Comparison of methods for the isolation of human breast epithelial and myoepithelial cells

Optimization of mouse kidney digestion protocols for single-cell applications

Single-cell technologies such as flow cytometry and single-cell RNA sequencing have allowed for comprehensive characterization of the kidney cellulome. However, there is a disparity in the various protocols for preparing kidney single-cell suspensions. We aimed to address this limitation by characterizing kidney cellular heterogeneity using three previously published single-cell preparation protocols. Single-cell suspensions were prepared from male and female C57BL/6 kidneys using the following kidney tissue dissociation protocols: a scRNAseq protocol (P1), a multi-tissue digestion kit from Miltenyi Biotec (P2), and a protocol established in our laboratory (P3). Following dissociation, flow cytometry was used to identify known major cell types including leukocytes (myeloid and lymphoid), vascular cells (smooth muscle and endothelial), nephron epithelial cells (intercalating, principal, proximal, and distal tubule cells), podocytes, and fibroblasts. Of the protocols tested, P2 yielded significantly less leukocytes and type B intercalating cells compared with the other techniques. P1 and P3 produced similar yields for most cell types; however, endothelial and myeloid-derived cells were significantly enriched using P1. Significant sex differences were detected in only two cell types: granulocytes (increased in males) and smooth muscle cells (increased in females). Future single-cell studies that aim to enrich specific kidney cell types may benefit from this comparative analysis.NEW & NOTEWORTHY This study is the first to evaluate published single-cell suspension preparation protocols and their ability to produce high-quality cellular yields from the mouse kidney. Three single-cell digestion protocols were compared and each produced significant differences in kidney cellular heterogeneity. These findings highlight the importance of the digestion protocol when using single-cell technologies. This study may help future single-cell science research by guiding researchers to choose protocols that enrich certain cell types of interest.

Navigating challenges: optimising methods for primary cell culture isolation

Primary cell lines are invaluable for exploring cancer biology and investigating novel treatments. Despite their numerous advantages, primary cultures are laborious to obtain and maintain in culture. Hence, established cell lines are still more common. This study aimed to evaluate a range of techniques for isolating primary breast cancer cultures, employing distinct enzymatic compositions, incubation durations, and mechanical approaches, including filtration. Out of several protocols, we opted for a highly effective method (Method 5) that gave rise to a primary cell culture (BC160). This method combines mechanical disaggregation and enzymatic digestion with hyaluronidase and collagenase. Moreover, the paper addresses common issues in isolating primary cultures, shedding light on the struggle against fibroblasts overgrowing cancer cell populations. To make primary cell lines a preferred model, it is essential to elaborate and categorise isolation methods, develop approaches to separate heterogeneous cultures and investigate factors influencing the establishment of primary cell lines.

Fibroblast Isolation from Mammary Gland Tissue and Syngeneic Murine Breast Cancer Models

Cancer-associated fibroblasts (CAFs) are vital within the tumor ecosystem, regulating tumor growth, dissemination, and response to therapy through crosstalk with tumor cells, infiltrating immune and vascular cells, as well as components of the extracellular matrix (ECM). CAFs have thus emerged as potential therapeutic targets to complement cancer cell-targeted therapies. To study CAF-tumor cell crosstalk ex vivo, robust isolation methods of primary CAFs are required. Here, we present protocols to isolate, expand, and culture two types of fibroblasts: (1) healthy murine mammary gland fibroblasts, a key source of the CAF population in breast tumor models and (2) CAFs derived from syngeneic murine breast tumors. Isolated mammary fibroblasts and CAFs are suitable for use in a variety of downstream cellular and molecular experiments. We expect these methods to be useful to scientists studying the properties of fibroblasts and CAFs and the interaction between CAFs and the various components of the tumor microenvironment (TME).

Cell culture of the normal human mammary gland cultivated in monolayer - A mini systematic review

The mammary glands are constituted of different cell types. For example, the epithelial cells appear as the target in many studies since they produce and secrete milk during lactation and are the origin of many human breast cancers. Mammary gland biology is characterized by dynamic tissue growth, function and regression phases, which are understood mainly due to tissue culture studies. Cell culture is probably one of the most used in vitro scientific models, and the most common research model is still the two-dimensional (2D) culture system. Different approaches and conditions have been tested and used to improve the isolation, growth, yield and maintenance of viability of mammary gland cells. Therefore, our study aimed to explore and summarize the cell culture techniques with normal human mammary gland cells cultured in a monolayer. A search strategy was conducted using the electronic databases 'PubMed', 'Scopus' and 'Virtual Health Library'. The search was carried out using the keywords 'cell culture' and 'mammary gland' and 'human'. The main search was carried out by two authors between July and August 2021. In addition, we performed a review matrix elaborated in a spreadsheet to organize and systematize information about each article for inclusion. A total of 11 studies were included in the review and have conducted qualitative analyses on them. Although studies of these cells have been reported since the 1970 s, most found are from the last decade and are largely carried out in the USA. In addition, it was possible to verify the Human Mammary Epithelial Cells (HMEC) primary culture obtained from breast surgery as the main cell type studied. These cells are cultivated in Dulbecco's Modified Eagle Medium (DMEM) and M87A medium with diverse supplements. Finally, there was a diversity in the use of dissociation reagents and a lack of information about cryopreservation. We have observed detailed methodological information about these study models, which would propose further investigations.

Label-free isolation and cultivation of patient-matched human mammary epithelial and stromal cells from normal breast tissue

Breast cancer is primarily derived from mammary epithelial cells, the main cell type in human mammary glands. The majority of knowledge gained thus far around breast cancer has come from research using immortalized epithelial cell lines. The use of primary cells derived from breast tissue can be used in research to provide more biological relevance representative of the heterogeneous nature of breast cancer development and metastasis in its natural microenvironment. However, the successful isolation and propagation of human primary mammary gland cells can be costly and difficult due to their complex in vivo microenvironment and sensitivity when isolated. Here, we present a gentle isolation method for viable human mammary epithelial cells (hMECs) and donor-matched human mammary fibroblasts (hMFbs) from human mammary gland tissue. We isolated, expanded and passaged the hMECs and hMFbs in vitro and characterized cultures using cell-specific markers. A total of four primary cell lines were isolated and established from normal breast tissue and characterized through various markers, including pan cytokeratin (panCK), CK14, CD44, CD31, fibronectin and vimentin by immunofluorescence. To determine functional potential for subsequent studies, epithelial cells were examined via Matrigel® assays to assess spheroid development. Both cell type cultures expressed lineage specific markers with hMECs but not hMFbs forming spheroid structures in 3D Matrigel® assays. Our analyses confirm the successful isolation of two different cell phenotypes from normal breast tissues. This robust technique provides an inexpensive and accessible approach for mammary cell isolation.

From Donor to the Lab: A Fascinating Journey of Primary Cell Lines

Primary cancer cell lines are ex vivo cell cultures originating from resected tissues during biopsies and surgeries. Primary cell cultures are objects of intense research due to their high impact on molecular biology and oncology advancement. Initially, the patient-derived specimen must be subjected to dissociation and isolation. Techniques for tumour dissociation are usually reliant on the organisation of connecting tissue. The most common methods include enzymatic digestion (with collagenase, dispase, and DNase), chemical treatment (with ethylene diamine tetraacetic acid and ethylene glycol tetraacetic acid), or mechanical disaggregation to obtain a uniform cell population. Cells isolated from the tissue specimen are cultured as a monolayer or three-dimensional culture, in the form of multicellular spheroids, scaffold-based cultures (i.e., organoids), or matrix-embedded cultures. Every primary cell line must be characterised to identify its origin, purity, and significant features. The process of characterisation should include different assays utilising specific (extra- and intracellular) markers. The most frequently used approaches comprise immunohistochemistry, immunocytochemistry, western blot, flow cytometry, real-time polymerase chain reaction, karyotyping, confocal microscopy, and next-generation sequencing. The growing body of evidence indicates the validity of the usage of primary cancer cell lines in the formulation of novel anti-cancer treatments and their contribution to drug development.

Flower isoforms promote competitive growth in cancer

In humans, the adaptive immune system uses the exchange of information between cells to detect and eliminate foreign or damaged cells; however, the removal of unwanted cells does not always require an adaptive immune system^1,2. For example, cell selection in Drosophila uses a cell selection mechanism based on 'fitness fingerprints', which allow it to delay ageing³, prevent developmental malformations^3,4 and replace old tissues during regeneration⁵. At the molecular level, these fitness fingerprints consist of combinations of Flower membrane proteins^3,4,6. Proteins that indicate reduced fitness are called Flower-Lose, because they are expressed in cells marked to be eliminated⁶. However, the presence of Flower-Lose isoforms at a cell's membrane does not always lead to elimination, because if neighbouring cells have similar levels of Lose proteins, the cell will not be killed^4,6,7. Humans could benefit from the capability to recognize unfit cells, because accumulation of damaged but viable cells during development and ageing causes organ dysfunction and disease^8-17. However, in Drosophila this mechanism is hijacked by premalignant cells to gain a competitive growth advantage¹⁸. This would be undesirable for humans because it might make tumours more aggressive^19-21. It is unknown whether a similar mechanism of cell-fitness comparison is present in humans. Here we show that two human Flower isoforms (hFWE1 and hFWE3) behave as Flower-Lose proteins, whereas the other two isoforms (hFWE2 and hFWE4) behave as Flower-Win proteins. The latter give cells a competitive advantage over cells expressing Lose isoforms, but Lose-expressing cells are not eliminated if their neighbours express similar levels of Lose isoforms; these proteins therefore act as fitness fingerprints. Moreover, human cancer cells show increased Win isoform expression and proliferate in the presence of Lose-expressing stroma, which confers a competitive growth advantage on the cancer cells. Inhibition of the expression of Flower proteins reduces tumour growth and metastasis, and induces sensitivity to chemotherapy. Our results show that ancient mechanisms of cell recognition and selection are active in humans and affect oncogenic growth.

Application of Cancer Organoid Model for Drug Screening and Personalized Therapy

Drug screening—i.e., testing the effects of a number of drugs in multiple cell lines—is used for drug discovery and development, and can also be performed to evaluate the heterogeneity of a disease entity. Notably, intertumoral heterogeneity is a large hurdle to overcome for establishing standard cancer treatment, necessitating disease models better than conventional established 2D cell lines for screening novel treatment candidates. In the present review, we outline recent progress regarding experimental cancer models having more physiological and clinical relevance for drug screening, which are important for the successful evaluation of cellular response to drugs. The review is particularly focused on drug screening using the cancer organoid model, which is emerging as a better physiological disease model than conventional established 2D cell lines. We also review the use of cancer organoids to examine intertumor and intratumor heterogeneity, and introduce the perspective of the clinical use of cancer organoids to enable precision medicine.

Expanding and characterizing esophageal epithelial cells obtained from children with eosinophilic esophagitis

BACKGROUND

The role of epithelial cells in eosinophilic esophagitis (EoE) is not well understood. In this study, our aim was to isolate, culture, and expand esophageal epithelial cells obtained from patients with or without EoE and characterize differences observed over time in culture.

METHODS

Biopsies were obtained at the time of endoscopy from children with EoE or suspected to have EoE. We established patient-derived esophageal epithelial cell (PDEEC) lines utilizing conditional reprogramming methods. We determined integrin profiles, gene expression, MHC class II expression, and reactivity to antigen stimulation.

RESULTS

The PDEECs were found to maintain their phenotype over several passages. There were differences in integrin profiles and gene expression levels in EoE-Active compared to normal controls and EoE-Remission patients. Once stimulated with antigens, PDEECs express MHC class II molecules on their surface, and when co-cultured with autologous T-cells, there is increased IL-6 and TNF-α secretion in EoE-Active patients vs. controls.

CONCLUSION

We are able to isolate, culture, and expand esophageal epithelial cells from pediatric patients with and without EoE. Once stimulated with antigens, these cells express MHC class II molecules and behave as non-professional antigen-presenting cells. This method will help us in developing an ex vivo, individualized, patient-specific model for diagnostic testing for causative antigens.

Glucocorticoids promote transition of ductal carcinoma in situ to invasive ductal carcinoma by inducing myoepithelial cell apoptosis

BACKGROUND

The microenvironment and stress factors like glucocorticoids have a strong influence on breast cancer progression but their role in the first stages of breast cancer and, particularly, in myoepithelial cell regulation remains unclear. Consequently, we investigated the role of glucocorticoids in ductal carcinoma in situ (DCIS) in breast cancer, focusing specially on myoepithelial cells.

METHODS

To clarify the role of glucocorticoids at breast cancer onset, we evaluated the effects of cortisol and corticosterone on epithelial and myoepithelial cells using 2D and 3D in vitro and in vivo approaches and human samples.

RESULTS

Glucocorticoids induce a reduction in laminin levels and favour the disruption of the basement membrane by promotion of myoepithelial cell apoptosis in vitro. In an in vivo stress murine model, increased corticosterone levels fostered the transition from DCIS to invasive ductal carcinoma (IDC) via myoepithelial cell apoptosis and disappearance of the basement membrane. RU486 is able to partially block the effects of cortisol in vitro and in vivo. We found that myoepithelial cell apoptosis is more frequent in patients with DCIS+IDC than in patients with DCIS.

CONCLUSIONS

Our findings show that physiological stress, through increased glucocorticoid blood levels, promotes the transition from DCIS to IDC, particularly by inducing myoepithelial cell apoptosis. Since this would be a prerequisite for invasive features in patients with DCIS breast cancer, its clinical management could help to prevent breast cancer progression to IDC.

Conditional Reprogramming of Pediatric Human Esophageal Epithelial Cells for Use in Tissue Engineering and Disease Investigation

Identifying and expanding patient-specific cells in culture for use in tissue engineering and disease investigation can be very challenging. Utilizing various types of stem cells to derive cell types of interest is often costly, time consuming and highly inefficient. Furthermore, undesired cell types must be removed prior to using this cell source, which requires another step in the process. In order to obtain enough esophageal epithelial cells to engineer the lumen of an esophageal construct or to screen therapeutic approaches for treating esophageal disease, native esophageal epithelial cells must be expanded without altering their gene expression or phenotype. Conditional reprogramming of esophageal epithelial tissue offers a promising approach to expanding patient-specific esophageal epithelial cells. Furthermore, these cells do not need to be sorted or purified and will return to a mature epithelial state after removing them from conditional reprogramming culture. This technique has been described in many cancer screening studies and allows for indefinite expansion of these cells over multiple passages. The ability to perform esophageal screening assays would help revolutionize the treatment of pediatric esophageal diseases like eosinophilic esophagitis by identifying the trigger mechanism causing the patient's symptoms. For those patients who suffer from congenital defect, disease or injury of the esophagus, this cell source could be used as a means to seed a synthetic construct for implantation to repair or replace the affected region.

Amplexicaule A exerts anti-tumor effects by inducing apoptosis in human breast cancer

Chemotherapy is the main treatment for patients with breast cancer metastases, but natural alternatives have been receiving attention for their potential as novel anti-tumor reagents. Amplexicaule A (APA) is a flavonoid glucoside isolated from rhizomes of Polygonum amplexicaule D. Don var. sinense Forb (PADF). We found that APA has anti-tumor effects in a breast cancer xenograft mouse model and induces apoptosis in breast cancer cell lines. APA increased levels of cleaved caspase-3,-8,-9 and PARP, which resulted from suppression of MCL-1 and BCL-2 expression in the cells. APA also inactivated the Akt/mTOR pathway in breast cancer cells. Thus, APA exerts a strong anti-tumor effect on breast cancer cells, most likely through induction of apoptosis. Our study is the first to identify this novel anti-tumor compound and provides a new strategy for isolation and separation of single compounds from herbs.

S100A4 (metastasin) positive mesenchymal canine mammary tumour spheroids reduce Tenascin C synthesis under DMSO exposure in vitro

In breast cancer research S100A4-positive tumour-associated stromal cells are assumed as primary source of Tenascin C (TNC) in the metastatic environment. Aim of the present study was to isolate and characterize S100A4/TNC positive stromal canine mammary tumour (CMT) cells. Cells grown as scaffold-free spheroids were investigated for S100A4, TNC, and proliferative activity under 1.8% DMSO stimulation by means of Western blot and immunohistochemistry. DMSO is a commonly used drug solvent despite well-known side effects on cells including TNC expression. DMSO did not affect proliferation, but TNC was significantly reduced under DMSO exposure for 7 and 14 days, whereby for S100A4 a reducing effect was only observed after 14 days. Without DMSO, cells stably expressed TNC and S100A4 which makes them suitable to be used in experimental approaches requiring S100A4/TNC expressing CMT stromal cells. Results show that 1.8% DMSO should not be used as solvent for experiments concerning TNC/S100A4 expression.

In vitro model for DNA double-strand break repair analysis in breast cancer reveals cell type-specific associations with age and prognosis

Dysfunction of homologous recombination is a common denominator of changes associated with breast cancer-predisposing mutations. In our previous work, we identified a functional signature in peripheral blood lymphocytes from women who were predisposed that indicated a shift from homologous recombination to alternative, error-prone DNA double-strand break (DSB) repair pathways. To capture both hereditary and nonhereditary factors, we newly established a protocol for isolation and ex vivo analysis of epithelial cells, epithelial-mesenchymal transition cells (EMTs), and fibroblasts from breast cancer specimens (147 patients). By applying a fluorescence-based test system, we analyzed the error-prone DSB repair pathway microhomology-mediated end joining in these tumor-derived cell types and peripheral blood lymphocytes. In parallel, we investigated DNA lesion processing by quantitative immunofluorescence microscopy of histone H2AX phosphorylated on Ser139 focus after radiomimetic treatment. Our study reveals elevated histone H2AX phosphorylated on Ser139 damage removal in epithelial cells, not EMTs, and poly(ADP-ribose)polymerase inhibitor sensitivities, which suggested a DSB repair pathway shift with increasing patient age. Of interest, we found elevated microhomology-mediated end joining in EMTs, not epithelial cells, from patients who received a treatment recommendation of adjuvant chemotherapy, that is, those with high-risk tumors. Our discoveries of altered DSB repair activities in cells may serve as a method to further classify breast cancer to predict responsiveness to adjuvant chemotherapy and/or therapeutics that target DSB repair-dysfunctional tumors.-Deniz, M., Kaufmann, J., Stahl, A., Gundelach, T., Janni, W., Hoffmann, I., Keimling, M., Hampp, S., Ihle, M., Wiesmüller, L. In vitro model for DNA double-strand break repair analysis in breast cancer reveals cell type-specific associations with age and prognosis.

Molecular Portrait of the Normal Human Breast Tissue and Its Influence on Breast Carcinogenesis

Normal human breast tissue consists of epithelial and nonepithelial cells with different molecular profiles and differentiation grades. This molecular heterogeneity is known to yield abnormal clones that may contribute to the development of breast carcinomas. Stem cells that are found in developing and mature breast tissue are either positive or negative for cytokeratin 19 depending on their subtype. These cells are able to generate carcinogenesis along with mature cells. However, scientific data remains controversial regarding the monoclonal or polyclonal origin of breast carcinomas. The majority of breast carcinomas originate from epithelial cells that normally express BRCA1. The consecutive loss of the BRCA1 gene leads to various abnormalities in epithelial cells. Normal breast epithelial cells also express hypoxia inducible factor (HIF) 1α and HIF-2α that are associated with a high metastatic rate and a poor prognosis for malignant lesions. The nuclear expression of estrogen receptor (ER) and progesterone receptor (PR) in normal human breast tissue is maintained in malignant tissue as well. Several controversies regarding the ability of ER and PR status to predict breast cancer outcome remain. Both ER and PR act as modulators of cell activity in normal human breast tissue. Ki-67 positivity is strongly correlated with tumor grade although its specific role in applied therapy requires further studies. Human epidermal growth factor receptor 2 (HER2) oncoprotein is less expressed in normal human breast specimens but is highly expressed in certain malignant lesions of the breast. Unlike HER2, epidermal growth factor receptor expression is similar in both normal and malignant tissues. Molecular heterogeneity is not only found in breast carcinomas but also in normal breast tissue. Therefore, the molecular mapping of normal human breast tissue might represent a key research area to fully elucidate the mechanisms of breast carcinogenesis.

Breast primary epithelial cells that escape p16-dependent stasis enter a telomere-driven crisis state

Breast cancer is the most common malignant disease in women, but some basic questions remain in breast cancer biology. To answer these, several cell models were developed. Recently, the use of improved cell-culture conditions has enabled the development of a new primary cell model with certain luminal characteristics. This model is relevant because, after the introduction of a specific set of genetic elements, the transformed cells yielded tumors resembling human adenocarcinomas in mice. The use of improved cell-culture conditions supporting the growth of these breast primary epithelial cells was expected to delay or eliminate stress-induced senescence and lead to the propagation of normal cells. However, no studies have been carried out to investigate these points. Propagation of breast primary epithelial cells was performed in WIT medium on Primaria plates. Immunofluorescence, western blot and qRT-PCR were used to detect molecular markers, and to determine the integrity of DNA damage-response pathways. Promoter methylation of p16 (INK4a) was assessed by pyrosequencing. In order to obtain a dynamic picture of chromosome instability over time in culture, we applied FISH methodologies. To better link chromosome instability with excessive telomere attrition, we introduced the telomerase reverse transcriptase human gene using a lentiviral vector. We report here that breast primary epithelial cells propagated in vitro with WIT medium on Primaria plates express some luminal characteristics, but not a complete luminal lineage phenotype. They undergo a p16-dependent stress-induced senescence (stasis), and the cells that escape stasis finally enter a crisis state with rampant chromosome instability. Chromosome instability in these cells is driven by excessive telomere attrition, as distributions of chromosomes involved in aberrations correlate with the profiles of telomere signal-free ends. Importantly, ectopic expression of the human TERT gene rescued their chromosomal instability phenotype. Essentially, our data show that contrary to what was previously suggested, improved culture conditions to propagate in vitro mammary epithelial cells with some luminal characteristics do not prevent stress-induced senescence. This barrier is overcome by spontaneous methylation of the p16 (INK4a) promoter, allowing the proliferation of cells with telomere dysfunction and ensuing chromosome instability.