4. Somatic TP53 (p53) Mutations in Colorectal Cancer
The p53 protein functions as a key transcriptional regulator in cell cycle regulation, apoptosis, gene transcription, DNA repair and angiogenesis [18,19,20]. Loss of wildtype TP53 function facilitates the continued growth and the acquisition of invasive properties [21]. Mutations within the TP53 gene are the most frequent genetic alterations in human cancer such as CRC. The GeneChip p53 assay is based on the recently developed oligonucleotide microarray technology. By screening primary colon cancer samples the assay was able to detect TP53 mutations in 65% of tumors [22]. Direct sequencing confirmed the presence of these TP53 mutations. By comparing the two methods, the GeneChip assay revealed several advantages, i.e., higher throughput, higher sensitivity for point mutations and less expenditure of work [23,24]. In contrast the inability to detect deletions or insertions >1 bp and frameshift mutations demonstrates the limitation of the GeneChip assay. Nevertheless, GeneChip has an adequate sensitivity to detect TP53 point mutations in primary colon cancers. Takahashi and colleagues concluded that the GeneChip p53 assay could be applicable to screening procedures in clinical samples but this potential application has to be confirmed in follow-up studies [22].