Prostate Tumor Model Research Articles

Dynamic reciprocal interactions between activated T cells and tumor associated macrophages drive macrophage reprogramming and proinflammatory T cell migration within prostate tumor models

Tumor-associated macrophages (TAMs) have been implicated as a tumor microenvironment (TME) cell population, which may be playing a vital role in the inhibition of effective T cell responses in the prostate TME. In this manuscript, we leverage a novel microscale cell culture platform, known as Stacks, to investigate mono-, co-, and tri-culture TME models comprised of prostate tumor cell lines, primary macrophages, and autologous T cells from patients with prostate cancer. Through multiplexed analysis of these multi-cellular prostate tumor models, we capture a dynamic interaction between primary TAMs and activated T cells that resulted in reciprocal proinflammatory activation of both cell populations upon interaction. These findings suggest that activated T cells are capable of reprogramming immunosuppressive TAMs in the context of prostate tumor models and that TAM reprogramming may play a key supportive role in restoring proinflammatory T cell tumor responses in the prostate TME.

Abstract 4649: BLX-3030, a potent, selective, orally available small molecule CDK9 inhibitor for aggressive variant prostate cancers

Abstract Background: The use of novel, potent targeted therapies in prostate cancers has led to the development of highly aggressive variant cancers, including neuroendocrine prostate cancer (NEPC). Gene amplification of N-MYC and C-MYC oncogenes leads to its overexpression in NEPC and mCRPC patients, highly prevalent in these lethal subtypes of cancers detected in 2% of all Prostate Cancers (PCa) and over 10-17% of mCRPC patients. N-MYC is a transcriptional target of CDK9, which acts as an oncogenic driver sufficient to transform human-derived prostate cancer to take on NEPC phenotypic changes resulting in a more aggressive disease identified in late-stage human PCa patients. Additionally, N-MYC and C-MYC are required for tumor drug resistance, and their downregulation through CDK9 inhibition lowers tumor growth. Our efforts have demonstrated that targeting both N-MYC and C-MYC as a driver of NEPC and mCRPC with highly selective CDK9 inhibitor BLX-3030 is a viable approach for therapeutic intervention of mCRPC and NEPC. Materials and Methods: Our empirical data-driven AI/ML MolecuLernTM fragment library, workflows, LigEdit design strategies, and hit2-lead optimization methods are employed. In vitro experiments include kinase glo, cell titer glo, selectivity profiler, ADME-Tox, FACS/apoptosis, cell migration, live cell imaging, immunofluorescent, western blot, combination studies and in vivo experiments including PK, prostate tumor models, 7-day tox, BLX-3030 non (GMP) scaleup and safety pharmacology experiments conducted. Results: We synthesized a series of novel small molecule CDK9 inhibitors that reversibly bind to CDK9, competitively block the ATP site with an IC50 of 1.06 nM, and elicit pharmacological responses in N-MYC, C-MYC, and other prostate cancer cells in vitro and in vivo. We studied the CDK9 N-MYC expression detected in PC-3, DU-145, LNCaP, and in LASCPC-01, NCI-H660, and 22RV1 cell lines. BLX-3030 exhibited potent cellular efficacy with an IC50 of 22 to 590 nM in PC cell lines and in N-MYC expressed cells had an activity of 76, 470, and 132 nM respectively, and reduced pCDK9, C-MYC, Mcl-1, N-MYC and its downstream RNA Pol II (Ser-2) and pAR (Ser-81) dose-dependently. BLX-3030 exhibits in vivo antitumor activity in LASCPC-01, 22RV1, and C4-2 prostate cancer mouse models. Several ADME-Tox, MTD, dose range finding, hERG and other in vivo safety pharmacology experiments have advanced BLX-3030 to the IND enabling studies. Conclusions: BLX-3030 is currently being investigated in non-clinical toxicology, toxicokinetic, and core battery of safety pharmacology studies including the assessment of effects on cardiovascular, central nervous, and respiratory systems. Citation Format: Zhaoang li, Chenyu Lin, Kyle Medley, Hariprasad Vankayalapati, David J. Bearss. BLX-3030, a potent, selective, orally available small molecule CDK9 inhibitor for aggressive variant prostate cancers [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 4649.

Abstract 3996: Secreted cytokine-αPDL1 fusion proteins improve solid tumor chimeric antigen receptor (CAR) T-cell therapy

Abstract Background: Success of Chimeric Antigen Receptor (CAR) T cells therapy for solid tumors are limited by the suppressive solid tumor microenvironment (TME), T cell exhaustion, lack of persistence, and poor trafficking to tumors. Strategies to improve this include therapeutic combinations, such as checkpoint inhibition (CPI) or cytokine support. However, CPI therapy has largely failed because of refractory and resistant tumors and cytokine administration can lead to lethal toxicities. To this end, we propose that enabling CAR T cells to secrete bi-functional fusion proteins consisting of cytokine modifiers (ie: IL12, IL15, or TGFβ-trap) combined with checkpoint inhibition (αPDL1 scFv) can provide tumor PDL1 sequestered cytokine activity and local tumor-immune modulation to boost solid tumor CAR T cell efficacy, enhance CPI impacts, and safely improve durable outcomes. Methods: Mouse T cells dual transduced to express surface CAR targeting prostate or ovarian solid tumors in addition to secretable cytokine fused to an αPDL1 scFv were generated. In vitro, the PDL1 blockade capacity and tumor-surface cytokine presentation of supernatants from dual transduced CAR T cells was assessed on PDL1 induced tumor cells. Further, secreted fusion protein transduced CAR T cells were assessed for function, phenotype, and cytokine release in a repetitive tumor rechallenge assay. In vivo, mouse CAR T cells dual transduced with fusion proteins and appropriate controls were assessed for anti-tumor efficacy, survival kinetics, and toxicity in immunocompetent solid tumor mouse models of prostate cancer and intraperitoneal disseminated ovarian cancer. Results: CAR T cells were shown to be successfully dual transduced, and secreted αPDL1-cytokine fusion proteins exhibiting functional PDL1 binding characteristics in vitro. CAR T cells engineered with αPDL1-IL12 fusion protein had greater anti-tumor activity and CAR specific expansion compared to other tested fusion proteins in in vitro co-culture assays. In a syngeneic prostate tumor model, mice receiving CAR T cells with αPDL1-IL12 fusion T cells out competed other cytokine fusion combinations. In a syngeneic ovarian tumor model we safely achieved 100% curative response rate with CAR secreting αPDL1-IL12 fusion in contrast to CAR with αPDL1mutIL12 control along with tumor regional PDL1 blockade on myeloid subsets within the TME. Conclusions: Our findings suggest that CAR T cells engineered to secrete αPD-L1-IL12 fusion protein show improved tumor control, less systemic toxicity, and enhanced expansion which promotes eradication of disease in two independent in vivo tumor models with two unique solid tumor CAR targets. We believe this strategy has the potential to improve solid tumor CAR T-cell efficacy and enhance durable innate immune responses. Citation Format: Lea Christian, John P. Murad, Lupita Lopez, Anthony Park, Jason Yang, Eric Lee, Candi Trac, Stephen Forman, Saul J. Priceman. Secreted cytokine-αPDL1 fusion proteins improve solid tumor chimeric antigen receptor (CAR) T-cell 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 3996.

Capivasertib combines with docetaxel to enhance anti-tumour activity through inhibition of AKT-mediated survival mechanisms in prostate cancer

Background/objectiveTo explore the anti-tumour activity of combining AKT inhibition and docetaxel in PTEN protein null and WT prostate tumours.MethodsMechanisms associated with docetaxel capivasertib treatment activity in prostate cancer were examined using a panel of in vivo tumour models and cell lines.ResultsCombining docetaxel and capivasertib had increased activity in PTEN null and WT prostate tumour models in vivo. In vitro short-term docetaxel treatment caused cell cycle arrest in the majority of cells. However, a sub-population of docetaxel-persister cells did not undergo G2/M arrest but upregulated phosphorylation of PI3K/AKT pathway effectors GSK3β, p70S6K, 4E-BP1, but to a lesser extent AKT. In vivo acute docetaxel treatment induced p70S6K and 4E-BP1 phosphorylation. Treating PTEN null and WT docetaxel-persister cells with capivasertib reduced PI3K/AKT pathway activation and cell cycle progression. In vitro and in vivo it reduced proliferation and increased apoptosis or DNA damage though effects were more marked in PTEN null cells. Docetaxel-persister cells were partly reliant on GSK3β as a GSK3β inhibitor AZD2858 reversed capivasertib-induced apoptosis and DNA damage.ConclusionCapivasertib can enhance anti-tumour effects of docetaxel by targeting residual docetaxel-persister cells, independent of PTEN status, to induce apoptosis and DNA damage in part through GSK3β.

Abstract A085: A luminal intermediate cell state maintains long-term prostate homeostasis and contributes to tumorigenesis

Abstract Cellular heterogeneity poses tremendous challenges for developing cell-targeted therapies and biomarkers of clinically significant prostate cancer. The origins of this heterogeneity within the cellular complexities of normal adult and aging tissue remain unknown leaving important cellular states and transcriptional programs that allow the expansion of malignant clones in early cancer unidentified. These unresolved questions hamper the development of novel therapies designed to block the deregulated proliferation of prostate epithelial cells. To define cell states that contribute to early cancer development, we performed in vivo lineage tracing with multicolor reporters, whole organ mapping and single cell transcriptomics of normal and malignant prostate from genetically-engineered mouse models. We show here that the long-term luminal homeostasis is maintained by multiple clones with various fitness levels. Long-term clonal expansions are enabled by a luminal transcriptional state harboring basal markers (Luminal Intermediate, LumI) and controlled by Wnt/p63 signaling. Moreover, LumI cells greatly expand during early stages of tumorigenesis in several mouse models of prostate cancer. Specific genetic ablation of p63 from luminal cells in vivo decreases clonal activity in homeostasis and reduces the formation of aggressive clones in prostate tumor models. Finally, the LumI cells and Wnt signaling appear to significantly increase in human aging prostate and prostate cancer samples, highlighting the importance of this hybrid cell state for human pathologies with potential translational impact. Our models reveal a continuity of this cell state from normal homeostasis to aging and early cancer with specific alterations at each stage. Understanding how the luminal intermediate cell state is regulated in homeostasis and deregulated in hyperproliferative contexts is crucial for the development of prognostic markers and new therapeutic interventions for prostate diseases. Citation Format: Fu Luo, Lara F. Tshering, Karis Tutuska, Mariola Szenk, Diana Rubel, James G. Rail, Savanah Russ, Jingxuan Liu, Alice Nemajerova, Gábor Balázsi, Flaminia Talos. A luminal intermediate cell state maintains long-term prostate homeostasis and contributes to tumorigenesis [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr A085.

Evaluation of a photodynamic therapy agent using a canine prostate cancer model.

Male dogs can develop spontaneous prostate cancer, which is similar physiologically to human disease. Recently, Tweedle and coworkers have developed an orthotopic canine prostate model allowing implanted tumors and therapeutic agents to be tested in a more translational large animal model. We used the canine model to evaluate prostate-specific membrane antigen (PSMA)-targeted gold nanoparticles as a theranostic approach for fluorescence (FL) imaging and photodynamic therapy (PDT) of early stage prostate cancer. Dogs (four in total) were immunosuppressed with a cyclosporine-based immunosuppressant regimen and their prostate glands were injected with Ace-1-hPSMA cells using transabdominal ultrasound (US) guidance. Intraprostatic tumors grew in 4-5 weeks and were monitored by ultrasound (US). When tumors reached an appropriate size, dogs were injected intravenously (iv) with PSMA-targeted nano agents (AuNPs-Pc158) and underwent surgery 24 h later to expose the prostate tumors for FL imaging and PDT. Ex vivo FL imaging and histopathological studies were performed to confirm PDT efficacy. All dogs had tumor growth in the prostate gland as revealed by US. Twenty-four hours after injection of PSMA-targeted nano agents (AuNPs-Pc158), the tumors were imaged using a Curadel FL imaging device. While normal prostate tissue had minimal fluorescent signal, the prostate tumors had significantly increased FL. PDT wasactivated by irradiating specific fluorescent tumor areas with laser light (672 nm). PDT bleached the FL signal, while fluorescent signals from the other unexposed tumor tissues were unaffected. Histological analysis of tumors and adjacent prostate revealed that PDT damaged the irradiated areas to a depth of 1-2 mms with the presence of necrosis, hemorrhage, secondary inflammation, and occasional focal thrombosis. The nonirradiated areas showed no visible damages by PDT. We have successfully established a PSMA-expressing canine orthotopic prostate tumor model and used the model to evaluate the PSMA-targeted nano agents (AuNPs-Pc158) in the application of FL imaging and PDT. It was demonstrated that the nano agents allowed visualization of the cancer cells and enabled their destruction when they were irradiated with a specific wavelength of light.

An in-vivo study of the combined therapeutic effects of pulsed non-thermal focused ultrasound and radiation for prostate cancer

Purpose The purpose of this study was to investigate the in vivo combined effects of pulsed focused ultrasound (pFUS) and radiation (RT) for prostate cancer treatment. Materials and Methods An animal prostate tumor model was developed by implanting human LNCaP tumor cells in the prostates of nude mice. Tumor-bearing mice were treated with pFUS, RT or both (pFUS + RT) and compared with a control group. Non-thermal pFUS treatment was delivered by keeping the body temperature below 42 °C as measured real-time by MR thermometry and using a pFUS protocol (1 MHz, 25 W focused ultrasound; 1 Hz pulse rate with a 10% duty cycle for 60 sec for each sonication). Each tumor was covered entirely using 4–8 sonication spots. RT treatment with a dose of 2 Gy was delivered using an external beam (6 MV photon energy with dose rate 300MU/min). Following the treatment, mice were scanned weekly with MRI for tumor volume measurement. Results The results showed that the tumor volume in the control group increased exponentially to 142 ± 6%, 205 ± 12%, 286 ± 22% and 410 ± 33% at 1, 2, 3 and 4 weeks after treatment, respectively. In contrast, the pFUS group was 29% (p < 0.05), 24% (p < 0.05), 8% and 9% smaller, the RT group was 7%, 10%, 12% and 18% smaller, and the pFUS + RT group was 32%, 39%, 41% and 44% (all with p < 0.05) smaller than the control group at 1, 2, 3, and 4 weeks post treatment, respectively. Tumors treated by pFUS showed an early response (i.e. the first 2 weeks), while the RT group showed a late response. The combined pFUS + RT treatment showed consistent response throughout the post-treatment weeks. Conclusions These results suggest that RT combined with non-thermal pFUS can significantly delay the tumor growth. The mechanism of tumor cell killing between pFUS and RT may be different. Pulsed FUS shows early tumor growth delay, while RT contributes to the late effect on tumor growth delay. The addition of pFUS to RT significantly enhanced the therapeutic effect for prostate cancer treatment.

Beta-D-glucan Polysaccharide Downregulates p53, and Prostate Specific Antigen Expression in Histological and Immunohistochemical study of Prostate Tumor Model

Global increase in cancer incidence has prompted the search for natural bioactive products which&nbsp;are readily available, safer and more affordable. Beta-D-glucan polysaccharide (βDgP) is a phytochemical fractionate of an edible mushroom Auricularia polytricha known to have anti cancer property but information about the actual mechanism underlying its therapeutic property is lacking. This research investigates the tumor regulatory effect of Beta-D-glucan polysaccharide on some tumor markers; p53 and Prostate Specific Antigen (PSA) in nitrosobis amine (NA) – induced prostate tumor model of Wister rat. Twenty-four male Wister rats were divided into four groups with six rats in each group. Group A served as normal control while treatment groups: B (5mg/kgbw nitrosobis amine only); C and D (placed on 120 mg/kgbw and 250 mg/kgbw respectively) after inducing tumor. The experiment lasted for 10 weeks. At termination, ELISA method was used to evaluate PSA levels; p53 tumor marker was assessed using immunohistochemical methods; histological alterations were examined using routine H&amp;E technique. Results shown that p53 and PSA levels increased significantly (at p≤0.05) in group B (tumor control) when compared to normal control. Increase in papillary fronds, basal cell hyperplasia and prostatic concretions depicted cytoarchitectural alterations in tumor control group. However, expression of p53 and PSA was down-regulated significantly (p≤0.05) when compared to tumor control, and histological distortions reversed in a dose-dependent manner, following administration of graded concentration of βDgP. Findings from the present study have revealed the anti-tumor property of βDgP in NA-induced prostate tumor model in Wister rat.&nbsp

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.

Using microfluidic models to evaluate whether monocyte preconditioning plays a role in tumor-associated macrophage mediated resistance to hormone therapy in men with prostate cancer.

228 Background: While men with metastatic castrate-resistant prostate cancer benefit greatly from 2nd generation androgen targeted therapies (ATTs), the utility of these therapies is inevitably limited by the development of resistance. Tumor associated macrophages (TAMs) are a myeloid immune cell population within the prostate tumor microenvironment (TME) that have been shown to play an integral role in development of ATT-resistance. However, the pathways that underlie TAM-mediated ATT resistance remain under investigation. In particular, many TAMs within the TME are derived from circulating monocytes and it is not yet clear whether the pathways driving TAM-mediated resistance are activated exclusively within the TME or if the activation of critical resistance pathways begins while the cells are circulating as monocytes. In this study, we utilized novel microscale technologies to investigate the transcriptome of monocytes and macrophages derived from patients progressing and responding to ATTs as well as the degree to which the macrophages promote ATT resistance in prostate tumor models. Methods: Primary monocytes were isolated from 22 men with prostate cancer who were either progressing or responding to 2ndgeneration ATTs. A portion of the monocytes from each patient were isolated for transcriptome analysis and the rest were differentiated into monocyte-derived macrophages (MDMs). MDMs were then cultured in monoculture or in co-culture with androgen-independent prostate tumor cells (22Rv1 and C42B). Each culture was then left untreated or treated with enzalutamide therapy. Following culture/treatment, each macrophage condition was isolated for transcriptome analysis and tumor cell populations from each condition were evaluated for treatment cytotoxicity. Results: Viability data from MDM-C42B co-culture demonstrated a 20% increase in tumor cell viability following enzalutamide treatment when C42B cells were cultured with primary MDMs from castrate-sensitive patients as compared to MDMs from castrate-resistant patients. Subsequent transcriptome analysis demonstrated key signatures in monocyte/macrophage populations that were associated ATT response. Conclusions: Leveraging a novel microfluidic culture platform known as Stacks, we were able to utilize primary, patient-derived cells to demonstrate that the role of TAMs in ATT resistance within the prostate TME is dependent, at least in part, on factors that are present prior to extravasation into the TME. Transcriptome analysis identified candidate pathways, which may be driving TAM-mediated differences in ATT response. These findings have the potential to lead to future use of circulating monocytes as a predictive biomarker as well as lead to the identification and targeting of ATT resistance pathways in patients.

Allosteric inhibition of HSP70 in collaboration with STUB1 augments enzalutamide efficacy in antiandrogen resistant prostate tumor and patient-derived models

Ubiquitin proteasome activity is suppressed in enzalutamide resistant prostate cancer cells, and the heat shock protein 70/STIP1 homology and U-box-containing protein 1 (HSP70/STUB1) machinery are involved in androgen receptor (AR) and AR variant protein stabilization. Targeting HSP70 could be a viable strategy to overcome resistance to androgen receptor signaling inhibitor (ARSI) in advanced prostate cancer. Here, we showed that a novel HSP70 allosteric inhibitor, JG98, significantly suppressed drug-resistant C4–2B MDVR and CWR22Rv1 cell growth, and enhanced enzalutamide treatment. JG98 also suppressed cell growth in conditional reprogramed cell cultures (CRCs) and organoids derived from advanced prostate cancer patient samples. Mechanistically, JG98 degraded AR/AR-V7 expression in resistant cells and promoted STUB1 nuclear translocation to bind AR-V7. Knockdown of the E3 ligase STUB1 significantly diminished the anticancer effects and partially restored AR-V7 inhibitory effects of JG98. JG231, a more potent analog developed from JG98, effectively suppressed the growth of the drug-resistant prostate cancer cells, CRCs, and organoids. Notably, the combination of JG231 and enzalutamide synergistically inhibited AR/AR-V7 expression and suppressed CWR22Rv1 xenograft tumor growth. Inhibition of HSP70 using novel small-molecule inhibitors coordinates with STUB1 to regulate AR/AR-V7 protein stabilization and ARSI resistance.

Abstract 284: A 3D multicellular in vitro prostate cancer model featuring racially/ethnically diverse PDXs

Abstract Current in vitro prostate cancer (PCa) research tools do not incorporate the complexities of the tumor microenvironment including perfusion, multiple cell types, extracellular matrix (ECM) and 3D-orientation. Additionally, these models lack racial/ethnic (R/E) diversity, failing to address the cancer health disparity (CHD) observed in Black men with PCa who experience double the incidence and mortality rates as compared to White men. Population-based in vitro PCa models that support crosstalk between different cell types will improve our understanding of the underlying mechanisms contributing to this CHD and improve the prediction of drug response in specific populations. Here, we used the high-throughput, perfusion-based microfluidic platform called the MIMETAS OrganoPlate® to culture up to 96 individual, multicellular PCa-on-a-chip cultures in parallel. PCa PDX cells of various R/E were embedded together with E2Crimson-labeled stromal fibroblasts in a migration-permissive hyaluronic acid hydrogel in the gel compartment, alongside an endothelium-lined perfusion channel containing a targeted immune cell population. Using high content imaging, we confirmed the stability and viability of the cultures over 7 days. The cultures maintained a 3D structure with PCa cells and fibroblasts evenly dispersed throughout the height of the gel compartment and a blood vessel-like structure within the perfusion channel. Closer evaluation of the gel compartment revealed a close association between PCa cells and stromal fibroblasts in a core-shell structure with PCa clusters surrounded by fibroblasts. Further, all cells maintained expected expression of phenotypic markers (PCa: epCAM, PSMA; fibroblast: vimentin, endothelium: CD31). For the immune component, medium and cell tracker dye conditions were optimized to support immune cell viability. Over 72 hours, immune cells were monitored, revealing migration of PBMCs through the gel compartment. Finally, the value of the complex, population-based multicellular in vitro model of PCa will be evaluated in a drug screen comparing the system with simple, PCa PDX monocultures. This R/E diverse 3D prostate tumor model will enable the full incorporation of all cell types and ECM into a single model which will better recapitulate population specific PCa and drug response. Citation Format: Divya Iyer, Andrei Bonteanu, Peter Shepherd, Rick Kittles, Nora Navone, Daniel Harrington, Kristin Bircsak. A 3D multicellular in vitro prostate cancer model featuring racially/ethnically diverse PDXs [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 284.

Abstract 4231: Hypoxia reduction in tandem with anti-angiogenic therapy remodels the pancreatic tumor microenvironment

Abstract Pancreatic cancer patients remain largely unresponsive to single agent immune checkpoint blockade (ICB) therapy. This refractory state originates from PDAC’s unique immunosuppressive microenvironment that is densely populated by suppressive myeloid cells, exhibits poor vascularity, and is highly hypoxic. We previously showed that the hypoxia-activated prodrug TH-302 (Evofosfamide) reduces intratumoral hypoxia through a tissue remodeling process, initiates tumor vasculature reorganization, and sensitizes aggressive, spontaneous murine models of prostate cancer to ICB. In a clinical trial testing the combination of Evofosfamide with cytotoxic T-lymphocyte-associated protein (CTLA-4) blockade (NCT03098160) a subset of metastatic, immune checkpoint blockade refractory patients showed prolonged progression free survival. While these studies highlight hypoxia reduction as therapeutically tractable, we lack complete understanding of the contribution of the tumor vasculature to hypoxia reduction therapy, as well as the downstream consequences of hypoxia reduction on the cellular composition of the tumor microenvironment and the responsiveness to immunotherapy. We used a transplantable, orthotopic pancreatic tumor model derived from Kras+/LSL-G12D; Trp53+/LSL-R172H; Pdx1-Cre mice and a syngeneic prostate tumor model to study tumor responses to hypoxia-reduction, anti-angiogenic therapy, and combination immunotherapy. We find that Evofosfamide with anti-VEGFR-2 (DC101) significantly extends mouse survival. Combination therapy reduces intratumoral hypoxia, improves vessel integrity, and increases intratumoral DNA damage. In response to the improved metabolic microenvironment, CD8 T cells gain enhanced effector function and lose expression of exhaustion-associated features. Like other anti-angiogenic regimens, combination Evofosfamide and DC101 leads to an increased frequency of PD-L1 expressing cells within the tumor, however blockade of PD-1 failed to prolong survival. Bulk-tumor RNA sequencing and tumor infiltrating lymphocyte analysis implicates immature myeloid cells as mediators of resistance. Re-education of the infiltrating myeloid stroma with CD40 agonist could improve responses to hypoxia-reducing, anti-angiogenic therapy. Put together, these data indicate that targeted hypoxic reduction with anti-angiogenic therapy remodels the pancreatic tumor microenvironment. In this setting, CD40 agonist over PD-1 blockade provides an additive benefit in prolonging mouse survival. Citation Format: Arthur J. Liu, Michael A. Curran. Hypoxia reduction in tandem with anti-angiogenic therapy remodels the pancreatic 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 4231.

329 Longitudinal immune profiling reveals unique myeloid and T cell phenotypes associated with spontaneous immunoediting in a novel prostate tumor model

OBJECTIVES/GOALS: Few preclinical models exist to study how tumors transition from prolonged stable disease ('equilibrium') to progressive disease ('escape'). We characterized a new murine tumor model the exhibits such behavior, and sought to identify and validate the role of unique tumor-infiltrating immune cell subsets in this process. METHODS/STUDY POPULATION: We evaluated growth of NPK-C1 (originally LM7304; received from Dr. Cory Abate-Shen at Columbia University), a cell line developed from spontaneous prostate cancer lung metastases in NPK mice (Nkx3.1CreERT2/+Ptenflox/floxKrasLSL-G12D/+R26R-LSL-YFP/+), in immune competent (C57BL/6) and immune deficient mice (J/Nu). We determined the role of CD4 and CD8 T cells in regulating the 'equilibrium to escape’ growth dynamics of NPK-C1 via in vivo cell depletions at key inflection points of tumor growth. To deeply profile the immune contexture of NPK-C1 at these inflection points, we developed a 28-color immunophenotyping panel for use on a Cytek Aurora spectral flow cytometer. We performed dimensionality reduction and clustering analyses on these data using tSNE and FlowSOM algorithms within FlowJo (v10.6). RESULTS/ANTICIPATED RESULTS: We found that activated CD4 effector T cells are enriched in regressing NPK-C1 tumors, highlighting a role for CD4 T cells in antitumor immunity. CD8 T cells are also important for NPK-C1 control; specifically central memory-like cytotoxic CD8 T cells. Depletion of either CD4 or CD8 T cells during the equilibrium phase of NPK-C1 growth confirmed the role of these cells in antagonizing NPK-C1 escape. Tregs as a whole were counterintuitively enriched in regressing tumors, however high dimensional analysis reveals their significant phenotypic diversity, with a number of Treg subpopulations enriched in progressing tumors. In the myeloid compartment, we found that iNOS+ DC-like cells are enriched in regressing tumors, while CD103+ DCs are associated with late stage tumor progression. DISCUSSION/SIGNIFICANCE: In total, these analyses of the NPK-C1 model provide novel insights into the roles of lymphoid and myeloid populations throughout key phases of tumor/immune co-evolution, and highlight a role for multi-dimensional flow cytometry-based analyses to more deeply understand immune cell dynamics in the tumor microenvironment.

Development of a novel castration-resistant orthotopic prostate cancer model in New Zealand White rabbit.

Prostate cancer (PCa) models in mice and rats are limited by their size and lack of a clearly delineated or easily accessible prostate gland. The canine PCa model is currently the only large animal model which can be used to test new preclinical interventions but is costly and availability is sparse. As an alternative, we developed an orthotopic human prostate tumor model in an immunosuppressed New Zealand White rabbit. Rabbits are phylogenetically closer to humans, their prostate gland is anatomically similar, and its size allows for clinically-relevant testing of interventions. Rabbits were immunosuppressed via injection of cyclosporine. Human PC3pipGFP PCa cells were injected into the prostate via either (a) laparotomy or (b) transabdominal ultrasound (US) guided injection. Tumor growth was monitored using US and magnetic resonance imaging (MRI). Contrast-enhanced ultrasound (CEUS) imaging using nanobubbles and Lumason microbubbles was also performed to examine imaging features and determine the optimal contrast dose required for enhanced visualization of the tumor. Ex vivo fluorescence imaging, histopathology, and immunohistochemistry analyses of the collected tissues were performed to validate tumor morphology and prostate-specific membrane antigen (PSMA) expression. Immunosuppression and tumor growth were, in general, well-tolerated by the rabbits. Fourteen out of 20 rabbits, with an average age of 8 months, successfully grew detectable tumors from Day 14 onwards after cell injection. The tumor growth rate was 39 ± 25 mm2 per week. CEUS and MRI of tumors appear hypoechoic and T2 hypointense, respectively, relative to normal prostate tissue. Minimally invasive US-guided tumor cell injection proved to be a better method compared to laparotomy due to the shorter recovery time required for the rabbits following injection. Among the rabbits that grew tumors, seven had tumors both inside and outside the prostate, three had tumors only inside the prostate, and four had tumors exclusively outside of the prostate. All tumors expressed the PSMA receptor. We have established, for the first time, an orthotopic PCa rabbit model via percutaneous US-guided tumor cell inoculation. This animal model is an attractive, clinically relevant intermediate step to assess preclinical diagnostic and therapeutic compounds.

Spatial analysis of histology in 3D: quantification and visualization of organ and tumor level tissue environment

Histological changes in tissue are of primary importance in pathological research and diagnosis. Automated histological analysis requires ability to computationally separate pathological alterations from normal tissue. Conventional histopathological assessments are performed from individual tissue sections, leading to the loss of three-dimensional context of the tissue. Yet, the tissue context and spatial determinants are critical in several pathologies, such as in understanding growth patterns of cancer in its local environment. Here, we develop computational methods for visualization and quantitative assessment of histopathological alterations in three dimensions. First, we reconstruct the 3D representation of the whole organ from serial sectioned tissue. Then, we proceed to analyze the histological characteristics and regions of interest in 3D. As our example cases, we use whole slide images representing hematoxylin-eosin stained whole mouse prostates in a Pten+/- mouse prostate tumor model. We show that quantitative assessment of tumor sizes, shapes, and separation between spatial locations within the organ enable characterizing and grouping tumors. Further, we show that 3D visualization of tissue with computationally quantified features provides an intuitive way to observe tissue pathology. Our results underline the heterogeneity in composition and cellular organization within individual tumors. As an example, we show how prostate tumors have nuclear density gradients indicating areas of tumor growth directions and reflecting varying pressure from the surrounding tissue. The methods presented here are applicable to any tissue and different types of pathologies. This work provides a proof-of-principle for gaining a comprehensive view from histology by studying it quantitatively in 3D.

Photosubstitution in a trisheteroleptic ruthenium complex inhibits conjunctival melanoma growth in a zebrafish orthotopic xenograft model

In vivo data are rare but essential for establishing the clinical potential of ruthenium-based photoactivated chemotherapy (PACT) compounds, a new family of phototherapeutic drugs that are activated via ligand photosubstitution. Here a novel trisheteroleptic ruthenium complex [Ru(dpp)(bpy)(mtmp)](PF6)2 ([2](PF6)2, dpp = 4,7-diphenyl-1,10-phenanthroline, bpy = 2,2′-bipyridine, mtmp = 2-methylthiomethylpyridine) was synthesized and its light-activated anticancer properties were validated in cancer cell monolayers, 3D tumor spheroids, and in embryonic zebrafish cancer models. Upon green light irradiation, the non-toxic mtmp ligand is selectively cleaved off, thereby releasing a phototoxic ruthenium-based photoproduct capable notably of binding to nuclear DNA and triggering DNA damage and apoptosis within 24–48 h. In vitro, fifteen minutes of green light irradiation (21 mW cm−2, 19 J cm−2, 520 nm) were sufficient to generate high phototherapeutic indexes (PI) for this compound in a range of cancer cell lines including lung (A549), prostate (PC3Pro4), conjunctival melanoma (CRMM1, CRMM2, CM2005.1) and uveal melanoma (OMM1, OMM2.5, Mel270) cancer cell lines. The therapeutic potential of [2](PF6)2 was further evaluated in zebrafish embryo ectopic (PC3Pro4) or orthotopic (CRMM1, CRMM2) tumour models. The ectopic model consisted of red fluorescent PC3Pro4-mCherry cells injected intravenously (IV) into zebrafish, that formed perivascular metastatic lesions at the posterior ventral end of caudal hematopoietic tissue (CHT). By contrast, in the orthotopic model, CRMM1- and CRMM2-mCherry cells were injected behind the eye where they developed primary lesions. The maximally-tolerated dose (MTD) of [2](PF6)2 was first determined for three different modes of compound administration: (i) incubating the fish in prodrug-containing water (WA); (ii) injecting the prodrug intravenously (IV) into the fish; or (iii) injecting the prodrug retro-orbitally (RO) into the fish. To test the anticancer efficiency of [2](PF6)2, the embryos were treated 24 h after engraftment at the MTD. Optimally, four consecutive PACT treatments were performed on engrafted embryos using 60 min drug-to-light intervals and 90 min green light irradiation (21 mW cm−2, 114 J cm−2, 520 nm). Most importantly, this PACT protocol was not toxic to the zebrafish. In the ectopic prostate tumour models, where [2](PF6)2 showed the highest photoindex in vitro (PI > 31), the PACT treatment did not significantly diminish the growth of primary lesions, while in both conjunctival melanoma orthotopic tumour models, where [2](PF6)2 showed more modest photoindexes (PI ∼ 9), retro-orbitally administered PACT treatment significantly inhibited growth of the engrafted tumors. Overall, this study represents the first demonstration in zebrafish cancer models of the clinical potential of ruthenium-based PACT, here against conjunctival melanoma.

Formulating RALA/Au nanocomplexes to enhance nanoparticle internalisation efficiency, sensitising prostate tumour models to radiation treatment

BackgroundGold nanoparticles (AuNP) are effective radiosensitisers, however, successful clinical translation has been impeded by short systemic circulation times and poor internalisation efficiency. This work examines the potential of RALA, a short amphipathic peptide, to enhance the uptake efficiency of negatively charged AuNPs in tumour cells, detailing the subsequent impact of AuNP internalisation on tumour cell radiation sensitivity.ResultsRALA/Au nanoparticles were formed by optimising the ratio of RALA to citrate capped AuNPs, with assembly occurring through electrostatic interactions. Physical nanoparticle characteristics were determined by UV–vis spectroscopy and dynamic light scattering. Nano-complexes successfully formed at w:w ratios > 20:1 (20 µg RALA:1 µg AuNP) yielding positively charged nanoparticles, sized < 110 nm with PDI values < 0.52. ICP-MS demonstrated that RALA enhanced AuNP internalisation by more than threefold in both PC-3 and DU145 prostate cancer cell models, without causing significant toxicity. Importantly, all RALA-AuNP formulations significantly increased prostate cancer cell radiosensitivity. This effect was greatest using the 25:1 RALA-AuNP formulation, producing a dose enhancement effect (DEF) of 1.54 in PC3 cells. Using clinical radiation energies (6 MV) RALA-AuNP also significantly augmented radiation sensitivity. Mechanistic studies support RALA-AuNP nuclear accumulation resulting in increased DNA damage yields.ConclusionsThis is the first study to demonstrate meaningful radiosensitisation using low microgram AuNP treatment concentrations. This effect was achieved using RALA, providing functional evidence to support our previous imaging study indicating RALA-AuNP nuclear accumulation.Graphic abstract

Ultrasound Molecular Imaging for the Guidance of Ultrasound-Triggered Release of Liposomal Doxorubicin and Its Treatment Monitoring in an Orthotopic Prostatic Tumor Model in Rat

Liposome encapsulation of drugs is an interesting approach in cancer therapy to specifically release the encapsulated drug at the desired treatment site. In addition to thermo-, pH-, light-, enzyme- or redox-responsive liposomes, which have had promising results in (pre-) clinical studies, ultrasound-triggered sonosensitive liposomes represent an exciting alternative to locally trigger the release from these cargos. Localized drug release requires precise tumor visualization to produce a targeted and ultrasound stimulus. We used ultrasound molecular imaging (USMI) with BR55, a vascular endothelial growth factor receptor 2 (VEGFR2)-targeted ultrasound contrast agent, to guide ultrasound-triggered release of sonosensitive liposomes encapsulating doxorubicin (L-DXR) in an orthotopic prostatic rodent tumor model. Forty-eight hours after L-DXR injection, local release of doxorubicin was triggered with a confocal ultrasound device with two focused transducers, 1.1-MHz center frequency, and peak positive and negative pressures of 20.5 and 13 MPa at focus. Tumor size decreased by 20% in 2 wk with L-DXR alone (n = 9) and by 70% after treatment with L-DXR and confocal ultrasound (n = 7) (p < 0.01). The effect of doxorubicin on perfusion/vascularity and VEGFR2 expression was evaluated by USMI and immunohistochemistry of CD31 and VEGFR2 and did not reveal differences in perfusion or VEGFR2 expression in the absence or after the triggered release of liposomes. USMI can provide precise guidance for ultrasound-triggered release of liposomal doxorubicin mediated by a confocal ultrasound device; moreover, the combination of B-mode imaging and USMI can help to follow the response of the tumor to the therapy.

Abstract 2641: Development of a 3D in vitro model of the prostate tumor microenvironment

Abstract Prostate cancer (PCa) is the most common occurring cancer in men and the second-most leading cause of cancer-related deaths in the United States. To improve patient outcome, research tools which mimic the prostate tumor microenvironment (TME) and accurately predict drug response are urgently needed. However, current in vitro PCa models do not recapitulate the complexities of the prostate TME including three-dimensional (3D) orientation, perfusion, extracellular matrix (ECM), and the presence of multiple cell types such as tumor cells, fibroblasts, and endothelium. Further, many complex in vitro model systems fail to maintain the throughput required for robust drug screening. To address this need, here, we highlight the stepwise development of a 3D in vitro PCa model by optimizing the individual culture conditions for each cell type (PCa cells, fibroblasts (FB), endothelial cells (EC)) within MIMETAS' high throughput perfusable 3D cell culture platform, the OrganoPlate® 2-lane 96. All monocultures (PCa, fibroblast, endothelial cell) were viable and expressed respective phenotypic markers (PCa: AR and PSA; FB: vimentin; EC: CD-31, VE-cadherin) as detected by immunofluorescent staining and high-content imaging. To demonstrate the statistical retention of heterogeneity within PCa populations, PCa cells (MDA-PCa-2b) were pre-labeled with 4 different tracking dyes and clustered into multicellular aggregates using a multiwell, ultra-low attachment plate. After 3D encapsulation within a migration permissive hyaluronic acid (MP-HA) hydrogel, PCa clusters retained uniform size clusters and even distribution of the pre-labeled populations within each cluster. Additionally, use of this pre-clustering reduced cell debris in the encapsulated 3D cultures. 3D FB cultures, mimicking normal or reactive stroma, were established with bone stroma cell lines and primary human mesenchymal stem cells. The cells' phenotypic stretched morphology and migration through the ECM were tuned by tailoring the hydrogel crosslinking assessed further by measuring the permeability of 2,000 kDa FITC-dextran. EC (primary human lung microvascular endothelium) were seeded against MP-HA to form a tubule structure within the perfusion channel. Culture conditions were optimized to reduce the permeability of smaller molecules (4.4, 150 KDa Dextran) through EC barriers and further imaging revealed the formation of a 3D blood vessel-like structure within the perfusion channel. Studies are ongoing to combine all three cell types into a single model. This stepwise approach, for building a complex, 3D prostate tumor model, will enable the full incorporation of all cell types and ECM into a single model which will have the potential to better recapitulate the in vivo prostate TME and improve the predictivity of PCa in vitro models. Citation Format: Divya Iyer, Andrei Bonteanu, Jedidiah Z. Zhu, Peter Shepherd, Rick Kittles, Nora M. Navone, Daniel A. Harrington, Dwayne Dexter, Kristin M. Bircsak. Development of a 3D in vitro model of the prostate tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2641.