Immortalized cells as experimental models to study cancer

The applications and techniques of organoids in head and neck cancer therapy

Head and neck cancer (HNC) is one of the most common cancers on the planet, with approximately 600,000 new cases diagnosed and 300,000 deaths every year. Research into the biological basis of HNC has advanced slowly over the past decades, which has made it difficult to develop new, more effective treatments. The patient-derived organoids (PDOs) are made from patient tumor cells, resembling the features of their tumors, which are high-fidelity models for studying cancer biology and designing new precision medicine therapies. In recent years, considerable effort has been focused on improving "organoids" technologies and identifying tumor-specific medicine using head and neck samples and a variety of organoids. A review of improved techniques and conclusions reported in publications describing the application of these techniques to HNC organoids is presented here. Additionally, we discuss the potential application of organoids in head and neck cancer research as well as the limitations associated with these models. As a result of the integration of organoid models into future precision medicine research and therapeutic profiling programs, the use of organoids will be extremely significant in the future.

Head and neck cancer patient-derived tumouroid cultures: opportunities and challenges

Head and neck cancers (HNC) are the seventh most prevalent cancer type globally. Despite their common categorisation, HNCs are a heterogeneous group of malignancies arising in various anatomical sites within the head and neck region. These cancers exhibit different clinical and biological manifestations, and this heterogeneity also contributes to the high rates of treatment failure and mortality. To evaluate patients who will respond to a particular treatment, there is a need to develop in vitro model systems that replicate in vivo tumour status. Among the methods developed, patient-derived cancer organoids, also known as tumouroids, recapitulate in vivo tumour characteristics including tumour architecture. Tumouroids have been used for general disease modelling and genetic instability studies in pan-cancer research. However, a limited number of studies have thus far been conducted using tumouroid-based drug screening. Studies have concluded that tumouroids can play an essential role in bringing precision medicine for highly heterogenous cancer types such as HNC.

New insights from Whole Genome Sequencing: BCLAF1 deletion as a structural variant that predisposes cells towards cellular transformation

Cancer arises from a multi‑step cellular transformation process where some mutations may be inherited, while others are acquired during the process of malignant transformation. Aberrations in the BCL2 associated transcription factor 1 (BCLAF1) gene have previously been identified in patients with cancer and the aim of the present study was to identify structural variants (SVs) and the effects of BCLAF1 gene silencing on cell transformation. Whole‑genome sequencing was performed on DNA isolated from tumour biopsies with a histologically confirmed diagnosis of oesophageal squamous cell carcinoma (OSCC). Paired‑end sequencing was performed on the Illumina HiSeq2000, with 300 bp reads. Reads were aligned to the Homo sapiens reference genome (NCBI37) using ELAND and CASAVA software. SVs reported from the alignment were collated with gene loci, using the variant effect predictor of Ensembl. The affected genes were subsequently cross‑checked against the Genetic Association Database for disease and cancer associations. BCLAF1 deletion was identified as a noteworthy SV that could be associated with OSCC. Transient small interfering RNA‑mediated knockdown of BCLAF1 resulted in the altered expression of several downstream genes, including downregulation of the proapoptotic genes Caspase‑3 and BAX and the DNA damage repair genes exonuclease 1, ATR‑interacting protein and transcription regulator protein BACH1. BCLAF1 deficiency also attenuated P53 gene expression. Inhibition of BCLAF1 expression also resulted in increased colony formation. These results provide evidence that the abrogation of BCLAF1 expression results in the dysregulation of several cancer signalling pathways and abnormal cell proliferation.

Screening of Health-Associated Oral Bacteria for Anticancer Properties in vitro

While extensive literature exists about the role of oral bacterial pathogens like Porphyromonas gingivalis and Fusobacterium nucleatum in oral squamous cell carcinoma (OSCC), the role of health-associated species has been largely unexplored. In this study, we assessed the effect of Streptococcus mitis, Rothia mucilaginosa, Neisseria flavescens, Haemophilus parainfluenzae, Lautropia mirabilis, and Veillonella parvula on proliferation and expression of marker genes (IL-6, TNF-α, MMP3, CD36, CCD1, and NANOG) in OSCC cell lines CAL27, SCC25, and SCC4. Porphyromonas gingivalis was included as a pathogenic control. Both bacterial lysates (3 concentrations) and live cells (3 MOIs) were tested. S. mitis, H. parainfluenzae, and N. flavescens resulted in substantial, dose-dependent reduction of proliferation, which was found to be mediated by H₂O₂ for the former and intracellular infection in the latter two species. However, only H. parainfluenzae showed differential antiproliferative effect against the cancer cell lines vs. the normal control (TIGKs). In the gene expression assays, the health-associated species mostly downregulated CD36, a gene that plays an important role in tumor growth and metastasis, while P. gingivalis upregulated it. IL6 and TNF expression, on the other hand, was upregulated by almost all species, particularly the Gram-negatives including P. gingivalis. The effect on other genes was less evident and varied significantly by cell line. This exploratory study is the first insight into how health-associated bacteria may interact with OSCC. Further studies to explore whether the observed effects may have implications for the prevention or treatment of oral cancer are warranted.

Patient-Derived Xenografts as an Innovative Surrogate Tumor Model for the Investigation of Health Disparities in Triple Negative Breast Cancer

Despite a decline in overall incidence rates for cancer in the past decade, due in part to impressive advancements in both diagnosis and treatment, breast cancer (BC) remains the leading cause of cancer-related deaths in women. BC alone accounts for ∼30% of all new cancer diagnoses in women worldwide. Triple-negative BC (TNBC), defined as having no expression of the estrogen or progesterone receptors and no amplification of the HER2 receptor, is a subtype of BC that does not benefit from the use of estrogen receptor-targeting or HER2-targeting therapies. Differences in socioeconomic factors and cell intrinsic and extrinsic characteristics have been demonstrated in Black and White TNBC patient tumors. The emergence of patient-derived xenograft (PDX) models as a surrogate, translational, and functional representation of the patient with TNBC has led to the advances in drug discovery and testing of novel targeted approaches and combination therapies. However, current established TNBC PDX models fail to represent the diverse patient population and, most importantly, the specific ethnic patient populations that have higher rates of incidence and mortality. The primary aim of this review is to emphasize the importance of using clinically relevant translatable tumor models that reflect TNBC human tumor biology and heterogeneity in high-risk patient populations. The focus is to highlight the complexity of BC as it specifically relates to the management of TNBC in Black women. We discuss the importance of utilizing PDX models to study the extracellular matrix (ECM), and the distinct differences in ECM composition and biophysical properties in Black and White women. Finally, we demonstrate the crucial importance of PDX models toward novel drug discovery in this patient population.

Induced pluripotent stem cells: A new strategy to model human cancer

Induced pluripotent stem cells are derived from adult somatic cells by ectopic expression of stem cell factors OCT4, SOX2, MYC and KLF4. These cells have characteristic features similar to embryonic stem cells. Although there exists in vitro and in vivo models of cancer, recapitulating the earliest events in the pathogenesis remain challenging. More recently, induced pluripotent stem cells have been generated to model human disease and cancer. There are advantages in the cancer models derived from these cells as compared to existing conventional approaches. Induced pluripotent stem cells have been generated from cancer cell lines, primary tumours and from those with an inherited predisposition to develop cancer. In addition, these cells provide a valuable tool in understanding the pathogenesis of familial cancer in its earliest stages, and to identify additional genetic alterations that are required to develop cancer. Furthermore, these cells can serve as a resource in drug screening and developing new therapies.

Gene expression changes in human lung cells exposed to arsenic, chromium, nickel or vanadium indicate the first steps in cancer

The complex process of carcinogenesis begins with transformation of a single cell to favor aberrant traits such as loss of contact inhibition and unregulated proliferation - features found in every cancer. Despite cancer's widespread prevalence, the early events that initiate cancer remain elusive, and without knowledge of these events cancer prevention is difficult. Here we show that exposure to As, Cr, Ni, or vanadium (V) promotes changes in gene expression that occur in conjunction with aberrant growth. We exposed immortalized human bronchial epithelial cells to one of four metals/metalloid for four to eight weeks and selected transformed clonal populations based upon anchorage independent growth of single cells in soft agar. We detected a metal-specific footprint of cancer-related gene expression that was consistent across multiple transformed clones. These gene expression changes persisted in the absence of the progenitor metal for numerous cell divisions. Our results show that even a brief exposure to a carcinogenic metal may cause many changes in gene expression in the exposed cells, and that from these many changes, the specific change(s) that each metal causes that initiate cancer likely arise.

Cell transformation assays for prediction of carcinogenic potential: state of the science and future research needs

Cell transformation assays (CTAs) have long been proposed as in vitro methods for the identification of potential chemical carcinogens. Despite showing good correlation with rodent bioassay data, concerns over the subjective nature of using morphological criteria for identifying transformed cells and a lack of understanding of the mechanistic basis of the assays has limited their acceptance for regulatory purposes. However, recent drivers to find alternative carcinogenicity assessment methodologies, such as the Seventh Amendment to the EU Cosmetics Directive, have fuelled renewed interest in CTAs. Research is currently ongoing to improve the objectivity of the assays, reveal the underlying molecular changes leading to transformation and explore the use of novel cell types. The UK NC3Rs held an international workshop in November 2010 to review the current state of the art in this field and provide directions for future research. This paper outlines the key points highlighted at this meeting.

Telomerase immortalization of principal cells from mouse collecting duct

Recently, the use of overexpression of telomerase reverse transcriptase (TERT) has led to the generation of immortalized human cell lines. However, this cell immortalization approach has not been reported in well-differentiated mouse cells, such as renal epithelial cells. We sought to establish and then characterize a mouse collecting duct cell line, using ectopic expression of mTERT. Isolated primary cortical collecting duct (CCD) cell lines were transduced with mouse (m)TERT, using a lentiviral vector. mTERT-negative cells did not survive blasticidin selection, whereas mTERT-immortalized cells proliferated in selection media for over 40 subpassages. mTERT messenger RNA and telomerase activity was elevated in these cells, compared with an SV40-immortalized cell line. Flow cytometry with Dolichos biflorus agglutinin was used to select the CCD principal cells, and we designated this cell line mTERT-CCD. Cells were well differentiated and exhibited morphological characteristics typically found in renal epithelial cells, such as tight junction formation, microvilli, and primary cilia. Further characterization using standard immunofluorescence revealed abundant expression of aquaporin-2 and the vasopressin type 2 receptor. mTERT-CCD cells exhibited cAMP-stimulated/benzamil-inhibited whole cell currents. Whole cell patch-clamp currents were also enhanced after a 6-day treatment with aldosterone. In conclusion, we have successfully used mTERT to immortalize mouse collecting duct cells that retain the basic in vivo phenotypic characteristics of collecting duct cells. This technique should be valuable in generating cell lines from genetically engineered mouse models.

Check your cultures! A list of cross-contaminated or misidentified cell lines

Continuous cell lines consist of cultured cells derived from a specific donor and tissue of origin that have acquired the ability to proliferate indefinitely. These cell lines are well-recognized models for the study of health and disease, particularly for cancer. However, there are cautions to be aware of when using continuous cell lines, including the possibility of contamination, in which a foreign cell line or microorganism is introduced without the handler's knowledge. Cross-contamination, in which the contaminant is another cell line, was first recognized in the 1950s but, disturbingly, remains a serious issue today. Many cell lines become cross-contaminated early, so that subsequent experimental work has been performed only on the contaminant, masquerading under a different name. What can be done in response-how can a researcher know if their own cell lines are cross-contaminated? Two practical responses are suggested here. First, it is important to check the literature, looking for previous work on cross-contamination. Some reports may be difficult to find and to make these more accessible, we have compiled a list of known cross-contaminated cell lines. The list currently contains 360 cell lines, drawn from 68 references. Most contaminants arise within the same species, with HeLa still the most frequently encountered (29%, 106/360) among human cell lines, but interspecies contaminants account for a small but substantial minority of cases (9%, 33/360). Second, even if there are no previous publications on cross-contamination for that cell line, it is essential to check the sample itself by performing authentication testing.