ABM: To explore the effect and significance of inhibitor of growth 1 (ING1) gene in carcinogenesis and progression of human sporadic colorectal cancer. METHODS: mRNA expression, mutation, and loss of heterozygosity (LOH) of ING1 gene in 35 specimens of sporadic colorectal cancer tissues and the matched normal mucous membrane tissues were detected by semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), PCR-single strain conformation polymorphism (PCR-SSCP) and PCR-simple sequence length polymorphism (PCR-SSLP) using microsatellite markers, respectively. RESULTS: The average ratios of light intensities of p33ING1b and p47ING1a mRNA expression in the cancerous tissues were significantly lower than those in normal tissues. The difference between the two mRNA splices was not significant in the matched tissues. In addition, the ratios of light intensities of p33ING1b and p47ING1a mRNA expression in the cancerous tissues of Dukes’ stages C and D were significantly lower than those in cancerous tissues of Dukes’ stages A and B. However, no mutation of ING1 gene was detected in all 35 cases; only 4 cases of LOH (11.4%) were found. CONCLUSION: p33ING1b and p47ING1a mRNA expressions are closely related with the carcinogenesis and progression of human sporadic colorectal cancer. No mutation of ING1 gene is found, and there are only few LOH in sporadic coiorectal cancers. These might not be the main reasons for the down regulation of ING1 expression. Its low expression may happen in transcription or post-transcription. METHODS: mRNA expression, mutation, and loss of heterozygosity (LOH) of ING1 gene in 35 specimens of sporadic colorectal cancer tissues and the matched normal mucous membrane tissues were detected by semi-quantitative reverse transcriptase-polymerase chain reaction (PCR-SSCP) and PCR-simple sequence length polymorphism (PCR-SSLP) using microsatellite markers, respectively. RESULTS: The average ratios of light intensities of p33ING1b and p47ING1a mRNA expression in the cancerous tissues were significantly lower than those in normal tissues. The difference between the two mRNA splices was not significant in the matched tissues. , the ratios of light intensities of p33ING1b and p47ING1a mRNA expression in the cancerous tissues of Dukes’ stages C and D were significantly lower only those 4 cases of LOH (11.4%) were found. CONCLUSION: p33ING1b and p47ING1a mRNA expressions are closely related with the carcinogenesis and progression of human sporadic colorectal cancer. No mutation of ING1 gene is found, and there are only few LOH in sporadic coiorectal cancers. These might not be the main reasons for the down regulation of ING1 expression. Its low expression may happen in transcription or post-transcription.