Next, to assess the effect of CUL4B on the breast CSC population, MCF‐7 cells engineered to stably express firefly luciferase lentiviruses carrying an empty vector or CUL4B were subcutaneously injected into the mammary fat pads of NOD/SCID mice at limit dilutions (2 × 106, 1 × 106, 1 × 105, 1 × 104, and 1 × 103) to determine their tumor formation ability. Here, CUL4B is linked to neoplasm.