Project description:Aberrant splicing is a hallmark of many cancers, including Acute Myeloid Leukemia (AML), but its role in post-treatment relapse remains poorly understood. Here, we analyzed the alternative splicing landscape of 19 AML patients during chemotherapy treatment. We found an upregulation of the long isoform of the transcription factor RUNX1 (also known as RUNX1C) in relapsed cohorts, which conferred chemotherapy resistance. Notably, these patients showed elevanted intragenic DNA methylation at the RUNX1 proximal promoter, thereby activating RUNX1C transcript through its alternative distal promoter. Mechanistically the N-terminus region of RUNX1C is required to promote chemoresistance by regulating a distinct RUNX1 transciptional program. Among these target genes, B-cell translocation gene 2 (BTG2) mediates a quiescent-like phenotype by deadenylating ribosomal RNAs to reduce global protein synthesis. Lastly, we harnessed orthogonal RNA-targeting strategies to target RUNX1C isoform, which led to augmented chemotherapy efficacy. Collectively, our finidngs delineate a transcriptional circuity orchestrated by a transcription factor isoform that underpins chemotherapy responsiveness and a potential therapeutic strategy to mitigate disease recurrence.
Project description:Aberrant splicing is a hallmark of many cancers, including Acute Myeloid Leukemia (AML), but its role in post-treatment relapse remains poorly understood. Here, we analyzed the alternative splicing landscape of 19 AML patients during chemotherapy treatment. We found an upregulation of the long isoform of the transcription factor RUNX1 (also known as RUNX1C) in relapsed cohorts, which conferred chemotherapy resistance. Notably, these patients showed elevanted intragenic DNA methylation at the RUNX1 proximal promoter, thereby activating RUNX1C transcript through its alternative distal promoter. Mechanistically the N-terminus region of RUNX1C is required to promote chemoresistance by regulating a distinct RUNX1 transciptional program. Among these target genes, B-cell translocation gene 2 (BTG2) mediates a quiescent-like phenotype by deadenylating ribosomal RNAs to reduce global protein synthesis. Lastly, we harnessed orthogonal RNA-targeting strategies to target RUNX1C isoform, which led to augmented chemotherapy efficacy. Collectively, our finidngs delineate a transcriptional circuity orchestrated by a transcription factor isoform that underpins chemotherapy responsiveness and a potential therapeutic strategy to mitigate disease recurrence.
Project description:Aberrant splicing is a hallmark of many cancers, including Acute Myeloid Leukemia (AML), but its role in post-treatment relapse remains poorly understood. Here, we analyzed the alternative splicing landscape of 19 AML patients during chemotherapy treatment. We found an upregulation of the long isoform of the transcription factor RUNX1 (also known as RUNX1C) in relapsed cohorts, which conferred chemotherapy resistance. Notably, these patients showed elevanted intragenic DNA methylation at the RUNX1 proximal promoter, thereby activating RUNX1C transcript through its alternative distal promoter. Mechanistically the N-terminus region of RUNX1C is required to promote chemoresistance by regulating a distinct RUNX1 transciptional program. Among these target genes, B-cell translocation gene 2 (BTG2) mediates a quiescent-like phenotype by deadenylating ribosomal RNAs to reduce global protein synthesis. Lastly, we harnessed orthogonal RNA-targeting strategies to target RUNX1C isoform, which led to augmented chemotherapy efficacy. Collectively, our finidngs delineate a transcriptional circuity orchestrated by a transcription factor isoform that underpins chemotherapy responsiveness and a potential therapeutic strategy to mitigate disease recurrence.
Project description:Chemoresistance remains a major obstacle to the successful treatment of breast cancer. Especially, more than 80% of cases cannot achieve pathological complete response (pCR) in patients who received neoadjuvant chemotherapy (NAC). Understanding the mechanisms involved in chemoresistance can guide the development of efficient therapies in patients with breast cancer. Herein, we identified a novel p62 isoform with a short 3′UTR (p62-SU, 662-nt) that is associated with chemoresistance by RNA-sequence and verified by qRT-PCR, 3′RACE, and northern blot in breast cancer cells and tissue specimens. Furthermore, enforced expression of p62-SU dramatically promoted the ability of proliferation, migration, invasion, and chemoresistance compared with p62 isoform with a long/full-length 3′UTR (p62-LU, 1485-nt) in vivo and in vitro. Mechanistically, we revealed that CPSF1 could regulate the 3′UTR shorting of p62 by alternative polyadenylation and then enhanced chemoresistance in breast cancer cells. In addition, we found that p62-SU escaped the repression of miR-124-3p and promoted the ability of p62-SU to produce more protein and, subsequently, p62-dependent chemoresistance. Together, our data suggest the p62-SU, generated by CPSF1, plays an essential role in the regulation of breast cancer chemoresistance through CPSF1-p62-miR-124-3p signaling.
Project description:Through alternative processing of pre-mRNAs, individual mammalian genes often produce multiple mRNA and protein isoforms that may have related, distinct or even opposing functions. Here we report an in-depth analysis of 15 diverse human tissue and cell line transcriptomes based on deep sequencing of cDNA fragments, yielding a digital inventory of gene and mRNA isoform expression. Analysis of mappings of sequence reads to exon-exon junctions indicated that ~94% of human genes undergo alternative splicing (AS), ~86% with a minor isoform frequency of 15% or more. Differences in isoform-specific read densities indicated that a majority of AS and alternative cleavage and polyadenylation (APA) events exhibit variation between tissues. Variations in alternative mRNA isoform expression between 6 individuals were also detected in cerebellar cortex, with ~2- to 3-fold less isoform variation observed between individuals than between tissues. Extreme or 'switch-like' regulation of splicing between tissues was associated with increased sequence conservation and with generation of full-length open reading frames. Patterns of AS and APA were strongly correlated across tissues, suggesting coordinated regulation, and sequence conservation of known regulatory motifs in both regulated introns and 3' UTRs suggested common involvement of the same factors in regulation of tissue-specific splicing and polyadenylation. Exam mRNA expression in 15 human tissues and cell lines
Project description:Intra-tumoral heterogeneity can impact the competitive fitness and chemoresistance of individual cancer cells. In acute myeloid leukemia (AML), both genetic and functional heterogeneity contribute to chemoresistance, resulting in relapse after chemotherapy. While the role of cell-extrinsic factors such as interactions with non-leukemic cells has been described for AML relapse, whether interactions between cancer cells affects chemoresistance is not fully known. Here, we demonstrate that a dominant leukemic fraction can suppress the proliferation and expansion of other leukemic cells and that this suppression is reversible. We show that this suppression is mediated in part by both type I and type II intra-leukemic interferon (IFN) signaling and dependent on BST2. Importantly, blocking antibodies to type II IFN receptor activated the cycling of this suppressed cell fraction and sensitized the cells to subsequent chemotherapy treatment. Our findings suggest that interactions between functionally heterogeneous leukemic fractions can affect competitive fitness and treatment response, highlighting IFN signaling as a potential therapeutic target to counter chemoresistance.
Project description:Through alternative processing of pre-mRNAs, individual mammalian genes often produce multiple mRNA and protein isoforms that may have related, distinct or even opposing functions. Here we report an in-depth analysis of 15 diverse human tissue and cell line transcriptomes based on deep sequencing of cDNA fragments, yielding a digital inventory of gene and mRNA isoform expression. Analysis of mappings of sequence reads to exon-exon junctions indicated that ~94% of human genes undergo alternative splicing (AS), ~86% with a minor isoform frequency of 15% or more. Differences in isoform-specific read densities indicated that a majority of AS and alternative cleavage and polyadenylation (APA) events exhibit variation between tissues. Variations in alternative mRNA isoform expression between 6 individuals were also detected in cerebellar cortex, with ~2- to 3-fold less isoform variation observed between individuals than between tissues. Extreme or 'switch-like' regulation of splicing between tissues was associated with increased sequence conservation and with generation of full-length open reading frames. Patterns of AS and APA were strongly correlated across tissues, suggesting coordinated regulation, and sequence conservation of known regulatory motifs in both regulated introns and 3' UTRs suggested common involvement of the same factors in regulation of tissue-specific splicing and polyadenylation.