Sequencing of agents in castration-resistant prostate cancer

A Dual Targeting Dendrimer-Mediated siRNA Delivery System for Effective Gene Silencing in Cancer Therapy

Small interfering RNA (siRNA) is emerging as a novel therapeutic for treating various diseases, provided a safe and efficient delivery is available. In particular, specific delivery to target cells is critical for achieving high therapeutic efficacy while reducing toxicity. Amphiphilic dendrimers are emerging as novel promising carriers for siRNA delivery by virtue of the combined multivalent cooperativity of dendrimers with the self-assembling property of lipid vectors. Here, we report a ballistic approach for targeted siRNA delivery to cancer cells using an amphiphilic dendrimer equipped with a dual targeting peptide bearing an RGDK warhead. According to the molecular design, the amphiphilic dendrimer was expected to deliver siRNA effectively, while the aim of the targeting peptide was to home in on tumors via interaction of its warhead with integrin and the neuropilin-1 receptor on cancer cells. Coating the positively charged siRNA/dendrimer delivery complex with the negatively charged segment of the targeting peptide via electrostatic interactions led to small and stable nanoparticles which were able to protect siRNA from degradation while maintaining the accessibility of RGDK for targeting cancer cells and preserving the ability of the siRNA to escape from endosomes. The targeted system had enhanced siRNA delivery, stronger gene silencing, and more potent anticancer activity compared to nontargeted or covalent dendrimer-based systems. In addition, neither acute toxicity nor induced inflammation was observed. Consequently, this delivery system constitutes a promising nonviral vector for targeted delivery and can be further developed to provide RNAi-based personalized medicine against cancer. Our study also gives new perspectives on the use of nanotechnology based on self-assembling dendrimers in various biomedical applications.

DNA repair defects in prostate cancer: impact for screening, prognostication and treatment

Failure of effective DNA damage repair is a hallmark of cancer, but was previously underappreciated as a driver of aggressive prostate cancer. However, recent international sequencing efforts have revealed that both germline and somatic alterations within the homologous recombination and mismatch repair pathways are relatively common in lethal metastatic disease. BRCA2 gene alterations are particularly prevalent and are linked to poor prognosis as well as poor responses to systemic therapy for castration-resistant prostate cancer, although there is conflicting support for the latter. Defective DNA repair contributes to tumour heterogeneity, evolution and progression, but there are high hopes that management of this aggressive subset will be transformed by biomarker-driven use of poly-ADP ribose polymerase (PARP) inhibitors and platinum-based chemotherapy. In this review, we detail the relationship between DNA repair defects and prostate cancer, highlighting the prevalence of mutations in key genes and their controversial association with clinical outcomes.

Collateral resistance to taxanes in enzalutamide-resistant prostate cancer through aberrant androgen receptor and its variants

Currently, the optimal sequential use of androgen receptor (AR) axis-targeted agents and taxane chemotherapies remains undetermined. We aimed to elucidate the resistance status between taxanes and enzalutamide, and the functional role of the AR axis. Enzalutamide-resistant 22Rv1 cells showed collateral resistance to taxanes, including docetaxel and cabazitaxel. However, taxane-resistant cells showed no collateral resistance to enzalutamide; taxane-resistant cells expressed comparable protein levels of full-length AR and AR variants. Knockdown of both full-length AR and AR variants rendered cells sensitive to taxanes, whereas knockdown of AR variants sensitized cells to enzalutamide, but not to taxanes. In contrast, overexpression of full-length AR rendered cells resistant to taxanes. Consistently, the prostate-specific antigen response and progression-free survival in docetaxel chemotherapy were worse in cases with prior use of ARAT agents compared with cases without. Collateral resistance to taxanes was evident after obtaining enzalutamide resistance, and aberrant AR signaling might be involved in taxane resistance.

Enzalutamide after chemotherapy in advanced castration-resistant prostate cancer: the Italian Named Patient Program

AIM

To collect efficacy and safety data of enzalutamide after docetaxel, we retrospectively evaluated the Italian Named Patient Program results.

PATIENTS & METHODS

Two hundred and nine metastatic castration-resistant prostate cancer patients were enrolled. Median age was 73 years. Total 42.1% patients had pain, 14.4% had a performance status of two and 59.8% had a Gleason score ≥8. Total 31.1% had previously received ≥2 chemotherapies, 15.3 and 12% had been previously treated with abiraterone and cabazitaxel, respectively and 14.8% had received both.

RESULTS

 Median progression-free survival and overall survival were 4.8 and 13.1 months, respectively. A prostate-specific antigen reduction ≥50% was observed in 49.1%. Total 32.7% abiraterone-pretreated patients achieved a biochemical response compared with 56% of abiraterone-naive patients.

CONCLUSION

 Enzalutamide was safe and well tolerated. Its antitumor activity in abiraterone-pretreated patients was limited.

Plasma Cell-free DNA Concentration and Outcomes from Taxane Therapy in Metastatic Castration-resistant Prostate Cancer from Two Phase III Trials (FIRSTANA and PROSELICA)

BACKGROUND

Noninvasive biomarkers are needed to guide metastatic castration-resistant prostate cancer (mCRPC) treatment.

OBJECTIVE

To clinically qualify baseline and on-treatment cell-free DNA (cfDNA) concentrations as biomarkers of patient outcome following taxane chemotherapy.

DESIGN, SETTING, AND PARTICIPANTS

Blood for cfDNA analyses was prospectively collected from 571 mCRPC patients participating in two phase III clinical trials, FIRSTANA (NCT01308567) and PROSELICA (NCT01308580). Patients received docetaxel (75mg/m2) or cabazitaxel (20 or 25mg/m2) as first-line chemotherapy (FIRSTANA), and cabazitaxel (20 or 25mg/m2) as second-line chemotherapy (PROSELICA).

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Associations between cfDNA concentration and prostate-specific antigen (PSA) response were tested using logistic regression models. Survival was estimated using Kaplan-Meier methods for cfDNA concentration grouped by quartile. Cox proportional hazard models, within each study, tested for associations with radiological progression-free survival (rPFS) and overall survival (OS), with multivariable analyses adjusting for baseline prognostic variables. Two-stage individual patient meta-analysis combined results for cfDNA concentrations for both studies.

RESULTS AND LIMITATIONS

In 2502 samples, baseline log10 cfDNA concentration correlated with known prognostic factors, shorter rPFS (hazard ratio [HR]=1.54; 95% confidence interval [CI]: 1.15-2.08; p=0.004), and shorter OS on taxane therapy (HR=1.53; 95% CI: 1.18-1.97; p=0.001). In multivariable analyses, baseline cfDNA concentration was an independent prognostic variable for rPFS and OS in both first- and second-line chemotherapy settings. Patients with a PSA response experienced a decline in log10 cfDNA concentrations during the first four cycles of treatment (per cycle -0.03; 95% CI: -0.044 to -0.009; p=0.003). Study limitations included the fact that blood sample collection was not mandated for all patients and the inability to specifically quantitate tumour-derived cfDNA fraction in cfDNA.

CONCLUSIONS

We report that changes in cfDNA concentrations correlate with both rPFS and OS in patients receiving first- and second-line taxane therapy, and may serve as independent prognostic biomarkers of response to taxanes.

PATIENT SUMMARY

In the past decade, several new therapies have been introduced for men diagnosed with metastatic prostate cancer. Although metastatic prostate cancer remains incurable, these novel agents have extended patient survival and improved their quality of life in comparison with the last decade. To further optimise treatment allocation and individualise patient care, better tests (biomarkers) are needed to guide the delivery of improved and more precise care. In this report, we assessed cfDNA in over 2500 blood samples from men with prostate cancer who were recruited to two separate international studies and received taxane chemotherapy. We quantified the concentration of cfDNA fragments in blood plasma, which partly originates from tumour. We identified that higher concentrations of circulating cfDNA fragments, prior to starting taxane chemotherapy, can be used to identify patients with aggressive prostate cancer. A decline in cfDNA concentration during the first 3-9 wk after initiation of taxane therapy was seen in patients deriving benefit from taxane chemotherapy. These results identified circulating cfDNA as a new biomarker of aggressive disease in metastatic prostate cancer and imply that the study of cfDNA has clinical utility, supporting further efforts to develop blood-based tests on this circulating tumour-derived DNA.

Dual role of autophagy on docetaxel-sensitivity in prostate cancer cells

Prostate cancer (PC) is one of the leading causes of death in males. Available treatments often lead to the appearance of chemoresistant foci and metastases, with mechanisms still partially unknown. Within tumour mass, autophagy may promote cell survival by enhancing cancer cells tolerability to different cell stresses, like hypoxia, starvation or those triggered by chemotherapic agents. Because of its connection with the apoptotic pathways, autophagy has been differentially implicated, either as prodeath or prosurvival factor, in the appearance of more aggressive tumours. Here, in three PC cells (LNCaP, PC3, and DU145), we tested how different autophagy inducers modulate docetaxel-induced apoptosis. We selected the mTOR-independent disaccharide trehalose and the mTOR-dependent macrolide lactone rapamycin autophagy inducers. In castration-resistant PC (CRPC) PC3 cells, trehalose specifically prevented intrinsic apoptosis in docetaxel-treated cells. Trehalose reduced the release of cytochrome c triggered by docetaxel and the formation of aberrant mitochondria, possibly by enhancing the turnover of damaged mitochondria via autophagy (mitophagy). In fact, trehalose increased LC3 and p62 expression, LC3-II and p62 (p62 bodies) accumulation and the induction of LC3 puncta. In docetaxel-treated cells, trehalose, but not rapamycin, determined a perinuclear mitochondrial aggregation (mito-aggresomes), and mitochondria specifically colocalized with LC3 and p62-positive autophagosomes. In PC3 cells, rapamycin retained its ability to activate autophagy without evidences of mitophagy even in presence of docetaxel. Interestingly, these results were replicated in LNCaP cells, whereas trehalose and rapamycin did not modify the response to docetaxel in the ATG5-deficient (autophagy resistant) DU145 cells. Therefore, autophagy is involved to alter the response to chemotherapy in combination therapies and the response may be influenced by the different autophagic pathways utilized and by the type of cancer cells.

Treatment in the STAMPEDE era for castrate resistant prostate cancer in the UK: ongoing challenges and underappreciated clinical problems

BACKGROUND

This study aimed to explore the opinions of healthcare professionals regarding the management of men with advanced prostate cancer with particular emphasis on treatment timing and sequencing; treatment adverse-effects and exercise a supportive therapy.

METHODS

Semi-structured interviews with a purposively selected group of healthcare professionals involved in prostate cancer care within the NHS, conducted over the phone or face to face. A total of 37 healthcare professionals participated in the interviews including urologists, clinical oncologists, medical oncologists, clinical nurse specialists, general practitioners, physiotherapists, exercise specialists, service managers, clinical commissioners and primary care physicians.

RESULTS

The availability of newer treatments for advanced prostate cancer as well as results from the STAMPEDE and CHAARTED trials has resulted in new challenges for patients and HCPs. This includes the impact of an increased workload on oncologists, a potential lack of clinical continuity between urology and oncology and uncertainties regarding optimal selection, timing and sequencing of chemotherapy and second-line treatment. Fitness for treatment in advanced prostate cancer populations remains a significant barrier to accessing therapies for patients with a poor performance status. Among this, muscle wastage can significantly affect performance status and consequentially compromise cancer therapy. Exercise was regarded as a potential therapy to mitigate the adverse-effects of treatment including the prevention or reduction in muscle wastage.

CONCLUSIONS

There is a lack of data guiding clinicians in this post STAMPEDE and CHAARTED era, work is needed to reassess and optimize the prostate cancer care pathway as it evolves. Exercise should be explored as a therapeutic option to mitigate the effects of long term ADT. Further study from a wider cohort of both prostate cancer care specialists and patients will aid in establishing a highly functioning pathway with optimal individualised care.

TRIAL REGISTRATION

Sustained exercise TrAining for Men wIth prostate caNcer on Androgen deprivation: the STAMINA programme (RP-DG-1213-10,010). REC Reference: 15/SW/0260 IRAS Project ID: 178340 Hospital ID: STH 18391 approved on 24/08/2015.

Targeted and Nontargeted α-Particle Therapies

α-Particle irradiation of cancerous tissue is increasingly recognized as a potent therapeutic option. We briefly review the physics, radiobiology, and dosimetry of α-particle emitters, as well as the distinguishing features that make them unique for radiopharmaceutical therapy. We also review the emerging clinical role of α-particle therapy in managing cancer and recent studies on in vitro and preclinical α-particle therapy delivered by antibodies, other small molecules, and nanometer-sized particles. In addition to their unique radiopharmaceutical characteristics, the increased availability and improved radiochemistry of α-particle radionuclides have contributed to the growing recent interest in α-particle radiotherapy. Targeted therapy strategies have presented novel possibilities for the use of α-particles in the treatment of cancer. Clinical experience has already demonstrated the safe and effective use of α-particle emitters as potent tumor-selective drugs for the treatment of leukemia and metastatic disease.

Treatment of Advanced Prostate Cancer-A Review of Current Therapies and Future Promise

Despite many recent advances in the therapy for metastatic castration-resistant prostate cancer (mCRPC), the disease remains incurable, although men suffering from this disease are living considerably longer. In this review, we discuss the current treatment options available for this disease, such as taxane-based chemotherapy, the novel hormone therapies abiraterone and enzalutamide, and treatments such as radium-223 and sipuleucel-T. We also highlight the need for ongoing research in this field, because, despite numerous recent advances, the prognosis for mCRPC remains poor. Furthermore, as a growing body of evidence shows the increasing heterogeneity of the disease, and highlights the ongoing need for disease molecular stratification and validation/qualification of predictive biomarkers, we explore this burgeoning research space that is likely to transform how we treat this disease. We describe putative predictive biomarkers, including androgen receptor splice variants, phosphatase and tensin homolog (PTEN) loss, homologous recombination repair defects, including BRCA2 loss, and mismatch repair defects. The development of next-generation sequencing techniques and the routine biopsy of metastatic disease have driven significant advances in our understanding of the genomics of cancer, and are now poised to transform our treatment of this disease.

[Metronomic chemotherapy with oral cyclophosphamide : An individual option for the metastatic castration-resistant prostate cancer patient?]

BACKGROUND

Multiple experimental approaches are meanwhile available for progressive metastatic castration resistant prostate cancer (mCRPC) patients after failure of guideline recommended therapy (i. e., chemotherapy and/or hormonal treatment). We evaluated the outcome of metronomic chemotherapy with cyclophosphamide (CY) in combination with low-dose prednisolone.

MATERIALS AND METHODS

A total of 14 mCRPC-patients were treated with CY 50 mg/day (plus prednisolone 10 mg/day) between November 2012 and September 2017 after being resistant or unfit for chemotherapy and/or further hormonal treatment. Time to progression and overall survival (OS) were retrospectively determined by using Kaplan-Meier curves.

RESULTS

Eight of 14 (57.1%) patients had undergone radical prostatectomy and 2 (14.3%) external beam radiation. All patients had at least three therapy lines and 50% had ≥5 mCRPC therapies. The median time from first diagnosis to mCRPC was 88 months; the median age was 78 years with a median baseline serum prostate-specific antigen (PSA) level of 341 ng/ml. With a median follow-up of 16.4 months, progression-free survival (PFS) was 71, 64, and 43% after 2, 4, and 6 months, respectively. Median OS was 8.1 months. No relevant adverse events occurred.

CONCLUSION

Since CY is a well-tolerated medication with partially good clinical tumor control, it seems to be a convenient, individual treatment option in progressive mCRPC patients after failure of guideline recommended therapy.

Targeted alpha therapy using Radium-223: From physics to biological effects

With the advance of the use of ionizing radiation in therapy, targeted alpha therapy (TAT) has assumed an important role around the world. This kind of therapy can potentially reduce side effects caused by radiation in normal tissues and increased destructive radiobiological effects in tumor cells. However, in many countries, the use of this therapy is still in a pioneering phase. Radium-223 (²²³Ra), an alpha-emitting radionuclide, has been the first of its kind to be approved for the treatment of bone metastasis in metastatic castration-resistant prostate cancer. Nevertheless, the interaction mechanism and the direct effects of this radiopharmaceutical in tumor cells are not fully understood neither characterized at a molecular level. In fact, the ways how TAT is linked to radiobiological effects in cancer is not yet revised. Therefore, this review introduces some physical properties of TAT that leads to biological effects and links this information to the hallmarks of cancer. The authors also collected the studies developed with ²²³Ra to correlate with the three categories reviewed - properties of TAT, 5 R's of radiobiology and hallmarks of cancer- and with the promising future to this radiopharmaceutical.

Radium-223 in the therapeutic sequence of metastatic castration-resistant prostate cancer

CONTEXT

Radium-223 is an □ -particle transmitter with specific action on bone metastases. The Alpharadin in Symptomatic Prostate Cancer Patients (ALSYMPCA) study showed that radium-223 extended overall survival and delayed the onset of bone events in patients with symptomatic castration-resistant prostate cancer with bone metastases (mCRPC) and without visceral metastases, with a good safety profile.

OBJECTIVE

To review the new scientific evidence on radium-223 based on prespecified and post-hoc analyses of the ALSYMPCA study and on early-access programs after the publication of the ALSYMPCA study, thereby providing new data on the management of patients with mCRPC.

ACQUISITION OF EVIDENCE

We searched for evidence on PubMed and in the abstracts of international urology and oncology congresses, as well as ongoing clinical trials (ClinicalTrials.gov).

SYNTHESIS OF THE EVIDENCE

The results of the reviewed studies offer promising results that will broaden the therapeutic benefits of radium-223 to patients with mild symptoms and those with no symptoms. The results also provide preliminary evidence on the benefit of radium-223 treatment after the failure of docetaxel, enzalutamide or abiraterone or the combination of radium-223 with these agents or other therapeutic agents such as bone-targeted agents and immunotherapy.

CONCLUSION

Radium-223 can be a treatment option for patients with mild symptoms and can provide a therapeutic benefit after failure of currently available treatments or in combination with these treatments. This evidence should be corroborated in clinical trials before being added to clinical practice.

Interrogating Metastatic Prostate Cancer Treatment Switch Decisions: A Multi-institutional Survey

BACKGROUND

Evaluation of responses to treatment for metastatic castration-resistant prostate cancer (mCRPC) remains challenging. Consensus criteria based on prostate-specific antigen (PSA) and clinical and radiologic biomarkers are inconsistently utilized. Circulating tumor cell (CTC) counts can inform prognosis and response, but are not routinely used.

OBJECTIVE

To evaluate the use of biomarkers and trends in clinical decision-making in current mCRPC treatment.

DESIGN, SETTING, AND PARTICIPANTS

A 23-part online questionnaire was completed by physicians treating mCRPC.

OUTCOME MEASURES AND STATISTICAL ANALYSIS

Results are presented as the proportion (%) of physicians responding to each of the options. We used χ2 and Fisher's tests to compare differences.

RESULTS AND LIMITATIONS

A total of 118 physicians (22.1%) responded. Of these, 69.4% treated ≥50 mCRPC patients/year. More physicians administered four or fewer courses of cabazitaxel (27.9%) than for docetaxel (10.4%), with no significant difference in the number of courses between bone-only disease and Response Evaluation Criteria in Solid Tumours (RECIST)-evaluable disease. Some 74.5% of respondents considered current biomarkers useful for monitoring disease, but only 39.6% used the Prostate Cancer Working Group (PCWG2) criteria in clinical practice. PSA was considered an important biomarker by 55.7%, but only 41.4% discarded changes in PSA before 12 wk, and only 39.4% were able to identify bone-scan progression according to PCWG2. The vast majority of physicians (90.5%) considered clinical progression to be important for switching treatment. The proportion considering biomarkers important was 71.6% for RECIST, 47.4% for bone scans, 23.2% for CTCs, and 21.1% for PSA. Although 53.1% acknowledged that baseline CTC counts are prognostic, only 33.7% would use CTC changes alone to switch treatment in patients with bone-only disease. The main challenges in using CTC counts were access to CTC technology (84.7%), cost (74.5%), and uncertainty over utility as a response indicator (58.2%).

CONCLUSIONS

A significant proportion of physicians discontinue treatment for mCRPC before 12 wk, raising concerns about inadequate response assessment. Many physicians find current biomarkers useful, but most rely on symptoms to drive treatment switch decisions, suggesting there is a need for more precise biomarkers.

PATIENT SUMMARY

In this report we analyse the results of a questionnaire evaluating tools for clinical decision-making completed by 118 prostate cancer specialists. We found that most physicians favour clinical progression over prostate-specific antigen or imaging, and that criteria established by the Prostate Cancer Working Group are not widely used.

Treatment-induced changes in the androgen receptor axis: Liquid biopsies as diagnostic/prognostic tools for prostate cancer

Prostate cancer progression and treatment relapse is associated with changes in the androgen receptor axis, and analysis of alternations of androgen receptor signaling is valuable for prognostics and treatment optimization. The profile of androgen receptor axis is currently obtained from biopsy specimens, which are not always easy to obtain. Moreover, the information acquired only provides a snapshot of the tumor biology, with strict spatial and temporal limitations. On the other hand, circulation is easily accessible source of both circulating tumor cells and circulating tumor DNA, which can be sampled at numerous time points. This Review will explore the potential use of androgen receptor axis alternations detectable in the blood in therapeutic decision-making and precision medicine for advancing metastatic castration-resistant prostate cancer.

Subcutaneous Fat Distribution is a Prognostic Biomarker for Men with Castration Resistant Prostate Cancer

PURPOSE

The relationship between body fat distribution and survival remains unclear in patients with castration resistant prostate cancer treated with docetaxel and androgen receptor axis targeted agents. We investigated whether body composition parameters could predict radiographic progression-free and cancer specific survival in patients with castration resistant prostate cancer.

MATERIALS AND METHODS

In this multicenter retrospective study we evaluated data on 282 consecutive patients diagnosed with castration resistant prostate cancer between September 2009 and March 2017. The subcutaneous fat index, the visceral fat index and the skeletal muscle index at the diagnosis of castration resistant prostate cancer were determined by computerized tomography data. Survival analyses were performed using the subcutaneous fat, visceral fat and skeletal muscle indexes dichotomized at 39.9, 58 and 52.4 cm²/m², respectively.

RESULTS

At the diagnosis of castration resistant prostate cancer, cancer specific survival was independently predicted using prostate specific antigen levels, Gleason score 8 or greater, performance status, a shorter interval from androgen deprivation therapy to castration resistant prostate cancer and a subcutaneous fat index of less than 39.9 cm²/m². During the median followup of 16.0 months patients with a subcutaneous fat index of 39.9 cm²/m² or greater received more docetaxel cycles than patients with a subcutaneous fat index of less than 39.9 cm²/m². Compared to patients with a subcutaneous fat index of less than 39.9 cm²/m² those with an index of 39.9 cm²/m² or greater had better 1-year progression-free and 2-year cancer specific survival (p = 0.009 and 0.021, respectively).

CONCLUSIONS

Patients with a subcutaneous fat index of 39.9 cm²/m² or greater at the diagnosis of castration resistant prostate cancer showed higher progression-free and cancer specific survival rates than those with a subcutaneous fat index of less 39.9 cm²/m² at diagnosis. The subcutaneous fat index determined by computerized tomography data could serve as a useful objective prognostic factor to discuss patient therapeutic options. Further studies are needed to define the roles of each body composition parameter in relation to pharmacokinetics and oncologic outcome.

Hyper-acetylation contributes to the sensitivity of chemo-resistant prostate cancer cells to histone deacetylase inhibitor Trichostatin A

Therapeutic agents are urgently needed for treating metastatic castration‐refractory prostate cancer (mCRPC) that is unresponsive to androgen deprivation and chemotherapy. Our screening assays demonstrated that chemotherapy‐resistant prostate cancer (PCa) cells are more sensitive to HDAC inhibitors than paired sensitive PCa cells, as demonstrated by cell proliferation and apoptosis in vitro and in vivo. Kinetic study revealed that TSA‐induced apoptosis was significantly dependent on enhanced transcription and protein synthesis in an early stage, which subsequently caused ER stress and apoptosis. ChIP analysis indicated that TSA increased H4K16 acetylation, promoting ER stress gene transcription. The changes in Ac‐H4K16, ATF3 and ATF4 were also validated in TSA‐treated animals. Further study revealed the higher enzyme activity of HDACs and an increase in acetylated proteins in resistant cells. The higher nucleocytoplasmic acetyl‐CoA in resistant cells was responsible for elevated acetylation status of protein and a more vigorous growth state. These results strongly support the pre‐clinical application of HDAC inhibitors for treating chemotherapy‐resistant mCRPC.

Castration-Resistant Prostate Cancer: Mechanisms, Targets and Treatment

Prostate cancer is the most common malignancy in men, and remains the second leading cause of cancer-related death in this gender [1]. Data suggests that 10-20% of patients with prostate cancer metastasis develop castration-resistant prostate cancer (CRPC) within 5 years of follow-up, and that the median survival since development of castration resistance is approximately 14 months (range 9-30) [2]. Additionally, patients with non-metastatic CRPC are at higher risk of disease progression. Approximately 15-33% of patients develop metastasis within 2 years, increasing the mortality burden in this population [3, 4].

Effectiveness of Deferred Combined Androgen Blockade Therapy Predicts Efficacy in Abiraterone Acetate Treated Metastatic Castration-Resistant Prostate Cancer Patients after Docetaxel

Introduction: Conventional anti-androgen regimens were widely used as an initiation or combined androgen blockade (CAB) therapy in advanced prostate cancer patients. Currently, new androgen pathway inhibitors such as abiraterone acetate (AA) and enzalutamide had been proven effective in metastatic castration resistant prostate cancer. In this study, we attempt to analyze the role of conventional anti-androgen drugs as deferred CAB therapy in castration-resistant prostate cancer patients.

Materials and Methods: From 2012 to 2017, 48 metastatic castration-resistant prostate cancer (CRPC) patients who received sequential treatments with primary androgen blockade, oral anti-androgen regimens, and docetaxel followed by AA treatment were included. We defined effective deferred CAB as any decline of PSA after add-on antiandrogen after CRPC. Patients were separated into effective and ineffective deferred CAB. Comparison between two groups in the first line androgen deprivation therapy duration, CRPC PSA level, pre-AA PSA level, chemotherapy dosages, duration, and patients progression free survival and overall survival after AA treatment were analyzed.

Results: Twenty-three patients (47.9%) achieved PSA decline after deferred CAB. Among total 48 patients, 24 patients experienced PSA decline more than 50% after AA treatment. The median PSA progression-free survival and overall survival after AA treatment in the total cohort of 48 patients were 4.4 and 24.3 months, respectively. The effective deferred CAB group showed significantly lower PSA level, lower percentage of PSA progression, higher total follow-up duration, higher percentage of surviving patients, better progression free survival, and overall survival estimate after AA treatment. Of the eight variables analyzed, effectiveness in deferred CAB showed positive association to progression free survival (HR 0.29, 95% CI 0.12–0.67, p = 0.004) and overall survival (HR 0.24, 95% CI 0.07–0.81, p = 0.022). First line androgen deprivation therapy (ADT) duration also showed positive association to overall survival (HR 0.95, 95% CI 0.91–0.99, p = 0.023).

Conclusions: Effectiveness of deferred CAB therapy was positively associated with progression free survival and overall survival of AA treatment after docetaxel. It can be used as a pre-treatment predictor.

Investigation of Cytotoxic Activity of Mitoxantrone at the Individual Cell Level by Using Ionic-Liquid-Tag-Enhanced Mass Spectrometry

A novel mitoxantrone conjugate was synthesized by coupling mitoxantrone with ionic liquid tags, and cytotoxic behavior of the designed conjugate was studied in normal and cancer cell lines. The synthesized mitoxantrone conjugate was oil at physiological temperatures and demonstrated high aqueous solubility. Sensitivity of electrospray ionization mass spectrometry (ESI-MS) to the mitoxantrone conjugate was improved by an order of magnitude, in comparison with original mitoxantrone dihydrochloride. The observed ESI-MS signals were shifted to a "clearer" lower-mass region of the spectrum, which allowed investigation of the drug at the level of individual cells. The ionic liquid tags proposed in the present work consist of an easily available imidazolium salt residue and show a number of key advantages from the points of view of drug conjugate synthesis, drug delivery and analytic detection.

HOTAIR-mediated reciprocal regulation of EZH2 and DNMT1 contribute to polyphyllin I-inhibited growth of castration-resistant prostate cancer cells in vitro and in vivo

BACKGROUND

Polyphyllin I (PPI), one of the steroidal saponins in paris polyphylla, has been reported to exhibit antitumor effects. However, the detailed molecular mechanism underlying this has not been elucidated.

METHODS

Cell viability and cell cycle distribution were measured using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) and Flow cytometry assays, respectively. Cell invasion and migration were examined by Transwell invasion and wound healing assays. Western blot analysis was performed to examine the protein expressions of zeste homolog 2 (EZH2), DNA methyltransferase 1 (DNMT1). QRT-PCR was used to examine the levels of long non-coding RNA (lncRNA) HOX transcript antisense RNA (HOTAIR). Small interfering RNAs (siRNAs) method was used to knockdown HOTAIR. Exogenously expressions of HOTAIR, DNMT1 and EZH2 were carried out by Transient transfection assays. EZH2 promoter activity was measured by Secrete-Pair Dual Luminescence Assay Kit. A nude mice xenograft model was used to confirm the findings in vitro.

RESULTS

We showed that PPI significantly inhibited growth, induced cell cycle arrest of castration-resistant prostate cancer (CRPC) cells. In addition, PPI also reduced the migration and invasion in CRPC cells. In mechanism, we found that PPI decreased the protein expressions of EZH2, DNMT1 and levels of HOTAIR. Interestingly, silenced HOTAIR reduced EZH2 and DNMT1 protein expressions. On the contrary, exogenously expressed HOTAIR resisted PPI-inhibited EZH2 and DNMT1 protein expressions, EZH2 promoter activity and cell growth. Moreover, excessive EZH2 antagonized PPI-suppressed DNMT1 protein expression or vice versa. Consistent with this, PPI inhibited tumor growth, HOTAIR, the protein expressions of DNMT1 and EZH2 in vivo.

CONCLUSION

Our results show that PPI inhibits growth of CRPC cells through inhibition of HOTAIR expression, subsequently; this results in the repression of DNMT1 and EZH2 expressions. The interactions among HOTAIR, DNMT1 and EZH2, and reciprocal regulation of DNMT1 and EZH2 contribute to the overall responses of PPI. This study reveals a novel mechanism for HOTAIR-mediated regulating DNMT1 and EZH2 in response to PPI in inhibition of the growth of CRPC cells.

Selection and monitoring of patients with metastatic castration-resistant prostate cancer for treatment with radium-223

Despite the improvement provided by androgenic suppression in the treatment of prostate cancer, most of tumors develop resistance to castration. However, new therapies have demonstrated an increase in patient survival such as radium-223 (Ra-223), an alpha emitter and calcium mimetic with the capability of targeting osteoblastic metastatic lesions. According to results of the ALSYMPCA phase III trial, Ra-223 has demonstrated its activity by improving symptoms and survival of patients with metastatic castration-resistant prostate cancer (mCRPC), symptomatic bone metastases, and no known visceral metastatic disease, without interfering with subsequent treatments. This review examines the key evidence to establish the best patient selection criteria to use Ra-223, how to assess the response to treatment, treatment-related toxicity, and follow-up, but also current research regarding imaging techniques and biomarkers to assess the efficacy of Ra-223. Finally, we briefly describe the clinical trials that are currently ongoing with Ra-223.

The evolution of chemotherapy for the treatment of prostate cancer

Chemotherapy has been explored as a treatment option for metastatic prostate cancer since the early 1980s. Docetaxel, a taxane chemotherapeutic, was approved for the treatment of men with metastatic castration-resistant prostate cancer in 2004, and is now standard of care for late stage disease. Recent clinical studies demonstrated that patients with metastatic castration-sensitive disease, and possibly those with high-risk localized prostate cancer also benefit from docetaxel administration, expanding the role of chemotherapy in the prostate cancer treatment landscape. Another taxane, cabazitaxel, is approved for post-docetaxel metastatic castration-resistant prostate cancer. Taxanes and other chemotherapeutics, such as carboplatin, are now being tested in combination regimens. This review presents an outline of recent and ongoing clinical studies assessing docetaxel and its derivative cabazitaxel at different stages of the disease, and in various combinations with other agents. We summarize current knowledge on biomarkers predictive of response to chemotherapy, which may in future be used to guide individualized treatment decisions.

Second-line therapy in patients with metastatic castration-resistant prostate cancer with progression after or under docetaxel: A systematic review of nine randomized controlled trials

Treatment decisions are challenging in patients with metastatic castration-resistant prostate cancer with progression after or under docetaxel. The current review systematically searched the published literature on all treatment options, and assessed the risk of bias and quality of evidence. It found the best available evidence for effective prolongation of overall survival and progression-free survival for abiraterone acetate plus prednisone versus placebo plus prednisone and enzalutamide versus placebo. Other treatment modalities could be beneficial for individual patients by taking into consideration the: selection criteria of the randomized clinical trials, risk of bias, subgroup analyses, and quality of life and adverse events. Further research is needed to determine the sequence, timing asnd combination of different treatments.

Patient characteristics and overall survival in patients with post-docetaxel metastatic castration-resistant prostate cancer in the community setting

It is unclear how treatment sequencing for metastatic castration-resistant prostate cancer (mCRPC) affects real-world patient outcomes. We assessed treatment sequences, patient characteristics and overall survival (OS) in post-docetaxel mCRPC patients. mCRPC patients receiving second-line cabazitaxel or androgen receptor-targeted therapy (ART; abiraterone/enzalutamide) post-docetaxel were identified using electronic medical records. OS was assessed from second-line therapy initiation using Cox regressions adjusting for: metastases; prostate-specific antigen (PSA); hemoglobin; alkaline phosphatase (ALP); albumin; second-line therapy initiation year. Following docetaxel (n = 629), 123 (19.6%) and 506 (80.4%) patients received cabazitaxel and ART, respectively. One hundred and ninety-five patients received additional treatments thereafter (54 following cabazitaxel; 141 following ART). Although patients receiving second-line cabazitaxel versus ART had similar disease characteristics at first-line therapy initiation, at second-line therapy initiation they had higher mean PSA (386.6 vs. 233.9 ng/mL) and ALP (182.0 vs. 167.3 u/L), lower mean hemoglobin (10.8 vs. 11.5 g/dL), and more frequently had intermediate/high-risk Halabi scores (61.8 vs. 48.4%); all p < 0.05. Overall, crude survival was not significantly different. Among Halabi high-risk patients, adjusted median OS was significantly longer in patients receiving cabazitaxel versus ART (HR 0.48; 95% CI 0.24–0.93; p = 0.030). Low albumin and hemoglobin led to similar findings (HR 0.43; 95% CI 0.23–0.80; p = 0.0077; HR 0.60; 95% CI 0.40–0.90; p = 0.014). Most post-docetaxel patients received second-line ART. Patients receiving second-line cabazitaxel had more high-risk features; however, second-line cabazitaxel administered after docetaxel may improve OS in patients with Halabi high-risk scores or low albumin/hemoglobin.

Predicting Response and Recognizing Resistance: Improving Outcomes in Patients With Castration-resistant Prostate Cancer

Optimal sequencing strategies for approved agents in metastatic castration-resistant prostate cancer (mCRPC) are unclear. Retrospective clinical studies suggest cross-resistance between specific therapies. This review assesses treatment decisions for mCRPC. Increased use of chemohormonal therapy in castration-sensitive disease may affect subsequent treatment decisions in mCRPC. Initial abiraterone or enzalutamide treatment may result in cross-resistance for subsequent androgen receptor-targeted therapy. Clinical responses may be seen in both docetaxel- and cabazitaxel-treated patients progressing after treatment with abiraterone or enzalutamide. These observations are supported by proposed resistance mechanisms. In conclusion, small, retrospective studies suggest cross-resistance between specific therapies in mCRPC. Larger prospective studies are required.

Prognostic and predictive biomarkers in prostate cancer: latest evidence and clinical implications

Advances in our understanding of the mechanisms driving castration-resistant prostate cancer have promoted the development of several new drugs including androgen receptor-directed therapy and chemotherapy. Concomitant docetaxel treatment at the beginning of hormonal therapy for metastatic prostate cancer has resulted in longer overall survival than with hormonal therapy alone. Elucidating an appropriate treatment sequence using these therapies is important for maximizing clinical benefit in castration-sensitive and castration-resistant prostate cancer patients. The development of advanced high-throughput ‘omics’ technology has enabled the use of novel markers to guide prognosis and treatment of this disease. In this review, we outline the genomic landscape of prostate cancer and the molecular mechanisms of castration-resistant progression, and how these affect the development of new drugs, and their clinical implications for selecting treatment sequence. We also discuss many of the potential tissue-based or liquid biomarkers that may soon enter clinical use, with the hope that several of these prognostic or predictive markers will guide precision medicine for prostate cancer patients in the near future.

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

BACKGROUND

There is an urgent need to identify biomarkers to guide personalized therapy in castration-resistant prostate cancer (CRPC). We aimed to clinically qualify androgen receptor (AR) gene status measurement in plasma DNA using multiplex droplet digital PCR (ddPCR) in pre- and post-chemotherapy CRPC.

METHODS

We optimized ddPCR assays for AR copy number and mutations and retrospectively analyzed plasma DNA from patients recruited to one of the three biomarker protocols with prospectively collected clinical data. We evaluated associations between plasma AR and overall survival (OS) and progression-free survival (PFS) in 73 chemotherapy-naïve and 98 post-docetaxel CRPC patients treated with enzalutamide or abiraterone (Primary cohort) and 94 chemotherapy-naïve patients treated with enzalutamide (Secondary cohort; PREMIERE trial).

RESULTS

In the primary cohort, AR gain was observed in 10 (14%) chemotherapy-naïve and 33 (34%) post-docetaxel patients and associated with worse OS [hazard ratio (HR), 3.98; 95% CI 1.74-9.10; P < 0.001 and HR 3.81; 95% CI 2.28-6.37; P < 0.001, respectively], PFS (HR 2.18; 95% CI 1.08-4.39; P = 0.03, and HR 1.95; 95% CI 1.23-3.11; P = 0.01, respectively) and rate of PSA decline ≥50% [odds ratio (OR), 4.7; 95% CI 1.17-19.17; P = 0.035 and OR, 5.0; 95% CI 1.70-14.91; P = 0.003, respectively]. AR mutations [2105T>A (p.L702H) and 2632A>G (p.T878A)] were observed in eight (11%) post-docetaxel but no chemotherapy-naïve abiraterone-treated patients and were also associated with worse OS (HR 3.26; 95% CI 1.47-not reached; P = 0.004). There was no interaction between AR and docetaxel status (P = 0.83 for OS, P = 0.99 for PFS). In the PREMIERE trial, 11 patients (12%) with AR gain had worse PSA-PFS (sPFS) (HR 4.33; 95% CI 1.94-9.68; P < 0.001), radiographic-PFS (rPFS) (HR 8.06; 95% CI 3.26-19.93; P < 0.001) and OS (HR 11.08; 95% CI 2.16-56.95; P = 0.004). Plasma AR was an independent predictor of outcome on multivariable analyses in both cohorts.

CONCLUSION

Plasma AR status assessment using ddPCR identifies CRPC with worse outcome to enzalutamide or abiraterone. Prospective evaluation of treatment decisions based on plasma AR is now required.

CLINICAL TRIAL NUMBER

NCT02288936 (PREMIERE trial).

Real-world Characteristics and Outcomes of Patients With Metastatic Castration-resistant Prostate Cancer Receiving Chemotherapy Versus Androgen Receptor-targeted Therapy After Failure of First-line Androgen Receptor-targeted Therapy in the Community Setting

BACKGROUND

In metastatic castration-resistant prostate cancer (mCRPC), optimal treatment sequences are unknown. We assessed second-line taxane (TT) versus androgen receptor-targeted therapy (ART), after initial ART failure, in United States oncology community practices.

PATIENTS AND METHODS

Using electronic medical records, patients with mCRPC receiving first-line ART and second-line therapy (TT, ART) were identified. Response and overall survival (OS) were evaluated from second-line therapy initiation. Multivariate analyses were adjusted for year, age, metastases, opioid use, prostate-specific antigen (PSA), hemoglobin, alkaline phosphatase, and albumin levels.

RESULTS

Of 546 patients receiving first-line ART, 206 and 340 received second-line TT and ART. Compared with patients receiving second-line ART, patients receiving TT were younger (median, 74 vs. 79 years), more had intermediate-high Halabi risk scores (59% vs. 35%), had higher opioid use (42% vs. 22%), median PSA (116 vs. 48 ng/mL), alkaline phosphatase (112 vs. 87 U/L), and lactate dehydrogenase (254 vs. 201 U/L), and had lower hemoglobin (11.2 vs. 12.3 g/dL) and albumin levels (3.8 vs. 4.0 g/dL); all P < .001. Response rates were higher with second-line TT versus ART (clinical response, 44.2% vs. 24.7%; P = .006; PSA response, 44.5% vs. 28.7%; P = .004). OS did not differ between cohorts (hazard ratio [HR], 0.90; P = .511). Among patients with a poor prognosis (hemoglobin < 11 g/d; albumin < lower limit of normal), those receiving second-line TT versus ART showed improved OS (HR, 0.52; P = .004 and HR, 0.36; P = .003, respectively).

CONCLUSIONS

Despite more severe disease profiles, patients with mCRPC receiving second-line TT versus ART achieved higher response rates after initial ART. Poor prognosis patients had improved OS with second-line TT versus ART.

Treating breast cancer metastasis with cabazitaxel-loaded polymeric micelles

Cancer metastasis is the primary cause of high mortality in breast cancer patients. In this study, we loaded an anti-cancer drug, cabazitaxel (CTX), into polymeric micelles (CTX-loaded polymeric micelles, PCMs), and explored their therapeutic efficacy in breast cancer metastasis. The characteristics of PCMs were investigated, and their anti-metastatic efficacy was assessed using in vitro and in vivo evaluations. PCMs had an average diameter of 50.13±11.96 nm with a CTX encapsulation efficiency of 97.02%±0.97%. PCMs could be effectively internalized into metastatic 4T1 breast cancer cells in vitro. CTX (10 ng/mL) or an equivalent concentration in PCMs did not significantly affected the viability of 4T1 cells, but dramatically decreased the cell migration activities. In an orthotopic metastatic breast cancer model, intravenously administered PCMs could be efficiently delivered to the tumor sites, resulting in a 71.6% inhibition of tumor growth and a 93.5% reduction of lung metastases. Taken together, our results verify the anti-metastatic efficacy of PCMs, thus providing an encouraging strategy for treating breast cancer metastasis.

Association Between Early PSA Increase and Clinical Outcome in Patients Treated with Enzalutamide for Metastatic Castration Resistant Prostate Cancer

OBJECTIVE

Prostate-specific antigen (PSA) decline by 50 % from the baseline to 12 weeks (PSA50w12) is currently used to predict response to treatment and clinical outcome of patients with metastatic castration-resistant prostate cancer (mCRPC). We evaluated the association between PSA changes at 4 weeks and clinical outcome.

PATIENTS AND METHODS

Eligible patients had PSA levels assessed at baseline, and monthly during enzalutamide treatment. Early PSA increase was defined as an increased PSA level at 4 weeks ≥20 % (PSA + 20w4) from baseline. Early PSA decline was defined as a PSA response at 4 weeks ≥30 % (PSA30w4) and ≥50 % (PSA50w4) from baseline. Progression-free survival (PFS), overall survival (OS) and their 95 % confidence intervals (CI) were evaluated by the Kaplan-Meier method and compared with the log-rank test. The impact of early PSA increase and decline on PFS and OS was evaluated by Cox regression analyses.

RESULTS

We assessed 193 patients with median age of 73 years (range 43-91 years). The median follow-up was 11.7 months (range 0.5-27.4 months). PSA + 20w4 predicted both PFS and OS [HR 6.50 (95 % CI 2.63-16.07; p < 0.0001) and HR 10.54 (95 % CI 4.02-27.64; p < 0.0001), respectively], whereas PSA30w4 and PSA50w4 predicted only PFS [HR 0.37 (95 % CI 0.21-0.67; p = 0.0009) and HR 0.34 (95 % CI 0.19-0.60; p = 0.0003), respectively].

CONCLUSIONS

An early PSA increase, defined as a PSA level at 4 weeks ≥20 % (PSA + 20w4), could be useful to quickly identify patients unlikely to benefit from enzalutamide. Larger studies are needed to confirm PSA + 20W4 as an early biomarker of primary resistance to enzalutamide.

The prevention of fragility fractures in patients with non-metastatic prostate cancer: a position statement by the international osteoporosis foundation

Androgen deprivation therapy is commonly employed for the treatment of non-metastatic prostate cancer as primary or adjuvant treatment. The skeleton is greatly compromised in men with prostate cancer during androgen deprivation therapy because of the lack of androgens and estrogens, which are trophic factors for bone. Men receiving androgen deprivation therapy sustain variable degrees of bone loss with an increased risk of fragility fractures. Several bone antiresorptive agents have been tested in randomized controlled trials in these patients. Oral bisphosphonates, such as alendronate and risedronate, and intravenous bisphosphonates, such as pamidronate and zoledronic acid, have been shown to increase bone density and decrease the risk of fractures in men receiving androgen deprivation therapy. Denosumab, a fully monoclonal antibody that inhibits osteoclastic-mediated bone resorption, is also effective in increasing bone mineral density and reducing fracture rates in these patients. The assessment of fracture risk, T-score and/or the evaluation of prevalent fragility fractures are mandatory for the selection of patients who will benefit from antiresorptive therapy. In the future, new agents modulating bone turnover and skeletal muscle metabolism will be available for testing in these subjects.

Exploring the optimal sequence of abiraterone and enzalutamide in patients with chemotherapy-naïve castration-resistant prostate cancer: The Kyoto-Baltimore collaboration

OBJECTIVES

To evaluate and compare the efficacy of sequential treatment with abiraterone followed by enzalutamide or vice versa for castration-resistant prostate cancer.

METHODS

We retrospectively evaluated data on 198 consecutive chemotherapy-naïve patients who had received both abiraterone and enzalutamide for castration-resistant prostate cancer at Kyoto University Hospital (including satellite hospitals) and at Johns Hopkins Cancer Center. Prostate-specific antigen progression-free survival and overall survival in patients treated with sequential abiraterone-to-enzalutamide versus enzalutamide-to-abiraterone without intervening therapies were compared.

RESULTS

Overall, 113 patients were treated with the abiraterone-to-enzalutamide sequence and 85 with the enzalutamide-to-abiraterone sequence. Median prostate-specific antigen progression-free survival was not significantly different between abiraterone and enzalutamide in the first-line setting (hazard ratio 0.88, 95% confidence interval 0.66-1.19, P = 0.412), but there was an advantage favoring enzalutamide compared with abiraterone in the second-line setting (hazard ratio 0.67, 95% confidence interval 0.49-0.91, P = 0.009). Furthermore, the combined prostate-specific antigen progression-free survival was significantly longer in the abiraterone-to-enzalutamide sequence than in the enzalutamide-to-abiraterone sequence (hazard ratio 0.56, 95% confidence interval 0.41-0.76, P < 0.001). The difference was significant even in multivariate analyses (hazard ratio 0.65, 95% confidence interval 0.42-0.99, P = 0.044). There was no statistical difference in overall survival between the two sequences in univariate (hazard ratio 0.88, 95% confidence interval 0.53-1.43, P = 0.599) and multivariate analyses (hazard ratio 0.81, 95% confidence interval 0.49-1.35, P = 0.427).

CONCLUSIONS

The abiraterone-to-enzalutamide sequence might have more favorable efficacy in terms of combined prostate-specific antigen progression-free survival than the enzalutamide-to-abiraterone sequence, although no differences in overall survival were observed. This could possibly be attributable to longer prostate-specific antigen progression-free survival with second-line enzalutamide compared with abiraterone.

First-line management of metastatic castrate-resistant prostate cancer patients: Audit of real-life practices

BACKGROUND

No reliable guidelines are available for choosing the best option between docetaxel and new hormonal therapies (NHTs) (i.e., abiraterone and enzalutamide) in first-line therapy for metastatic castration-resistant prostate cancer (mCRPC) patients. We performed an audit of real-life practices.

METHODS

We built an online questionnaire and distributed it with the help of French oncology networks. This questionnaire was sent to 481 physicians who treat patients with mCRPC. All of the answers were declarative, individual, and anonymized. A descriptive analysis was done. A univariate logistic regression analysis was performed for the criteria of choice between docetaxel and NHTs.

RESULTS

From March to July 2015, 109/481 physicians (22.6%) completed the questionnaire. The selection criteria for initially choosing docetaxel were as follows: presence of visceral metastases (79.8%), heavy tumor burden (68.8%), aggressive tumor disease (66.1%), and short-term efficacy of castration (66.1%). The selection criteria for initially choosing NHTs were as follows: long-term efficacy of castration (66.1%), higher age (67.9%), low tumor grade (56.9%), and absence of symptoms (54.1%). With docetaxel, the first tumor assessment was typically performed after three (1-6) cycles, including prostate-specific antigen (PSA) testing (96.3%), a thoraco-abdominopelvic CT scan (68.8%), and bone scintigraphy (59.6%). With NHTs, tumor assessment was mainly performed after 3 months of treatment (1-6) and included PSA testing, a thoraco-abdominopelvic CT, and bone scintigraphy in 90.8%, 61.5%, and 63.3% of cases, respectively.

CONCLUSIONS

This is the first study assessing real-life practices among physicians who treat patients with mCRPC. These practices were found to be homogeneous.

Paired High-Content Analysis of Prostate Cancer Cells in Bone Marrow and Blood Characterizes Increased Androgen Receptor Expression in Tumor Cell Clusters

Purpose: Recent studies demonstrate that prostate cancer clones from different metastatic sites are dynamically represented in the blood of patients over time, suggesting that the paired evaluation of tumor cells in circulation and bone marrow, the primary target for prostate cancer metastasis, may provide complementary information.Experimental Design: We adapted our single-cell high-content liquid biopsy platform to bone marrow aspirates (BMA) to concurrently identify and characterize prostate cancer cells in patients' blood and bone and thus discern features associated to tumorigenicity and dynamics of metastatic progression.Results: The incidence of tumor cells in BMAs increased as the disease advanced: 0% in biochemically recurrent (n = 52), 26% in newly diagnosed metastatic hormone-naïve (n = 26), and 39% in metastatic castration-resistant prostate cancer (mCRPC; n = 63) patients, and their number was often higher than in paired blood. Tumor cell detection in metastatic patients' BMAs was concordant but 45% more sensitive than using traditional histopathologic interpretation of core bone marrow biopsies. Tumor cell clusters were more prevalent and bigger in BMAs than in blood, expressed higher levels of the androgen receptor protein per tumor cell, and were prognostic in mCRPC. Moreover, the patterns of genomic copy number variation in single tumor cells in paired blood and BMAs showed significant inter- and intrapatient heterogeneity.Conclusions: Paired analysis of single prostate cancer cells in blood and bone shows promise for clinical application and provides complementary information. The high prevalence and prognostic significance of tumor cell clusters, particularly in BMAs, suggest that these structures are key mediators of prostate cancer's metastatic progression. Clin Cancer Res; 23(7); 1722-32. ©2016 AACR.

Navigating the evolving therapeutic landscape in advanced prostate cancer

Prostate cancer is the most common cause of cancer in men, with 137.9 new cases per 100,000 men per year. The overall 5-year survival rate for prostate cancer is very high. Up to 20% of men who undergo state-of-the art treatment for prostate cancer will develop castration-resistant prostate cancer (CRPC) within 5 years, with median survival for those with metastatic CRPC ranging from approximately 15 to 36 months in recent studies. With the advent of several new drugs in the past 5 years to treat CRPC, the challenge facing clinicians is how to best sequence or combine therapies or both to optimize outcomes. A better understanding of the disease process and the role of the androgen receptor as a target for both therapy and resistance have led to the consideration of biomarkers as an approach to aid in selecting the appropriate agent for a given patient as patients respond to or tolerate different drugs differently. Research to identify new prognostic biomarkers, which are associated with outcome measures, as well as predictive biomarkers, which predict response or resistance to therapy is ongoing. The treatment of advanced prostate cancer and the research related to biomarkers are discussed.

First-line non-cytotoxic therapy in chemotherapy-naive patients with metastatic castration-resistant prostate cancer: a systematic review of 10 randomised clinical trials

The aim of this study is to systematically evaluate all available treatment options in chemotherapy-naive patients with metastatic castration-resistant prostate cancer (mCRPC). We systematically searched PubMed, EMBASE, and the Cochrane libraries up to 1 March 2016 for peer-reviewed publications on randomised clinical trials (RCTs). RCTs were included if progression-free survival (PFS), overall survival (OS), quality of life (QoL), or adverse events (AEs) were quantitatively evaluated. We assessed the risk of bias with the Cochrane Collaboration's tool and graded the evidence with the Grading of Recommendations Assessment, Development and Evaluation (GRADE) Working Group's approach. We included 25 articles, reporting on 10 unique RCTs describing seven different comparisons. In one RCT, a prolonged OS and PFS (high quality) were found with abiraterone and prednisone compared to placebo plus prednisone. In one RCT, a prolonged OS and PFS (high quality) were found with enzalutamide compared to placebo. In two RCTs, a prolonged OS (high and moderate quality) was found with ²²³ radium compared to placebo, but its effect on PFS is unknown. In three RCTs, a prolonged OS (moderate quality) was found with sipuleucel-T compared to placebo, but no prolonged PFS (low quality). In one RCT a prolonged PFS (high quality) was found with orteronel compared to placebo, but no prolonged OS (moderate quality). In one RCT, a prolonged OS (moderate quality) was found with bicalutamide compared to placebo, but its effect on PFS is unknown. In one RCT, a prolonged PFS (high quality) was found with enzalutamide compared to bicalutamide, but its effect on OS is unknown. The best evidence was found for abiraterone and enzalutamide for effective prolongation of OS and PFS to treat chemotherapy-naive patients with mCRPC. However, taking both QoL and AEs into consideration, other treatment modalities could be considered for individual patients.

Androgen receptor-dependent and -independent mechanisms driving prostate cancer progression: Opportunities for therapeutic targeting from multiple angles

Despite aggressive treatment for localized cancer, prostate cancer (PC) remains a leading cause of cancer-related death for American men due to a subset of patients progressing to lethal and incurable metastatic castrate-resistant prostate cancer (CRPC). Organ-confined PC is treated by surgery or radiation with or without androgen deprivation therapy (ADT), while options for locally advanced and disseminated PC include radiation combined with ADT, or systemic treatments including chemotherapy. Progression to CRPC results from failure of ADT, which targets the androgen receptor (AR) signaling axis and inhibits AR-driven proliferation and survival pathways. The exact mechanisms underlying the transition from androgen-dependent PC to CRPC remain incompletely understood. Reactivation of AR has been shown to occur in CRPC despite depletion of circulating androgens by ADT. At the same time, the presence of AR-negative cell populations in CRPC has also been identified. While AR signaling has been proposed as the primary driver of CRPC, AR-independent signaling pathways may represent additional mechanisms underlying CRPC progression. Identification of new therapeutic strategies to target both AR-positive and AR-negative PC cell populations and, thereby, AR-driven as well as non-AR-driven PC cell growth and survival mechanisms would provide a two-pronged approach to eliminate CRPC cells with potential for synthetic lethality. In this review, we provide an overview of AR-dependent and AR-independent molecular mechanisms which drive CRPC, with special emphasis on the role of the Jak2-Stat5a/b signaling pathway in promoting castrate-resistant growth of PC through both AR-dependent and AR-independent mechanisms.

Comparing Sequencing of Abiraterone and Enzalutamide in Men With Metastatic Castration-Resistant Prostate Cancer: A Retrospective Study

BACKGROUND

There are no validated clinical decision tools to aid optimal treatment selection in men with metastatic castration-resistant prostate cancer (mCRPC). Frequently, abiraterone and enzalutamide are used prior to chemotherapy in mCRPC, given the more favorable safety profiles. However, there is no published data on clinical outcomes regarding best sequencing of these two agents.

METHODS

A retrospective analysis of consecutive mCRPC patients treated with enzalutamide and abiraterone at Johns Hopkins was conducted. Patients were treated with sequential enzalutamide and abiraterone, in either order. The combined progression-free survival (PFS: PFS1 + PFS2) of abiraterone-to-enzalutamide was compared to the reverse sequence, where PFS1 and PFS2 represented clinical/radiographic progression-free survival on the first and second agents, respectively. Overall survival (OS) from the start of the first therapy to death and PSA response rates (defined as ≥50% PSA declines at any time) were also compared between groups. Outcomes were adjusted using propensity score-weighted multivariable Cox analyses.

RESULTS

Eighty-one patients who satisfied our entry criteria were identified: 65 in the abiraterone-to-enzalutamide group and 16 in the enzalutamide-to-abiraterone group. There were no significant baseline differences between groups. Multivariable analysis suggested a difference between groups favoring the abiraterone-to-enzalutamide sequence with respect to combined PFS (HR 0.37, 95%CI 0.22-0.64, P < 0.001). There was no statistical difference in OS between the groups after multivariable adjustment (HR 0.57, 95%CI 0.29-1.11, P = 0.098), although OS was numerically superior in the abiraterone-to-enzalutamide group.

CONCLUSIONS

We observed differences suggesting improved outcomes favoring the abiraterone-to-enzalutamide sequence in men with mCRPC, with statistical confirmation in terms of PFS but not OS. Prospective studies are required to verify these hypothesis-generating findings. Further evaluation of biomarkers to inform optimal treatment sequencing in men with mCRPC is urgently needed. Prostate 77:33-40, 2017. © 2016 Wiley Periodicals, Inc.

Relation between plasma trough concentration of abiraterone and prostate-specific antigen response in metastatic castration-resistant prostate cancer patients

BACKGROUND

Abiraterone (ABI) is a major oral agent for the treatment of metastatic castration-resistant prostate cancer (mCRPC) patients but its systemic exposure is subject to a large inter-individual variability. We aimed to explore the relationship between ABI trough plasma concentration and prostate-specific antigen (PSA) response in mCRPC patients and to identify the critical determinants for its activity.

PATIENTS AND METHODS

This is a monocentric prospective observational study in mCRPC patients treated with ABI. The plasmatic concentration of ABI at steady state was measured using liquid chromatography with fluorescence detection. The primary objective was to study the relationship between mean ABI plasma exposure (ABI C_min) and 3-month PSA response.

RESULTS

From 2012 to 2016, 61 mCRPC patients were eligible for pharmacokinetic/pharmacodynamic assessment. Thirty-eight patients experienced PSA response (62%, [confidence interval {CI} 95% 50-78]). In univariate analysis, ABI C_min was 1.5-fold higher in responders: 12.0 ng/mL (CI 95% 9.4-15.6) versus 8.0 ng/mL (CI 95% 5.8-11.6; P = 0.0015). In multivariate analysis, only ABI C_min was independently associated with PSA response (odds ratio = 1.12 [CI 95% 1.01-1.25], P = 0.004). By receiver operating characteristic analysis, the optimal threshold for ABI C_min was 8.4 ng/mL. Progression-free survival (PFS) was significantly higher in patients with ABI C_min above 8.4 ng/mL (hazard ratio 0.55, [CI 95% 0.31-0.99], 12.2 [CI 95% 9.2-19.5] versus 7.4 [CI 95% 5.5-14.7] months otherwise, P = 0.044).

CONCLUSIONS

We showed that ABI trough concentration correlates with PSA response and PFS. Moreover, we could determine a cut-off value of plasmatic concentration for PSA response. Altogether, ABI concentration monitoring appears as a new approach to improve clinical outcome in mCPRC patients.

Sipuleucel-T and Androgen Receptor-Directed Therapy for Castration-Resistant Prostate Cancer: A Meta-Analysis

New treatments, such as sipuleucel-T and androgen receptor- (AR-) directed therapies (enzalutamide (Enz) and abiraterone acetate (AA)), have emerged and been approved for the management of castration-resistant prostate cancer (CRPC). There are still debates over their efficacy and clinical benefits. This meta-analysis aimed to investigate the efficacy and safety of sipuleucel-T and AR-directed therapies in patients with CRPC. RevMan 5.1 was used for pooled analysis and analysis of publication bias. Seven studies were included in the meta-analysis, with three studies in sipuleucel-T (totally 737 patients, 488 patients in treatment group, and 249 patients in placebo group) and four in AR-directed therapies (totally 5,199 patients, 3,015 patients in treatment group, and 2,184 patients in placebo group). Treatment with sipuleucel-T significantly improved overall survival in patients with CRPC and was not associated with increased risk of adverse event of grade ≥3 (p > 0.05). However, treatment with sipuleucel-T did not improve time-to-progression and reduction of prostate-specific antigen (PSA) level ≥50% was not significantly different from that with placebo. AR-directed therapies significantly improved overall survival in patients with CRPC and improved time-to-progression and reduction of PSA level ≥50%. AR-directed therapies did not increase risk of adverse event of grade ≥3 (p > 0.05).

Targeting the N-Terminal Domain of the Androgen Receptor: A New Approach for the Treatment of Advanced Prostate Cancer

: Despite the recent approval and widespread use of abiraterone acetate and enzalutamide for the treatment of castration-resistant prostate cancer (CRPC), this disease still poses significant management challenges because of various tumor escape mechanisms, including those that allow androgen receptor (AR) signaling to remain active. These AR-related resistance mechanisms include AR gene amplification or overexpression, constitutively active ligand-independent AR splice variants, and gain-of-function mutations involving the AR ligand-binding domain (LBD), among others. Therefore, the development of AR-targeted therapies that function independently of the LBD represents an unmet medical need and has the potential to overcome many of these resistance mechanisms. This article discusses N-terminal domain (NTD) inhibition as a novel concept in the field of AR-directed therapies for prostate cancer. AR NTD-targeting agents have the potential to overcome shortcomings of current hormonal therapies by inhibiting all forms of AR-mediated transcriptional activity, and as a result, may affect a broader AR population including mutational and splice variant ARs. Indeed, the first clinical trial of an AR NTD inhibitor is now underway.

IMPLICATIONS FOR PRACTICE

Because of emerging resistance mechanisms that involve the ligand-binding domain of the androgen receptor (AR), there is currently no effective treatment addressing tumor escape mechanisms related to current AR-targeted therapies. Many patients still demonstrate limited clinical response to current hormonal agents, and castration-resistant prostate cancer remains a lethal disease. Intense research efforts are under way to develop therapies to target resistance mechanisms, including those directed at other parts of the AR molecule. A novel small-molecule agent, EPI-506, represents a new pharmaceutical class, AR N-terminal domain inhibitors, and shows preclinical promise to overcome many known resistance mechanisms related to novel hormonal therapies.

Activation of AMPKα mediates additive effects of solamargine and metformin on suppressing MUC1 expression in castration-resistant prostate cancer cells

Prostate cancer is the second most common cause of cancer-related deaths worldwide. The mucin 1 (MUC1) oncoprotein is highly expressed in human prostate cancers with aggressive features. However, the role for MUC1 in occurrence and progression of castration-resistant prostate cancer (CRPC) remained elusive. In this study, we showed that solamargine, a major steroidal alkaloid glycoside, inhibited the growth of CRPC cells, which was enhanced in the presence of metformin. Furthermore, we found that solamargine increased phosphorylation of AMPKα, whereas reducing the protein expression and promoter activity of MUC1. A greater effect was observed in the presence of metformin. In addition, solamargine reduced NF-κB subunit p65 protein expression. Exogenously expressed p65 resisted solamargine-reduced MUC1 protein and promoter activity. Interestingly, exogenously expressed MUC1 attenuated solamargine-stimulated phosphorylation of AMPKα and, more importantly reversed solamargine-inhibited cell growth. Finally, solamargine increased phosphorylation of AMPKα, while inhibiting MUC1, p65 and tumor growth were observed in vivo. Overall, our results show that solamargine inhibits the growth of CRPC cells through AMPKα-mediated inhibition of p65, followed by reduction of MUC1 expression in vitro and in vivo. More importantly, metformin facilitates the antitumor effect of solamargine on CRPC cells.