Cancer Biology

The ubiquitous and cancer-associated Epstein-Barr virus (EBV) is associated with nearly all cases of nasopharyngeal carcinoma (NPC). Nasopharyngeal tissue is comprised of both pseudostratified and stratified epithelium, which are modeled in three-dimensional (3-D) cell culture. The cellular origin of EBV-associated NPC is as yet unknown, but both latent and lytic infections are likely important for preneoplastic mechanisms and replenishing the compartmentalized viral reservoir. Conventional 2-D cultures of nasopharyngeal epithelial cells (as primary cells or immortalized cell lines) are difficult to infect with EBV and cannot mimic the tissue-specific biology of the airway epithelium, which can only be captured in 3-D models. We have shown that EBV can infect the pseudostratified epithelium in air-liquid interface (ALI) culture using primary conditionally reprogrammed cells (CRCs) derived from the nasopharynx. In this protocol, we provide a step-by-step guide for the (i) conditional reprogramming of primary nasopharyngeal cells, (ii) differentiation of CRCs into pseudostratified epithelium in ALI culture (known as pseudo-ALI), and (iii) EBV infection of pseudo-ALI cultures. Additionally, we show that nasopharyngeal CRCs can be grown as organotypic rafts and subjected to EBV infection. These nasopharyngeal-derived 3-D cell cultures can be used to study EBV latent and lytic infection in relation to cell type and donor variation, by immunostaining and single-cell RNA-sequencing methods (Ziegler et al., 2021). These methods are useful for studies of EBV molecular pathogenesis, and can overcome many of the limitations associated with conventional 2-D cell cultures.

Graphic abstract:

Workflow of nasopharyngeal-derived conditionally reprogrammed cells grown into pseudostratified-ALI and organotypic rafts in 3-D cell culture. Created with Biorender.com.

With the advent of CRISPR-Cas and the ability to easily modify the genome of diverse organisms, rat models are being increasingly developed to interrogate the genetic events underlying mammary development and tumorigenesis. Protocols for the isolation and characterization of mammary epithelial cell subpopulations have been thoroughly developed for mouse and human tissues, yet there is an increasing need for rat-specific protocols. To date, there are no standard protocols for isolating rat mammary epithelial subpopulations. Analyzing changes in the rat mammary hierarchy will help us elucidate the molecular events in breast cancer, the cells of origin for breast cancer subtypes, and the impact of the tumor microenvironment. Here we describe several methods developed for 1) rat mammary epithelial cell isolation; 2) rat mammary fibroblast isolation; 3) culturing rat mammary epithelial cells; and characterization of rat mammary cells by 4) flow cytometric analysis; and 5) immunofluorescence. Cells derived from this protocol can be used for many purposes, including RNAseq, drug studies, functional assays, gene/protein expression analyses, and image analysis.

Chromatin consists of compacted DNA in complex with proteins and contributes to the organization of DNA and its stability. Furthermore, chromatin plays key roles in regulating cellular processes such as DNA replication, transcription, DNA repair, and mitosis. Chromatin assumes more compact (inaccessible) or decondensed (accessible) conformations depending on the function that is being supported in the genome, either locally or globally. The activity of nucleases has been used previously to assess the accessibility of specific genomic regions in vitro, such as origins of replication at varying points in the cell cycle. Here, we provide an assay to determine the accessibility of specific human genomic regions (example used herein: Lamin B2 origin of DNA replication) by measuring the effect of DNase I nuclease on qPCR signal from the studied site. This assay provides a powerful method to interrogate the molecular mechanisms that regulate chromatin accessibility, and how these processes affect various cellular functions involving the human genome that require manipulation of chromatin conformation.

Heterogeneous prostatic carcinoma-associated fibroblasts (CAF) contribute to tumor progression. This was established using transgenic mouse models. Paracrine interactions between fibroblasts and epithelial cells were further interrogated using isolated 2D cell culture systems, but 3D culture systems currently being developed can better mimic reciprocal interactions potentially found in the native tissue. To understand paracrine and juxtacrine signaling among fibroblasts and epithelia, 3D co-cultures with species differences allows for further subsequent analysis of the cultures. The use of mouse and human cells, for example, in one system allows for species-specific FACS or quantitative PCR analysis. This protocol describes the use of a 3D Co-culture System of Mouse Prostatic Wild-type Fibroblasts with Human Prostate Cancer Epithelial Cells.

To assess oncogenic potential, classical transformation assays are based on cell line models. However, cell line based models do not reflect the complexity of human tissues. We thus developed an inducible expression system for gene expression in ex vivo human tissues, which maintain native tissue architecture, such as epithelia and stroma. To validate the system, we transduced and expressed known tumor suppressors (p53, p33ING1b), oncoproteins (RasV12, p47ING3), or controls (empty vector, YFP) in ex vivo prostate tissues, then assessed proliferation by immunohistochemistry of markers (H3S10^phos). Herein, we describe how to generate lentiviral vectors and particules, successfully transduce human prostate tissues, induce exogenous gene expression, and assess cellular proliferation.