Since 5-FU is an S-phase specific drug, and only active during certain cell cycles, those LARC patients, showed higher expression levels of Cellular Growth and Proliferation signature, and c-Myc, could respond better to the treatment Physiologically, c-Myc DNA, mRNA and protein levels are tightly regulated. The high levels of Myc mRNA in LARC could be attributed to gain of c-Myc DNA or aberrant transcriptional activation. However, when we examined rectal tumors before CRT, we found no evidence of gene amplification, according to previous colorectal studies. While higher c-Myc mRNA expression levels correlated with response to treatment, a non significant correlation was found in our study between c-Myc mRNA overexpression in the tumor and c-Myc gene amplification, suggesting that overexpression of c-Myc also can occur via mechanisms independent of gene amplification, such as chromosomal translocations, point mutations in the coding sequence of the promoter region, or activation/deactivation of trans-activating factors. Finally, we studied the relationship between c-Myc mRNA and protein expression levels. Previous studies have recognized the diagnostic significance of immunohistochemical analysis for c-Myc in human rectal cancers although the limited amounts of pre-treatment biopsy material impede the analysis of c-Myc at the protein level. In interpreting our gene expression data, we generally assume that protein levels in these tissue samples reflect the expression of their corresponding mRNAs. However, both responder and nonresponder tumor patients overexpressed c-Myc protein independently of their c-Myc RNA expression levels. Biological reasons for this poor correlation between c-Myc mRNA and protein levels could include post-translational modifications, as well as the protein’s half-live. We acknowledge that this needs not to be the case, as post-transcriptional, translational and protein degradation controls probably have a significant influence in LARC. Novel observations from this study were the distinct expression of c-Myc in adenocarcinoma and its adjacent normal tissue samples, and the range of c-Myc protein expression in LARC. Protein stability is often a limiting factor for the application, engineering and structural studies of proteins. Low protein stability can result in aggregation, susceptibility to protease degradation and poor yields in the expression of BI-D1870 soluble protein, thereby complicating the study and use of these proteins. For commercial applications, proteins commonly need to be particularly stable to increase their tolerance to process conditions like high temperatures or organic solvents. Furthermore, proteins with low stability are less tolerant to mutations thereby limiting further engineering because even slightly destabilizing mutations can lead to unfolding. This can create situations where mutations that would improve enzyme activity in a protein engineering project appear ineffective because the enzyme was not stable enough to remain folded.