Abstract: Thirty-one pairs of FTIR spectra of samples, including gastric and colorectal cancer and the corresponding normal tissues, were collected after surgery. FTIR spectra of cancerous tissue were significantly different from those of normal tissues. (1) Alterations of bands related to lipid: 2955, 2920, 2870, 2850 and 1740 cm^-1 appeared less frequently in malignant tissue(P<0.001). The ratio of I₁₄₆₀/I₁₄₀₀ in malignant tissue decreased significantly(P<0.001), indicating that the relative quantity of lipid in malignant tissue decreased significantly. (2) Alterations of bands related to protein: in malignant tissue, the band of N—H and O—H shifted to a lower wave number(P=0.025), suggesting that the degree of hydrogen-bonding of N—H and O—H increased. In malignant tissue, the ratios of I₃₃₇₅/I₁₄₆₀, I₁₆₄₀/I₁₄₆₀, I₁₅₅₀/I₁₄₆₀ raised(P<0.01), respectively. These changes illustrate that the relative quantity of protein to lipid in malignant tissue increased significantly. The ratio of HW₁₅₅₀/I₁₅₅₀ increased obviously(P=0.036), while HW₁₅₅₀ decreased significantly(P=0.05), compared with those of normal tissue. We can conclude that the secondary structure of protein in malignant tissue changed. (3) Alterations of bands related to carbohydrate: in malignant tissue, the ratio of I₁₁₆₀/I₁₄₆₀ reduced(P=0.002). It might be due to the lessen of glycoprotein on the surface of malignant tissue, reversely, the ratio of I₁₁₂₀/I₁₄₆₀ raised(P= 0.019). The possible reason was that the glucogen grains on the surface of the malignant tissue increased. (4) Alterations of band related to nucleic acid: in normal tissue, the peak of PO antisymmetric vibration was at (1241.61±6.15) cm^-1. In malignant tissue, the band shifted toward a higher wave number(P=0.033) due to the decreased hydrogen-bonding of PO. FTIR spectroscopy could be a powerful tool for cancer diagnosis.

Key words: Gastric cancer, Colorectal cancer, FTIR