Abstract 2988: Characterization of 3D models of human breast, prostate and colorectal cancer

Tumorigenic expression of programmed death-ligand 1 (PD-L1) and its receptor PD-1 is found in many cancers, though the intrinsic roles of these proteins and how immunotherapy treatment may affect these pathways needs to be fully explored across human cancers. One platform to assess the expression and regulation of these proteins is 3D cell culture, which is thought to more closely mimic the architecture of solid tumors and more closely recapitulate in vivo human tumors in terms of cell heterogeneity, immunological and tumorigenic marker expression and treatment response, to investigate PD-L1/PD-1 signaling in cancer cells. Human breast (MDA-MB-231 and MCF-7), prostate (LNCaP and PC3) and colorectal (SW480 and SW620) cancer cell lines were cultured in both scaffold-free and scaffold-based 3D cell culture models to facilitate the formation of spheroids that display cell heterogeneity. 3D cancer models were analyzed by microscopy, qPCR and flow cytometry to assess the viability of spheroids, and measure any alterations in immunological and tumorigenic markers at mRNA and protein level, respectively, compared to their 2D monolayer counterparts. Breast, prostate and colorectal cancer cells cultured in 3D were highly viable over time and displayed significantly altered levels of immunological and tumorigenic marker expression at mRNA and/or protein level compared to their 2D monolayer counterparts. Importantly, PD-L1 expression changed in a 3D environment which may be linked to the increased cell-cell and cell-ECM interactions; increased expression of PD-L1 regulatory genes/proteins; or hypoxic regions that establish in 3D spheroids. The significantly altered expression levels of immunological and tumorigenic markers in a 3D cell culture environment is more likely to mimic that of an in vivo human tumor than standard 2D cell culture; allowing for optimized in vitro evaluation of the role of tumorigenic PD-L1/PD-1 and how immunotherapy treatment may affect these pathways.

Citation Format: Katie Hudson, Neil Cross, Nicola Jordan-Mahy, Rebecca Leyland. Characterization of 3D models of human breast, prostate and colorectal cancer [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 2988.

Molecular Action of Polyphenols in Leukaemia and Their Therapeutic Potential

Leukaemia is a malignant disease of the blood. Current treatments for leukaemia are associated with serious side-effects. Plant-derived polyphenols have been identified as potent anti-cancer agents and have been shown to work synergistically with standard chemotherapy agents in leukaemia cell lines. Polyphenols have multiple mechanisms of action and have been reported to decrease cell proliferation, arrest cell cycle and induce apoptosis via the activation of caspase (3, 8 and 9); the loss of mitochondrial membrane potential and the release of cytochrome c. Polyphenols have been shown to suppress activation of transcription factors, including NF-kB and STAT3. Furthermore, polyphenols have pro-oxidant properties, with increasing evidence that polyphenols inhibit the antioxidant activity of glutathione, causing oxidative DNA damage. Polyphenols also induce autophagy-driven cancer cell death and regulate multidrug resistance proteins, and thus may be able to reverse resistance to chemotherapy agents. This review examines the molecular mechanism of action of polyphenols and discusses their potential therapeutic targets. Here, we discuss the pharmacological properties of polyphenols, including their anti-inflammatory, antioxidant, anti-proliferative, and anti-tumour activities, and suggest that polyphenols are potent natural agents that can be useful therapeutically; and discuss why data on bioavailability, toxicity and metabolism are essential to evaluate their clinical use.

The Extrinsic and Intrinsic Roles of PD-L1 and Its Receptor PD-1: Implications for Immunotherapy Treatment

Programmed death-ligand 1 (PD-L1) is an immune checkpoint inhibitor that binds to its receptor PD-1 expressed by T cells and other immune cells to regulate immune responses; ultimately preventing exacerbated activation and autoimmunity. Many tumors exploit this mechanism by overexpressing PD-L1 which often correlates with poor prognosis. Some tumors have also recently been shown to express PD-1. On tumors, PD-L1 binding to PD-1 on immune cells promotes immune evasion and tumor progression, primarily by inhibition of cytotoxic T lymphocyte effector function. PD-1/PD-L1-targeted therapy has revolutionized the cancer therapy landscape and has become the first-line treatment for some cancers, due to their ability to promote durable anti-tumor immune responses in select patients with advanced cancers. Despite this clinical success, some patients have shown to be unresponsive, hyperprogressive or develop resistance to PD-1/PD-L1-targeted therapy. The exact mechanisms for this are still unclear. This review will discuss the current status of PD-1/PD-L1-targeted therapy, oncogenic expression of PD-L1, the new and emerging tumor-intrinisic roles of PD-L1 and its receptor PD-1 and how they may contribute to tumor progression and immunotherapy responses as shown in different oncology models.

The use of auxetic materials in tissue engineering

A number of biological tissues have been reported as behaving in an auxetic manner, defined by a negative Poisson's ratio. This describes the deformation of tissue which expands in the axial and the transverse directions simultaneously while under uniaxial tension; and contracts axially and transversely upon uniaxial compression. The discovery of auxetic behaviour within biological tissues has implications for the recreation of the auxetic loading environment within tissue engineering. Tissue engineers strive to recreate the natural properties of biological tissue and in order to recreate the unique loading environment of cells from auxetic tissue, an auxetic scaffold is required. A number of studies have used a variety of auxetic scaffolds within tissue engineering. Investigation into the effect of auxetic micro-environments created by auxetic scaffolds on cellular behaviour has demonstrated an increased cellular proliferation and enhanced differentiation. Here, we discuss studies which have identified auxetic behaviour within biological tissues, and where cells have been cultured within auxetic scaffolds, bringing together current knowledge of the potential use of auxetic materials in tissue engineering applications and biomedical devices.

Use of l-pNIPAM hydrogel as a 3D-scaffold for intestinal crypts and stem cell tissue engineering

Intestinal stem cells hold great potential in tissue regeneration of the intestine, however, there are key limitations in their culture in vitro. We previously reported a novel synthetic non-biodegradable hydrogel as a 3D culture model for intestinal epithelium using Caco2 and HT29-MTX cells. Here, we investigated the potential of this system as a 3D scaffold for crypts and single intestinal stem cells to support long-term culture and differentiation. Intestinal crypts were extracted from murine small intestines and Lgr5+ stem cells isolated by magnetic activated cell sorting. Crypts and stem cells were suspended within Matrigel or l-pNIPAM for 14 days or suspended within Matrigel for 7 days then released, dissociated, and suspended within, or on l-pNIPAM hydrogel for 28 days. Cellular behaviour and phenotype were determined by histology and immunohistochemistry for stem cell and differentiation markers: Lgr5, E-cadherin MUC2 chromograninA and lysozymes. Isolated crypts and Lgr5+ intestinal stem cells formed enteroids with a central lumen surrounded by multiple crypt-like buds when cultured in Matrigel. In contrast, when crypts and stem cells were directly suspended within, or layered on l-pNIPAM hydrogel under dynamic culture conditions they formed spherical balls of cells, with no central lumen. When enteroids were initially formed in Matrigel from crypts or single Lgr5+ intestinal stem cells and dissociated into small fragments or single cells and transferred to l-pNIPAM hydrogel they formed new larger enteroids with numerous crypt-like buds. These crypt-like buds showed the presence of mucin-producing cells, which resembled goblet cells, scattered throughout their structures. Immunohistochemistry staining also showed the expression of Lgr5 and differentiation markers of all the main intestinal cell types including: enterocytes, goblet cells, enteroendocrine and Paneth cells. This demonstrated that l-pNIPAM hydrogel supported long-term culture of crypts and Lgr5+ stem cells and promoted intestinal cell differentiation.

Polyphenols enhance the activity of alkylating agents in leukaemia cell lines

Polyphenols have been shown to sensitize solid tumours to alkylating agents such as cisplatin, and induce apoptosis and/or cell-cycle arrest. Here, we assess the effects of five polyphenols alone and in combination with three alkylating agents: cisplatin, cyclophosphamide and chlorambucil in lymphoid and myeloid leukaemia cells lines, and non-tumour control cells. In lymphoid leukaemia cell lines there was a synergistic reduction in ATP and glutathione levels, an induction of cell cycle arrest, DNA damage and apoptosis when quercetin, apigenin, emodin and rhein were combined with cisplatin and cyclophosphamide; and when apigenin and rhein were combined with chlorambucil. In myeloid leukaemia cells quercetin, apigenin and emodin showed a similar synergistic effect with all alkylating agents; however antagonistic effects were observed with some or all alkylating agents when combined with emodin, rhein and cis-stilbene. All synergistic effects were associated with reduced glutathione levels, DNA damage and apoptosis; whilst during antagonism the reverse effects were observed. The combination of alkylating agents, particularly cisplatin with polyphenols could be promising for the treatment of lymphoid leukaemias, with apigenin showing the greatest effects. Likewise in myeloid cells apigenin also synergised the action of all alkylating agents, suggesting that apigenin may also be beneficial in myeloid leukaemias.

Interleukin 1 is a key driver of inflammatory bowel disease-demonstration in a murine IL-1Ra knockout model

Interleukin 1 (IL-1) is an important mediator of inflammation and tissue damage in inflammatory bowel disease (IBD). The balance between IL-1 and IL-1Ra as a natural inhibitor plays a vital role in a variety of diseases. Here, we investigated whether changes seen during IBD are induced spontaneously in mice lacking a functional IL-1rn gene. Histological staining was performed on the jejunum and ileum of BALB/c IL-1rn^+/+ and IL-1rn^-/- mice to characterize crypt-villus height, villus width, and number of goblet cells per villus. Pro-inflammatory cytokines, immune cell infiltration and matrix-degrading enzymes, together with the production of intestinal enzymes and the integrity of tight and adherent junction proteins were determined using immunohistochemistry. In the small intestine of BALB/c IL-1rn^-/- mice the villus heights were significantly reduced; and in the ileum this was accompanied by a decrease in villi width. There was also an increase in goblet cell number and mucin production compared to wild-type mice. IL-1α and IL-1β immunopositivity were increased, whilst IL-1R1 expression was decreased in IL-1rn^-/- mice. IL-15 and TNFα were also increased in older IL-1rn^-/- mice. Increased polymorphonuclear and macrophage infiltration were seen in IL-1rn^-/- mice, whilst expression of matrix-degrading enzymes and digestive enzymes were unchanged, except for dipeptidyl peptidase IV which was increased in younger IL-1rn^-/- mice compared to wild type mice. The expression of tight and adhesion junctions were also dramatically decreased in IL-1rn^-/- mice. In conclusion, IL-1rn^-/- mice developed spontaneous abnormalities which displayed features associated with IBD, demonstrating a clear role for IL-1 in IBD.

Long-term in vitro 3D hydrogel co-culture model of inflammatory bowel disease

The in vitro study of the pathogenesis of inflammatory bowel disease (IBD) requires a cell model which closely reflects the characteristics of the in vivo intestinal epithelium. This study aimed to investigate the application of L-pNIPAM hydrogel as a scaffold to develop a long-term 3D co-culture model of Caco-2 and HT29-MTX cells under conditions analogous to inflammation, to determine its potential use in studying IBD. Monocultures and co-cultures were layered on L-pNIPAM hydrogel scaffolds and maintained under dynamic culture conditions for up to 12 weeks. Treatments with IL-1β, TNFα, and hypoxia for 1 week were used to create an inflammatory environment. Following prolonged culture, the metabolic activity of Caco-2 monoculture and 90% Caco-2/10% HT29-MTX co-cultures on L-pNIPAM hydrogels were increased, and finger-like structures, similar in appearance to villi were observed. Following treatment with IL-1β, TNFα and hypoxia, ALP and ZO-1 were decreased, MUC2 increased, and MUC5AC remained unchanged. ADAMTS1 was increased in response to hypoxia. Caspase 3 expression was increased in response to TNFα and hypoxic conditions. In conclusion, L-pNIPAM hydrogel supported long-term co-culture within a 3D model. Furthermore, stimulation with factors seen during inflammation recapitulated features seen during IBD.

Dietary polyphenols influence antimetabolite agents: methotrexate, 6-mercaptopurine and 5-fluorouracil in leukemia cell lines

Polyphenols have been previously shown to sensitize leukemia cell lines to topoisomerase inhibitors. Here, we assess the effects of five polyphenols when used alone and in combination with antimetabolites: methotrexate, 6-mercaptopurine and 5-fluorouracil; in lymphoid and myeloid leukemia cells lines, and non-tumor control cells. The effects of combined treatments were investigated on ATP and glutathione levels, cell-cycle progression, DNA damage and apoptosis.

Polyphenols antagonized methotrexate and 6-mercaptopurine induced cell-cycle arrest and apoptosis in most leukemia cell lines. This was associated with reduced DNA damage and increased glutathione levels, greater than that seen following individual treatments alone.

In contrast, 5-fluorouracil when combined with quercetin, apigenin and rhein caused synergistic decrease in ATP levels, induction of cell-cycle arrest and apoptosis in some leukemia cell lines. However, antagonistic effects were observed when 5-fluorouracil was combined with rhein and cis-stilbene in myeloid cell lines. The effects were dependant on polyphenol type and chemotherapy agent investigated, and cell type treated. Interestingly treatment of non-tumor control cells with polyphenols protected cells from antimetabolite treatments.

This suggests that polyphenols modulate the action of antimetabolite agents; more importantly they antagonized methotrexate and 6-mercaptopurine actions, thus suggesting the requirement of polyphenol-exclusion during their use.

Polyphenols act synergistically with doxorubicin and etoposide in leukaemia cell lines

The study aimed to assess the effects of polyphenols when used in combination with doxorubicin and etoposide, and to determine whether polyphenols sensitised leukaemia cells, causing inhibition of cell proliferation, cell cycle arrest and induction of apoptosis. This study is based on findings in solid cancer tumours, which have shown that polyphenols can sensitize cells to chemotherapy, and induce apoptosis and/or cell-cycle arrest. This could enable a reduction of chemotherapy dose and off-target effects, whilst maintaining treatment efficacy. Quercetin, apigenin, emodin, rhein and cis-stilbene were investigated alone and in combination with etoposide and doxorubicin in two lymphoid and two myeloid leukaemia cells lines. Measurements were made of ATP levels (using CellTiter-Glo assay) as an indication of total cell number, cell cycle progression (using propidium iodide staining and flow cytometry) and apoptosis (NucView caspase 3 assay and Hoechst 33342/propidium iodide staining). Effects of combination treatments on caspases 3, 8 and 9 activity were determined using Glo luminescent assays, glutathione levels were measured using the GSH-Glo Glutathione Assay and DNA damage determined by anti-γH2AX staining. Doxorubicin and etoposide in combination with polyphenols synergistically reduced ATP levels, induced apoptosis and increased S and/or G₂/M phase cell cycle arrest in lymphoid leukaemia cell lines. However, in the myeloid cell lines the effects of the combination treatments varied; doxorubicin had a synergistic or additive effect when combined with quercetin, apigenin, emodin, and cis-stilbene, but had an antagonistic effect when combined with rhein. Combination treatment caused a synergistic downregulation of glutathione levels and increased DNA damage, driving apoptosis via caspase 8 and 9 activation. However, in myeloid cells where antagonistic effects were observed, this was associated with increased glutathione levels and a reduction in DNA damage and apoptosis. This study has demonstrated that doxorubicin and etoposide activity were enhanced by polyphenols in lymphoid leukaemia cells, however, differential responses were seen in myeloid cells with antagonistic responses seen in some combination therapies.

Differential effects of polyphenols on proliferation and apoptosis in human myeloid and lymphoid leukemia cell lines

BACKGROUND

Mortality rates for leukemia are high despite considerable improvements in treatment. Since polyphenols exert pro-apoptotic effects in solid tumors, our study investigated the effects of polyphenols in haematological malignancies. The effect of eight polyphenols (quercetin, chrysin, apigenin, emodin, aloe-emodin, rhein, cis-stilbene and trans-stilbene) were studied on cell proliferation, cell cycle and apoptosis in four lymphoid and four myeloid leukemic cells lines, together with normal haematopoietic control cells.

METHODS

Cellular proliferation was measured by CellTiter-Glo(®) luminescent assay; and cell cycle arrest was assessed using flow cytometry of propidium iodide stained cells. Apoptosis was investigated by caspase-3 activity assay using flow cytometry and apoptotic morphology was confirmed by Hoescht 33342 staining.

RESULTS

Emodin, quercetin, and cis-stilbene were the most effective polyphenols at decreasing cell viability (IC50 values of 5-22 μM, 8-33 μM, and 25-85 μM respectively) and inducing apoptosis (AP50 values (the concentration which 50% of cells undergo apoptosis) of 2-27 μM, 19-50 μM, and 8-50 μM respectively). Generally, lymphoid cell lines were more sensitive to polyphenol treatment compared to myeloid cell lines, however the most resistant myeloid (KG-1a and K562) cell lines were still found to respond to emodin and quercetin treatment at low micromolar levels. Non-tumor cells were less sensitive to all polyphenols compared to the leukemia cells.

CONCLUSIONS

These findings suggest that polyphenols have anti-tumor activity against leukemia cells with differential effects. Importantly, the differential sensitivity of emodin, quercetin, and cis-stilbene between leukemia and normal cells suggests that polyphenols are potential therapeutic agents for leukemia.

Polyphenols are responsible for the proapoptotic properties of pomegranate juice on leukemia cell lines

Pomegranates have shown great promise as anti-cancer agents in a number of cancers including clinical trials in prostate cancer. We have previously shown pomegranate juice (PGJ) induced apoptosis and preferentially alters the cell cycle in leukemia cell lines compared with nontumor control cells. However, the agents responsible have not yet been fully elucidated. Treatment of four leukemia cell lines with five fractions obtained from PGJ by solid phase extraction demonstrated that only the acetonitrile fractions decreased adenosine triphosphate (ATP) levels in all leukemia cell lines. Acetonitrile fractions also significantly activated caspase-3 and induced nuclear morphology characteristic of apoptosis. S phase arrest was induced by acetonitrile fractions which matched S phase arrest seen previously following whole PGJ treatments. The acetonitrile fractions contained higher phenol content than whole PGJ whereas only low levels of phenols were seen in any other fraction. Liquid chromatography mass spectrometry (LC–MS) analysis demonstrated that acetonitrile fractions were enriched in ellagitannins, ellagic acid, and hydroxycinnamic acid derivatives but depleted in anthocyanins. Individual treatments with identified compounds demonstrated that the ellagitannin: punicalagin was the most active and mimicked the responses seen following acetonitrile fraction treatment. Bioactive components within pomegranate were confined to the acetonitrile fraction of PGJ. The enrichment in ellagitannins and hydroxycinnamic acids suggest these may provide the majority of the bioactivities of PGJ. Individual treatments with compounds identified demonstrated that the ellagitannin: punicalagin was the most active agent, highlighting this compound as a key bioactive agent in PGJ.

Bioactive actions of pomegranate fruit extracts on leukemia cell lines in vitro hold promise for new therapeutic agents for leukemia

Studies suggest that pomegranates contain bioactive chemicals with potential for treatment and prevention of cancer. Pomegranate juice extracts (PJE) have been shown to inhibit cellular proliferation and tumor growth and induce cell death via apoptosis in a number of cancer cell lines. However, to date, few studies have investigated the potential of PJE in the treatment of leukemia. We investigated the potential effect of PJE on induction of apoptosis and inhibition of cellular proliferation in 8 leukemia cell lines (4 lymphoid and 4 myeloid) and nontumor hematopoietic stem cells (control cells). Apoptosis was assessed by 2 methods: Annexin V-FITC/propidium iodide staining with flow cytometric analysis and 4'-6-diamidino-2-phenylindole (DAPI) morphological assessment. Cell cycle stage was investigated using propidum iodide staining of DNA content and flow cytometric analysis. Live cell counts were also performed using a trypan exclusion assay. PJE significantly induced apoptosis in all cell lines, including nontumor control cells, although lymphoid cells and 2 of the myeloid cell lines were more sensitive. Furthermore, PJE induced cell cycle arrest. These results were confirmed by DAPI analysis and viable cell counts using trypan blue exclusion assay. Our results provide evidence that PJE contain bioactive compounds that could be used in the treatment of leukemia.