CD133 is a membrane molecule that has been, controversially, reported as a CSC marker in colorectal cancer (CRC). In this study, we sought to clarify the expression and role of CD133 in CRC. Initially the size of the CD133−expressing (CD133+) population in eight well-described CRC cell lines was measured by flow cytometry and was found to range from 0% to >95%. The cell line HT29 has a CD133+ population of >95% and was chosen for functional evaluation of CD133 after gene knockdown by RNA interference. A time course assay showed that CD133 inhibition had no significant effect on cell proliferation or apoptosis. However, CD133 knockdown did result in greater susceptibility to staurosporine-induced apoptosis (p = 0.01) and reduction in cell motility (p<0.04). Since gene knockdown may cause “off-target” effects, the cell line SW480 (which has a CD133+ population of 40%) was sorted into pure CD133+ and CD133− populations to allow functional comparison of isogenic populations separated only by CD133 expression. In concordance with the knockdown experiments, a time course assay showed no significant proliferative differences between the CD133+/CD133− populations. Also greater resistance to staurosporine-induced apoptosis (p = 0.008), greater cell motility (p = 0.03) and greater colony forming efficiency was seen in the CD133+ population than the CD133− population in both 2D and 3D culture (p<0.0001 and p<0.003 respectively). Finally, the plasticity of CD133 expression in tumour cells was tested. Quantitative PCR analysis showed there was transcriptional repression in the CD133− population of SW480. Prolonged culture of a pure CD133− population resulted in re-emergence of CD133+ cells. We conclude that CD133 expression in CRCs is associated with some features attributable to stemness and that there is plasticity of CD133 expression. Further studies are necessary to delineate the mechanistic basis of these features.

Amplification of HER-2 gene and overexpression of HER-2 receptor play a significant role in the progression of a number of malignancies such as breast cancer. Trastuzumab (anti-HER-2 therapeutic agent) has been used successfully in treatment of breast cancer. The aim of this study was to assess the pattern of HER-2 gene amplification and of HER-2 receptor expression in a spectrum of serous and mucinous ovarian tumors to determine whether HER-2 is altered in these neoplasms similar to that occurring in breast cancer. Formalin-fixed paraffin-embedded microarray tissue sections from 212 specimens were stained with HER-2 antibody using immunohistochemistry and with anti-HER-2 DNA probe using chromogenic in situ hybridization. Specimens consisted of 65 benign tumors (50 serous and 15 mucinous), 26 borderline (13 serous and 13 mucinous), 73 malignant tumors (53 serous carcinoma and 20 mucinous carcinoma), 18 metastatic deposits (13 serous and 5 mucinous), in addition to 30 normal tissues (16 ovarian surface and 14 normal fallopian tube). HER-2 protein-positive expression was not detected in the normal or the benign tissues. Borderline neoplasms showed positive staining, but no overexpression. HER-2 overexpression was seen only in 4 carcinoma specimens: 1/53 (1.8%) primary serous carcinomas and 3/20 (15%) primary mucinous carcinomas. HER-2 gene amplification was seen in 4 specimens: 2 primary mucinous carcinomas and 2 malignant deposits of these 2 mucinous carcinomas. In conclusion, alteration of HER-2 was not detected in ovarian serous neoplasms; however, in mucinous carcinoma, HER-2 amplification and overexpression occur.