Thesis (M.Sc.) - Cairo University - Faculty of Medicine - Department of Pathology

Background: Increasing evidence has proposed that tumor contains tumor initiating cells or cancer stem cells (CSCs) that are responsible for its progression and relapse. Aldehyde dehydrogenase 1A1 (ALDH1A1) has recently been identified as a marker for cancer stem cells in some human malignancies including colorectal cancer (CRC). Aim of Work: The assessment of immunohistochemical (IHC) expression of ALDH1A1 in different colonic lesions, tracking human colonic stem cells during CRC development and its correlation with the clinicopathological features of such lesions. Methods: This study consisted of 45 cases of colonic tissue sections, selected as 5 cases of normal colonic tissue & 10 cases for each of chronic non specific colitis, inflammatory bowel disease, colonic adenoma & CRC. IHC reactions were carried out by using ALDH1A1 monoclonal antibody. A total score of ALDH1A1 expression is obtained by multiplying the score of staining intensity and score of percentage of positively stained cells to obtain score ranging from 0 up to 12. Results: IHC staining of ALDH1A1 in the selected cases displayed a heterogeneous expression pattern, with differences in the distribution and intensity of pos»itivity. According to ALDH1A1 score, 22 cases (48.9%) were negative, 19 cases (42.2%) were weakly positive, 2 cases (4.4%) were moderately positive & 2 cases (4.4%) were strongly positive. There was no statistical significant correlation detected regarding ALDH1A1 score with age & sex for all the selected cases except in normal colonic tissue cases, a significant correlation was detected regarding ALDH1A1 score with sex (P value = 0.025). Also, there was no statistical significant correlation detected regarding ALDH1A1 score with dysplasia in colonic adenoma cases or with tumor type, site, shape, size, grade & TNM staging in CRC cases (P value > 0.05)

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