title: Aberrant BLM cytoplasmic expression associates with DNA damage stress and hypersensitivity to DNA-damaging agents in colorectal cancer.
abstract: BACKGROUND
  Bloom syndrome is a rare and recessive disorder characterized by loss-of-function mutations of the BLM gene, which encodes a RecQ 3'-5' DNA helicase. Despite its putative tumor suppressor function, the contribution of BLM to human sporadic colorectal cancer (CRC) remains poorly understood.
  
  
  METHODS
  The transcriptional regulation mechanism underlying BLM and related DNA damage response regulation in independent CRC subsets and a panel of derived cell lines was investigated by bioinformatics analysis, the transcriptomic profile, a CpG island promoter methylation assay, Western blot, and an immunolocalization assay.
  
  
  RESULTS
  In silico analysis of gene expression data sets revealed that BLM is overexpressed in poorly differentiated CRC and exhibits a close connection with shorter relapse-free survival even after adjustment for prognostic factors and pathways that respond to DNA damage response through ataxia telangiectasia mutated (ATM) signaling. Functional characterization demonstrated that CpG island promoter hypomethylation increases BLM expression and associates with cytoplasmic BLM mislocalization and increased DNA damage response both in clinical CRC samples and in derived cancer cell lines. The DNA-damaging agent S-adenosylmethionine suppresses BLM expression, leading to the inhibition of cell growth following accumulation of DNA damage. In tumor specimens, cytoplasmic accumulation of BLM correlates with DNA damage and γH2AX and phosphorylated ATM foci and predicts long-term progression-free survival in metastatic patients treated with irinotecan.
  
  
  CONCLUSIONS
  Taken together, the findings of this study provide the first evidence that cancer-linked DNA hypomethylation and cytosolic BLM mislocalization might reflect compromised levels of DNA-repair activity and enhanced hypersensitivity to DNA-damaging agents in CRC patients.
authors.affiliation: Department of Sciences and Technologies, University of Sannio, Via Port'Arsa, 11, 82100, Benevento, Italy.
authors.forename: Carolina
authors.initials: C
authors.lastname: Votino
authors.affiliation: Department of Experimental and Clinical Medicine "Gaetano Salvatore", University "Magna Grecia", 88100, Catanzaro, Italy.
authors.forename: Carmelo
authors.initials: C
authors.lastname: Laudanna
authors.affiliation: Department of Surgery and Oncology, University of Verona, 37129, Verona, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: Parcesepe
authors.affiliation: Medical Oncology Unit, Fatebenefratelli Hospital, 82100, Benevento, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Giordano
authors.affiliation: Department of Pathology, "Mater Salutis" Hospital, 37045, Legnago, VR, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Remo
authors.affiliation: Medical Oncology Unit, Fatebenefratelli Hospital, 82100, Benevento, Italy.
authors.forename: Erminia
authors.initials: E
authors.lastname: Manfrin
authors.affiliation: Department of Sciences and Technologies, University of Sannio, Via Port'Arsa, 11, 82100, Benevento, Italy. massimo.pancione@unisannio.it.|Department of Biochemistry and Molecular Biology, Faculty of Pharmacy, Complutense University, Madrid, Spain. massimo.pancione@unisannio.it.
authors.forename: Massimo
authors.initials: M
authors.lastname: Pancione
mesh_terms: D001260:Ataxia Telangiectasia / Q000235:genetics; D001816:Bloom Syndrome / Q000150:complications / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000209:etiology / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D018899:CpG Islands / Q000235:genetics; D003593:Cytoplasm / Q000378:metabolism; D004249:DNA Damage; D019175:DNA Methylation; D004260:DNA Repair; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods; D020868:Gene Silencing; D006801:Humans; D008297:Male; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D009367:Neoplasm Staging; D012333:RNA, Messenger / Q000235:genetics; D053484:RecQ Helicases / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D015854:Up-Regulation
chemical_list: D004273:DNA, Neoplasm; D009363:Neoplasm Proteins; D012333:RNA, Messenger; C097151:Bloom syndrome protein; D053484:RecQ Helicases
keywords: Bloom syndrome gene; CpG island promoter hypomethylation; DNA damage response; DNA repair; Phosphorylated ataxia telangiectasia mutated; γH2AX