[Myrislignan Induces Apoptosis in Gastric Cancer Cell Line Through PI3K/AKT Signaling Pathway].

Objective: To investigate the effect of myrislignan (MYR) on the apoptosis of gastric cancer cell line and its relationship with phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway. Methods: The gastric cells (SGC-7901) were treated with MYR at different concentrations, i.e., 0, 25, 50, 100, and 200 µmol/L, for 48 h and 72 h and the effect of MYR on the proliferation of SGC-7901 cells was measured by CCK-8 assay. Then, SGC-7901 cells were treated with different concentrations of MYR at 50, 100, and 200 µmol/L for 48 h. Meanwhile, a normal control group and a dimethyl sulfoxide (DMSO) solvent control group (0.1% DMSO) were established. Flow cytometry was used to determine the apoptosis rate of SGC-7901 cells. The protein expression levels of PI3K, AKT, Bcl-2-associated X protein (BAX), cysteine-dependent aspartate-specifc protease-3 (Caspase-3), and Caspase-9 were determined by Western blot. Then, PI3K activator (20 µmol/mL) was used to treat SGC-7901 cells for 48 h in 4 groups, the control group, 0.1% DMSO group, MYR group, and MYR+PI3K activator group, and the effect on MYR's induction of apoptosis and regulation of the protein expression levels of PI3K, AKT, BAX, Caspase-3, and Caspase-9 in SGC-7901 cells. Results: Compared with the control group, MYR at 50, 100 and 200 µmol/L inhibited the proliferation of gastric cancer cells, increased the apoptosis rate, down-regulated the protein expression levels of PI3K and AKT, and up-regulated the protein expression levels of BAX, Caspase-3, and Caspase-9 in a dose-dependent manner ( P<0.05). However, PI3K activator attenuated MYR-induced apoptosis in gastric cancer cells and MYR's regulation of PI3K, AKT, BAX, Caspase-3, and Caspase-9 protein expression ( P<0.05). Conclusion: MYR induces the expression of BAX, Caspase-3, and Caspase-9 proteins by inhibiting the PI3K/AKT signaling pathway, thereby promoting the apoptosis of gastric cancer cells.

GCH1 plays a role in the high-altitude adaptation of Tibetans.

Tibetans are well adapted to high-altitude hypoxia. Previous genome-wide scans have reported many candidate genes for this adaptation, but only a few have been studied. Here we report on a hypoxia gene ( GCH1, GTP-cyclohydrolase I), involved in maintaining nitric oxide synthetase (NOS) function and normal blood pressure, that harbors many potentially adaptive variants in Tibetans. We resequenced an 80.8 kb fragment covering the entire gene region of GCH1 in 50 unrelated Tibetans. Combined with previously published data, we demonstrated many GCH1 variants showing deep divergence between highlander Tibetans and lowlander Han Chinese. Neutrality tests confirmed a signal of positive Darwinian selection on GCH1 in Tibetans. Moreover, association analysis indicated that the Tibetan version of GCH1 was significantly associated with multiple physiological traits in Tibetans, including blood nitric oxide concentration, blood oxygen saturation, and hemoglobin concentration. Taken together, we propose that GCH1 plays a role in the genetic adaptation of Tibetans to high altitude hypoxia.

EP300 contributes to high-altitude adaptation in Tibetans by regulating nitric oxide production.

The genetic adaptation of Tibetans to high altitude hypoxia likely involves a group of genes in the hypoxic pathway, as suggested by earlier studies. To test the adaptive role of the previously reported candidate gene EP300 (histone acetyltransferase p300), we conducted resequencing of a 108.9 kb gene region of EP300 in 80 unrelated Tibetans. The allele-frequency and haplotype-based neutrality tests detected signals of positive Darwinian selection on EP300 in Tibetans, with a group of variants showing allelic divergence between Tibetans and lowland reference populations, including Han Chinese, Europeans, and Africans. Functional prediction suggested the involvement of multiple EP300 variants in gene expression regulation. More importantly, genetic association tests in 226 Tibetans indicated significant correlation of the adaptive EP300 variants with blood nitric oxide (NO) concentration. Collectively, we propose that EP300 harbors adaptive variants in Tibetans, which might contribute to high-altitude adaptation through regulating NO production.