Targeting CD46 for both adenocarcinoma and neuroendocrine prostate cancer.

Although initially responsive to androgen signaling inhibitors (ASIs), metastatic castration-resistant prostate cancer (mCRPC) inevitably develops and is incurable. In addition to adenocarcinoma (adeno), neuroendocrine prostate cancer (NEPC) emerges to confer ASI resistance. We have previously combined laser capture microdissection and phage antibody display library selection on human cancer specimens and identified novel internalizing antibodies binding to tumor cells residing in their tissue microenvironment. We identified the target antigen for one of these antibodies as CD46, a multifunctional protein that is best known for negatively regulating the innate immune system. CD46 is overexpressed in primary tumor tissue and CRPC (localized and metastatic; adeno and NEPC), but expressed at low levels on normal tissues except for placental trophoblasts and prostate epithelium. Abiraterone- and enzalutamide-treated mCRPC cells upregulate cell surface CD46 expression. Genomic analysis showed that the CD46 gene is gained in 45% abiraterone-resistant mCRPC patients. We conjugated a tubulin inhibitor to our macropinocytosing anti-CD46 antibody and showed that the resulting antibody-drug conjugate (ADC) potently and selectively kills both adeno and NEPC cell lines in vitro (sub-nM EC50) but not normal cells. CD46 ADC regressed and eliminated an mCRPC cell line xenograft in vivo in both subcutaneous and intrafemoral models. Exploratory toxicology studies of the CD46 ADC in non-human primates demonstrated an acceptable safety profile. Thus, CD46 is an excellent target for antibody-based therapy development, which has potential to be applicable to both adenocarcinoma and neuroendocrine types of mCRPC that are resistant to current treatment.

High-Dose Abiraterone Acetate in Men With Castration Resistant Prostate Cancer.

BACKGROUND: Abiraterone acetate (AA) inhibits androgen biosynthesis and prolongs survival in men with metastatic castration-resistant prostate cancer (mCRPC) when combined with prednisone (P). Resistance to therapy remains incompletely understood. In this open-label, single-arm, multicenter phase II study we investigated the clinical benefit of increasing the dose of AA at the time of resistance to standard-dose therapy. PATIENTS AND METHODS: Eligible patients had progressive mCRPC and started AA 1000 mg daily and P 5 mg twice daily. Patients who achieved any prostate-specific antigen (PSA) decline after 12 weeks of therapy continued AA with P until PSA or radiographic progression. At progression, AA was increased to 1000 mg twice daily with unchanged P dosing. Patients were monitored for response to therapy for a minimum of 12 weeks or until PSA or radiographic progression. The primary end point was PSA decline of at least 30% after 12 weeks of therapy at the increased dose of AA. RESULTS: Forty-one patients were enrolled from March 2013 through March 2014. Thirteen men experienced disease progression during standard-dose therapy and were subsequently treated with AA 1000 mg twice per day. Therapy was well tolerated. No PSA declines ≥ 30% nor radiographic responses were observed after 12 weeks of dose-escalated therapy. Higher baseline dehydroepiandrosterone levels, lower circulating tumor cell burden, and higher pharmacokinetic levels of abiraterone and abiraterone metabolites were associated with response to standard-dose therapy. CONCLUSION: Increasing the dose of abiraterone at the time of resistance has limited clinical utility and cannot be recommended. Lower baseline circulating androgen levels and interpatient pharmacokinetic variance appear to be associated with primary resistance to AA with P.

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

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

Measurement of copy number variation in single cancer cells using rapid-emulsification digital droplet MDA.

Uniform amplification of low input DNA is important for applications across biology, including single-cell genomics, forensic science, and microbial and viral sequencing. However, the requisite biochemical amplification methods are prone to bias, skewing sequence proportions and obscuring signals relating to copy number. Digital droplet multiple displacement amplification enables uniform amplification, but requires expert knowledge of microfluidics to generate monodisperse emulsions. In addition, existing microfluidic methods are tedious and labor intensive for preparing many samples. Here, we introduce rapid emulsification multiple displacement amplification, a method to generate monodisperse droplets with a hand-held syringe and hierarchical droplet splitter. While conventional microfluidic devices require >10 minutes to emulsify a sample, our system takes tens of seconds and yields data of equivalent quality. We demonstrate the approach by using it to accurately measure copy number variation in single cancer cells.

Programmed death-ligand 1 (PD-L1) characterization of circulating tumor cells (CTCs) in muscle invasive and metastatic bladder cancer patients.

BACKGROUND: While programmed death 1 (PD-1) and programmed death-ligand 1 (PD-L1) checkpoint inhibitors have activity in a proportion of patients with advanced bladder cancer, strongly predictive and prognostic biomarkers are still lacking. In this study, we evaluated PD-L1 protein expression on circulating tumor cells (CTCs) isolated from patients with muscle invasive (MIBC) and metastatic (mBCa) bladder cancer and explore the prognostic value of CTC PD-L1 expression on clinical outcomes. METHODS: Blood samples from 25 patients with MIBC or mBCa were collected at UCSF and shipped to Epic Sciences. All nucleated cells were subjected to immunofluorescent (IF) staining and CTC identification by fluorescent scanners using algorithmic analysis. Cytokeratin expressing (CK)+ and (CK)-CTCs (CD45-, intact nuclei, morphologically distinct from WBCs) were enumerated. A subset of patient samples underwent genetic characterization by fluorescence in situ hybridization (FISH) and copy number variation (CNV) analysis. RESULTS: CTCs were detected in 20/25 (80 %) patients, inclusive of CK+ CTCs (13/25, 52 %), CK-CTCs (14/25, 56 %), CK+ CTC Clusters (6/25, 24 %), and apoptotic CTCs (13/25, 52 %). Seven of 25 (28 %) patients had PD-L1+ CTCs; 4 of these patients had exclusively CK-/CD45-/PD-L1+ CTCs. A subset of CTCs were secondarily confirmed as bladder cancer via FISH and CNV analysis, which revealed marked genomic instability. Although this study was not powered to evaluate survival, exploratory analyses demonstrated that patients with high PD-L1+/CD45-CTC burden and low burden of apoptotic CTCs had worse overall survival. CONCLUSIONS: CTCs are detectable in both MIBC and mBCa patients. PD-L1 expression is demonstrated in both CK+ and CK-CTCs in patients with mBCa, and genomic analysis of these cells supports their tumor origin. Here we demonstrate the ability to identify CTCs in patients with advanced bladder cancer through a minimally invasive process. This may have the potential to guide checkpoint inhibitor immune therapies that have been established to have activity, often with durable responses, in a proportion of these patients.

An improved CTC isolation scheme for pairing with downstream genomics: Demonstrating clinical utility in metastatic prostate, lung and pancreatic cancer.

Improvements in technologies to yield purer circulating tumor cells (CTCs) will enable a broader range of clinical applications. We have previously demonstrated the use of a commercially available cell-adhesion matrix (CAM) assay to capture invasive CTCs (iCTCs). To improve the purity of the isolated iCTCs, here we used fluorescence-activated cell sorting (FACS) in combination with the CAM assay (CAM + FACS). Our results showed an increase of median purity from the CAM assay to CAM + FACS for the spiked-in cell lines and patient samples analyzed from three different metastatic cancer types: castration resistant prostate cancer (mCRPC), non-small cell lung cancer (mNSCLC) and pancreatic ductal adenocarcinoma cancer (mPDAC). Copy number profiles for spiked-in mCRPC cell line and mCRPC patient iCTCs were similar to expected mCRPC profiles and a matched biopsy. A somatic epidermal growth factor receptor (EGFR) mutation specific to mNSCLC was observed in the iCTCs recovered from EGFR(+) mNSCLC cell lines and patient samples. Next-generation sequencing (NGS) of spiked-in pancreatic cancer cell line and mPDAC patient iCTCs showed mPDAC common mutations. CAM + FACS iCTC enrichment enables multiple downstream genomic characterizations across different tumor types.

Circulating Tumor Cells as Potential Biomarkers in Bladder Cancer.

PURPOSE: We explored the diagnostic use of circulating tumor cells in patients with neoadjuvant bladder cancer using enumeration and next generation sequencing. MATERIALS AND METHODS: A total of 20 patients with bladder cancer who were eligible for cisplatin based neoadjuvant chemotherapy were enrolled in an institutional review board approved study. Subjects underwent blood draws at baseline and after 1 cycle of chemotherapy. A total of 11 patients with metastatic bladder cancer and 13 healthy donors were analyzed for comparison. Samples were enriched for circulating tumor cells using the novel IsoFlux™ System microfluidic collection device. Circulating tumor cell counts were analyzed for repeatability and compared with Food and Drug Administration cleared circulating tumor cells. Circulating tumor cells were also analyzed for mutational status using next generation sequencing. RESULTS: Median circulating tumor cell counts were 13 at baseline and 5 at followup in the neoadjuvant group, 29 in the metastatic group and 2 in the healthy group. The concordance of circulating tumor cell levels, defined as low-fewer than 10, medium-11 to 30 and high-greater than 30, across replicate tubes was 100% in 15 preparations. In matched samples the IsoFlux test showed 10 or more circulating tumor cells in 4 of 9 samples (44%) while CellSearch® showed 0 of 9 (0%). At cystectomy 4 months after baseline all 3 patients (100%) with medium/high circulating tumor cell levels at baseline and followup had unfavorable pathological stage disease (T1-T4 or N+). Next generation sequencing analysis showed somatic variant detection in 4 of 8 patients using a targeted cancer panel. All 8 cases (100%) had a medium/high circulating tumor cell level with a circulating tumor cell fraction of greater than 5% purity. CONCLUSIONS: This study demonstrates a potential role for circulating tumor cell assays in the management of bladder cancer. The IsoFlux method of circulating tumor cell detection shows increased sensitivity compared with CellSearch. A next generation sequencing assay is presented with sufficient sensitivity to detect genomic alterations in circulating tumor cells.

Detection and characterization of invasive circulating tumor cells derived from men with metastatic castration-resistant prostate cancer.

The Vitatex cell-adhesion matrix (CAM) platform allows for isolation of invasive circulating tumor cells (iCTCs). Here we sought to determine the utility of prostate-specific membrane antigen (PSMA) as a metastatic castration-resistant prostate cancer (mCRPC) iCTC biomarker, to identify solitary cells and clusters of iCTCs expressing either epithelial, mesenchymal, or stem cell markers, and to explore the feasibility of iCTC epigenomic analysis. CTCs were isolated and enumerated simultaneously using the Vitatex and CellSearch platforms in 23 men with mCRPC. CAM-avid iCTCs were identified as nucleated cells capable of CAM uptake, but without detectable expression of hematopoietic lineage (HL) markers including CD45. iCTCs were enumerated immunocytochemically (ICC) and by flow cytometry. Whole-genome methylation status was determined for iCTCs using the Illumina HumanMethylation27 BeadChip. Thirty-four samples were collected for iCTC analysis. A median of 27 (range 0-800) and 23 (range 2-390) iCTCs/mL were detected by ICC and flow, respectively. In a subset of 20 samples, a median of seven CTCs/mL (range 0-85) were detected by the CellSearch platform compared to 26 by the CAM platform. iCTC clusters were observed in 17% of samples. iCTCs expressing PSMA as well as markers of EMT and stemness were detectable. The iCTC methylation profile highly resembled mCRPC. More CTCs were recovered using the CAM platform than the CellSearch platform, and the CAM platform allowed for the detection of iCTC clusters, iCTCs expressing EMT and stem-cell markers, and characterization of the iCTC methylome. Correlation with clinical data in future studies may yield further insight into the functional significance of these findings.

Looking back, to the future of circulating tumor cells.

Detection and analysis of circulating tumor cells (CTCs) from patients with metastatic malignancies have become active areas of research in recent years. CTC enumeration has already proven useful in establishing prognosis for patients with metastatic breast, colon, and prostate cancer. More recently, studies are going beyond enumeration, exploring the CTCs as a means to better understand the mechanisms of tumorigenesis, invasion, and metastasis and the value of CTC characterization for prognosis and tailoring of treatment. Analysis of CTC subpopulations, for example, is highlighting the importance of the epithelial to mesenchymal transition (EMT), a process which may be crucial for allowing tumors to invade into and grow at sites distant from the original tumor site. Similarly, the detection of CTCs expressing markers of stemness may also have important implications for treatment resistance. Genomic analysis of CTC and CTC subpopulations may allow for selection of novel therapeutic targets to combat treatment resistance. CTCs become a particularly valuable biospecimen resource when tissue biopsies are unavailable or not feasible and liquid biopsies allow for serial monitoring. Lastly, cultures of patient-derived CTCs may allow for an evaluation of therapeutic strategies performed ex vivo and in real time. This review article will focus on these developments, starting with the CTC pathogenesis, going on to discuss the different platforms available for CTC isolation and their use to date in these arenas, then will explore multiple topics including the existing data concerning CTC subpopulations and their clinical relevance, genomic characterization, and lastly, avenues for future research.

Iron-mediated lipid peroxidation and lipid raft disruption in low-dose silica-induced macrophage cytokine production.

Silica inhalation can induce respiratory disease. Iron is suspected of playing an important role in silica-mediated respiratory toxicity, but unambiguously determining its role has been hampered by incomplete characterization, use of high particle doses, and lack of understanding of proinflammatory mechanisms. In this study, we investigated a novel hypothesis for the mechanism of silica particle-induced increase in cytokine production. We studied the role of iron in lipid peroxidation-dependent transcription of cytokines in macrophages by ground natural silica particles at low sublethal doses. Particle size, size distribution, surface area, and structure were determined using electron microscopy, nitrogen adsorption, and X-ray diffraction. Iron impurity concentrations before and after acid treatment were determined by energy-dispersive X-ray and inductively coupled plasma mass spectroscopy. At a low noncytotoxic dose (1 µg/ml) of 2-µm silica, the presence of iron significantly increased superoxide (O(2)(•-)), lipid peroxidation, lipid raft disruption, and cytokine production in macrophages. The iron chelators deferoxamine mesylate and diethylenetriaminepentaacetic acid were found to abrogate O(2)(•-) production and inhibit lipid peroxidation, raft disruption, and cytokine induction. Tricyclodecan-9-yl xanthate, a competitive inhibitor of phosphatidylcholine-specific phospholipase C (PC-PLC), which is an upstream participant in NF-κB activation, and manganese(III) tetrakis(N-ethylpyridinium-2-yl) porphyrin, a superoxide dismutase and catalase mimic, blocked silica-stimulated cytokine production. We propose a pathway of iron-induced lipid peroxidation disrupting lipid rafts and signaling for the production of cytokines through PC-PLC in silica-exposed macrophages.