Rhonda L. Bitting

Circulating Tumor Cells from Patients with Advanced Prostate and Breast Cancer Display Both Epithelial and Mesenchymal Markers

During cancer progression, malignant cells undergo epithelial-mesenchymal transitions (EMT) and mesenchymal-epithelial transitions (MET) as part of a broad invasion and metastasis program. We previously observed MET events among lung metastases in a preclinical model of prostate adenocarcinoma that suggested a relationship between epithelial plasticity and metastatic spread. We thus sought to translate these findings into clinical evidence by examining the existence of EMT in circulating tumor cells (CTC) from patients with progressive metastatic solid tumors, with a focus on men with castration-resistant prostate cancer (CRPC) and women with metastatic breast cancer. We showed that the majority (>80%) of these CTCs in patients with metastatic CRPC coexpress epithelial proteins such as epithelial cell adhesion molecule (EpCAM), cytokeratins (CK), and E-cadherin, with mesenchymal proteins including vimentin, N-cadherin and O-cadherin, and the stem cell marker CD133. Equally, we found that more than 75% of CTCs from women with metastatic breast cancer coexpress CK, vimentin, and N-cadherin. The existence and high frequency of these CTCs coexpressing epithelial, mesenchymal, and stem cell markers in patients with progressive metastases has important implications for the application and interpretation of approved methods to detect CTCs. Mol Cancer Res; 9(8); 997–1007. ©2011 AACR.

Clinical activity of abiraterone acetate in patients with metastatic castration-resistant prostate cancer progressing after enzalutamide

BACKGROUND Abiraterone acetate and enzalutamide both improve outcomes in patients with metastatic castration-resistant prostate cancer (mCRPC). Optimal sequencing for these agents and whether cross-resistance occurs is unknown. METHODS Multicentre review of patients with mCRPC treated with abiraterone acetate and prednisone after progressing on enzalutamide. Primary objective was to determine abiraterone acetate response. RESULTS Thirty patients identified from four North American centres. At abiraterone initiation, median age was 70 years (56-84 years); 70% had ECOG performance status of 0-1; all had prior docetaxel. Median prior enzalutamide treatment duration was 41 weeks (6-95 weeks), with 70% (21 of 30) having a ≥30% prostate-specific antigen (PSA) decline. Median abiraterone acetate treatment duration was 13 weeks (1-52). No objective radiographic responses were observed. Median abiraterone time to progression (PSA, objective or symptomatic) was 15.4 weeks [95% confidence interval (CI) 10.7-20.2]. Median overall survival was 50.1 weeks (95% CI 28.3-72.0). Three patients had a ≥30% PSA decline with abiraterone. Two of these patients had PSA progression as best response with prior enzalutamide. CONCLUSIONS In this study of patients progressing after enzalutamide, treatment with abiraterone was associated with a modest response rate and brief duration of effect. Primary progression on enzalutamide may not preclude a response to abiraterone.BACKGROUND Abiraterone acetate and enzalutamide both improve outcomes in patients with metastatic castration-resistant prostate cancer (mCRPC). Optimal sequencing for these agents and whether cross-resistance occurs is unknown. METHODS Multicentre review of patients with mCRPC treated with abiraterone acetate and prednisone after progressing on enzalutamide. Primary objective was to determine abiraterone acetate response. RESULTS Thirty patients identified from four North American centres. At abiraterone initiation, median age was 70 years (56-84 years); 70% had ECOG performance status of 0-1; all had prior docetaxel. Median prior enzalutamide treatment duration was 41 weeks (6-95 weeks), with 70% (21 of 30) having a ≥30% prostate-specific antigen (PSA) decline. Median abiraterone acetate treatment duration was 13 weeks (1-52). No objective radiographic responses were observed. Median abiraterone time to progression (PSA, objective or symptomatic) was 15.4 weeks [95% confidence interval (CI) 10.7-20.2]. Median overall survival was 50.1 weeks (95% CI 28.3-72.0). Three patients had a ≥30% PSA decline with abiraterone. Two of these patients had PSA progression as best response with prior enzalutamide. CONCLUSIONS In this study of patients progressing after enzalutamide, treatment with abiraterone was associated with a modest response rate and brief duration of effect. Primary progression on enzalutamide may not preclude a response to abiraterone.

Targeting the PI3K/Akt/mTOR pathway in castration-resistant prostate cancer

The phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway is a key signaling pathway that has been linked to both tumorigenesis and resistance to therapy in prostate cancer and other solid tumors. Given the significance of the PI3K/Akt/mTOR pathway in integrating cell survival signals and the high prevalence of activating PI3K/Akt/mTOR pathway alterations in prostate cancer, inhibitors of this pathway have great potential for clinical benefit. Here, we review the role of the PI3K/Akt/mTOR pathway in prostate cancer and discuss the potential use of pathway inhibitors as single agents or in combination in the evolving treatment landscape of castration-resistant prostate cancer.

The role of epithelial plasticity in prostate cancer dissemination and treatment resistance

Nearly 30,000 men die annually in the USA of prostate cancer, nearly uniformly from metastatic dissemination. Despite recent advances in hormonal, immunologic, bone-targeted, and cytotoxic chemotherapies, treatment resistance and further dissemination are inevitable in men with metastatic disease. Emerging data suggests that the phenomenon of epithelial plasticity, encompassing both reversible mesenchymal transitions and acquisition of stemness traits, may underlie this lethal biology of dissemination and treatment resistance. Understanding the molecular underpinnings of this cellular plasticity from preclinical models of prostate cancer and from biomarker studies of human metastatic prostate cancer has provided clues to novel therapeutic approaches that may delay or prevent metastatic disease and lethality over time. This review will discuss the preclinical and clinical evidence for epithelial plasticity in this rapidly changing field and relate this to clinical phenotype and resistance in prostate cancer while suggesting novel therapeutic approaches.

Development of a method to isolate circulating tumor cells using mesenchymal-based capture

Epithelial tumor cells can become mesenchymal cells and vice versa via phenotypic transitions, a process known as epithelial plasticity. We postulate that during the process of metastasis, circulating tumor cells (CTCs) lose their epithelial phenotype and acquire a mesenchymal phenotype that may not be sufficiently captured by existing epithelial-based CTC technologies. We report here on the development of a novel CTC capture method, based on the biology of epithelial plasticity, which isolates cells based on OB-cadherin cell surface expression. Using this mesenchymal-based assay, OB-cadherin cellular events are detectable in men with metastatic prostate cancer and are less common in healthy volunteers. This method may complement existing epithelial-based methods and may be particularly useful in patients with bone metastases.

A Phase II Trial of Temsirolimus in Men With Castration-Resistant Metastatic Prostate Cancer

BACKGROUND Phosphatase and tensin homologue (PTEN) loss is common in advanced prostate cancer, leading to constitutive activation of the PI3 kinase pathway. Temsirolimus blocks mammalian target of rapamycin (mTOR)/target of rapamycin complex 1 (TORC1), a key signaling node in this pathway; its activity in men with advanced castration-resistant metastatic prostate cancer (mCRPC) is unknown. METHODS We conducted a single-arm trial of weekly intravenous temsirolimus administration in men with chemorefractory mCRPC who had ≥ 5 circulating tumor cells (CTCs) at baseline. The primary end point was the change in CTCs at 8 weeks; secondary end points were composite progression-free survival (PFS) (excluding prostate-specific antigen [PSA]), PSA and radiographic response rates, safety, and survival. At PSA/CTC progression, an anti-androgen could be added while continuing temsirolimus. RESULTS Eleven patients were accrued out of a planned 20; the trial was stopped prematurely because of lack of efficacy/feasibility. Median age was 61 years, with 55% African-Americans and 36% Caucasian patients. Median baseline PSA level was 390 ng/dL, median baseline number of CTCs was 14 cells; 50% of patients had pain, and 63% had undergone ≥ 2 previous chemotherapy regimens. Median CTC decline was 48% and 3 patients experienced decline in CTCs to < 5. However, 73% of men had a persistently unfavorable number of CTCs (≥ 5) and only 1 patient had a ≥ 30% PSA decline. Median PFS was 1.9 months (95% confidence interval [CI], 0.9-3.1) and median overall survival (OS) was 8.8 months (95% CI, 3.1-15.6). Toxicities included grade 4 hypophosphatemia and central nervous system (CNS) hemorrhage, and frequent grade 3 fatigue, anemia, stomatitis, hypokalemia, weakness, and hyperglycemia. CONCLUSION Temsirolimus lacked sufficient clinical activity in men with mCRPC, despite transient CTC improvements in some men. Future studies should focus on combination approaches or novel PI3K pathway inhibitors.

A phase Ib study of combined VEGFR and mTOR inhibition with vatalanib and everolimus in patients with advanced renal cell carcinoma.

BACKGROUND Vatalanib is an oral vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitor (TKI), whereas everolimus inhibits mammalian target of rapamycin (mTOR). Combination therapy with VEGFR and mTOR inhibitors has not been well tolerated to date but may have efficacy in renal cell carcinoma (RCC). PATIENTS AND METHODS A phase Ib study of vatalanib and everolimus was performed in patients with advanced solid tumors to determine the maximum tolerated dose (MTD), safety, and tolerability of the combination. A dose-expansion cohort of 20 patients with metastatic RCC was studied to further define toxicity and preliminary efficacy in patients with RCC. RESULTS We evaluated 32 patients over 3 dose levels and a dose-expansion cohort. The most common toxicities of any grade were proteinuria, fatigue, hypertriglyceridemia, nausea, and vomiting. Dose-limiting toxicities (DLTs) included severe hypertension, diarrhea, neutropenia, mucositis, and fatigue. The MTD for the combination was vatalanib 1000 mg daily and everolimus 5 mg daily. In all patients, median overall survival (OS) was 16.3 months. In patients with RCC, median progression-free survival (PFS) was 5.8 months, and OS was 16.5 months. OS was significantly better in treatment-naive patients (25.1 months) compared with patients who had received previous vascular endothelial growth factor (VEGF)-targeted therapy (6.3 months). Seven of 24 (29.2%) evaluable patients demonstrated a partial response, and an additional 15 patients exhibited stable disease. Long-term tolerability (> 1 year) was demonstrated in 19% of patients. CONCLUSION Relevant doses of vatalanib and everolimus were achieved in combination, with expected toxicities. A substantial number of patients with RCC achieved an objective response in the treatment-naive setting, with prolonged tolerability and survival. Further comparative phase II/III studies of specifically targeted VEGF and mTOR inhibitor combinations may be warranted in patients with RCC.

Clinical phenotypes associated with circulating tumor cell enumeration in metastatic castration–resistant prostate cancer

BACKGROUND The presence of ≥5 circulating tumor cells (CTCs) is prognostic for shorter survival in men with metastatic castration-resistant prostate cancer (mCRPC). However, some men have low CTCs despite widespread disease, suggesting heterogeneity in CTC phenotype or detection. The aim of this study was to evaluate the association of CTC enumeration with clinical disease characteristics and overall survival in men with mCRPC at our institution. DESIGN CTCs were enumerated using the CellSearch method in a prospective correlative study in men with mCRPC starting a new systemic therapy. The primary objective was to determine the clinical phenotype of the subset of men with mCRPC who have a poor prognosis and low CTCs. Secondary end points included associations of CTCs with survival and known prognostic biomarkers, before therapy and at progression. RESULTS At baseline, median CTC count was 16 cells and prostate-specific antigen (PSA) level was 178 ng/ml. At progression, median CTC count was 42, PSA level was 245 ng/ml, levels of lactate dehydrogenase and alkaline phosphatase rose, and level of hemoglobin dropped. The median overall survival for this heavily pretreated population was 11.2 months, and the multivariable hazard ratio for death of men with CTCs<5 vs.≥5 was 0.43 (95% CI: 0.24-0.77). Median progression-free survival was 4.4 months. CTC enumeration modestly correlated with lactate dehydrogenase and alkaline phosphatase levels but only weakly correlated with PSA and hemoglobin levels. We were unable to identify a consistent subgroup of poor prognosis men with a low number of CTCs. CONCLUSION CTC enumeration appears to be prognostic in men with mCRPC and describes a phenotype of hematogenous dissemination that cannot be predicted based on standard clinical and laboratory assessments.

Whole Genomic Copy Number Alterations in Circulating Tumor Cells from Men with Abiraterone or Enzalutamide-Resistant Metastatic Castration-Resistant Prostate Cancer

Purpose: Beyond enumeration, circulating tumor cells (CTCs) can provide genetic information from metastatic cancer that may facilitate a greater understanding of tumor biology and enable a precision medicine approach. Experimental Design: CTCs and paired leukocytes from men with metastatic castration-resistant prostate cancer (mCRPC) were isolated from blood through red cell lysis, CD45 depletion, and flow sorting based on EpCAM/CD45 expression. We next performed whole genomic copy number analysis of CTCs and matched patient leukocytes (germline) using array-based comparative genomic hybridization (aCGH) from 16 men with mCRPC, including longitudinal and sequential aCGH analyses of CTCs in the context of enzalutamide therapy. Results: All patients had mCRPC and primary or acquired resistance to abiraterone acetate or enzalutamide. We compiled copy gains and losses, with a particular focus on those genes highly implicated in mCRPC progression and previously validated as being aberrant in metastatic tissue samples and genomic studies of reference mCRPC datasets. Genomic gains in >25% of CTCs were observed in AR, FOXA1, ABL1, MET, ERG, CDK12, BRD4, and ZFHX3, while common genomic losses involved PTEN, ZFHX3, PDE4DIP, RAF1, and GATA2. Analysis of aCGH in a sample with sequential enzalutamide-resistant visceral progression showed acquired loss of AR amplification concurrent with gain of MYCN, consistent with evolution toward a neuroendocrine-like, AR-independent clone. Conclusions: Genomic analysis of pooled CTCs in men with mCRPC suggests a reproducible, but highly complex molecular profile that includes common aberrations in AR, ERG, c-MET, and PI3K signaling during mCRPC progression, which may be useful for predictive biomarker development. Clin Cancer Res; 23(5); 1346–57. ©2016 AACR.

Potential predictive biomarkers for individualizing treatment for men with castration-resistant prostate cancer.

AbstractWith the surge in therapeutic options for men with castration-resistant prostate cancer (CRPC) comes increasingly complicated treatment decision making, highlighting the need for biomarkers that can identify appropriate patients for specific treatments and accurately assess disease response. Predictive biomarkers are factors related to the disease or the host that are associated with improvements in outcomes, such as survival, due to specific therapies. Such biomarkers have become of paramount importance in oncology to maximize the benefits of novel systemic agents while minimizing harm to individual patients and the costs to society. Given the number of newly approved and expensive systemic therapies, including novel hormonal therapies, chemotherapies, immunotherapies, and bone microenvironment-targeting therapies, predictive biomarkers are needed to give physicians a more rational sense of matching the right patient to the right therapy sequence at a given time. There are currently no validated predictive biomarkers in CRPC. We discuss potential predictive biomarkers in men with CRPC and how these may be developed in the context of therapeutic clinical trials.