Evaluation of the Carcinogenic Possibility of Butachlor

• Main Authors: Yue-Lun He, 何岳倫
• Other Authors: Yueh-Hsing Ou
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/64291371919226745604

碩士 === 國立陽明大學 === 醫學生物技術暨檢驗學系暨研究所 === 99 === Butachlor is a herbicide that has been widely used in rice fields of Southeast Asia and Taiwan. Previous research has shown butachlor could be a carcinogen, but the detailed mechanism is still unclear. Another herbicide, alachlor, is known to cause rat nasopharyngeal carcinoma and thyroid cancer, and has been demonstrated to be an endocrine disrupting chemical (EDC) belonging to an estrogen family. Butachlor and alachlor are very similar in their chemical structure and properties. Therefore, we hypothesized that butachlor might be a carcinogen and EDC. From the cell proliferation assay, we found that 20μM butachlor could effectively enhance proliferation of both MCF-7 and BNL CL2 cell lines. The cell proliferation became less obvious due to the counter cytotoxic effect of the butachlor if the concentration is higher. To further understand the mechanism of butachlor induced cell proliferation, we examined AP-1 transcription factor regulated pathway. AP-1 is composed of two proto-oncogenes: c-jun and c-fos. Butachlor was used to treat two cell lines, MCF-7 and BNL CL2, for 30 to 120 minutes; there was no significant change in c-jun or c-fos RNA level. If the treatment is lengthened to 36 and 48 hours, still, c-jun RNA level in both MCF-7 and BNL CL2 cell lines showed no difference; however, the level of c-fos RNA was slightly lower in BNL CL2. Therefore, butachlor might not act through AP-1/MAPK pathway to induce cell proliferation. In addition, we would also like to determine if butachlor could induce cell transformation. By performing soft agar assay, we discovered that butachlor alone or with MNNG could not induce BNL CL2 cell line transformation. A possible reason could be the weak carcinogenic ability of butachlor. Lastly, we performed luciferase reporter assay to figure out if butachlor indeed is an EDC. Our results showed that 40 and 60μM of butachlor could induce luciferase expression in MCF-7. As for BNL CL2, whether E2 or butachlor was used, luciferase expression was not significant. A possible explanation could be that the expression of ERα is low, the affinity between the ligand and its receptor was not strong enough, or that between the ligand-receptor complex and estrogen response element (ERE). From MCF-7 experiment, we demonstrated that butachlor could possibly be an estrogen-related EDC. More studies need to be done in the future to confirm the EDC and carcinogenic abilities of butachlor.