Background: 5-year survival rate of oral tongue squamous cell carcinoma (OTSCC) has been low (less than 60%) despite developing treatment modalities. A previous research revealed that different populations of inflammatory cells infiltration in OTSCC were associated with different clinical outcomes. On the other hand, extracellular vesicles (EVs) secreted by OTSCC cells suggested crosstalk between OTSCC cells and tumor infiltrating inflammatory cells. Study aims: This study aims to investigate the interaction between OTSCC cells and inflammatory cells and answer 3 questions: (1) Can human peripheral blood mononuclear cells (MNCs) affect activities of OTSCC cells such as proliferation, migration and invasion? (2) Can EVs of OTSCC cells affect polarization of macrophages? (3) Can EVs of OTSCC cells affect cytotoxic activity of CD8+ T cells and NK cells? Materials and methods: Two OTSCC cell lines (HSC-3 and SCC-25) were used. OTSCC cells and human peripheral blood MNCs were co-cultured using a 3D organotypic myoma model. Proliferation and invasion into myoma tissue of OTSCC cells were detected by Immunohistochemical staining of pan-cytokeratin and Ki67. Invasion area and depth of OTSCC cells were measured using ImageJ software. Migration of OTSCC cells in the presence of MNCs was monitored using a scratch wound healing assay with IncuCyte™ system. OTSCC EVs were isolated with ultracentrifugation and characterized with NTA and Immuno-EM. Human primary monocytes, CD8+ T cells and NK cells were isolated using MACS, and their purity was checked using FACS. Expression of macrophage phenotypic markers was checked with qPCR. Cytotoxic activity was evaluated using an IncyCyte™ cell killing assay. Results: Activated human peripheral blood MNCs significantly reduced proliferation of both OTSCC cell lines, and invasion area of only HSC-3. None of the inflammatory cells in the experiment had any effect on invasion depth and migration of OTSCC cells. On the other hand, OTSCC cell-derived EVs didn't influence macrophage polarization, but had heterogeneous modulating effects on cytotoxic activity of CD8+ T cells and NK cells. Conclusion: We detected effects of OTSCC cells and inflammatory cells on each other by secreted molecule mediators or EVs, but the results were not uniform and varied in different OTSCC cell lines or inflammatory cell populations and sources. The outcome of the study emphasizes the importance of a personalized design of cancer treatment, which takes other components in tumor microenvironment such as inflammatory cells and EVs into consideration.

Oral tongue squamous cell carcinoma (OTSCC) is one of the most common types of oral cancer. OTSCC usually occurs in males between the ages of 60-70, but recently there has been an increase in OTSCC patients under the age of 40. Commonly known risk factors for tongue cancer are heavy smoking and excessive alcohol consumption. The aim of our study was to find a correlation between gender and prevalence of diagnosis in OTSCC patients, and to observe if OTSCC has become more common in younger patients during recent years. In this study, we studied oral tongue squamous cell carcinoma cases found in the data pool of the pathological department of the University of Helsinki central hospital Q-Pati during the years 1975-2018. We recorded only the gender, date of birth and age at the time of diagnosis. For the statistical analysis, we divided our patients in age-groups of ≤40 years, 40-59 years and ≥60 years. The data was then analyzed using R-studio. From the data, we calculated the incidence rate ratio (IRR) and p-value using the Poisson analysis method. The results show that the rate of diagnosed OTSCC patients has generally increased in all age groups. For female patients the biggest increase was observed in patients ≥60 years old and in male patients 40-59 years old. In both genders we could observe a statistically significant increase in younger patients.