OBJECTIVE To investigate whether platelet-activating factor acetylhydrolase IB3(PAFAH1B3) promotes vemurafenib resistance in BRAF^V600E papillary thyroid carcinoma(PTC) cells by regulating the AMP-activated protein kinase(AMPK)-acetyl-CoA carboxylase(ACC) pathway and enhancing lipid metabolism.

METHODS RT-PCR was used to detect the mRNA expression levels of PAFAH1B3 in cells. The protein expression levels of PAFAH1B3, Bcl-2, Bax, pAMPK, AMPK, ACC2 and pACC in cells were measured using Western blotting. Lipid accumulation in cells was assessed using Oil Red O staining, while cell apoptosis was evaluated through flow cytometry. A drug-resistant cell line was established, and the effects of PAFAH1B3 on lipid metabolism were examined through overexpression or knockdown experiments.

RESULTS PAFAH1B3 expression was higher in BRAF^V600E cells than BRAF^wt cells(P<0.05 or P<0.001), and was significantly upregulated in BRAF^V600E vemurafenib-resistant cells compared with non-resistant cells(P<0.001). Upregulation of PAFAH1B3 enhanced the resistance of cells to vemurafenib and reduced the apoptosis rate(P<0.05). OE-PAFAH1B3 decreased AMPK phosphorylation, thereby downregulating ACC2 phosphorylation levels, which significantly reduced fatty acid oxidation levels and increased lipid accumulation in BRAF^V600E cells. sh-PAFAH1B3 enhanced the vemurafenib sensitivity of BRAF^V600E cells, and this effect was reversed by sh-ACC2.

CONCLUSION PAFAH1B3 enhances the resistance of BRAF^V600E PTC cells to vemurafenib by reducing the phosphorylation levels of AMPK and ACC, thereby inhibiting fatty acid oxidation and promoting lipid accumulation.