Ki-67, p53 and bcl-2 analysis in colonic versus rectal adenocarcinoma

This paper develops a comparative study between similar subtypes of colonic and rectal adenocarcinoma, based on their immunohistochemical profiles for Ki-67, p53 and bcl-2 markers, in order to evaluate the prediction value for the investigated markers, according to the histologic subtype and location. Thirty cases of adenocarcinoma were investigated, 15 with colonic and 15 with rectal location. For both locations, the cases included five well-differentiated, five moderately differentiated and five low differentiated subtypes. The immunohistochemical investigation was performed using Ki-67, p53 and bcl-2 antibodies (DAKO) and streptavidin-biotin method (LSAB Kit, DAKO). The semiquantitative analysis of the immunohistochemical reactions was based on the Ki-67 and p53 index, respectively, counted as number of positive cells from 100 positive and negative cells. For bcl-2, the reaction was considered positive, respectively negative, for a percentage of positive cells higher, respectively smaller, than 5%. All 30 cases (100%) were positive for Ki-67. The mean value of Ki-67 index for colonic, respectively rectal adenocarcinoma was 55.8%, respectively 59.6%. No statistical correlation was found between the proliferative activity and location (p=0.502). Ten cases (66%) of colonic adenocarcinoma were positive for p53, with a mean value of 42.5% for p53 index. Eight cases (53%) of rectal adenocarcinoma were positive for p53, with a mean value of 21.1% for p53 index. There was a statistic correlation between the apoptotic activity and location (p=0.005). The positive reaction for bcl-2 was present in seven (46.6%) and nine (60%) from the 15 cases of colonic and, respectively, rectal adenocarcinoma. The statistic analysis revealed that bcl-2 cannot be significantly associated with any of the two locations (p=0.48144, 95% CI). The use of the Wald tests permitted the assessment of the predictive power for the investigated markers according to the pathologic subtype and location. Thus, p53 is on the first position (W=16.56, p=0.00004, 95% CI), followed by Ki-67 (W=4.49, p=0.034, 95% CI), whereas bcl-2 cannot be considered a predictive factor (W=2.5, p=0.107, 95% CI). The immunohistochemical evaluation of Ki-67, p53 and bcl-2 yields refined information on colorectal tumor biology. Our study confirms, from the statistic point of view, the role of p53, followed by Ki-67, as predictive factors.