The Role of Mesenchymal Stem/Stromal Cells in Head and Neck Cancer – Regulatory Mechanisms of Tumorigenic and Immune Activity, Chemotherapy Resistance, and Therapeutic Benefits of the Use of Stromal Cell-Based Pharmacological Strategies
Authors: Starska-Kowarska Katarzyna 
Published: June 2024

The most common type of head and neck cancer (HNC) is head and neck squamous cell carcinoma (HNSCC). It describes a heterogenous neoplastic disease that arises from the mucosal epithelium of the of the upper respiratory system and the gastrointestinal tract. It is characterized by high morbidity and mortality, being is the eighth most common cancer worldwide, with 931,931 newly diagnosed cases and 467,125 deaths according to the latest Global Cancer Statistics (GLOBOCAN) data. Despite the use of modern low-invasive surgical techniques and application of promising new chemoradiotherapies or combination treatment, the frequency of recurrences and the five-year survival of these patients remains unsatisfactory. The microenvironment of head and neck cancer comprises various cells that regulate neoplastic expansion. It is believed that the mesenchymal stromal cells (MSCs) present in the tumour milieu play a key role in the modulation of tumour initiation, development and progression, in the regulation of cancer treatment response, survival rates, patient outcomes and long-term prognosis; they also influence the resistance to cisplatin-based chemotherapy, the gold standard for advanced HNSCC. MSCs, are multipotent, heterogeneous, mobile cells, which meet specific stemness criteria defined by the International Society for Cellular Therapy (ISCT). Although no MSC-specific markers exist, they can be recognized based on several others, such as CD73, CD90 and CD105, while lacking the presence of CD45, CD34, CD14 or CD11b, CD79α, or CD19 and HLA-DR antigens; they share phenotypic similarity with stromal cells and their capacity to differentiate into other cell types. In the tumour niche, MSC populations are characterized by cell quiescence, self-renewal capacity, low reactive oxygen species production and the acquisition of epithelial-to-mesenchymal transition properties, they may play a key role in the process of acquiring drug resistance, and thus treatment failure. MSCs must also demonstrate plastic adherence in vitro and be able to differentiate into specific mesodermal cell types after stimulation i.e., adipocytes, chondrocytes, and osteoblasts when cultured under well-defined conditions. The present narrative review examines the links between mesenchymal stromal/stem cells and HNC, as well as the different mechanisms involved in the development of resistance to current chemo- and radiotherapies in HNSCC. It provides an overview of the current literature, including key opinion-forming systematic reviews, as well as cross-sectional, longitudinal, prospective and interventional studies based on cell culture models in vitro, animal or in vivo models of HNSCC; it also examines the possibilities of pharmacological targeting of stemness-related chemoresistance in HNSCC. It describes promising new strategies to optimize chemoradiotherapy with the potential to personalize patient treatment approaches, and highlights future therapeutic perspectives in HNC. The data concerning tumour-associated MSCs is arranged according to increasing clinical credibility.