ICAD Deficiency in Human Colon Cancer and Predisposition to Colon Tumorigenesis: Linkage to Apoptosis Resistance and Genomic Instability

Abstract

We previously showed that DNA fragmentation factor, which comprises a caspase-3-activated DNase (CAD) and its inhibitor (ICAD), may influence the rate of cell death by generating PARP-1-activating DNA breaks. Here we tested the hypothesis that ICAD-deficient colon epithelial cells exhibiting resistance to death stimuli may accumulate additional genetic modifications, leading to a tumorigenic phenotype. We show that ICAD deficiency may be associated with colon malignancy in humans. Indeed, an examination of ICAD expression using immunohistochemistry in an array of both colon cancer and normal tissues revealed that ICAD expression levels were severely compromised in the cancerous tissues. Upon DNA damage caused by a low dose of irradiation, ICAD cells acquire a tumorigenic phenotype. Colon epithelial cells derived from ICAD mice showed a significant resistance to death induced by the colon carcinogen dimethylhydrazine in vitro and in mice. Such resistance was associated with a decrease in PARP-1 activation. In an animal model of dimethylhydrazine-induced colon tumorigenesis, ICAD−/− mice developed significantly higher numbers of tumors with markedly larger sizes than the wild-type counterparts. Interestingly, the phenotype of the ICAD−/− mice was not associated with a significant increase in the precancerous aberrant crypt foci suggesting a potential link to tumor progression rather than initiation. More importantly, ICAD deficiency was associated with severe genomic instability as assessed by array comparative genomic hybridization. Such genomic instability consisted most prominently of amplifications but with sizable deletions as compared to the wild-type counterparts affecting several cancer-related genes including RAF-1, GSN, LMO3, and Fzd6 independently of p53. Altogether, our results present a viable case for the involvement of ICAD deficiency in colon carcinogenesis and show that apoptosis and genomic instability may comprise the means by which such deficiency may contribute to the process of increasing susceptibility to carcinogen-induced tumorigenesis.

Expressions of SH3BP5, LMO3, and SNAP25 in diffuse large B‐cell lymphoma cells and their association with clinical features

“…Recently, aberrant LMO3 expression in other various types of malignant cells has been reported 27, 28, 29. Our samples examined also did not include any neuronal tissue, so that the further investigation of the LMO3 expression is valuable for understanding its exact role in both normal and tumor cells.…”

ApoE deficiency promotes colon inflammation and enhances the inflammatory potential of oxidized-LDL and TNF-α in primary colon epithelial cells

“…Mice were killed by carbon dioxide asphyxiation and blood was drawn by cardiac puncture. The colons were collected and prepared for primary CECs isolation, RNA or protein extraction or fixation with formalin as described [ 13 ]. Tissue sections were subjected to haematoxylin and eosin (H&E) staining or immunohistochemistry with antibodies specific to proliferating cell nuclear antigen (PCNA) (Santa Cruz Biotechnology) as described previously [ 13 ].…”

“…CECs were isolated essentially as described previously [ 13 ] with minor modifications. Briefly, colons were extracted from 6 weeks old mice and cleaned with cold calcium and magnesium-free Hanks balanced salt solution (HBSS) and then cut into smaller pieces for partial digestion with a cocktail of collagenase I (Sigma–Aldrich) and dispase (Thermo Fisher Scientific) in a complete Dulbecco's Modified Eagle's medium (DMEM) media.…”

“…Cells were monitored for quality and used when they reach 80–90% confluency (∼10 days). Quality of CECs was monitored by immunofluorescence with pan-cytokeratin antibodies (Santa Cruz Biotech) and counterstained with DAPI as described [ 13 ]. Prior to treatment with oxLDL (Sigma–Aldrich) or TNF-α (Roche Applied Science), cells were starved for 5 h by incubation in serum-free medium containing 0.5% cell culture-tested BSA (Sigma–Aldrich).…”

Epigenetics Territory and Cancer

“…Moreover, this deficiency increases susceptibility to carcinogen-induced tumorigenesis through apoptosis and genomic instability (Errami et al 2013). This factor is composed of a caspase-3-activated DNase (CAD) and its inhibitor (ICAD).…”