One of the diseases related to cone cells present in retina is retinoblastoma. Retinoblastoma is a rare cancer of the retina, caused by the mutation of both copies of retinoblastoma genes (RB1). Most cases of retinoblastoma occur during early childhood. One or both eyes may be affected. The protein encoded by RB1 regulates a signal transduction pathway while controlling the cell cycle progression as normally. Retinoblastoma seems to originate in cone precursor cells present in the retina that consist of natural signalling networks which restrict cell death and promote cell survival after losing the RB1, or having both the RB1 copies mutated. It has been found that TRβ2 which is a transcription factor specifically affiliated with cones is essential for rapid reproduction and existence of the retinoblastoma cell. A drug that can be useful in the treatment of this disease is MDM2 (murine double minute 2) gene. Knockdown studies have shown that the MDM2 gene silences ARF-induced apoptosis in retinoblastoma cells and that MDM2 is necessary for the survival of cone cells.