Carolina Votino1, Carmelo Laudanna2, Pietro Parcesepe3, Guido Giordano4, Andrea Remo5, Erminia Manfrin4, Massimo Pancione6,7. 1. Department of Sciences and Technologies, University of Sannio, Via Port'Arsa, 11, 82100, Benevento, Italy. 2. Department of Experimental and Clinical Medicine "Gaetano Salvatore", University "Magna Grecia", 88100, Catanzaro, Italy. 3. Department of Surgery and Oncology, University of Verona, 37129, Verona, Italy. 4. Medical Oncology Unit, Fatebenefratelli Hospital, 82100, Benevento, Italy. 5. Department of Pathology, "Mater Salutis" Hospital, 37045, Legnago, VR, Italy. 6. Department of Sciences and Technologies, University of Sannio, Via Port'Arsa, 11, 82100, Benevento, Italy. massimo.pancione@unisannio.it. 7. Department of Biochemistry and Molecular Biology, Faculty of Pharmacy, Complutense University, Madrid, Spain. massimo.pancione@unisannio.it.
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.
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.
Entities:
Keywords:
Bloom syndrome gene; CpG island promoter hypomethylation; DNA damage response; DNA repair; Phosphorylated ataxia telangiectasia mutated; γH2AX
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