An integrative proteomics approach identifies tyrosine kinase KIT as a therapeutic target for SPINK1-positive prostate cancer

Elevated serine peptidase inhibitor, Kazal type 1 (SPINK1) levels in ∼10%-25% of prostate cancer (PCa) patients associate with aggressive phenotype, for which there are limited treatment choices and dismal clinical outcomes. Using an integrative proteomics approach involving label-free phosphoproteome and proteome profiling, we delineated the downstream signaling pathways involved in SPINK1-mediated tumorigenesis and identified tyrosine kinase KIT as highly enriched. Furthermore, high to moderate levels of KIT expression were detected in ∼85% of SPINK1-positive PCa specimens. We show KIT signaling orchestrates SPINK1-mediated oncogenesis, and treatment with KIT inhibitor reduces tumor growth and metastases in preclinical mice models. Mechanistically, KIT signaling modulates WNT/β-catenin pathway and confers stemness-related features in PCa. Notably, inhibiting KIT signaling led to restoration of AR/REST levels, forming a feedback loop enabling SPINK1 repression. Overall, we uncover the role of KIT signaling downstream of SPINK1 in maintaining lineage plasticity and provide distinct treatment modalities for advanced-stage SPINK1-positive patients.

Targeting MALAT1 Augments Sensitivity to PARP Inhibition by Impairing Homologous Recombination in Prostate Cancer

PARP inhibitors (PARPi) have emerged as a promising targeted therapeutic intervention for metastatic castrate-resistant prostate cancer (mCRPC). However, the clinical utility of PARPi is limited to a subset of patients who harbor aberrations in the genes associated with the homologous recombination (HR) pathway. Here, we report that targeting metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), an oncogenic long noncoding RNA (lncRNA), contrives a BRCAness-like phenotype, and augments sensitivity to PARPi. Mechanistically, we show that MALAT1 silencing reprograms the homologous recombination (HR) transcriptome and makes prostate cancer cells more vulnerable to PARPi. Particularly, coinhibition of MALAT1 and PARP1 exhibits a decline in clonogenic survival, delays resolution of γH2AX foci, and reduces tumor burden in mice xenograft model. Moreover, we show that miR-421, a tumor suppressor miRNA, negatively regulates the expression of HR genes, while in aggressive prostate cancer cases, miR-421 is sequestered by MALAT1, leading to increased expression of HR genes. Conclusively, our findings suggest that MALAT1 ablation confers sensitivity to PARPi, thus highlighting an alternative therapeutic strategy for patients with castration-resistant prostate cancer (CRPC), irrespective of the alterations in HR genes.

SIGNIFICANCE

PARPi are clinically approved for patients with metastatic CRPC carrying mutations in HR genes, but are ineffective for HR-proficient prostate cancer. Herein, we show that oncogenic lncRNA, MALAT1 is frequently overexpressed in advanced stage prostate cancer and plays a crucial role in maintaining genomic integrity. Importantly, we propose a novel therapeutic strategy that emphasizes MALAT1 inhibition, leading to HR dysfunction in both HR-deficient and -proficient prostate cancer, consequently augmenting their susceptibility to PARPi.

Transcription networks rewire gene repertoire to coordinate cellular reprograming in prostate cancer

Transcription factors (TFs) represent the most commonly deregulated DNA-binding class of proteins associated with multiple human cancers. They can act as transcriptional activators or repressors that rewire the cistrome, resulting in cellular reprogramming during cancer progression. Deregulation of TFs is associated with the onset and maintenance of various cancer types including prostate cancer. An emerging subset of TFs has been implicated in the regulation of multiple cancer hallmarks during tumorigenesis. Here, we discuss the role of key TFs which modulate transcriptional cicuitries involved in the development and progression of prostate cancer. We further highlight the role of TFs associated with key cancer hallmarks, including, chromatin remodeling, genome instability, DNA repair, invasion, and metastasis. We also discuss the pluripotent function of TFs in conferring lineage plasticity, that aids in disease progression to neuroendocrine prostate cancer. At the end, we summarize the current understanding and approaches employed for the therapeutic targeting of TFs and their cofactors in the clinical setups to prevent disease progression.

Human ERG oncoprotein represses a Drosophila LIM domain binding protein-coding gene Chip

Human ETS Related Gene, ERG, a master transcription factor, turns oncogenic upon its out-of-context activation in diverse developmental lineages. However, the mechanism underlying its lineage-specific activation of Notch (N), Wnt, or EZH2-three well-characterized oncogenic targets of ERG-remains elusive. We reasoned that deep homology in genetic tool kits might help uncover such elusive cancer mechanisms in Drosophila. By heterologous gain of human ERG in Drosophila, here we reveal Chip, which codes for a transcriptional coactivator, LIM-domain-binding (LDB) protein, as its novel target. ERG represses Drosophila Chip via its direct binding and, indirectly, via E(z)-mediated silencing of its promoter. Downregulation of Chip disrupts LIM-HD complex formed between Chip and Tailup (Tup)-a LIM-HD transcription factor-in the developing notum. A consequent activation of N-driven Wg signaling leads to notum-to-wing transdetermination. These fallouts of ERG gain are arrested upon a simultaneous gain of Chip, sequestration of Wg ligand, and, alternatively, loss of N signaling or E(z) activity. Finally, we show that the human LDB1, a homolog of Drosophila Chip, is repressed in ERG-positive prostate cancer cells. Besides identifying an elusive target of human ERG, our study unravels an underpinning of its lineage-specific carcinogenesis.

Red-emitting polyaniline-based nanoparticle probe for pH-sensitive fluorescence imaging

Fluorescent probes based on semiconducting polymer nanoparticles (NPs) such as polyaniline (PANI) usually require external fluorophore doping to provide fluorescence function. Direct use of PANI-based NPs for bioimaging applications has been limited by PANI's weak blue fluorescence and aggregation-induced quenching in physiological medium. In this report, we developed a facile solid-state synthesis method to produce fluorescent polyaniline nanoparticles (FPNs) that are not only water-soluble but also exhibit high intensity and pH-sensitive red fluorescence. The FPNs showed high photoluminescence quantum yield (PLQY) of 19.3 % at physiological pH, which makes FPNs ideal for application as fluorescent nanoprobes in bioimaging. Moreover, we performed an in-depth study of photoluminescence dependence on pH and the phenomena of exciton-polaron quenching at low pH was highlighted. We also found that the ratio of emission intensity at 600 nm and 650 nm increased from 0.04 to 1.65 as pH was raised from 2.6 to 11.8, which could find its application in ratiometric pH sensing. FPNs exhibited excellent biocompatibility with >85 % cell viability for fibroblasts NIH/3 T3 and prostate cancer 22RV1 cells even at concentrations as high as 1000 μg/mL. In addition, fluorescence microscopy demonstrated concentration-dependent red fluorescence in the cytoplasm owing to the cellular uptake of FPNs in prostate cancer cells.

Nuclear magnetic resonance spectroscopy reveals dysregulation of monounsaturated fatty acid metabolism upon SPINK1 attenuation in colorectal cancer

Metabolic reprogramming, a key hallmark of cancer, plays a pivotal role in fulfilling the accelerated biological demands of tumor cells. Such metabolic changes trigger the production of several proinflammatory factors, thereby inciting cancer development and its progression. Serine protease inhibitor Kazal Type 1 (SPINK1), well known for its oncogenic role and its upregulation via acute-phase reactions, is highly expressed in multiple cancers including colorectal cancer (CRC). Here, we show accumulation of lipid droplets in CRC cells stained with Oil Red O upon SPINK1 silencing. Furthermore, NMR spectroscopy analysis revealed an accretion of monounsaturated fatty acids (MUFAs) and phosphatidylcholine in these CRC cells, while the levels of polyunsaturated fatty acids remained unaltered. This alteration indicates the presence of MUFAs with the triglycerides in the lipid droplets as observed in SPINK1-silenced CRC cells. Considering the role of MUFAs in the anti-inflammatory response, our data hint that suppression of SPINK1 in CRC leads to activation of an anti-inflammatory signaling milieu. Conclusively, our study uncovers a connection between lipid metabolism and SPINK1-mediated CRC progression, hence paving the way for further exploration and better prognosis of SPINK1-positive CRC patients.

Abstract 6246: WNT signaling-mediated DKC1 expression drives stemness associated with colorectal cancer

The emergence of subclonal mutations in high grade colorectal (CRC) tumors driving resistance against EGFR targeting is a major challenge, thus necessitating the discovery of alternative therapeutic strategies. Targeting aberrantly active WNT signaling provides an alternate route for CRC treatment. Here we show that the high DKC1 expression in CRC patients associates with advanced-stage disease regardless of RAS/RAF mutation status, indicating the potential of DKC1 as a pan-CRC therapeutic target. We show a direct regulation of DKC1 downstream of canonical WNT signaling and confirm it as one of the WNT targets. Mechanistically, DKC1 regulates several critical cellular processes such as telomere maintenance, pseudouridylation of ribosomal RNAs, ribosomal biogenesis, etc. However, its plausible association with cancer stemness remains largely unexplored. We generated stable DKC1 knockdown (DKC1-KD) cell lines, namely WiDr and Colo320HSR to investigate its role in cancer stemness and CRC progression. DKC1-KD cells show a significant reduction in the tumor sphere forming ability along with diminished cell surface expression of stemness markers. Using multiple publicly available gene expression datasets for CRC patients, we performed Gene Set Variation Analysis to characterize the association of DKC1 with upregulated gene signature of consensus molecular subtype 2 (CMS2) of CRC, which has been associated with the highest incidence rate and active WNT signaling. Further, Database for Annotation Visualization and Integrated Discovery tool-based analysis across these CRC patient samples striated based on DKC1 expression shows positive enrichment of biological processes related to cell cycle regulation. Consistently, we observed a G2/M phase cell cycle arrest upon silencing DKC1 in CRC cells. We also show that silencing DKC1 results in enhanced chemosensitivity with a remarkable reduction in lipid accumulation. Moreover, upon DKC1 silencing, an increase in epithelial marker E-cadherin and a decrease in mesenchymal marker N-cadherin expression was observed, suggesting its role in epithelial-to-mesenchymal transition (EMT) in CRC. Our findings demonstrate the role of DKC1 in regulating stemness, drug resistance, and EMT to drive CRC oncogenicity. Taken together, we highlight the role of DKC1 as the most suitable pan-CRC drug target by employing the potential of pharmacological inhibitors against WNT signaling.

Citation Format: Shivansh Nigam, Ayush Praveen, Bushra Ateeq. WNT signaling-mediated DKC1 expression drives stemness associated with colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6246.

Abstract 5585: Inhibition of CSF1R enhances the antitumor efficacy of DC derived exosomes by modulating immunosuppressive tumor microenvironment

Dendritic cell (DC) derived exosomes (Dex) provide many advantages over DC vaccines such as cost effectiveness, stability, sensitivity to the systemic microenvironment. Though, Dex showed better therapeutic outcome in murine models, however, desired outcome was not achieved in clinical trials as it failed to induce robust immunity to modulate the immunosuppressive tumor microenvironment (TME). Colony stimulating factor-1 (CSF-1) binds to its receptor (CSF-1R) and recruits tumor associated macrophages (TAMs) and myeloid derived suppressor cells (MDSCs) in the TME which eventually creates the tumor immunosuppressive. Hence, in this study we used PLX-3397, a small molecule inhibitor of CSF-1R to enhance the antitumor efficacy of Dex. In a syngenic B16-F10murine melanoma model, we found that the combination treatment delayed the tumor growth and improved the survival compare to the mono therapy. In TME, the combination treatment significantly depleted the TAMs and MDSCs and increased the infiltration of lymphocytes (TILs). Additionally, Th1 population were found significantly higher in tumor as well as in spleen with mice received both Dex and PLX3397. In conclusion, PLX-3397 enhanced the in vivo antitumor efficacy of Dex by modulating the immunosuppressive microenvironment in tumor.

Citation Format: Anjali Barnwal, Jayanta Bhattacharyya, Bushra Ateeq. Inhibition of CSF1R enhances the antitumor efficacy of DC derived exosomes by modulating immunosuppressive tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5585.

Abstract 1542: MALAT1 ablation dismantles homologous recombination repair machinery and sensitizes castrate resistant prostate cancer cells to PARP inhibitor

Poly (ADP-ribose) polymerase (PARP) inhibitors have emerged as a promising target of intervention for metastatic castration-resistant prostate cancer (mCRPC), as approximately one-third of mCRPC patients harbor mutations in the genes associated with the homologous recombination (HR) pathway. Nonetheless, most patients inevitably develop resistance to PARP inhibition (PARPi), due to the induction of reversion mutations in the HR pathway. These mutations restore the function of HR genes and revert to the HR-proficient stage, which in turn decreases the vulnerability of cancer cells to PARP inhibitors. Here, we report that the clinical utility of PARPi could be efficaciously extended by targeting Metastasis associated lung adenocarcinoma transcript (MALAT1), a long non-coding RNA (lncRNA) often elevated in advanced-stage prostate cancer (PCa). In support of this, we show that mCRPC patients exhibit higher expression of genes involved in HR, which positively correlate with MALAT1 levels. Furthermore, RNA interference (RNAi)-mediated depletion of MALAT1 in CRPC cells perturb the expression of key HR genes, namely BRCA1/2, RAD51, EXO1, CHEK1/2, subsequently resulting in HR deficiency. This, in turn, escalates accumulation of DNA lesions in the MALAT1 ablated cells as noticed by abundance in γH2AX, a marker for DNA damage. As a consequence, MALAT1 ablated cells instigates G1/S phase arrest to fetch additional time to repair the damaged DNA or to induce apoptosis. Furthermore, we also provide evidence that the HR deficiency induced by MALAT1 depletion phenocopies “BRCAness” and exhibits synergy with clinically approved DNA repair inhibitors such as Olaparib. In particular, co-inhibition of MALAT1 and PARP1 exhibits a significant anti-proliferative effect reduced clonogenic survival and delays the resolution of γH2AX foci in CRPC cell lines. Taken together, our results establish that MALAT1 plays a central role in regulating the DNA damage response and provides a mechanistic rationale for dual targeting of MALAT1 and PARP in mCRPC patients.

Citation Format: Anjali Yadav, Tanay Biswas, Ayush Praveen, Bushra Ateeq. MALAT1 ablation dismantles homologous recombination repair machinery and sensitizes castrate resistant prostate cancer cells to PARP inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1542.

The Histone H3K27me3 Demethylases KDM6A/B Resist Anoikis and Transcriptionally Regulate Stemness-Related Genes

Epithelial cancer cells that lose attachment from the extracellular matrix (ECM) to seed in a distant organ often undergo anoikis’s specialized form of apoptosis. Recently, KDM3A (H3K9 demethylase) has been identified as a critical effector of anoikis in cancer cells. However, whether other histone demethylases are involved in promoting or resisting anoikis remains elusive. We screened the major histone demethylases and found that both H3K27 histone demethylases, namely, KDM6A/B were highly expressed during ECM detachment. Inhibition of the KDM6A/B activity by using a specific inhibitor results in reduced sphere formation capacity and increased apoptosis. Knockout of KDM6B leads to the loss of stem cell properties in solitary cells. Furthermore, we found that KDM6B maintains stemness by transcriptionally regulating the expression of stemness genes SOX2, SOX9, and CD44 in detached cells. KDM6B occupies the promoter region of both SOX2 and CD44 to regulate their expression epigenetically. We also noticed an increased occupancy of the HIF1α promoter by KDM6B, suggesting its regulatory role in maintaining hypoxia in detached cancer cells. This observation was further strengthened as we found a significant positive association in the expression of both KDM6B and HIF1α in various cancer types. Overall, our results reveal a novel transcriptional program that regulates resistance against anoikis and maintains stemness-like properties.

Transcriptional network involving ERG and AR orchestrates Distal-less homeobox-1 mediated prostate cancer progression

Distal-less homeobox-1 (DLX1) is a well-established non-invasive biomarker for prostate cancer (PCa) diagnosis, however, its mechanistic underpinnings in disease pathobiology are not known. Here, we reveal the oncogenic role of DLX1 and show that abrogating its function leads to reduced tumorigenesis and metastases. We observed that ~60% of advanced-stage and metastatic patients display higher DLX1 levels. Moreover, ~96% of TMPRSS2-ERG fusion-positive and ~70% of androgen receptor (AR)-positive patients show elevated DLX1, associated with aggressive disease and poor survival. Mechanistically, ERG coordinates with enhancer-bound AR and FOXA1 to drive transcriptional upregulation of DLX1 in ERG-positive background. However, in ERG-negative context, AR/AR-V7 and FOXA1 suffice to upregulate DLX1. Notably, inhibiting ERG/AR-mediated DLX1 transcription using BET inhibitor (BETi) or/and anti-androgen drugs reduce its expression and downstream oncogenic effects. Conclusively, this study establishes DLX1 as a direct-target of ERG/AR with an oncogenic role and demonstrates the clinical significance of BETi and anti-androgens for DLX1-positive patients.

Computational Design of BH3-Mimetic Peptide Inhibitors That Can Bind Specifically to Mcl-1 or Bcl-XL: Role of Non-Hot Spot Residues

Interactions between pro- and anti-apoptotic Bcl-2 proteins decide the fate of the cell. The BH3 domain of pro-apoptotic Bcl-2 proteins interacts with the exposed hydrophobic groove of their anti-apoptotic counterparts. Through their design and development, BH3 mimetics that target the hydrophobic groove of specific anti-apoptotic Bcl-2 proteins have the potential to become anticancer drugs. We have developed a novel computational method for designing sequences with BH3 domain features that can bind specifically to anti-apoptotic Mcl-1 or Bcl-X_L. In this method, we retained the four highly conserved hydrophobic and aspartic residues of wild-type BH3 sequences and randomly substituted all other positions to generate a large number of BH3-like sequences. We modeled 20000 complex structures with Mcl-1 or Bcl-X_L using the BH3-like sequences derived from five wild-type pro-apoptotic BH3 peptides. Peptide-protein interaction energies calculated from these models for each set of BH3-like sequences resulted in negatively skewed extreme value distributions. The selected BH3-like sequences from the extreme negative tail regions have highly favorable interaction energies with Mcl-1 or Bcl-X_L. They are enriched in acidic and basic residues when they bind to Mcl-1 and Bcl-X_L, respectively. With the charged residues often away from the binding interface, the overall electric field generated by the charged residues results in strong long-range electrostatic interaction energies between the peptide and the protein giving rise to high specificity. Cell viability studies of representative BH3-like peptides further validated the predicted specificity. This study has revealed the importance of non-hot spot residues in BH3-mimetic peptides in providing specificity to a particular anti-apoptotic protein.

Targeting AGTR1/NF-κB/CXCR4 axis by miR-155 attenuates oncogenesis in glioblastoma

Glioblastoma (GBM) represents the most aggressive malignancy of the central nervous system. Increased expression of Angiotensin II Receptor Type 1 (AGTR1) has been associated with proliferative and infiltrative properties of glioma cells. However, the underlying mechanism of AGTR1 upregulation in GBM is still unexplored. To understand the post-transcriptional regulation of AGTR1 in GBM, we screened 3'untranslated region (3'UTR) of AGTR1 for putative miRNA binding by using prediction algorithms. Interestingly, miR-155 showed conserved binding on the 3'UTR of AGTR1, subsequently confirmed by luciferase reporter assay. Furthermore, miR-155 overexpressing GBM cells show decrease in AGTR1 expression accompanied with reduced cell proliferation, invasion, foci formation and anchorage-independent growth. Strikingly, immunodeficient mice implanted with stable miR-155 overexpressing SNB19 cells show negligible tumor growth. Notably, miR-155 attenuates NF-κB signaling downstream of AGTR1 leading to reduced CXCR4 as well as AGTR1 levels. Mechanistically, miR-155 mitigates AGTR1-mediated angiogenesis, epithelial-to-mesenchymal transition, stemness, and MAPK signaling. Similar effects were observed by using pharmacological inhibitor of IκB Kinase (IKK) complex in multiple cell-based assays. Taken together, we established that miRNA-155 post-transcriptionally regulates AGTR1 expression, abrogates AGTR1/NF-κB/CXCR4 signaling axis and elicits pleiotropic anticancer effects in GBM. This study opens new avenues for using IKK inhibitors and miRNA-155 replacement therapies for the treatment of AGTR1-positive malignancies.

A Drosophila model of oral peptide therapeutics for adult intestinal stem cell tumors

Peptide therapeutics, unlike small-molecule drugs, display crucial advantages of target specificity and the ability to block large interacting interfaces, such as those of transcription factors. The transcription co-factor of the Hippo pathway, YAP/Yorkie (Yki), has been implicated in many cancers, and is dependent on its interaction with the DNA-binding TEAD/Sd proteins via a large Ω-loop. In addition, the mammalian vestigial-like (VGLL) proteins, specifically their TONDU domain, competitively inhibit YAP-TEAD interaction, resulting in arrest of tumor growth. Here, we show that overexpression of the TONDU peptide or its oral uptake leads to suppression of Yki-driven intestinal stem cell tumors in the adult Drosophila midgut. In addition, comparative proteomic analyses of peptide-treated and untreated tumors, together with chromatin immunoprecipitation analysis, reveal that integrin pathway members are part of the Yki-oncogenic network. Collectively, our findings establish Drosophila as a reliable in vivo platform to screen for cancer oral therapeutic peptides and reveal a tumor suppressive role for integrins in Yki-driven tumors.This article has an associated First Person interview with the first author of the paper.

Toxicity of exhaust particulates and gaseous emissions from gasohol (ethanol blended gasoline)-fuelled spark ignition engines

In the last couple of decades, blending of oxygenated additives with gasoline has been advocated to reduce dependence on fossil fuels and to reduce hazardous health effects of gaseous emissions and particulate matter (PM) emitted by internal combustion (IC) engines in the transport sector worldwide. The primary objective of this research was to carry out a comparative analysis of exhaust PM emitted by gasohol (gasoline blended with 10% ethanol, v/v)-fulled spark ignition (SI) engine with that of baseline gasoline-fuelled SI engine. To assess the PM toxicity, physical, chemical and biological characterizations of PM were carried out using the state-of-the-art instruments and techniques. Measurements of regulated and unregulated gaseous species were also carried out at part/full loads. The results showed that the gasohol-fuelled engine emitted relatively lower concentrations of unregulated gaseous species such as sulfur dioxide (SO2), isocyanic acid (HNCO), etc. Physical characterization of exhaust particles revealed that the gasohol-fuelled engine emitted a significantly lower number of particles compared to the gasoline-fuelled engine. The presence of harmful polycyclic aromatic hydrocarbons (PAHs) and higher trace metal concentrations in PM emitted from the gasoline-fuelled engine was another important finding of this study. Biological characterizations showed that PM emitted from the gasohol-fuelled engine were less cytotoxic and had lower reactive oxygen species (ROS) generation potential. Mutagenicity of PM emitted from the gasohol-fuelled engine was also lower compared to that from the gasoline-fuelled engine. Overall, this study demonstrated that utilization of gasohol in SI engines led to the reduction in emissions, and lowering of PM toxicity, in addition to partial replacement of fossil fuels with renewable fuels.

Dynamics of Cellular Plasticity in Prostate Cancer Progression

Despite the current advances in the treatment for prostate cancer, the patients often develop resistance to the conventional therapeutic interventions. Therapy-induced drug resistance and tumor progression have been associated with cellular plasticity acquired due to reprogramming at the molecular and phenotypic levels. The plasticity of the tumor cells is mainly governed by two factors: cell-intrinsic and cell-extrinsic. The cell-intrinsic factors involve alteration in the genetic or epigenetic regulators, while cell-extrinsic factors include microenvironmental cues and drug-induced selective pressure. Epithelial-mesenchymal transition (EMT) and stemness are two important hallmarks that dictate cellular plasticity in multiple cancer types including prostate. Emerging evidence has also pinpointed the role of tumor cell plasticity in driving anti-androgen induced neuroendocrine prostate cancer (NEPC), a lethal and therapy-resistant subtype. In this review, we discuss the role of cellular plasticity manifested due to genetic, epigenetic alterations and cues from the tumor microenvironment, and their role in driving therapy resistant prostate cancer.

Nutritive vitamins as epidrugs

Epigenetic modifications play an important role in disease pathogenesis and therefore are a focus of intense investigation. Epigenetic changes include DNA, RNA, and histone modifications along with expression of non-coding RNAs. Various factors such as environment, diet, and lifestyle can influence the epigenome. Dietary nutrients like vitamins can regulate both physiological and pathological processes through their direct impact on epigenome. Vitamin A acts as a major regulator of above-mentioned epigenetic mechanisms. B group vitamins including biotin, niacin, and pantothenic acid also participate in modulation of various epigenome. Further, vitamin C has shown to modulate both DNA methylation and histone modifications while few reports have also supported its role in miRNA-mediated pathways. Similarly, vitamin D also influences various epigenetic modifications of both DNA and histone by controlling the regulatory mechanisms. Despite the information that vitamins can modulate the epigenome, the detailed mechanisms of vitamin-mediated epigenetic regulations have not been explored fully and hence further detailed studies are required to decipher their role at epigenome level in both normal and disease pathogenesis. The current review summarizes the available literature on the role of vitamins as epigenetic modifier and highlights the key evidences for developing vitamins as potential epidrugs.

Androgen deprivation upregulates SPINK1 expression and potentiates cellular plasticity in prostate cancer

Emergence of an aggressive androgen receptor (AR)-independent neuroendocrine prostate cancer (NEPC) after androgen-deprivation therapy (ADT) is well-known. Nevertheless, the majority of advanced-stage prostate cancer patients, including those with SPINK1-positive subtype, are treated with AR-antagonists. Here, we show AR and its corepressor, REST, function as transcriptional-repressors of SPINK1, and AR-antagonists alleviate this repression leading to SPINK1 upregulation. Increased SOX2 expression during NE-transdifferentiation transactivates SPINK1, a critical-player for maintenance of NE-phenotype. SPINK1 elicits epithelial-mesenchymal-transition, stemness and cellular-plasticity. Conversely, pharmacological Casein Kinase-1 inhibition stabilizes REST, which in cooperation with AR causes SPINK1 transcriptional-repression and impedes SPINK1-mediated oncogenesis. Elevated levels of SPINK1 and NEPC markers are observed in the tumors of AR-antagonists treated mice, and in a subset of NEPC patients, implicating a plausible role of SPINK1 in treatment-related NEPC. Collectively, our findings provide an explanation for the paradoxical clinical-outcomes after ADT, possibly due to SPINK1 upregulation, and offers a strategy for adjuvant therapies.

Abstract C128: Reprogramming transcription factors SOX2 and REST modulates SPINK1 expression in governing cellular plasticity in prostate cancer

Androgen deprivation therapy (ADT) remains the clinical paradigm for the management of prostate cancer (PCa) patients. However, most of the cases inevitably become resistant to ADT, leading to a more aggressive, hormone-refractory stage known as castrate-resistant prostate cancer (CRPC). A subset of CRPC patients undergoing ADT develop tumors with low AR-signaling dependence where the luminal prostate cancer cells consequently acquire alternative lineage programs, resulting in the development of neuroendocrine prostate cancer (NEPC). In the past decade, several molecular features have been associated with progression of the adenocarcinoma to NEPC, including loss of RE1-silencing transcription factor (REST), N-MYC proto-oncogene amplification, upregulation of Aurora kinase A, neural transcription factor BRN2, and reprogramming factor SRY (sex determining region Y)-box 2 (SOX2). Nonetheless, the underlying molecular mechanism involved in lineage plasticity in neuroendocrine (NE) transdifferentaition is poorly understood and remains a matter of speculation. Overexpression of Serine Peptidase Inhibitor, Kazal type 1 (SPINK1) represents the second major molecular PCa subtype (~15-20% of the cases) associated with aggressive stage and poor patient outcome. Oncogenic role of SPINK1 in PCa has already been established, and recently SPINK1 produced in the tumor stroma was found to act as a senescence-associated secretory factor and contributes to chemoresistance in a paracrine manner. Here, we show that androgen receptor (AR) along with its corepressor REST functions as a direct transcriptional repressor of SPINK1, and blocking AR signaling using anti-androgens relieve this repression, leading to increase in SPINK1 expression. We also show that the lineage reprogramming factor SOX2 binds to the SPINK1 promoter and positively regulate its expression in androgen deprivation induced NE-transdifferentiated PCa cells. Conversely, silencing SPINK1 in the NE-transdifferentiated PCa cells result in reduced expression of epithelial-mesenchymal transition (EMT) and neuroendocrine markers accompanied with a concomitant decrease in the neurite-like projections. Moreover, castration-resistant mice xenografts treated with anti-androgens show increase in SPINK1 levels as well as EMT and neuroendocrine markers. Likewise, higher SPINK1 expression was observed in NE patient-derived organoids and NEPC clinical specimens, indicating its plausible role in cellular plasticity and NE progression. Since, REST along with AR negatively regulates SPINK1 expression, and Casein kinase 1 elicits ubiquitin-mediated proteasomal degradation of REST. Therefore, we treated SPINK1-positive PCa cells with Casein kinase 1 inhibitor (iCK1), which results in restoration of the REST expression, leading to transcriptional repression of SPINK1 as well as decrease in SPINK1-mediated oncogenesis. Taken together, we highlight the clinical complications associated with high SPINK1 levels and discovered its possible role in maintaining cellular plasticity in prostate cancer cells. Notably, stabilization of REST levels using iCK1 suggests a novel therapeutic strategy for the management of SPINK1-positive subtype and also open new avenues for the treatment modalities for CRPC patients.

Citation Format: Nishat Manzar, Ritika Tiwari, Vipul Bhatia, Anjali Yadav, Shannon Carskadon, Nilesh Gupta, Amina Zoubeidi, Matti Poutanen, Himisha Beltran, Nallasivam Palanisamy, Bushra Ateeq. Reprogramming transcription factors SOX2 and REST modulates SPINK1 expression in governing cellular plasticity in prostate cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C128. doi:10.1158/1535-7163.TARG-19-C128

Abstract C129: MicroRNA-155 targets AGTR1/NF-κB /CXCR4 axis and attenuates oncogenesis in glioblastoma

Glioblastoma (GBM) is the most aggressive malignancy of all primary brain tumors. Despite the recent advances in GBM treatment, the average survival time for a patient is less than 15 months. Therefore, we sought to investigate the molecular mechanisms underlying GBM initiation, progression and identify novel drug targets for this deadly disease. Higher levels of Angiotensin II Receptor Type 1 (AGTR1) and Angiotensin II Receptor Type 2 (AGTR2) have been associated with poor patient prognosis in astrocytomas. Additionally, contribution of these receptors in proliferative and infiltrative properties of glioma cells has already been established. Moreover, overexpression of AGTR1 has been known to play a critical role in multiple human malignancies including brain. However, the underlying mechanism involved in AGTR1 upregulation in GBM is not clearly understood and remains a matter of conjecture. Here, we analysed online available RNA-seq data from two independent GBM patients’ cohorts for AGTR1 expression and observed significant overexpression of AGTR1 in glioma patients compared to normal adjacent tissue. Importantly, the overall survival probability of GBM patients with high AGTR1 expression was low as compared to patients with low AGTR1 levels. To understand the post-transcriptional regulation of AGTR1 in GBM, we employed miRNA prediction algorithms namely, TargetScan, miRanda (microRNA.org), MicroT4 (DIANA tools), RNA22 along with experimentally supported database (TarBase), and examined miRNAs that bind to 3’UTR of AGTR1. Interestingly, conserved binding of miRNA-155 was predicted by all algorithms. Further, AGTR1-3’UTR-luciferase reporter assay in HEK-293T cells also confirmed the miRNA-155 mediated post-transcriptional regulation of AGTR1. Moreover, ectopic expression of miRNA-155 in GBM cells abrogate AGTR1-mediated proliferation, invasion, foci formation and anchorage independent growth. Intriguingly, immunodeficient mice implanted with stable miRNA-155 overexpressing SNB19 cells showed a significant reduction (~95%) in tumor burden as compared to the control group. Mechanistically, we showed that miRNA-155 attenuates AGTR1-mediated epithelial-to-mesenchymal transition, angiogenesis, ERK/MAPK signaling and promotes apoptosis. Importantly, stimulation with Angiotensin II (Ang II), a bonafide ligand of AGTR1, results in activation of NF-κB signaling downstream of AGTR1, followed by an increase in expression of C-X-C chemokine receptor type 4 (CXCR4) and AGTR1. Conversely, miRNA-155 overexpression in GBM cells attenuate NF-κB signalling, leading to a notable decrease in the expression of CXCR4 and its downstream signalling accompanied with reduction in AGTR1 levels. Alternately, we treated GBM cells with IKK-16, an inhibitor of IKK complex, to abrogate the NF-κB signalling downstream of AGTR1. Interestingly, we observed a significant reduction in the AGTR1 expression along with a marked decrease in CXCR4 expression. Taken together, we demonstrate that miRNA-155 is involved in post-transcriptional regulation of AGTR1 and disrupts AGTR1/NF-κB /CXCR4 signaling axis via anticancer pleiotropic effects. The present study opens new avenues to use IKK inhibitors and possible use of miRNA-155 replacement therapy for AGTR1-positive malignancies.

Citation Format: Anukriti Singh, Nidhi Srivastava, Bushra Ateeq. MicroRNA-155 targets AGTR1/NF-κB /CXCR4 axis and attenuates oncogenesis in glioblastoma [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C129. doi:10.1158/1535-7163.TARG-19-C129

Caspase-3 mediated programmed cell death by a gold-stabilised peptide carbene

The synthesis of novel N-heterocyclic carbene complexes derived from a tripeptide ligand (L), containing non-natural amino acid, thiazolylalanine is described here. The peptide ligand was reacted with suitable precursors to generate gold and mercury carbene complexes. The plausible structures of both complexes were predicted by spectroscopic data and DFT calculations. The binding energy data was also analyzed to predict their stability. The gold carbene complex (1A), showed activity against MCF7 breast cancer cell line due to mitochondrial triggered caspase-3 mediated programmed cell death. Its internalization inside cells could be observed due to autofluorescence. This study affords a methodology for successful generation of peptide carbene complexes for their therapeutic potential.

Molecular Underpinnings Governing Genetic Complexity of ETS-Fusion-Negative Prostate Cancer

Inter- and intra-patient molecular heterogeneity of primary and metastatic prostate cancer (PCa) confers variable clinical outcome and poses a formidable challenge in disease management. High-throughput integrative genomics and functional approaches have untangled the complexity involved in this disease and revealed a spectrum of diverse aberrations prevalent in various molecular subtypes, including ETS fusion negative. Emerging evidence indicates that SPINK1 upregulation, mutations in epigenetic regulators or chromatin modifiers, and SPOP are associated with the ETS-fusion negative subtype. Additionally, patients with defects in a DNA-repair pathway respond to poly-(ADP-ribose)-polymerase (PARP) inhibition therapies. Furthermore, a new class of immunogenic subtype defined by CDK12 biallelic loss has also been identified in ETS-fusion-negative cases. This review focuses on the emerging molecular underpinnings driving key oncogenic aberrations and advancements in therapeutic strategies of this disease.

Abstract 5225: Androgen deprivation upregulates SPINK1 expression and potentiates cellular plasticity in prostate cancer

The Serine Peptidase Inhibitor, Kazal type 1 (SPINK1) overexpression represents the second-largest prostate cancer (PCa) subtype associated with increased risk of recurrence and poor prognosis. Regardless of molecular subtype, androgen-deprivation therapy (ADT) remains the mainstay treatment for locally advanced and metastatic PCa patients. However, majority of the treated individuals eventually progress to castration-resistant stage and a subset of these patients develop ADT-induced neuroendocrine prostate cancer. Despite evidences of detrimental effects of ADT on PCa, possible role of androgen signaling in SPINK1-mediated prostate oncogenesis remains unexplored. Here, we show that androgen receptor (AR) functions as a direct transcriptional repressor of SPINK1, and blocking AR signaling relieves its repression, leading to upregulation of SPINK1. In agreement, we observe an inverse association between SPINK1 levels and AR expression across multiple patient cohorts, and in neuroendocrine differentiated LNCaP cells. We show that AR and its corepressor, the RE1-silencing transcription factor (REST), occupy SPINK1 promoter and inhibits its transcription. On the other hand, in the absence of AR, lineage reprogramming factor SOX2 in turn binds to SPINK1 promoter leading to its positive transcriptional regulation in androgen-deprived conditions with concomitant increase in neuroendocrine markers. Additionally, stable knockdown of SPINK1 results in reduced epithelial-mesenchymal transition, decreased stemness and drug resistance. Collectively, our findings provide a plausible explanation to the paradoxical clinical outcomes of ADT, arising due to increase in SPINK1 levels. Finally, we emphasize the need to take a well-informed decision prior to ADT and develop alternative therapeutic strategies for castrate-resistant PCa patients.

Citation Format: Ritika Tiwari, Nishat Manzar, Vipul Bhatia, Anjali Yadav, Shannon Carskadon, Nilesh Gupta, Amina Zoubeidi, Nallasivam Palanisamy, Bushra Ateeq. Androgen deprivation upregulates SPINK1 expression and potentiates cellular plasticity in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5225.

Proproliferative function of adaptor protein GRB10 in prostate carcinoma

Growth factor receptor-binding protein 10 (GRB10) is a well-known adaptor protein and a recently identified substrate of the mammalian target of rapamycin (mTOR). Depletion of GRB10 increases insulin sensitivity and overexpression suppresses PI3K/Akt signaling. Because the major reason for the limited efficacy of PI3K/Akt-targeted therapies in prostate cancer (PCa) is loss of mTOR-regulated feedback suppression, it is therefore important to assess the functional importance and regulation of GRB10 under these conditions. On the basis of these background observations, we explored the status and functional impact of GRB10 in PCa and found maximum expression in phosphatase and tensin homolog (PTEN)-deficient PCa. In human PCa samples, GRB10 inversely correlated with PTEN and positively correlated with pAKT levels. Knockdown of GRB10 in nontumorigenic PTEN null mouse embryonic fibroblasts and tumorigenic PCa cell lines reduced Akt phosphorylation and selectively activated a panel of receptor tyrosine kinases. Similarly, overexpression of GRB10 in PTEN wild-type PCa cell lines accelerated tumorigenesis and induced Akt phosphorylation. In PTEN wild-type PCa, GRB10 overexpression promoted mediated PTEN interaction and degradation. PI3K (but not mTOR) inhibitors reduced GRB10 expression, suggesting primarily PI3K-driven regulation of GRB10. In summary, our results suggest that GRB10 acts as a major downstream effector of PI3K and has tumor-promoting effects in prostate cancer.-Khan, M. I., Al Johani, A., Hamid, A., Ateeq, B., Manzar, N., Adhami, V. M., Lall, R. K., Rath, S., Sechi, M., Siddiqui, I. A., Choudhry, H., Zamzami, M. A., Havighurst, T. C., Huang, W., Ntambi, J. M., Mukhtar, H. Proproliferatve function of adaptor protein GRB10 in prostate carcinoma.

Epigenetic Silencing of miRNA-338-5p and miRNA-421 Drives SPINK1-Positive Prostate Cancer

PURPOSE

Serine peptidase inhibitor, Kazal type-1 (SPINK1) overexpression defines the second most recurrent and aggressive prostate cancer subtype. However, the underlying molecular mechanism and pathobiology of SPINK1 in prostate cancer remains largely unknown.

EXPERIMENTAL DESIGN

miRNA prediction tools were employed to examine the SPINK1-3'UTR for miRNA binding. Luciferase reporter assays were performed to confirm the SPINK1-3'UTR binding of shortlisted miR-338-5p/miR-421. Furthermore, miR-338-5p/-421-overexpressing cancer cells (SPINK1-positive) were evaluated for oncogenic properties using cell-based functional assays and a mouse xenograft model. Global gene expression profiling was performed to unravel the biological pathways altered by miR-338-5p/-421. IHC and RNA in situ hybridization were carried out on prostate cancer patients' tissue microarray for SPINK1 and EZH2 expression, respectively. Chromatin immunoprecipitation assay was performed to examine EZH2 occupancy on the miR-338-5p/-421-regulatory regions. Bisulfite sequencing and methylated DNA immunoprecipitation were performed on prostate cancer cell lines and patients' specimens.

RESULTS

We established a critical role of miRNA-338-5p/-421 in posttranscriptional regulation of SPINK1. Ectopic expression of miRNA-338-5p/-421 in SPINK1-positive cells abrogates oncogenic properties including cell-cycle progression, stemness, and drug resistance, and shows reduced tumor burden and distant metastases in a mouse model. Importantly, we show that patients with SPINK1-positive prostate cancer exhibit increased EZH2 expression, suggesting its role in epigenetic silencing of miRNA-338-5p/-421. Furthermore, presence of CpG dinucleotide DNA methylation marks on the regulatory regions of miR-338-5p/-421 in SPINK1-positive prostate cancer cells and patients' specimens confirms epigenetic silencing.

CONCLUSIONS

Our findings revealed that miRNA-338-5p/-421 are epigenetically silenced in SPINK1-positive prostate cancer, although restoring the expression of these miRNAs using epigenetic drugs or synthetic mimics could abrogate SPINK1-mediated oncogenesis.See related commentary by Bjartell, p. 2679.

Mutagenicity and Cytotoxicity of Particulate Matter Emitted from Biodiesel-Fueled Engines

Biodiesel engines produce several intermediate species, which can potentially harm the human health. The concentration of these species and their health risk potential varies depending on engine technology, fuel, and engine operating condition. In this study, experiments were performed on a large number of engines having different configurations (emissions norms/fuel used), which were operated at part load/full load using B20 (20% v/v biodiesel blended with mineral diesel) and mineral diesel. Experiments included measurement of gaseous emissions, and physical, chemical, and biological characterization of exhaust particulate matter (PM). Chemical characterization of PM was carried out for detecting polycyclic aromatic hydrocarbons (PAH's) and PM bound trace metals. The biological toxicity associated with PM was assessed using human embryonic kidney 293T cells (HEK 293T). The mutagenic potential of the PM was tested at three different concentrations (500, 100, and 50 μg/mL) using two different  Salmonella strains, TA98 and TA100, with and without liver S9 metabolic enzyme fraction. PM samples exhibited cytotoxic effect on HEK 293T cells (IC₅₀ < 100 μg/mL) and there was significant potential for reactive oxygen species (ROS) generation. Comparison of different engines showed that modern engines (Euro-III and Euro-IV compliant) produced relatively cleaner exhaust compared to older engines (Euro-II compliant). Biodiesel-fueled engines emitted lower number of particles compared to diesel-fueled engines. However, chemical characterization revealed that biodiesel-fueled engines exhaust PM contained several harmful PAHs and trace metals, which affected the biological activity of these PM, as reflected in the biological investigations. Mutagenicity and cytotoxicity of PM from biodiesel-fueled engines were relatively higher compared to their diesel counterparts, indicating the need for exhaust gas after-treatment.

AKT Inhibition Modulates H3K4 Demethylase Levels in PTEN-Null Prostate Cancer

Hyperactivated AKT kinase due to loss of its negative regulator PTEN influences many aspects of cancer biology, including chromatin. AKT primarily regulates acetyl-CoA production and phosphorylates many histone-modulating enzymes, resulting in their activation or inhibition. Therefore, understanding the therapeutic impact of AKT inhibition on chromatin-related events is essential. Here, we report that AKT inhibition in prostate-specific PTEN knockout mice significantly induces di- and trimethylation of H3K4 with concomitant reduction in H3K9 acetylation. Mechanistically, we observed that AKT inhibition reduces expression of the H3K4 methylation-specific histone demethylases KDM5 family, especially KDM5B expression at transcriptional levels. Furthermore, we observed that AKT negatively regulates miR-137 levels, which transcriptionally represses KDM5B expression. Overexpression of miR-137 significantly reduced KDM5B and increased H3K4 methylation levels but failed to change AKT phosphorylation. Overall, we observed that AKT transcriptionally regulates KDM5B mainly via repression of miR-137. Our data identify a mechanism by which AKT kinase modulates the prostate cancer epigenome through regulating H3K4 methylation. Additional studies on AKT inhibition-mediated induction of H3K4 methylation will help in designing strategies to enhance the therapeutic efficacy of PI3K/AKT inhibitors.

Entropically driven controlled release of paclitaxel from poly(2-ethyl-2-oxazoline) coated maghemite nanostructures for magnetically guided cancer therapy

Theranostic nanostructures serve a dual purpose of therapy and diagnosis. A major fraction of these are based on polymer coated magnetic nanostructures of iron oxides (magnetite and maghemite), owing to the efficient drug loading capacity of polymer shells and enhanced magnetic contrast effects of the iron oxide core. In the current work we are proposing poly(2-ethyl-2-oxazoline) coated linear thermoresponsive nanostructures of maghemite (γ-Fe₂O₃) for potential application in targeted cancer therapy. The polymer coating was obtained via a modified sol-gel technique based on entropically driven phase separation of poly(2-ethyl-2-oxazoline) above its cloud point (CP) temperature of 63 °C in water. The developed nanostructures were further loaded with paclitaxel, a polar anticancer compound at room temperature (25 °C). The entropically driven release of paclitaxel at various concentrations and physiological temperatures was modeled and their application to the PC3 prostrate cancer cell line was investigated by treating in vitro. The steering efficiency of the magnetic nanostructures during their navigation through large blood vessels was also analyzed with the help of a synthetic model of the human axillary artery. The proposed application of these newly developed nanostructures can easily be extended towards localized delivery of additional polar anticancer drugs like cisplatin and doxorubicin.

Abstract A060: Repression of microRNA-338/421 by EZH2 represents a novel mechanism for SPINK1-positive prostate cancers

Prostate cancer (PCa) is a clinically heterogeneous disease marked by variability in patient prognosis. The intratumoral and interpatient heterogeneity formed the basis of molecular stratification of the disease. Overexpression of Serine Peptidase Inhibitor, Kazal type-1 (SPINK1), was found to be the second most recurrent (~10-15%) PCa subtype, after highly recurrent (~50%) androgen-driven TMPRSS2-ERG genetic rearrangement. Unlike amplification of ERBB2 in breast cancer, SPINK1 overexpression has not been associated with gene amplification or rearrangement. Nonetheless, molecular mechanism underlying its upregulation in cancer is poorly understood and remains a matter of conjecture.

Using in silico microRNA prediction tools, we shortlisted three miRNAs, of which miR-338-5p and miR-421 revealed an inverse correlation with SPINK1 in The Cancer Genome Atlas (TCGA) prostate adenocarcinoma RNA-Seq dataset (n=106), which was validated in our PCa specimens (n=20). Here, we showed that miR-338-5p and miR-421 post-transcriptionally regulate SPINK1 by binding to its 3′ UTR. We established that miR-338-5p and miR-421 mediate several cellular responses against SPINK1-positive cancer by inducing S-phase cell-cycle arrest, inhibiting epithelial-to-mesenchymal transition (EMT), cancer stemness, and drug resistance. Moreover, ectopic expression of miR-338-5p and miR-421 abrogates SPINK1-mediated oncogenesis, tumor growth, and distant metastases in murine xenograft model. Further, mechanistically we demonstrate that Polycomb group protein enhancer of zeste homolog 2 (EZH2) mediates epigenetic silencing by establishing histone H3K27me3 repressive marks and DNA methylation, 5’ methyl cytosine (5mC) marks on the promoters of miR-338-5p and miR-421 in SPINK1-positive subtype. Thus, restoring miR-338-5p and miR-421 expression using either epigenetic drugs or synthetic mimics could abrogate SPINK1-mediated oncogenesis by targeting multiple oncogenic pathways and eliciting anticancer pleiotropic effects.

Taken together, the present study for the first time unravels the molecular mechanism underlying SPINK1 overexpression and thereby opens up new avenues for the use of miR-338-5p and miR-421 replacement therapy for the treatment of SPINK1-positive malignancies.

Citation Format: Vipul Bhatia, Anjali Yadav, Ritika Tiwari, Shivansh Nigam, Apul Goel, Bushra Ateeq. Repression of microRNA-338/421 by EZH2 represents a novel mechanism for SPINK1-positive prostate cancers [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr A060.

Abstract A065: MicroRNA-338-5p/-421 mediated regulation of oncogenic long noncoding RNA MALAT1 abrogates prostate cancer progression and metastases

Prostate cancer (PCa) is one of the leading cause of cancer-associated death among men worldwide. Understanding the mechanism underpinning the disease pathogenesis is therefore critical in developing novel therapeutic strategies for this disease. Multiple lines of evidence suggest that noncoding RNAs (ncRNAs), including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), are implicated in PCa progression and metastases. To date, great efforts have been put forth to characterize the role of miRNAs in regulating the expression of coding transcripts. However, little is known about the influence of miRNAs on the expression of noncoding transcripts such as lncRNAs. Thus, elucidating the role of miRNAs in modulating the expression of lncRNAs in PCa is crucial in order to understand their functional significance and potential utility for therapeutic interventions.

Previously, we demonstrated that miR-338-5p and miR-421 exhibit tumor-suppressive properties in prostate cancer by inducing S-phase arrest, inhibiting epithelial-to-mesenchymal transition (EMT) and cancer stemness (unpublished data). Moreover, ectopic expression of these miRNAs abrogated tumor growth and distant metastases in murine xenograft model. Further, to gain insights into the biologic functions altered by miR-338-5p and miR-421, we performed global gene expression profiling of 22RV1 cells overexpressing these miRNAs. Our analysis revealed several lncRNAs deregulated by these miRNAs. One of the lncRNA found to be downregulated upon overexpression of miR-338-5p/miR-421was an oncogenic lncRNA, Metastasis Associated Lung Adenocarcinoma Transcript 1 (MALAT1), which is known to be profoundly upregulated across many cancers including prostate. Moreover, in silico miRNA prediction tools indicated putative binding sites of miR-338-5p and miR-421 on the 3’ end of MALAT1. The binding of miR-338-5p and miR-421 on MALAT1 was further confirmed by luciferase reporter assay, indicating miRNA-mediated post-transcriptional regulation. Furthermore, analysis of RNA-seq data from The Cancer Genome Atlas for prostate adenocarcinoma (TCGA-PRAD) revealed an inverse correlation of miR-338-5p/miR-421 with MALAT1 expression in PCa patients, which in turn confirms the notion that these miRNAs suppress the expression of onco-lncRNA MALAT1.

Taken together, our findings indicate that oncogenic lncRNA, MALAT1 is a target of tumor suppressor miRNAs, miR-338-5p/miR-421. More importantly, we elucidated a novel miRNA-lncRNA regulatory network that is miR-338-5p/miR-421-MALAT1 axis in PCa pathogenesis and a potential therapeutic strategy for PCa patients.

Citation Format: Anjali Yadav, Vipul Bhatia, Ritika Tiwari, Shivansh Nigam, Apul Goel, Bushra Ateeq. MicroRNA-338-5p/-421 mediated regulation of oncogenic long noncoding RNA MALAT1 abrogates prostate cancer progression and metastases [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr A065.

Toxicity and mutagenicity of exhaust from compressed natural gas: Could this be a clean solution for megacities with mixed-traffic conditions?

Despite intensive research carried out on particulates, correlation between engine-out particulate emissions and adverse health effects is not well understood yet. Particulate emissions hold enormous significance for mega-cities like Delhi that have immense traffic diversity. Entire public transportation system involving taxis, three-wheelers, and buses has been switched from conventional liquid fuels to compressed natural gas (CNG) in the Mega-city of Delhi. In this study, the particulate characterization was carried out on variety of engines including three diesel engines complying with Euro-II, Euro-III and Euro-IV emission norms, one Euro-II gasoline engine and one Euro-IV CNG engine. Physical, chemical and biological characterizations of particulates were performed to assess the particulate toxicity. The mutagenic potential of particulate samples was investigated at different concentrations using two different Salmonella strains, TA98 and TA100 in presence and absence of liver S9 metabolic enzyme fraction. Particulates emitted from diesel and gasoline engines showed higher mutagenicity, while those from CNG engine showed negligible mutagenicity compared to other test fuels and engine configurations. Polycyclic aromatic hydrocarbons (PAHs) adsorbed onto CNG engine particulates were also relatively fewer compared to those from equivalent diesel and gasoline engines. Taken together, our findings indicate that CNG is comparatively safer fuel compared to diesel and gasoline and can offer a cleaner transport energy solution for mega-cities with mixed-traffic conditions, especially in developing countries.

Association of AGTR1 (A1166C) and ACE (I/D) Polymorphisms with Breast Cancer Risk in North Indian Population

Renin angiotensin system (RAS) comprising Angiotensin converting enzyme (ACE), Angiotensin II (Ang II) and its receptor Angiotensin II receptor type I (AGTR1), plays a critical role in several diseases including cancer. A single nucleotide polymorphism (SNP) A1166C located in 3' untranslated region (UTR) of AGTR1 and an insertion/deletion (I/D) polymorphism present in intron 16 of ACE gene have been associated with many diseases, but their association with Breast cancer (BCa) is still debatable. Here, we for the first time investigated the association of these polymorphisms in a North Indian BCa cohort including 161 patients and 152 healthy women. The polymorphisms were evaluated by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) respectively. The association between these polymorphisms and BCa risk was estimated by calculating Odds Ratio (OR) and chi-square (χ2) test. The DD genotype/D allele of ACE (I/D) polymorphism and "AC and CC" genotype/C allele of AGTR1 (A1166C) polymorphism were associated with higher risk of BCa when evaluated independently. Furthermore, interaction analysis of "AC and CC" and DD genotype and combination of "C and D" alleles of both polymorphisms revealed significantly greater BCa risk than that observed independently. Conclusively, women harboring "AC or CC" genotype/C allele for AGTR1 (A1166C) polymorphism and DD genotype/D allele for ACE (I/D) polymorphisms have a predisposition to develop more aggressive disease with advanced staging and larger tumor size. Our study indicates importance of genetic screening based on these polymorphisms for women, who may have higher risk of BCa.

Direct Intranuclear Anticancer Drug Delivery via Polydimethylsiloxane Nanoparticles: in Vitro and in Vivo Xenograft Studies

Direct delivery of anticancer drugs to nuclei of tumor cells is required to enhance the therapeutic activity, which can be achieved by a nuclear localization signal (NLS) or peptide-decorated nanovehicles. However, NLS/peptide-based approaches may create certain undesirable immunological responses and the utilized synthesis processes are generally labor intensive. To this end, we report ligand-free, enhanced intranuclear delivery of Doxorubicin (Dox) to different cancer cells via porous polydimethylsiloxane (PDMS) nanoparticles (NPs). PDMS NPs were prepared by sacrificial silica template-based approach and Dox was loaded into the pores of PDMS NPs. These Dox-loaded PDMS NPs show enhanced cytotoxicity and reduce the IC50 values by 84 and 54% for HeLa and PC-3, respectively, compared to free Dox. Further, DNA damage in HeLa cells was estimated using comet assay suggesting enhanced DNA damage (72%) with Dox-loaded PDMS NPs as compared to free Dox (12%). The therapeutic efficiency of PDMS-Dox drug delivery system was tested in prostate cancer (PC-3) xenografts in NOD/SCID mice which showed enhanced tumor reduction (∼66%) as compared to free Dox. Taken together, our PDMS-Dox delivery system shows efficient and enhanced transportation of Dox to tumor cells which can be harnessed to develop advanced chemotherapy-based approaches to treat prostate and other cancers.

Development of Peptidomimetic Inhibitors of the ERG Gene Fusion Product in Prostate Cancer

Transcription factors play a key role in the development of diverse cancers, and therapeutically targeting them has remained a challenge. In prostate cancer, the gene encoding the transcription factor ERG is recurrently rearranged and plays a critical role in prostate oncogenesis. Here, we identified a series of peptides that interact specifically with the DNA binding domain of ERG. ERG inhibitory peptides (EIPs) and derived peptidomimetics bound ERG with high affinity and specificity, leading to proteolytic degradation of the ERG protein. The EIPs attenuated ERG-mediated transcription, chromatin recruitment, protein-protein interactions, cell invasion and proliferation, and tumor growth. Thus, peptidomimetic targeting of transcription factor fusion products may provide a promising therapeutic strategy for prostate cancer as well as other malignancies.

Targeting NF-kappa B Signaling by Artesunate Restores Sensitivity of Castrate-Resistant Prostate Cancer Cells to Antiandrogens

Androgen deprivation therapy (ADT) is the most preferred treatment for men with metastatic prostate cancer (PCa). However, the disease eventually progresses and develops resistance to ADT in majority of the patients, leading to the emergence of metastatic castration-resistant prostate cancer (mCRPC). Here, we assessed artesunate (AS), an artemisinin derivative, for its anticancer properties and ability to alleviate resistance to androgen receptor (AR) antagonists. We have shown AS in combination with bicalutamide (Bic) attenuates the oncogenic properties of the castrate-resistant (PC3, 22RV1) and androgen-responsive (LNCaP) PCa cells. Mechanistically, AS and Bic combination inhibits nuclear factor (NF)-κB signaling and decreases AR and/or AR-variant 7 expression via ubiquitin-mediated proteasomal degradation. The combination induces oxidative stress and apoptosis via survivin downregulation and caspase-3 activation, resulting in poly-ADP-ribose polymerase (PARP) cleavage. Moreover, preclinical castrate-resistant PC3 xenograft studies in NOD/SCID mice (n =28, seven per group) show remarkable tumor regression and significant reduction in lungs and bone metastases upon administering AS (50 mg/kg per day in two divided doses) and Bic (50 mg/kg per day) via oral gavage. Taken together, we for the first time provide a compelling preclinical rationale that AS could disrupt AR antagonist-mediated resistance observed in mCRPC. The current study also indicates that the therapeutic combination of Food and Drug Administration-approved AS or NF-κB inhibitors and AR antagonists may enhance the clinical efficacy in the treatment of mCRPC patients.

Molecular Discriminators of Racial Disparities in Prostate Cancer

Recent molecular characterization of prostate cancer (PCa) identified novel genetic aberrations and disease subtypes. The frequencies of molecular aberrations show racial disparity. Clinical strategies and targeted therapies embracing these racial differences are required. Here we discuss ethnic differences in genetic alterations and their impact on the susceptibility, progression, and treatment of prostate cancer.

Molecular profiling of ETS and non-ETS aberrations in prostate cancer patients from northern India

BACKGROUND

Molecular stratification of prostate cancer (PCa) based on genetic aberrations including ETS or RAF gene-rearrangements, PTEN deletion, and SPINK1 over-expression show clear prognostic and diagnostic utility. Gene rearrangements involving ETS transcription factors are frequent pathogenetic somatic events observed in PCa. Incidence of ETS rearrangements in Caucasian PCa patients has been reported, however, occurrence in Indian population is largely unknown. The aim of this study was to determine the prevalence of the ETS and RAF kinase gene rearrangements, SPINK1 over-expression, and PTEN deletion in this cohort.

METHODS

In this multi-center study, formalin-fixed paraffin embedded (FFPE) PCa specimens (n = 121) were procured from four major medical institutions in India. The tissues were sectioned and molecular profiling was done using immunohistochemistry (IHC), RNA in situ hybridization (RNA-ISH) and/or fluorescence in situ hybridization (FISH).

RESULTS

ERG over-expression was detected in 48.9% (46/94) PCa specimens by IHC, which was confirmed in a subset of cases by FISH. Among other ETS family members, while ETV1 transcript was detected in one case by RNA-ISH, no alteration in ETV4 was observed. SPINK1 over-expression was observed in 12.5% (12/96) and PTEN deletion in 21.52% (17/79) of the total PCa cases. Interestingly, PTEN deletion was found in 30% of the ERG-positive cases (P = 0.017) but in only one case with SPINK1 over-expression (P = 0.67). BRAF and RAF1 gene rearrangements were detected in ∼1% and ∼4.5% of the PCa cases, respectively.

CONCLUSIONS

This is the first report on comprehensive molecular profiling of the major spectrum of the causal aberrations in Indian men with PCa. Our findings suggest that ETS gene rearrangement and SPINK1 over-expression patterns in North Indian population largely resembled those observed in Caucasian population but differed from Japanese and Chinese PCa patients. The molecular profiling data presented in this study could help in clinical decision-making for the pursuit of surgery, diagnosis, and in selection of therapeutic intervention.

Role and therapeutic potential of G-protein coupled receptors in breast cancer progression and metastases

G-protein-coupled receptors (GPCRs) comprise a large family of cell-surface receptors, which have recently emerged as key players in tumorigenesis, angiogenesis and metastasis. In this review, we discussed our current understanding of the many roles played by GPCRs in general, and particularly Angiotensin II type I receptor (AGTR1), a member of the seven-transmembrane-spanning G-protein coupled receptor superfamily, and its significance in breast cancer progression and metastasis. We have also discussed different strategies for targeting AGTR1, and its ligand Angiotension II (Ang II), which might unravel unique opportunities for breast cancer prevention and treatment. For example, AGTR1 blockers (ARBs) which are already in clinical use for treating hypertension, merit further investigation as a therapeutic strategy for AGTR1-positive cancer patients and may have the potential to prevent Ang II-AGTR1 signalling mediated cancer pathogenesis and metastases.

Abstract 5348: Characterization of the EZH2-MMSET histone methyltransferase regulatory axis in cancer

Histone methyltransferases (HMTases), as chromatin modifiers, regulate the transcriptomic landscape in normal development as well in diseases such as cancer. Here, we molecularly order two HMTases, EZH2 and MMSET that have established genetic links to oncogenesis. EZH2, which mediates histone H3K27 trimethylation and is associated with gene silencing, was shown to be coordinately expressed and function upstream of MMSET, which mediates H3K36 dimethylation and is associated with active transcription. EZH2 transcript expression levels were compared to all HMTases (n=51) in our compendium of RNA-seq data comprising 474 malignant and benign samples, representing 14 different tissue types. MMSET displayed the strongest correlation with EZH2 expression. Similarly, a meta-analysis of 1755 samples from 22 published microarray gene expression studies in Oncomine revealed co-expression of MMSET and EZH2 in 15 different cancers. We found that the EZH2-MMSET HMTase axis is coordinated by a microRNA network and that the oncogenic functions of EZH2 require MMSET activity. Together, these results suggest that the EZH2-MMSET HMTase axis coordinately functions as a master regulator of transcriptional repression, activation, and oncogenesis and may represent an attractive therapeutic target in cancer.

Citation Format: Irfan A. Asangani, Bushra Ateeq, Qi Cao, Lois Dodson, Mithil Pandhi, Lakshmi P. Kunju, Rohit Mehra, Robert J. Lonigro, Javed Siddiqui, Nallasivam Palanisamy, Yi-Mi Wu, Xuhong Cao, Jung H. Kim, Mathew K. Iyer, Christopher A. Maher, Chandan Kumar-Sinha, Sooryanarayana Varambally, Arul M. Chinnaiyan, Meng Zhao, Zhaohui S. Qin. Characterization of the EZH2-MMSET histone methyltransferase regulatory axis in cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5348. doi:10.1158/1538-7445.AM2013-5348

Identification of targetable FGFR gene fusions in diverse cancers

Through a prospective clinical sequencing program for advanced cancers, four index cases were identified which harbor gene rearrangements of FGFR2, including patients with cholangiocarcinoma, breast cancer, and prostate cancer. After extending our assessment of FGFR rearrangements across multiple tumor cohorts, we identified additional FGFR fusions with intact kinase domains in lung squamous cell cancer, bladder cancer, thyroid cancer, oral cancer, glioblastoma, and head and neck squamous cell cancer. All FGFR fusion partners tested exhibit oligomerization capability, suggesting a shared mode of kinase activation. Overexpression of FGFR fusion proteins induced cell proliferation. Two bladder cancer cell lines that harbor FGFR3 fusion proteins exhibited enhanced susceptibility to pharmacologic inhibition in vitro and in vivo. Because of the combinatorial possibilities of FGFR family fusion to a variety of oligomerization partners, clinical sequencing efforts, which incorporate transcriptome analysis for gene fusions, are poised to identify rare, targetable FGFR fusions across diverse cancer types.

Characterization of the EZH2-MMSET histone methyltransferase regulatory axis in cancer

Histone methyltransferases (HMTases), as chromatin modifiers, regulate the transcriptomic landscape in normal development as well in diseases such as cancer. Here, we molecularly order two HMTases, EZH2 and MMSET, that have established genetic links to oncogenesis. EZH2, which mediates histone H3K27 trimethylation and is associated with gene silencing, was shown to be coordinately expressed and function upstream of MMSET, which mediates H3K36 dimethylation and is associated with active transcription. We found that the EZH2-MMSET HMTase axis is coordinated by a microRNA network and that the oncogenic functions of EZH2 require MMSET activity. Together, these results suggest that the EZH2-MMSET HMTase axis coordinately functions as a master regulator of transcriptional repression, activation, and oncogenesis and may represent an attractive therapeutic target in cancer.

Role of dutasteride in pre-clinical ETS fusion-positive prostate cancer models

BACKGROUND

Androgens play a crucial role in prostate cancer, hence the androgenic pathway has become an important target of therapeutic intervention. Previously we discovered that gene fusions between the 5'-untranslated region of androgen regulated gene TMPRSS2 and the ETS transcription factor family members were present in a majority of the prostate cancer cases. The resulting aberrant overexpression of ETS genes drives tumor progression.

METHODS

Here, we evaluated the expression levels of 5α-reductase isoenzymes in prostate cancer cell lines and tissues. We tested the effect of dutasteride, a 5α-reductase inhibitor, in TMPRSS2-ERG fusion-positive VCaP cell proliferation and cell invasion. We also evaluated the effect of dutasteride on the TMPRSS2-ERG fusion gene expression. Finally, we tested dutasteride alone or in combination with an anti-androgen in VCaP cell xenografts tumor model.

RESULTS

Our data showed that 5α-reductase SRD5A1 and SRD5A3 isoenzymes that are responsible for the conversion of testosterone to DHT, are highly expressed in metastatic prostate cancer compared to benign and localized prostate cancer. Dutasteride treatment attenuated VCaP cell proliferation and invasion. VCaP cells pre-treated with dutasteride showed a reduction in ERG and PSA expression. In vivo studies demonstrated that dutasteride in combination with the anti-androgen bicalutamide significantly decreased tumor burden in VCaP cell xenograft model.

CONCLUSIONS

Our findings suggest that dutasteride can inhibit ERG fusion-positive cell growth and in combination with anti-androgen, significantly reduce the tumor burden. Our study suggests that anti-androgens used in combination with dutasteride could synergistically augment the therapeutic efficacy in the treatment of ETS-positive prostate cancer.

Functionally recurrent rearrangements of the MAST kinase and Notch gene families in breast cancer

Breast cancer is a heterogeneous disease, exhibiting a wide range of molecular aberrations and clinical outcomes. Here we employed paired-end transcriptome sequencing to explore the landscape of gene fusions in a panel of breast cancer cell lines and tissues. We observed that individual breast cancers harbor an array of expressed gene fusions. We identified two classes of recurrent gene rearrangements involving microtubule associated serine-threonine kinase (MAST) and Notch family genes. Both MAST and Notch family gene fusions exerted significant phenotypic effects in breast epithelial cells. Breast cancer lines harboring Notch gene rearrangements are uniquely sensitive to inhibition of Notch signaling, and over-expression of MAST1 or MAST2 gene fusions had a proliferative effect both in vitro and in vivo. These findings illustrate that recurrent gene rearrangements play significant roles in subsets of carcinomas and suggest that transcriptome sequencing may serve to identify patients with rare, actionable gene fusions.

Coordinated regulation of polycomb group complexes through microRNAs in cancer

Polycomb Repressive Complexes (PRC1 and PRC2)-mediated epigenetic regulation is critical for maintaining cellular homeostasis. Members of Polycomb Group (PcG) proteins including EZH2, a PRC2 component, are upregulated in various cancer types, implicating their role in tumorigenesis. Here, we have identified several microRNAs (miRNAs) that are repressed by EZH2. These miRNAs, in turn, regulate the expression of PRC1 proteins BMI1 and RING2. We found that ectopic overexpression of EZH2-regulated miRNAs attenuated cancer cell growth and invasiveness, and abrogated cancer stem cell properties. Importantly, expression analysis revealed an inverse correlation between miRNA and PRC protein levels in cell culture and prostate cancer tissues. Taken together, our data have uncovered a coordinate regulation of PRC1 and PRC2 activities that is mediated by miRNAs.