Tumor organoids to study gastroesophageal cancer: a primer

Current trends and future prospects of drug repositioning in gastrointestinal oncology

Gastrointestinal (GI) cancers comprise a significant number of cancer cases worldwide and contribute to a high percentage of cancer-related deaths. To improve survival rates of GI cancer patients, it is important to find and implement more effective therapeutic strategies with better prognoses and fewer side effects. The development of new drugs can be a lengthy and expensive process, often involving clinical trials that may fail in the early stages. One strategy to address these challenges is drug repurposing (DR). Drug repurposing is a developmental strategy that involves using existing drugs approved for other diseases and leveraging their safety and pharmacological data to explore their potential use in treating different diseases. In this paper, we outline the existing therapeutic strategies and challenges associated with GI cancers and explore DR as a promising alternative approach. We have presented an extensive review of different DR methodologies, research efforts and examples of repurposed drugs within various GI cancer types, such as colorectal, pancreatic and liver cancers. Our aim is to provide a comprehensive overview of employing the DR approach in GI cancers to inform future research endeavors and clinical trials in this field.

Molecular pathogenesis, targeted therapies, and future perspectives for gastric cancer

Gastric cancer is a major source of global cancer mortality with limited treatment options and poor patient survival. As our molecular understanding of gastric cancer improves, we are now beginning to recognize that these cancers are a heterogeneous group of diseases with incredibly unique pathogeneses and active oncogenic pathways. It is this molecular diversity and oftentimes lack of common oncogenic driver mutations that bestow the poor treatment responses that oncologists often face when treating gastric cancer. In this review, we will examine the treatments for gastric cancer including up-to-date molecularly targeted therapies and immunotherapies. We will then review the molecular subtypes of gastric cancer to highlight the diversity seen in this disease. We will then shift our discussion to basic science and gastric cancer mouse models as tools to study gastric cancer molecular heterogeneity. Furthermore, we will elaborate on a molecular process termed paligenosis and the cyclical hit model as key events during gastric cancer initiation that impart nondividing mature differentiated cells the ability to re-enter the cell cycle and accumulate disparate genomic mutations during years of chronic inflammation and injury. As our basic science understanding of gastric cancer advances, so too must our translational and clinical efforts. We will end with a discussion regarding single-cell molecular analyses and cancer organoid technologies as future translational avenues to advance our understanding of gastric cancer heterogeneity and to design precision-based gastric cancer treatments. Elucidation of interpatient and intratumor heterogeneity is the only way to advance future cancer prevention, diagnoses and treatment.

Application of Organoids in Carcinogenesis Modeling and Tumor Vaccination

Organoids well recapitulate organ-specific functions from their tissue of origin and remain fundamental aspects of organogenesis. Organoids are widely applied in biomedical research, drug discovery, and regenerative medicine. There are various cultivated organoid systems induced by adult stem cells and pluripotent stem cells, or directly derived from primary tissues. Researchers have drawn inspiration by combination of organoid technology and tissue engineering to produce organoids with more physiological relevance and suitable for translational medicine. This review describes the value of applying organoids for tumorigenesis modeling and tumor vaccination. We summarize the application of organoids in tumor precision medicine. Extant challenges that need to be conquered to make this technology be more feasible and precise are discussed.

Gastric Organoids: Progress and Remaining Challenges

The stomach is a complex and physiologically necessary organ, yet large differences in physiology between mouse and human stomachs have impeded translation of physiological discoveries and drug screens performed using murine gastric tissues. Gastric cancer (GC) is a global health threat, with a high mortality rate and limited treatment options. The heterogeneous nature of GC makes it poorly suited for current "one size fits all" standard treatments. In this review, we discuss the rapidly evolving field of gastric organoids, with a focus on studies expanding cultures from primary human tissues and describing the benefits of mouse organoid models. We introduce the differing methods for culturing healthy gastric tissue from adult tissues or pluripotent stem cells, discuss the promise these systems have for preclinical drug screens, and highlight applications of organoids for precision medicine. Finally, we discuss the limitations of these models and look to the future to present potential ways gastric organoids will advance treatment options for patients with GC.

Understanding the cellular origin and progression of esophageal cancer using esophageal organoids

Three-dimensional (3D) organoids are a novel tool to model epithelial cell biology and human diseases of the esophagus. 3D organoid culture systems have been utilized to investigate the pathobiology of esophageal cancer, including both squamous cell carcinoma and adenocarcinoma. Additional organoid-based approaches for study of esophageal development and benign esophageal diseases have provided key insights into esophageal keratinocyte differentiation and mucosal regeneration. These investigations have implications for the identification of esophageal cancer stem cells, as well as the potential to halt malignant progression through induction of differentiation pathways. Patient-derived organoids (PDOs) from human tissue samples allow for unique and faithful in vitro modeling of esophageal cancers, and provide an exciting platform for investigation into personalized medicine and targeted treatment approaches, as well as new models for understanding therapy resistance and recurrent disease. Future directions include high-throughput genomic screening using PDOs, and study of tumor-microenvironmental interactions through co-culture with immune and stromal cells and novel extracellular matrix complexes.

Mechanism of tumour microenvironment in the progression and development of oral cancer

Oral cancer has been a major problem all across the globe, majorly in the developing countries. With a growing emphasis in the field of cancer research, the contribution of the tumour microenvironment has been gaining a lot of importance in identifying the role of components other than the tumour cells that cause the development of cancer, thus changing the outlook. The review will shed light on the studies that describe the role of microenvironment, its components as well as summarize the studies related to their mechanism in the progression of oral cancer. The literature for the review was derived mainly from Google Scholar and PubMed, in particular concentrating on the most recent papers published in 2019 and 2020, by using the keywords "Cancer, Oral Cancer, Metastasis, OSCC, Tumour microenvironment, CAFs, ECM, Cytokines, Hypoxia, Therapeutics targeting the microenvironment". The study provides insight into the world of micro-environmental regulation of oral cancer, the mechanism by which they interact and how to exploit it as a potential therapeutic haven for treating the disease. The components Cancer-Associated Fibroblasts (CAFs), Tumour-associated Macrophages (TAMs), Tumour-associated neutrophils (TANs), Hypoxic environment, myeloid-derived stem cells (MDSCs) and T regulatory (Tregs) cells and underlying mechanisms that control them will be the targets of study to understand the microenvironment.