Also of interest, according to the genomic alterations in the 102-retinoblastoma cohort [23], retinoblastomas often show gains in genes expressing factors involved in the pyrimidine ribonucleotide salvage pathway and in particular, gains in chr6p21.1 (containing SLC29A1 gene for the ENT1 uridine transporter) and/or gains in genes expressing uridine kinases (chr1q24.1, including UCK2 and chr20q13.33, including UCKL1). Here, UCKL1 is linked to retinoblastoma.