Abstract: OBJECTIVE: To develope a solution which could be used for preserving DNA samples in fecal samples from individuals who participated in early colorectal cancer screening. METHODS: An original formula was modified for this investigation. Fecal samples were stored at room temperature for 3 and 7 days,and freezing and thawing at -80℃ within the 7 days. Then,agarose gel electrophoresis (the qualitative method) and real-time fluorescent quantitative PCR (qPCR,the semi-quantitative method) were used for detecting presence of the human housekeeping β-globin gene. Usefulness of our modified preservation solution wascompared to similar international preservation solutions using 501 of the fecal samples. RESULTS: The agarose gel electrophoresis band did not change significantly after the fecal samples were stored at room temperature for 3 and 7 days. The qPCR results as measured using the ΔC_t value were less than or equal to 0.2. After freezings and thawings,the agarose gel electrophoresis results remained the same and ΔC_t value for the qPCR results was less than 1. Compared with the international preservation solutions,our solution showed more clear bands and less changes of the ΔC_t value. Using our solution,effectiveness in preserving fecal samples for DNA analysis was >70% compared to <40% if no preservation solutions were used. CONCLUSION: Our data indicate that our preservation solution was both economical and effective in preserving fecal samples after cold-chain transportation and in inhibiting proliferation of microorganisms. Our solution is therefore useful for use in large-scale colorectal cancer screening.

Key words: feces, sample preservation solution, fecal DNA, colorectal cancer, early screening