Only FISH was used in this project in an effort to avoid methodol

Only FISH was used in this project in an effort to avoid methodological bias due to differences in tissue handling. Insufficient hybridisation is always recognised in FISH due to the absence of signals, if suboptimal tissue processing interferes with http://www.selleckchem.com/products/Rapamycin.html the hybridisation. Regarding immunohistochemical analysis, false negative results cannot occur in FISH analysis, because lack of any signals renders a FISH analysis non�\interpretable but not (false) negative. In contrast, by immunohistochemical analysis it is not possible to distinguish a true negative result (absence of the antigen) from a false negative result (loss of immunoreactivity due to suboptimal tissue fixation). However, section thickness, incubation time, data evaluation can all influence FISH results.

The definition used for amplification (ratio of gene copy number�\to�\centromere copy number 2.0) reflects the currently used standard. However, this value was established in breast cancer HER2/neu studies where the majority of amplified cases had ratios >5.0 and where the few cases with a borderline ratio (2 to 4) were too rare to have a major impact on statistical analyses. It is noteworthy that the general amplification pattern in cases with colon cancer is not comparable to HER2 findings in patients with breast cancer. Here, for all genes, most ��amplified�� cases had ratios ranging between 2.0 and 4.0. This may indicate a much lower genomic instability of colon cancer as compared with breast cancer, and may also suggest a different biological significance of ��amplifications�� according to the definitions used in this study in colon cancer than in breast cancer.

Using these established criteria, a relevant fraction of MYC amplifications was observed in colon cancer. This is consistent with previous studies describing 48�C60% 8q over�\representations in studies performing comparative genomic hybridisation,14,15,16 Southern blot17 and FISH analysis.18 An additional study using the Southern blot method detected low�\level amplification in approximately one�\third of cases with colon carcinoma.19 Furthermore, these authors reported that amplification of c�\myc identified patients with stage II and stage III colon cancer with increased disease�\free and overall survival after 5 FU�\based therapy. In contrast with previous studies (maximum of 149 patients included),20 our patient set was large enough to investigate the potential clinical significance of MYC amplifications.

The absence of associations between MYC amplification and unfavourable pathological or clinical features was disappointing. Previous large�\scale amplification analyses had almost always found gene amplification��a hallmark of AV-951 genomic instability��to be related to unfavourable tumour features��for example, in cases with breast and bladder cancers.

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