Project description:The let-7 microRNA families are tumor suppressors often deregulated in cancer, yet the underlying mechanisms of let-7 disruption remain poorly understood. Neuroblastoma is defined in part by poor prognosis associated with genetic amplification of MYCN, itself a let-7 target. The let-7 biogenesis inhibitor LIN28B has been implicated as a critical regulator of MYCN ; however, here we show that LIN28B is dispensable for both MYCN protein expression and growth of MYCN amplified neuroblastoma cell lines despite robust de-repression of let-7 . We further report that amplified MYCN mRNA is a potent let-7 sponge that through exceptionally high expression defines a sub-set of self-sponging amplified competing endogenous RNA (aceRNA) and reconciles the dispensability of LIN28B . In addition, we observe frequent genomic loss of let-7 that inversely associates with MYCN- amplification, providing an explanation for common, yet unresolved amplification-independent patterns of chromosome loss. We thus propose a model whereby let-7 disruption by genetic loss, LIN28B expression, or aceRNA sponging is a unifying mechanism of neuroblastoma pathogenesis. Indeed, our data show that the majority of neuroblastomas have at least one let-7 disruption event and that genetic loss in non-MYCN amplified tumors marks decreased survival, further underscoring its importance. The inverse relationship between allelic loss and sponging of let-7 from highly expressed or amplified oncogenes may have broad implications for oncogenesis. BE(2)C:MYCN-ORF cells transfected with siRNA and miRNA mimics
Project description:The let-7 microRNA families are tumor suppressors often deregulated in cancer, yet the underlying mechanisms of let-7 disruption remain poorly understood. Neuroblastoma is defined in part by poor prognosis associated with genetic amplification of MYCN, itself a let-7 target. The let-7 biogenesis inhibitor LIN28B has been implicated as a critical regulator of MYCN ; however, here we show that LIN28B is dispensable for both MYCN protein expression and growth of MYCN amplified neuroblastoma cell lines despite robust de-repression of let-7 . We further report that amplified MYCN mRNA is a potent let-7 sponge that through exceptionally high expression defines a sub-set of self-sponging amplified competing endogenous RNA (aceRNA) and reconciles the dispensability of LIN28B . In addition, we observe frequent genomic loss of let-7 that inversely associates with MYCN- amplification, providing an explanation for common, yet unresolved amplification-independent patterns of chromosome loss. We thus propose a model whereby let-7 disruption by genetic loss, LIN28B expression, or aceRNA sponging is a unifying mechanism of neuroblastoma pathogenesis. Indeed, our data show that the majority of neuroblastomas have at least one let-7 disruption event and that genetic loss in non-MYCN amplified tumors marks decreased survival, further underscoring its importance. The inverse relationship between allelic loss and sponging of let-7 from highly expressed or amplified oncogenes may have broad implications for oncogenesis. Two cell lines, sampled in triplicate.
Project description:The let-7 microRNA families are tumor suppressors often deregulated in cancer, yet the underlying mechanisms of let-7 disruption remain poorly understood. Neuroblastoma is defined in part by poor prognosis associated with genetic amplification of MYCN, itself a let-7 target. The let-7 biogenesis inhibitor LIN28B has been implicated as a critical regulator of MYCN ; however, here we show that LIN28B is dispensable for both MYCN protein expression and growth of MYCN amplified neuroblastoma cell lines despite robust de-repression of let-7 . We further report that amplified MYCN mRNA is a potent let-7 sponge that through exceptionally high expression defines a sub-set of self-sponging amplified competing endogenous RNA (aceRNA) and reconciles the dispensability of LIN28B . In addition, we observe frequent genomic loss of let-7 that inversely associates with MYCN- amplification, providing an explanation for common, yet unresolved amplification-independent patterns of chromosome loss. We thus propose a model whereby let-7 disruption by genetic loss, LIN28B expression, or aceRNA sponging is a unifying mechanism of neuroblastoma pathogenesis. Indeed, our data show that the majority of neuroblastomas have at least one let-7 disruption event and that genetic loss in non-MYCN amplified tumors marks decreased survival, further underscoring its importance. The inverse relationship between allelic loss and sponging of let-7 from highly expressed or amplified oncogenes may have broad implications for oncogenesis. Three cell lines, sampled in triplicate.
Project description:The let-7 microRNA families are tumor suppressors often deregulated in cancer, yet the underlying mechanisms of let-7 disruption remain poorly understood. Neuroblastoma is defined in part by poor prognosis associated with genetic amplification of MYCN, itself a let-7 target. The let-7 biogenesis inhibitor LIN28B has been implicated as a critical regulator of MYCN ; however, here we show that LIN28B is dispensable for both MYCN protein expression and growth of MYCN amplified neuroblastoma cell lines despite robust de-repression of let-7 . We further report that amplified MYCN mRNA is a potent let-7 sponge that through exceptionally high expression defines a sub-set of self-sponging amplified competing endogenous RNA (aceRNA) and reconciles the dispensability of LIN28B . In addition, we observe frequent genomic loss of let-7 that inversely associates with MYCN- amplification, providing an explanation for common, yet unresolved amplification-independent patterns of chromosome loss. We thus propose a model whereby let-7 disruption by genetic loss, LIN28B expression, or aceRNA sponging is a unifying mechanism of neuroblastoma pathogenesis. Indeed, our data show that the majority of neuroblastomas have at least one let-7 disruption event and that genetic loss in non-MYCN amplified tumors marks decreased survival, further underscoring its importance. The inverse relationship between allelic loss and sponging of let-7 from highly expressed or amplified oncogenes may have broad implications for oncogenesis.
Project description:The let-7 microRNA families are tumor suppressors often deregulated in cancer, yet the underlying mechanisms of let-7 disruption remain poorly understood. Neuroblastoma is defined in part by poor prognosis associated with genetic amplification of MYCN, itself a let-7 target. The let-7 biogenesis inhibitor LIN28B has been implicated as a critical regulator of MYCN ; however, here we show that LIN28B is dispensable for both MYCN protein expression and growth of MYCN amplified neuroblastoma cell lines despite robust de-repression of let-7 . We further report that amplified MYCN mRNA is a potent let-7 sponge that through exceptionally high expression defines a sub-set of self-sponging amplified competing endogenous RNA (aceRNA) and reconciles the dispensability of LIN28B . In addition, we observe frequent genomic loss of let-7 that inversely associates with MYCN- amplification, providing an explanation for common, yet unresolved amplification-independent patterns of chromosome loss. We thus propose a model whereby let-7 disruption by genetic loss, LIN28B expression, or aceRNA sponging is a unifying mechanism of neuroblastoma pathogenesis. Indeed, our data show that the majority of neuroblastomas have at least one let-7 disruption event and that genetic loss in non-MYCN amplified tumors marks decreased survival, further underscoring its importance. The inverse relationship between allelic loss and sponging of let-7 from highly expressed or amplified oncogenes may have broad implications for oncogenesis.
Project description:The let-7 microRNA families are tumor suppressors often deregulated in cancer, yet the underlying mechanisms of let-7 disruption remain poorly understood. Neuroblastoma is defined in part by poor prognosis associated with genetic amplification of MYCN, itself a let-7 target. The let-7 biogenesis inhibitor LIN28B has been implicated as a critical regulator of MYCN ; however, here we show that LIN28B is dispensable for both MYCN protein expression and growth of MYCN amplified neuroblastoma cell lines despite robust de-repression of let-7 . We further report that amplified MYCN mRNA is a potent let-7 sponge that through exceptionally high expression defines a sub-set of self-sponging amplified competing endogenous RNA (aceRNA) and reconciles the dispensability of LIN28B . In addition, we observe frequent genomic loss of let-7 that inversely associates with MYCN- amplification, providing an explanation for common, yet unresolved amplification-independent patterns of chromosome loss. We thus propose a model whereby let-7 disruption by genetic loss, LIN28B expression, or aceRNA sponging is a unifying mechanism of neuroblastoma pathogenesis. Indeed, our data show that the majority of neuroblastomas have at least one let-7 disruption event and that genetic loss in non-MYCN amplified tumors marks decreased survival, further underscoring its importance. The inverse relationship between allelic loss and sponging of let-7 from highly expressed or amplified oncogenes may have broad implications for oncogenesis.
Project description:Poor prognosis in neuroblastoma is associated with genetic amplification of MYCN. MYCN is itself a target of let-7, a tumour suppressor family of microRNAs implicated in numerous cancers. LIN28B, an inhibitor of let-7 biogenesis, is overexpressed in neuroblastoma and has been reported to regulate MYCN. Here we show, however, that LIN28B is dispensable in MYCN-amplified neuroblastoma cell lines, despite de-repression of let-7. We further demonstrate that MYCN messenger RNA levels in amplified disease are exceptionally high and sufficient to sponge let-7, which reconciles the dispensability of LIN28B. We found that genetic loss of let-7 is common in neuroblastoma, inversely associated with MYCN amplification, and independently associated with poor outcomes, providing a rationale for chromosomal loss patterns in neuroblastoma. We propose that let-7 disruption by LIN28B, MYCN sponging, or genetic loss is a unifying mechanism of neuroblastoma development with broad implications for cancer pathogenesis.