Introduction of Androgen Receptor Targeting shRNA Inhibits Tumor Growth in Patient-Derived Prostate Cancer Xenografts

Patient-derived xenograft (PDX) models have been established as important preclinical cancer models, overcoming some of the limitations associated with the use of cancer cell lines. The utility of prostate cancer PDX models has been limited by an inability to genetically manipulate them in vivo and difficulties sustaining PDX-derived cancer cells in culture. Viable, short-term propagation of PDX models would allow in vitro transfection with traceable reporters or manipulation of gene expression relevant to different studies within the prostate cancer field. Here, we report an organoid culture system that supports the growth of prostate cancer PDX cells in vitro and permits genetic manipulation, substantially increasing the scope to use PDXs to study the pathobiology of prostate cancer and define potential therapeutic targets. We have established a short-term PDX-derived in vitro cell culture system which enables genetic manipulation of prostate cancer PDXs LuCaP35 and BM18. Genetically manipulated cells could be re-established as viable xenografts when re-implanted subcutaneously in immunocompromised mice and were able to be serially passaged. Tumor growth of the androgen-dependent LuCaP35 PDX was significantly inhibited following depletion of the androgen receptor (AR) in vivo. Taken together, this system provides a method to generate novel preclinical models to assess the impact of controlled genetic perturbations and allows for targeting specific genes of interest in the complex biological setting of solid tumors.

hSSB1 (NABP2/OBFC2B) modulates the DNA damage and androgen-induced transcriptional response in prostate cancer

BACKGROUND

Activation and regulation of androgen receptor (AR) signaling and the DNA damage response impact the prostate cancer (PCa) treatment modalities of androgen deprivation therapy (ADT) and radiotherapy. Here, we have evaluated a role for human single-strand binding protein 1 (hSSB1/NABP2) in modulation of the cellular response to androgens and ionizing radiation (IR). hSSB1 has defined roles in transcription and maintenance of genome stability, yet little is known about this protein in PCa.

METHODS

We correlated hSSB1 with measures of genomic instability across available PCa cases from The Cancer Genome Atlas (TCGA). Microarray and subsequent pathway and transcription factor enrichment analysis were performed on LNCaP and DU145 prostate cancer cells.

RESULTS

Our data demonstrate that hSSB1 expression in PCa correlates with measures of genomic instability including multigene signatures and genomic scars that are reflective of defects in the repair of DNA double-strand breaks via homologous recombination. In response to IR-induced DNA damage, we demonstrate that hSSB1 regulates cellular pathways that control cell cycle progression and the associated checkpoints. In keeping with a role for hSSB1 in transcription, our analysis revealed that hSSB1 negatively modulates p53 and RNA polymerase II transcription in PCa. Of relevance to PCa pathology, our findings highlight a transcriptional role for hSSB1 in regulating the androgen response. We identified that AR function is predicted to be impacted by hSSB1 depletion, whereby this protein is required to modulate AR gene activity in PCa.

CONCLUSIONS

Our findings point to a key role for hSSB1 in mediating the cellular response to androgen and DNA damage via modulation of transcription. Exploiting hSSB1 in PCa might yield benefits as a strategy to ensure a durable response to ADT and/or radiotherapy and improved patient outcomes.

Neuropilin-1 is over-expressed in claudin-low breast cancer and promotes tumor progression through acquisition of stem cell characteristics and RAS/MAPK pathway activation

Background

Triple-negative breast cancers (TNBC) have a relatively poor prognosis and responses to targeted therapies. Between 25 and 39% of TNBCs are claudin-low, a poorly differentiated subtype enriched for mesenchymal, stem cell and mitogen-activated signaling pathways. We investigated the role of the cell-surface co-receptor NRP1 in the biology of claudin-low TNBC.

Methods

The clinical prognostic value of NRP1 was determined by Kaplan–Meier analysis. GSVA analysis of METABRIC and Oslo2 transcriptomics datasets was used to correlate NRP1 expression with claudin-low gene signature scores. NRP1 siRNA knockdown was performed in MDA-MB-231, BT-549, SUM159 and Hs578T claudin-low cells and proliferation and viability measured by live cell imaging and DNA quantification. In SUM159 orthotopic xenograft models using NSG mice, NRP1 was suppressed by shRNA knockdown or systemic treatment with the NRP1-targeted monoclonal antibody Vesencumab. NRP1-mediated signaling pathways were interrogated by protein array and Western blotting.

Results

High NRP1 expression was associated with shorter relapse- and metastasis-free survival specifically in ER-negative BrCa cohorts. NRP1 was over-expressed specifically in claudin-low clinical samples and cell lines, and NRP1 knockdown reduced proliferation of claudin-low cells and prolonged survival in a claudin-low orthotopic xenograft model. NRP1 inhibition suppressed expression of the mesenchymal and stem cell markers ZEB1 and ITGA6, respectively, compromised spheroid-initiating capacity and exerted potent anti-tumor effects on claudin-low orthotopic xenografts (12.8-fold reduction in endpoint tumor volume). NRP1 was required to maintain maximal RAS/MAPK signaling via EGFR and PDGFR, a hallmark of claudin-low tumors.

Conclusions

These data implicate NRP1 in the aggressive phenotype of claudin-low breast cancer and offer a novel targeted therapeutic approach to this poor prognosis subtype.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-022-01501-7.

In vitro engineering of a bone metastases model allows for study of the effects of antiandrogen therapies in advanced prostate cancer

While androgen-targeted therapies are routinely used in advanced prostate cancer (PCa), their effect is poorly understood in treating bone metastatic lesions and ultimately results in the development of metastatic castrate resistant prostate cancer (mCRPC). Here, we used an all-human microtissue-engineered model of mineralized metastatic tissue combining human osteoprogenitor cells, 3D printing and prostate cancer cells, to assess the effects of the antiandrogens, bicalutamide, and enzalutamide in this microenvironment. We demonstrate that cancer/bone stroma interactions and antiandrogens drive cancer progression in a mineralized microenvironment. Probing the bone microenvironment with enzalutamide led to stronger cancer cell adaptive responses and osteomimicry than bicalutamide. Enzalutamide presented with better treatment response, in line with enzalutamide delaying time to bone-related events and enzalutamide extending survival in mCRPC. The all-human microtissue-engineered model of mineralized metastatic tissue presented here represents a substantial advance to dissect the role of the bone tumor microenvironment and responses to therapies for mCPRC.

Leptin antagonism inhibits prostate cancer xenograft growth and progression

Hyperleptinaemia is a well-established therapeutic side effect of drugs inhibiting the androgen axis in prostate cancer (PCa), including main stay androgen deprivation therapy (ADT) and androgen targeted therapies (ATT). Given significant crossover between the adipokine hormone signalling of leptin and multiple cancer-promoting hallmark pathways, including growth, proliferation, migration, angiogenesis, metabolism and inflammation, targeting the leptin axis is therapeutically appealing, especially in advanced PCa where current therapies fail to be curative. In this study, we uncover leptin as a novel universal target in PCa and are the first to highlight increased intratumoural leptin and leptin receptor (LEPR) expression in PCa cells and patients' tumours exposed to androgen deprivation, as is observed in patients' tumours of metastatic and castrate resistant (CRPC) PCa. We also reveal the world-first preclinical evidence that demonstrates marked efficacy of targeted leptin-signalling blockade, using Allo-aca, a potent, specific, and safe LEPR peptide antagonist. Allo-aca-suppressed tumour growth and delayed progression to CRPC in mice bearing LNCaP xenografts, with reduced tumour vascularity and altered pathways of apoptosis, transcription/translation, and energetics in tumours determined as potential mechanisms underpinning anti-tumour efficacy. We highlight LEPR blockade in combination with androgen axis inhibition represents a promising new therapeutic strategy vital in advanced PCa treatment.

Apocryphal FADS2 activity promotes fatty acid diversification in cancer

Canonical fatty acid metabolism describes specific enzyme-substrate interactions that result in products with well-defined chain lengths, degree(s), and positions of unsaturation. Deep profiling of lipids across a range of prostate cancer cell lines reveals a variety of fatty acids with unusual site(s) of unsaturation that are not described by canonical pathways. The structure and abundance of these unusual lipids correlate with changes in desaturase expression and are strong indicators of cellular phenotype. Gene silencing and stable isotope tracing demonstrate that direct Δ6 and Δ8 desaturation of 14:0 (myristic), 16:0 (palmitic), and 18:0 (stearic) acids by FADS2 generate new families of unsaturated fatty acids (including n-8, n-10, and n-12) that have rarely-if ever-been reported in human-derived cells. Isomer-resolved lipidomics reveals the selective incorporation of these unusual fatty acids into complex structural lipids and identifies their presence in cancer tissues, indicating functional roles in membrane structure and signaling.

Adiponectin receptor activation inhibits prostate cancer xenograft growth

Adiponectin is an adipokine originally identified as dysregulated in obesity, with a key role in insulin sensitisation and in maintaining systemic energy balance. However, adiponectin is progressively emerging as having aberrant signalling in multiple disease states, including prostate cancer (PCa). Circulating adiponectin is lower in patients with PCa than in non-malignant disease, and inversely correlates with cancer severity. More severe hypoadiponectinemia is observed in advanced PCa than in organ-confined disease. Given the crossover between adiponectin signalling and several cancer hallmark pathways that influence PCa growth and progression, we hypothesised that targeting dysregulated adiponectin signalling may inhibit tumour growth and progression. We, therefore, aimed to test the efficacy of correcting the hypoadiponectinemia and dysregulated adiponectin signalling observed in PCa, a world-first PCa therapeutic approach, using peptide adiponectin receptor (ADIPOR) agonist ADP355 in mice bearing subcutaneous LNCaP xenografts. We demonstrate significant evidence for PCa growth inhibition by ADP355, which slowed tumour growth and delayed progression of serum PCa biomarker, prostate-specific antigen (PSA), compared to vehicle. ADP355 conferred a significant advantage by increasing time on treatment with a delayed ethical endpoint. mRNA sequencing and protein expression analyses of tumours revealed ADP355 PCa growth inhibition may be through altered cellular energetics, cellular stress and protein synthesis, which may culminate in apoptosis, as evidenced by the increased apoptotic marker in ADP355-treated tumours. Our findings highlight the efficacy of ADP355 in targeting classical adiponectin-associated signalling pathways in vivo and provide insights into the promising future for modulating adiponectin signalling through ADIPOR agonism as a novel anti-tumour treatment modality.

Synthesis of a Unique Psammaplysin F Library and Functional Evaluation in Prostate Cancer Cells by Multiparametric Quantitative Single Cell Imaging

The spirooxepinisoxazoline alkaloid psammaplysin F (1) was selected as a scaffold for the generation of a unique screening library for both drug discovery and chemical biology research. Large-scale extraction and isolation chemistry was performed on a marine sponge (Hyattella sp.) collected from the Great Barrier Reef in order to acquire >200 mg of the desired bromotyrosine-derived alkaloidal scaffold. Parallel solution-phase semisynthesis was employed to generate a series of psammaplysin-based urea (2-9) and amide analogues (10-11) in low to moderate yields. The chemical structures of all analogues were characterized using NMR and MS data. The absolute configuration of psammaplysin F and all semisynthetic analogues was determined as 6R, 7R by comparison of ECD data with literature values. All compounds (1-11) were evaluated for their effect on cell cycle distribution and changes to cancer metabolism in LNCaP prostate cancer cells using a multiparametric quantitative single-cell imaging approach. These investigations identified that in LNCaP cells psammaplysin F and some urea analogues caused loss of mitochondrial membrane potential, fragmentation of the mitochondrial tubular network, chromosome misalignment, and cell cycle arrest in mitosis.

Therapy-induced lipid uptake and remodeling underpin ferroptosis hypersensitivity in prostate cancer

Background

Metabolic reprograming, non-mutational epigenetic changes, increased cell plasticity, and multidrug tolerance are early hallmarks of therapy resistance in cancer. In this temporary, therapy-tolerant state, cancer cells are highly sensitive to ferroptosis, a form of regulated cell death that is caused by oxidative stress through excess levels of iron-dependent peroxidation of polyunsaturated fatty acids (PUFA). However, mechanisms underpinning therapy-induced ferroptosis hypersensitivity remain to be elucidated.

Methods

We used quantitative single-cell imaging of fluorescent metabolic probes, transcriptomics, proteomics, and lipidomics to perform a longitudinal analysis of the adaptive response to androgen receptor-targeted therapies (androgen deprivation and enzalutamide) in prostate cancer (PCa).

Results

We discovered that cessation of cell proliferation and a robust reduction in bioenergetic processes were associated with multidrug tolerance and a strong accumulation of lipids. The gain in lipid biomass was fueled by enhanced lipid uptake through cargo non-selective (macropinocytosis, tunneling nanotubes) and cargo-selective mechanisms (lipid transporters), whereas de novo lipid synthesis was strongly reduced. Enzalutamide induced extensive lipid remodeling of all major phospholipid classes at the expense of storage lipids, leading to increased desaturation and acyl chain length of membrane lipids. The rise in membrane PUFA levels enhanced membrane fluidity and lipid peroxidation, causing hypersensitivity to glutathione peroxidase (GPX4) inhibition and ferroptosis. Combination treatments against AR and fatty acid desaturation, lipase activities, or growth medium supplementation with antioxidants or PUFAs altered GPX4 dependence.

Conclusions

Our work provides mechanistic insight into processes of lipid metabolism that underpin the acquisition of therapy-induced GPX4 dependence and ferroptosis hypersensitivity to standard of care therapies in PCa. It demonstrates novel strategies to suppress the therapy-tolerant state that may have potential to delay and combat resistance to androgen receptor-targeted therapies, a currently unmet clinical challenge of advanced PCa. Since enhanced GPX4 dependence is an adaptive phenotype shared by several types of cancer in response to different therapies, our work might have universal implications for our understanding of metabolic events that underpin resistance to cancer therapies.

Targeted beta therapy of prostate cancer with 177Lu-labelled Miltuximab® antibody against glypican-1 (GPC-1)

PURPOSE

Chimeric antibody Miltuximab®, a human IgG1 engineered from the parent antibody MIL-38, is in clinical development for solid tumour therapy. Miltuximab® targets glypican-1 (GPC-1), a cell surface protein involved in tumour growth, which is overexpressed in solid tumours, including prostate cancer (PCa). This study investigated the potential of ⁸⁹Zr-labelled Miltuximab® as an imaging agent, and ¹⁷⁷Lu-labelled Miltuximab® as a targeted beta therapy, in a mouse xenograft model of human prostate cancer.

METHODS

Male BALB/c nude mice were inoculated subcutaneously with GPC-1-positive DU-145 PCa cells. In imaging and biodistribution studies, mice bearing palpable tumours received (a) 2.62 MBq [⁸⁹Zr]Zr-DFO-Miltuximab® followed by PET-CT imaging, or (b) 6 MBq [¹⁷⁷Lu]Lu-DOTA-Miltuximab® by Cerenkov imaging, and ex vivo assessment of biodistribution. In an initial tumour efficacy study, mice bearing DU-145 tumours were administered intravenously with 6 MBq [¹⁷⁷Lu]Lu-DOTA-Miltuximab® or control DOTA-Miltuximab® then euthanised after 27 days. In a subsequent survival efficacy study, tumour-bearing mice were given 3 or 10 MBq of [¹⁷⁷Lu]Lu-DOTA-Miltuximab®, or control, and followed up to 120 days.

RESULTS

Antibody accumulation in DU-145 xenografts was detected by PET-CT imaging using [⁸⁹Zr]Zr-DFO-Miltuximab® and confirmed by Cerenkov luminescence imaging post injection of [¹⁷⁷Lu]Lu-DOTA-Miltuximab®. Antibody accumulation was higher (% IA/g) in tumours than other organs across multiple time points. A single injection with 6 MBq of [¹⁷⁷Lu]Lu-DOTA-Miltuximab® significantly inhibited tumour growth as compared with DOTA-Miltuximab® (control). In the survival study, mice treated with 10 MBq [¹⁷⁷Lu]Lu-DOTA-Miltuximab® had significantly prolonged survival (mean 85 days) versus control (45 days), an effect associated with increased cancer cell apoptosis. Tissue histopathology assessment showed no abnormalities associated with [¹⁷⁷Lu]Lu-DOTA-Miltuximab®, in line with other observations of tolerability, including body weight stability.

CONCLUSION

These findings demonstrate the potential utility of Miltuximab® as a PET imaging agent ([⁸⁹Zr]Zr-DFO-Miltuximab®) and a beta therapy ([¹⁷⁷Lu]Lu-DOTA-Miltuximab®) in patients with PCa or other GPC-1 expressing tumours.

The long non-coding RNA GHSROS facilitates breast cancer cell migration and orthotopic xenograft tumour growth

Recent evidence suggests that numerous long non-coding RNAs (lncRNAs) are dysregulated in cancer, and have critical roles in tumour development and progression. The present study investigated the ghrelin receptor antisense lncRNA growth hormone secretagogue receptor opposite strand (GHSROS) in breast cancer. Reverse transcription-quantitative polymerase chain reaction revealed that GHSROS expression was significantly upregulated in breast tumour tissues compared with normal breast tissue. Induced overexpression of GHSROS in the MDA-MB-231 breast cancer cell line significantly increased cell migration in vitro, without affecting cell proliferation, a finding similar to our previous study on lung cancer cell lines. Microarray analysis revealed a significant repression of a small cluster of major histocompatibility class II genes and enrichment of immune response pathways; this phenomenon may allow tumour cells to better evade the immune system. Ectopic overexpression of GHSROS in the MDA-MB-231 cell line significantly increased orthotopic xenograft growth in mice, suggesting that in vitro culture does not fully capture the function of this lncRNA. This study demonstrated that GHSROS may serve a relevant role in breast cancer. Further studies are warranted to explore the function and therapeutic potential of this lncRNA in breast cancer progression.

Discovery of thalicthuberine as a novel antimitotic agent from nature that disrupts microtubule dynamics and induces apoptosis in prostate cancer cells

We report for the first time the mechanism of action of the natural product thalicthuberine (TH) in prostate and cervical cancer cells. TH induced a strong accumulation of LNCaP cells in mitosis, severe mitotic spindle defects, and asymmetric cell divisions, ultimately leading to mitotic catastrophe accompanied by cell death through apoptosis. However, unlike microtubule-binding drugs (vinblastine and paclitaxel), TH did not directly inhibit tubulin polymerization when tested in a cell-free system, whereas it reduced cellular microtubule polymer mass in LNCaP cells. This suggests that TH indirectly targets microtubule dynamics through inhibition of a critical regulator or tubulin-associated protein. Furthermore, TH is not a major substrate for P-glycoprotein (Pgp), which is responsible for multidrug resistance in numerous cancers, providing a rationale to further study TH in cancers with Pgp-mediated treatment resistance. The identification of TH's molecular target in future studies will be of great value to the development of TH as potential treatment of multidrug-resistant tumors.

Limited short-term effects on human prostate cancer xenograft growth and epidermal growth factor receptor gene expression by the ghrelin receptor antagonist [D-Lys3]-GHRP-6

PURPOSE

The ghrelin axis regulates many physiological functions (including appetite, metabolism, and energy balance) and plays a role in disease processes. As ghrelin stimulates prostate cancer proliferation, the ghrelin receptor antagonist [D-Lys³]-GHRP-6 is a potential treatment for castrate-resistant prostate cancer and for preventing the metabolic consequences of androgen-targeted therapies. We therefore explored the effect of [D-Lys³]-GHRP-6 on PC3 prostate cancer xenograft growth.

METHODS

NOD/SCID mice with PC3 prostate cancer xenografts were administered 20 nmoles/mouse [D-Lys³]-GHRP-6 daily by intraperitoneal injection for 14 days and tumour volume and weight were measured. RNA sequencing of tumours was conducted to investigate expression changes following [D-Lys³]-GHRP-6 treatment. A second experiment, extending treatment time to 18 days and including a higher dose of [D-Lys³]-GHRP-6 (200 nmoles/mouse/day), was undertaken to ensure repeatability.

RESULTS

We demonstrate here that daily intraperitoneal injection of 20 nmoles/mouse [D-Lys³]-GHRP-6 reduces PC3 prostate cancer xenograft tumour volume and weight in NOD/SCID mice at two weeks post treatment initiation. RNA-sequencing revealed reduced expression of epidermal growth factor receptor (EGFR) in these tumours. Further experiments demonstrated that the effects of [D-Lys³]-GHRP-6 are transitory and lost after 18 days of treatment.

CONCLUSIONS

We show that [D-Lys³]-GHRP-6 has transitory effects on prostate xenograft tumours in mice, which rapidly develop an apparent resistance to the antagonist. Although further studies on [D-Lys³]-GHRP-6 are warranted, we suggest that daily treatment with the antagonist is not a suitable treatment for advanced prostate cancer.

Engineering osteoblastic metastases to delineate the adaptive response of androgen-deprived prostate cancer in the bone metastatic microenvironment

While stromal interactions are essential in cancer adaptation to hormonal therapies, the effects of bone stroma and androgen deprivation on cancer progression in bone are poorly understood. Here, we tissue-engineered and validated an in vitro microtissue model of osteoblastic bone metastases, and used it to study the effects of androgen deprivation in this microenvironment. The model was established by culturing primary human osteoprogenitor cells on melt electrowritten polymer scaffolds, leading to a mineralized osteoblast-derived microtissue containing, in a 3D setting, viable osteoblastic cells, osteocytic cells, and appropriate expression of osteoblast/osteocyte-derived mRNA and proteins, and mineral content. Direct co-culture of androgen receptor-dependent/independent cell lines (LNCaP, C4-2B, and PC3) led cancer cells to display functional and molecular features as observed in vivo. Co-cultured cancer cells showed increased affinity to the microtissues, as a function of their bone metastatic potential. Co-cultures led to alkaline phosphatase and collagen-I upregulation and sclerostin downregulation, consistent with the clinical marker profile of osteoblastic bone metastases. LNCaP showed a significant adaptive response under androgen deprivation in the microtissues, with the notable appearance of neuroendocrine transdifferentiation features and increased expression of related markers (dopa decarboxylase, enolase 2). Androgen deprivation affected the biology of the metastatic microenvironment with stronger upregulation of androgen receptor, alkaline phosphatase, and dopa decarboxylase, as seen in the transition towards resistance. The unique microtissues engineered here represent a substantial asset to determine the involvement of the human bone microenvironment in prostate cancer progression and response to a therapeutic context in this microenvironment.

Lipid Uptake Is an Androgen-Enhanced Lipid Supply Pathway Associated with Prostate Cancer Disease Progression and Bone Metastasis

De novo lipogenesis is a well-described androgen receptor (AR)-regulated metabolic pathway that supports prostate cancer tumor growth by providing fuel, membrane material, and steroid hormone precursor. In contrast, our current understanding of lipid supply from uptake of exogenous lipids and its regulation by AR is limited, and exogenous lipids may play a much more significant role in prostate cancer and disease progression than previously thought. By applying advanced automated quantitative fluorescence microscopy, we provide the most comprehensive functional analysis of lipid uptake in cancer cells to date and demonstrate that treatment of AR-positive prostate cancer cell lines with androgens results in significantly increased cellular uptake of fatty acids, cholesterol, and low-density lipoprotein particles. Consistent with a direct, regulatory role of AR in this process, androgen-enhanced lipid uptake can be blocked by the AR-antagonist enzalutamide, but is independent of proliferation and cell-cycle progression. This work for the first time comprehensively delineates the lipid transporter landscape in prostate cancer cell lines and patient samples by analysis of transcriptomics and proteomics data, including the plasma membrane proteome. We show that androgen exposure or deprivation regulates the expression of multiple lipid transporters in prostate cancer cell lines and tumor xenografts and that mRNA and protein expression of lipid transporters is enhanced in bone metastatic disease when compared with primary, localized prostate cancer. Our findings provide a strong rationale to investigate lipid uptake as a therapeutic cotarget in the fight against advanced prostate cancer in combination with inhibitors of lipogenesis to delay disease progression and metastasis. IMPLICATIONS: Prostate cancer exhibits metabolic plasticity in acquiring lipids from uptake and lipogenesis at different disease stages, indicating potential therapeutic benefit by cotargeting lipid supply.

Insulin Enhances Migration and Invasion in Prostate Cancer Cells by Up-Regulation of FOXC2

Androgen deprivation therapy (ADT) is the standard treatment for advanced prostate cancer (PCa), yet many patients relapse with lethal metastatic disease. With this loss of androgens, increased cell plasticity has been observed as an adaptive response to ADT. This includes gain of invasive and migratory capabilities, which may contribute to PCa metastasis. Hyperinsulinemia, which develops as a side-effect of ADT, has been associated with increased tumor aggressiveness and faster treatment failure. We investigated the direct effects of insulin in PCa cells that may contribute to this progression. We measured cell migration and invasion induced by insulin using wound healing and transwell assays in a range of PCa cell lines of variable androgen dependency (LNCaP, 22RV1, DuCaP, and DU145 cell lines). To determine the molecular events driving insulin-induced invasion we used transcriptomics, quantitative real time-PCR, and immunoblotting in three PCa cell lines. Insulin increased invasiveness of PCa cells, upregulating Forkhead Box Protein C2 (FOXC2), and activating key PCa cell plasticity mechanisms including gene changes consistent with epithelial-to-mesenchymal transition (EMT) and a neuroendocrine phenotype. Additionally, analysis of publicly available clinical PCa tumor data showed metastatic prostate tumors demonstrate a positive correlation between insulin receptor expression and the EMT transcription factor FOXC2. The insulin receptor is not suitable to target clinically however, our data shows that actions of insulin in PCa cells may be suppressed by inhibiting downstream signaling molecules, PI3K and ERK1/2. This study identifies for the first time, a mechanism for insulin-driven cancer cell motility and supports the concept that targeting insulin signaling at the level of the PCa tumor may extend the therapeutic efficacy of ADT.

Transcriptomic analysis of mRNA expression and alternative splicing during mouse sex determination

Mammalian sex determination hinges on sexually dimorphic transcriptional programs in developing fetal gonads. A comprehensive view of these programs is crucial for understanding the normal development of fetal testes and ovaries and the etiology of human disorders of sex development (DSDs), many of which remain unexplained. Using strand-specific RNA-sequencing, we characterized the mouse fetal gonadal transcriptome from 10.5 to 13.5 days post coitum, a key time window in sex determination and gonad development. Our dataset benefits from a greater sensitivity, accuracy and dynamic range compared to microarray studies, allows global dynamics and sex-specificity of gene expression to be assessed, and provides a window to non-transcriptional events such as alternative splicing. Spliceomic analysis uncovered female-specific regulation of Lef1 splicing, which may contribute to the enhanced WNT signaling activity in XX gonads. We provide a user-friendly visualization tool for the complete transcriptomic and spliceomic dataset as a resource for the field.

No effect of unacylated ghrelin administration on subcutaneous PC3 xenograft growth or metabolic parameters in a Rag1-/- mouse model of metabolic dysfunction

Ghrelin is a peptide hormone which, when acylated, regulates appetite, energy balance and a range of other biological processes. Ghrelin predominately circulates in its unacylated form (unacylated ghrelin; UAG). UAG has a number of functions independent of acylated ghrelin, including modulation of metabolic parameters and cancer progression. UAG has also been postulated to antagonise some of the metabolic effects of acyl-ghrelin, including its effects on glucose and insulin regulation. In this study, Rag1-/- mice with high-fat diet-induced obesity and hyperinsulinaemia were subcutaneously implanted with PC3 prostate cancer xenografts to investigate the effect of UAG treatment on metabolic parameters and xenograft growth. Daily intraperitoneal injection of 100 μg/kg UAG had no effect on xenograft tumour growth in mice fed normal rodent chow or 23% high-fat diet. UAG significantly improved glucose tolerance in host Rag1-/- mice on a high-fat diet, but did not significantly improve other metabolic parameters. We propose that UAG is not likely to be an effective treatment for prostate cancer, with or without associated metabolic syndrome.

Mining human cancer datasets for kallikrein expression in cancer: the 'KLK-CANMAP' Shiny web tool

The dysregulation of the serine-protease family kallikreins (KLKs), comprising 15 genes, has been reportedly associated with cancer. Their expression in several tissues and physiological fluids makes them potential candidates as biomarkers and therapeutic targets. There are several databases available to mine gene expression in cancer, which often include clinical and pathological data. However, these platforms present some limitations when comparing a specific set of genes and can generate considerable unwanted data. Here, several datasets that showed significant differential expression (p<0.01) in cancer vs. normal (n=118), metastasis vs. primary (n=15) and association with cancer survival (n=21) have been compiled in a user-friendly format from two open and/or publicly available databases Oncomine and OncoLnc for the 15 KLKs. The data have been included in a free web application tool: the KLK-CANMAP https://cancerbioinformatics.shinyapps.io/klk-canmap/. This tool integrates, analyses and visualises data and it was developed with the R Shiny framework. Using KLK-CANMAP box-plots, heatmaps and Kaplan-Meier graphs can be generated for the KLKs of interest. We believe this new cancer KLK focused web tool will benefit the KLK community by narrowing the data visualisation to only the genes of interest.

Extracellular Vesicles in the Adaptive Process of Prostate Cancer during Inhibition of Androgen Receptor Signaling by Enzalutamide

Current treatments for advanced prostate cancer focus on inhibition of the androgen receptor (AR) by androgen deprivation therapy (ADT). However, complex interactions mediated by tumor suppressors, oncogenes, aberrations of AR expression, or de novo androgen production have been shown to induce the adaptive response of prostate cancer, leading to the development of castration resistant prostate cancer. In this study, we report the effects of AR antagonist, enzalutamide on the protein contents of extracellular vesicles (EVs). EVs mediate cell-to-cell communication and increasing evidence shows the role of EVs in promoting cancer survival and metastasis. We found that treatment with enzalutamide alters the secretion of EVs, one of which is a plasma membrane calcium pump, ATP2B1/PMCA ATPase, as an AR-regulated EV protein. We highlight the networks of interactions between AR, Ca²⁺ , and ATP2B1, where the extracellular proteins thrombospondin-1, gelsolin, and integrinß1 were previously reported as regulators for cancer progression and metastasis, indicating the potential role of EV-derived proteins in mediating calcium homoeostasis under AR inhibition by enzalutamide. Our data further highlight the cross-talk between AR signaling and EV pathways in mediating resistance toward ADT.

Abstract 2452: Dysregulated expression of the human long noncoding RNA GHSROS may influence prostate cancer progression and resistance to docetaxel

Long noncoding RNAs (lncRNAs) play key regulatory roles in cancer progression and are novel therapeutic targets. We recently discovered the lncRNA gene, GHSROS (GHSR opposite strand), on the antisense DNA strand of the ghrelin receptor gene (GHSR). Here, we studied the expression and function of GHSROS in prostate cancer. Interrogation of microarray and RNA-seq data sets revealed that (similar to other lncRNA oncogenes) GHSROS is actively transcribed, although expressed at very low levels in cancer cell lines and tissues. By quantitative RT-PCR we demonstrate that GHSROS is highly expressed in a subset of high-grade prostate cancers (~11.4%). Moreover, the lncRNA is upregulated in high Gleason-score prostate tumors in two clinical data sets. Forced GHSROS overexpression significantly increased in vitro cell proliferation and migration of PC3, DU145, and LNCaP prostate cancer cell lines (P ≤ 0.05, Student's t-test). Increased cell proliferation observed in GHSROS-overexpressing prostate cancer cell lines was recapitulated in PC3, DU145, and LNCaP prostate cancer xenografts in NOD/SCID mice. Cell survival was significantly increased in GHSROS-overexpressing LNCaP cells treated with the cytotoxic drug docetaxel (P ≤ 0.05, Student's t-test). Docetaxel treatment also increased GHSROS expression in native LNCaP and PC3 cells in a dose-dependent manner (P ≤ 0.05, Student's t-test). These data suggest that GHSROS mediates tumor survival and resistance to docetaxel. To identify fundamental drivers of the observed tumorigenic phenotype of GHSROS-overexpressing cell lines, high-throughput RNA-seq data from in vitro cultured PC3 cells and LNCaP xenografts were examined. A quarter of the genes differentially expressed by GHSROS-overexpressing PC3 cells were also differentially expressed by GHSROS-overexpressing LNCaP xenografts. These 101 genes include several transcription factors with established roles in prostate cancer (including the androgen receptor) and genes associated with metastasis and poor prognosis. Finally, we developed two distinct antisense oligonucleotides (ASOs) targeting GHSROS, achieving &gt;60% knockdown, and their function was assessed in vitro. ASO inhibition of GHSROS expression reciprocally regulated cell growth and migration and the expression of a range of genes. These ASOs are currently being assessed in preclinical animal models. Our findings suggest that the long noncoding RNA GHSROS reprograms prostate cancer cells toward a more aggressive phenotype and that the lncRNA represents a promising therapeutic target.

Citation Format: Patrick B. Thomas, Penny L. Jeffery, Gahete D. Manuel, Eliza J. Whiteside, Michelle Maugham, Carina Walpole, Jennifer H. Gunter, Elizabeth D. Williams, Colleen C. Nelson, Adrian C. Herington, Raul M. Luque, Rakesh N. Veedu, Lisa K. Chopin, Inge Seim. Dysregulated expression of the human long noncoding RNA GHSROS may influence prostate cancer progression and resistance to docetaxel [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2452.

Identification of Gibberellic Acid Derivatives That Deregulate Cholesterol Metabolism in Prostate Cancer Cells

The naturally occurring pentacyclic diterpenoid gibberellic acid (1) was used in the generation of a drug-like amide library using parallel-solution-phase synthesis. Prior to the synthesis, a virtual library was generated and prioritized based on drug-like physicochemical parameters such as log P, hydrogen bond donor/acceptor counts, and molecular weight. The structures of the synthesized analogues (2-13) were elucidated following analysis of the NMR, MS, UV, and IR data. Compound 12 afforded crystalline material, and its structure was confirmed by X-ray crystallographic analysis. All compounds were evaluated in vitro for cytotoxicity and deregulation of lipid metabolism in LNCaP prostate cancer cells. While no cytotoxic activity was identified at the concentrations tested, synthesized analogues 3, 5, 7, 10, and 11 substantially reduced cellular uptake of free cholesterol in prostate cancer cells, suggesting a novel role of gibberellic acid derivatives in deregulating cholesterol metabolism.

Short term ex-vivo expansion of circulating head and neck tumour cells

Minimally invasive techniques are required for the identification of head and neck cancer (HNC) patients who are at an increased risk of metastasis, or are not responding to therapy. An approach utilised in other solid cancers is the identification and enumeration of circulating tumour cells (CTCs) in the peripheral blood of patients. Low numbers of CTCs has been a limiting factor in the HNC field to date. Here we present a methodology to expand HNC patient derived CTCs ex-vivo. As a proof of principle study, 25 advanced stage HNC patient bloods were enriched for circulating tumour cells through negative selection and cultured in 2D and 3D culture environments under hypoxic conditions (2% O₂, 5% CO₂). CTCs were detected in 14/25 (56%) of patients (ranging from 1–15 CTCs/5 mL blood). Short term CTC cultures were successfully generated in 7/25 advanced stage HNC patients (5/7 of these cultures were from HPV+ patients). Blood samples from which CTC culture was successful had higher CTC counts (p = 0.0002), and were predominantly from HPV+ patients (p = 0.007). This is, to our knowledge, the first pilot study to culture HNC CTCs ex-vivo. Further studies are warranted to determine the use of short term expansion in HNC and the role of HPV in promoting culture success.

Extracellular vesicles for personalized therapy decision support in advanced metastatic cancers and its potential impact for prostate cancer

The use of circulating tumor cells (CTCs) and circulating extracellular vesicles (EVs), such as exosomes, as liquid biopsy-derived biomarkers for cancers have been investigated. CTC enumeration using the CellSearch based platform provides an accurate insight on overall survival where higher CTC counts indicate poor prognosis for patients with advanced metastatic cancer. EVs provide information based on their lipid, protein, and nucleic acid content and can be isolated from biofluids and analyzed from a relatively small volume, providing a routine and non-invasive modality to monitor disease progression. Our pilot experiment by assessing the level of two subpopulations of small EVs, the CD9 positive and CD63 positive EVs, showed that the CD9 positive EV level is higher in plasma from patients with advanced metastatic prostate cancer with detectable CTCs. These data show the potential utility of a particular EV subpopulation to serve as biomarkers for advanced metastatic prostate cancer. EVs can potentially be utilized as biomarkers to provide accurate genotypic and phenotypic information for advanced prostate cancer, where new strategies to design a more personalized therapy is currently the focus of considerable investigation.

Folate-targeted amphiphilic cyclodextrin nanoparticles incorporating a fusogenic peptide deliver therapeutic siRNA and inhibit the invasive capacity of 3D prostate cancer tumours

The main barrier to the development of an effective RNA interference (RNAi) therapy is the lack of a suitable delivery vector. Modified cyclodextrins have emerged in recent years for the delivery of siRNA. In the present study, a folate-targeted amphiphilic cyclodextrin was formulated using DSPE-PEG₅₀₀₀-folate to target prostate cancer cells. The fusogenic peptide GALA was included in the formulation to aid in the endosomal release of siRNA. Targeted nanoparticles were less than 200nm in size with a neutral surface charge. The complexes were able to bind siRNA and protect it from serum nucleases. Incubation with excess free folate resulted in a significant decrease in the uptake of targeted nanoparticles in LNCaP and PC3 cells, both of which have been reported to have differing pathways of folate uptake. There was a significant reduction in the therapeutic targets, ZEB1 and NRP1 at mRNA and protein level following treatment with targeted complexes. In preliminary functional assays using 3D spheroids, treatment of PC3 tumours with targeted complexes with ZEB1 and NRP1 siRNA resulted in more compact colonies relative to the untargeted controls and inhibited infiltration into the Matrigel™ layer.

Abstract 3442: The long non-coding RNA GHSROS mediates expression of genes associated with tumor growth, metastasis and adverse disease outcome

Long non-coding RNAs (lncRNAs) play key regulatory roles in cancer progression and are emerging therapeutic targets. The objective of this study was to investigate the expression and function of the lncRNA GHSROS in prostate cancer. Quantitative RT-PCR revealed that GHSROS is highly expressed in a subset of prostate cancers (Gleason score 8-10; z-score &gt;1; Mann-Whitney-Wilcoxon test P=0.0021). Forced overexpression of the lncRNA stimulated cell migration in vitro in the PC3 (1.82 ± 0.35, P=0.006; Student’s t-test), DU145 (1.94 ± 0.34, P=0.017), and LNCaP (1.27 ± 0.02, P=0.0002) prostate cancer cell lines. Cell proliferation was increased in GHSROS overexpressing PC3 (3.36 ± 1.91, P=0.029), DU145 (1.749 ± 0.59, P=0.026), and LNCaP (1.39 ± 0.26, P=0.040) prostate cancer cell lines. These results were recapitulated in NOD/SCID mice, with increased tumor growth and Ki67 immunohistochemical staining in PC3 (P=0.0040) and DU145 (P = 0.036) xenografts overexpressing the lncRNA.High-throughput transcriptome sequencing (RNA-seq) identified 400 differentially expressed genes in GHSROS overexpressing PC3 cells, with enrichment of genes associated with motility, migration and regulation of cell growth. Further interrogation of the 400 gene set using Oncomine concept mapping, and interrogation of publicly-available clinical prostate cancer data sets, revealed a 34-gene signature associated with poorer disease outcome and metastatic progression. Preliminary analysis of The Cancer Genome Atlas (TCGA) data, suggest that the signature has potential as a prognostic indicator for disease free- or overall survival in numerous cancers. Finally, locked antisense oligonucleotide (LNA-ASO) inhibition of endogenous GHSROS reciprocally regulated cell growth (Student’s t-test; RNV124: -1.14 ± 0.06, P=0.049 and RNV104L: -1.18 ± 0.05, P=0.030, migration (RNV124: -1.96 ± 0.11, P=0.004) and gene expression changes, supporting the observations from forced GHSROS overexpression experiments.In summary, we provide evidence that GHSROS is a prostate cancer associated lncRNA that promotes a gene expression signature which enhances the propensity for metastasis and adverse disease outcomes. We also demonstrate that GHSROS can be targeted using antisense oligonucleotides. Further studies on this lncRNA may provide new prognostic and therapeutic opportunities.

Citation Format: Patrick B. Thomas, Penny L. Jeffery, Eliza Whiteside, Carina Walpole, Michelle Maugham, Lidija Jovanovic, Jennifer H. Gunter, Colleen C. Nelson, Adrian C. Herington, Rakesh Veedu, Lisa K. Chopin, Inge Seim. The long non-coding RNA GHSROS mediates expression of genes associated with tumor growth, metastasis and adverse disease outcome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3442. doi:10.1158/1538-7445.AM2017-3442

Abstract 4819: Insights from engraftable immunodeficient mouse models of hyperinsulinaemia

Hyperinsulinemia, obesity and dyslipidemia are independent and collective risk factors for many cancers, however, there is a lack of suitable mouse models available to study this association.

We examined the long-term effects of a “Western style” 23% high fat diet (HFD, 46% of total calculated energy from lipids) in two immunodeficient mouse strains (NOD/SCID and Rag1 -/-) suitable for engraftment with human-derived cell lines and tissue xenografts. HFD-fed mice of both strains exhibited diet-induced impairments in glucose tolerance at 16 and 23 weeks post initiation of HFD feeding. Only Rag1 -/- mice developed higher fasting insulin levels (2.16 ± 1.01ng/ml versus 0.71 ± 0.12ng/ml, P = 0.01) and increased insulin resistance (6.70 ± 1.68 HOMA-IR, versus 2.91 ± 0.42, P = 0.01) when fed a HFD. Similarly, hepatic steatosis was more extensive, and intramyocellular lipid storage was increased in HFD-fed Rag1 -/- mice. Conversely, NOD/SCID mice exhibited relatively low levels of steatosis and no intramyocellular lipid was observed. These data suggest that Rag1 -/- mice are a more suitable pre-clinical model for examining the interactions between hyperinsulinemia, obesity and hyperlipidemia and cancer than the more commonly used NOD/SCID mouse model.

We next investigated the growth of human prostate cancer cell lines (PC3 and LNCaP) subcutaneously injected into hyperinsulinemic Rag1 -/- mice. Compared to normal chow-fed mice, tumor growth velocity was greater in HFD-fed mice with PC3 and LNCaP xenografts, and mice reached humane endpoints (cancer-associated cachexia and tumor burden) significantly earlier (P = 0.0078 and P = 0.031). Strikingly, HFD-fed mice bearing PC3 xenografts presented with significantly greater normalized wet tumor weight (485.16 ± 143.80% vs. 1562.69 ± 338.20%, P = 0.032), tumor volume (485.16 ± 143.80% vs.1562.69 ± 338.20%, P = 0.032) and number of Ki67 positive (proliferating) tumor cells (36.08 ± 2.53% vs. 66.14 ± 8.514, P = 0.032), compared to mice fed a normal chow diet.

In summary, this is the first study of the metabolic effects of a long-term “Western style” HFD in two immunodeficient mouse strains suitable for xenograft studies. We demonstrate that the Rag1 -/- mouse is an appropriate and novel model for studying the interactions between hyperinsulinaemia and cancer.

Citation Format: Michelle L. Maugham, Patrick B. Thomas, Gabrielle J. Crisp, Lisa K. Philp, Esha T. Shah, Adrian C. Herington, Chen Chen, Laura S. Gregory, Colleen C. Nelson, Inge Seim, Penny L. Jeffery, Lisa K. Chopin. Insights from engraftable immunodeficient mouse models of hyperinsulinaemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4819. doi:10.1158/1538-7445.AM2017-4819

Abstract 4909: Androgen targeted therapy induces ZEB1 expression and is associated with suppression of androgen signalling and therapy resistance

Reactivation of the embryonic developmental pathway, epithelial-to-mesenchymal transition (EMT) is associated with prostate cancer (PCa) metastasis and therapy resistance. Recent evidence has demonstrated EMT is stimulated following androgen targeted therapy (ATT). In the present study we investigated the role of EMT transcription factor ZEB1 in ATT-driven EMT, PCa metastasis and drug resistance.

Immunohistochemistry (IHC) staining of ZEB1 on tissue microarrays of primary tumors from clinical samples demonstrated ZEB1 expression correlated with increased tumor aggressiveness and Gleason score. Upon stratification of patient data (n=198), high ZEB1 protein expression correlated with a shorter time to biochemical recurrence (BCR). Furthermore, IHC staining of primary tumours from 148 treatment-naïve patients with and without metastasis demonstrated high ZEB1 levels and correlated to a reduced time to metastasis.

To delineate the role of ZEB1 as a molecular driver of late-stage PCa, microarray analysis of an in vivo LNCaP progression model demonstrated ZEB1 levels increased following castration. Significantly, high ZEB1 levels were associated with patients who had undergone neoadjuvant hormone therapy with or without docetaxel and high ZEB1 levels were associated with a shorter time to BCR and metastasis. Inhibition of the androgen/androgen receptor (AR) axis in LNCaP cells using antiandrogen treatment or shRNA targeting AR resulted in upregulation of ZEB1 in LNCaP cells suggesting enhanced levels of ZEB1 may drive the early adaptive response of PCa after hormone therapy. Interestingly, in models where ZEB1 expression was elevated this was accompanied with repression of classical androgen-regulated genes suggesting ZEB1 is able to regulate the AR transcriptional pathway.

We also investigated the role of ZEB1 in cancer invasion and chemoresistance. An inducible model of ZEB1 overexpression in LNCaP cells produced a robust EMT upon ZEB1 expression and was accompanied by an invasive phenotype in 3D cultures. ZEB1 overexpression also conferred resistance to docetaxel (IC50 of 8.17±2.45nM in ZEB1-expressing cells vs. 3.35±0.23nM in control cells) potentially as a result of a reduced apoptotic cell death response mediated by ZEB1. At suboptimal doses of docetaxel, the percentage of apoptotic cells (annexin-V+/propidium iodide-) decreased 4-fold when ZEB1 was expressed compared with control cells and was accompanied by a reduction in PARP cleavage and cleaved caspase-7 expression.

In summary, we provide evidence that ZEB1 expression is increased in response to ATTs and correlates with disease progression, metastasis and therapy resistance. We also show ZEB1 is a transcriptional regulator of AR signalling in PCa, Together this provides the rationale to target ZEB1 for the development of novel therapies for the treatment of CRPC.

Note: This abstract was not presented at the meeting.

Citation Format: Katrina G. Sweeney, Nataly Stylianou, Gregor Tevz, Atefeh Taherianfard, Katrina Pirlo, Akanksha Upadhyaya, Ellca Ratther, Melanie Lehman, Martin Gleave, Jennifer Gunter, Elizabeth D. Williams, Colleen C. Nelson, Brett Hollier. Androgen targeted therapy induces ZEB1 expression and is associated with suppression of androgen signalling and therapy resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4909. doi:10.1158/1538-7445.AM2017-4909

Abstract 818: Unravelling the role of androgen targeted therapies in epithelial plasticity during prostate cancer progression

Recent evidence suggests that the use of potent androgen receptor (AR) antagonists have contributed to the increased prevalence of prostate cancer (PCa) tumors exhibiting therapy resistance. Androgen targeted therapies (ATT) inhibit the androgen/AR axis which PCa cells rely on for growth. ATT are initially effective however most men progress to metastatic castration resistant prostate cancer (mCRPC). Mechanisms of resistance include programs of epithelial plasticity (EP) such as epithelial-to-mesenchymal transition (EMT) and neuroendocrine transdifferentiation (NEtD). EMT enables PCa cells to become more motile and invasive. PCa cells that undergo NEtD gain neuroendocrine (NE)-like traits. Patients with NE prostate cancer (NEPC) usually present with visceral metastasis, are refractory to ATT and have short response to chemotherapies. We aim to characterize models of therapy-induced NEtD (tNEPC) and to investigate the role of tumor plasticity in the progression to mCRPC.

To recapitulate ATT in vitro, androgen-dependent LNCaP cells were treated with either enzalutamide (Enz) (10μM) or shRNA targeting AR in culture medium containing fetal bovine serum (FBS) or charcoal stripped serum (CSS) with or without 10nM dihydrotestosterone (DHT). To model EMT, LNCaP cells were engineered to express doxycycline (Dox) inducible overexpression of EMT transcription factor Snail. Androgen deprivation in vitro induced expression of NE markers in LNCaP cells compared with FBS treated cells (mean fold increase ± SEM): neuron specific enolase (ENO2) (6.0 ± 2.5), neural cell adhesion molecule (NCAM) (10.4 ± 6.8) and midkine (MDK) (13.2 ± 2.4). Cells co-treated with Enz and DHT had increased expression of NE markers compared to DHT alone: ENO2 (2.7 ± 0.6), NCAM (2.9 ± 0.3) and MDK (2.3 ± 1.8). AR knockdown resulted in a potent induction of NE markers compared with control cells: ENO2 (8.3 ± 1.4), NCAM (8.3 ± 2.4) and MDK (9.0 ± 2.2). Dox-induced Snail enhanced androgen deprivation-mediated upregulation of NE markers compared with no-Dox cells: ENO2 (1.3 ± 0.1), NCAM (8.3 ± 2.4) and MDK (9.0 ± 2.2). To more accurately model a preclinical setting, LNCaP tumors were grown subcutaneously in severe combined immune deficiency mice. Once tumors grew to 200mm3, mice were castrated and upon tumor recurrence mice were treated with Enz (10mg/kg). At the ethical endpoint, expression of EMT and NE markers will be assessed.

Patients treated with ATTs show an increase in NE-like traits. Thus, there is a need to identify molecular mechanisms involved in this adaptive response. In vitro, we have modelled the acquisition of NE-like features in PCa cells using ATTs, EMT drivers and AR knockdown. Further investigation using these models may lead to the development of biomarkers and therapeutic targets for the clinical management of advanced PCa.

Citation Format: Ellca Ratther, Katrina G. Sweeney, Nataly Stylianou, Qiuhua Hu, Gregor Tevz, Colleen C. Nelson, Elizabeth D. Williams, Brett G. Hollier. Unravelling the role of androgen targeted therapies in epithelial plasticity during prostate cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 818. doi:10.1158/1538-7445.AM2017-818

Whole-Genome Sequence of the Metastatic PC3 and LNCaP Human Prostate Cancer Cell Lines

The bone metastasis-derived PC3 and the lymph node metastasis-derived LNCaP prostate cancer cell lines are widely studied, having been described in thousands of publications over the last four decades. Here, we report short-read whole-genome sequencing (WGS) and de novo assembly of PC3 (ATCC CRL-1435) and LNCaP (clone FGC; ATCC CRL-1740) at ∼70 × coverage. A known homozygous mutation in TP53 and homozygous loss of PTEN were robustly identified in the PC3 cell line, whereas the LNCaP cell line exhibited a larger number of putative inactivating somatic point and indel mutations (and in particular a loss of stop codon events). This study also provides preliminary evidence that loss of one or both copies of the tumor suppressor Capicua (CIC) contributes to primary tumor relapse and metastatic progression, potentially offering a treatment target for castration-resistant prostate cancer (CRPC). Our work provides a resource for genetic, genomic, and biological studies employing two commonly-used prostate cancer cell lines.

Insights from engraftable immunodeficient mouse models of hyperinsulinaemia

Hyperinsulinaemia, obesity and dyslipidaemia are independent and collective risk factors for many cancers. Here, the long-term effects of a 23% Western high-fat diet (HFD) in two immunodeficient mouse strains (NOD/SCID and Rag1 -/-) suitable for engraftment with human-derived tissue xenografts, and the effect of diet-induced hyperinsulinaemia on human prostate cancer cell line xenograft growth, were investigated. Rag1 -/-and NOD/SCID HFD-fed mice demonstrated diet-induced impairments in glucose tolerance at 16 and 23 weeks post weaning. Rag1 -/- mice developed significantly higher fasting insulin levels (2.16 ± 1.01 ng/ml, P = 0.01) and increased insulin resistance (6.70 ± 1.68 HOMA-IR, P = 0.01) compared to low-fat chow-fed mice (0.71 ± 0.12 ng/ml and 2.91 ± 0.42 HOMA-IR). This was not observed in the NOD/SCID strain. Hepatic steatosis was more extensive in Rag1 -/- HFD-fed mice compared to NOD/SCID mice. Intramyocellular lipid storage was increased in Rag1 -/- HFD-fed mice, but not in NOD/SCID mice. In Rag1 -/- HFD-fed mice, LNCaP xenograft tumours grew more rapidly compared to low-fat chow-fed mice. This is the first characterisation of the metabolic effects of long-term Western HFD in two mouse strains suitable for xenograft studies. We conclude that Rag1 -/- mice are an appropriate and novel xenograft model for studying the relationship between cancer and hyperinsulinaemia.

The ascidian natural product eusynstyelamide B is a novel topoisomerase II poison that induces DNA damage and growth arrest in prostate and breast cancer cells

As part of an anti-cancer natural product drug discovery program, we recently identified eusynstyelamide B (EB), which displayed cytotoxicity against MDA-MB-231 breast cancer cells (IC₅₀ = 5 μM) and induced apoptosis. Here, we investigated the mechanism of action of EB in cancer cell lines of the prostate (LNCaP) and breast (MDA-MB-231). EB inhibited cell growth (IC₅₀ = 5 μM) and induced a G2 cell cycle arrest, as shown by a significant increase in the G2/M cell population in the absence of elevated levels of the mitotic marker phospho-histone H3. In contrast to MDA-MB-231 cells, EB did not induce cell death in LNCaP cells when treated for up to 10 days. Transcript profiling and Ingenuity Pathway Analysis suggested that EB activated DNA damage pathways in LNCaP cells. Consistent with this, CHK2 phosphorylation was increased, p21^CIP1/WAF1 was up-regulated and CDC2 expression strongly reduced by EB. Importantly, EB caused DNA double-strand breaks, yet did not directly interact with DNA. Analysis of topoisomerase II-mediated decatenation discovered that EB is a novel topoisomerase II poison.

Modulation of paracrine signaling by CD9 positive small extracellular vesicles mediates cellular growth of androgen deprived prostate cancer

Proliferation and maintenance of both normal and prostate cancer (PCa) cells is highly regulated by steroid hormones, particularly androgens, and the extracellular environment. Herein, we identify the secretion of CD9 positive extracellular vesicles (EV) by LNCaP and DUCaP PCa cells in response to dihydrotestosterone (DHT) and use nano-LC–MS/MS to identify the proteins present in these EV. Subsequent bioinformatic and pathway analyses of the mass spectrometry data identified pathologically relevant pathways that may be altered by EV contents. Western blot and CD9 EV TR-FIA assay confirmed a specific increase in the amount of CD9 positive EV in DHT-treated LNCaP and DUCaP cells and treatment of cells with EV enriched with CD9 after DHT exposure can induce proliferation in androgen-deprived conditions. siRNA knockdown of endogenous CD9 in LNCaPs reduced cellular proliferation and expression of AR and prostate specific antigen (PSA) however knockdown of AR did not alter CD9 expression, also implicating CD9 as an upstream regulator of AR. Moreover CD9 positive EV were also found to be significantly higher in plasma from prostate cancer patients in comparison with benign prostatic hyperplasia patients. We conclude that CD9 positive EV are involved in mediating paracrine signalling and contributing toward prostate cancer progression.

Bioactive Dihydro-β-agarofuran Sesquiterpenoids from the Australian Rainforest Plant Maytenus bilocularis

Chemical investigations of the CH2Cl2 extract obtained from the leaves of the Australian rainforest tree Maytenus bilocularis afforded three new dihydro-β-agarofurans, bilocularins A-C (1-3), and six known congeners, namely, celastrine A (4), 1α,6β,8α-triacetoxy-9α-benzoyloxydihydro-β-agarofuran (5), 1α,6β-diacetoxy-9α-benzoyloxy-8α-hydroxydihydro-β-agarofuran (6), Ejap-10 (11), 1α,6β-diacetoxy-9β-benzoyloxydihydro-β-agarofuran (12), and Ejap-2 (13). The major compound 1 was used in semisynthetic studies to afford four ester derivatives (7-10). The chemical structures of 1-3 were elucidated following analysis of 1D/2D NMR and MS data. The absolute configurations of bilocularins A (1) and B (2) were determined by single-crystal X-ray diffraction analysis. All compounds were evaluated for cytotoxic activity against the human prostate cancer cell line LNCaP; none of the compounds were active. However, several compounds showed similar potency to the drug efflux pump inhibitor verapamil in reversing the drug resistance of the human leukemia CEM/VCR R cell line. In addition, similar to verapamil, compound 5 was found to inhibit leucine uptake in LNCaP cells (IC50 = 15.5 μM), which was more potent than the leucine analogue 2-aminobicyclo[2.2.1]heptane-2-carbocyclic acid. This is the first report of secondary metabolites from Maytenus bilocularis.

Target Acquired: Progress and Promise of Targeted Therapeutics in the Treatment of Prostate Cancer

Cancer is fundamentally a genomic disease caused by mutations or rearrangements in the DNA or epigenetic machinery of a patient. An emerging field in cancer treatment targets key aberrations arising from the mutational landscape of an individual patient's disease rather than employing a cancer-wide cytotoxic therapy approach. In prostate cancer in particular, where there is an observed variation in response to standard treatments between patients with disease of a similar pathological stage and grade, mutationdirected treatment may grow to be a viable tool for clinicians to tailor more effective treatments. This review will describe a number of mutations across multiple forms of cancer that have been successfully antagonised by targeted therapeutics including their identification, the development of targeted compounds to combat them and the development of resistance to these therapies. This review will continue to examine these same mutations in the treatment and management of prostate cancer; the prevalence of targetable mutations in prostate cancer, recent clinical trials of targeted-agents and the potential or limitations for their use.

Repositioning "old" drugs for new causes: identifying new inhibitors of prostate cancer cell migration and invasion

The majority of prostate cancer (PCa) deaths occur due to the metastatic spread of tumor cells to distant organs. Currently, there is a lack of effective therapies once tumor cells have spread outside the prostate. It is therefore imperative to rapidly develop therapeutics to inhibit the metastatic spread of tumor cells. Gain of cell motility and invasive properties is the first step of metastasis and by inhibiting motility one can potentially inhibit metastasis. Using the drug repositioning strategy, we developed a cell-based multi-parameter primary screening assay to identify drugs that inhibit the migratory and invasive properties of metastatic PC-3 PCa cells. Following the completion of the primary screening assay, 33 drugs were identified from an FDA approved drug library that either inhibited migration or were cytotoxic to the PC-3 cells. Based on the data obtained from the subsequent validation studies, mitoxantrone hydrochloride, simvastatin, fluvastatin and vandetanib were identified as strong candidates that can inhibit both the migration and invasion of PC-3 cells without significantly affecting cell viability. By employing the drug repositioning strategy instead of a de novo drug discovery and development strategy, the identified drug candidates have the potential to be rapidly translated into the clinic for the management of men with aggressive forms of PCa.

Identification of a novel fusion transcript between human relaxin-1 (RLN1) and human relaxin-2 (RLN2) in prostate cancer

Simultaneous expression of highly homologous RLN1 and RLN2 genes in prostate impairs their accurate delineation. We used PacBio SMRT sequencing and RNA-Seq in LNCaP cells in order to dissect the expression of RLN1 and RLN2 variants. We identified a novel fusion transcript comprising the RLN1 and RLN2 genes and found evidence of its expression in the normal and prostate cancer tissues. The RLN1-RLN2 fusion putatively encodes RLN2 isoform with the deleted secretory signal peptide. The identification of the fusion transcript provided information to determine unique RLN1-RLN2 fusion and RLN1 regions. The RLN1-RLN2 fusion was co-expressed with RLN1 in LNCaP cells, but the two gene products were inversely regulated by androgens. We showed that RLN1 is underrepresented in common PCa cell lines in comparison to normal and PCa tissue. The current study brings a highly relevant update to the relaxin field, and will encourage further studies of RLN1 and RLN2 in PCa and broader.

Cytotoxic C20 Diterpenoid Alkaloids from the Australian Endemic Rainforest Plant Anopterus macleayanus

In order to identify new anticancer compounds from nature, a prefractionated library derived from Australian endemic plants was generated and screened against the prostate cancer cell line LNCaP using a metabolic assay. Fractions from the seeds, leaves, and wood of Anopterus macleayanus showed cytotoxic activity and were subsequently investigated using a combination of bioassay-guided fractionation and mass-directed isolation. This led to the identification of four new diterpenoid alkaloids, 6α-acetoxyanopterine (1), 4'-hydroxy-6α-acetoxyanopterine (2), 4'-hydroxyanopterine (3), and 11α-benzoylanopterine (4), along with four known compounds, anopterine (5), 7β-hydroxyanopterine (6), 7β,4'-dihydroxyanopterine (7), and 7β-hydroxy-11α-benzoylanopterine (8); all compounds were purified as their trifluoroacetate salt. The chemical structures of 1-8 were elucidated after analysis of 1D/2D NMR and MS data. Compounds 1-8 were evaluated for cytotoxic activity against a panel of human prostate cancer cells (LNCaP, C4-2B, and DuCaP) and nonmalignant cell lines (BPH-1 and WPMY-1), using a live-cell imaging system and a metabolic assay. All compounds showed potent cytotoxicity with IC50 values of <400 nM; compound 1 was the most active natural product from this series, with an IC50 value of 3.1 nM toward the LNCaP cell line. The live-cell imaging assay on 1-8 showed a concentration- and time-dependent effect on the cell morphology and proliferation of LNCaP cells.

Fusion transcript loci share many genomic features with non-fusion loci

BACKGROUND

Fusion transcripts are found in many tissues and have the potential to create novel functional products. Here, we investigate the genomic sequences around fusion junctions to better understand the transcriptional mechanisms mediating fusion transcription/splicing. We analyzed data from prostate (cancer) cells as previous studies have shown extensively that these cells readily undergo fusion transcription.

RESULTS

We used the FusionMap program to identify high-confidence fusion transcripts from RNAseq data. The RNAseq datasets were from our (N = 8) and other (N = 14) clinical prostate tumors with adjacent non-cancer cells, and from the LNCaP prostate cancer cell line that were mock-, androgen- (DHT), and anti-androgen- (bicalutamide, enzalutamide) treated. In total, 185 fusion transcripts were identified from all RNAseq datasets. The majority (76%) of these fusion transcripts were 'read-through chimeras' derived from adjacent genes in the genome. Characterization of sequences at fusion loci were carried out using a combination of the FusionMap program, custom Perl scripts, and the RNAfold program. Our computational analysis indicated that most fusion junctions (76%) use the consensus GT-AG intron donor-acceptor splice site, and most fusion transcripts (85%) maintained the open reading frame. We assessed whether parental genes of fusion transcripts have the potential to form complementary base pairing between parental genes which might bring them into physical proximity. Our computational analysis of sequences flanking fusion junctions at parental loci indicate that these loci have a similar propensity as non-fusion loci to hybridize. The abundance of repetitive sequences at fusion and non-fusion loci was also investigated given that SINE repeats are involved in aberrant gene transcription. We found few instances of repetitive sequences at both fusion and non-fusion junctions. Finally, RT-qPCR was performed on RNA from both clinical prostate tumors and adjacent non-cancer cells (N = 7), and LNCaP cells treated as above to validate the expression of seven fusion transcripts and their respective parental genes. We reveal that fusion transcript expression is similar to the expression of parental genes.

CONCLUSIONS

Fusion transcripts maintain the open reading frame, and likely use the same transcriptional machinery as non-fusion transcripts as they share many genomic features at splice/fusion junctions.

The fatty acid synthase inhibitor triclosan: repurposing an anti-microbial agent for targeting prostate cancer

Inhibition of FASN has emerged as a promising therapeutic target in cancer, and numerous inhibitors have been investigated. However, severe pharmacological limitations have challenged their clinical testing. The synthetic FASN inhibitor triclosan, which was initially developed as a topical antibacterial agent, is merely affected by these pharmacological limitations. Yet, little is known about its mechanism in inhibiting the growth of cancer cells. Here we compared the cellular and molecular effects of triclosan in a panel of eight malignant and non-malignant prostate cell lines to the well-known FASN inhibitors C75 and orlistat, which target different partial catalytic activities of FASN. Triclosan displayed a superior cytotoxic profile with a several-fold lower IC50 than C75 or orlistat. Structure-function analysis revealed that alcohol functionality of the parent phenol is critical for inhibitory action. Rescue experiments confirmed that end product starvation was a major cause of cytotoxicity. Importantly, triclosan, C75 and orlistat induced distinct changes to morphology, cell cycle, lipid content and the expression of key enzymes of lipid metabolism, demonstrating that inhibition of different partial catalytic activities of FASN activates different metabolic pathways. These finding combined with its well-documented pharmacological safety profile make triclosan a promising drug candidate for the treatment of prostate cancer.

Analysis of androgen and anti-androgen regulation of KLK-related peptidase 2, 3, and 4 alternative transcripts in prostate cancer

We assessed whether alternative transcripts (using KLK2, KLK3 and KLK4 as models) are differentially regulated by androgens and anti-androgens as an indicator of prostate cancers as they acquire treatment resistance. Using RNAseq of LNCaP cells treated with dihydrotestosterone, bicalutamide and enzalutamide, we show that the expression of variant KLK transcripts is markedly different to other variant transcripts at those loci. We also reveal that KLK variants are also over 2-fold more highly expressed in prostate cancers compared to their corresponding normal prostate. We propose that androgens and anti-androgens can activate specific variant transcripts of critical prostate cancer genes during treatment resistance.

EVERSUN: a phase 2 trial of alternating sunitinib and everolimus as first-line therapy for advanced renal cell carcinoma

BACKGROUND

We hypothesised that alternating inhibitors of the vascular endothelial growth factor receptor (VEGFR) and mammalian target of rapamycin pathways would delay the development of resistance in advanced renal cell carcinoma (aRCC).

PATIENTS AND METHODS

A single-arm, two-stage, multicentre, phase 2 trial to determine the activity, feasibility, and safety of 12-week cycles of sunitinib 50 mg daily 4 weeks on / 2 weeks off, alternating with everolimus 10 mg daily for 5 weeks on / 1 week off, until disease progression or prohibitive toxicity in favourable or intermediate-risk aRCC. The primary end point was proportion alive and progression-free at 6 months (PFS6m). The secondary end points were feasibility, tumour response, overall survival (OS), and adverse events (AEs). The correlative objective was to assess biomarkers and correlate with clinical outcome.

RESULTS

We recruited 55 eligible participants from September 2010 to August 2012.

DEMOGRAPHICS

mean age 61, 71% male, favourable risk 16%, intermediate risk 84%. Cycle 2 commenced within 14 weeks for 80% of participants; 64% received ≥22 weeks of alternating therapy; 78% received ≥22 weeks of any treatment. PFS6m was 29/55 (53%; 95% confidence interval [CI] 40% to 66%). Tumour response rate was 7/55 (13%; 95% CI 4% to 22%, all partial responses). After median follow-up of 20 months, 47 of 55 (86%) had progressed with a median progression-free survival of 8 months (95% CI 5-10), and 30 of 55 (55%) had died with a median OS of 17 months (95% CI 12-undefined). AEs were consistent with those expected for each single agent. No convincing prognostic biomarkers were identified.

CONCLUSIONS

The EVERSUN regimen was feasible and safe, but its activity did not meet pre-specified values to warrant further research. This supports the current approach of continuing anti-VEGF therapy until progression or prohibitive toxicity before changing treatment.

AUSTRALIAN NEW ZEALAND CLINICAL TRIALS REGISTRY

ACTRN12609000643279.

Design and Synthesis of a Screening Library Using the Natural Product Scaffold 3-Chloro-4-hydroxyphenylacetic Acid

The fungal metabolite 3-chloro-4-hydroxyphenylacetic acid (1) was utilized in the generation of a unique drug-like screening library using parallel solution-phase synthesis. A 20-membered amide library (3-22) was generated by first converting 1 to methyl (3-chloro-4-hydroxyphenyl)acetate (2), then reacting this scaffold with a diverse series of primary amines via a solvent-free aminolysis procedure. The structures of the synthetic analogues (3-22) were elucidated by spectroscopic data analysis. The structures of compounds 8, 12, and 22 were confirmed by single X-ray crystallographic analysis. All compounds were evaluated for cytotoxicity against a human prostate cancer cell line (LNCaP) and for antiparasitic activity toward Trypanosoma brucei brucei and Plasmodium falciparum and showed no significant activity at 10 μM. The library was also tested for effects on the lipid content of LNCaP and PC-3 prostate cancer cells, and it was demonstrated that the fluorobenzyl analogues (12-14) significantly reduced cellular phospholipid and neutral lipid levels.

Targeting ASCT2-mediated glutamine uptake blocks prostate cancer growth and tumour development

Glutamine is conditionally essential in cancer cells, being utilized as a carbon and nitrogen source for macromolecule production, as well as for anaplerotic reactions fuelling the tricarboxylic acid (TCA) cycle. In this study, we demonstrated that the glutamine transporter ASCT2 (SLC1A5) is highly expressed in prostate cancer patient samples. Using LNCaP and PC‐3 prostate cancer cell lines, we showed that chemical or shRNA‐mediated inhibition of ASCT2 function in vitro decreases glutamine uptake, cell cycle progression through E2F transcription factors, mTORC1 pathway activation and cell growth. Chemical inhibition also reduces basal oxygen consumption and fatty acid synthesis, showing that downstream metabolic function is reliant on ASCT2‐mediated glutamine uptake. Furthermore, shRNA knockdown of ASCT2 in PC‐3 cell xenografts significantly inhibits tumour growth and metastasis in vivo, associated with the down‐regulation of E2F cell cycle pathway proteins. In conclusion, ASCT2‐mediated glutamine uptake is essential for multiple pathways regulating the cell cycle and cell growth, and is therefore a putative therapeutic target in prostate cancer. © 2015 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

The tumour-promoting receptor tyrosine kinase, EphB4, regulates expression of integrin-β8 in prostate cancer cells

Background

The EphB4 receptor tyrosine kinase is overexpressed in many cancers including prostate cancer. The molecular mechanisms by which this ephrin receptor influences cancer progression are complex as there are tumor-promoting ligand-independent mechanisms in place as well as ligand-dependent tumor suppressive pathways.

Methods

We employed transient knockdown of EPHB4 in prostate cancer cells, coupled with gene microarray analysis, to identify genes that were regulated by EPHB4 and may represent linked tumor-promoting factors. We validated target genes using qRT-PCR and employed functional assays to determine their role in prostate cancer migration and invasion.

Results

We discovered that over 500 genes were deregulated upon EPHB4 siRNA knockdown, with integrin β8 (ITGB8) being the top hit (29-fold down-regulated compared to negative non-silencing siRNA). Gene ontology analysis found that the process of cell adhesion was highly deregulated and two other integrin genes, ITGA3 and ITGA10, were also differentially expressed. In parallel, we also discovered that over-expression of EPHB4 led to a concomitant increase in ITGB8 expression. In silico analysis of a prostate cancer progression microarray publically available in the Oncomine database showed that both EPHB4 and ITGB8 are highly expressed in prostatic intraepithelial neoplasia, the precursor to prostate cancer. Knockdown of ITGB8 in PC-3 and 22Rv1 prostate cancer cells in vitro resulted in significant reduction of cell migration and invasion.

Conclusions

These results reveal that EphB4 regulates integrin β8 expression and that integrin β8 plays a hitherto unrecognized role in the motility of prostate cancer cells and thus targeting integrin β8 may be a new treatment strategy for prostate cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1164-6) contains supplementary material, which is available to authorized users.