Clinical validation of circulating GDF15/MIC-1 as a marker of response to docetaxel and survival in men with metastatic castration-resistant prostate cancer

BACKGROUND

Elevated circulating growth differentiation factor (GDF15/MIC-1), interleukin 4 (IL4), and IL6 levels were associated with resistance to docetaxel in an exploratory cohort of men with metastatic castration-resistant prostate cancer (mCRPC). This study aimed to establish level 2 evidence of cytokine biomarker utility in mCRPC.

METHODS

IntVal: Plasma samples at baseline (BL) and Day 21 docetaxel (n = 120). ExtVal: Serum samples at BL and Day 42 of docetaxel (n = 430). IL4, IL6, and GDF15 levels were measured by ELISA. Monocytes and dendritic cells were treated with 10% plasma from men with high or low GDF15 or recombinant GDF15.

RESULTS

IntVal: Higher GDF15 levels at BL and Day 21 were associated with shorter overall survival (OS) (BL; p = 0.03 and Day 21; p = 0.004). IL4 and IL6 were not associated with outcomes. ExtVal: Higher GDF15 levels at BL and Day 42 predicted shorter OS (BL; p < 0.0001 and Day 42; p < 0.0001). Plasma from men with high GDF15 caused an increase in CD86 expression on monocytes (p = 0.03), but was not replicated by recombinant GDF15.

CONCLUSIONS

Elevated circulating GDF15 is associated with poor prognosis in men with mCRPC receiving docetaxel and may be a marker of changes in the innate immune system in response to docetaxel resistance. These findings provide a strong rationale to consider GDF15 as a biomarker to guide a therapeutic trial of drugs targeting the innate immune system in combination with docetaxel in mCRPC.

Plasma Lipidomic Profiling Identifies Elevated Triglycerides as Potential Risk Factor in Chemotherapy-Induced Peripheral Neuropathy

PURPOSE

Chemotherapy-induced peripheral neuropathy (CIPN) is a dose-limiting side effect of cytotoxic cancer treatment, often necessitating dose reduction (DR) or chemotherapy discontinuation (CD). Studies on peripheral neuropathy related to chemotherapy, obesity, and diabetes have implicated lipid metabolism. This study examined the association between circulating lipids and CIPN.

METHODS

Lipidomic analysis was performed on plasma samples from 137 patients receiving taxane-based treatment. CIPN was graded using Total Neuropathy Score-clinical version (TNSc) and patient-reported outcome measure European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-CIPN (EORTC-QLQ-CIPN20).

RESULTS

A significant proportion of elevated baseline lipids were associated with high-grade CIPN defined by TNSc and EORTC-QLQ-CIPN20 including triacylglycerols (TGs). Multivariable Cox regression on lipid species, adjusting for BMI, age, and diabetes, showed several elevated baseline TG associated with shorter time to DR/CD. Latent class analysis identified two baseline lipid profiles with differences in risk of CIPN (hazard ratio, 2.80 [95% CI, 1.50 to 5.23]; P = .0013). The higher risk lipid profile had several elevated TG species and was independently associated with DR/CD when modeled with other clinical factors (diabetes, age, BMI, or prior numbness/tingling).

CONCLUSION

Elevated baseline plasma TG is associated with an increased risk of CIPN development and warrants further validation in other cohorts. Ultimately, this may enable therapeutic intervention.

Modulation of Plasma Lipidomic Profiles in Metastatic Castration-Resistant Prostate Cancer by Simvastatin

Elevated circulating sphingolipids are associated with shorter overall survival and therapeutic resistance in metastatic castration-resistant prostate cancer (mCRPC), suggesting that perturbations in sphingolipid metabolism promotes prostate cancer growth. This study assessed whether addition of simvastatin to standard treatment for mCRPC can modify a poor prognostic circulating lipidomic profile represented by a validated 3-lipid signature (3LS). Men with mCRPC (n = 27) who were not on a lipid-lowering agent, were given simvastatin for 12 weeks (40 mg orally, once daily) with commencement of standard treatment. Lipidomic profiling was performed on their plasma sampled at baseline and after 12 weeks of treatment. Only 11 men had the poor prognostic 3LS at baseline, of whom five (45%) did not retain the 3LS after simvastatin treatment (expected conversion rate with standard treatment = 19%). At baseline, the plasma profiles of men with the 3LS displayed higher levels (p < 0.05) of sphingolipids (ceramides, hexosylceramides and sphingomyelins) than those of men without the 3LS. These plasma sphingolipids were reduced after statin treatment in men who lost the 3LS (mean decrease: 23−52%, p < 0.05), but not in men with persistent 3LS, and were independent of changes to plasma cholesterol, LDL-C or triacylglycerol. In conclusion, simvastatin in addition to standard treatment can modify the poor prognostic circulating lipidomic profile in mCRPC into a more favourable profile at twice the expected conversion rate.

GUIDE: a randomised non-comparative phase II trial of biomarker-driven intermittent docetaxel versus standard-of-care docetaxel in metastatic castration-resistant prostate cancer (clinical trial protocol)

Objective:

To determine the efficacy and safety of intermittent docetaxel chemotherapy guided by circulating methylated glutathione S-transferase Pi-1 (mGSTP1) in men with metastatic castration-resistant prostate cancer (CRPC).

Patients and Methods:

GUIDE (NCT04918810) is a randomised, two-arm, non-comparative phase-2 trial recruiting 120 patients at six Australian centres. Patients with Prostate Cancer Working Group-3 defined metastatic CRPC who are commencing docetaxel 75 mg/m² q3w will be pre-screened for detectable mGSTP1 at baseline ± following two cycles of treatment. Those with detectable plasma mGSTP1 at baseline that becomes undetectable after two cycles of chemotherapy will be eligible for GUIDE. Prior to Cycle 4 of docetaxel, these patients are randomised 2:1 to one of two treatment arms: Arm A (cease docetaxel and reinstitute if mGSTP1 becomes detectable) or Arm B (continue docetaxel 75 mg/m² q3w in accordance with clinician’s usual practice). The primary endpoint is radiographic progression-free survival. Secondary endpoints include time on treatment holidays, safety, patient-reported outcomes, overall survival, health resource use, and cost associated with treatment. Enrolment commenced November 2021.

Results and Conclusion:

The results of this trial will generate data on the clinical utility of mGSTP1 as a novel biomarker to guide treatment de-escalation in metastatic CRPC.

Overcoming enzalutamide resistance in metastatic prostate cancer by targeting sphingosine kinase

Background

Intrinsic resistance to androgen receptor signalling inhibitors (ARSI) occurs in 20–30% of men with metastatic castration-resistant prostate cancer (mCRPC). Ceramide metabolism may have a role in ARSI resistance. Our study's aim is to investigate the association of the ceramide-sphingosine-1-phosphate (ceramide-S1P) signalling axis with ARSI resistance in mCRPC.

Methods

Lipidomic analysis (∼700 lipids) was performed on plasma collected from 132 men with mCRPC, before commencing enzalutamide or abiraterone. AR gene aberrations in 77 of these men were identified by deep sequencing of circulating tumour DNA. Associations between circulating lipids, radiological progression-free survival (rPFS) and overall survival (OS) were examined by Cox regression. Inhibition of ceramide-S1P signalling with sphingosine kinase (SPHK) inhibitors (PF-543 and ABC294640) on enzalutamide efficacy was investigated with in vitro assays, and transcriptomic and lipidomic analyses of prostate cancer (PC) cell lines (LNCaP, C42B, 22Rv1).

Findings

Men with elevated circulating ceramide levels had shorter rPFS (HR=2·3, 95% CI=1·5–3·6, p = 0·0004) and shorter OS (HR=2·3, 95% CI=1·4–36, p = 0·0005). The combined presence of an AR aberration with elevated ceramide levels conferred a worse prognosis than the presence of only one or none of these characteristics (median rPFS time = 3·9 vs 8·3 vs 17·7 months; median OS time = 8·9 vs 19·8 vs 34·4 months). SPHK inhibitors enhanced enzalutamide efficacy in PC cell lines. Transcriptomic and lipidomic analyses indicated that enzalutamide combined with SPHK inhibition enhanced PC cell death by SREBP-induced lipotoxicity.

Interpretation

Ceramide-S1P signalling promotes ARSI resistance, which can be reversed with SPHK inhibitors.

Aberrations in circulating ceramide levels are associated with poor clinical outcomes across localised and metastatic prostate cancer

BACKGROUND

Dysregulated lipid metabolism is associated with more aggressive pathology and poorer prognosis in prostate cancer (PC). The primary aim of the study is to assess the relationship between the plasma lipidome and clinical outcomes in localised and metastatic PC. The secondary aim is to validate a prognostic circulating 3-lipid signature specific to metastatic castration-resistant PC (mCRPC).

PATIENTS AND METHODS

Comprehensive lipidomic analysis was performed on pre-treatment plasma samples from men with localised PC (N = 389), metastatic hormone-sensitive PC (mHSPC)(N = 44), or mCRPC (validation cohort, N = 137). Clinical outcomes from our previously published mCRPC cohort (N = 159) that was used to derive the prognostic circulating 3-lipid signature, were updated. Associations between circulating lipids and clinical outcomes were examined by Cox regression and latent class analysis.

RESULTS

Circulating lipid profiles featuring elevated levels of ceramide species were associated with metastatic relapse in localised PC (HR 5.80, 95% CI 3.04-11.1, P = 1 × 10^-6), earlier testosterone suppression failure in mHSPC (HR 3.70, 95% CI 1.37-10.0, P = 0.01), and shorter overall survival in mCRPC (HR 2.54, 95% CI 1.73-3.72, P = 1 × 10^-6). The prognostic significance of circulating lipid profiles in localised PC was independent of standard clinicopathological and metabolic factors (P < 0.0002). The 3-lipid signature was verified in the mCRPC validation cohort (HR 2.39, 95% CI 1.63-3.51, P = 1 × 10^-5).

CONCLUSIONS

Elevated circulating ceramide species are associated with poorer clinical outcomes across the natural history of PC. These clinically actionable lipid profiles could be therapeutically targeted in prospective clinical trials to potentially improve PC outcomes.

Review of systemic chemotherapy in unresectable colorectal peritoneal carcinomatosis

Colorectal cancer remains the third most common malignancy in Australia with the peritoneum being the second most common metastatic site. Colorectal peritoneal carcinomatosis (CPC) can be treated with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy but this is only limited to a small subset of patients. Those with inoperable disease have a particularly poor prognosis. While the ideal systemic regimen has not been defined, 5-fluorouracil-based chemotherapy regimens appear to provide overall and progression free survival benefits. The role of targeted agents such as bevacizumab (vascular endothelial growth factor inhibitor) or cetuximab (epidermal growth factor inhibitor) in the setting of CPC is still evolving. Currently, retrospective analyses have shown promising results for the use of bevacizumab in addition to systemic chemotherapy but similar results have not been seen with cetuximab or panitumumab. However, there is significant heterogeneity in the trial data, lack of prospective randomized controlled trials and demonstrated treatment variability based on age and tumour characteristics. This review summarises the current literature in regard to treatment in the unresectable CPC setting as well as discussing issues with the current data and highlighting the need for further trials.

Evaluation of a Mainstream Model of Genetic Testing for Men With Prostate Cancer

PURPOSE

To identify the approximately 12% with inherited cancer predisposition, all men with metastatic prostate cancer (mPC) should be offered germline genetic testing. This guides treatment choices and impacts cancer prevention in the family. Limited genetic services globally present a barrier to testing. This study tested a potential solution, "mainstreaming," where counseling and testing are performed by the patient's oncologist.

PATIENTS AND METHODS

Men with mPC at three Australian sites were offered germline genetic testing at their medical oncology appointment. Panel testing (ATM, BRCA1, BRCA2, BRIP1, CHEK2, EPCAM, FANCA, HOXB13, MLH1, MSH2, MSH6, NBN, PALB2, PMS2, RAD51D, and TP53) was performed on saliva/blood (Invitae, San Francisco, CA). Primary outcomes were clinician and patient satisfaction. Secondary outcomes included mutation rates and resource allocation.

RESULTS

Of 66 men offered testing, 63 (95%) accepted. Four pathogenic variants were identified (two BRCA2, one NBN, and one MSH6). Fifty patients and nine clinicians completed questionnaires. Satisfaction was high. All patients were pleased to have had testing overall, 98% (46 of 47) to have had testing at their usual oncology appointment, and all to receive results from their usual specialist, rather than a separate genetics appointment. A total of 88% (7 of 8) of clinicians felt confident, and all were satisfied with mainstreaming. Mainstreaming was resource efficient, requiring 87% fewer genetic consultations than traditional genetic counseling.

CONCLUSION

This study demonstrates that mainstreaming of men with mPC is feasible, resource efficient, and satisfactory for clinicians and patients. Widespread implementation as standard of care would facilitate timely access to genetic testing for men with mPC.

Assessment of Periprostatic and Subcutaneous Adipose Tissue Lipolysis and Adipocyte Size from Men with Localized Prostate Cancer

The prostate is surrounded by periprostatic adipose tissue (PPAT), the thickness of which has been associated with more aggressive prostate cancer (PCa). There are limited data regarding the functional characteristics of PPAT, how it compares to subcutaneous adipose tissue (SAT), and whether in a setting of localized PCa, these traits are altered by obesity or disease aggressiveness. PPAT and SAT were collected from 60 men (age: 42–78 years, BMI: 21.3–35.6 kg/m²) undergoing total prostatectomy for PCa. Compared to SAT, adipocytes in PPAT were smaller, had the same basal rates of fatty acid release (lipolysis) yet released less polyunsaturated fatty acid species, and were more sensitive to isoproterenol-stimulated lipolysis. Basal lipolysis of PPAT was increased in men diagnosed with less aggressive PCa (Gleason score (GS) ≤ 3 + 4) compared to men with more aggressive PCa (GS ≥ 4 + 3) but no other measured adipocyte parameters related to PCa aggressiveness. Likewise, there was no difference in PPAT lipid biology between lean and obese men. In conclusion, lipid biological features of PPAT do differ from SAT; however, we did not observe any meaningful difference in ex vivo PPAT biology that is associated with PCa aggressiveness or obesity. As such, our findings do not support a relationship between altered PCa behavior in obese men and the metabolic reprogramming of PPAT.

Mainstream consent programs for genetic counseling in cancer patients: A systematic review

As demand for germline genetic testing for cancer patients increases, novel methods of genetic counseling are required. One such method is the mainstream consent pathway, whereby a member of the oncology team (rather than a genetic specialist) is responsible for counseling, consenting, and arranging genetic testing for cancer patients. We systematically reviewed the literature for evidence evaluating mainstream pathways for patients with breast, ovarian, colorectal, and prostate cancer. Medline, EMBASE, and Cochrane Library were searched for studies that met inclusion and exclusion criteria. Article references were checked for additional studies. Trial databases were searched for ongoing studies. Of the 13 papers that met inclusion criteria, 11 individual study groups were identified (two study groups had two publications each). Ten of the 11 studies evaluated the acceptability, feasibility, and impact of BRCA testing for patients and/or clinicians in different clinical settings in breast and ovarian cancer, while the final study explored the attitudes of colorectal specialists toward genetic testing for colorectal cancer. None involved prostate cancer. Overall, mainstream pathways were acceptable and feasible. Medical oncologist- and nurse-driven pathways were particularly successful, with both patients and clinicians satisfied with this process. Although the content of pretest counseling was less consistent compared with counseling via the traditional model, patients were largely satisfied with the education they received. Further research is required to evaluate the mainstream pathway for men with prostate cancer.

Pharmacodynamics effects of CDK4/6 inhibitor LEE011 (ribociclib) in high-risk, localised prostate cancer: a study protocol for a randomised controlled phase II trial (LEEP study: LEE011 in high-risk, localised Prostate cancer)

INTRODUCTION

Despite the development of new therapies for advanced prostate cancer, it remains the most common cause of cancer and the second leading cause of cancer death in men. It is critical to develop novel agents for the treatment of prostate cancer, particularly those that target aspects of androgen receptor (AR) signalling or prostate biology other than inhibition of androgen synthesis or AR binding. Neoadjuvant pharmacodynamic studies allow for a rational approach to the decisions regarding which targeted therapies should progress to phase II/III trials. CDK4/6 inhibitors have evidence of efficacy in breast cancer, and have been shown to have activity in preclinical models of hormone sensitive and castrate resistant prostate cancer. The LEEP trial aims to assess the pharmacodynamic effects of LEE011 (ribociclib), an orally bioavailable and highly selective CDK4/6 inhibitor, in men undergoing radical prostatectomy for high-risk, localised prostate cancer.

METHODS AND ANALYSIS

The multicentre randomised, controlled 4:1 two-arm, phase II, open label pharmacodynamic study will recruit 47 men with high risk, localised prostate cancer who are planned to undergo radical prostatectomy. Participants who are randomised to receive the study treatment will be treated with LEE011 400 mg daily for 21 days for one cycle. The primary endpoint is the frequency of a 50% reduction in Ki-67 proliferation index from the pretreatment prostate biopsy compared to that present in prostate cancer tissue from radical prostatectomy. Secondary and tertiary endpoints include pharmacodynamic assessment of CDK4/6 cell cycle progression via E2F levels, apoptotic cell death by cleaved caspase-3, changes in serum and tumour levels of Prostate Specific Antigen (PSA), pathological regression, safety via incidence of adverse events and exploratory biomarker analysis.

ETHICS AND DISSEMINATION

The protocol was approved by a central ethics review committee (St Vincent's Hospital HREC) for all participating sites (HREC/17/SVH/294). Results will be disseminated in peer-reviewed journals and at scientific conferences.

DRUG SUPPLY

Novartis.

PROTOCOL VERSION

2.0, 30 May 2019 TRIAL REGISTRATION NUMBER: Australian New Zealand Clinical Trials Registry (ACTRN12618000354280).

An analysis of a multiple biomarker panel to better predict prostate cancer metastasis after radical prostatectomy

A plethora of individual candidate biomarkers for predicting biochemical relapse in localized prostate cancer (PCa) have been proposed. Combined biomarkers may improve prognostication, and ensuring validation against more clinically relevant endpoints are required. The Australian PCa Research Centre NSW has contributed to numerous studies of molecular biomarkers associated with biochemical relapse. In the current study, these biomarkers were re-analyzed for biochemical relapse, metastatic relapse and PCa death with extended follow-up. Biomarkers of significance were then used to develop a combined prognostic model for clinical outcomes and validated in a large independent cohort. The discovery cohort (n = 324) was based on 12 biomarkers with a median follow-up of 16 years. Seven biomarkers were significantly associated with biochemical relapse. Three biomarkers were associated with metastases: AZGP1, Ki67 and PML. Only AZGP1 was associated with PCa death. In their individual and combinational forms, AZGP1 and Ki67 as a dual BM signature was the most robust predictor of metastatic relapse (AUC 0.762). The AZPG1 and Ki67 signature was validated in an independent cohort of 347 PCa patients. The dual BM signature of AZGP1 and Ki67 predicted metastasis in the univariable (HR 7.2, 95% CI, 1.6-32; p = 0.01) and multivariable analysis (HR 5.4, 95% CI, 1.2-25; p = 0.03). The dual biomarker signature marginally improved risk prediction compared to AZGP1 alone (AUC 0.758 versus 0.738, p < 0.001). Our findings indicate that biochemical relapse is not an adequate surrogate for metastasis or PCa death. The dual biomarker signature of AZGP1 and Ki67 offers a small benefit in predicting metastasis over AZGP1 alone.

A prospective multicentre phase III validation study of AZGP1 as a biomarker in localized prostate cancer

Background

Prostate cancers (PCs) with similar characteristics at the time of diagnosis can have very different disease outcomes. Conventional biomarkers of PC still lack precision in identifying individuals at high risk of PC recurrence. While many candidate biomarkers are proposed in the literature, few are in clinical practice as they lack rigorous validation. This study prospectively enrolled an independent phase III cohort to evaluate the clinical utility of zinc-alpha 2-glycoprotein (AZGP1) as a prognostic biomarker in localized PC.

Patients and methods

In our multicentre, prospective phase III study, AZGP1 status in 347 radical prostatectomy specimens was assayed by immunohistochemistry in a NATA-accredited laboratory. The AZGP1 score was assessed in a multivariable model incorporating established prognostic factors. We also report extended outcomes from our previous phase II study. The primary endpoint was biochemical relapse-free survival (BRFS). Secondary endpoints were metastasis-free survival (MFS) and PC-specific survival (PCSS).

Results

In the phase II cohort, with a median follow-up of 15.8 years, low/absent AZGP1 expression was an independent predictor of poor BRFS (HR, 1.4; 95% CI, 1.1-1.9; P = 0.03), MFS (HR, 2.8; 95% CI, 1.2-6.6; P = 0.02) and PCSS (HR, 3.8; 95% CI, 1.5-9.5; P = 0.005). These results were validated in our prospective phase III cohort. Low/absent AZGP1 expression independently predicted for BRFS (HR, 1.9; 95% CI, 1.1-3.3; P = 0.02), with shorter MFS (HR, 2.0; 95% CI, 1.1-3.4; P = 0.02). AZGP1 improved the discriminatory value when incorporated into existing prognostic risk models.

Conclusion

Our study provides prospective phase III validation that absent/low AZGP1 expression provides independent prognostic value in PC. This study provides robust evidence for the incorporation of this biomarker into clinical practice.

A distinct plasma lipid signature associated with poor prognosis in castration-resistant prostate cancer

Lipids are known to influence tumour growth, inflammation and chemoresistance. However, the association of circulating lipids with the clinical outcome of metastatic castration-resistant prostate cancer (CRPC) is unknown. We investigated associations between the plasma lipidome and clinical outcome in CRPC. Lipidomic profiling by liquid chromatography-tandem mass spectrometry was performed on plasma samples from a Phase 1 discovery cohort of 96 CRPC patients. Results were validated in an independent Phase 2 cohort of 63 CRPC patients. Unsupervised analysis of lipidomic profiles (323 lipid species) classified the Phase 1 cohort into two patient subgroups with significant survival differences (HR 2.31, 95% CI 1.44-3.68, p = 0.0005). The levels of 46 lipids were individually prognostic and were predominantly sphingolipids with higher levels associated with poor prognosis. A prognostic three-lipid signature was derived (ceramide d18:1/24:1, sphingomyelin d18:2/16:0, phosphatidylcholine 16:0/16:0) and was also associated with shorter survival in the Phase 2 cohort (HR 4.8, 95% CI 2.06-11.1, p = 0.0003). The signature was an independent prognostic factor when modelled with clinicopathological factors or metabolic characteristics. The association of plasma lipids with CRPC prognosis suggests a possible role of these lipids in disease progression. Further research is required to determine if therapeutic modulation of the levels of these lipids by targeting their metabolic pathways may improve patient outcome.

Somatic mutations in salivary duct carcinoma and potential therapeutic targets

Background

Salivary duct carcinomas (SDCa) are rare highly aggressive malignancies. Most patients die from distant metastatic disease within three years of diagnosis. There are limited therapeutic options for disseminated disease.

Results

11 cases showed androgen receptor expression and 6 cases showed HER2 amplification. 6 Somatic mutations with additional available targeted therapies were identified: EGFR (p.G721A: Gefitinib), PDGFRA (p.H845Y: Imatinib and Crenolanib), PIK3CA (p.H1047R: Everolimus), ERBB2 (p.V842I: Lapatinib), HRAS (p.Q61R: Selumetinib) and KIT (p.T670I: Sorafenib). Furthermore, alterations in PTEN, PIK3CA and HRAS that alter response to androgen deprivation therapy and HER2 inhibition were also seen.

Materials and Methods

Somatic mutation analysis was performed on DNA extracted from 15 archival cases of SDCa using the targeted Illumina TruSeq Amplicon Cancer Panel. Potential targetable genetic alterations were identified using extensive literature and international somatic mutation database (COSMIC, KEGG) search. Immunohistochemistry for androgen receptor and immunohistochemistry and fluorescent in situ hybridization for HER2 were also performed.

Conclusions

SDCa show multiple somatic mutations, some that are amenable to pharmacologic manipulation and others that confer resistance to treatments currently under investigation. These findings emphasize the need to develop testing and treatment strategies for SDCa.

Phase 2 study of circulating microRNA biomarkers in castration-resistant prostate cancer

Background:

Biomarkers of therapeutic response and prognosis are needed to assist in the sequencing of treatments for metastatic castration-resistant prostate cancer (CRPC). Previously in a Phase 1 discovery study, we identified 14 circulating microRNAs that were associated with response to docetaxel chemotherapy or overall survival. We performed a Phase 2 validation study to verify these findings.

Methods:

Using real-time PCR, the levels of the 14 microRNAs were measured in plasma collected before and after the first cycle of docetaxel from a Phase 2 cohort of 89 patients.

Results:

The microRNAs were not associated with docetaxel response in the Phase 2 cohort. Higher baseline levels of six microRNAs, predominantly of the miR-200 family, were confirmed to be associated with shorter overall survival. A microRNA signature comprising these six microRNAs predicted high-risk patients in the Phase 2 cohort with a hazard ratio of 4.12 (95% CI 2.20–7.70, P=0.000001). The signature was an independent predictor in multivariable analysis with clinicopathological factors.

Conclusions:

The association of circulating microRNAs with overall survival suggests their involvement in CRPC progression.

Loss of AZGP1 as a Superior Predictor of Relapse in Margin-Positive Localized Prostate Cancer

BACKGROUND

Positive surgical margins (PSMs) in localized prostate cancer (PC) confer a two- to three-fold increased risk of biochemical relapse (BR). Absent/weak AZGP1 expression and Gleason grade ≥4 at the margin are each independent predictors of BR in patients with PSMs. Our study aimed to determine whether the biomarkers AZGP1 expression and Gleason grade at the site of a PSM are significant independent markers of biochemical and clinical relapse (CR) when modeled together and whether one of these biomarkers may be superior in its capacity to predict outcome.

METHODS

A cohort of 275 consecutive patients with margin-positive localized PC following surgery were assessed for Gleason grade and AZGP1 expression at the PSM. BR-free survival was the primary end-point, while CR-free survival and PC-specific death were secondary endpoints. Kaplan-Meier Analysis and Cox Proportional Hazards Modeling were performed.

RESULTS

Absent AZGP1 expression was significantly associated with increased risk of BR (P = 0.001) and PC-specific death (P = 0.02). Gleason grade ≥4 at PSM was associated with BR (P = 0.02), CR (P = 0.003), and PC-specific death (P = 0.004). On multivariable analysis, absent AZGP1 expression remained an independent predictor of BR (HR 2.4, 95%CI 1.5-3.9, P < 0.001) when modeled with Gleason grade at margin (HR 1.3, 95%CI 0.9-1.9, P = 0.16), preoperative PSA (P = 0.002), seminal vesicle involvement (P = 0.002), extraprostatic extension (P = 0.001), Gleason score (P = 0.01), adjuvant treatment (P = 0.75), linear length of the involved margin (P = 0.001) and margin number (P = 0.09).

CONCLUSION

Absent AZGP1 expression is an independent predictor of BR in margin-positive localized PC and is associated with increased PC-specific mortality in a Phase II study. Absent AZGP1 expression was superior to Gleason grade at PSM in predicting relapse and should be incorporated into subsequent clinical trials of post-operative radiotherapy in men with margin-positive PC. Prostate 76:1491-1500, 2016. © 2016 Wiley Periodicals, Inc.

Methylated circulating tumor DNA in blood: power in cancer prognosis and response

Circulating tumor DNA (ctDNA) in the plasma or serum of cancer patients provides an opportunity for non-invasive sampling of tumor DNA. This 'liquid biopsy' allows for interrogations of DNA such as quantity, chromosomal alterations, sequence mutations and epigenetic changes, and can be used to guide and improve treatment throughout the course of the disease. This tremendous potential for real-time 'tracking' in a cancer patient has led to substantial research efforts in the ctDNA field. ctDNA can be distinguished from non-tumor DNA by the presence of tumor-specific mutations and copy number variations, and also by aberrant DNA methylation, with both DNA sequence and methylation changes corresponding to those found in the tumor. Aberrant methylation of specific promoter regions can be a very consistent feature of cancer, in contrast to mutations, which typically occur at a wide range of sites. This consistency makes ctDNA methylation amenable to the design of widely applicable clinical assays. In this review, we examine ctDNA methylation in the context of monitoring disease status, treatment response and determining the prognosis of cancer patients.

Cytokine profiling of docetaxel-resistant castration-resistant prostate cancer

Background:

Docetaxel improves symptoms and survival in metastatic castration-resistant prostate cancer (CRPC). However, ∼50% of patients are chemoresistant. This study examined whether changes in cytokine levels predict for docetaxel resistance in vitro and in a clinical cohort.

Methods:

PC3 cells or their docetaxel-resistant subline (PC3Rx) were co-cultured with U937 monocytes, with and without docetaxel treatment, and cytokine levels were measured. The circulating levels of 28 cytokines were measured pre-/post cycle 1 of docetaxel from 55 men with CRPC, and compared with prostate-specific antigen (PSA) response.

Results:

PC3Rx-U937 co-culture expressed more cytokines, chiefly markers of alternative macrophage differentiation, compared with PC3-U937 co-culture. Docetaxel treatment enhanced cytokine production by PC3Rx-U937 co-culture, while reducing cytokine levels in PC3-U937. In patients, changes in the levels of seven circulating cytokines (macrophage inhibitory cytokine 1 (MIC1), interleukin (IL)-1ra, IL-1β, IL-4, IL-6, IL-12 and IFNγ) after cycle 1 of docetaxel were associated with progressive disease (all P<0.05). The combination of changes in MIC1, IL-4 and IL-6 most strongly predicted PSA response (P=0.002).

Conclusions:

In vitro studies suggest docetaxel resistance is mediated, at least in part, by cytokines induced by the interaction between the docetaxel-resistant tumour cells and macrophages. Early changes in circulating cytokine levels were associated with docetaxel resistance in CRPC patients. When considered together, these data suggest a significant role for the inflammatory response and macrophages in the development of docetaxel resistance in CRPC.

Methylated Glutathione S-transferase 1 (mGSTP1) is a potential plasma free DNA epigenetic marker of prognosis and response to chemotherapy in castrate-resistant prostate cancer

Background:

Glutathione S-transferase 1 (GSTP1) inactivation is associated with CpG island promoter hypermethylation in the majority of prostate cancers (PCs). This study assessed whether the level of circulating methylated GSTP1 (mGSTP1) in plasma DNA is associated with chemotherapy response and overall survival (OS).

Methods:

Plasma samples were collected prospectively from a Phase I exploratory cohort of 75 men with castrate-resistant PC (CRPC) and a Phase II independent validation cohort (n=51). mGSTP1 levels in free DNA were measured using a sensitive methylation-specific PCR assay.

Results:

The Phase I cohort identified that detectable baseline mGSTP1 DNA was associated with poorer OS (HR, 4.2 95% CI 2.1–8.2; P<0.0001). A decrease in mGSTP1 DNA levels after cycle 1 was associated with a PSA response (P=0.008). In the Phase II cohort, baseline mGSTP1 DNA was a stronger predictor of OS than PSA change after 3 months (P=0.02). Undetectable plasma mGSTP1 after one cycle of chemotherapy was associated with PSA response (P=0.007).

Conclusions:

We identified plasma mGSTP1 DNA as a potential prognostic marker in men with CRPC as well as a potential surrogate therapeutic efficacy marker for chemotherapy and corroborated these findings in an independent Phase II cohort. Prospective Phase III assessment of mGSTP1 levels in plasma DNA is now warranted.

Circulating microRNAs are associated with docetaxel chemotherapy outcome in castration-resistant prostate cancer

Background:

Docetaxel is the first-line chemotherapy for castration-resistant prostate cancer (CRPC). However, response rates are ∼50% and determined quite late in the treatment schedule, thus non-responders are subjected to unnecessary toxicity. The potential of circulating microRNAs as early biomarkers of docetaxel response in CRPC patients was investigated in this study.

Methods:

Global microRNA profiling was performed on docetaxel-resistant and sensitive cell lines to identify candidate circulating microRNA biomarkers. Custom Taqman Array MicroRNA cards were used to measure the levels of 46 candidate microRNAs in plasma/serum samples, collected before and after docetaxel treatment, from 97 CRPC patients.

Results:

Fourteen microRNAs were associated with serum prostate-specific antigen (PSA) response or overall survival, according to Mann–Whitney U or log-rank tests. Non-responders to docetaxel and patients with shorter survival generally had high pre-docetaxel levels of miR-200 family members or decreased/unchanged post-docetaxel levels of miR-17 family members. Multivariate Cox regression with bootstrapping validation showed that pre-docetaxel miR-200b levels, post-docetaxel change in miR-20a levels, pre-docetaxel haemoglobin levels and visceral metastasis were independent predictors of overall survival when modelled together.

Conclusions:

Our study suggests that circulating microRNAs are potential early predictors of docetaxel chemotherapy outcome, and warrant further investigation in clinical trials.

Pathways of chemotherapy resistance in castration-resistant prostate cancer

Chemotherapy remains the major treatment option for castration-resistant prostate cancer (CRPC) and limited cytotoxic options are available. Inherent chemotherapy resistance occurs in half of all patients and inevitably develops even in those who initially respond. Docetaxel has been the mainstay of therapy for 6 years, providing a small survival benefit at the cost of significant toxicity. Cabazitaxel is a promising second-line agent; however, it is no less toxic, whereas mitoxantrone provides only symptomatic benefit. Multiple cellular pathways involving apoptosis, inflammation, angiogenesis, signalling intermediaries, drug efflux pumps and tubulin are implicated in the development of chemoresistance. A thorough understanding of these pathways is needed to identify biomarkers that predict chemotherapy resistance with the aim to avoid unwarranted toxicities in patients who will not benefit from treatment. Until recently, the search for predictive biomarkers has been disappointing; however, the recent discovery of macrophage inhibitory cytokine 1 as a marker of chemoresistance may herald a new era of biomarker discovery in CRPC. Understanding the interface between this complex array of chemoresistance pathways rather than their study in isolation will be required to effectively predict response and target the late stages of advanced disease. The pre-clinical evidence for these resistance pathways and their progress through clinical trials as therapeutic targets is reviewed in this study.