Background: Although alterations in the somatic genome are known to influence tumorigenesis, our laboratory has demonstrated that germline variation plays a pivotal role as well, shaping oncogenic signaling to drive neuroblastoma oncogenicity. We showed that common variation at the LIN28B locus influences neuroblastoma susceptibility, and acts in cis to drive LIN28B overexpression. LIN28B, an RNA binding protein implicated in Wilms tumor, hepatoblastoma/hepatocellular carcinoma, and colon cancer, inhibits the let-7 family of tumor suppressor microRNAs and directly binds mRNAs. We recently described a LIN28B-mediated oncogenic network within neuroblastoma, linking LIN28B to RAN GTPase and Aurora kinase A signaling and sought to define additional key LIN28B-mediated signaling networks.
Methods: Using pooled siRNAs, we transiently depleted LIN28B in three neuroblastoma cell lines, isolated RNA, and performed RNA sequencing. We used gain and loss of function approaches to manipulate transcripts of interest, and then measured effects on downstream signaling, protein-RNA interactions, and proliferation.
Results and Conclusions: We identified JARID2 as a novel LIN28B target, as it was within the top ten most differentially regulated genes (6/10) across 18 samples and was strongly correlated with LIN28B expression in neuroblastoma tumors (p<0.0005). JARID2, a member of the Polycomb family, interacts with both chromatin and long non-coding RNAs, and, in embryonic stem cells, balances self-renewal and differentiation. We next demonstrated that LIN28B regulates JARID2 mRNA and protein expression. largely through direct binding of LIN28B to JARID2 mRNA. As the role of JARID2 in tumorigenesis is incompletely understood, we further focused on the role of JARID2 itself, demonstrating that JARID2 enhances cell proliferation. Currently, we are studying whether JARID2 affects cell cycle progression or apoptosis to influence neuroblastoma proliferation. In summary, our findings link LIN28B to JARID2, suggesting a potential mechanism by which LIN28B might influence the neuroblastoma epigenome.