HELLS and retinoblastoma: At the protein level, we identified overexpression of UHRF1 and HELLS in a subset of the human retinoblastoma tumors and in all the human retinoblastoma cell lines analyzed (RB355, Weri, and Y79) when compared to normal fetal retina (FW19) and normal human fibroblasts (BJ) (Fig. 5C-F).