ODP276 THYROID CANCER CELLS ARE MORE RESISTANT THAN NORMAL CELLS TO BISPHENOL-A CYTOTOXIC EFFECT

Bisphenol-A (BPA) is a well-known endocrine disruptor that produces important effects on thyroid metabolism, can interfere with TSH transcriptional activity, alter the transcription of T3-associated genes and, thus, modulate its activity in different cell lines. However, its direct effects on thyroid cells, especially on mutated thyroid cells, are still poorly understood. We tested 14 different concentrations of BPA, ranging from 0.4µg/mL to 400µg/mL, including LME (Specific Migration Limit =1μg/mL, recommended as acceptable by the Brazilian National Health Surveillance Agency-ANVISA) on two human thyroid cell lines: Nthy-ori 3-1 (from normal thyroid follicular cells) and TPC-1 (from papillary carcinoma). Cell viability analysis was made using the Trypan blue assay on cells exposed to BPA for 24h and 48h in technical and biological triplicate. We observed a non-monotone dose-response curve, characteristic of disruptors’ effect, on both cell lines, with greater cytotoxic effect with higher doses. In fact,100μg/mL already killed almost all Nthy-ori 3-1 cells (99% at 24h and 97% at 48h), whereasthe doses of 0.78µg/mL; 4µg/mL and 12.5µg/mL caused 50% kill. Optical microscopy revealed some irregular cells lost on the plate, and few debris with50μg/mL. Concentrations of 100 to 400µg/mL produced many dark small cells detached from the plate and clumps of dead cells. The SCI dose (1µg/mL - allowed in daily life), resulted in 79% of Nthy-ori 3-1 cell death after 24h of exposure. However, only 7% of the cell were dead after 48h of exposure to the SCI dose. This reduction in death rate after longer exposure to BPA was observed at all concentrations, suggesting a potent cellular recovery mechanism. The TPC-1 strain showed a different behavior, with a much more linear dose-dependent cytotoxic effect and much more resistance to the harmful effects of BPA at low doses. In fact, 0.4μg/mL to 3.125μg/mL produced less than 10% cell death, and microscopy confirmed the maintenance of the integrity of virtually all cells. On the contrary, BPA concentrations from 100 to 400µg/mL killed almost all TPC-1 cells at both 24h and 48h times. We conclude that this thyroid papillary carcinoma cell line is more resistant than the normal thyroid lineage to low BPA concentrations (from 0.4 to 50µg/mL) but this endocrine disruptor is highly cytotoxic at higher concentrations, causing more than 90% cell deaths on both normal and mutated thyroid cell lines. Presentation: No date and time listed