SMAD2 and retinoblastoma: In agreement with a previous report stating that retinoblastoma cells lack functional TGFβ receptors I and II [30] (Figure 4B and Figure S3B), we identified that ACVRC1 receptors, which is a member of the TGFβ family, could accelerate SMAD2 activations in advanced retinoblastoma [31] (Figure S3C).