Investigating the Mechanisms of Anti-tumoral Effect of Combination Therapy of Calcitriol and Sodium Pentaborate Pentahydrate on HepG2 Hepatocellular Carcinoma Cells.

Hepatocellular carcinoma (HCC) is one of the most common primary liver cancers worldwide and is often associated with poor prognosis due to drug resistance. Combination therapies demonstrate superior efficacy at lower drug dosages on cancer cells compared to single treatments, resulting in less drug resistance in the cells. This study investigates the synergistic anti-tumoral effects of calcitriol, the biologically active form of vitamin D, and sodium pentaborate pentahydrate (NaB) on HepG2 cells. We examined the cell viability of NaB, calcitriol, or the combination of NaB and calcitriol on HepG2 cells and healthy human hepatic stellate cells (HHSC) using MTS. Our findings showed that combination therapy with 3.3 mM NaB and 1 µM calcitriol has a synergistic effect and a more cytotoxic effect on HepG2 cells. This combination significantly increased apoptosis and ROS levels compared to treatment alone with NaB or calcitriol. Gene expression and proteomics analysis revealed inhibition of DNA replication and the cell cycle process, further confirming the potent anti-proliferative effects of the combination therapy. When HepG2 cells were treated with a combination of 3.3 mM NaB and 1 µM calcitriol, mRNA levels of apoptosis-related genes AKT1 and MDM2 were downregulated, while p53 was upregulated. Additionally, cell cycle-related genes CDKN1A, GADD45A, and p27 were upregulated, whereas MCM2, MCM5, and MCM7 were downregulated. Furthermore, genes associated with the vitamin D receptor (VDR), including VDR and CYP24A1, were upregulated, while CYP27B1 was downregulated. Our proteomic analysis revealed decreased MCM2 and MCM5 protein expressions which was confirmed by western blotting. In conclusion, this study highlights the potential of NaB and calcitriol as a promising therapeutic strategy for HCC.