Al-Awadi Farida, Yang Meng, Tan Yuying, Han Qinghong, Li Shukuan, Hoffman Robert M
Faculty of Medicine, Kuwait University, Kuwait.
Anticancer Res. 2008 Sep-Oct;28(5A):2541-4.
The methionine cycle and its metabolites homocysteine and cysteine serve several important functions in cellular metabolism. Abnormalities in metabolism of the methionine cycle have been associated with cancer. We determined plasma levels of methionine, homocysteine and cysteine in nude mice implanted with human cancer cell lines (MDA-MB-435 breast, PC-3 prostate, HT29 colon, BX-PC3 pancreas) over a prolonged period of tumor growth. The data were compared with correspondins values in nontumor-bearing controls. Nude mice were injected s.c. in the right flank with 10(6) cancer cells. Tumor growth was measured over time. Methionine was measured in plasma by HPLC. Cysteine and homocysteine were measured in plasma by recombinant enzyme assays and spectrophotometry to measure products. The concentrations of cysteine and homocysteine in plasma decreased significantly as a result of progression of breast, prostate and the pancreas tumor types implanted in the nude mice at least over a two-month period. Data for the colon tumors were nonsignificant for both cysteine and homocysteine. In the case of methionine, the decrease was significant only due to progression of the breast tumors, grown over a long time period, as compared to the mice without tumors control. The results suggest that sulphur amino acids may be plasma or serum biomarkers for cancer progression.
甲硫氨酸循环及其代谢产物同型半胱氨酸和半胱氨酸在细胞代谢中发挥着多种重要功能。甲硫氨酸循环代谢异常与癌症有关。我们测定了长时间植入人癌细胞系（MDA - MB - 435乳腺癌、PC - 3前列腺癌、HT29结肠癌、BX - PC3胰腺癌）的裸鼠血浆中甲硫氨酸、同型半胱氨酸和半胱氨酸的水平。将这些数据与无肿瘤对照的相应值进行比较。给裸鼠右腹侧皮下注射10⁶个癌细胞。随时间测量肿瘤生长情况。通过高效液相色谱法测定血浆中的甲硫氨酸。通过重组酶测定法和分光光度法测量产物来测定血浆中的半胱氨酸和同型半胱氨酸。至少在两个月的时间里，裸鼠体内植入的乳腺癌、前列腺癌和胰腺癌肿瘤类型进展导致血浆中半胱氨酸和同型半胱氨酸的浓度显著降低。结肠癌肿瘤的半胱氨酸和同型半胱氨酸数据无显著意义。就甲硫氨酸而言，与无肿瘤的对照小鼠相比，仅长时间生长的乳腺癌进展导致其降低显著。结果表明，含硫氨基酸可能是癌症进展的血浆或血清生物标志物。
