title: Aberrant methylation of PSD disturbs Rac1-mediated immune responses             governing neutrophil chemotaxis and apoptosis in ulcerative colitis-associated             carcinogenesis.
abstract: We previously reported that the Pleckstrin and Sec7 domain-containing (PSD)             gene is preferentially methylated in patients with ulcerative colitis (UC) who             developed colorectal cancer (CRC), and is implicated in UC-associated carcinogenesis             through its inhibition of apoptosis. This study aimed to determine the potential             effect of PSD methylation on its downstream molecule, Ras-related C3 botulinum             toxin substrate 1 (Rac1), which governs neutrophil chemotaxis and apoptosis signaling.             PSD was knocked down in a normal human fibroblast cell line (HNDF) and a neutrophil-like             cell line (HL-60). Both NHDF and HL-60 cells exhibited numerous filamentous-actin             (F-actin) rich membrane extensions, resulting in the activation of Rac1; this             activation was hampered by PSD silencing. Lipopolysaccharide, a reactive oxygen             species (ROS) inducer, stimulated NHDF cells to release ROS and activated caspase‑3/7             in the presence of neutrophils, which was inhibited by PSD knockdown. Migration             assays demonstrated that chemotaxis of HL-60 cells was affected by PSD silencing             in NHDF cells. Tissue sections from 6 UC patients with CRC and 15 UC patients             without CRC were examined. To verify Rac1-mediated chemotaxis in tissue sections,             we evaluated the grade of neutrophil infiltration by histological assessment and             assessed F-actin and PSD expression by immunohistochemistry. Neutrophil infiltration,             F-actin and PSD expression were significantly decreased in specimens from UC patients             with PSD methylation compared with those without. Decreased levels of F-actin             expression were observed in colorectal mucosa, as well as in infiltrating cells             with PSD methylation. PSD expression was preferentially inhibited in colorectal             mucosa by PSD methylation, whereas PSD expression was rarely observed in infiltrating             cells, regardless of PSD methylation status. These data indicate that aberrant             methylation of PSD occurs in UC-associated colorectal mucosa, enabling circumvention             of Rac1-mediated immune responses governing neutrophil chemotaxis and apoptosis,             and thus plays a pivotal role in the mechanisms underlying UC-associated carcinogenesis.
authors.affiliation: Department of Surgery, Saitama Medical Center, Jichi Medical                     University, 1-847 Amanuma-cho, Omiya-ku, Saitama 330-8503, Japan.
authors.forename: Takaharu
authors.initials: T
authors.lastname: Kato
authors.forename: Koichi
authors.initials: K
authors.lastname: Suzuki
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Okada
authors.forename: Hidenori
authors.initials: H
authors.lastname: Kamiyama
authors.forename: Takafumi
authors.initials: T
authors.lastname: Maeda
authors.forename: Masaaki
authors.initials: M
authors.lastname: Saito
authors.forename: Kei
authors.initials: K
authors.lastname: Koizumi
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Miyaki
authors.forename: Fumio
authors.initials: F
authors.lastname: Konishi
mesh_terms: D000199:Actins / Q000378:metabolism; D000328:Adult; D000368:Aged; D017209:Apoptosis / Q000235:genetics / Q000276:immunology; D045744:Cell Line, Tumor; D002634:Chemotaxis, Leukocyte / Q000276:immunology; D003093:Colitis, Ulcerative / Q000235:genetics* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D019175:DNA Methylation; D005260:Female; D055785:Gene Knockdown Techniques; D020662:Guanine Nucleotide Exchange Factors; D018922:HL-60 Cells; D006801:Humans; D008297:Male; D008875:Middle Aged; D009419:Nerve Tissue Proteins / Q000172:deficiency / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D009504:Neutrophils / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D017382:Reactive Oxygen Species / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000276:immunology* / Q000378:metabolism
chemical_list: D000199:Actins; D020662:Guanine Nucleotide Exchange Factors; D009419:Nerve Tissue Proteins; C109970:PSD protein, human; C107953:RAC1 protein, human; D017382:Reactive Oxygen Species; D020830:rac1 GTP-Binding Protein