Synergistic effects of vitamin D3 and 5-aza-2′-deoxycytidine on VDR methylation and breast cancer progression

Introduction

Breast cancer (BC) is a highly aggressive disease with limited treatment options. Calcitriol, the active form of vitamin D3, exerts anticancer effects via the vitamin D receptor (VDR), but its efficacy is often reduced by VDR promoter hypermethylation. This study investigates the role of VDR promoter hypermethylation in breast cancer and evaluates the potential of 5-Aza-2dC and vitamin D3 to restore VDR function and enhance therapeutic efficacy.

Methods

BALB/c mice were treated with DMBA to induce VDR promoter hypermethylation. The effects of 5-Aza-2dC and Vitamin D3 on VDR, CYP27B1, and CYP24A1 expression were evaluated to assess their impact on calcitriol signaling and BC proliferation.

Results

DMBA-treated mice exhibited VDR hypermethylation, increased CYP24A1, and decreased VDR and CYP27B1 expression, with significantly enhanced tumor growth. Treatment with 5-Aza-2dC reversed VDR hypermethylation, restored VDR and CYP27B1 expression, and suppressed CYP24A1, leading to reduced tumor size and higher vitamin D3 levels. Vitamin D3 pre-treatment preserved VDR and CYP27B1 expression, reduced CYP24A1, and protected against VDR methylation, decreasing tumor proliferation. Combined treatment with 5-Aza-2dC and vitamin D3 synergistically enhanced VDR demethylation, reduced CYP24A1, increased vitamin D3 levels, and significantly inhibited BC proliferation, reducing tumor size.

Conclusion

Reversing VDR hypermethylation with 5-Aza-2dC and vitamin D3 offers a promising strategy to overcome calcitriol resistance and improve therapeutic outcomes in BC. This combination may enhance the efficacy of vitamin D3-based therapies in BC treatment.