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Background/Aim: Low-molecular weight heparins (LMWHs) may possess putative antitumoral properties; however, the underlying mechanism(s) remains elusive. We evaluated the antiproliferative and antimigratory effects of enoxaparin (a LMWH) in lung adenocarcinoma A549 cells, and assessed the possible mechanism involved, and the effect on doxorubicin's efficacy. Materials and Methods: Proliferation and migration were evaluated using BrdU and transwell assays, respectively. Immunoblotting was used to measure PAR-1, PAR-2, MMP-2, ERK1/2 and Akt proteins. Apoptosis and cell cycle studies examined the combined effect of enoxaparin and doxorubicin. Results: Enoxaparin inhibited A549 cell proliferation and migration. Following PAR-1 gene knock down, enoxaparin's effect on A549 cell proliferation was diminished compared to scrambled siRNA. Our experiments verified that enoxaparin-mediated down-regulation of MAPK and PI3K, reduced MMP-2 expression and inhibited A549 cell migration. Additionally, enoxaparin increased doxorubicin's efficacy by enhancing apoptosis, while no effect on cell-cycle progression was observed. Conclusion: Results suggest that the anticancer activity of enoxaparin in A549 cells was mediated by the interference of two major PAR-1 downstream signaling pathways, MAPK/ERK and PI3K/Akt, which in turn inhibit proliferation and migration. Therefore, enoxaparin may be promising as an adjunct to traditional chemotherapy for lung cancer and warrants further investigation.

The folate and cobalamin (Cbl-) dependent enzyme methionine synthase (MS) is highly sensitive to oxidation and its activity affects all methylation reactions. Recent studies have revealed alternative splicing of MS mRNA in human brain and patient-derived fibroblasts. Here we show that MS mRNA in SH-SY5Y human neuroblastoma cells is alternatively spliced, resulting in three primary protein species, thus providing a useful model to examine cofactor dependence of these variant enzymes. MS activity was dependent upon methylcobalamin (MeCbl) or the combination of hydroxocobalamin (OHCbl) and S-adenosylmethionine (SAM). OHCbl-based activity was eliminated by depletion of the antioxidant glutathione (GSH) but could be rescued by provision of either glutathionylcobalamin (GSCbl) or MeCbl. Pretreatment of cells with lead, arsenic, aluminum, mercury, or the ethylmercury-containing preservative thimerosal lowered GSH levels and inhibited MS activity in association with decreased uptake of cysteine, which is rate-limiting for GSH synthesis. Thimerosal treatment decreased cellular levels of GSCbl and MeCbl. These findings indicate that the alternatively spliced form of MS expressed in SH-SY5Y human neuronal cells is sensitive to inhibition by thimerosal and neurotoxic metals, and lower GSH levels contribute to their inhibitory action.