PDCD4 and retinoblastoma: Accordingly, an overall decrease in circRNA expression levels was demonstrated in RB by Lyu et al. (Lyu et al., 2019a), who further reported that TET1-hsa_circ_0093996 expression was downregulated in both primary and recurrent RB samples, which led to an increase in miR-183 levels and ultimately to a reduction in the expression of the tumor suppressor programmed cell death 4 (PDCD4).