Evaluation of chemotherapeutics in a three-dimensional breast cancer model

Evaluation of assays for drug efficacy in a three-dimensional model of the lung

Background

The focus of the outlined work is the establishment of a three-dimensional lung model for various drug-screening applications.

Methods

The non-small cell lung cancer (NSCLC) cell line Colo699 was cultivated as monolayer (2D) on plates for 5 days or as microtissues (3D) using a hanging-drop system for 5 and 10 days. Cells and microtissues were treated with afatinib (10–80 µM), cisplatin (100–800 µM) or vinorelbine (25–200 µM) for 24 or 48 hours (h). Cell proliferation and viability were analysed by intra-cellular adenosine triphosphate (ATP) and lactate dehydrogenase release (LDH) assays, annexin V/propidium iodide (PI) staining, and cell cycle determination. Microtissue morphology and size, as well as cell death were evaluated via phase contrast microscopy.

Results

Our results demonstrate the valid determination of viability and cell death using established assays in the 3D system for drug testing. The comparison of ATP, LDH and cytometry data showed moderate (0.40) to very strong (0.99) correlations. Thereby, we observed partially significant differences in drug efficacy between microtissues and 2D cultures dependent from the applied treatment and read-out method. Altogether, microtissues developed resistance to cisplatin and vinorelbine; but remained more vulnerable to afatinib. These findings were confirmed with microscopy.

Conclusion

In summary, we established an NSCLC 3D test system with multiple assays compatible for drug-testing applications of substances with different mechanisms of action. In addition, our data support the usage of microtissues as more accurate tools for drug-efficacy testing with the possibility of long-term cultivation and treatment.

Electronic supplementary material

The online version of this article (doi:10.1007/s00432-016-2198-0) contains supplementary material, which is available to authorized users.

An Evaluation of Matrix-Containing and Humanised Matrix-Free 3-Dimensional Cell Culture Systems for Studying Breast Cancer

BACKGROUND

3D cell cultures are emerging as more physiologically meaningful alternatives to monolayer cultures for many biological applications. They are attractive because they more closely mimic in vivo morphology, especially when co-cultured with stromal fibroblasts.

METHODOLOGY/PRINCIPAL FINDINGS

We compared the efficacy of 3 different 3D cell culture systems; collagen I, low attachment culture vessels and a modification of Fibrolife®, a specialised humanised cell culture medium devoid of animal-derived components, using breast cancer cell lines representative of the different molecular subtypes of breast cancer, cultured alone or with human mammary fibroblasts with a view to developing matrix-free humanised systems. 3D collagen I culture supported the growth of a range of breast cancer cell lines. By modifying the composition of Fibrolife® to epiFL, matrix-free cell culture was possible. During sequential transfer to epiFL breast cancer cells gradually detached from the flask, growing progressively as spheroids. Phenotype was stable and reversible with cells remaining actively proliferating and easily accessible throughout culture. They could also be revived from frozen stocks. To achieve co-culture with fibroblasts in epiFL required use of low attachment culture vessels instead of standard plastic as fibroblasts remained adherent in epiFL. Here, cancer cell spheroids were allowed to form before adding fibroblasts. Immunohistochemical examination showed fibroblasts scattered throughout the epithelial spheroid, not dissimilar to the relationship of tumour stroma in human breast cancer.

CONCLUSIONS

Because of its ease of handling, matrix-free 3D cell culture may be a useful model to study the influence of fibroblasts on breast cancer epithelial cells with use of epiFL culture medium taking this a step further towards a fully humanised 3D model. This methodology could be applied to other types of cancer cell lines, making this a versatile technique for cancer researchers wishing to use in vitro systems that better reflect cancer in vivo.

Bruton's Tyrosine Kinase Inhibitors Prevent Therapeutic Escape in Breast Cancer Cells

We have reported that a novel isoform of BTK (BTK-C) expressed in breast cancer protects these cells from apoptosis. In this study, we show that recently developed inhibitors of BTK, such as ibrutinib (PCI-32765), AVL-292, and CGI-1746, reduce breast cancer cell survival and prevent drug-resistant clones from arising. Ibrutinib treatment impacts HER2(+) breast cancer cell viability at lower concentrations than the established breast cancer therapeutic lapatinib. In addition to inhibiting BTK, ibrutinib, but not AVL-292 and CGI-1746, efficiently blocks the activation of EGFR, HER2, ErbB3, and ErbB4. Consequently, the activation of AKT and ERK signaling pathways are also blocked leading to a G1-S cell-cycle delay and increased apoptosis. Importantly, inhibition of BTK prevents activation of the AKT signaling pathway by NRG or EGF that has been shown to promote growth factor-driven lapatinib resistance in HER2(+) breast cancer cells. HER2(+) breast cancer cell proliferation is blocked by ibrutinib even in the presence of these factors. AVL-292, which has no effect on EGFR family activation, prevents NRG- and EGF-dependent growth factor-driven resistance to lapatinib in HER2(+) breast cancer cells. In vivo, ibrutinib inhibits HER2(+) xenograft tumor growth. Consistent with this, immunofluorescence analysis of xenograft tumors shows that ibrutinib reduces the phosphorylation of HER2, BTK, Akt, and Erk and histone H3 and increases cleaved caspase-3 signals. As BTK-C and HER2 are often coexpressed in human breast cancers, these observations indicate that BTK-C is a potential therapeutic target and that ibrutinib could be an effective drug especially for HER2(+) breast cancer. Mol Cancer Ther; 15(9); 2198-208. ©2016 AACR.

Photoactivated inhibition of cathepsin K in a 3D tumor model

Collagenolytic activity of cathepsin K is important for many physiological and pathological processes including osteoclast-mediated bone degradation, macrophage function and fibroblast-mediated matrix remodeling. Here, we report application of a light-activated inhibitor for controlling activity of cathepsin K in a 3D functional imaging assay. Using prostate carcinoma cell line engineered to overexpress cathepsin K, we demonstrate the utility of the proteolytic assay in living tumor spheroids for the evaluation and quantification of the inhibitor effects on cathepsin K-mediated collagen I degradation. Importantly, we also show that utilizing the ruthenium-caged version of a potent nitrile cathepsin K inhibitor (4), cis-[Ru(bpy)2(4)2](BF4)2 (5), offers significant advantage in terms of effective concentration of the inhibitor and especially its light-activated control in the 3D assay. Our results suggest that light activation provides a suitable, attractive approach for spatial and temporal control of proteolytic activity, which remains a critical, unmet need in treatment of human diseases, especially cancer.

Testing chemotherapy efficacy in HER2 negative breast cancer using patient-derived spheroids

BACKGROUND

Targeted anti-HER2 therapy has greatly improved the prognosis for many breast cancer patients. However, treatment for HER2 negative disease is currently still selected from a multitude of untargeted chemotherapeutic treatment options. A predictive test was developed using patient-derived spheroids to identify the most effective therapy for patients with HER2 negative breast cancer of all stages, for clinically relevant subgroups, as well as individual patients.

METHODS

Tumor samples from 120 HER2 negative patients obtained through biopsy or surgical excision were tested in the breast cancer spheroid model using scaffold-free cell culture. Similarly, spheroids were also generated from established HER2 negative breast cancer cell lines T-47D, MCF7, HCC1143, and HCC1937 to compare treatment efficacy of heterogeneous cell populations from patient tumor tissue with homogeneous cell lines. Spheroids were treated in vitro with guideline-recommended compounds. Treatment mediated impact on cell survival was subsequently quantified using an ATP assay.

RESULTS

Differences were observed in the metabolic activity of the untreated spheroids, whereby cell lines consistently achieved higher values compared to tissue spheroids (p < 0.001). A higher number of cells per spheroid correlated with a higher basal metabolic activity in tissue-derived spheroids (p < 0.01), while the opposite was observed for cell line spheroids (p < 0.01). Recurrent tumors showed a higher mean vitality (p < 0.01) compared to primary tumors. Except for taxanes, treatment efficacy for most tested compounds differed significantly between breast cancer tissue spheroids and breast cancer cell lines. Overall a high variability in treatment response in vitro was seen in the tissue spheroids regardless of the tested substances. A greater response to anthracycline/docetaxel was observed for hormone receptor negative samples (p < 0.01). A higher response to 5-FU (p < 0.01) and anthracycline (p < 0.05) was seen in high grade tumors. Smaller tumor size and negative lymph node status were both associated with a higher treatment efficacy to anthracycline treatment combined with 5-FU (cT1/2 vs cT3/4, p = 0.035, cN+ vs cN-, p < 0.05).

CONCLUSIONS

The tissue spheroid model reflects current guideline treatment recommendations for HER2 negative breast cancer, whereas tested cell lines did not. This model represents a unique diagnostic method to select the most effective therapy out of several equivalent treatment options.

Liquid-based three-dimensional tumor models for cancer research and drug discovery

Tumors are three-dimensional tissues where close contacts between cancer cells, intercellular interactions between cancer and stromal cells, adhesion of cancer cells to the extracellular matrix, and signaling of soluble factors modulate functions of cancer cells and their response to therapeutics. Three-dimensional cultures of cancer cells overcome limitations of traditionally used monolayer cultures and recreate essential characteristics of tumors such as spatial gradients of oxygen, growth factors, and metabolites and presence of necrotic, hypoxic, quiescent, and proliferative cells. As such, three-dimensional tumor models provide a valuable tool for cancer research and oncology drug discovery. Here, we describe different tumor models and primarily focus on a model known as tumor spheroid. We summarize different technologies of spheroid formation, and discuss the use of spheroids to address the influence of stromal fibroblasts and immune cells on cancer cells in tumor microenvironment, study cancer stem cells, and facilitate compound screening in the drug discovery process. We review major techniques for quantification of cellular responses to drugs and discuss challenges ahead to enable broad utility of tumor spheroids in research laboratories, integrate spheroid models into drug development and discovery pipeline, and use primary tumor cells for drug screening studies to realize personalized cancer treatment.

Three-dimensional culture systems in cancer research: Focus on tumor spheroid model

Cancer cells propagated in three-dimensional (3D) culture systems exhibit physiologically relevant cell-cell and cell-matrix interactions, gene expression and signaling pathway profiles, heterogeneity and structural complexity that reflect in vivo tumors. In recent years, development of various 3D models has improved the study of host-tumor interaction and use of high-throughput screening platforms for anti-cancer drug discovery and development. This review attempts to summarize the various 3D culture systems, with an emphasis on the most well characterized and widely applied model - multicellular tumor spheroids. This review also highlights the various techniques to generate tumor spheroids, methods to characterize them, and its applicability in cancer research.

Imaging Sites of Inhibition of Proteolysis in Pathomimetic Human Breast Cancer Cultures by Light-Activated Ruthenium Compound

The cysteine protease cathepsin B has been causally linked to progression and metastasis of breast cancers. We demonstrate inhibition by a dipeptidyl nitrile inhibitor (compound 1) of cathepsin B activity and also of pericellular degradation of dye-quenched collagen IV by living breast cancer cells. To image, localize and quantify collagen IV degradation in real-time we used 3D pathomimetic breast cancer models designed to mimic the in vivo microenvironment of breast cancers. We further report the synthesis and characterization of a caged version of compound 1, [Ru(bpy)₂(1)₂](BF₄)₂ (compound 2), which can be photoactivated with visible light. Upon light activation, compound 2, like compound 1, inhibited cathepsin B activity and pericellular collagen IV degradation by the 3D pathomimetic models of living breast cancer cells, without causing toxicity. We suggest that caged inhibitor 2 is a prototype for cathepsin B inhibitors that can control both the site and timing of inhibition in cancer.

Il-6 signaling between ductal carcinoma in situ cells and carcinoma-associated fibroblasts mediates tumor cell growth and migration

Background

Ductal carcinoma in situ (DCIS) is a non-obligate precursor lesion of invasive breast cancer in which approximately half the patients will progress to invasive cancer. Gaining a better understanding of DCIS progression may reduce overtreatment of patients. Expression of the pro-inflammatory cytokine interleukin-6 increases with pathological stage and grade, and is associated with poorer prognosis in breast cancer patients. Carcinoma associated fibroblasts (CAFs), which are present in the stroma of DCIS patients are known to secrete pro-inflammatory cytokines and promote tumor progression.

Methods

We hypothesized that IL-6 paracrine signaling between DCIS cells and CAFs mediates DCIS proliferation and migration. To test this hypothesis, we utilized the mammary architecture and microenvironment engineering or MAME model to study the interactions between human breast CAFs and human DCIS cells in 3D over time. We specifically inhibited autocrine and paracrine IL-6 signaling to determine its contribution to early stage tumor progression.

Results

Here, DCIS cells formed multicellular structures that exhibited increased proliferation and migration when cultured with CAFs. Treatment with an IL-6 neutralizing antibody inhibited growth and migration of the multicellular structures. Moreover, selective knockdown of IL-6 in CAFs, but not in DCIS cells, abrogated the migratory phenotype.

Conclusion

Our results suggest that paracrine IL-6 signaling between preinvasive DCIS cells and stromal CAFs represent an important factor in the initiation of DCIS progression to invasive breast carcinoma.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1576-3) contains supplementary material, which is available to authorized users.