Identifying potential immuno-oncology targets in salivary gland mucoepidermoid carcinoma based on inflammatory status and treatment response.

Abstract

Mucoepidermoid carcinoma is a rare salivary gland malignant tumour. This study aimed to investigate inflammatory and immune signatures of mucoepidermoid carcinoma by identifying potential proteo-transcriptomic biomarkers towards the development of precision immuno-oncology treatment strategies. A total of 30 biopsies obtained from patients diagnosed with mucoepidermoid carcinoma between 2013 and 2022 were analysed after H&E staining for scoring of histological inflammatory stroma subtypes and inflammatory hotspots with QuPath. Multiplex immunofluorescence staining and NanoString nCounter PanCancer IO 360™ panel were used to assess stroma and tumour inflammation signatures in high grade mucoepidermoid carcinoma cases in the tumour microenvironment via proteomics and transcriptomics, respectively. Inflammatory cells within the histological inflammatory stroma inflammatory (HIS-INF/hot) tumour neighbourhoods were greater compared to the histological inflammatory stroma-immune desert (HIS-ID/cold) (p = 0.001). A similar trend was observed between treatment non-responders and responders in stroma neighbourhoods (p = 0.0625) and in stroma-to-interface inflammatory hotspots (p = 0.0081), indicating an augmented inflammatory response in hot tumours and non-responders. Furthermore, there were striking differences in the expression of pan-immune leukocyte marker CD45 between responders and non responders particularly in the tumour neighbourhoods (p = 0.0341), but such were not robust for PD-1 and macrophage fractions. Additionally, transcriptomic analysis revealed key differences in leukocyte activation profiles between responders and non-responders. This preliminary report unveils the importance of assessing immune leukocyte cellular fractions and pathways for future prognostic biomarker discoveries in mucoepidermoid carcinoma as per the involvement of CD45-driven inflammatory and immune mediators in high grade mucoepidermoid carcinoma in non-responders to treatment. These findings will potentially contribute to the development of novel personalised immunotherapies.