Abstract
BackgroundTumour stem cells are considered important to promote disease progression, recurrence and treatment resistance following chemotherapy in colon cancer. However, genomic analyses of colorectal cancer have mainly been performed on integrated tumour tissue consisting of several different cell types in addition to differentiated tumour cells. The purpose of the present study was to compare genomic alterations in two cell fractions enriched of CD133+ and CD133−/EpCAM+ cells, respectively, obtained from fresh intraoperative human tumour biopsies.MethodsThe tumour biopsies were fractionated into CD133+ and CD133−/EpCAM+ cells by immunomagnetic separation, confirmed by immunocytochemistry and Q-PCR. DNA were extracted and used for array comparative genome hybridization (aCGH) after whole genome amplification. Frozen tumour tissue biopsies were used for DNA/RNA extraction and Q-PCR analyses to check for DNA alterations detected in the cell fractions.ResultsThe number and size of DNA alterations were equally distributed across the cell fractions; however, large deletions were detected on chromosome 1, 7 and 19 in CD133−/EpCAM+ cells. Deletions were frequent in both cell fractions and a deletion on chromosome 19p was confirmed in 90% of the patients.ConclusionIsolation of enriched cells derived from tumour tissue revealed mainly genomic deletions, which were not observed in tumour tissue DNA analyses. CD133+ cells were genetically heterogeneous among patients without any defined profile compared to CD133−/EpCAM+ cells.
Highlights
Tumour stem cells are considered important to promote disease progression, recurrence and treatment resistance following chemotherapy in colon cancer
Immuno-cytochemical detection of CD133 expression in the tumour cell fractions CD133 protein expression was evaluated in 4 samples by immunocytochemistry to demonstrate that CD133+ and CD133- cell fractions were separated into two cell populations with different expression of CD133
Gene expression of stem cell markers Transcript levels of known cancer stem cell genes indicated that the CD133+ cell population expressed higher levels of such genes
Summary
Tumour stem cells are considered important to promote disease progression, recurrence and treatment resistance following chemotherapy in colon cancer. The purpose of the present study was to compare genomic alterations in two cell fractions enriched of CD133+ and CD133−/EpCAM+ cells, respectively, obtained from fresh intraoperative human tumour biopsies. Frozen tumour tissue biopsies were used for DNA/ RNA extraction and Q-PCR analyses to check for DNA alterations detected in the cell fractions. Current chemotherapies that target proliferating cells are assumed to meet considerable levels of resistance from CSC in solid tumours since CSC proliferate at slow rates compared to differentiated tumour cells and normal cells [2]. Little is known about genomic changes of CD133+ cells compared to differentiated tumour cells within solid tumours. The aim of the present study was to compare genomic changes in CD133+ cells versus differentiated
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