DNTT and cancer: 1,25(OH)2D3 studies of cancer and other cell lines have shown an increase in the rate of cell death by apoptosis.17, 18, 19, 20 However, 1,25(OH)2D3 does not always induce apoptosis.17, 21 We next asked whether retinal PC undergo apoptosis in response to 1,25(OH)2D3 and evaluated the late stage of apoptosis using a TdT‐dUTP TUNEL assay.