CYP24A1 and Hypercalcemia: As administration of vitamin D3 in its biologically inactive form has not increased systemic calcium levels; we could exclude hypercalcaemia as a side‐effect, which is often observed when administrating 1,25‐D3.13 Local metabolism of 1,25‐D3 in extra‐renal tissues does not affect circulating levels of 25‐D3.32 Thus we did not expect that overexpression of CYP24A1 in xenografts would affect systemic 25‐D3 levels.