Current and emerging treatment modalities for metastatic castration-resistant prostate cancer

Dianhydrogalactitol synergizes with topoisomerase poisons to overcome DNA repair activity in tumor cells

1,2:5,6-Dianhydrogalactitol (DAG) is a bi-functional DNA-targeting agent currently in phase II clinical trial for treatment of temozolomide-resistant glioblastoma (GBM). In the present study, we investigated the cytotoxic activity of DAG alone or in combination with common chemotherapy agents in GBM and prostate cancer (PCa) cells, and determined the impact of DNA repair pathways on DAG-induced cytotoxicity. We found that DAG produced replication-dependent DNA lesions decorated with RPA32, RAD51, and γH2AX foci. DAG-induced cytotoxicity was unaffected by MLH1, MSH2, and DNA-PK expression, but was enhanced by knockdown of BRCA1. Acting in S phase, DAG displayed selective synergy with topoisomerase I (camptothecin and irinotecan) and topoisomerase II (etoposide) poisons in GBM, PCa, and lung cancer cells with no synergy observed for docetaxel. Importantly, DAG combined with irinotecan treatment enhanced tumor responses and prolonged survival of tumor-bearing mice. This work provides mechanistic insight into DAG cytotoxicity in GBM and PCa cells and offers a rational for exploring combination regimens with topoisomerase I/II poisons in future clinical trials.

Prostate-specific antigen response patterns during cabazitaxel therapy in patients with metastatic castration-resistant prostate cancer

Background

The objective of this study was to categorize prostate-specific antigen (PSA) response during cabazitaxel therapy in patients with metastatic castration-resistant prostate cancer (mCRPC) into different patterns and to investigate the prognostic impact of the PSA response patterns.

Methods

We reviewed data from patients with mCRPC who had been treated with cabazitaxel therapy at four institutions belonging to Tokai Urologic Oncology Research Seminar. Patients eligible for this study had received at least three cycles of cabazitaxel treatment at three- or four-week intervals. The PSA response patterns were categorized as primary resistance (PR), response (RE), stabilization (ST), and fluctuating (FL). The overall survival (OS) was compared among the patterns.

Results

Data from a total of 50 patients were analyzed in this study. The number of patients exhibiting PR, RE, ST and FL patterns were 18 (36%), 14 (28%), 12 (24%) and 6 (12%), respectively. The median (95% CI) OS of patients with PR and RE patterns was 10.7 (5.6–15.9) and 14.9 (6.8–23.0) months, respectively, and was not reached for patients with ST and FL patterns. The OS of patients with the FL pattern was significantly better than that of patients with PR (P = 0.012) and RE (P = 0.010) patterns.

Conclusion

There were some patients whose PSA were fluctuating during cabazitaxel therapy in patients with mCRPC. Because the prognosis of such patients was relatively good, the judgment to discontinue the cabazitaxel therapy after PSA rise followed by decrease should be made prudently.

Obesity-Linked Cancers: Current Knowledge, Challenges and Limitations in Mechanistic Studies and Rodent Models

The worldwide prevalence of obesity has doubled during the last 50 years, and according to the World Obesity Federation, one third of the people on Earth will be obese by the year 2025. Obesity is described as a chronic, relapsing and multifactorial disease that causes metabolic, biomechanical, and psychosocial health consequences. Growing evidence suggests that obesity is a risk factor for multiple cancer types and rivals smoking as the leading preventable cause for cancer incidence and mortality. The epidemic of obesity will likely generate a new wave of obesity-related cancers with high aggressiveness and shortened latency. Observational studies have shown that from cancer risk to disease prognosis, an individual with obesity is consistently ranked worse compared to their lean counterpart. Mechanistic studies identified similar sets of abnormalities under obesity that may lead to cancer development, including ectopic fat storage, altered adipokine profiles, hormone fluctuations and meta-inflammation, but could not explain how these common mechanisms produce over 13 different cancer types. A major hurdle in the mechanistic underpinning of obesity-related cancer is the lack of suitable pre-clinical models that spontaneously develop obesity-linked cancers like humans. Current approaches and animal models fall short when discerning the confounders that often coexist in obesity. In this mini-review, we will briefly survey advances in the different obesity-linked cancers and discuss the challenges and limitations in the rodent models employed to study their relationship. We will also provide our perspectives on the future of obesity-linked cancer research.

Epithelial cell adhesion molecule (EpCAM) is involved in prostate cancer chemotherapy/radiotherapy response in vivo

Background

Development of chemo−/radioresistance is a major challenge for the current prostate cancer (CaP) therapy. We have previously demonstrated that epithelial cell adhesion molecule (EpCAM) is associated with CaP growth and therapeutic resistance in vitro, however, the role of EpCAM in CaP in vivo is not fully elucidated. Here, we aimed to investigate how expression of EpCAM is involved in CaP growth and chemo−/radiotherapy response in NOD/SCID mouse models in vivo and to validate its role as a therapeutic target for CaP therapy.

Methods

EpCAM was knocked down in PC-3 CaP cell line using short hairpin RNA (shRNA). The effect of EpCAM-knockdown (KD) on tumour growth, chemo−/radiotherapy response and animal survival was evaluated on subcutaneous (s.c) and orthotopic mouse models.

Results

We found that KD of EpCAM significantly inhibited tumour growth, increased xenograft sensitivity to chemotherapy/radiotherapy, and prolonged the survival of tumour-bearing mice. In addition, we demonstrated that KD of EpCAM is associated with downregulation of the PI3K/Akt/mTOR pathway.

Conclusions

In conclusion, our data confirms that CaP growth and chemo−/radioresistance in vivo is associated with over-expression of EpCAM, which serves both a functional biomarker and promising therapeutic target.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-5010-5) contains supplementary material, which is available to authorized users.

Morin promotes prostate cancer cells chemosensitivity to paclitaxel through miR-155/GATA3 axis

Paclitaxel is a first-line microtubule-stabilizing drug in treating prostate cancer. However, most patients develop resistance and experience relapse. Morin (3,5,7,20,40-pentahydroxyflavone) is an anti-tumor flavonoid in a numerous types of cancer cells including breast, ovarian and lung cancers. We therefore researched the effects of morin as an adjuvant to paclitaxel in in treating DU145 and PC-3 cells in vitro and DU145 derived prostate cancers in nude mice models. The chemosensitivities of these cells to the treatments of morin and paclitaxel were tested through viability assays utilizing cell counting kit 8 (CCK-8) and apoptosis assays through flow cytometry analyses. MicroRNA (miRNA) microarray was employed to determine the changes in miRNA profile of morin treated DU145 cells. The results from microarrays were further certified by quantitative real-time reverse transcription-PCR (qRT-PCR). The underlying targets of miR-155 were verified using luciferase assays followed by Western blot assays. In the results, morin was capable of repressing the cell viabilities in the paclitaxel-treated cells. MiR-155might be an effective target that can be down-regulated in morin-treated cells. We also discovered that GATA binding protein 3 (GATA3) was directly repressed by miR-155, and the treatment of morin reversed the expression of GATA3. In conclusion, morin might be a potential adjuvant of paclitaxel in treating prostate cancer through regulating miR-155/GATA3 axis.

Stem cells and the role of ETS transcription factors in the differentiation hierarchy of normal and malignant prostate epithelium

Prostate cancer is the most common cancer of men in the UK and accounts for a quarter of all new cases. Although treatment of localised cancer can be successful, there is no cure for patients presenting with invasive prostate cancer and there are less treatment options. They are generally treated with androgen-ablation therapies but eventually the tumours become hormone resistant and patients develop castration-resistant prostate cancer (CRPC) for which there are no further successful or curative treatments. This highlights the need for new treatment strategies. In order to prevent prostate cancer recurrence and treatment resistance, all the cell populations in a heterogeneous prostate tumour must be targeted, including the rare cancer stem cell (CSC) population. The ETS transcription factor family members are now recognised as a common feature in multiple cancers including prostate cancer; with aberrant expression, loss of tumour suppressor function, inactivating mutations and the formation of fusion genes observed. Most notably, the TMPRSS2-ERG gene fusion is present in approximately 50% of prostate cancers and in prostate CSCs. However, the role of other ETS transcription factors in prostate cancer is less well understood. This review will describe the prostate epithelial cell hierarchy and discuss the evidence behind prostate CSCs and their inherent resistance to conventional cancer therapies. The known and proposed roles of the ETS family of transcription factors in prostate epithelial cell differentiation and regulation of the CSC phenotype will be discussed, as well as how they might be targeted for therapy.

Dehydroandrographolide inhibits oral cancer cell migration and invasion through NF-κB-, AP-1-, and SP-1-modulated matrix metalloproteinase-2 inhibition

BACKGROUND AND PURPOSE

Oral cancer is a type of head and neck cancer that is characterized by cancerous tissue growth in the oral cavity. Andrographolide and dehydroandrographolide (DA) are the two principal components of Andrographis paniculata (Burm.f.) Nees and are the main contributors to its therapeutic properties. However, the pharmacological activities of DA remain unclear.

EXPERIMENTAL APPROACH

In this study, we used wound closure assay and Boyden chamber assay to determine the effects of DA on oral cancer cell migration and invasion.

KEY RESULTS

DA treatment significantly inhibited the migration and invasion abilities of SCC9 cells in vitro. Gelatin zymography and Western blotting results revealed that DA inhibited MMP-2 activity and reduced its protein levels. DA inhibited the phosphorylation of ERK1/2, p38, and JNK 1/2 in SCC9 cells. According to the mRNA levels detected using real-time PCR, DA inhibited MMP-2 expression in SCC9 cells. This inhibitory effect was associated with the upregulation of the TIMP-2 and downregulation of NF-κB, AP-1, and SP-1 expression. In addition, DA suppressed carcinoma-associated epithelial-mesenchymal transition in SCC9 cells. Finally, DA administration effectively suppressed MMP-2 expression and tumor metastases in the oral carcinoma xenograft mouse model in vivo.

CONCLUSIONS & IMPLICATIONS

DA inhibits the invasion of human oral cancer cells and is a potential chemopreventive agent against oral cancer metastasis.

A novel spontaneous model of epithelial-mesenchymal transition (EMT) using a primary prostate cancer derived cell line demonstrating distinct stem-like characteristics

Cells acquire the invasive and migratory properties necessary for the invasion-metastasis cascade and the establishment of aggressive, metastatic disease by reactivating a latent embryonic programme: epithelial-to-mesenchymal transition (EMT). Herein, we report the development of a new, spontaneous model of EMT which involves four phenotypically distinct clones derived from a primary tumour-derived human prostate cancer cell line (OPCT-1), and its use to explore relationships between EMT and the generation of cancer stem cells (CSCs) in prostate cancer. Expression of epithelial (E-cadherin) and mesenchymal markers (vimentin, fibronectin) revealed that two of the four clones were incapable of spontaneously activating EMT, whereas the others contained large populations of EMT-derived, vimentin-positive cells having spindle-like morphology. One of the two EMT-positive clones exhibited aggressive and stem cell-like characteristics, whereas the other was non-aggressive and showed no stem cell phenotype. One of the two EMT-negative clones exhibited aggressive stem cell-like properties, whereas the other was the least aggressive of all clones. These findings demonstrate the existence of distinct, aggressive CSC-like populations in prostate cancer, but, importantly, that not all cells having a potential for EMT exhibit stem cell-like properties. This unique model can be used to further interrogate the biology of EMT in prostate cancer.

Biodistribution and Efficacy of Low Temperature-Sensitive Liposome Encapsulated Docetaxel Combined with Mild Hyperthermia in a Mouse Model of Prostate Cancer

PURPOSE

Low temperature sensitive liposome (LTSL) encapsulated docetaxel were combined with mild hyperthermia (40-42°C) to investigate in vivo biodistribution and efficacy against a castrate resistant prostate cancer.

METHOD

Female athymic nude mice with human prostate PC-3 M-luciferase cells grown subcutaneously into the right hind leg were randomized into six groups: saline (+/- heat), free docetaxel (+/- heat), and LTSL docetaxel (+/- heat). Treatment (15 mg docetaxel/kg) was administered via tail vein once tumors reached a size of 200-300 mm(3). Mice tumor volumes and body weights were recorded for up to 60 days. Docetaxel concentrations of harvested tumor and organ/tissue homogenates were determined by LC-MS. Histological evaluation (Mean vessel density, Ki67 proliferation, Caspase-3 apoptosis) of saline, free Docetaxel and LTSL docetaxel (+/- heat n = 3-5) was performed to determine molecular mechanism responsible for tumor cell killing.

RESULT

LTSL/heat resulted in significantly higher tumor docetaxel concentrations (4.7-fold greater compared to free docetaxel). Adding heat to LTSL Docetaxel or free docetaxel treatment resulted in significantly greater survival and growth delay compared to other treatments (p < 0.05). Differences in body weight between all Docetaxel treatments were not reduced by >10% and were not statistically different from each other. Molecular markers such as caspase-3 were upregulated, and Ki67 expression was significantly decreased in the chemo-hyperthermia group. Vessel density was similar post treatment, but the heated group had reduced vessel area, suggesting thermal enhancement in efficacy by reduction in functional perfusion.

CONCLUSION

This technique of hyperthermia sensitization and enhanced docetaxel delivery has potential for clinical translation for prostate cancer treatment.

Neuronal Trans-Differentiation in Prostate Cancer Cells

BACKGROUND

Neuroendocrine (NE) differentiation in prostate cancer (PCa) is an aggressive phenotype associated with therapy resistance. The complete phenotype of these cells is poorly understood. Clinical classification is based predominantly on the expression of standard NE markers.

METHODS

We analyzed the phenotype of NE carcinoma of the prostate utilizing in vitro methods, in silico, and immunohistochemical analyses of human disease.

RESULTS

LNCaP cells, subjected to a variety of stressors (0.1% [v/v] fetal bovine serum, cyclic AMP) induced a reproducible phenotype consistent with neuronal trans-differentiation. Cells developed long cytoplasmic processes resembling neurons. As expected, serum deprived cells had decreased expression in androgen receptor and prostate specific antigen. A significant increase in neuronal markers also was observed. Gene array analysis demonstrated that LNCaP cells subjected to low serum or cAMP showed statistically significant manifestation of a human brain gene expression signature. In an in silico experiment using human data, we identified that only hormone resistant metastatic prostate cancer showed enrichment of the "brain profile." Gene ontology analysis demonstrated categories involved in neuronal differentiation. Three neuronal markers were validated in a large human tissue cohort.

CONCLUSION

This study proposes that the later stages of PCa evolution involves neuronal trans-differentiation, which would enable PCa cells to acquire independence from the neural axis, critical in primary tumors. Prostate 76:1312-1325, 2016. © 2016 Wiley Periodicals, Inc.

Bortezomib and etoposide combinations exert synergistic effects on the human prostate cancer cell line PC-3

Novel treatment modalities are urgently required for androgen-independent prostate cancer. In order to develop an alternative treatment for prostate cancer, the cytotoxic effects of the 26S proteasome inhibitor bortezomib, either alone or in combination with the two commonly used chemotherapeutic agents irinotecan and etoposide, on the human prostate cancer cell line PC-3 were evaluated in the present study. The PC-3 cell line was maintained in Dulbecco's modified Eagle's medium with 10% fetal bovine serum and treated with various doses of bortezomib, irinotecan, etoposide or their combinations. The growth inhibitory and cytotoxic effects were determined by water-soluble tetrazolium (WST)-1 assay, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay or iCELLigence system. The combination index values were determined by the Chou-Talalay method. The half maximal inhibitory concentration (IC50) value of bortezomib on the PC-3 cell line was determined to be 53.4 nM by WST-1 assay, whereas the IC50 values of irinotecan and etoposide were determined to be 2.1 and 26.5 µM, respectively. These results suggest that the 26S proteasome inhibitor bortezomib is more potent, compared with irinotecan and etoposide, in the androgen-insensitive and tumor protein p53-null cell line PC-3. The combined effects of bortezomib+irinotecan and bortezomib+etoposide were also tested on PC-3 cells. The effect of bortezomib+irinotecan combination was not significantly different than that produced by either monotherapy, according to the results of iCELLigence system and MTT assay. However, 40 nM bortezomib+5 µM etoposide or 40 nM bortezomib+20 µM etoposide combinations were observed to be more effective than each drug tested alone. The results of the current study suggest that bortezomib and etoposide combination may be additionally evaluated in clinical trials for the treatment of hormone-refractory prostate cancer.

Docetaxel rechallenge in metastatic castration-resistant prostate cancer: any place in the modern treatment scenario? An intention to treat evaluation

BACKGROUND

We evaluated the possible advantages of a docetaxel (DCT) rechallenge strategy in metastatic castration-resistant prostate cancer (mCRPC) patients, also given the possible earlier positioning of this treatment option in the modern scenario.

PATIENTS & METHODS

All mCRPC patients planned for DCT chemotherapy rechallenge in our institutions were evaluated.

RESULTS

Of 128 patients, 98 achieved disease control on the initial DCT round. After a treatment holiday of 8.3 months, the 98 responsive patients underwent a second DCT round, with 56 cases achieving again disease control. After a 5.7-month off-treatment period, 32 of these cases underwent a third DCT round, and 16 responded. Lastly, after a further 4.2-month treatment holiday, eight patients underwent a fourth DCT round and two responded. Median time to definitive disease progression for the whole population was 16.4 months.

CONCLUSIONS

Rechallenge with DCT may be considered a suitable treatment option for mCRPC patients recurring after a successful DCT chemotherapy. The interest in this strategy may be increased because of the showed efficacy of early DCT chemotherapy in patients with bulky disease (CHAARTED study) and the potential lower efficacy of the new hormonal agents abiraterone acetate and enzalutamide when used in a immediate sequencing.

Differential Utilization of Dietary Fatty Acids in Benign and Malignant Cells of the Prostate

Tumor cells adapt via metabolic reprogramming to meet elevated energy demands due to continuous proliferation, for example by switching to alternative energy sources. Nutrients such as glucose, fatty acids, ketone bodies and amino acids may be utilized as preferred substrates to fulfill increased energy requirements. In this study we investigated the metabolic characteristics of benign and cancer cells of the prostate with respect to their utilization of medium chain (MCTs) and long chain triglycerides (LCTs) under standard and glucose-starved culture conditions by assessing cell viability, glycolytic activity, mitochondrial respiration, the expression of genes encoding key metabolic enzymes as well as mitochondrial mass and mtDNA content. We report that BE prostate cells (RWPE-1) have a higher competence to utilize fatty acids as energy source than PCa cells (LNCaP, ABL, PC3) as shown not only by increased cell viability upon fatty acid supplementation but also by an increased ß-oxidation of fatty acids, although the base-line respiration was 2-fold higher in prostate cancer cells. Moreover, BE RWPE-1 cells were found to compensate for glucose starvation in the presence of fatty acids. Of notice, these findings were confirmed in vivo by showing that PCa tissue has a lower capacity in oxidizing fatty acids than benign prostate. Collectively, these metabolic differences between benign and prostate cancer cells and especially their differential utilization of fatty acids could be exploited to establish novel diagnostic and therapeutic strategies.

Tumor Necrosis Factor-related Apoptosis-inducing Ligand (TRAIL)-Troglitazone-induced Apoptosis in Prostate Cancer Cells Involve AMP-activated Protein Kinase

Prostate cancer (PCa) is one of the most frequently diagnosed cancers in men with limited treatment options for the hormone-resistant forms. Development of novel therapeutic options is critically needed to target advanced forms. Here we demonstrate that combinatorial treatment with the thiazolidinedione troglitazone (TZD) and TNF-related apoptosis-inducing ligand (TRAIL) can induce significant apoptosis in various PCa cells independent of androgen receptor status. Because TZD is known to activate AMP-activated protein kinase (AMPK), we determined whether AMPK is a molecular target mediating this apoptotic cascade by utilizing PCa cell lines stably overexpressing AMPKα1 dominant negative (C4-2-DN) or empty vector (C4-2-EV). Our results indicated a significantly higher degree of apoptosis with TRAIL-TZD combination in C4-2-EV cells compared with C4-2-DN cells. Similarly, results from a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed a larger reduction of viability of C4-2-EV cells compared with C4-2-DN cells when treated with TRAIL-TZD, thus suggesting that C4-2-DN cells were more apoptosis-resistant. Additionally, siRNA-mediated knockdown of endogenous AMPKα1 expression showed a reduction of TRAIL-TZD-induced apoptosis, further confirming the participation of AMPK in mediating this apoptosis. Apoptosis induction by this combinatorial treatment was also associated with a cleavage of β-catenin that was inhibited in both C4-2-DN cells and those cells in which AMPKα1 was knocked down. In addition, time course studies showed an increase in pACC(S79) (AMPK target) levels coinciding with the time of apoptosis. These studies indicate the involvement of AMPK in TRAIL-TZD-mediated apoptosis and β-catenin cleavage and suggest the possibility of utilizing AMPK as a therapeutic target in apoptosis-resistant prostate cancer.

Phase 1/2 study of orteronel (TAK-700), an investigational 17,20-lyase inhibitor, with docetaxel-prednisone in metastatic castration-resistant prostate cancer

BACKGROUND

Docetaxel-prednisone (DP) is an approved therapy for metastatic castration-resistant prostate cancer (mCRPC). Orteronel (TAK-700) is an investigational, selective, non-steroidal inhibitor of 17,20-lyase, a key enzyme in androgenic hormone production. This phase 1/2 study evaluated orteronel plus DP in mCRPC patients.

METHODS

Adult men with chemotherapy-naïve mCRPC, serum prostate-specific antigen (PSA) ≥5 ng/mL, and serum testosterone <50 ng/dL received oral orteronel 200 or 400 mg twice-daily (BID) in phase 1 to determine the recommended dose for phase 2, plus intravenous docetaxel 75 mg/m(2) every 3 weeks, and oral prednisone 5 mg BID. Phase 2 objectives included safety, pharmacokinetics, and efficacy.

RESULTS

In phase 1 (n = 6, orteronel 200 mg; n = 8, orteronel 400 mg), there was one dose-limiting toxicity of grade 3 febrile neutropenia at 400 mg BID. This dose was evaluated further in phase 2 (n = 23). After 4 cycles, 68, 59, and 23% of patients achieved ≥30, ≥50, and ≥90% PSA reductions, respectively; median best PSA response was -77%. Seven of 10 (70%) RECIST-evaluable patients achieved objective partial responses. Median time to PSA progression and radiographic disease progression was 6.7 and 12.9 months, respectively. Dehydroepiandrosterone-sulfate (DHEA-S) and testosterone levels were rapidly and durably reduced. Common adverse events were fatigue (78%), alopecia (61%), diarrhea (48%), nausea (43%), dysgeusia (39%), and neutropenia (39%). Orteronel and docetaxel pharmacokinetics were similar alone and in combination.

CONCLUSIONS

Orteronel plus DP was tolerable, with substantial reductions in PSA, DHEA-S, and testosterone levels, and evidence for measurable disease responses.

Acquisition of paclitaxel resistance is associated with a more aggressive and invasive phenotype in prostate cancer

Drug resistance is a major limitation to the successful treatment of advanced prostate cancer (PCa). Patients who have metastatic, castration-resistant PCa (mCRPC) are treated with chemotherapeutics. However, these standard therapy modalities culminate in the development of resistance. We established paclitaxel resistance in a classic, androgen-insensitive mCRPC cell line (DU145) and, using a suite of molecular and biophysical methods, characterized the structural and functional changes in vitro and in vivo that are associated with the development of drug resistance. After acquiring paclitaxel-resistance, cells exhibited an abnormal nuclear morphology with extensive chromosomal content, an increase in stiffness, and faster cytoskeletal remodeling dynamics. Compared with the parental DU145, paclitaxel-resistant (DU145-TxR) cells became highly invasive and motile in vitro, exercised greater cell traction forces, and formed larger and rapidly growing tumors in mouse xenografts. Furthermore, DU145-TxR cells showed a discrete loss of keratins but a distinct gain of ZEB1, Vimentin and Snail, suggesting an epithelial-to-mesenchymal transition. These findings demonstrate, for the first time, that paclitaxel resistance in PCa is associated with a trans-differentiation of epithelial cell machinery that enables more aggressive and invasive phenotype and portend new strategies for developing novel biomarkers and effective treatment modalities for PCa patients.

The fat side of prostate cancer

Prostate cancer (PCa) metabolism appears to be unique in comparison with other types of solid cancers. Normal prostate cells mainly rely on glucose oxidation to provide precursors for the synthesis and secretion of citrate, resulting in an incomplete Krebs cycle and minimal oxidative phosphorylation for energy production. In contrast, during transformation, PCa cells no longer secrete citrate and they reactivate the Krebs cycle as energy source. Moreover, primary PCas do not show increased aerobic glycolysis and therefore they are not efficiently detectable with (18)F-FDG-PET. However, increased de novo lipid synthesis, strictly intertwined with deregulation in classical oncogenes and oncosuppressors, is an early event of the disease. Up-regulation and increased activity of lipogenic enzymes (including fatty acid synthase and choline kinase) occurs throughout PCa carcinogenesis and correlates with worse prognosis and poor survival. Thus, lipid precursors such as acetate and choline have been successfully used as alternative tracers for PET imaging. Lipid synthesis intermediates and FA catabolism also emerged as important players in PCa maintenance. Finally, epidemiologic studies suggested that systemic metabolic disorders including obesity, metabolic syndrome, and diabetes as well as hypercaloric and fat-rich diets might increase the risk of PCa. However, how metabolic disorders contribute to PCa development and whether dietary lipids and de novo lipids synthesized intra-tumor are differentially metabolized still remains unclear. In this review, we examine the switch in lipid metabolism supporting the development and progression of PCa and we discuss how we can exploit its lipogenic nature for therapeutic and diagnostic purposes. This article is part of a Special Issue entitled Lipid Metabolism in Cancer.

Apigenin sensitizes prostate cancer cells to Apo2L/TRAIL by targeting adenine nucleotide translocase-2

Apo2 ligand (Apo2L)/tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising cancer therapeutic agent. Recombinant human Apo2L/TRAIL has been under clinical trials, whereas various kinds of malignant tumors have resistance to Apo2L/TRAIL. We and others have shown that several anticancer agents and flavonoids overcome resistance to Apo2L/TRAIL by upregulating death receptor 5 (DR5) in malignant tumor cells. However, the mechanisms by which these compounds induce DR5 expression remain unknown. Here we show that the dietary flavonoid apigenin binds and inhibits adenine nucleotide translocase-2 (ANT2), resulting in enhancement of Apo2L/TRAIL-induced apoptosis by upregulation of DR5. Apigenin and genistein, which are major flavonoids, enhanced Apo2L/TRAIL-induced apoptosis in cancer cells. Apigenin induced DR5 expression, but genistein did not. Using our method identifying the direct targets of flavonoids, we compared the binding proteins of apigenin with those of genistein. We discovered that ANT2 was a target of apigenin, but not genistein. Similarly to apigenin, knockdown of ANT2 enhanced Apo2L/TRAIL-induced apoptosis by upregulating DR5 expression at the post-transcriptional level. Moreover, silencing of ANT2 attenuated the enhancement of Apo2L/TRAIL-induced apoptosis by apigenin. These results suggest that apigenin upregulates DR5 and enhances Apo2L/TRAIL-induced apoptosis by binding and inhibiting ANT2. We propose that ANT2 inhibitors may contribute to Apo2L/TRAIL therapy.

The role of treatment modality on the utility of predictive tissue biomarkers in clinical prostate cancer: a systematic review

BACKGROUND

Tissue biomarkers could pivotally improve clinical outcome prediction following prostate cancer therapy. Clinically, prostate cancer is managed by diverse treatment modalities whose individual influence on a biomarker's predictive ability is not well understood and poorly investigated in the literature.

OBJECTIVE

We conducted a systematic review to assess the predictive value of biomarkers in different treatment contexts in prostate cancer.

STUDY METHODOLOGY

A literature search was performed using the MeSH headings "prostate neoplasms" and "biological markers". Rigorous selection criteria identified studies correlating expression with clinical outcomes from primary androgen deprivation therapy (ADT), radical prostatectomy and radiotherapy (± neoadjuvant ADT).

STUDY RESULTS

Of 10,668 studies identified, 481 papers matched initial inclusion criteria. Following rescreening, 384 studies identified 236 individual tissue biomarkers, of which 29 were predictive on multivariate analysis in at least 2 independent cohorts. The majority were only tested in surgical cohorts. Only 8 predictive biomarkers were tested across all 3 treatments with Ki67 identified as universal predictive marker. p16 showed potential for treatment stratification between surgery and radiotherapy but needs further validation in independent studies.

CONCLUSIONS

Despite years of research, very few tissue biomarkers retain predictive value in independent validation across therapy context. Currently, none have conclusive ability to help treatment selection. Future biomarker research should consider the therapy context and use uniform methodology and evaluation criteria.

Prospective evaluation of 18F-NaF and 18F-FDG PET/CT in detection of occult metastatic disease in biochemical recurrence of prostate cancer

PURPOSE

This study aimed to perform a prospective evaluation of 18F-NaF and 18F-FDG PET/CT in the detection of occult metastatic disease in men with prostate cancer and biochemical relapse.

METHODS

Thirty-seven men with prostate-specific antigen (PSA) relapse (median, 3.2 ng/mL; range, 0.5-40.2 ng/mL) after definitive therapy for localized prostate cancer [26 radical prostatectomy (RP), 11 external beam radiation therapy] and negative conventional imaging underwent 18F-FDG and 18F-NaF PET/CT on 2 separate days within the same week. Studies were interpreted by 2 experienced radiologists in consensus for abnormal uptake suspicious for metastatic disease. The reference standard was a combination of imaging and clinical follow-up. Rank of PSA values for positive and negative PET/CT was compared using analysis of variance adjusting for primary therapy. Association between PSA and scan positivity in patients with RP was evaluated using Wilcoxon rank sum test.

RESULTS

Result of the 18F-FDG PET/CT scan was positive for nodal disease in 2 patients. True-positive detection rate for occult osseous metastases by 18F-NaF PET/CT was 16.2%. Median PSA levels for positive versus negative PET/CT scans were 4.4 and 2.9 ng/mL, respectively, with the difference marginally significant in prostatectomized men (P=0.072). Percentages of patients with either 18F-NaF- or 18F-FDG-positive PET/CT in RP and external beam radiation therapy were 10% (n=10) and undefined (n=0) for a PSA of 2 ng/mL or less, 29% (n=7) and 50% (n=2) for PSA greater than 2 ng/mL but 4 ng/mL or less, 60% (n=5) and 40% (n=5) for PSA greater than 4 ng/mL but 10 ng/mL or less, and 25% (n=4) and 25% (n=4) for PSA greater than 10 ng/mL, respectively.

CONCLUSIONS

In biochemical relapse of prostate cancer, 18 F-NaF PET/CT is useful in the detection of occult osseous metastases, whereas the yield of 18F-FDG PET/CT is relatively limited. 18F-NaF PET/CT positivity tends to associate with increasing PSA level in prostatectomized men and may occur in lower PSA ranges than conventionally recognized.

The changing therapeutic landscape of castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) has a poor prognosis and remains a significant therapeutic challenge. Before 2010, only docetaxel-based chemotherapy improved survival in patients with CRPC compared with mitoxantrone. Our improved understanding of the underlying biology of CRPC has heralded a new era in molecular anticancer drug development, with a myriad of novel anticancer drugs for CRPC entering the clinic. These include the novel taxane cabazitaxel, the vaccine sipuleucel-T, the CYP17 inhibitor abiraterone, the novel androgen-receptor antagonist MDV-3100 and the radioisotope alpharadin. With these developments, the management of patients with CRPC is changing. In this Review, we discuss these promising therapies along with other novel agents that are demonstrating early signs of activity in CRPC. We propose a treatment pathway for patients with CRPC and consider strategies to optimize the use of these agents, including the incorporation of predictive and intermediate end point biomarkers, such as circulating tumor cells.

Differences in treatment patterns among patients with castration-resistant prostate cancer treated by oncologists versus urologists in a US managed care population

Objective:

Differences in treatment patterns, health care resource utilization, and costs between patients with castration-resistant prostate cancer (CRPC) treated by oncologists and those treated by urologists were examined.

Methods:

Patients aged ≥40 with CRPC were identified using claims from a large US managed health care plan between July 2001 and December 2007. A 6-month baseline period was used to assess patient characteristics. Patients with visits to an urologist, without visits to an oncologist, were assigned to the urology cohort, and patients with visits to an oncologist, with or without visits to an urologist, were assigned to the oncology cohort. Treatment patterns, health care resource utilization, and costs during a variable follow-up period were compared between cohorts using descriptive statistics and Lin’s regression.

Results:

The urology cohort had fewer comorbid illnesses (P < 0.001) and patients were less likely to have other cancers during baseline (P < 0.001) or to die during follow-up (P = 0.004) compared with the oncology cohort. The oncology cohort patients were significantly more likely to have a claim for hormones (74.5% vs 61.1%; P < 0.001), chemotherapy (46.9% vs 10.2%, P < 0.001), and radiation (22.3% vs 3.7%, P < 0.0001) over follow-up. Mean unadjusted health care costs were higher in the oncology vs the urology cohort (US$31,896 vs US$15,318, respectively; P < 0.001). At 6 years follow-up, cumulative adjusted CRPC-specific costs were significantly higher among patients treated by oncologists with chemotherapy than among patients treated by urologists.

Conclusion:

CRPC patients treated by oncologists had greater use of hormones, chemotherapy, and radiation; higher percentages of patients with inpatient stays, emergency room, and ambulatory visits; and higher health care costs, than patients treated by urologists.