Management of castrate resistant prostate cancer-recent advances and optimal sequence of treatments

Immunotherapeutic role of cabazitaxel treatment in the activation of TLR3 signalling in metastatic castration-resistant prostate cancer in vitro

BACKGROUND

The activation of toll like receptors (TLR) potentially affect the inflammatory tumor microenvironment and thus is associated with tumor growth or inhibition. Cabazitaxel (CAB) has been effectively used for the treatment of metastatic castration-resistant prostate cancer (mCRPC). However, the immune regulatory role of CAB in the tumor microenvironment is not clear. In this context, we for the first time assessed the immunotherapeutic role of CAB in the TLR3 signalling following activation of Poly I:C in mCRPC cells.

METHODS AND RESULTS

The cytotoxic and apoptotic effects of CAB with the induction of Poly I:C were determined by WST-1, Annexin V, acridine orange, RT-PCR analysis, ELISA assay and immunofluorescence staining in DU-145 mCRPC and HUVEC control cells. Our findings showed that CAB treatment with Poly I:C significantly suppressed the proliferation of DU-145 cells through the induction of apoptosis and caspase activation. Additionally, higher concentration of CAB mediated the activation of TLR3 via increased cytoplasmic and nuclear expression of TLR3, TICAM-1 and IRF-3 in mCRPC cells.

CONCLUSIONS

Co-treatment of CAB and Poly I:C was more effective in mCRPC cells with less toxicity in control cells. However, further investigations are required to elucidate the molecular mechanisms of TLRs signalling upon CAB treatment at the molecular level to further validate the immunotherapeutic efficacy of CAB in mCRPC.

Identification of lipidomic profiles associated with drug-resistant prostate cancer cells

BACKGROUND

The association of circulating lipids with clinical outcomes of drug-resistant castration-resistant prostate cancer (DR-CRPC) is not fully understood. While it is known that increases in select lipids correlate to decreased survival, neither the mechanisms mediating these alterations nor the correlation of resistance to drug treatments is well characterized.

METHODS

This gap-in-knowledge was addressed using in vitro models of non-cancerous, hormone-sensitive, CRPC and drug-resistant cell lines combined with quantitative LC-ESI-Orbitrap-MS (LC-ESI-MS/MS) lipidomic analysis and subsequent analysis such as Metaboanalyst and Lipid Pathway Enrichment Analysis (LIPEA).

RESULTS

Several lipid regulatory pathways were identified that are associated with Docetaxel resistance in prostate cancer (PCa). These included those controlling glycerophospholipid metabolism, sphingolipid signaling and ferroptosis. In total, 7460 features were identified as being dysregulated between the cell lines studied, and 21 lipid species were significantly altered in drug-resistant cell lines as compared to nonresistant cell lines. Docetaxel resistance cells (PC3-Rx and DU145-DR) had higher levels of phosphatidylcholine (PC), oxidized lipid species, phosphatidylethanolamine (PE), and sphingomyelin (SM) as compared to parent control cells (PC-3 and DU-145). Alterations were also identified in the levels of phosphatidic acid (PA) and diacylglyceride (DAG), whose levels are regulated by Lipin (LPIN), a phosphatidic acid phosphatase that converts PA to DAG. Data derived from cBioPortal demonstrated a population of PCa patients expressing mutations aligning with amplification of LPIN1, LPIN2 and LPIN3 genes. Lipin amplification in these genes correlated to decreased survival in these patients. Lipin-1 mRNA expression also showed a similar trend in PCa patient data. Lipin-1, but not Lipin-2 or - 3, was detected in several prostate cancer cells, and was increased in 22RV1 and PC-3 cell lines. The increased expression of Lipin-1 in these cells correlated with the level of PA.

CONCLUSION

These data identify lipids whose levels may correlate to Docetaxel sensitivity and progression of PCa. The data also suggest a correlation between the expression of Lipin-1 in cells and patients with regards to prostate cancer cell aggressiveness and patient survivability. Ultimately, these data may be useful for identifying markers of lethal and/or metastatic prostate cancer.

Real-world incidence and burden of adverse events among non-metastatic prostate cancer patients treated with secondary hormonal therapies following androgen deprivation therapy

Aims: To describe the incidence and identify prognostic factors of central nervous system (CNS) adverse events (AEs) and any AEs (CNS, skin rash, or fracture) and evaluate the healthcare resource utilization (HCRU), direct medical costs, and therapy discontinuation associated with these AEs among non-metastatic prostate cancer (nmPC) patients who received secondary hormone therapies.Methods and results: nmPC patients who had initiated secondary hormonal therapy with enzalutamide, bicalutamide, or abiraterone ≥1 year after androgen deprivation therapy (ADT) were identified in the MarketScan database. Survival analyses were used to describe the incidence of CNS or any AEs. Annual HCRU and costs were compared across patient groups (CNS AE vs no CNS AE; any AE vs no AE) using propensity score weighted generalized linear models. Multivariate Cox proportional hazards models were used to identify AE predictors and compare risks of discontinuation.Results: The analysis included 532 patients who initiated secondary hormonal therapies, among whom 201 (38%) and 244 (46%) experienced a CNS AE and any AE, respectively. Median times to CNS AE and any AE from therapy initiation were 17.90 and 11.00 months, respectively. Predictors of any AE were any AE in the baseline period (≤6 months before starting therapy), Charlson Comorbidity Index (CCI) score (1 vs 0), surgical castration, and older age. Predictors of CNS AEs were CNS AE in the baseline period and CCI score (1 vs 0). CNS and any AEs were associated with significantly higher HCRU. CNS AEs were associated with significantly higher incremental total medical costs ($18,522). CNS AEs and any AEs significantly increased therapy discontinuation risk by 48% and 38%, respectively.Conclusions: AEs increase the economic burden and therapy discontinuation among nmPC patients receiving secondary hormonal therapies subsequent to ADTs. These patients should be carefully evaluated for AEs to reduce therapy discontinuation, HCRU, and direct medical costs.

Treatment characteristics for nonmetastatic castration-resistant prostate cancer in the United States, Europe and Japan

Aim: We conducted this study to describe nonmetastatic castration-resistant prostate cancer (nmCRPC) patient characteristics and treatment patterns in the US, Europe and Japan. Materials & methods: Descriptive analyses were conducted using the 2015–2017 Ipsos Global Oncology Monitor Database. Results: A total of 2065 (442 in the US, 509 in Europe and 1114 in Japan) patients (median age: 74–80 years; stage III at diagnosis : 38.5%; Eastern Cooperative Oncology Group [ECOG] score ≤1: 79.4%; treated by urologist : 88.4%) were included in the analytic cohort. Luteinizing hormone-releasing hormone agonists and antiandrogens were the most commonly used first regimen treatments. With subsequent nmCRPC regimens their use decreased, while the use of chemotherapy, corticosteroids, androgen synthesis inhibitors and second-generation androgen receptor inhibitors increased. Conclusion: These data represent real-world treatment patterns in nmCRPC.

Androgen Receptor Deregulation Drives Bromodomain-Mediated Chromatin Alterations in Prostate Cancer

Global changes in chromatin accessibility may drive cancer progression by reprogramming transcription factor (TF) binding. In addition, histone acetylation readers such as bromodomain-containing protein 4 (BRD4) have been shown to associate with these TFs and contribute to aggressive cancers including prostate cancer (PC). Here, we show that chromatin accessibility defines castration-resistant prostate cancer (CRPC). We show that the deregulation of androgen receptor (AR) expression is a driver of chromatin relaxation and that AR/androgen-regulated bromodomain-containing proteins (BRDs) mediate this effect. We also report that BRDs are overexpressed in CRPCs and that ATAD2 and BRD2 have prognostic value. Finally, we developed gene stratification signature (BROMO-10) for bromodomain response and PC prognostication, to inform current and future trials with drugs targeting these processes. Our findings provide a compelling rational for combination therapy targeting bromodomains in selected patients in which BRD-mediated TF binding is enhanced or modified as cancer progresses.

Circulating AR copy number and outcome to enzalutamide in docetaxel-treated metastatic castration-resistant prostate cancer

In the present study, we aimed to evaluate the association of circulating AR copy number (CN) and outcome in a cohort of patients with advanced castration-resistant prostate cancer (CRPC) treated with enzalutamide after docetaxel. Fifty-nine CRPC patients were evaluated. AR CN was analyzed with real-time and digital PCR in the serum collected at starting of treatment. Progressive disease was defined on the basis of Prostate Cancer Working Group 2 criteria. AR CN gain was found in 21 of 59 (36%) patients. Median baseline PSA, alkaline phosphatase and lactate dehydrogenase levels were higher in the AR CN gained group (p = 0.007, p = 0.003, p = 0.0009, respectively). Median PFS of patients with AR CN gain was 2.4 (95%CI: 1.9-3.2) vs. 4.0 months (95%CI: 3.0-6.5) of those with no gain (p = 0.0004). Median OS of patients with AR CN gain was 6.1 (95%CI: 3.4-8.6) vs. 14.1 months (95%CI: 8.2-20.5) of those with no gain (p = 0.0003). At multivariate analysis, PSA decline ≥ 50% and AR CN showed a significant association with PFS (p = 0.008 and p = 0.002, respectively) and OS (p = 0.009 and p = 0.001, respectively). These findings indicate that the detection of circulating AR CN gain is a promising non-invasive biomarker for outcome prediction to enzalutamide treatment in CRPC patients.

What is the role of sipuleucel-T in the treatment of patients with advanced prostate cancer? An update on the evidence

Prostate cancer is the most common cancer in men and the second most deadly. About one-third of patients with prostate cancer will develop metastatic disease. We discuss the six United States Food and Drug Administration (FDA) approved treatments for metastatic castrate-resistant prostate cancer (mCRPC) with a strong focus on sipuleucel-T. Sipuleucel-T is the first immunotherapy shown to improve survival in asymptomatic or minimally-symptomatic mCRPC. Herein, we discuss the proposed mechanism of sipuleucel-T and its synthesis. We describe in detail the three randomized controlled trials (RTCs) that led to its approval. We also compiled the newest research regarding use of sipuleucel-T with other agents and in different patient populations. Finally, we discuss the current ongoing trials.

Comparative analysis of the effectiveness of abiraterone before and after docetaxel in patients with metastatic castration-resistant prostate cancer

AIM: To study the efficacy and safety of abiraterone in patients with and without prior chemotherapy.

METHODS: The databases including PubMed and abstracts presented at the American Society of Clinical Oncology meetings up to April 2014 were systematically searched. Eligible studies included randomized controlled trials (RCTs) in which abiraterone plus prednisone was compared to placebo plus prednisone in metastatic castration-resistant prostate cancer (CRPC) patients. The summary incidence, relative risk, hazard ratio and 95%CI were calculated using random or fixed-effects models. Heterogeneity test was performed to test between-study differences in efficacy and toxicity.

RESULTS: A total of two phase III RCTs were included in our analysis, with metastatic CPRC patients before (n = 1088) and after chemotherapy (n = 1195). Prior chemotherapy did not significantly alter the effect of abiraterone on overall survival (P = 0.92) and prostate-specific antigen (PSA) progression-free survival (P = 0.13), but reduced its effect on radiographic-progression-free survival (P = 0.04), objective response rate (P < 0.001), and PSA response rate (P < 0.001). Prior chemotherapy significantly increased the specific risk of fluid retention and edema (P < 0.001) and hypokalemia (P < 0.001), but decreased the risk of all-grade hypertension (P < 0.001) attributable to abiraterone. There was no significant difference of cardiac disorders associated with abiraterone between the two settings (P = 0.58).

CONCLUSION: Prior chemotherapy may reduce the effectiveness of abiraterone in patients with metastatic CRPC.

UK single centre experience of rare and atypical variant of castrate-resistant prostate cancer: Poorly differentiated neuroendocrine small-cell carcinoma

Background:

We report on the emergence of a rare and atypical variant of castrate-resistant prostate cancer (CRPC) that is characterised by transformation into poorly differentiated neuroendocrine small-cell carcinoma (NSCC). The existence of this variant was previously described in isolated case reports and small case-studies, but as yet there has been no UK series reported in the literature.

Methods:

Between January 2010 and January 2014, eight cases were presented in our local multi-disciplinary team meeting having a diagnosis of NSCC arising on a background of prostate cancer treated with androgen deprivation therapy. We performed a retrospective review of the clinical records of these patients, to identify the mode of presentation, diagnostic investigations, pathological characteristics, and subsequent treatment and survival outcomes.

Results:

The median patient age was 77 years (range, 68 – 84), with a median time interval of 25 months (range, 7 – 83) between the original diagnosis and subsequent transformation to NSCC. The median prostate-specific antigen (PSA) was 4 ng/ml, at presentation. Most patients presented with local progression, combined with high-volume and atypical sites of metastasis (e.g. brain, pancreas and penis). Patients developed a good initial response to platinum-based chemotherapy, but responses were short-lived and prognosis poor, with a median overall survival (OS) of 8 months.

Conclusion:

Prostate NSCC represents an atypical variant of CRPC with significant therapeutic and prognostic implications. Based on our observations, we have proposed a clinical algorithm for early diagnosis and appropriate management of these patients.

Combination of the PI3K inhibitor ZSTK474 with a PSMA-targeted immunotoxin accelerates apoptosis and regression of prostate cancer

The phosphoinositide 3-kinase (PI3K) pathway is activated in most advanced prostate cancers, yet so far treatments with PI3K inhibitors have been at best tumorostatic in preclinical cancer models and do not show significant antitumor efficacy in clinical trials. Results from tissue culture experiments in prostate cancer cells suggest that PI3K inhibitors should be combined with other cytotoxic agents; however, the general toxicity of such combinations prevents translating these experimental data into preclinical and clinical models. We investigated the emerging concept of tumor-targeted synthetic lethality in prostate cancer cells by using the pan-PI3K inhibitor ZSTK474 and the immunotoxin J591PE, a protein chimera between the single-chain variable fragment of the monoclonal antibody J591 against the prostate-specific membrane antigen (PSMA) and the truncated form of the Pseudomonas aeruginosa exotoxin A (PE38QQR). The combination of ZSTK474 and J591PE increased apoptosis within 6 hours and cell death (monitored at 24-48 hours) in the PSMA-expressing cells LNCaP, C4-2, and C4-2Luc but not in control cells that do not express PSMA (PC3 and BT549 cells). Mechanistic analysis suggested that induction of apoptosis requires Bcl-2-associated death promoter (BAD) dephosphorylation and decreased expression of myeloid leukemia cell differentiation protein 1 (MCL-1). A single injection of ZSTK474 and J591PE into engrafted prostate cancer C4-2Luc cells led to consistent and stable reduction of luminescence within 6 days. These results suggest that the combination of a PI3K inhibitor and a PSMA-targeted protein synthesis inhibitor toxin represents a promising novel strategy for advanced prostate cancer therapy that should be further investigated.