Gene expression in colorectal neoplasia: modifications induced by tissue ischaemic time and tissue handling protocol

Abstract

Reliable interpretation of results of gene expression at the mRNA level requires standardized protocols for tissue procurement.

Effects of Cold Ischemia on Gene Expression: A Review and Commentary

“…Nevertheless, based on the literature, the major tumors of breast, colorectum, liver, and prostate are unlikely to have major molecular damage secondary to typical times of cold ischemia. 3,6,[8][9][10][11][12][13][14][15][16][17][18] Effects of Cold Ischemia of RNA Stability RNA integrity number (RIN) is a surrogate measure of mRNA stability. RIN specifically is an indication of the stability of ribosomal RNA (rRNA) based on the two major peaks of rRNA, 18S and 28S.…”

“…Of note, the stability of mRNA is assumed to be very similar to RIN or the 28S:18S rRNA ratio, but this has not been studied adequately and likely varies with a specific transcript and organ system. 3,[10][11][12][13][14][15][16][17] Importantly, most studies of RIN or 28S:18S ratios are performed with specimens held at room temperature (usually assumed to be 22°C-25°C) and some studies of the effects of cold ischemia focus only on the cold ischemia period after specimens leave the operating room and/or arrive in surgical pathology and do not consider the period of cold ischemia in the operating room or during transport. 19 More importantly, most studies do not evaluate the effects of warm ischemia, which is likely to interact with the effects of cold ischemia.…”

“…19 More importantly, most studies do not evaluate the effects of warm ischemia, which is likely to interact with the effects of cold ischemia. [10][11][12][13] Nevertheless, the following question remains: How are RIN and/or 28S:18S ratios affected by different times of cold ischemia? Multiple studies have reported that there is no statistical difference in RIN and/or there are minimal changes in RIN (£10%) or 28S:18S ratios during cold ischemia times of 1-6 hours.…”

“…Multiple studies have reported that there is no statistical difference in RIN and/or there are minimal changes in RIN (£10%) or 28S:18S ratios during cold ischemia times of 1-6 hours. 3,[10][11][12][13][14][15][16][17]19,20 Few studies report large and/or statistically significant changes in RIN, except studies that held specimens at 37°C or at 60°C where decreases in RIN of about 50% were reported at 3.15 hours at 60°C. 3,13 An outlier is a study in which colorectal cancer specimens were held at 4°C, but RIN decreased 44% (statistically significant) between 10 minutes and 1.5 hours; however, the changes in 28S:18S ratios were not statistically different.…”

“…Some of these transcripts are associated with specific genes and their proteins, but other transcripts are to unknown genes and/or genes with no clearly identified functions. In most reported studies of changes in transcripts during cold ischemia usually at RT, typically less than 1%-3% of transcripts statistically change over the initial 2-3 hours of cold ischemia, 3,7,[10][11][12]18,23 but up to 10% of transcripts have been reported to change after 6 hours.…”