Length of positive surgical margins after radical prostatectomy: Does size matter? - A systematic review and meta-analysis

OBJECTIVES

The prognostic capacity of positive surgical margins (PSM) for biochemical recurrence (BCR) is unclear, with inconsistent findings across published studies. We aimed to systematically review and perform a meta-analysis exploring the impact of Positive surgical margin length on biochemical recurrence in men after radical prostatectomy.

METHODS

A search was conducted using the MEDLINE, Scopus, Embase and Cochrane databases according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines. The quality of the studies was assessed using the Newcastle-Ottawa scale, and the protocol was registered in advance (PROSPERO: CRD42020195908). This meta-analysis included 16 studies with BCR as the primary outcome measure.

RESULTS

Studies used various dichotomised thresholds for PSM length. A subgroup meta-analysis was performed using the reported multivariable hazard ratio (Continuous, 3, and 1 mm PSM length). PSM length (continuous) was independently associated with an increased risk of BCR (7 studies, HR 1.04 (CI 1.02-1.05), I2 = 8% p < 0.05). PSM length greater than 3 mm conferred a higher risk of BCR compared to less than 3 mm (4 studies, HR 1.99 (1.54-2.58) I2 = 0%, p < 0.05). There was also an increased risk of BCR associated with PSM length of less than 1 mm compared to negative surgical margins (3 studies, HR 1.46 (1.05-2.04), I2 = 0%, P = 0.02).

CONCLUSION

PSM length is independently prognostic for BCR after radical prostatectomy. Further long-term studies are needed to estimate the impact on systemic progression.

Targeting lipid metabolism in metastatic prostate cancer

Despite key advances in the treatment of prostate cancer (PCa), a proportion of men have de novo resistance, and all will develop resistance to current therapeutics over time. Aberrant lipid metabolism has long been associated with prostate carcinogenesis and progression, but more recently there has been an explosion of preclinical and clinical data which is informing new clinical trials. This review explores the epidemiological links between obesity and metabolic syndrome and PCa, the evidence for altered circulating lipids in PCa and their potential role as biomarkers, as well as novel therapeutic strategies for targeting lipids in men with PCa, including therapies widely used in cardiovascular disease such as statins, metformin and lifestyle modification, as well as novel targeted agents such as sphingosine kinase inhibitors, DES1 inhibitors and agents targeting FASN and beta oxidation.

ODP571 Blockade of ErbB-2 Nuclear Function Induces the Interferon Signaling Pathway in Breast Cancer Models Resistant to Trastuzumab

ErbB-2, a member of ErbB family of receptor tyrosine kinases, is a key oncogenic driver in breast cancer. Despite clinical efficiency of ErbB-2-targeted therapies (trastuzumab, TZ), resistance to drugs is a major issue in the clinic. While ErbB-2 is mainly a plasma membrane-bound receptor, it also migrates to the nucleus (NErbB-2) where it can act as a transcription factor or coactivator. We previously reported that NErbB-2 is a major proliferation driver in TZ-resistant breast cancer. To investigate the NErbB-2 dependent transcriptome, RNAseq was performed using a TZ-resistant breast cancer model (JIMT-1 cells) with high constitutive levels of NErbB-2. JIMT-1 cells were transfected with an ErbB-2 nuclear localization domain mutant (hErbB-2ΔNLS), which also acts as a dominant-negative inhibitor of endogenous NErbB-2 migration. Exclusion of ErbB-2 from the nucleus resulted in up-regulation of 280 genes and down-regulation of 33 genes. Functional analysis revealed that NErbB-2 blockade enriched the expression of genes involved in type-I interferon (IFN) signaling pathway. IFNB1 and its downstream effectors OAS2 and TRIM22 were among the top up-regulated genes. In an independent breast cancer model (i. e., HCC-1569 cells), exclusion of NErbB-2 from the nucleus also induced expression of these genes. Blockade of NErbB-2 localization by injection of the hErbB-2ΔNLS mutant into JIMT-1 tumor xenografts significantly inhibited in vivo tumor growth and induced mRNA expression of IFNB1, OAS2 and TRIM22. Interestingly, blockade of NErbB-2 localization by treatment with Retro-2, an inhibitor of the retrograde transport, showed similar effects consistent with modulation of the IFN signaling pathway by NErbB-2. Bioinformatic analyses showed that both the promoter and the coding region of the IFNB1 gene contain ErbB-2 associated sequences (HAS sites). ChIP-PCR analyses revealed ErbB-2 recruitment to the HAS sites of the IFNB1 promoter and coding regions in normal growth conditions. Transfection of JIMT-1 cells with the hErbB-2ΔNLS mutant abolished the recruitment of ErbB-2 at the IFNB1 gene and also caused an increase in histone H4 acetylation, a marker of active gene transcription. NErbB-2 immunostaining in a cohort of 32 primary invasive ErbB-2-positive breast carcinomas treated with TZ revealed that NErbB-2 expression correlated with a poor disease-free survival. While this cohort is small, the findings suggest that NErbB-2 could be used as a biomarker of poor response to TZ in the clinic. In summary, our findings indicate that NErbB-2 drives the growth of TZ-resistant breast cancer cells via transcriptional repression of the IFNB1 signaling pathway, and highlight NErbB-2 as a therapeutic target and biomarker in TZ-resistant breast cancer.

Presentation: No date and time listed

Abstract 2076: Phospholipid profiling of clinical prostate tissues reveals targetable alterations in membrane lipid composition accompanying tumorigenesis

Membranes are unique phospholipid (PL) interfaces that play a central role in cancer cell biology. However, PL composition of clinical tumors, and its dynamic regulation, remains a critical gap in the molecular profiling of this disease. Here, we used mass spectrometry-based spatial imaging and lipidomics to generate PL profiles of clinical prostate tissues upon cancer development and in patient-derived tumor explants (PDEs; n=43) cultured with the current clinical agent enzalutamide. Analysis of more than 100 PL species in tumors and matched normal tissues from 21 patients revealed a complexity of cancer-related changes in the tissue PL landscape. Phosphatidylcholine (PC)-based PLs were the most abundant PL class, and their relative abundance was increased in tumors compared to matched benign tissues. A greater proportion of monounsaturated fatty acid chains was characteristic of PLs in tumors, most evident in the PC and phosphatidylethanolamine (PE) PLs, as was striking elongation of fatty acid chains in the phosphatidylinositol (PI) and phosphatidylserine (PS) classes. The abundance of specific PL species and saturation groups was significantly associated with malignancy in both this and an independent cohort of unmatched patient tissues (n=47). Notably, the PL profile was significantly associated with the ERG molecular subtype and basal proliferative index (Ki67) in tumors. Furthermore, we identified individual PL species that were associated with the antiproliferative response to enzalutamide, in cultured PDEs. In light of these PL features, we proposed acetyl coA carboxylase (ACC) as a novel therapeutic target in prostate cancer. Indeed, blocking lipid biosynthesis and elongation in prostate tumors with an ACC inhibitor (ACCi, PF-05175157) significantly reduced tumor cell proliferation in PDE tissues (n=13), concomitant with increased pACC1 staining and a decreased proportion of longer chain PLs. Our findings suggest that the clinical PCa lipidome is not only a marker of malignant transformation and aggressiveness, but also therapeutic response to enzalutamide. Moreover, defining this unique biology identified further clinically actionable targets that may improve prostate cancer outcomes.

Citation Format: Lisa M. Butler, Chui Yan Mah, Jonas Dehairs, Andrew Vincent, Shadrack Mutuku, Xander Spotbeen, Rajdeep Das, Zeyad Nassar, Luke Selth, Paul Trim, Marten Snel, David Lynn, Lisa Horvath, Wayne Tilley, Margaret Centenera, Johannes Swinnen. Phospholipid profiling of clinical prostate tissues reveals targetable alterations in membrane lipid composition accompanying tumorigenesis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2076.

OR05-06 The Androgen Receptor Is a Tumour Suppressor in Estrogen Receptor Positive Breast Cancer

There is strong interest in targeting the androgen receptor (AR) in estrogen receptor (ER) positive breast cancer, but widespread confusion exits as to what therapeutic strategy - agonism or antagonism - is appropriate. Current understanding of AR predominantly stems from the field of prostate cancer, where AR is the key oncogenic driver and therapeutic target. An ensuing assumption is that AR promotes malignancy in breast cancer and should be therapeutically antagonised. However, compelling pre-clinical data to support this assumption is lacking. Since estrogen stimulates and androgen inhibits the development of normal breast tissue, we hypothesized that AR acts as a tumour suppressor in the breast and that AR agonism is the appropriate therapeutic strategy for ER-driven breast cancer. We tested this hypothesis using a large suite of cell line and patient-derived explant (PDE) and xenograft (PDX) models of breast cancer, including those that were resistant to current therapies and those harbouring genomic anomalies of ESR1 associated with treatment-resistant disease. Across the diverse models we found compelling evidence that AR agonism, but not antagonism, potently and durably inhibited tumour growth. A signature of AR activity derived from the xenograft models positively predicted disease survival in multiple large clinical cohorts of ER+ breast cancer, out-performing other breast cancer-specific prognostic signatures. We also show that an AR agonist can be combined with current ER target therapies such as Tamoxifen or a CDK4/6 inhibitor to maximize growth inhibition. Mechanistically, agonist-bound AR opposed ER signalling by repositioning ER and the co-activator p300 in the chromatin landscape, resulting in down-regulation of cell cycle genes. Introduction of an AR DNA binding mutant had no effect on ER signalling or estrogen-stimulated growth in breast cancer cells. As part of this study, we have generated consensus AR cistromes representing ER+ breast cancer cell lines and ER+ tumours that provide a new understanding of AR activity and clearly show differences to those associated with prostate cancer cell lines and tumours. In conclusion, our data provides a compelling biological rationale for AR agonism as a therapeutic strategy in multiple, clinically relevant contexts of ER-positive breast cancer. These findings should dispel widespread confusion over the role of AR in ER-driven breast cancer, an issue that currently hinders progress in leveraging modern AR-targeted therapies (e.g. selective androgen receptor modulators) that lack the undesirable side-effects of androgens for clinical benefit.

Does Gleason score of positive surgical margin after radical prostatectomy affect biochemical recurrence and oncological outcomes? Protocol for systematic review

INTRODUCTION

Positive surgical margins (PSM) in cancer patients are commonly associated with worse prognosis and a higher risk of secondary treatment. However, the relevance of this parameter in prostate cancer patients undergoing radical prostatectomy (RP) remains controversial, given the inconsistencies in its ability to predict biochemical recurrence (BCR) and oncological outcomes. Hence, further assessment of the utility of surgical margins for prostate cancer prognosis is required to predict these outcomes more accurately. Over the last decade, studies have used the Gleason score (GS) of positive margins to predict outcomes. Herein, the authors aim to conduct a systematic review investigating the role of GS of PSM after radical prostatectomy in predicting BCR and oncological outcomes.

METHODS AND ANALYSIS

We will perform a search using MEDLINE, EMBASE, SCOPUS and COCHRANE databases. The review will be reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We will screen titles and abstracts to select articles appropriate for full-text review. Studies discussing GS of PSM after RP will be included. Given the change in reporting of GS, only articles from 2005 to 2019 will be included. The quality of the studies chosen will be assessed using the Newcastle Ottawa tool for non-randomised and Cochrane risk of bias for randomised control studies. We will adopt the grading of recommendations, assessment, development and evaluation framework to comment on quality of cumulative evidence. The primary outcome measure will be time to BCR. Secondary outcome measures include secondary treatment, disease-specific survival, disease progression-free and overall mortality at follow-up period. We aim to perform a meta-analysis if the level of heterogeneity is acceptable (I² <50%).

ETHICS AND DISSEMINATION

The review does not require ethics approval as it is a review of published literature. The findings of the review will be submitted for peer-reviewed publications and presented at scientific meetings.

PROSPERO REGISTRATION NUMBER

CRD42019131800.

Abstract LB-003: Androgen-regulated proteome reveals a therapeutically relevant androgen receptor coactivator target in prostate cancer

Resistance to androgen deprivation therapy (ADT) and the development of castration resistant prostate cancer (CRPC) remains a major challenge in the treatment of advanced prostate cancer (PCa). Elucidation of resistance mechanisms leading to CRPC is essential to develop novel therapeutic interventions. Using a systems biology approach, we interrogated the androgen-regulated proteome and identified a mitotic Kinase as a novel androgen regulated kinase in PCa. The kinase was shown to be androgen-regulated in PCa and its nuclear localisation significantly increased in CRPC and was associated with biochemical relapse. Interestingly, the Kinase interacted directly with the amino terminus transactivation and carboxy terminus ligand binding domain of androgen receptor (AR), resulting in stabilisation of AR protein and its activity. The AR-driven global transcriptional program was regulated by this coactivator kinase including pathways involved in tumour invasion and metastasis. The inhibition of the kinase function decreased AR levels and activity, and slowed growth of PCa cell lines and human PCa explants. Thus the mitotic kinase is a novel AR-Stablised kinase with potential for clinical applications as both a candidate biomarker of PCa progression and a therapeutic target in advanced disease.

Citation Format: Mohammad Asim, Charlie Massie, Anne Warren, Katarina Luko, Brinder Chohan, Suraj Menon, Ajoeb Baridi, Folake Orafidiya, Wanfeng Zhao, Carlos Escriu, Hisham Mohammed, Clive D’Santos, Xiaoping Yang, Chris Taylor, Arham Qureshi, Kate Watt, Vincent Zecchini, Luke Selth, Scott Dehm, Ian Mills, Jason Carroll, Wayne Tilley, Iain McEwan, Aria Baniahmad, David Neal. Androgen-regulated proteome reveals a therapeutically relevant androgen receptor coactivator target in prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-003.

Abstract 274: The combined actions of DHT and MPA lead to altered AR signaling in normal and malignant post-menopausal breast epithelial cells

Consistent with several observational studies examining combined hormone replacement therapy (cHRT: conjugated equine estrogen in conjunction with the synthetic progestin medroxyprogesterone acetate, MPA) in postmenopausal women, a re-analysis of the placebo-controlled randomized Women's Health Initiative clinical trial demonstrated a markedly increased breast cancer risk in newly menopausal women following ≥ 5 years of cHRT (Hazard Ratio, 3.05; 95% Confidence Interval, 1.62-5.70) [1]. We have previously demonstrated that androgen receptor (AR)-mediated effects of MPA impede 5α-dihydrotestosterone (DHT)-induced AR signaling in normal and malignant breast epithelial cells (AACR abstract 2010). The current study aimed to further investigate the biological actions of DHT and/or MPA on steroid receptor expression and cancer-related intracellular signaling pathways. Immunohistochemical analysis of estrogen receptor alpha (ERα), progesterone receptor (PR) and AR expression was performed on histologically normal human post-menopausal breast tissues and measured by image analysis in tissues cultured ex vivo with vehicle (0.1% ethanol control), DHT (1nM), MPA (1nM) or the AR antagonist, bicalutamide (Bic;1uM) for 48 hr, either alone or in combination. Microarray analysis and qRT-PCR validation were performed using the ERα positive breast cancer cell line, ZR-75-1 to determine changes in gene expression in key intracellular signaling pathways. The microarray data was analyzed with Ingenuity Gene Pathway Analysis and Gene Ontology software. Statistical tests included both Wilcoxon matched pairs test and one-way ANOVA (p&lt;0.05). DHT treatment increased AR expression in cultured breast tissues compared to vehicle control (p&lt;0.05), and co-treatment with either MPA or Bic impeded this effect. No change in ERα or PR protein levels was induced by the hormone treatments. Microarray studies revealed that DHT or MPA treatment for 6 hr altered the expression of 439 and 858 genes, respectively, whereas co-treatment altered 1494 genes (p&lt;0.05). Only 114 genes were uniquely regulated by DHT, and the expression of 32% (41% induced and 27% repressed) of these genes was abrogated by MPA. Similarly, the expression of 38% (51% induced and 24% repressed) of the 690 genes uniquely regulated by co-treatment with DHT and MPA was altered compared to DHT alone (p&lt;0.05). Examples of genes that were regulated by DHT (p&lt;0.05) and this effect of DHT was antagonised by co-treatment with DHT and MPA (p&lt;0.05) are FGFR2, OLR1 and C1ORF116. Co-treatment with DHT and MPA altered the expression of genes involved in cell growth, cell cycle, cell death, cancer and intracellular signaling pathways compared to individual treatments (p&lt;0.05). Collectively, these findings suggest an AR-mediated mechanism for the action of MPA in breast cancer. 1.Prentice, R.L., et al. Am J Epidemiol, 2009 170(1): 12-23.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 274. doi:1538-7445.AM2012-274

Vps75, A New Yeast Member of the NAP Histone Chaperone Family

Homologues of nucleosome assembly protein 1 (NAP1) are found throughout eukaryotes. Here we identify and characterize a new NAP family histone chaperone from budding yeast, named Vps75. Purified Vps75 preferentially binds histone H3/H4 tetramers and is capable of assembling nucleosomes in vitro. In vivo, Vps75 is associated with the chromatin of both active and inactive genes and telomeres. Others have previously reported that Vps75 forms a complex with Rtt109, required for acetylation of histone H3 lysine 56 (H3 Lys-56). Cells lacking RTT109 are sensitive to hydroxyurea, pointing to a role in replication. We show that VPS75 is not required for H3 Lys-56 acetylation and that vps75Delta cells are insensitive to hydroxyurea, suggesting that although Rtt109 and Vps75 associate and are likely to be functionally connected, they also have separate roles.