p53, Bcl-2 and C-Myc expressions in colorectal carcinoma associated with schistosomiasis in Egypt.

BACKGROUND AND AIMS: Oncogenes and tumor suppressor genes expression are well described in bladder cancer associated with schistosomiasis especially in Egypt. Scarce studies were directed to colorectal cancer (CRC) associated with Schistosoma mansoni (S. mansoni). Apoptosis (programmed cell death) and the genes regulating this process (e.g., Bcl-2) have recently become a focus of interest in the study of cancer development and progression. In the present study, we aimed to investigate the expression pattern of p53, Bcl-2 and C-Myc in CRC tissues obtained from Egyptian colorectal cancer patients divided in two different groups, one associated with Schistosoma mansoni (CRC-Sm) and the other without Schistosoma mansoni (CRC-NSm). METHODS: Seventy-five CRC tumors containing 36 draining lymph node metastatic tumors were immunohistochemically stained using specific monoclonal antibodies for p53, Bcl-2 and C-Myc, in addition the apoptotic activity of these tumors were analyzed. RESULTS AND CONCLUSIONS: Regardless of the S. mansoni infection, the obtained results showed that the apoptotic activity was more evident in p53 diffuse positive tumors (P = 0.021). There was a significant correlation between p53 diffuse positive staining and Bcl-2 positive immunostaining (P = 0.011). Signet ring cell carcinoma and mucinous adenocarcinoma exhibited both intense C-Myc expression than non-mucinous carcinoma (P = 0.001). When adjusting for S. mansoni infection, 58.3% of CRC-Sm cases were Bcl-2 positive compared to only (33.3%) of CRC-NSm (P = 0.046). Apoptotic activity was more evident in the latter group than of CRC-Sm tumors (P = 0.009). p53 and C-Myc expressions were found insignificantly different in CRC-Sm compared with CRC-NSm (P > 0.05). These observations suggest that the genotoxic agents produced endogenously through the course of schistosomiasis mansoni may play a role in CRC-Sm pathogenesis through the dysregulation of apoptosis by alteration the expression pattern of Bcl-2 protein differently from CRC-NSm suggesting a different biological behavior.

p53 expression and DNA ploidy pattern in Egyptian colorectal carcinoma.

BACKGROUND/AIMS: p53 gene mutation occurs in about 50-60% of colorectal carcinoma cases. This mostly occurs as a late event in the adenoma-carcinoma sequence. These late stages are associated with more aneuploidy compared to adenomas and early carcinomas. However there is a controversy regarding the relation between p53 overexpression and DNA index. This study was designed to investigate the relationship between p53 status and DNA ploidy pattern. METHODOLOGY: Nuclear DNA content of paraffin-embedded material from 83 colectomy specimens for colorectal carcinoma was measured by flow cytometry. Also, p53 was detected by immunohistochemistry in 73 out of the 83 tumor cases using a monoclonal antibody that detects both wild and mutant p53 proteins (Biogenex 1801). RESULTS: Aneuploidy was identified in 37 cases (46.25%). Tumors with rectal location were significantly more aneuploid in comparison to other sites (P = 0.009), p53 staining showed three patterns: diffuse staining (29 cases), focal (13 cases), and negative (31 cases). Diffuse p53 staining was associated with aneuploidy (P = 0.04). The majority of DNA indices fell within the range 1.1-2.2 (32 out of 37). Twenty-one of these had DNA index = 1.1-1.8 (aneuploidy short of tetraploidy) significantly associated with diffuse p53 staining compared with peritetraploid cases (DNA index 1.8-2.2) (P = 0.034). CONCLUSIONS: p53 immunohistochemistry demonstrates two distinct patterns in colorectal carcinoma. Diffuse p53 staining, which is associated with aneuploidy short of tetraploidy (DNA index 1.1-1.8), a finding which is different from previously published work. Focal p53 staining pattern, in contrast, is related to high G2M and more abnormal tetraploid peaks but less aneuploidy.