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

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.

Oral and Extraoral Intermediate Tumors: Are MMP-9 and Ki-67 Biomarkers Correlated to Their High Recurrence Rates?

Intermediate tumors of the head and neck fall in the borderline category. They are clinically aggressive tumors with no malignant phenotyping. They are locally infiltrative and have high recurrence rate with less chances to metastasize. The standard care is surgical excision with wide margins. However, surgeons are challenged with the anatomic complexity of the head and neck, increasing the susceptibly of satellite cells being left behind. Ki-67 and MMP-9 are proliferative index and extracellular matrix degradation biomarkers, respectively. They are directly correlated to malignant tumors, whereas less associated with the benign ones. Our main objective was to correlate between Ki-67 and MMP-9 expressions and the recurrence rates in these borderline tumors. We performed a retrospective immunohistochemical study comparing the immunoexpression of Ki-67 and MMP-9. Tumors of interest were aggressive fibromatosis (AF, n=70), epithelioid hemangioendothelioma (EHE, n=25), hemangiopericytoma (HP, n=25), benign fibrous histiocytoma (BFH, n=80) and juvenile ossifying fibroma (JOF, n= 40). Our results revealed that AF followed by HP showed significant high levels of MMP-9 expression, with an average positive area percentage of 40% and 37.4% respectively, compared with other tumors (P<0.05). Ki-67 immunoreaction was significantly the lowest in AF (2.3%, P<0.05) and the highest in JOF (24.7%). To conclude, MMP-9 can be used as a possible target in these tumors as an adjuvant therapy to minimize recurrence rates.