Exploiting Vitamin D Receptor and Its Ligands to Target Squamous Cell Carcinomas of the Head and Neck

• Published in: International journal of molecular sciences Vol. 24; no. 5; p. 4675
• Main Authors: Koll, Laura, Gül, Désirée, Elnouaem, Manal I, Raslan, Hanaa, Ramadan, Omneya R, Knauer, Shirley K, Strieth, Sebastian, Hagemann, Jan, Stauber, Roland H, Khamis, Aya
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 28.02.2023; MDPI
• Subjects: 1-Phosphatidylinositol 3-kinase; 3D tumor spheroids; AKT protein; Alfacalcidol; Analysis; Breast cancer; Calcifediol; Calciferol; calcitriol; Cancer therapies; Carcinoma, Squamous Cell - drug therapy; Cisplatin; Cisplatin - therapeutic use; Colon; Computer architecture; Correlation; Disease; Drug therapy, Combination; Female; Functional foods & nutraceuticals; gender-specific effects; Genomes; Head & neck cancer; Head and Neck Neoplasms - drug therapy; Humans; Ki-67 Antigen - metabolism; Ligands; Male; Medical prognosis; Molecular Targeted Therapy; Nuclear receptors; Phosphatidylinositol 3-Kinases - metabolism; Physiology; Receptors, Calcitriol - metabolism; Retinoic acid; Retinoid X receptors; RNA sequencing; Serum levels; Spheroids; Squamous cell carcinoma; Success; TOR protein; Tumor cells; Tumors; Vitamin D; Vitamin D - therapeutic use; Vitamin D receptors; Vitamins - therapeutic use; Netherlands; Germany; nuclear receptors; calcitriol; gender-specific effects; 3D tumor spheroids
• DOI: 10.3390/ijms24054675
• ISSN: 1422-0067; 1661-6596

Vitamin D (VitD) and its receptor (VDR) have been intensively investigated in many cancers. As knowledge for head and neck cancer (HNC) is limited, we investigated the (pre)clinical and therapeutic relevance of the VDR/VitD-axis. We found that VDR was differentially expressed in HNC tumors, correlating to the patients' clinical parameters. Poorly differentiated tumors showed high VDR and Ki67 expression, whereas the VDR and Ki67 levels decreased from moderate to well-differentiated tumors. The VitD serum levels were lowest in patients with poorly differentiated cancers (4.1 ± 0.5 ng/mL), increasing from moderate (7.3 ± 4.3 ng/mL) to well-differentiated (13.2 ± 3.4 ng/mL) tumors. Notably, females showed higher VitD insufficiency compared to males, correlating with poor differentiation of the tumor. To mechanistically uncover VDR/VitD's pathophysiological relevance, we demonstrated that VitD induced VDR nuclear-translocation (VitD < 100 nM) in HNC cells. RNA sequencing and heat map analysis showed that various nuclear receptors were differentially expressed in cisplatin-resistant versus sensitive HNC cells including VDR and the VDR interaction partner retinoic acid receptor (RXR). However, RXR expression was not significantly correlated with the clinical parameters, and cotreatment with its ligand, retinoic acid, did not enhance the killing by cisplatin. Moreover, the Chou-Talalay algorithm uncovered that VitD/cisplatin combinations synergistically killed tumor cells (VitD < 100 nM) and also inhibited the PI3K/Akt/mTOR pathway. Importantly, these findings were confirmed in 3D-tumor-spheroid models mimicking the patients' tumor microarchitecture. Here, VitD already affected the 3D-tumor-spheroid formation, which was not seen in the 2D-cultures. We conclude that novel VDR/VitD-targeted drug combinations and nuclear receptors should also be intensely explored for HNC. Gender-specific VDR/VitD-effects may be correlated to socioeconomic differences and need to be considered during VitD (supplementation)-therapies.