Department of Medicinal Chemistry, Medical University of Bialystok, Mickiewicza 2 D, 15-222 Bialystok, Poland.
Laboratory of Cosmetology, Medical University of Bialystok, Akademicka 3, 15-267 Bialystok, Poland.
Biomed Pharmacother. 2017 Nov;95:429-436. doi: 10.1016/j.biopha.2017.08.104. Epub 2017 Sep 12.
Since betulin (Bet) and its acetylenic derivative, 28-O-propynoylbetulin (proBet) were shown to induce apoptosis in several cancer cell lines, we studied the mechanism of this process in human endometrial adenocarcinoma cells (EA). Previous studies suggested that this group of compounds affect prolidase activity (proline releasing enzyme from imidodipeptides) and collagen biosynthesis (proline utilizing process) providing substrate (proline) for proline oxidase (POX) dependent apoptosis. Here we provide evidence that Bet and proBet exhibit prolidase-inducing activity in EA cell line. However, in contrast to Bet, proBet inhibited collagen biosynthesis, increased intracellular proline concentration and induced apoptosis in EA cells, as detected by caspase-3, and -9 expressions and annexin V staining. Although POX expression was not affected by both compounds, the process of apoptosis was accompanied by increase in cytoplasmic level of proline. The mechanism for proBet-induced prolidase activity was found at the level of β1 integrin signaling. The inhibition of collagen biosynthesis was due to up-regulation of NF-κB p65, an inhibitor of collagen type I gene transcription. Although Bet and proBet induced expression of pro-apoptotic p53 in EA cells, the effect of proBet on the processes was much stronger. In contrast to proBet, Bet strongly induced expression of pro-survival factors, HIF-1α and VEGF. The data suggest that massive production of proline by proBet-dependent activation of prolidase and inhibition of proline utilization for collagen biosynthesis may represent mechanism for POX-dependent apoptosis in EA cells.
由于白桦脂醇（Bet）及其炔基衍生物 28-O-丙炔酰基白桦脂醇（proBet）已被证明可诱导几种癌细胞系凋亡，我们研究了其在人子宫内膜腺癌细胞（EA）中的作用机制。先前的研究表明，这组化合物影响脯氨酰肽酶（从二肽释放脯氨酸的酶）和胶原生物合成（脯氨酸利用过程），为脯氨酸氧化酶（POX）依赖性凋亡提供底物（脯氨酸）。在这里，我们提供了证据表明 Bet 和 proBet 在 EA 细胞系中表现出脯氨酰肽酶诱导活性。然而，与 Bet 相反，proBet 抑制胶原生物合成，增加细胞内脯氨酸浓度，并通过 caspase-3 和 -9 表达和 Annexin V 染色诱导 EA 细胞凋亡。虽然两种化合物均未影响 POX 表达，但凋亡过程伴随着细胞质中脯氨酸水平的增加。proBet 诱导的脯氨酰肽酶活性的机制被发现在β1 整合素信号转导水平。胶原生物合成的抑制是由于 NF-κB p65 的上调，NF-κB p65 是胶原 I 基因转录的抑制剂。尽管 Bet 和 proBet 诱导 EA 细胞中促凋亡 p53 的表达，但 proBet 的作用要强得多。与 proBet 相反，Bet 强烈诱导促生存因子 HIF-1α 和 VEGF 的表达。数据表明，proBet 依赖性脯氨酰肽酶的激活和脯氨酸利用抑制胶原生物合成大量产生脯氨酸可能代表 POX 依赖性 EA 细胞凋亡的机制。
