Vitamin D3 (Calcitriol) Monotherapy Decreases Tumor Growth, Increases Survival, and Correlates with Low Neutrophil-to-Lymphocyte Ratio in a Murine HPV-16-Related Cancer Model.

Vitamin D3 or calcitriol (VitD3) has been shown to have anticancer and anti-inflammatory activity in in vitro models and clinical studies. However, its effect on HPV-16-related cancer has been sparsely explored. In this study, we aimed to determine whether monotherapy or combination therapy with cisplatin (CP) reduces tumor growth and affects survival and systemic inflammation. Treatments were administered to C57BL/6 mice with HPV-16-related tumors (TC-1 cells) as follows: (1) placebo (100 µL vehicle, olive oil, orally administered daily); (2) VitD3 (3.75 µg/kg calcitriol orally administered daily); (3) CP (5 mg/kg intraperitoneally, every 7 days); and (4) VitD3+CP. Tumor growth was monitored for 25 days, survival for 60 days, and the neutrophil-to-lymphocyte ratio (NLR) was evaluated on days 1 (baseline), 7, and 14. VitD3+CP showed greater success in reducing tumor volume compared to CP monotherapy ( p = 0.041), while no differences were observed between CP and VitD3 monotherapy ( p = 0.671). Furthermore, VitD3+CP prolonged survival compared to CP ( p = 0.036) and VitD3 ( p = 0.007). Additionally, at day 14 the VitD3 and VitD3+CP groups showed significantly lower NLR values than the CP group ( p < 0.05, for both comparisons). Vitamin D3 could be a promising adjuvant in the treatment of cervical cancer or solid tumors and deserves further investigation.