+1 Immune Therapy for Metastatic Castration-Resistant Prostate Cancer: Results from Dose Exploration in a First-in-Human Study

Xaluritamig (AMG 509) is a six-transmembrane epithelial antigen of the prostate 1 (STEAP1)-targeted T-cell engager designed to facilitate lysis of STEAP1-expressing cancer cells, such as those in advanced prostate cancer. This first-in-human study reports monotherapy dose exploration for patients with metastatic castration-resistant prostate cancer (mCRPC), primarily taxane pretreated. Ninety-seven patients received ≥1 intravenous dose ranging from 0.001 to 2.0 mg weekly or every 2 weeks. MTD was identified as 1.5 mg i.v. weekly via a 3-step dose. The most common treatment-related adverse events were cytokine release syndrome (CRS; 72%), fatigue (45%), and myalgia (34%). CRS occurred primarily during cycle 1 and improved with premedication and step dosing. Prostate-specific antigen (PSA) and RECIST responses across cohorts were encouraging [49% PSA50; 24% objective response rate (ORR)], with greater frequency at target doses ≥0.75 mg (59% PSA50; 41% ORR). Xaluritamig is a novel immunotherapy for prostate cancer that has shown encouraging results supporting further development.

SIGNIFICANCE

Xaluritamig demonstrated encouraging responses (PSA and RECIST) compared with historical established treatments for patients with late-line mCRPC. This study provides proof of concept for T-cell engagers as a potential treatment for prostate cancer, validates STEAP1 as a target, and supports further clinical investigation of xaluritamig in prostate cancer. See related commentary by Hage Chehade et al., p. 20. See related article by Nolan-Stevaux et al., p. 90. This article is featured in Selected Articles from This Issue, p. 5.

Targeting the αVβ3/NgR2 pathway in neuroendocrine prostate cancer

Highly aggressive, metastatic, neuroendocrine prostate cancer, which typically develops from prostate cancer cells acquiring resistance to androgen deprivation therapy, is associated with limited treatment options and hence poor prognosis. We have previously demonstrated that the αVβ3 integrin is over-expressed in neuroendocrine prostate cancer. We now show that LM609, a monoclonal antibody that specifically targets the human αVβ3 integrin, hinders the growth of neuroendocrine prostate cancer patient-derived xenografts in vivo. Our group has recently identified a novel αVβ3 integrin binding partner, NgR2, responsible for regulating the expression of neuroendocrine markers and for inducing neuroendocrine differentiation in prostate cancer cells. Through in vitro functional assays, we here demonstrate that NgR2 is crucial in promoting cell adhesion to αVβ3 ligands. Moreover, we describe for the first time co-fractionation of αVβ3 integrin and NgR2 in small extracellular vesicles derived from metastatic prostate cancer patients' plasma. These prostate cancer patient-derived small extracellular vesicles have a functional impact on human monocytes, increasing their adhesion to fibronectin. The monocytes incubated with small extracellular vesicles do not show an associated change in conventional polarization marker expression and appear to be in an early stage that may be defined as "adhesion competent". Overall, these findings allow us to better understand integrin-directed signaling and cell-cell communication during cancer progression. Furthermore, our results pave the way for new diagnostic and therapeutic perspectives for patients affected by neuroendocrine prostate cancer.

Review of Cardiovascular Risk of Androgen Deprivation Therapy and the Influence of Race in Men with Prostate Cancer

Androgen deprivation therapy is the cornerstone of prostate cancer therapy. Recent studies have revealed an association between androgen deprivation therapy and cardiovascular adverse effects such as myocardial infarction and stroke. This review summarizes the available research on the cardiovascular risk of men using androgen deprivation therapy. We also discuss racial disparities surrounding both prostate cancer and cardiovascular disease, emphasizing the importance of biological/molecular and socioeconomic factors in assessing baseline risk in patients beginning androgen ablation. Based on the literature, we provide recommendations for monitoring patients who are at high risk for a cardiovascular adverse event while being treated on androgen deprivation therapy. This review aims to present the current research on androgen deprivation therapy and cardiovascular toxicity with an emphasis on racial disparities and provides a framework for clinicians to decrease the cardiovascular morbidity in men that are being treated with hormone therapy.

Bispecific T-Cell Engagers Therapies in Solid Tumors: Focusing on Prostate Cancer

Over the past decade, immunotherapy has demonstrated an impressive improvement in treatment outcomes for multiple cancers. Following the landmark approvals for use of immune checkpoint inhibitors, new challenges emerged in various clinical settings. Not all tumor types harbor immunogenic characteristics capable of triggering responses. Similarly, many tumors' immune microenvironment allows them to become evasive, leading to resistance and, thus, limiting the durability of responses. To overcome this limitation, new T-cell redirecting strategies such as bispecific T-cell engager (BiTE) have become attractive and promising immunotherapies. Our review provides a comprehensive perspective of the current evidence of BiTE therapies in solid tumors. Considering that immunotherapy has shown modest results in advanced prostate cancer to date, we review the biologic rationale and promising results of BiTE therapy in this clinical setting and discuss potential tumor-associated antigens that may be integrated into BiTE construct designs. Our review also aims to evaluate the advances of BiTE therapies in prostate cancer, illustrate the major obstacles and underlying limitations, and discuss directions for future research.

Harnessing transcriptionally driven chromosomal instability adaptation to target therapy-refractory lethal prostate cancer

Metastatic prostate cancer (PCa) inevitably acquires resistance to standard therapy preceding lethality. Here, we unveil a chromosomal instability (CIN) tolerance mechanism as a therapeutic vulnerability of therapy-refractory lethal PCa. Through genomic and transcriptomic analysis of patient datasets, we find that castration and chemotherapy-resistant tumors display the highest CIN and mitotic kinase levels. Functional genomics screening coupled with quantitative phosphoproteomics identify MASTL kinase as a survival vulnerability specific of chemotherapy-resistant PCa cells. Mechanistically, MASTL upregulation is driven by transcriptional rewiring mechanisms involving the non-canonical transcription factors androgen receptor splice variant 7 and E2F7 in a circuitry that restrains deleterious CIN and prevents cell death selectively in metastatic therapy-resistant PCa cells. Notably, MASTL pharmacological inhibition re-sensitizes tumors to standard therapy and improves survival of pre-clinical models. These results uncover a targetable mechanism promoting high CIN adaptation and survival of lethal PCa.

The NOGO receptor NgR2, a novel αVβ3 integrin effector, induces neuroendocrine differentiation in prostate cancer

Androgen deprivation therapies aimed to target prostate cancer (PrCa) are only partially successful given the occurrence of neuroendocrine PrCa (NEPrCa), a highly aggressive and highly metastatic form of PrCa, for which there is no effective therapeutic approach. Our group has demonstrated that while absent in prostate adenocarcinoma, the αVβ3 integrin expression is increased during PrCa progression toward NEPrCa. Here, we show a novel pathway activated by αVβ3 that promotes NE differentiation (NED). This novel pathway requires the expression of a GPI-linked surface molecule, NgR2, also known as Nogo-66 receptor homolog 1. We show here that NgR2 is upregulated by αVβ3, to which it associates; we also show that it promotes NED and anchorage-independent growth, as well as a motile phenotype of PrCa cells. Given our observations that high levels of αVβ3 and, as shown here, of NgR2 are detected in human and mouse NEPrCa, our findings appear to be highly relevant to this aggressive and metastatic subtype of PrCa. This study is novel because NgR2 role has only minimally been investigated in cancer and has instead predominantly been analyzed in neurons. These data thus pave new avenues toward a comprehensive mechanistic understanding of integrin-directed signaling during PrCa progression toward a NE phenotype.

Technology-enhanced AcceleRation of Germline Evaluation for Therapy (TARGET): A randomized controlled trial of a pretest patient-driven webtool vs. genetic counseling for prostate cancer germline testing

BACKGROUND

Germline testing has an increasingly important role in prostate cancer care. However, a relative shortage of genetic counselors necessitates alternate strategies for delivery of pre-test education for germline testing. This study, funded by the Prostate Cancer Foundation, seeks to address the need for novel methods of delivery of pre-test germline education beyond traditional germline counseling to facilitate informed patient decision-making for germline testing.

METHODS

This is a two-armed randomized controlled trial (RCT) with a target enrollment of 173 participants with prostate cancer per study arm (total anticipated n = 346). Patients who meet criteria for germline testing based on tumor features, family history or Ashkenazi Jewish ancestry are being recruited from 5 US sites including academic, private practice and Veterans healthcare settings. Consenting participants are randomized to the interactive pretest webtool or germline counseling with assessment of key patient-reported outcomes involved in informed decision-making for germline germline testing.

RESULTS

Participants complete surveys at baseline, after pretest education/counseling, and following disclosure of germline germline results. The primary outcome of the study is decisional conflict for germline testing. Secondary outcomes include germline knowledge, satisfaction, uptake of germline testing, and understanding of results.

CONCLUSION

Our hypothesis is that the web-based germline education tool is non-inferior to traditional germline counseling regarding key patient-reported outcomes involved in informed decision-making for germline testing. If proven, the results would support deploying the webtool across various practice settings to facilitate pre-test germlines education for individuals with prostate cancer and developing collaborative care strategies with germline counseling.

CLINICALTRIALS

gov Identifier: NCT04447703.

Considerations on Integrating Prostate-Specific Membrane Antigen Positron Emission Tomography Imaging Into Clinical Prostate Cancer Trials by National Clinical Trials Network Cooperative Groups

PURPOSE

As prostate-specific membrane antigen (PSMA) positron emission tomography (PET) becomes increasingly available in the United States, the greater sensitivity of the technology in comparison to conventional imaging poses challenges for clinical trials. The NCI Clinical Imaging Steering Committee (CISC) PSMA PET Working Group was convened to coordinate the identification of these challenges in various clinical scenarios and to develop consensus recommendations on how best to integrate PSMA PET into ongoing and upcoming National Clinical Trials Network (NCTN) trials.

METHODS

NCI CISC and NCI Genitourinary Steering Committee members and leadership nominated clinicians, biostatisticians, patient advocates, and other imaging experts for inclusion in the PSMA PET Working Group. From April to July 2021, the working group met independently and in conjunction with the CISC to frame challenges, including stage migration, response assessment, trial logistics, and statistical challenges, and to discuss proposed solutions. An anonymous, open-ended survey was distributed to members to collect feedback on challenges faced. Representatives from each NCTN group were invited to present an overview of affected trials. From these discussions, the consensus document was developed and circulated for the inclusion of multiple rounds of feedback from both the Working Group and CISC.

RESULTS

The current consensus document outlines the key challenges for clinical prostate cancer trials resulting from the increasing availability of PSMA PET. We discuss implications for patient selection and definition of end points and provide guidance and potential solutions for different clinical scenarios, particularly with regard to best practices in defining eligibility criteria and outcome measures.

RECOMMENDATIONS

This article provides guidance regarding clinical trial design and conduct, and the interpretation of trial results.

A Novel Role for DNA-PK in Metabolism by Regulating Glycolysis in Castration-Resistant Prostate Cancer

PURPOSE

DNA-dependent protein kinase catalytic subunit (DNA-PKcs, herein referred as DNA-PK) is a multifunctional kinase of high cancer relevance. DNA-PK is deregulated in multiple tumor types, including prostate cancer, and is associated with poor outcomes. DNA-PK was previously nominated as a therapeutic target and DNA-PK inhibitors are currently undergoing clinical investigation. Although DNA-PK is well studied in DNA repair and transcriptional regulation, much remains to be understood about the way by which DNA-PK drives aggressive disease phenotypes.

EXPERIMENTAL DESIGN

Here, unbiased proteomic and metabolomic approaches in clinically relevant tumor models uncovered a novel role of DNA-PK in metabolic regulation of cancer progression. DNA-PK regulation of metabolism was interrogated using pharmacologic and genetic perturbation using in vitro cell models, in vivo xenografts, and ex vivo in patient-derived explants (PDE).

RESULTS

Key findings reveal: (i) the first-in-field DNA-PK protein interactome; (ii) numerous DNA-PK novel partners involved in glycolysis; (iii) DNA-PK interacts with, phosphorylates (in vitro), and increases the enzymatic activity of glycolytic enzymes ALDOA and PKM2; (iv) DNA-PK drives synthesis of glucose-derived pyruvate and lactate; (v) DNA-PK regulates glycolysis in vitro, in vivo, and ex vivo; and (vi) combination of DNA-PK inhibitor with glycolytic inhibitor 2-deoxyglucose leads to additive anti-proliferative effects in aggressive disease.

CONCLUSIONS

Findings herein unveil novel DNA-PK partners, substrates, and function in prostate cancer. DNA-PK impacts glycolysis through direct interaction with glycolytic enzymes and modulation of enzymatic activity. These events support energy production that may contribute to generation and/or maintenance of DNA-PK-mediated aggressive disease phenotypes.

Relevance of pRB Loss in Human Malignancies

The retinoblastoma tumor suppressor protein (pRB) is a known regulator of cell-cycle control; however, recent studies identified critical functions for pRB in regulating cancer-associated gene networks that influence the DNA damage response, apoptosis, and cell metabolism. Understanding the impact of these pRB functions on cancer development and progression in the clinical setting will be essential, given the prevalence of pRB loss of function across disease types. Moreover, the current state of evidence supports the concept that pRB loss results in pleiotropic effects distinct from tumor proliferation. Here, the implications of pRB loss (and resultant pathway deregulation) on disease progression and therapeutic response will be reviewed, based on clinical observation. Developing a better understanding of the pRB-regulated pathways that underpin the aggressive features of pRB-deficient tumors will be essential for further developing pRB as a biomarker of disease progression and for stratifying pRB-deficient tumors into more effective treatment regimens.

Helix: A Digital Tool to Address Provider Needs for Prostate Cancer Genetic Testing in Clinical Practice

BACKGROUND

Prostate cancer (PCA) germline testing (GT) is now standard-of-care for men with advanced PCA. Thousands of men may consider GT due to clinical and family history (FH) features. Identifying and consenting men for GT can be complex. Here we identified barriers and facilitators of GT across a spectrum of providers which informed the development of Helix - an educational and clinical/FH collection tool to facilitate GT in practice.

MATERIALS AND METHODS

A 12-question survey assessing knowledge of genetics PCA risk and FH was administered December 2017 to March 2018 in the Philadelphia area and at the Mid-Atlantic AUA meeting (March 2018). Responses were analyzed using descriptive statistics. Semi-structured interviews were conducted with medical oncologists, radiation oncologists, and urologists across practice settings from March-October 2020 as part of a larger study based on the Tailored Implementation in Chronic Diseases framework. Helix was then developed followed by user testing.

RESULTS

Fifty-six providers (50% urologists) responded to the survey. Multiple FH and genetic knowledge gaps were identified: only 66% collected maternal FH and 43% correctly identified BRCA2 and association to aggressive PCA. Genetic counseling gaps included low rates of discussing genetic discrimination laws (45%). Provider interviews (n = 14) identified barriers to FH intake including access to details and time needed. In user testing (n = 10), providers found Helix helpful for FH collection. All providers found Helix easy to use, suggesting expanded clinical use.

CONCLUSION

Helix addressed multiple GT knowledge and practice gaps across a spectrum of providers. This tool will become publicly available soon to facilitate PCA GT in clinical practice.

Pretest Genetic Education Video Versus Genetic Counseling for Men Considering Prostate Cancer Germline Testing: A Patient-Choice Study to Address Urgent Practice Needs

PURPOSE

Germline testing (GT) for prostate cancer (PCA) is now central to treatment and hereditary cancer assessment. With rising demand for and shortage of genetic counseling (GC), tools to deliver pretest informed consent across practice settings are needed to improve access to GT and precision care. Here, we report on Evaluation and Management for Prostate Oncology, Wellness, and Risk (EMPOWER), a patient-choice study for pretest video-based genetic education (VBGE) versus GC to inform urgent practice needs.

PATIENTS AND METHODS

Men with PCA or at risk for PCA (family history of PCA) were eligible and could choose pretest VBGE or GC. Outcomes included decisional conflict for GT, change in genetics knowledge, satisfaction, and intention to share results with family and/or providers. Descriptive statistics summarized results with counts and percentages for categorical variables and mean ± standard deviation for continuous variables. Data were compared with Fisher's exact, chi-squared, or Wilcoxon two-sample tests. Mean change in genetics knowledge was compared with t tests. The significance level was set a priori at .05.

RESULTS

Data on the first 127 participants were analyzed. Characteristics were White (85.8%), bachelor's degree (66.9%), and PCA diagnosis (90.6%). The majority chose VBGE (71%) versus GC (29%; P < .001). No differences were observed in decisional conflict for GT or satisfaction. Cancer genetics knowledge improved in both groups without significant difference (+0.9 VBGE, +1.8 GC, P = .056). Men who chose VBGE had higher intention to share GT results (96.4% VBGE v 86.4% GC, P = .02). Both groups had high rates of GT uptake (VBGE 94.4%, GC 92%).

CONCLUSION

A substantial proportion of men opted for pretest VBGE, with comparable patient-reported outcomes and uptake of GT. The results support the use of pretest video to address the critical GC shortage in the precision era.

Imaging urothelial bladder cancer: A VPAC PET targeted approach

INTRODUCTION Accurate staging of urothelial bladder cancer (UBC) with imaging, which guides effective bladder cancer treatment, remains challenging. This investigation is to validate a hypothesis that targeting Vasoactive intestinal and pituitary adenylate cyclase activating peptide (VPAC) receptors using ⁶⁴Cu-TP3805 can PET image UBC efficiently.

MATERIALS AND METHODS

Nineteen patients (44-84 years of age) scheduled for radical cystectomy, underwent VPAC positron emission tomography (PET) imaging prior to surgery. Sixteen had completed neoadjuvant chemotherapy prior to imaging. All 19 received ⁶⁴Cu-TP3805 (148 % ± 10% MBq) intravenously, and were imaged 60 to 90 minutes later. Standard uptake value (SUV)max for malignant lesions and SUVmean for normal tissues were determined and mean +/-SEM recorded. Following radical cystoprostatectomy, pelvic lymphadenectomy and urinary diversion imaging, results were compared with final surgical pathology.

RESULTS

⁶⁴Cu-TP3805 had no adverse events, negligible urinary excretion and rapid blood clearance. UBC PET images for residual disease were true positive in 11 patients and true negative in four. Of remaining 4, one had false positive and 3 had false negative scans, equating to 79% sensitivity (95%, CI 49%-95%), 80% specificity (95%, CI 28%-100%), 92% positive predictive value (95%, CI 62%-100%) and 57% negative predictive value (95%, CI 18%-90%).

CONCLUSIONS

These first in man results, in a group, heavily pretreated with neoadjuvant chemotherapy, indicate that VPAC PET imaging can identify UBC effeiciently and suggest, that VPAC PET can diagnose UBC in a treatment naïve cohort for accurate staging, guide biopsy and treatment in patients with suspected metastasis and determine response to therapy. Further investigation of this molecular imaging approach is warranted.

Differential expression of αVβ3 and αVβ6 integrins in prostate cancer progression

Neuroendocrine prostate cancer (NEPrCa) arises de novo or after accumulation of genomic alterations in pre-existing adenocarcinoma tumors in response to androgen deprivation therapies. We have provided evidence that small extracellular vesicles released by PrCa cells and containing the αVβ3 integrin promote neuroendocrine differentiation of PrCa in vivo and in vitro. Here, we examined αVβ3 integrin expression in three murine models carrying a deletion of PTEN (SKO), PTEN and RB1 (DKO), or PTEN, RB1 and TRP53 (TKO) genes in the prostatic epithelium; of these three models, the DKO and TKO tumors develop NEPrCa with a gene signature comparable to those of human NEPrCa. Immunostaining analysis of SKO, DKO and TKO tumors shows that αVβ3 integrin expression is increased in DKO and TKO primary tumors and metastatic lesions, but absent in SKO primary tumors. On the other hand, SKO tumors show higher levels of a different αV integrin, αVβ6, as compared to DKO and TKO tumors. These results are confirmed by RNA-sequencing analysis. Moreover, TRAMP mice, which carry NEPrCa and adenocarcinoma of the prostate, also have increased levels of αVβ3 in their NEPrCa primary tumors. In contrast, the αVβ6 integrin is only detectable in the adenocarcinoma areas. Finally, analysis of 42 LuCaP patient-derived xenografts and primary adenocarcinoma samples shows a positive correlation between αVβ3, but not αVβ6, and the neuronal marker synaptophysin; it also demonstrates that αVβ3 is absent in prostatic adenocarcinomas. In summary, we demonstrate that αVβ3 integrin is upregulated in NEPrCa primary and metastatic lesions; in contrast, the αVβ6 integrin is confined to adenocarcinoma of the prostate. Our findings suggest that the αVβ3 integrin, but not αVβ6, may promote a shift in lineage plasticity towards a NE phenotype and might serve as an informative biomarker for the early detection of NE differentiation in prostate cancer.

Improved Prognostic Stratification Using Circulating Tumor Cell Clusters in Patients with Metastatic Castration-Resistant Prostate Cancer

Simple Summary

Metastatic castration-resistant prostate cancer (mCRPC) is the most aggressive and deadly form of prostate cancer. As a bone-predominant metastatic disease, liquid biopsy-based biomarkers have advantages in monitoring cancer dynamics. Previous studies have demonstrated the associations between circulating tumor cells (CTCs) and mCRPC outcomes, but little is known about the prognostic value of CTC-clusters. In this study, we investigated the associations of CTCs and CTC-clusters with mCRPC prognosis, individually and jointly, using longitudinal samples. We confirmed the associations of CTC counts with mCRPC outcomes in both baseline and longitudinal analyses. Our results also showed that the presence of CTC-clusters alone had prognostic value and that CTC-clusters may further improve CTC-based prognostic stratification in mCRPC. Our findings suggest the potential of combing CTC and CTC-clusters as non-invasive means to monitor progression and predict survival in mCRPC and build a premise for in-depth genomic and molecular analyses of CTCs and CTC-clusters.

Abstract

Liquid biopsy-based biomarkers have advantages in monitoring the dynamics of metastatic castration-resistant prostate cancer (mCRPC), a bone-predominant metastatic disease. Previous studies have demonstrated associations between circulating tumor cells (CTCs) and clinical outcomes of mCRPC patients, but little is known about the prognostic value of CTC-clusters. In 227 longitudinally collected blood samples from 64 mCRPC patients, CTCs and CTC-clusters were enumerated using the CellSearch platform. The associations of CTC and CTC-cluster counts with progression-free survival (PFS) and overall survival (OS), individually and jointly, were evaluated by Cox models. CTCs and CTC-clusters were detected in 24 (37.5%) and 8 (12.5%) of 64 baseline samples, and in 119 (52.4%) and 27 (11.9%) of 227 longitudinal samples, respectively. CTC counts were associated with both PFS and OS, but CTC-clusters were only independently associated with an increased risk of death. Among patients with unfavorable CTCs (≥5), the presence of CTC-clusters signified a worse survival (log-rank p = 0.0185). mCRPC patients with both unfavorable CTCs and CTC-clusters had the highest risk for death (adjusted hazard ratio 19.84, p = 0.0072), as compared to those with <5 CTCs. Analyses using longitudinal data yielded similar results. In conclusion, CTC-clusters provided additional prognostic information for further stratifying death risk among patients with unfavorable CTCs.

Urine Extracellular Vesicle GATA2 mRNA Discriminates Biopsy Result in Men with Suspicion of Prostate Cancer

PURPOSE

Prostate specific antigen has limited performance in detecting prostate cancer. The transcription factor GATA2 is expressed in aggressive prostate cancer. We analyzed the predictive value of urine extracellular vesicle GATA2 mRNA alone and in combination with a multigene panel to improve detection of prostate cancer and high risk disease.

MATERIALS AND METHODS

GATA2 mRNA was analyzed in matched extracellular vesicles isolated from urines before and after prostatectomy (16) and paired urine and tissue prostatectomy samples (19). Extracellular vesicle GATA2 mRNA performance to distinguish prostate cancer and high grade disease was tested in training (52) and validation (165) cohorts. The predictive value of a multigene score including GATA2, PCA3 and TMPRSS2-ERG (GAPT-E) was tested in both cohorts.

RESULTS

Confirming its prostate origin, urine extracellular vesicle GATA2 mRNA levels decreased significantly after prostatectomy and correlated with prostate cancer tissue GATA2 mRNA levels. In the training and validation cohort GATA2 discriminated prostate cancer (AUC 0.74 and 0.66) and high grade disease (AUC 0.78 and 0.65), respectively. Notably, the GAPT-E score improved discrimination of prostate cancer (AUC 0.84 and 0.72) and high grade cancer (AUC 0.85 and 0.71) in both cohorts when compared with each biomarker alone and PT-E (PCA3 and TMPRSS2-ERG). A GAPT-E score for high grade prostate cancer would avoid 92.1% of unnecessary prostate biopsies, compared to 61.9% when a PT-E score is used.

CONCLUSIONS

Urine extracellular vesicle GATA2 mRNA analysis improves the detection of high risk prostate cancer and may reduce the number of unnecessary biopsies.

Implementation of Germline Testing for Prostate Cancer: Philadelphia Prostate Cancer Consensus Conference 2019

PURPOSE

Germline testing (GT) is a central feature of prostate cancer (PCA) treatment, management, and hereditary cancer assessment. Critical needs include optimized multigene testing strategies that incorporate evolving genetic data, consistency in GT indications and management, and alternate genetic evaluation models that address the rising demand for genetic services.

METHODS

A multidisciplinary consensus conference that included experts, stakeholders, and national organization leaders was convened in response to current practice challenges and to develop a genetic implementation framework. Evidence review informed questions using the modified Delphi model. The final framework included criteria with strong (> 75%) agreement (Recommend) or moderate (50% to 74%) agreement (Consider).

RESULTS

Large germline panels and somatic testing were recommended for metastatic PCA. Reflex testing-initial testing of priority genes followed by expanded testing-was suggested for multiple scenarios. Metastatic disease or family history suggestive of hereditary PCA was recommended for GT. Additional family history and pathologic criteria garnered moderate consensus. Priority genes to test for metastatic disease treatment included BRCA2, BRCA1, and mismatch repair genes, with broader testing, such as ATM, for clinical trial eligibility. BRCA2 was recommended for active surveillance discussions. Screening starting at age 40 years or 10 years before the youngest PCA diagnosis in a family was recommended for BRCA2 carriers, with consideration in HOXB13, BRCA1, ATM, and mismatch repair carriers. Collaborative (point-of-care) evaluation models between health care and genetic providers was endorsed to address the genetic counseling shortage. The genetic evaluation framework included optimal pretest informed consent, post-test discussion, cascade testing, and technology-based approaches.

CONCLUSION

This multidisciplinary, consensus-driven PCA genetic implementation framework provides novel guidance to clinicians and patients tailored to the precision era. Multiple research, education, and policy needs remain of importance.

Small extracellular vesicles modulated by αVβ3 integrin induce neuroendocrine differentiation in recipient cancer cells

The ability of small extracellular vesicles (sEVs) to reprogram cancer cells is well established. However, the specific sEV components able to mediate aberrant effects in cancer cells have not been characterized. Integrins are major players in mediating sEV functions. We have previously reported that the αVβ3 integrin is detected in sEVs of prostate cancer (PrCa) cells and transferred into recipient cells. Here, we investigate whether sEVs from αVβ3-expressing cells affect tumour growth differently than sEVs from control cells that do not express αVβ3. We compared the ability of sEVs to stimulate tumour growth, using sEVs isolated from PrCa C4-2B cells by iodixanol density gradient and characterized with immunoblotting, nanoparticle tracking analysis, immunocapturing and single vesicle analysis. We incubated PrCa cells with sEVs and injected them subcutaneously into nude mice to measure in vivo tumour growth or analysed in vitro their anchorage-independent growth. Our results demonstrate that a single treatment with sEVs shed from C4-2B cells that express αVβ3, but not from control cells, stimulates tumour growth and induces differentiation of PrCa cells towards a neuroendocrine phenotype, as quantified by increased levels of neuroendocrine markers. In conclusion, the expression of αVβ3 integrin generates sEVs capable of reprogramming cells towards an aggressive phenotype.

Clinical outcomes in men of diverse ethnic backgrounds with metastatic castration-resistant prostate cancer

BACKGROUND

We have shown previously in multivariable analysis that black men had 19% lower risk of death than white men with metastatic castration-resistant prostate cancer (mCRPC) treated with a docetaxel and prednisone (DP)-based regimen. The primary goal of this analysis was to compare progression-free survival (PFS), biochemical PFS, ≥50% decline in prostate-specific antigen (PSA) from baseline and objective response rate (ORR) in white, black and Asian men with mCRPC treated with a DP-based regimen.

PATIENTS AND METHODS

Individual patient data from 8820 mCRPC men randomized on nine phase III trials to a DP-containing regimen were combined. Race used in the analysis was based on self-report. End points were PFS, biochemical PSA, ≥50% decline in PSA from baseline and ORR. The proportional hazards and the logistic regression models were employed to assess the prognostic importance of race in predicting outcomes adjusting for established prognostic factors.

RESULTS

Of 8820 patients, 7528 (85%) were white, 500 (6%) were black, 424 were Asian (5%) and 368 (4%) had race unspecified. Median PFS were 8.3 [95% confidence interval (CI) 8.2-8.5], 8.2 (95% CI 7.4-8.8) and 8.3 (95% CI 7.6-8.8) months in white, black and Asian men, respectively. Median PSA PFS were 9.9 (95% CI 9.7-10.4), 8.5 (95% CI 8.0-10.3) and 11.1 (95% CI 9.9-12.5) months in white, black and Asian men, respectively.

CONCLUSIONS

We observed no differences in clinical outcomes by race and ethnic groups in men with mCRPC enrolled on these phase III clinical trials with DP.

Individual and joint effects of metformin and statins on mortality among patients with high-risk prostate cancer

BACKGROUND

Pre-clinical studies suggest that metformin and statins may delay prostate cancer (PCa) metastases; however, data in humans are limited. To the best of our knowledge, this is the first human study aimed to quantify the individual and joint effects of statin and metformin use among patients with high-risk PCa.

METHODS

This population-based retrospective cohort study identified patients from the Surveillance, Epidemiology, and End Results (SEER)-Medicare linked database. Exposure to metformin and statins was ascertained from Medicare Prescription Drug Event files. The association with all-cause and PCa mortality were evaluated using Cox proportional hazard model with competing causes of death, where propensity scores were used to adjusted imbalances in covariates across groups.

RESULTS

Based on 12 700 patients with high-risk PCa, statin alone or in combination with metformin was significantly associated with reduced all-cause mortality (Hazard Ratio [HR]: 0.89; 95% Confidence Interval [CI]: 0.83, 0.96; and HR: 0.75; 95% CI, 0.67-0.83, respectively) and PCa mortality (HR, 0.80; 95% CI: 0.69, 0.92) and 0.64; 95% CI, d 0.51-0.81, respectively. The effects were more pronounced in post-diagnostic users: combination use of metformin/statins was associated with a 32% reduction in all-cause mortality (95% CI, 0.57-0.80), and 54% reduction in PCa mortality (95% CI, 0.30-0.69). No significant association of metformin alone was observed with either all-cause mortality or PCa mortality.

CONCLUSIONS

Statin use alone or in combination with metformin was associated with lower all-cause and PCa mortality among high-risk patients, particularly in post-diagnostic settings; further studies are warranted.

Androgens and Overall Survival in Patients With Metastatic Castration-resistant Prostate Cancer Treated With Docetaxel

BACKGROUND

Pre-treatment androgen levels are associated with overall survival (OS) in patients with metastatic castration-resistant prostate cancer (CRPC) treated with androgen synthesis inhibitors. The current study sought to determine whether pre-treatment serum androgens predict clinical outcome among patients with metastatic CRPC treated with docetaxel chemotherapy.

MATERIALS AND METHODS

Data were obtained from 1050 men who were chemotherapy-naive prior to treatment with docetaxel, prednisone, and either bevacizumab or placebo (CALGB 90401). Pretreatment serum assays for testosterone, androstenedione, and dehydroepiandrosterone (DHEA) were performed with tandem liquid chromatography-mass spectrometry.

RESULTS

Median values for testosterone, androstenedione, and DHEA were 1.00, 13.50, and 8.12 ng/dL, respectively. The median was used to define the midpoint between low and high values. In univariate analysis, median OS for low versus high levels was 21.4 and 24.2 months for testosterone, 23.8 and 21.9 months for androstenedione, and 20.2 and 25.2 months for DHEA (P = NS). In multivariable analysis of all androgens, baseline DHEA was prognostic of ≥ 50% PSA decline from baseline (P = .008). In multivariable analysis adjusting for 10 known prognostic values and prior ketoconazole use for metastatic CRPC, a 10-unit increase in baseline testosterone increased risk of death (hazard ratio, 1.11; 95% confidence interval, 1.01-1.23; P = .039), whereas a 10-unit increase in androstenedione lowered risk of death (hazard ratio, 0.92; 95% confidence interval, 0.88-0.97; P = .001).

CONCLUSION

Consistent with prior studies, higher androstenedione levels in patients with metastatic CRPC treated with docetaxel are associated with improved survival. However pretreatment levels of other androgen levels are associated with varied effects on clinical outcome in chemotherapy-treated patients.

Germline genetic testing for inherited prostate cancer in practice: Implications for genetic testing, precision therapy, and cascade testing

BACKGROUND

Genetic testing capability and guidelines are rapidly expanding to assess inherited prostate cancer (PCA). Clinical genetic data from multigene testing can provide insights into the germline pathogenic variant (PV) spectrum and correlates in men with PCA unselected for metastatic disease to optimize identification of men for genetic evaluation and management.

METHODS

A retrospective cross-sectional analysis was conducted of de-identified clinical genetic testing data from a large commercial genetic testing laboratory in the US. ICD-10 claims codes were used to identify men with PCA, along with family history data. Gleason score was abstracted from test request forms. Overall PV rate among men with PCA was estimated, along with PVs in DNA repair genes. Family history and Gleason score association to germline DNA repair PVs was assessed using Fisher's exact test with correction for false-discovery.

RESULTS

As of August 2017, genetic results were available on 1328 men with PCA. Overall PV rate was 15.6%, with 10.9% of PV in DNA repair genes. PVs were most commonly identified in BRCA2 (4.5%), CHEK2 (2.2%), ATM (1.8%), and BRCA1 (1.1%). Breast cancer family history was significantly associated with germline DNA repair PVs (OR 1.89, [95%CI 1.33, 2.68], P = 0.003). Among men with Gleason score>= 6 (n = 706), Gleason> = 8 was significantly associated with DNA repair PVs (OR 1.85 [95%CI 1.22, 2.80], P = 0.004).

CONCLUSIONS

A substantial proportion of men with PCA unselected for metastatic disease carry germline DNA repair PVs. Breast cancer family history and high Gleason score are important predictors to identify men with PCA who may carry germline DNA repair PVs. Our findings support current NCCN guidelines and have implications for genetic assessment, therapeutic management, and cascade testing for men with PCA and their families.

Exosomal αvβ6 integrin is required for monocyte M2 polarization in prostate cancer

Therapeutic approaches aimed at curing prostate cancer are only partially successful given the occurrence of highly metastatic resistant phenotypes that frequently develop in response to therapies. Recently, we have described αvβ6, a surface receptor of the integrin family as a novel therapeutic target for prostate cancer; this epithelial-specific molecule is an ideal target since, unlike other integrins, it is found in different types of cancer but not in normal tissues. We describe a novel αvβ6-mediated signaling pathway that has profound effects on the microenvironment. We show that αvβ6 is transferred from cancer cells to monocytes, including β6-null monocytes, by exosomes and that monocytes from prostate cancer patients, but not from healthy volunteers, express αvβ6. Cancer cell exosomes, purified via density gradients, promote M2 polarization, whereas αvβ6 down-regulation in exosomes inhibits M2 polarization in recipient monocytes. Also, as evaluated by our proteomic analysis, αvβ6 down-regulation causes a significant increase in donor cancer cells, and their exosomes, of two molecules that have a tumor suppressive role, STAT1 and MX1/2. Finally, using the Pten^pc-/- prostate cancer mouse model, which carries a prostate epithelial-specific Pten deletion, we demonstrate that αvβ6 inhibition in vivo causes up-regulation of STAT1 in cancer cells. Our results provide evidence of a novel mechanism that regulates M2 polarization and prostate cancer progression through transfer of αvβ6 from cancer cells to monocytes through exosomes.

Role of Genetic Testing for Inherited Prostate Cancer Risk: Philadelphia Prostate Cancer Consensus Conference 2017

Purpose Guidelines are limited for genetic testing for prostate cancer (PCA). The goal of this conference was to develop an expert consensus-driven working framework for comprehensive genetic evaluation of inherited PCA in the multigene testing era addressing genetic counseling, testing, and genetically informed management. Methods An expert consensus conference was convened including key stakeholders to address genetic counseling and testing, PCA screening, and management informed by evidence review. Results Consensus was strong that patients should engage in shared decision making for genetic testing. There was strong consensus to test HOXB13 for suspected hereditary PCA, BRCA1/2 for suspected hereditary breast and ovarian cancer, and DNA mismatch repair genes for suspected Lynch syndrome. There was strong consensus to factor BRCA2 mutations into PCA screening discussions. BRCA2 achieved moderate consensus for factoring into early-stage management discussion, with stronger consensus in high-risk/advanced and metastatic setting. Agreement was moderate to test all men with metastatic castration-resistant PCA, regardless of family history, with stronger agreement to test BRCA1/2 and moderate agreement to test ATM to inform prognosis and targeted therapy. Conclusion To our knowledge, this is the first comprehensive, multidisciplinary consensus statement to address a genetic evaluation framework for inherited PCA in the multigene testing era. Future research should focus on developing a working definition of familial PCA for clinical genetic testing, expanding understanding of genetic contribution to aggressive PCA, exploring clinical use of genetic testing for PCA management, genetic testing of African American males, and addressing the value framework of genetic evaluation and testing men at risk for PCA-a clinically heterogeneous disease.

Indoleamine 2,3-dioxygenase (IDO): Biology and Target in Cancer Immunotherapies

Indoleamine 2,3-dioxygenase (IDO) is a heme-containing oxidoreductase that catalyzes the initial and rate-limiting step in the breakdown of non-dietary tryptophan. The biology and immunomodulatory role for IDO is discussed in this review with a focus on its interaction with immune cells and its potential therapeutic target in the clinic. IDO has been revealed to be a central regulator of immune responses in a broad variety of physiological and pathological settings, mostly serving as a multifaceted negative feedback mechanism, to self-regulate immune responses. IDO is considered a therapeutic target in cancer and the use of IDO inhibitors as single agent or in combination with other treatment modalities are under active investigation.

Abstract 5874: Cdk4/6 kinase inhibitor resistance in prostate cancer

Non-organ confined prostate cancer (PCa) is often effectively, but only transiently treated by targeting the androgen receptor (AR) signaling axis through androgen depletion strategies, often coupled with AR antagonists. Unfortunately, disease recurs within a median of 3-4 years, presenting as castration resistant PCa (CRPC), for which there are limited therapeutic options. This emphasizes the need for more efficacious drugs and a patient-tailored approach towards cancer therapy to improve disease outcome. One class of drugs currently tested clinically, Cdk4/6 kinase inhibitors, blocks phosphorylation of the retinoblastoma (RB) tumor suppressor, thereby boosting its function, and likely preventing castration resistance. As Cdk4/6 inhibitor resistance has already been reported in other cancers, some PCa patients are anticipated to develop drug resistance. Here, we created palbociclib-resistant PCa cell models by continuously culturing them in presence of the drug to unravel mechanisms of acquired resistance, and assessed them for cross-resistance to ribociclib and response to other therapeutics. While the parental PCa cell models, Cdk4/6 inhibitors efficiently induce a G1 cell cycle arrest, the resistant cell lines bypass this cell cycle checkpoint. Although loss of RB is a known mechanism for Cdk4/6i resistance, none of the models lost RB expression. Strikingly, these originally hormone-sensitive cell lines, upon developing Cdk4/6 inhibitor resistance display altered response to selected therapeutic regimens. Mechanisms of resistance, as informed by Whole Exome Sequencing and RNASeq, will be discussed.

Citation Format: Renee de Leeuw, Matthew J. Schiewer, Christopher McNair, Michael A. Augello, Akihiro Yoshida, Edward S. Hazard, Sean Courtney, Gerard T. Hardiman, Justin Drake, Felix Y. Feng, Scott Tomlins, Maha H. Hussain, J Alan Diehl, William K. Kelly, Karen E. Knudsen. Cdk4/6 kinase inhibitor resistance in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5874. doi:10.1158/1538-7445.AM2017-5874

Inherited Mutations in Men Undergoing Multigene Panel Testing for Prostate Cancer: Emerging Implications for Personalized Prostate Cancer Genetic Evaluation

PURPOSE

Multigene panels are commercially available for the evaluation of prostate cancer (PCA) predisposition, which necessitates tailored genetic counseling (GC) for men. Here we describe emerging results of Genetic Evaluation of Men, prospective multigene testing study in PCA to inform personalized genetic counseling, with emerging implications for referrals, cancer screening, and precision therapy.

PATIENTS AND METHODS

Eligibility criteria for men affected by or at high risk for PCA encompass age, race, family history (FH), and PCA stage/grade. Detailed demographic, clinical, and FH data were obtained from participants and medical records. Multigene testing was conducted after GC. Mutation rates were summarized by eligibility criteria and compared across FH data. The 95% CI of mutation prevalence was constructed by using Poisson distribution.

RESULTS

Of 200 men enrolled, 62.5% had PCA. Eleven (5.5%; 95% CI, 3.0% to 9.9%) had mutations; 63.6% of mutations were in DNA repair genes. FH of breast cancer was significantly associated with mutation status (P = .004), and FH that met criteria for hereditary breast and ovarian cancer syndrome was significantly associated with PCA (odds ratio, 2.33; 95% CI, 1.05 to 5.18). Variants of uncertain significance were reported in 70 men (35.0%). Among mutation carriers, 45.5% had personal/FH concordant with the gene. A tailored GC model was developed based on emerging findings.

CONCLUSION

Multigene testing for PCA identifies mutations mostly in DNA repair genes, with implications for precision therapy. The study highlights the importance of comprehensive genetic evaluation for PCA beyond metastatic disease, including early-stage disease with strong FH. Detailed FH is important for referrals of men for genetic evaluation. The results inform precision GC and cancer screening for men and their male and female blood relatives.

Abstract 23: Caloric restriction slows tumor growth and metastases in both hormone-sensitive and hormone-resistant prostate cancers

Introduction: The purpose of this study is to assess the effect of caloric restriction (CR) on prostate cancer (PCa) tumor burden, proliferation, and overall survival with and without radiation treatment (RT). Additionally, we determined if the beneficial effect of CR noted are due to a reduction in pro-inflammatory markers hypothesized to enhance PCa tumorgenesis.

Methods: To assess the effect of CR in vivo, 40 male 12 week-old NCRNu-M mice were injected with LNCaP or PC3 tumor cells. Once tumors were palpable, mice were randomly assigned to one of four treatment groups in cohorts of 10: ad libitum (AL) diet, 6.5Gy of radiation (RT), 30% reduction in caloric intake (CR), or CR+RT. Tumor growth and proliferation rate were measured 3 times per week via calipers and live bioluminescent imaging. Additionally, PCa tumor tissue were analyzed to determine if CR can exert its effect on tumor growth and metastases via IGF-1R signaling pathway.

Results: Adding CR to RT decreased tumor progression. In the PC3 murine model, when compared to AL, RT reduced tumor size by 22%, 77% with CR, and 80% with CR+RT. In the LNCaP murine model, compared with AL, CR reduced tumor size by 49% and a 55% reduction with CR+RT. Primary tumor formation began 9 weeks post tumor injection in the radiated cohort and was delayed to 15 weeks post tumor injection in the CR and CT+ RT cohorts. Additionally, time to metastasis was delayed with CR (86 days to metastasis in AL, 93 with RT, and 108 when combining CR+RT). Molecularly, CR decreased multiple members of the IGF-1R signaling pathway. The total IGF-1 and IGF-1R levels exhibited 50% reduction with CR and CR+RT but total INSR levels. CR also induced a significant decrease of pGSK3β and pAKT levels.

Conclusions: For the first time, we have shown that decreasing calories by 30% in both hormone-sensitive and hormone-refractory prostate cancer models, enhance the efficacy of radiation. Our experiments show that even CR alone and in combination with RT can improve PCa tumor proliferation rate, tumor burden, time to metastasis, and overall survival. We hypothesize that these changes are in part, due to the decrease of the IGF-1R signaling pathway. We propose that CR may be used as a novel therapeutic intervention to enhance outcomes of radiation treatment by altering the molecular profile of prostate tumors.

Citation Format: Robert S. Gitman, Meredith LaRose, Edouard J. Trabulsi, Ajay Palagani, Tiziana DeAngelis, William K. Kelly, Leonard G. Gomella, Nicole L. Simone. Caloric restriction slows tumor growth and metastases in both hormone-sensitive and hormone-resistant prostate cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 23.

Abstract 2037: A discovery study to identify clinical and genetic risk factors for bevacizumab (BEV)-related gastrointestinal (GI) hemorrhage (HEM) in metastatic castration-resistant prostate cancer (mCRPC) patients (pts) treated on CALGB 90401 (Alliance)

Background: Treatment-related GI HEM is a major health concern with few known predictive risk factors. The objective of this analysis was to discover clinical and genetic factors that modulate GI HEM risk in a large randomized phase III study.

Methods: Chemotherapy-naïve mCRPC pts were randomized 1:1 to receive docetaxel and prednisone ± BEV once every 21 days for up to two years (N = 1008). Cause-specific time-to-event analysis using a Cox regression model was used to investigate the association between grade 2+ GI HEM (designated as at least “probably” related to therapy) and BEV, age, history (hx) of peptic ulcer disease (PUD), hx of HEM, antiplatelet/anticoagulant use, hx of smoking, and hemoglobin. Genetically-defined Caucasian pts who provided consent for the genomic companion study (CALGB 60404) were genotyped using the Illumina HumanHap610-Quad platform (N = 616). Log rank test was used to investigate the association of single nucleotide polymorphisms (SNPs) and GI HEM, and results were adjusted for significant clinical covariates.

Results: The overall incidence of grade 2+ GI HEM was 9.5% (48/503) and 3.8% (19/505) in the BEV and placebo arms, respectively. Of the clinical covariates, only BEV (HR = 5.77; 95% CI 2.20-15.11; P&lt;0.001) and age (HR = 1.06; 95% CI 1.01-1.11; P = 0.01) were significantly associated with GI HEM in the multivariable analysis, while a trend was noted for hx of PUD (P = 0.08). Of 498,081 SNPs tested, one intergenic SNP (rs1478947; HR 6.26; 95% CI 3.00-14.4; P = 9.40 × 10-8) surpassed Bonferroni-corrected significance (1.0 × 10-7) for association with GI HEM (minor allele frequency = 0.06). The incidence of GI HEM in the BEV arm was 33.3% (13/39) and 6.2% (17/275) for pts with the AA/AG and GG genotypes, while the incidence in the placebo arm was 2.9% (1/35) and 1.9% (5/267), respectively.

Conclusion: BEV, age, and one putative intergenic SNP (rs1478947) were associated with cause-specific GI HEM risk in CALGB 90401. The effect of rs1478947 appears to be specific to pts receiving BEV. Although the mechanism by which rs1478947 increases GI HEM risk remains unclear, rs1478947 is in complete LD (r2 = 1) with rs1478948, variations of which may alter the binding motif for transcription factor hepatocyte nuclear factor-4 (HNF4). HNF4 exerts a major regulatory effect on clotting factor VII (fVII) expression and function. Altered binding of HNF4 to fVII promoter may result in reduced fVII function and an increased risk of bleeding. It is unclear how much weight each identified risk factor contributes to the overall incidence of GI HEM, which in absolute terms was not dramatically different between arms. Exploratory studies from large trials of BEV-treated pts are needed to better understand the genetic contribution to and biological basis of GI HEM. Support: U10CA180821

Citation Format: Jai N. Patel, Chen Jiang, Kouros Owzar, Daniel L. Hertz, Flora A. Mulkey, William K. Kelly, Susan Halabi, Yoichi Furukawa, Cameron Lassiter, Susan G. Dorsey, Paula N. Friedman, Eric J. Small, Michael A. Carducci, John F. Mahoney, Michael J. Kelley, Yusuke Nakamura, Michiaki Kubo, Mark J. Ratain, Michael J. Morris, Howard L. McLeod. A discovery study to identify clinical and genetic risk factors for bevacizumab (BEV)-related gastrointestinal (GI) hemorrhage (HEM) in metastatic castration-resistant prostate cancer (mCRPC) patients (pts) treated on CALGB 90401 (Alliance). [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2037.

Bevacizumab and the risk of arterial and venous thromboembolism in patients with metastatic, castration-resistant prostate cancer treated on Cancer and Leukemia Group B (CALGB) 90401 (Alliance)

BACKGROUND

Bevacizumab is associated with an increased risk of arterial thromboembolism (ATE); however, its effect on venous thromboembolism (VTE) remains controversial. Scant data exist on the factors that increase the risk of ATE/VTE in patients with prostate cancer. The authors investigated the association of bevacizumab treatment and clinical factors with ATE/VTE risk in patients who were treated on Cancer and Leukemia Group B (CALGB) trial 90401.

METHODS

Patients with metastatic, castration-resistant prostate cancer were randomized to receive docetaxel and prednisone with or without bevacizumab once every 21 days. Cycle-to-event Cox regression models were used to investigate the association of bevacizumab with the incidence of grade 3 or greater (≥ 3) ATE and VTE. Age, prior ATE/VTE, baseline antiplatelet/anticoagulant use, and VTE risk score (based on leukocyte count, hemoglobin, platelet count, body mass index, and tumor location) were evaluated in univariate and multivariable analyses.

RESULTS

Of 1008 randomized patients, the odds of experiencing grade ≥ 3 ATE were significantly greater in those who received bevacizumab compared with those who received placebo (odds ratio, 2.79; P = .02), whereas an opposite trend was noted for grade ≥ 3 VTE (odds ratio, 0.60; P = .08). In the multivariable analysis, bevacizumab treatment (hazard ratio [HR], 3.00; P = .01) and age (HR, 1.06; P = .02) were significantly associated with the risk of ATE; whereas age (HR, 1.05; P = .01) and VTE risk score (HR, 1.83; P = .03) were significantly associated with the risk of VTE.

CONCLUSIONS

Bevacizumab was significantly associated with a greater risk of ATE in patients with metastatic, castration-resistant prostate cancer, but it was not significantly associated with the risk of VTE. Understanding clinical factors that increase the risk for experiencing ATE/VTE is essential to mitigate the risks and reduce the burden of these prevalent complications in cancer care.

Novel actions of next-generation taxanes benefit advanced stages of prostate cancer

PURPOSE

To improve the outcomes of patients with castration-resistant prostate cancer (CRPC), there is an urgent need for more effective therapies and approaches that individualize specific treatments for patients with CRPC. These studies compared the novel taxane cabazitaxel with the previous generation docetaxel, and aimed to determine which tumors are most likely to respond.

EXPERIMENTAL DESIGN

Cabazitaxel and docetaxel were compared via in vitro modeling to determine the molecular mechanism, biochemical and cell biologic impact, and cell proliferation, which was further assessed ex vivo in human tumor explants. Isogenic pairs of RB knockdown and control cells were interrogated in vitro and in xenograft tumors for cabazitaxel response.

RESULTS

The data herein show that (i) cabazitaxel exerts stronger cytostatic and cytotoxic response compared with docetaxel, especially in CRPC; (ii) cabazitaxel induces aberrant mitosis, leading to pyknotic and multinucleated cells; (iii) taxanes do not act through the androgen receptor (AR); (iv) gene-expression profiling reveals distinct molecular actions for cabazitaxel; and (v) tumors that have progressed to castration resistance via loss of RB show enhanced sensitivity to cabazitaxel.

CONCLUSIONS

Cabazitaxel not only induces improved cytostatic and cytotoxic effects, but also affects distinct molecular pathways, compared with docetaxel, which could underlie its efficacy after docetaxel treatment has failed in patients with CRPC. Finally, RB is identified as the first potential biomarker that could define the therapeutic response to taxanes in metastatic CRPC. This would suggest that loss of RB function induces sensitization to taxanes, which could benefit up to 50% of CRPC cases.

Abstract 3841: Bevacizumab (BEV) and risk of arterial (ATE) and venous thromboembolism (VTE) in metastatic castration-resistant prostate cancer (mCRPC) patients treated on CALGB 90401(ALLIANCE)

Background BEV is associated with an increased risk of ATE, however, its effect on VTE remains controversial. We investigated the association of BEV treatment and clinical risk factors with the incidence of ATE and VTE in a large randomized phase III study.

Methods mCRPC patients were randomized to receive docetaxel and prednisone with or without BEV once every 21 days. Competing risks cycle-to-event Cox regression models were used to investigate the association of BEV on the incidence of grade 3 or higher (3+) ATE (“cardiac ischemia/infarction” or “CNS ischemia”) and VTE (“thrombosis/thrombus/embolism”). Age, prior ATE/VTE, baseline antiplatelet/anticoagulant and VTE risk score were evaluated in univariable and multivariable analyses.

Results The analysis included 800 patients. The odds of experiencing grade 3+ ATE was significantly greater in BEV treated patients compared to placebo (OR 4.16, P=0.006; 4.02% [16/398] and 1.00% [4/402], respectively). The odds of experiencing grade 3+ VTE was lower in BEV treated patients compared to placebo (OR=0.57, P=0.08; 4.52% [18/398] and 7.71% [31/402], respectively). In the multivariable analysis, BEV treatment (HR=4.28; P=0.009) and prior ATE (HR=2.71; P=0.047) were associated with increased ATE, while age (HR=1.05; P=0.009) and VTE risk score (HR=2.24; P=0.007), but not BEV treatment (HR=0.62; P=0.11), were associated with increased VTE (Table 1).

Conclusion Due to the lack of survival benefit noted in the clinical trial, these results further reinforce the recommendation for not using BEV in this patient population, as it also placed patients at a significantly greater risk for ATE. However, the influence on VTE, if any, was a decreased risk. Understanding the risk factors for ATE and VTE is essential to mitigate risks and reduce the burden of these prevalent complications in cancer care.

Table 1 Risk of ATE and VTE by treatment arm and clinical risk factors

Table 1Risk of ATE and VTE by treatment arm and clinical risk factorsATERisk factorVTECause-specific HRCause-specific HR(95% CI)(95% CI)P-valueP-valueMultivariableUnivariableUnivariableMultivariable4.283.96BEV treatment0.560.62(1.42-12.84)(1.32-11.85)(0.31-1.00)(0.35-1.12)0.0090.0140.0510.111.051.05Agea1.041.05(0.99-1.11)(1.00-1.11)(1.01-1.08)(1.01-1.09)0.120.070.020.0092.713.48Prior thrombosis1.030.97(1.01-7.26)(1.33-9.07)(0.25-4.26)(0.23-4.07)0.0470.010.960.971.631.87Baseline antiplatelet/ anticoagulant 0.940.82(0.62-4.27)(0.72-4.86)(0.53-1.67)(0.46-1.47)0.320.20.850.51N/AN/AVTE risk scoreb2.012.24(1.14-3.54)(1.25-4.01)0.0150.007aAge as a continuous variablebLow, intermediate, or high risk if 0, 1-2, or ≥ 3 risk factors (hemoglobin &lt; 10 g/dL, platelet count ≥ 350,000/µl, leukocyte count &gt; 11,000/µl, body mass index ≥ 35 kg/m2), respectively; low vs. intermediate/high.

Citation Format: Jai N. Patel, Chen Jiang, Daniel L. Hertz, Flora A. Mulkey, Paula N. Friedman, Susan Halabi, Mark J. Ratain, Michael J. Morris, Eric J. Small, Kouros Owzar, William K. Kelly, Howard L. McLeod. Bevacizumab (BEV) and risk of arterial (ATE) and venous thromboembolism (VTE) in metastatic castration-resistant prostate cancer (mCRPC) patients treated on CALGB 90401(ALLIANCE). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3841. doi:10.1158/1538-7445.AM2014-3841

Abstract 4255: Imprintome-wide methylation alteration in human cancer: from occupation to clinic

Background: Exposure to light at night through shiftwork is a widespread occupational exposure which has been associated with cancer risk. In this study, we sought to investigate whether this association may be mediated in part by disruption of genomic imprinting patterns.

Methods: Using an Illumina Infinium Methylation Assay, we measured methylation differences at 397 CpG sites in the promoter regions of 56 imprinted genes in DNA isolated from 10 long-term shiftworkers as compared to 10 age- and folate intake-matched day workers. We subsequently measured methylation differences at these same CpG sites in a pooled sample of 12 pairs of prostate tumor as compared to adjacent normal tissue. Top differentially methylated loci were validated using the Sequenom EpiTYPER methylation assay.

Results: Among long-term shiftworkers, statistically significant hypermethylation was observed at 20 CpG sites and statistically significant hypomethylation was observed at 30 CpG sites relative to matched day workers (P &lt; 0.05). This differential methylation was observed across 26 unique genes, 15 of which contained CpG sites also statistically significantly differentially methylated between prostate tumor and adjacent normal tissue (P &lt; 0.05). In total, statistically significant hypermethylation was observed at 52 CpG sites and hypomethylation was observed at 17 CpG sites in prostate tumor relative to adjacent normal tissue. Of particular interest was the disruption of methylation patterns at TP73, an important component of the cellular apoptotic response, among both shiftworkers and in prostate tumor tissue. Tumor suppressor genes SLC22A18 and WT1 also demonstrated altered methylation patterns in both comparison groups. A query of publicly available expression array data returned several studies demonstrating statistically significant differential expression levels of these three genes in prostate cancer tissue relative to tissue from healthy controls.

Conclusion: In exploring the methylation patterns at normally imprinted genes among a set of shiftworkers and a sample of prostate tumor tissue, we have identified a set of 15 genes within which differential methylation is observed in comparison to day workers and adjacent normal prostate tissue, respectively. This altered methylation was observed at several important tumor suppressor genes, against a background of widespread changes in methylation at imprinted genes in both comparison groups. Taken together, these data suggest that loss of normal patterns of methylation at imprinted genes may be an important mechanism by which occupational exposure to light at night drives the increased risk of cancer development, and warrants further exploration.

Citation Format: Daniel I. Jacobs, Johnni Hansen, Alan Fu, Richard G. Stevens, Anne Tjonneland, Ulla B. Vogel, Tongzhang Zheng, Yingying Mao, William K. Kelly, Yong Zhu. Imprintome-wide methylation alteration in human cancer: from occupation to clinic. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4255. doi:10.1158/1538-7445.AM2013-4255

c-Met is a prognostic marker and potential therapeutic target in clear cell renal cell carcinoma

BACKGROUND

Activation of the c-Met pathway occurs in a range of malignancies, including papillary renal cell carcinoma (RCC). Its activity in clear cell RCC is less clear. We investigated c-Met expression and inhibition in a large cohort of RCC tumors and cell lines.

METHODS

c-Met protein expression was determined by automated quantitative analysis (AQUA) on a tissue microarray (TMA) constructed from 330 RCC tumors paired with adjacent normal renal tissue. c-Met expression and selective inhibition with SU11274 and ARQ 197 were studied in clear cell RCC cell lines.

RESULTS

Higher c-Met expression was detected in all RCC subtypes than in the adjacent normal renal tissue (P < 0.0001). Expression was highest in papillary and sarcomatoid subtypes, and high-grade and stage tumors. Higher c-Met expression correlated with worse disease-specific survival [risk ratio = 1.36; 95% confidence interval (CI) 1.08-1.74; P = 0.0091] and was an independent predictor of survival, maintained in clear cell subset analyses. c-Met protein was activated in all cell lines, and proliferation (and colony formation) was blocked by SU11274 and ARQ 197.

CONCLUSIONS

c-Met is associated with poor pathologic features and prognosis in RCC. c-Met inhibition demonstrates in vitro activity against clear cell RCC. Further study of ARQ 197 with appropriate biomarker studies in RCC is warranted.

Targeting angiogenesis as a promising modality for the treatment of prostate cancer

Antiangiogenic therapy has been successful for the treatment of solid tumors. Several strategies have been used to target angiogenesis in prostate cancer. These strategies include blocking proangiogenic factors via monoclonal antibodies or small molecule inhibitors targeting downstream signaling effector pathways, or using agents with immune-modulatory effects. This review examines the general concepts of tumor angiogenesis and the key clinical trials that have used these agents and other novel biologics in prostate cancer. Targeting angiogenesis is still a promising treatment strategy in prostate cancer with a rational trial design and combination approach.

Efficacy of peripheral androgen blockade in prostate cancer patients with biochemical failure after definitive local therapy: results of Cancer and Leukemia Group B (CALGB) 9782

BACKGROUND

The treatment for prostate cancer patients with biochemical failure after local therapy remains controversial. Peripheral androgen blockade using a combination of a 5-alpha reductase inhibitor and an antiandrogen may allow control of the prostate-specific antigen (PSA). Because testosterone levels are not suppressed, this approach may be associated with less morbidity than conventional gonadal androgen suppression.

METHODS

All patients had undergone previous definitive local therapy and had evidence of a rising PSA >1ng/mL, with no evidence of recurrent disease. Patients received both finasteride, 5 mg orally per day, and flutamide, 250 mg orally 3× a day. Patients were followed for a PSA response and quality of life assessment.

RESULTS

Ninety-nine of 101 accrued patients were eligible. A ≥80% PSA decline was seen in 96 (96%) patients. The median time to PSA progression was 85 months. With a median follow-up of 10 years, the median survival time had not been reached, and the 5-year overall survival rate was 87%. Toxicity was mild, with 18 patients stopping for toxicity; 15 had diarrhea, 4 had gynecomastia, and 3 had transaminase elevation. Baseline Functional Assessment of Cancer Therapy Prostate Module and Treatment Outcome Index scores decreased by 5 points each at 6 months after enrollment.

CONCLUSIONS

The use of the finasteride/flutamide combination is feasible, and results in PSA declines of ≥80% in 96% of patients with serologic progression after definitive local therapy. There were no unexpected toxicities, and the change in quality of life was mild. Further evaluation of this or a similar regimen in a controlled clinical trial is warranted.

Phase 1 trial of high-dose exogenous testosterone in patients with castration-resistant metastatic prostate cancer

BACKGROUND

Growth of selected castration-resistant prostate cancer (CRPC) cell lines and animal models can be repressed by reexposure to androgens. Low doses of androgens, however, can stimulate tumor growth.

OBJECTIVE

We performed a phase 1 clinical trial to determine the safety of high-dose exogenous testosterone in patients with castration-resistant metastatic prostate cancer (CRMPC).

DESIGN, SETTING, AND PARTICIPANTS

Patients with progressive CRMPC who had been castrate for at least 1 yr received three times the standard replacement dose of transdermal testosterone.

INTERVENTION

Cohorts of 3-6 patients received testosterone for 1 wk, 1 mo, or until disease progression.

MEASUREMENTS

Toxicities, androgen levels, prostate-specific antigen (PSA) assays, computed tomography (CT) scans, bone scintigraphy, positron emission tomography (PET) scans, and metastatic tumor biopsy androgen receptor levels were assessed.

RESULTS AND LIMITATIONS

Twelve patients were treated-three in cohorts 1 and 2 and six in cohort 3. No pain flares were noted. One patient came off study because of epidural disease, which was treated with radiation. Average testosterone levels were within normal limits, although dihydrotestosterone (DHT) levels on average were supraphysiologic in cohort 3. One patient achieved a PSA decline of >50% from baseline. No objective responses were seen. For cohort 3, median time on treatment was 84 d (range: 23-247 d).

CONCLUSIONS

We have demonstrated that patients with CRMPC can be safely treated in clinical trials using high-dose exogenous testosterone. Patients did not, on average, achieve sustained supraphysiologic serum testosterone levels. Future studies should employ strategies to maximize testosterone serum levels, use contemporary methods of identifying patients with androgen receptor overexpression, and utilize PSA Working Group II Consensus Criteria clinical trial end points.

TRIAL REGISTRATION

ClinicalTrials.gov; NCT00006044.

Efficacy of carboplatin-taxane combinations in the management of castration-resistant prostate cancer: a pooled analysis of seven prospective clinical trials

BACKGROUND

Docetaxel is associated with prolonged survival in castration-resistant prostate cancer (CRPC). Platinum compounds have modest but distinct single-agent activity. Carboplatin may have greatest potential for benefit when combined with taxanes. We investigated whether there is a subset of patients with CRPC for whom the efficacy of combination taxane-estramustine-carboplatin (TEC) chemotherapy may be greatest.

PATIENTS AND METHODS

Individual patient data (n = 310) were obtained from seven trials using TEC chemotherapy. Prostate-specific antigen (PSA) response was defined as > or = 50% post-therapy decline from baseline. Overall survival was defined from baseline to death from any cause. Logistic and Cox regression were used to investigate heterogeneity in outcome to TEC by patient and disease characteristics. Predicted survival probabilities were calculated from the Halabi Cancer and Leukemia Group B (CALGB) nomogram.

RESULTS

The pooled PSA response proportion was 69% [95% confidence interval (CI) 56% to 80%]. There was no evidence of differential PSA response by disease characteristics. Established prognostic factors were associated with survival. The pooled 12-month survival estimate of 79% (95% CI 71% to 84%) was higher than the median 59% 12-month nomogram-predicted survival.

CONCLUSIONS

TEC chemotherapy has significant clinical activity in CRPC. A randomized, controlled trial evaluating the addition of carboplatin to taxane-based chemotherapy is needed to elucidate the value of carboplatin in CRPC.

Phase I study of samarium-153 lexidronam with docetaxel in castration-resistant metastatic prostate cancer

PURPOSE

Early studies of patients with castration-resistant metastatic prostate cancer (CRMPC) suggest that chemotherapy administered with a dose of a bone-seeking radiopharmaceutical is superior to chemotherapy alone. To build on this strategy and fully integrate a repetitively dosed bone-seeking radiopharmaceutical into a contemporary chemotherapy regimen, we conducted a phase I study of docetaxel and samarium-153 ((153)Sm) lexidronam.

PATIENTS AND METHODS

Men with progressive CRMPC were eligible. Cohorts of three to six patients were defined by dose escalations as follows: docetaxel 65, 70, 75, 75, 75 mg/m(2) and (153)Sm ethylenediaminetetramethylenephosphonate (EDTMP) 0.5, 0.5, 0.5, 0.75, 1 mCi/kg. Each cycle lasted a minimum of 6 (cohorts 1 through 5) or 9 (cohort 6) weeks. Docetaxel was administered on days 1 and 22 (and day 43 for cohort 6), and (153)Sm-EDTMP was administered on day -1 to 1 of each cycle. Patients with acceptable hematologic toxicities were eligible to receive additional cycles until progression.

RESULTS

Twenty-eight men were treated in six cohorts. Maximum-tolerated dose was not reached, because full doses of both agents were well tolerated, even using an every-6-week dosing schedule of (153)Sm-EDTMP. Patients received an average of 5.6 docetaxel doses (range, one to 13 doses) and 2.9 (153)Sm-EDTMP doses (range, one to six doses). Fifteen patients demonstrated a more than 50% decline in prostate-specific antigen. Treatment significantly reduced indices of bone deposition and resorption.

CONCLUSION

Docetaxel and (153)Sm-EDTMP can be combined safely at full doses over repeated cycles. Responses were seen in the small group of patients with taxane-resistant disease tested. The optimal phase II doses for patients with taxane-naïve disease may differ from those optimal for patients with taxane-resistant disease.

Clinical Experience With Intravenous and Oral Formulations of the Novel Histone Deacetylase Inhibitor Suberoylanilide Hydroxamic Acid in Patients With Advanced Hematologic Malignancies

Purpose

To document the toxicity and activity of the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) in patients with pretreated hematologic malignancies.

Patients and Methods

Two formulations of SAHA (intravenous [IV] and oral) have been assessed in two consecutive phase I trials. In both trials, dose escalation was performed in parallel and independently in patients with solid tumors and hematologic malignancies. Eligible patients were required to have adequate hepatic and renal function, an absolute neutrophil count ≥ 500/μL and a platelet count more than 25,000/mL. All patients provided informed consent for study inclusion.

Results

A total of 39 patients with hematologic malignancy were enrolled (14 on IV SAHA and 25 on oral SAHA), of whom 35 were treated. The spectrum of diseases included patients with diffuse large B-cell lymphoma (n = 12), Hodgkin's disease (HD; n = 12), multiple myeloma (n = 2), T-cell lymphoma (n = 3), mantle cell lymphoma (n = 2), small lymphocytic lymphoma (n = 2), and myeloid leukemia (n = 2). Major adverse events with the oral formulation included fatigue, diarrhea, anorexia, and dehydration, whereas myelosuppression and thrombocytopenia were more prominent with the IV formulation. Typically, the hematologic toxicities resolved shortly after SAHA was stopped. There was no neutropenic fever or neutropenic sepsis. Reduction in measurable tumor was observed in five patients. One patient with transformed small lymphocytic lymphoma met criteria for complete response, whereas another met the criteria for partial response (PR). One patient with refractory HD had a PR, whereas three patients had stable disease for up to 9 months.

Conclusion

These results suggest that SAHA has activity in hematologic malignancies including HD and select subtypes of non-Hodgkin's lymphoma.