Metastatic Prostate Cancer Cell Lines Research Articles

CYB561 supports the neuroendocrine phenotype in castration-resistant prostate cancer.

Castration-resistant prostate cancer (CRPC) is associated with resistance to androgen deprivation therapy, and an increase in the population of neuroendocrine (NE) differentiated cells. It is hypothesized that NE differentiated cells secrete neuropeptides that support androgen-independent tumor growth and induce aggressiveness of adjacent proliferating tumor cells through a paracrine mechanism. The cytochrome b561 (CYB561) gene, which codes for a secretory vesicle transmembrane protein, is constitutively expressed in NE cells and highly expressed in CRPC. CYB561 is involved in the α-amidation-dependent activation of neuropeptides, and contributes to regulating iron metabolism which is often dysregulated in cancer. These findings led us to hypothesize that CYB561 may be a key player in the NE differentiation process that drives the progression and maintenance of the highly aggressive NE phenotype in CRPC. In our study, we found that CYB561 expression is upregulated in metastatic and NE prostate cancer (NEPC) tumors and cell lines compared to normal prostate epithelia, and that its expression is independent of androgen regulation. Knockdown of CYB561 in androgen-deprived LNCaP cells dampened NE differentiation potential and transdifferentiation-induced increase in iron levels. In NEPC PC-3 cells, depletion of CYB561 reduced the secretion of growth-promoting factors, lowered intracellular ferrous iron concentration, and mitigated the highly aggressive nature of these cells in complementary assays for cancer hallmarks. These findings demonstrate the role of CYB561 in facilitating transdifferentiation and maintenance of NE phenotype in CRPC through its involvement in neuropeptide biosynthesis and iron metabolism pathways.

Dickkopf-1 (DKK1) drives growth and metastases in castration-resistant prostate cancer.

Metastatic castration-resistant prostate cancer (mCRPC) is associated with a poor prognosis and remains an incurable fatal disease. Therefore, the identification of molecular markers involved in cancer progression is urgently needed to develop more-effective therapies. The present study investigated the role of the Wnt signaling modulator Dickkopf-1 (DKK1) in the growth and metastatic progression of mCRPC. DKK1 silencing through siRNA and deletion via CRISPR/Cas9 editing were performed in two different metastatic castration-resistant prostate cancer cell lines (PC3 and DU145). A xenograft tumor model was used to assess tumor growth and metastases. In in vitro experiments, both DKK1 silencing and deletion reduced cell growth and migration of both cell lines. DKK1 knockout clones (DKK1-KO) exhibited cell cycle arrest, tubulin reorganization, and modulation of tumor metastasis-associated genes. Furthermore, in DKK1-KO cells, E-cadherin re-expression and its membrane co-localization with β-catenin were observed, contributing to reduced migration; Cadherin-11, known to increase during epithelial-mesenchymal transition, was down-regulated in DKK1-KO cells. In the xenograft mouse model, DKK1 deletion not only reduced tumor growth but also inhibited the formation of lung metastases. In conclusion, our findings support the key role of DKK1 in the growth and metastatic dissemination of mCRPC, both in vitro and in vivo.

Abstract 2036: Characterizing PARP inhibitor and next-generation anti-androgen therapy responses in advanced prostate cancer

Abstract PARP inhibitors (PARPi) have been shown to be effective in prostate cancer patients with certain DNA repair defects, thus ushering in the era of precision medicine for this disease. Despite this advance, barriers remain which impede further progress including an incomplete understanding of therapeutic response. Our previous and on-going work shows that PARP inhibition leads to both cell death and a more cytostatic, senescence-like arrest. We hypothesize that persistent cells may later promote progression and treatment resistance. Recent clinical trials such as PROpel and TALAPRO-2 have demonstrated success in combining PARPi’s with next-generation anti-androgen therapies (NGAT) including abiraterone and enzalutamide. Whether NGAT’s are synthetic lethal and cell death promoting with PARP inhibition is poorly understood. Additionally, given the evolving clinical landscape for prostate cancer, it is important to test whether prior NGAT exposure may preclude response to combination therapy. In this study, we sought to characterize these combinations to better understand tumor cell response to treatment and the placement of treatment within the overall therapeutic paradigm. We’ve previously used the C4-2B metastatic castration-resistant prostate cancer cell line as a model which responds well to PARP inhibition. Here, we additionally utilize the C4-2B-derived enzalutamide and abiraterone resistant lines MDVR and AbiR, respectively. The combination of olaparib with abiraterone (recently approved from results of PROpel) was significantly more efficacious than either monotherapy in all three models. Additionally, combination of talazoparib and enzalutamide (approved from results of TALAPRO-2) was also more effective than monotherapy. These data suggest that prior development of NGAT resistance does not prevent benefit from NGAT and PARPi combinations. Although both combinations were found to cause significantly less cell growth, cells appeared more cytostatic rather than apoptotic, suggesting NGAT’s do not induce significant synthetic lethality with PARPi’s. Our work suggests that combining a PARPi with an NGAT promotes a persistent cytostasis which may give rise to eventual tumor progression and the development of resistance. Future studies are directed at further characterizing combinations with PARPi’s and the development of novel strategies to enhance their efficacy. Citation Format: Love A. Moore, Bryan Correa Gonzalez, Allen C. Gao, Alan P. Lombard. Characterizing PARP inhibitor and next-generation anti-androgen therapy responses in advanced prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2036.

Abstract 7200: Non-cytotoxic inhibition of nuclear encoded mitochondrial protein MAGMAS resensitize treatment resistant prostate cancer cells to taxane therapy

Abstract Metastatic prostate cancer (PCa) is the leading cause of PCa-associated deaths and one of the leading causes of cancer mortality in men. Novel therapeutics, such as Prostate Specific Membrane Antigen (PSMA) ligand therapy, are emerging as effective treatment strategies for metastatic prostate cancer. However, most men succumb to Metastatic Castration Resistant Prostate Cancer (mCRPC) due to treatment resistance. MAGMAS, a 13.8 kDa mitochondrial protein, imports nuclear-encoded mitochondrial proteins into the mitochondrial matrix. MAGMAS is overexpressed in several aggressive tumors, such as breast cancer, glioblastoma, and prostate cancer. When overexpressed, MAGMAS plays a role as a cytoprotective protein by acting as a reactive oxygen species (ROS) scavenger that maintains sufficient ROS levels to promote cell proliferation but below the threshold levels that could lead to apoptosis. This study was designed to investigate the pro-survival and therapy-resistance functions of MAGMAS in treatment-resistant PCa cells. Predictively, we observed that the docetaxel (DTX)-resistant PC3-DR and DU145-DR PCa cell lines expressed significantly higher levels of MAGMAS compared to their drug-sensitive parental cell lines. We hypothesized that inhibiting Magmas reduces the aggressive properties of highly proliferative DTX-resistant metastatic PCa cell lines and re-sensitizes them to DTX. MAGMAS knockdown in DTX-resistant PC3 and DU145 cells in the presence of increasing DTX treatments enhanced sensitivity to DTX. Consistent with these results, pharmacological inhibition of MAGMAS with the novel BT#9 inhibitor in combination with increasing DTX concentrations also enhanced sensitivity to DTX in these cell lines. Additional studies using cell migration/invasion assays and tumor-sphere formation assays are underway to further establish MAGMAS as a potential therapeutic target to attenuate the aggressive properties of chemo-resistant PCa cells. Lastly, we will investigate the diagnostic potential of MAGMAS as a biomarker for advanced PCa and BT#9 as an imaging/therapeutic-specific agent for treatment-resistant tumors. Citation Format: Alfonso Duran, Kristen Whitley, Krystal Santiago, Adil Mohammed, Carlos Casiano, Bhaskar Das, Frankis Almaguel. Non-cytotoxic inhibition of nuclear encoded mitochondrial protein MAGMAS resensitize treatment resistant prostate cancer cells to taxane therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7200.

Tramadol and/or Ketamine Repurposing as Potential Anticancer Drugs in Metastatic Castration-Resistant Prostate Cancer Cell Lines

Tramadol and/or Ketamine Repurposing as Potential Anticancer Drugs in Metastatic Castration-Resistant Prostate Cancer Cell Lines

Radiotherapy Metastatic Prostate Cancer Cell Lines Treated with Gold Nanorods Modulate miRNA Signatures.

MicroRNA (miRNA) modulation has been identified as a promising strategy for improving the response of human prostate cancer (PCa) to radiotherapy (RT). Studies have shown that mimics or inhibitors of miRNAs could modulate the sensitivity of PCa cells to RT. In addition, pegylated gold nanoparticles have been studied as a therapeutic approach to treat PCa cells and/or vehicles for carrying miRNAs to the inside of cells. Therefore, we evaluated the capacity of hypofractionated RT and pegylated gold nanorods (AuNPr-PEG) to modulate the miRNA signature on PCa cells. Thus, RT-qPCR was used to analyze miRNA-95, miRNA-106-5p, miRNA-145-5p, and miRNA-541-3p on three human metastatic prostate cell lines (PC3, DU145, and LNCaP) and one human prostate epithelial cell line (HprEpiC, a non-tumor cell line) with and without treatment. Our results showed that miRNA expression levels depend on cell type and the treatment combination applied using RT and AuNPr-PEG. In addition, cells pre-treated with AuNPr-PEG and submitted to 2.5 Gy per day for 3 days decreased the expression levels of miRNA-95, miRNA-106, miRNA-145, and miRNA-541-3p. In conclusion, PCa patients submitted to hypofractionated RT could receive personalized treatment based on their metastatic cellular miRNA signature, and AuNPr-PEG could be used to increase metastatic cell radiosensitivity.

MiR-410 Is a Key Regulator of Epithelial-to-Mesenchymal Transition with Biphasic Role in Prostate Cancer.

The molecular basis of prostate cancer (PCa) progression from the primary disease to metastatic castration-resistant prostate cancer (CRPC) followed by therapy-induced neuroendocrine prostate cancer is not fully understood. In this study, we elucidate the role of miR-410, a little-studied microRNA located on chromosome 14q32.31 within the DLK1-DIO3 cluster, in PCa. miR-410 expression analyses in primary and metastatic PCa tissues and cell lines show that its levels are decreased in initial stages and increased in advanced PCa. Functional studies were performed in a series of PCa cell lines. In LNCaP cells, miR-410 overexpression led to decreases in cellular viability, proliferation, invasiveness, and migration. On the other hand, miR-410 overexpression in PC3 and C42B cells led to increased viability, proliferation, and invasiveness. Our data suggest that miR-410 represses epithelial-to-mesenchymal transition (EMT) in LNCaP cells by directly repressing SNAIL. However, it promotes EMT and upregulates PI3K/Akt signaling in PC3 and C42B cells. In vivo studies with PC3 xenografts support an oncogenic role of miR-410. These data suggest that miR-410 acts as a tumor suppressor in the initial stages of PCa and play an oncogenic role in advanced PCa. Our findings have important implications in understanding the molecular basis of PCa progression with potential translational implications.

Photoactivation of pheophorbide-a utilizing 670 nm LEDs elicits cancer suppressive effects in androgen-independent prostate cancer cellular models.

Prostate cancer (PCa) is the most commonly diagnosed cancer and the second leading cause of cancer death in men in the USA. Photodynamic therapy (PDT) is a state-of-the-art treatment that combines high selectivity with minor side effects. Pheophorbide-a (Pheo) is a natural pigment with a photosensitizer property. Our study delved into the impact of Pheo alone or Pheo-PDT combination on the androgen-independent metastatic prostate cancer (AIPC) cell lines DU-145 and C4-2. Furthermore, an in-depth examination has been conducted on the photocytotoxicity mechanism of Pheo-PDT in these specific cell lines. In vitro studies were conducted using the AIPC cell lines. DU-145 and C4-2 cells were treated with Pheo at different concentrations for 60 min alone, or Pheo treatment followed by exposure to 670 nm illumination (60 mW/cm2 in 88 s pulses), producing 5 J/cm2 via portable light-emitting diode. Our results show that Pheo-PDT substantially inhibits cell viability, anchorage-independent growth, and migration capacities and induces autophagy and apoptosis via the over-production of reactive oxygen species that mediates endoplasmic reticulum stress in AIPC cell lines. Our study highlights the potential benefits of Pheo-PDT in metastatic hormone-insensitive PCa cell lines. It paves the way for treating localized and locally advanced PCa as a possible candidate for castration-resistant prostate cancer.

Functional In Vivo Screening Identifies microRNAs Regulating Metastatic Dissemination of Prostate Cancer Cells to Bone Marrow.

Distant metastasis is the major cause of cancer-related deaths in men with prostate cancer (PCa). An in vivo functional screen was used to identify microRNAs (miRNAs) regulating metastatic dissemination of PCa cells. PC3 cells transduced with pooled miRZiP™ lentivirus library (anti-miRNAs) were injected intraprostatic to 13 NSG mice followed by targeted barcode/anti-miR sequencing. PCa cells in the primary tumours showed a homogenous pattern of anti-miRNAs, but different anti-miRNAs were enriched in liver, lung, and bone marrow, with anti-miR-379 highly enriched in the latter. The bone metastasis-promoting phenotype induced by decreased miR-379 levels was also confirmed in a less metastatic PCa cell line, 22Rv1, where all mice injected intracardially with anti-miR-379-22Rv1 cells developed bone metastases. The levels of miR-379 were found to be lower in bone metastases compared to primary tumours and non-cancerous prostatic tissue in a patient cohort. In vitro functional studies suggested that the mechanism of action was that reduced levels of miR-379 gave an increased colony formation capacity in conditions mimicking the bone microenvironment. In conclusion, our data suggest that specific miRNAs affect the establishment of primary tumours and metastatic dissemination, with a loss of miR-379 promoting metastases in bone.

Characterisation of cell lines derived from prostate cancer patients with localised disease.

Prostate cancer is a broad-spectrum disease, spanning from indolent to a highly aggressive lethal malignancy. Prostate cancer cell lines are essential tools to understanding the basic features of this malignancy, as well as in identifying novel therapeutic strategies. However, most cell lines routinely used in prostate cancer research are derived from metastatic disease and may not fully elucidate the molecular events underlying the early stages of cancer development and progression. Thus, there is a need for new cell lines derived from localised disease to better span the disease spectrum. Prostatic tissue from the primary site, and adjacent non-cancerous tissue was obtained from four patients with localised disease undergoing radical prostatectomy. Epithelial cell outgrowths were immortalised with human papillomavirus type 16 (HPV16) E6 and E7 to establish monoclonal cell lines. Chromosomal ploidy was imaged and STR profiles were determined. Cell morphology, colony formation and cell proliferation characteristics were assessed. Androgen receptor (AR) expression and AR-responsiveness to androgen treatment were analysed by immunofluorescence and RT-qPCR, respectively. RNA-seq analysis was performed to identify prostate lineage markers and expression of prostate cancer tumorigenesis-related genes. Two benign cell lines derived from non-cancer cells (AQ0420 and AQ0396) and two tumour tissue derived cancer cell lines (AQ0411 and AQ0415) were immortalised from four patients with localised prostatic adenocarcinoma. The cell lines presented an epithelial morphology and a slow to moderate proliferative rate. None of the cell lines formed anchorage independent colonies or displayed AR-responsiveness. Comparative RNA-seq expression analysis confirmed the prostatic lineage of the four cell lines, with a distinct gene expression profile from that of the metastatic prostate cancer cell lines, PC-3 and LNCaP. Comprehensive characterization of these cell lines may provide new in vitro tools that could bridge the current knowledge gap between benign, early-stage and metastatic disease.

Abstract 3444: Role of AKR1C3 in converting reservoirs of DHEA-S into potent androgens that drive prostate cancer cell growth

Abstract Castration resistant prostate cancer (CRPC) treatment aims to stop a resurgence of androgen receptor (AR) signaling with a class of therapeutics known as androgen receptor signaling inhibitors (ARSI). Through inhibition of CYP17A1, Abiraterone (Abi) prevents an upstream step in androgen biosynthesis, while Enzalutamide (ENZ) acts as an AR antagonist. Despite the early success of ARSI, a subset of patients develop resistance and succumb to the disease. One major mode of resistance is thought to occur when steroidogenic enzymes that are upregulated in CRPC convert weaker circulating precursors to testosterone (T) and dihydrotestosterone (DHT) to restore AR signaling. In this study, we identify a mechanism driving intratumoral steroidogenesis that involves AKR1C3 (type 5 17β-hydroxysteroid dehydrogenase type 5). AKR1C3 is a major steroidogenic enzyme in the prostate that is involved in all androgen biosynthetic pathways to T and DHT, upregulated in CRPC patients, and is a component of Abi and ENZ drug resistance. Previously with Taplin et al. we observed in patients on Leuprolide that T was reduced to 5 ng/dL, and the addition of Abi lowered DHEA-S by 90% (from 230,000 ng/dL to 22,000 ng/dL). However, the DHEA-S that remained was 4,000x greater than circulating T, making it a reservoir for intratumoral steroidogenesis post Abi treatment. Here, we demonstrate that post-Abi concentrations of DHEA-S, and castrate levels of DHEA-S (post-leuprolide but pre-Abi treatment), which also corresponds to DHEA-S levels patients on ENZ are 1) converted to T in an AKR1C3-dependent manner in prostate cancer (PCa) cells, and 2) sufficient to stimulate AKR1C3-dependent cell growth. Our observations are consistent across both primary and metastatic PCa cell lines, CWR22PC and DuCaP, respectively. Androgen measurements were made using our highly sensitive and specific stable isotope dilution liquid chromatography tandem mass spectrometry (SID-LC-MS/MS) method. Additionally, we demonstrate AKR1C3-dependence using genetic and pharmacological approaches with an AKR1C3 stable knockdown for each cell line and two AKR1C3 competitive inhibitors. Taken together, we have identified a mechanism of resistance to ARSIs common to both primary and metastatic cell lines that operates through AKR1C3’s intratumoral conversion of DHEA-S to potent androgens that drive prostate cancer growth. Citation Format: Andrea J. Detlefsen, Ling Duan, Clementina Mesaros, Trevor M. Penning. Role of AKR1C3 in converting reservoirs of DHEA-S into potent androgens that drive prostate cancer cell growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3444.

Abstract 6241: LP-184, an acylfulvene class small molecule therapeutic, is synthetically lethal in DNA damage repair deficient cancers

Abstract As many as one third of solid tumors (ovarian, breast, pancreatic, prostate cancers) harbor deficiency in some DNA Damage Repair (DDR) pathways. Such cancers become dependent on alternative DDR pathways to maintain genome integrity, making them selectively vulnerable to DDR inhibitors. The concept of synthetic lethality has been successfully applied to develop strategies to treat subsets of such tumors. Clinically, PARP inhibitors (PARPi) have been successful particularly in Homologous Recombination Deficiency (HRD) cancers. Other agents have also been designed to target these DDR deficiencies in cancer cells and have potential to be clinically beneficial. LP-184 is a next generation acylfulvene prodrug metabolized to an active compound by prostaglandin reductase 1 (PTGR1) that is often elevated in multiple tumors. LP-184-induced DNA lesions are likely repaired by the Nucleotide Excision Repair (NER) and Homologous Repair (HR) pathways. Reduced activities of multiple DDR-related pathways in solid tumor models correlated with increased sensitivities to LP-184 as indicated by Gene Set Enrichment Analysis. Chinese Hamster Ovary cells with NER mutations (ERCC1/2/6) were at least 4 fold more sensitive to LP-184 relative to otherwise isogenic parental cells. ERCC2 or BRCA2 depletion enhanced LP-184 sensitivity 5-8X in a metastatic prostate cancer cell line. LP-184 showed ~120 fold higher potency (IC50 77 nM) compared to Olaparib in HRD prostate cancer organoid model LuCaP 96 (BRCA2/CHEK2 inactivating mutations). Across 14 patient-derived pancreatic, lung and prostate tumor models harboring HR mutations (BRCA1/2, CHEK1/2, ATM/ATR, PALB2, PARP1/2, RAD51, FANCA/B), LP-184 showed ex vivo IC50s in the range of 30-300 nM, whereas Olaparib IC50s ranged from 1700-6900 nM. LP-184 treatment resulted in complete tumor regression (107-141% TGI) in 10/10 HR deficient triple negative breast cancer PDX models of which 7/10 were resistant Olaparib/Niraparib and to Doxorubicin/Cyclophosphamide. LP-184 treatment resulted in complete and durable tumor regression in HRD (BRCA1/ATR mutant) pancreatic cancer PDX models (112-140% TGI). In the ovarian cancer cell line OVCAR3 having HRD/NERD phenotype, LP-184 IC50 was 13 nM, Olaparib IC50 was 145 nM and their combination Bliss Synergy Score was 16 indicating synergy. LP-184 is synthetic lethal resulting from its abilities to cause unresolvable DNA damage if tumor cells express high PTGR1 and are deficient in NER/HR genes. Unlike PARPi, LP-184 has striking activity in both NERD as well as HRD cancers. These strong data have prompted the development of a soon to be launched clinical trial to translate the broad preclinical anticancer activity of LP-184 in solid tumors with HR/NER pathway defects, such as pancreatic, prostate, ovarian and breast cancers. Citation Format: Aditya Kulkarni, Jianli Zhou, Neha Biyani, Kishor Bhatia, Panna Sharma. LP-184, an acylfulvene class small molecule therapeutic, is synthetically lethal in DNA damage repair deficient cancers. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6241.

Abstract 4975: Anti-cancer effect of a probiotic bacteria-derived compound, 1,4-Dihydroxy-2-naphthoic acid in prostate cancer

Abstract Cancer incidence has been increasing globally and the major cause for mortality associated with this disease is due to metastasis development. Followed by skin and lung cancer, prostate cancer (PCa) is one of the most common cancers prevailing among older men in the United States. Although androgen deprivation therapy (ADT) is the mainstay treatment for PCa, most patients undergoing ADT eventually develop metastatic PCa. Moreover, other treatment options, such as chemotherapy and radiotherapy, have toxic side effects and are ineffective in controlling advanced PCa. Hence, there arises a need for identifying alternative agents with possibly fewer side effects. The gut biome plays a significant role in regulating many bodily functions like digestion, immunity, and including cancer prevention. Probiotics, commonly known as 'good bacteria,' are living microorganisms that provide health promoting benefits. A probiotic metabolite, 1,4-Dihydroxy-2-naphthoic acid (DHNA), is an anti-inflammatory aryl hydrocarbon receptor (Ahr) agonist which is yet to be explored for its anticancer activity. Inhibiting the inflammatory signaling axis and activating Ahr by DHNA could be a promising strategy to counteract metastatic PCa. Cell viability assays revealed that 1,4-DHNA is highly toxic in metastatic prostate cancer cell lines such as DU145 and PC3 compared to normal prostate epithelial cells like RWPE-1 and human prostate stromal myofibroblast cell line, WPMY-1, with an approximate IC50 value of 5 µM in DU145 and PC3 and about 20 µM and 75 µM in WPMY-1 and RWPE-1 respectively. DHNA reduced the colony forming abilities of BPH-Cd, PC3, and DU145 in clonogenic assay and suppressed the BPH-Cd spheroid growth in spheroid formation assay, revealing its anti-tumorigenic potential. Trans-well migration assay using BPH-Cd, PC3, and DU145 showed a decrease in cell migration, hinting at the drug's anti-metastatic ability. G2/M phase arrest in cell cycle analysis and dose-dependent increase in apoptosis of DHNA-treated DU145, PC3, and LNCaP cell lines reiterated its anti-cancer potential. Western blot results in PC3 and DU145 showed significant dose-dependent inhibition of protooncogene β-catenin expression. Downregulation of cell cycle proteins like cyclin D1 and increased expression of effector caspase, cleaved caspase 7 support cell death promoting effects of DHNA via an intrinsic apoptotic pathway. Our pre-clinical data suggest that DHNA can be a potential drug for inhibiting both prostate tumor growth and metastasis. Further research is warranted to ascertain the anti-metastatic and underlying anti-cancer mechanisms to help translate the findings to clinical use. Citation Format: Shreeja Srinivas Bitla, Gnanasekar Munirathinam. Anti-cancer effect of a probiotic bacteria-derived compound, 1,4-Dihydroxy-2-naphthoic acid in prostate cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4975.

Abstract 6400: Synergistic combination of NCX 4040 and napabucasin induces immunogenic activation via upregulation of mitochondrial oxidative stress and STAT3 inhibition in cadmium transformed and metastatic prostate cancer cells

Abstract Despite recent diagnostic and therapeutic advances, prostate cancer (PCa) poses a significant burden on men’s health and quality of life, retaining the second highest incidence rate after lung cancer. The combinatorial therapy approach has emerged as a useful treatment option for various types of cancer to target tumor heterogeneity and overcome the limitations of existing treatment modalities. Here, we explored the combination of NCX 4040, a nitric oxide-releasing aspirin derivative and Napabucasin, a recently developed STAT3 and cancer stemness inhibitor as a potential treatment for PCa. Two cellular models were used namely BPH-Cd, a cadmium-transformed carcinogenic cell line and DU145, a brain metastatic PCa cell line. Cell viability assay indicated reduced cell viability in both cell lines in a dose-dependent manner and more so in combination as opposed to individual treatments, with an IC50 of 5 µM for NCX 4040 and 250 nM for Napabucasin. Notably, treatment with catalase prevented the synergistic activity of NCX 4040 and Napabucasin in reducing the viability of these cells. This suggested that NCX 4040 and Napabucasin might be inducing oxidative stress related cellular death. In addition, the combination of NCX 4040 and Napabucasin robustly impeded the in-vitro tumorigenic potential in both cell lines in colony formation assay and decreased the size of spheroids with increasing doses in in-vitro 3D spheroid assay in BPH-Cd. Western blot analysis revealed that in addition to the downregulation of STAT3, NCX 4040 and Napabucasin treatment showed upregulation in cGAS-STING immunogenic activation pathway related markers (pSTING, cGAS, pTBK1 in DU145 and STING, TBK1 in BPH-Cd). This data demonstrated that combination drug treatment might be inducing cell death via immunogenic activation. Additional markers related to this pathway are being tested in both cellular models. Interestingly, thioredoxin (TRX)-interacting protein was highly upregulated in both cell lines following combination treatment indicating that the synergistic effects are mediated via targeting TRX-regulated cellular redox signaling. Subsequently, TRX and thioredoxin reductase 1 were also downregulated in both cell lines. Furthermore, confocal imaging analysis indicated that NCX 4040 and Napabucasin together might be causing DNA damage and mitochondrial stress as DNA release was clearly evident. Flow cytometric analysis demonstrated that the drug combination shows a synergistic effect in producing excess mitochondrial and cellular ROS, causing apoptosis and in inducing cell cycle arrest in both BPH-Cd and DU145 cells. Taken together, our study demonstrates that NCX 4040 and Napabucasin in combination could be a potential anti-PCa therapy which warrants further evaluation for its clinical application. Citation Format: Nishtha Pathak, Gnanasekar Munirathinam. Synergistic combination of NCX 4040 and napabucasin induces immunogenic activation via upregulation of mitochondrial oxidative stress and STAT3 inhibition in cadmium transformed and metastatic prostate cancer cells. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6400.

Abstract 1754: Targeting the mitochondrial protein MAGMAS increases sensitivity to docetaxel in neuroendocrine prostate cancer cells

Abstract Metastatic prostate cancer (PCa) is the leading cause of PCa-associated deaths and one of the leading causes of cancer mortality in men. Novel therapeutics, such as Prostate Specific Membrane Antigen (PSMA) ligand therapy, are emerging as effective treatment strategies for metastatic prostate cancer. However, neuroendocrine differentiated (NED) metastatic PCa, which lacks the PSMA antigen, is deprived of effective biomarkers for disease treatment. Magmas, a 13.8 kDa mitochondrial protein, imports nuclear-encoded mitochondrial proteins into the mitochondrial matrix. Magmas is overexpressed in several aggressive tumors, such as breast cancer, glioblastoma, and prostate cancer. When overexpressed, Magmas plays a role as a cytoprotective protein by acting as a reactive oxygen species (ROS) scavenger that maintains sufficient ROS levels to promote cell proliferation, but below the threshold levels that could lead to apoptosis. This study was designed to investigate the pro-survival and therapy-resistance functions of Magmas in PCa cells expressing NED markers. Predictively, we observed that the docetaxel (DTX)-resistant PC3-DR and DU145-DR PCa cell lines expressed significantly higher levels of Magmas compared to their drug-sensitive parental cell lines. We hypothesized that inhibiting Magmas reduces the aggressive properties of highly proliferative DTX- resistant metastatic PCa cell lines and re-sensitize them to DTX. Magmas knockdown in DTX-sensitive and DTX-resistant PC3 and DU145 cells in the presence of increasing DTX treatments enhanced sensitivity to DTX. Consistent with these results, pharmacological inhibition of Magmas with the novel BT#9 inhibitor in combination with increasing DTX concentrations also enhanced sensitivity to DTX in these cell lines. Additional studies using clonogenic assays, cell migration/invasion assays, and tumorsphere formation assays are currently underway to further establish Magmas as a potential therapeutic target to attenuate the aggressive properties of chemoresistant PCa cells. Lastly, we will investigate the diagnostic potential of Magmas as a biomarker for NED and BT#9 as an imaging/therapeutic-specific agent for NED. Citation Format: Alfonso M. Durán, Christian H. Yoo, Jennifer D. Tran, Krystal Santiago, Adil S. Mohammed, Carlos A. Casiano, Frankis A. Almaguel. Targeting the mitochondrial protein MAGMAS increases sensitivity to docetaxel in neuroendocrine prostate cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1754.

Application of Gold Nanoparticles as Radiosensitizer for Metastatic Prostate Cancer Cell Lines

More than 50% of all prostate cancer (PCa) patients are treated by radiotherapy (RT). Radioresistance and cancer recurrence are two consequences of the therapy and are related to dose heterogeneity and non-selectivity between normal and tumoral cells. Gold nanoparticles (AuNPs) could be used as potential radiosensitizers to overcome these therapeutic limitations of RT. This study assessed the biological interaction of different morphologies of AuNPs with ionizing radiation (IR) in PCa cells. To achieve that aim, three different amine-pegylated AuNPs were synthesized with distinct sizes and shapes (spherical, AuNPsp-PEG, star, AuNPst-PEG, and rods, AuNPr-PEG) and viability, injury and colony assays were used to analyze their biological effect on PCa cells (PC3, DU145, and LNCaP) when submitted to the accumulative fraction of RT. The combinatory effect of AuNPs with IR decreased cell viability and increased apoptosis compared to cells treated only with IR or untreated cells. Additionally, our results showed an increase in the sensitization enhancement ratio by cells treated with AuNPs and IR, and this effect is cell line dependent. Our findings support that the design of AuNPs modulated their cellular behavior and suggested that AuNPs could improve the RT efficacy in PCa cells.

The androgen receptor as a potential regulator of prostate cancer contractility.

Prostate cancer (PCa) is a common health hazard for men that displays androgen-dependent growth at early stages through signalling mediated by the Androgen Receptor (AR). This has inspired androgen deprivation therapy (ADT) to be the gold standard treatment; however, in later stages, PCa displays a transition to androgen-independence and loss of AR, accompanied by a drastic increase in invasiveness. Critically, both the loss of AR and ADT have been shown to induce PCa invasiveness by promoting the epithelial-to-mesenchymal transition (EMT) which has been associated with biophysical changes in other cell models. Indeed, during metastasis cancers cells change their biophysical properties (reduced cell stiffness, increased contractility) facilitating migration through crowded microenvironments. Given AR's essential role in mediating PCa progression, we suspect that AR signalling may also regulate mechanical transitions required for PC metastasis and directed cell migration. In this study we characterize PCa biophysics in response to changes in AR signalling and expression. First, we applied Traction Force Microscopy on the metastatic PCa cell line LNCaP (AR-positive) to quantify contractile changes from androgen deprivation and supplementation, observing a non-monotonic contractile response with increasing androgen dose. These results suggest that the androgen-induced biophysical response shifts depending on the androgen availability, a finding consistent with past reports demonstrating that distinct pathways depend on both androgen concentration and AR expression. Regarding the latter, we then evaluated how AR expression and activity (nuclear localization) affects PCa biophysics by quantifying the contractility of highly metastatic PC3 cells with and without AR expression under varying androgen concentrations. We find that cell contractility is positively correlated with AR nuclear localization in androgen-containing media, yet negatively correlated in androgen-deprived media. These results complement emerging trends suggesting AR may have an important mechanobiological role in PCa migration and metastasis.

Abirateron ve Docetaxel Tedavileri Metastatik Prostat Kanseri Hücrelerinde Phospho-PTEN Ekspresyonunu Arttırır

Aim: Prostate cancer is the second leading cause of death in cancer-related deaths in men. Docetaxel and abiraterone acetate are widely used in the treatment of castration-resistant metastatic prostate cancer. Phospho-PTEN triggers proliferation, migration, angiogenesis and survival in cells by causing oncogenic Akt hyperactivation. This study, it is aimed to investigate the effects of docetaxel and abiraterone acetate agents, which are widely used in the treatment of prostate cancer, on the expression of phospho-PTEN, which stimulates the oncogenic pathway. Material and Methods: The effects of docetaxel and abiraterone acetate on phospho-PTEN expression in androgen receptor (+) and androgen receptor (-) metastatic prostate cancer cell lines were investigated in vitro by immunofluorescence method. Results: Findings were compatible in both androgen receptor (+) and androgen receptor (-) metastatic prostate cancer cell lines. No statistically significant difference in phospho-PTEN expression was observed between the control and abiraterone acetate groups. Phospho-PTEN expression was increased statistically significant in docetaxel and abiraterone acetate+docetaxel groups compared to control. This increase was greater statistically significant in the combined group given the two agents compared to the docetaxel group. Conclusion: A significant increase in phospho-PTEN was observed in the docetaxel and combined treatment groups. The increase of Phospho-PTEN causes oncogenic Akt hyperactivation. According to this information, docetaxel and combined drug treatments may support the oncogenic pathway in cells by increasing phospho-PTEN in patients. To eliminate these effects in patients, the administration of agents that dephosphorylate PTEN or agents that will stimulate the pathways that provide dephosphorylation may increase the total survival of the patients.

Cancer-derived exosomal miR-375 targets DIP2C and promotes osteoblastic metastasis and prostate cancer progression by regulating the Wnt signaling pathway.

Bone metastasis is the most common complication responsible for most deaths in the advanced stages of prostate cancer (PCa). However, the exact mechanism of bone metastasis in PCa remains unelucidated. Herein, we explored the function and potential underlying mechanism of exosomal miR-375 in bone metastasis and tumor progression in PCa. This study revealed that miR-375 expression was markedly upregulated in advanced PCa with bone metastasis and metastatic PCa cell lines. Moreover, miR-375 showed high expression in PCa-derived exosomes and could be delivered to human mesenchymal stem cells (hMSCs) via exosomes. Mechanistically, miR-375 directly targeted DIP2C and upregulated the Wnt signaling pathway, thereby promoting osteoblastic differentiation in hMSCs. Furthermore, miR-375 promoted the proliferation, invasion, and migration of PCa cells in vitro and enhanced tumor progression and osteoblastic metastasis in vivo. Notably, the expression of miR-375, TCF-1, LEF-1, and β-catenin in was higher in PCa tissues with bone metastasis than in PCa tissues without bone metastasis and showed a continuous increase, whereas DIP2C, cyclin D1, and Axin2 showed an opposite expression pattern. In conclusion, our study suggests that cancer-derived exosomal miR-375 targets DIP2C, activates the Wnt signaling pathway, and promotes osteoblastic metastasis and PCa progression.

The Subline of Metastatic Prostate Cancer Cell line, DU145 expresses Tks4 and reveals distinctive Phenotype

Cancer metastasis is the process of dissemination of cancer cells from their original site and localization in distant sites. During this journey, metastatic cancer cells have to undergo several phenotypical/ genotypical changes for acquiring cell migration, invasion, attachment properties etc. These steps can be partially/fully mimicked under in vivo and in vitro conditions. Here, we injected metastatic prostate cancer cell line, DU145, into the chorioallantoic membrane )CAM( of the chicken embryo to generate sublines which were isolated 7-days post-injection, and subcultured under in vitro conditions. Our results showed that one of these sublines, DC-1-, exhibited a distinctive phenotype compared with the parental cell line when grown in 3D culture model. Further, the expression of Tks4 at the mRNA and protein level in DC-1- cells was observed to be higher than the regular DU145 cells. Keywords: Prostate cancer, DU145, DC-1-, Metastasis, Round, Stellate, Colony, Tks4