RNAs as Candidate Diagnostic and Prognostic Markers of Prostate Cancer-From Cell Line Models to Liquid Biopsies

The treatment landscape of prostate cancer has evolved rapidly over the past five years. The explosion in treatment advances has been witnessed in parallel with significant progress in the field of molecular biomarkers. The advent of next-generation sequencing has enabled the molecular profiling of the genomic and transcriptomic architecture of prostate and other cancers. Coupled with this, is a renewed interest in the role of non-coding RNA (ncRNA) in prostate cancer biology. ncRNA consists of several different classes including small non-coding RNA (sncRNA), long non-coding RNA (lncRNA), and circular RNA (circRNA). These families are under active investigation, given their essential roles in cancer initiation, development and progression. This review focuses on the evidence for the role of RNAs in prostate cancer, and their use as diagnostic and prognostic markers, and targets for treatment in this disease.

Abstract A015: Molecular tumor profiling to identify mechanisms linking statin use with lower risk of lethal prostate cancer: Results from the Health Professionals Follow-up Study

Introduction: Epidemiologic data support an inverse association between statin use and risk of lethal prostate cancer, but contributing mechanisms have not been elucidated. Herein, using data from the Health Professionals Follow-up Study (HPFS), we updated our previous analysis of statins and lethal prostate cancer with a decade of additional follow-up, and incorporated immunohistochemistry (IHC)-based biomarkers and gene expression profiling to identify putative molecular mechanisms contributing to the association.

Methods: We included data from 44,076 HPFS participants who were cancer free in 1990, with follow-up through 2012. Participants reported prediagnostic statin use on biennial questionnaires. Statin use was categorized as current vs. never/past use, with current users further categorized as long-term vs. short-term users (≥6 vs. <6 years). To classify prostate cancer molecular subtypes, genetically validated IHC assays for TMPRSS2:ERG fusion and PTEN loss were conducted on tissue microarrays for 891 and 660 cases, respectively. Whole-genome mRNA profiling of tumor and adjacent normal tissue was completed for 237 and 114 cases, respectively, using Affymetrix GeneChip Human Gene 1.0 ST arrays. We used Cox proportional hazards analysis to generate hazard ratios (HR) and 95% confidence intervals (CI) for associations between statin use and risk of overall, advanced (stage T3b or higher at diagnosis, metastatic or fatal), and lethal (metastatic or fatal) prostate cancer, as well as molecular subtypes, adjusted for PSA testing behavior and potential confounders including obesity and smoking. Moreover, we explored gene expression pathways in tumor and adjacent normal prostate tissue of statin users vs. nonusers using gene set enrichment analysis (GSEA).

Results: During 22 years of follow-up, 6,144 men were diagnosed with prostate cancer; 1,051 (17%) had advanced disease and 827 (13%) developed lethal prostate cancer. Of cases with molecular subtype available, 48% were ERG-positive and 14% PTEN-null. In multivariable analysis, relative to never/past use, current statin use was inversely associated with risk of advanced (HR 0.84; 95% CI 0.68-1.04) and lethal (HR 0.78; 95% CI 0.68-1.01) prostate cancer. These associations were more pronounced in long-term users, where ≥6 years of prediagnosis statin use was significantly associated with a lower risk of advanced (HR 0.72; 95% CI 0.53-0.97) and lethal prostate cancer (HR 0.64; 95% CI 0.45-0.92), relative to nonuse. Long-term statin use was not associated with overall prostate cancer risk, whether ERG-positive (HR 0.89; 95% CI 0.59-1.35) or ERG-negative (HR 1.06; 95% CI 0.74-1.50). However, relative to nonuse, a longer duration of prediagnosis statin use was associated with reduced risk of PTEN-null cancers (HR 0.42; 95% CI 0.20-0.90), but not PTEN-intact disease (HR 1.18; 95% CI 0.95-1.46; p-heterogeneity=0.01). In GSEA, we identified T cell, B cell, and phosphatidylinositol (PI3K) signaling among the top pathways enriched in tumor-adjacent normal prostate tissue of current statin users, relative to never users. Intriguingly, no gene sets were differentially expressed by statin use in the tumor.

Discussion: Our updated findings from the HPFS are consistent with our prior findings and other epidemiologic data supporting a role for statins in lethal prostate cancer prevention. Molecular classification of tumors identified PTEN/PI3K signaling and inflammation/immune activation as two potential mechanisms contributing to this association. Elucidating molecular mechanisms mediating the association between statin use and lower risk of lethal prostate cancer will provide support for a causal effect of statins on lethal prostate cancer risk and could inform statin clinical trials with appropriate intermediate endpoints.

Citation Format: Emma H. Allott, Ericka M. Ebot, Amparo G. Gonzalez-Feliciano, Sarah C. Markt, Kathryn M. Wilson, Thomas U. Ahearn, Travis A. Gerke, Mary K. Downer, Konrad H. Stopsack, Jennifer R. Rider, Stephen J. Freedland, Elizabeth A. Platz, Meir J. Stampfer, Edward L. Giovannucci, Christopher J. Sweeney, Stephen P. Finn, Lorelei A. Mucci. Molecular tumor profiling to identify mechanisms linking statin use with lower risk of lethal prostate cancer: Results from the Health Professionals Follow-up Study [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr A015.

Abstract A057: Examining the link between obesity, inflammation, and exercise in patients with metastatic prostate cancer—An interim analysis from the ExPeCT trial

Background: Globally, prostate cancer (PrCa) is the fourth most common cancer type. Obesity and inflammation have been shown to play significant roles in PrCa disease progression. Obesity and a high body mass index (BMI) are associated with increased PrCa-specific mortality in patients with advanced disease. Furthermore, proinflammatory cytokines can aid metastatic potential and promote angiogenesis. The ExPeCT (Exercise, Prostate Cancer and Circulating Tumor Cells) trial seeks to examine the effectiveness of a structured exercise program in modulating inflammatory mediators and obesity in patients with metastatic PrCa.

Methods: ExPeCT (CTRIALIE 15-21 (ClincalTrials.gov identifier NCT02453139)) is a multicenter, randomized trial for patients with metastatic PrCa (n=67). Participants were randomized to either control or exercise arms. Participants in the exercise arm completed six months of prescribed aerobic exercise, which was monitored using percentage heart-rate reserve. Serum samples were collected for all participants at baseline (T0), three months (T3), and six months (T6), and assayed for 16 interlinked adipokines and cytokines using the Meso Scale Discovery platform. An interim statistical analysis was performed (n=26) comparing median change in serum analyte levels between control (n=13) and exercise (n=13) arms using non-parametric Wilcoxon rank-sum tests.

Results: Among 26 patients included in our interim analysis, mean age at baseline was 71 years, median BMI was 29.1 kg/m2, and median waist circumference (WC) was 107 cm, with no significant differences between arms (all p>0.3). Between T0 and T6, WC decreased by a median of 3.8 cm in the exercise group and 2.6 cm in the control group (p=0.412), with a similar trend for BMI. Interim serum cytokine analysis showed a 3-fold increase in IL-10 levels in the exercise arm at T3 when compared to the control arm (p=0.036). No significant change in IL-10 levels was recorded at T6 between arms (p=0.776). Similarly, CXCL8 (IL-8) levels were increased by 1.8-fold at T3 in the exercise arm in comparison to the control arm (p=0.017), with no significant change reported at T6 (p=0.191). While changes were evident in serum TNFα, IL-6, VEGF, IL-17a, MMP9 and CCL5 (RANTES) levels, these did not reach significance. Differences in levels of adipokines leptin and resistin were also reported. A 1.5-fold increase in resistin expression was observed in the exercise arm at T6; however, it was not significant (p=0.293). A 2-fold decrease in leptin in the control arm relative to the exercise arm at T6 was also detected (p=0.676). Analysis of adiponectin, MMP2, and CCL2 is ongoing.

Conclusion: Our interim analysis of ExPeCT trial participants demonstrated a significant increase in serum CXCL8 and IL-10 levels after three months of a supervised exercise intervention. These preliminary data suggest that a structured exercise program has the potential to modify inflammatory status in patients with metastatic PrCa.

Citation Format: Lauren Brady, Grainne Sheill, Anne-Marie Baird, Emma H. Allott, Tatjana Vlajnic, John Greene, Orla Casey, Brian Hayes, Emer Guinan, Juliette Hussey, Fidelma Cahill, Mieke Van Hemelrijck, Nicola Peat, Sarah Rudman, Moya Cunningham, Liam Grogan, Thomas Lynch, Rustom P. Manecksha, John McCaffrey, Orla Sheils, Dearbhaile M. O’Donnell, John O’Leary, Ray McDermott, Stephen P. Finn. Examining the link between obesity, inflammation, and exercise in patients with metastatic prostate cancer—An interim analysis from the ExPeCT trial [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr A057.

Abstract A059: Lifestyle and health-related quality of life in men with metastatic prostate cancer

Background: Patients with metastatic prostate cancer live with a considerable disease burden that may have a profound impact on physical activity and quality of life. This patient group may survive for many years after disease onset; however, there is little evidence on their habitual levels of physical activity. The aim of this study was to investigate physical activity levels and associated health-related quality of life in prostate cancer patients with bone metastases.

Methods: ExPeCT (Exercise, Prostate Cancer and Circulating Tumour Cells: CTRIAL-IE 15-21) (ClincalTrials.gov identifier NCT02453139) is an ongoing multicenter trial examining the effect of a 6-month structured exercise intervention for patients with metastatic prostate cancer. Participants complete questionnaires examining self-reported health-related quality of life (FACT-P), sleep (Pittsburgh Sleep Index), depression (PHQ-9), and physical activity (Harvard Health Professionals Study Questionnaire) at baseline, three, and six months. Analysis of 3- and 6-month data is ongoing.

Result: An interim analysis of the baseline outcome measures of 64 patients with bone metastases was completed (mean age 69.4 (SD 7.35) years and mean BMI 29.2 (SD 5.8) kg/m2). Median time since diagnosis was 34 months (IQR 7-54) and 55% (n=35) of participants had >1 region affected by metastatic disease. Preliminary data demonstrated that 38% (n=24) of participants did not meet the current aerobic exercise guidelines for cancer survivors. In total, 20% (n=13) of participants reported engaging in vigorous activity and 16% (n=11) reported completing resistance exercise. There was no correlation found between physical activity levels and quality of life (r=0.01), sleep (r=0.02), or depression (r=-0.15) scores. The majority of participants (61% (n=41)) had sleep scores of >7, indicative of poor sleep quality. Sleep scores correlated negatively with global quality of life (r =-0.55, p<0.05). Patients scored lowest in the “functional” and “additional prostate cancer-related concerns” domains of quality of life.

Discussion: Findings highlight the association between reduced quality of life and poor sleep quality among men with metastatic prostate cancer. In addition, data suggest a high prevalence of suboptimal physical activity levels in this population. Patients with metastatic disease may benefit from lifestyle interventions that aim to increase physical activity levels.

Citation Format: Gráinne Sheill, Lauren Brady, Emer Guinan, Juliette Hussey, David Hevey, Tatjana Vlajnic, Orla Casey, Anne-Marie Baird, Fidelma Cahill, Mieke Van Hemelrijck, Nicola Peat, Sarah Rudman, Thomas Lynch, Rustom P. Manecksha, Brian Hayes, Moya Cunningham, Liam Grogan, John McCaffrey, Dearbhaile M. O’Donnell, Ray McDermott, John O Leary, Stephen P. Finn. Lifestyle and health-related quality of life in men with metastatic prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr A059.

Intense Exercise for Survival among Men with Metastatic Castrate-Resistant Prostate Cancer (INTERVAL-GAP4): a multicentre, randomised, controlled phase III study protocol

INTRODUCTION

Preliminary evidence supports the beneficial role of physical activity on prostate cancer outcomes. This phase III randomised controlled trial (RCT) is designed to determine if supervised high-intensity aerobic and resistance exercise increases overall survival (OS) in patients with metastatic castrate-resistant prostate cancer (mCRPC).

METHODS AND ANALYSIS

Participants (n=866) must have histologically documented metastatic prostate cancer with evidence of progressive disease on androgen deprivation therapy (defined as mCRPC). Patients can be treatment-naïve for mCRPC or on first-line androgen receptor-targeted therapy for mCRPC (ie, abiraterone or enzalutamide) without evidence of progression at enrolment, and with no prior chemotherapy for mCRPC. Patients will receive psychosocial support and will be randomly assigned (1:1) to either supervised exercise (high-intensity aerobic and resistance training) or self-directed exercise (provision of guidelines), stratified by treatment status and site. Exercise prescriptions will be tailored to each participant's fitness and morbidities. The primary endpoint is OS. Secondary endpoints include time to disease progression, occurrence of a skeletal-related event or progression of pain, and degree of pain, opiate use, physical and emotional quality of life, and changes in metabolic biomarkers. An assessment of whether immune function, inflammation, dysregulation of insulin and energy metabolism, and androgen biomarkers are associated with OS will be performed, and whether they mediate the primary association between exercise and OS will also be investigated. This study will also establish a biobank for future biomarker discovery or validation.

ETHICS AND DISSEMINATION

Validation of exercise as medicine and its mechanisms of action will create evidence to change clinical practice. Accordingly, outcomes of this RCT will be published in international, peer-reviewed journals, and presented at national and international conferences. Ethics approval was first obtained at Edith Cowan University (ID: 13236 NEWTON), with a further 10 investigator sites since receiving ethics approval, prior to activation.

TRIAL REGISTRATION NUMBER

NCT02730338.

BBI608 inhibits cancer stemness and reverses cisplatin resistance in NSCLC

Non-small cell lung cancer (NSCLC) is the most common cause of cancer-related deaths worldwide. While partial or complete tumor regression can be achieved in patients, particularly with cisplatin-based strategies, these initial responses are frequently short-lived and are followed by tumor relapse and chemoresistance. Identifying the root of cisplatin resistance in NSCLC and elucidating the mechanism(s) of tumor relapse, is of critical importance in order to determine the point of therapeutic failure, which in turn, will aid the discovery of novel therapeutics, new combination strategies and a strategy to enhance the efficacy of current chemotherapeutics. It has been hypothesized that cancer stem cells (CSCs) may be the initiating factor of resistance. We have previously identified and characterized an aldehyde dehydrogenase 1 CSC subpopulation in cisplatin resistant NSCLC. BBI608 is a small molecule STAT3 inhibitor known to suppress cancer relapse, progression and metastasis. Here, we show that BBI608 can inhibit stemness gene expression, deplete CSCs and overcome cisplatin resistance in NSCLC.

Carcinogenesis in prostate cancer: The role of long non-coding RNAs

LncRNAs appear to play a considerable role in tumourigenesis through regulating key processes in cancer cells such as proliferative signalling, replicative immortality, invasion and metastasis, evasion of growth suppressors, induction of angiogenesis and resistance to apoptosis. LncRNAs have been reported to play a role in prostate cancer, particularly in regulating the androgen receptor signalling pathway. In this review article, we summarise the role of 34 lncRNAs in prostate cancer with a particular focus on their role in the androgen receptor signalling pathway and the epithelial to mesenchymal transition pathway.

Development and characterisation of a panel of phosphatidylinositide 3-kinase - mammalian target of rapamycin inhibitor resistant lung cancer cell lines

The PI3K-mTOR pathway is involved in regulating all hallmarks of cancer, and is often dysregulated in NSCLC, making it an attractive therapeutic target in this setting. Acquired resistance to PI3K-mTOR inhibition is a major hurdle to overcome in the success of PI3K-mTOR targeted agents. H460, A549, and H1975 resistant cells were generated by prolonged treatment in culture with Apitolisib (GDC-0980), a dual PI3K-mTOR inhibitor over a period of several months, from age-matched parent cells. Resistance was deemed to have developed when a log fold difference in IC50 had been achieved. Resistant cell lines also exhibited resistance to another widely investigated PI3K-mTOR dual inhibitor; Dactolisib (BEZ235). Cell lines were characterised at the level of mRNA (expression array profiling expression of >150 genes), miRNA (expression array profiling of 2100 miRNAs), protein (bottoms-up label-free mass spectrometry) and phosphoprotein (expression array profiling of 84 phospho/total proteins). Key alterations were validated by qPCR and Western blot. H1975 cells were initially most sensitive to Apitolisib (GDC-0980), but developed resistance more quickly than the other cell lines, perhaps due to increased selective pressure from the impressive initial effect. In-depth molecular profiling suggested epithelial-mesenchymal transition (EMT) may play a role in resistance to PI3K-mTOR dual inhibition in NSCLC.

Deoxycholic acid promotes development of gastroesophageal reflux disease and Barrett's oesophagus by modulating integrin-αv trafficking

The fundamental mechanisms underlying erosive oesophagitis and subsequent development of Barrett's oesophagus (BO) are poorly understood. Here, we investigated the contribution of specific components of the gastric refluxate on adhesion molecules involved in epithelial barrier maintenance. Cell line models of squamous epithelium (HET‐1A) and BO (QH) were used to examine the effects of bile acids on cell adhesion to extracellular matrix proteins (Collagen, laminin, vitronectin, fibronectin) and expression of integrin ligands (α₃, α_4, α₅, α₆ and α_ν). Experimental findings were validated in human explant oesophageal biopsies, a rat model of gastroesophageal reflux disease (GORD) and in patient tissue microarrays. The bile acid deoxycholic acid (DCA) specifically reduced adhesion of HET‐1A cells to vitronectin and reduced cell‐surface expression of integrin‐α_νvia effects on endocytic recycling processes. Increased expression of integrin‐α_v was observed in ulcerated tissue in a rat model of GORD and in oesophagitis and Barrett's intestinal metaplasia patient tissue compared to normal squamous epithelium. Increased expression of integrin‐α_ν was observed in QH BO cells compared to HET‐1A cells. QH cells were resistant to DCA‐mediated loss of adhesion and reduction in cell‐surface expression of integrin‐α_ν. We demonstrated that a specific component of the gastric refluxate, DCA, affects the epithelial barrier through modulation of integrin α_ν expression, providing a novel mechanism for bile acid‐mediated erosion of oesophageal squamous epithelium and promotion of BO. Strategies aimed at preventing bile acid‐mediated erosion should be considered in the clinical management of patients with GORD.

Stromal and epithelial transcriptional map of initiation progression and metastatic potential of human prostate cancer

While progression from normal prostatic epithelium to invasive cancer is driven by molecular alterations, tumor cells and cells in the cancer microenvironment are co-dependent and co-evolve. Few human studies to date have focused on stroma. Here, we performed gene expression profiling of laser capture microdissected normal non-neoplastic prostate epithelial tissue and compared it to non-transformed and neoplastic low-grade and high-grade prostate epithelial tissue from radical prostatectomies, each with its immediately surrounding stroma. Whereas benign epithelium in prostates with and without tumor were similar in gene expression space, stroma away from tumor was significantly different from that in prostates without cancer. A stromal gene signature reflecting bone remodeling and immune-related pathways was upregulated in high compared to low-Gleason grade cases. In validation data, the signature discriminated cases that developed metastasis from those that did not. These data suggest that the microenvironment may influence prostate cancer initiation, maintenance, and metastatic progression.Stromal cells contribute to tumor development but the mechanisms regulating this process are still unclear. Here the authors analyze gene expression profiles in the prostate and show that stromal gene signature changes ahead of the epithelial gene signature as prostate cancer initiates and progresses.

Investigating the role of the IGF axis as a predictor of biochemical recurrence in prostate cancer patients post-surgery

BACKGROUND

Between 20% and 35% of prostate cancer (PCa) patients who undergo treatment with curative intent (ie, surgery or radiation therapy) for localized disease will experience biochemical recurrence (BCR). Alterations in the insulin-like growth factor (IGF) axis and PTEN expression have been implicated in the development and progression of several human tumors including PCa. We examined the expression of the insulin receptor (INSR), IGF-1 receptor (IGF-1R), PTEN, and AKT in radical prostatectomy tissue of patients who developed BCR post-surgery.

METHODS

Tissue microarrays (TMA) of 130 patients post-radical prostatectomy (65 = BCR, 65 = non-BCR) were stained by immunohistochemistry for INSR, IGF-1R, PTEN, and AKT using optimized antibody protocols. INSR, IGF1-R, PTEN, and AKT expression between benign and cancerous tissue, and different Gleason grades was assessed. Kaplan-Meier survival curves were used to examine the relationship between proteins expression and BCR.

RESULTS

INSR (P < 0.001), IGF-1R (P < 0.001), and AKT (P < 0.05) expression was significantly increased and PTEN (P < 0.001) was significantly decreased in cancerous versus benign tissue. There was no significant difference in INSR, IGF-1R, or AKT expression in the cancerous tissue of non-BCR versus BCR patients (P = 0.149, P = 0.990, P = 0.399, respectively). There was a significant decrease in PTEN expression in the malignant tissue of BCR versus non-BCR patients (P = 0.011). Combinational analysis of the tissue proteins identified a combination of decreased PTEN and increased AKT or increased INSR was associated with worst outcome. We found that in each case, our hypothesized worst group was most likely to experience BCR and this was significant for combinations of PTEN+INSR and PTEN+AKT but not PTEN+IGF-1R (P = 0.023, P = 0.028, P = 0.078, respectively).

CONCLUSIONS

Low PTEN is associated with BCR and this association is strongly modified by high INSR and high AKT expression. Measurement of these proteins could help inform appropriate patient selection for postoperative adjuvant therapy and prevent BCR.

Targeting the cancer stem cell marker, aldehyde dehydrogenase 1, to circumvent cisplatin resistance in NSCLC

Non-small cell lung cancer (NSCLC) accounts for a large proportion of cancer deaths and is characterized by low treatment response rates and poor overall prognosis. In the absence of specific treatable mutations, cisplatin-based chemotherapy plays an important role in the treatment of this disease. Unfortunately, the development of resistance has become a major therapeutic challenge in the use of this cytotoxic drug. Elucidating the mechanisms underlying this resistance phenotype, may result in the development of novel agents that enhance sensitivity to cisplatin in lung cancer patients. In this study, targeting the cancer stem cell activity of aldehyde dehydrogenase 1 (ALDH1) was investigated as a strategy to overcome chemoresistance in NSCLC. Tumors from NSCLC patients showed an increase in their profile of pluripotent stemness genes. Cisplatin exposure induced the emergence or expansion of an ALDH1-positive subpopulation in cisplatin sensitive and resistant NSCLC cell lines, respectively, further enhancing cisplatin resistance. Using the Aldefluor assay and FACS analysis, ALDH1 subpopulations were isolated and evaluated in terms of stem cell characteristics. Only ALDH1-positive cells exhibited asymmetric division, cisplatin resistance and increased expression of stem cell factors in vitro. Xenograft studies in NOD/SCID mice demonstrated efficient tumorigenesis from low cell numbers of ALDH1-positive and ALDH1-negative subpopulations. Targeting ALDH1 with Diethylaminobenzaldehyde (DEAB) and Disulfiram, significantly re-sensitized resistant lung cancer cells to the cytotoxic effects of cisplatin. Our data demonstrate the existence of a lung CSC population and suggest a role for targeting ALDH1 as a potential therapeutic strategy in re-sensitizing NSCLC cells to the cytotoxic effects of cisplatin.

Expression of protein kinase C gamma promotes cell migration in colon cancer

Despite extensive efforts, Protein Kinase Cs (PKCs) have proven to be an intractable target in cancer therapies. Traditionally it was accepted that PKCs act as tumour promoters, however new research suggests that PKCs may play an important role in the suppression of cancer. A challenge in targeting PKCs is the limited data available in patient samples. One of the PKC isozymes, PKC gamma, is thought to be present only in the brain and has been largely neglected in the context of cancer. Analysis of gene expression levels of PKC gamma in patient matched normal and colon cancer tissue samples revealed an up-regulation of the gene in the cancer tissue of 54% of the patients examined. Mechanistically we demonstrate that a reduction in the levels of PKC gamma in the colon cancer cells inhibits cell migration and foci formation. Further to this, we observe an increase in cell adhesion and proliferation following the reduction of PKC gamma levels in the cell. Thus, PKC gamma plays a key role in colon cancer; making it an important isozyme that needs to be reconsidered in the context of cancer therapies.

Circular RNAs: Biogenesis, Function and Role in Human Diseases

Circular RNAs (circRNAs) are currently classed as non-coding RNA (ncRNA) that, unlike linear RNAs, form covalently closed continuous loops and act as gene regulators in mammals. They were originally thought to represent errors in splicing and considered to be of low abundance, however, there is now an increased appreciation of their important function in gene regulation. circRNAs are differentially generated by backsplicing of exons or from lariat introns. Unlike linear RNA, the 3' and 5' ends normally present in an RNA molecule have been joined together by covalent bonds leading to circularization. Interestingly, they have been found to be abundant, evolutionally conserved and relatively stable in the cytoplasm. These features confer numerous potential functions to circRNAs, such as acting as miRNA sponges, or binding to RNA-associated proteins to form RNA-protein complexes that regulate gene transcription. It has been proposed that circRNA regulate gene expression at the transcriptional or post-transcriptional level by interacting with miRNAs and that circRNAs may have a role in regulating miRNA function in cancer initiation and progression. circRNAs appear to be more often downregulated in tumor tissue compared to normal tissue and this may be due to (i) errors in the back-splice machinery in malignant tissues, (ii) degradation of circRNAs by deregulated miRNAs in tumor tissue, or (iii) increasing cell proliferation leading to a reduction of circRNAs. circRNAs have been identified in exosomes and more recently, chromosomal translocations in cancer have been shown to generate aberrant fusion-circRNAs associated with resistance to drug treatments. In addition, though originally thought to be non-coding, there is now increasing evidence to suggest that select circRNAs can be translated into functional proteins. Although much remains to be elucidated about circRNA biology and mechanisms of gene regulation, these ncRNAs are quickly emerging as potential disease biomarkers and therapeutic targets in cancer.

Prevalence and clinical correlation of programmed cell death 1 ligand (PD-L1) expression in patients with resected non-small cell lung cancer (NSCLC): Results from the European Thoracic Oncology Platform (ETOP) Lungscape cohort

8516

Background: Conflicting data exists on the potential prognostic impact of PD-L1 expression in NSCLC. The Lungscape project, a fully annotated large biobank of resected stage I-III NSCLC, allows detailed analysis of this issue. Methods: Prevalence of PD-L1 positivity and its association with clinicopathological characteristics and patient outcome - Relapse-free Survival (RFS), Time-to-Relapse (TTR) and Overall Survival (OS) - was explored in the ETOP Lungscape cohort. PD-L1 expression was assessed on tissue microarrays (TMAs) using the DAKO 28-8 immunohistochemistry assay. Positivity cut-off points of ≥1%, 5% and 50% for neoplastic cell membrane staining were considered. Results: PD-L1 data were available for 2182 patients, from 15 ETOP centers, with median follow-up 4.8 years; 1191 patients still alive; median age 66 years; 64% male, 32/54/11% for current/former/never smokers; 49/29/22% for stages I/II/III; 51/42/4/3% adenocarcinomas (AC)/squamous cell (SCC) /large cell and sarcomatoid (LCS)/other. Median RFS/TTR/OS were 53/99/69 months (AC: 52/84/72, SCC: 54/not reached/64; and LSC 52/103/74). PD-L1 prevalence with 1% cut-off was, overall: 43%, 95% confidence interval (95%CI): 41-46; (AC: 42%, 95%CI: 39-46; SCC: 44%, 95%CI: 40-47; and LCS: 53%, 95%CI: 42-65), while for 5% threshold, prevalence was 34%, 95%CI: 32-36. PD-L1 1% positivity was a significant predictor only for AC: HRRFS: + vs - = 0.82; 95%CI: 0.69-0.97, HRTTR: + vs - = 0.83; 95%CI: 0.68-1.01, HROS: + vs -= 0.83; 95%CI: 0.69-1.01 (adjusted p = 0.024, 0.064, 0.063 respectively). This effect is found also for the 5% cut-off, and preserved in the overall model including all histologies. Using the 50% cut-off, PD-L1 positivity was detected in 17% of patients; 95%CI: 15-18, but was no longer a significant predictor of outcome, overall and by histology type. Conclusions: PD-L1 positivity (1% and 5% cut-offs) was present in more than one third of resected NSCLC and was associated with a better prognosis for AC patients.

Impact and correlation of mutational load (ML) and specific mutations (mts) assessed by limited targeted profiling (LTP) with PD-L1 tumour expression (exp) in resected non-small cell lung carcinoma (NSCLC)

11587

Background: The advent of immunotherapy represents a paradigm shift in the treatment of NSCLC compared to conventional chemotherapy. Recent studies have shown higher mts burden assessed by exome sequencing are associated with improved objective response and clinical benefit. We performed this study to evaluate the impact of ML assessment by LTP, correlating with PD-L1 exp and clinicopathological variables in resected NSCLC. Methods: NSCLC patients(pts) who underwent curative resection between 1998 and 2006 at our institution were included. PD-L1 status was assessed using Ventana SP124 antibody on archival FFPE surgical tumour specimens cores. PD-L1 was scored positive if membranous staining was present in >1% of tumour cells aggregated across the replicate cores to address heterogeneity. In collaboration with the Lung Cancer Genomics Ireland Study a targeted panel of 49 genes were assessed by Sequenom MassArray including genes in MAPK and PI3K pathways. Clinical data was obtained from hospital electronic database. Results: Ninety-one pts were included, of which 51 (56.0%) were males, with a median age of 65 years (range: 42 – 82). 51.6%, n=47 with squamous histological subtypes, 46.2%, n=42 were ex-smoker and 49.5%, n=45 had Stage I disease. 23.1%, n=21 had PD-L1 positivity. 149 mts were identified of which, 32(21.5%) with PHLPP2, 31(20.9%) with PIK3R1 and 21(14.1%) with TP53. The presence of PI3K and TP53 mts are associated with positive PD-L1 status (see table). An inverse correlation of PD-L1 positivity with ML of (1 vs 2 vs 3: 53.8% vs 30.8% vs 15.4%) was noted. Conclusions: We did not identify higher PD-L1 exp with higher ML assessed by a LTP widely used in clincial practice. However, positive PD-L1 exp was correlated with PIK3R1 and TP53 mts , warranting further investigation as potential modulators or surrogates of positve PD-L1 expression. [Table: see text]

The novel detection of EGFR-T790M mutations in exhaled breath condensate

9032

Background: The EGFR-T790M somatic mutation is the most common mechanism of resistance to Tyrosine Kinase Inhibitors (TKI) in NSCLC. However patients with advanced disease are not always amenable to repeat biopsy for further molecular analysis. Developing non-invasive methods to detect T790M in cell-free DNA (cfDNA), in the absence of tissue is being actively investigated. Furthermore these 'liquid biopsies' may also overcome the problem of tumour genomic heterogeneity. Unfortunately the sensitivity of plasma for T790M detection has been disappointing with a significant chance of a false negative result. Exhaled breath condensate (EBC) is an easily collected sample and is known to harbour cfDNA, including lung cancer mutations. We explored the potential of EBC as a novel method of T790M detection. Methods: We recruited 26 patients who were either 1) known T790M positive pre/during Osimertinib therapy or 2) other mEGFR positive patients on 1st/2nd generation TKI. We collected matched plasma and EBC samples in the majority of cases. EBC samples were collected using the RTube device. Plasma was collected using standard EDTA tubes and extracted within 90 minutes. Using UltraSEEK chemistry, a targeted PCR for ultra-sensitive somatic mutation profiling on the MassARRAY system (Agena Bioscience), we compared the performance of EBC to plasma for the detection of T790M. Results: See Table. Conclusions: In this pilot study we describe the first ever report of the successful and consistent detection of T790M in the EBC of patients with EGFR mutated NSCLC, using a commercially available targeted assay. Our results suggest EBC is responsive to recognised dynamic molecular changes that occur on TKI treatment. We believe this makes EBC analysis an attractive avenue for future research, to optimise the detection of T790M mutations in liquid biopsies. [Table: see text]

Response to tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer (NSCLC) patients with de novo epidermal growth factor receptor (EGFR) T790M and S768I resistance mutations

e20557

Background: Patients with synchronous de novo EGFR sensitising and resistance mutations are rare. Little is known about the response of these patients to EGFR TKIs, especially in a Caucasian population. Methods: We identified NSCLC patients found to have EGFR mutations using PCR-based fragment length analysis, mass spectrometry-based genotyping (Sequenom), and Sanger sequencing using a large multi-institutional database. Baseline clinical characteristics, response rate, progression free survival (PFS) and overall survival (OS) were calculated. Results: From 2008-2015, we observed de novo synchronous EGFR sensitising and resistance mutations in 12 patients representing an overall incidence of 3.6% of EGFR mutants and 0.4% of all NSCLC patients tested. Seven patients were treated using EGFR TKI therapy with erlotinib. In all cases, T790M (n = 4,50%) or S768I (n = 4, 50%) occurred concurrently with another sensitising EGFR mutation, either L858R (n = 4, 34%) or exon 19 deletion (n = 8, 66%). Objective responses were seen in two patients (29%). Three further patients had stable disease lasting 6, 23 and 54 months respectively. The median progression-free survival was 24 months and the median overall survival was 34 months. All patients with baseline EGFR S768I mutations (n = 3) had an objective response or stable disease on erlotinib while two of four patients with T790M demonstrated de novo resistance. Conclusions: This is the largest Irish review of synchronous de novo EGFR mutations. The incidence of co-occurring EGFR mutations was 0.4% and erlotinib demonstrated activity in this cohort of patients. Ongoing trials will determine whether next-generation EGFR TKIs such as osimertinib are preferable as first-line therapy in these patients.

Long Non-Coding RNAs: Key Regulators of Epithelial-Mesenchymal Transition, Tumour Drug Resistance and Cancer Stem Cells

Epithelial mesenchymal transition (EMT), the adoption by epithelial cells of a mesenchymal-like phenotype, is a process co-opted by carcinoma cells in order to initiate invasion and metastasis. In addition, it is becoming clear that is instrumental to both the development of drug resistance by tumour cells and in the generation and maintenance of cancer stem cells. EMT is thus a pivotal process during tumour progression and poses a major barrier to the successful treatment of cancer. Non-coding RNAs (ncRNA) often utilize epigenetic programs to regulate both gene expression and chromatin structure. One type of ncRNA, called long non-coding RNAs (lncRNAs), has become increasingly recognized as being both highly dysregulated in cancer and to play a variety of different roles in tumourigenesis. Indeed, over the last few years, lncRNAs have rapidly emerged as key regulators of EMT in cancer. In this review, we discuss the lncRNAs that have been associated with the EMT process in cancer and the variety of molecular mechanisms and signalling pathways through which they regulate EMT, and finally discuss how these EMT-regulating lncRNAs impact on both anti-cancer drug resistance and the cancer stem cell phenotype.

Kdm6a and Kdm6b: Altered expression in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare aggressive cancer of the pleura primarily associated with prior exposure to asbestos. The current standard of care for patients suffering from MPM is a combination of cisplatin and pemetrexed (or alternatively cisplatin and raltitrexed). Most patients, however, die within 24 months of diagnosis. New therapies are therefore urgently required for this disease. Inflammation is thought to be a key element in the pathogenesis of MPM, and recently Kdm6 family members (Kdm6a and Kdm6b) have been identified as playing important roles in inflammatory processes. As such these genes could potentially represent novel candidate targets for intervention in MPM. Using RT-PCR we examined the expression of Kdm6aA and Kdm6b in a panel of MPM cell lines and in a cohort of snap-frozen patient samples isolated at surgery comprising benign, epithelial, biphasic and sarcomatoid histologies. Both Kdm6a and Kdm6b were found to be significantly overexpressed in MPM at the mRNA level. However, tests examining if targeting therapeutically Kdm6a/b using a specific small molecule inhibitor (GSK-J4) was potentially useful for treating MPM, revealed that anti-proliferative activity was higher at lower drug concentrations in cell lines derived from normal mesothelial cells compared to those derived from malignant cells. Treatments with GSK-J4 were found to be associated with the induction of apoptosis and increased expression of pro-inflammatory cytokines. As such our results demonstrate that whilst members of the Kdm6 family are overexpressed in MPM they may not be suitable candidates for therapy and may elicit a cytokine storm.

Pathology-Driven Comprehensive Proteomic Profiling of the Prostate Cancer Tumor Microenvironment

Prostate cancer is the second most common cancer in men worldwide. Gleason grading is an important predictor of prostate cancer outcomes and is influential in determining patient treatment options. Clinical decisions based on a Gleason score of 7 are difficult as the prognosis for individuals diagnosed with Gleason 4+3 cancer is much worse than for those diagnosed with Gleason 3+4 cancer. Laser capture microdissection (LCM) is a highly precise method to isolate specific cell populations or discrete microregions from tissues. This report undertook a detailed molecular characterization of the tumor microenvironment in prostate cancer to define the proteome in the epithelial and stromal regions from tumor foci of Gleason grades 3 and 4. Tissue regions of interest were isolated from several Gleason 3+3 and Gleason 4+4 tumors using telepathology to leverage specialized pathology expertise to support LCM. Over 2,000 proteins were identified following liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis of all regions of interest. Statistical analysis revealed significant differences in protein expression (>100 proteins) between Gleason 3 and Gleason 4 regions-in both stromal and epithelial compartments. A subset of these proteins has had prior strong association with prostate cancer, thereby providing evidence for the authenticity of the approach. Finally, validation of these proteins by immunohistochemistry has been obtained using an independent cohort of prostate cancer tumor specimens.Implications: This unbiased strategy provides a strong foundation for the development of biomarker protein panels with significant diagnostic and prognostic potential. Mol Cancer Res; 15(3); 281-93. ©2017 AACR.

The Role of Proteomics in Biomarker Development for Improved Patient Diagnosis and Clinical Decision Making in Prostate Cancer

Prostate Cancer (PCa) is the second most commonly diagnosed cancer in men worldwide. Although increased expression of prostate-specific antigen (PSA) is an effective indicator for the recurrence of PCa, its intended use as a screening marker for PCa is of considerable controversy. Recent research efforts in the field of PCa biomarkers have focused on the identification of tissue and fluid-based biomarkers that would be better able to stratify those individuals diagnosed with PCa who (i) might best receive no treatment (active surveillance of the disease); (ii) would benefit from existing treatments; or (iii) those who are likely to succumb to disease recurrence and/or have aggressive disease. The growing demand for better prostate cancer biomarkers has coincided with the development of improved discovery and evaluation technologies for multiplexed measurement of proteins in bio-fluids and tissues. This review aims to (i) provide an overview of these technologies as well as describe some of the candidate PCa protein biomarkers that have been discovered using them; (ii) address some of the general limitations in the clinical evaluation and validation of protein biomarkers; and (iii) make recommendations for strategies that could be adopted to improve the successful development of protein biomarkers to deliver improvements in personalized PCa patient decision making.