Triple-negative breast cancer (TNBC) is an aggressive form of breast cancer that disproportionately affects women with darker skin. Epidemiological studies indicate that higher vitamin D levels prevent incidence of TNBC and translate to higher survival rates in those that have TNBC.
The growth inhibition effects of two forms of vitamin D were assessed in MCF-7 and three TNBC lines using CellTiter-Glo. Expression of vitamin D-metabolizing enzymes was measured after vitamin D treatment by quantitative reverse transcription polymerase chain reaction (RT-qPCR).
MCF-7 was growth inhibited by vitamin D at high concentrations but the TNBC lines were not. All cell lines demonstrated large increases in CYP24A1 mRNA levels under vitamin D treatment but there was little change in CYP27B1 or VDR mRNA levels.
These TNBC cell lines are resistant to growth inhibition by vitamin D. This could be due to large inactivation of vitamin D by CYP24A1 or by another mechanism.