Proteomics Laboratory, Indian Institute of Toxicology Research/Council for Scientific & Industrial Research, Lucknow, India.
Biofactors. 2010 Nov-Dec;36(6):474-82. doi: 10.1002/biof.121. Epub 2010 Sep 16.
Bromelain, from pineapple, possesses potent anticancer effects. We investigated autophagic phenomenon in mammary carcinoma cells (estrogen receptor positive and negative) under bromelain treatment and also illustrated the relationship between autophagy and apoptosis in MCF-7 cells. MCF-7 cells exposed to bromelain showed delayed growth inhibitory response and induction of autophagy, identified by monodansylcadaverine localization. It was succeeded by apoptotic cell death, evident by sub-G1 cell fraction and apoptotic features like chromatin condensation and nuclear cleavage. 3-Methyladenine (MA, autophagy inhibitor) pretreatment reduced the bromelain-induced autophagic level, also leading to decline in apoptotic population, indicating that here autophagy facilitates apoptosis. However, addition of caspase-9 inhibitor Z-LEHD-FMK augmented the autophagy levels, inhibited morphological apoptosis but did not prevent cell death. Next, we found that bromelain downregulated the phosphorylation of extracellular signal-regulated kinase ½ (ERK½), whereas that of c-jun N-terminal kinase (JNK) and p38 kinase were upregulated. Also, MA had no influence on bromelain-suppressed ERK½ activation, yet, it downregulated JNK and p38 activation. Also, addition of mitogen-activated protein kinase (MAPK) inhibitors enhanced the autophagic ratios, which suggested the role of MAP kinases in bromelain-induced autophagy. All three MAPKs were seen to be constantly activated over the time. Bromelain was seen to induce the expressions of autophagy-related proteins, light chain 3 protein B II (LC3BII), and beclin-1. Using ERK½ inhibitor, expressions of LC3BII and beclin-1 increased, whereas p38 and JNK inhibitors decreased this protein expression, indicating that bromelain-induced autophagy was positively regulated by p38 and JNK but negatively regulated by ERK½. Autophagy-inducing property of bromelain can be further exploited in breast cancer therapy.
菠萝蛋白酶源自菠萝，具有很强的抗癌作用。我们研究了菠萝蛋白酶处理下乳腺癌细胞（雌激素受体阳性和阴性）中的自噬现象，并说明了 MCF-7 细胞中自噬与细胞凋亡之间的关系。暴露于菠萝蛋白酶的 MCF-7 细胞显示出生长抑制反应的延迟和自噬的诱导，这通过单丹磺酰尸胺定位来识别。继自噬之后，发生凋亡性细胞死亡，表现为亚 G1 细胞分数和染色质浓缩和核裂解等凋亡特征。3-甲基腺嘌呤（MA，自噬抑制剂）预处理降低了菠萝蛋白酶诱导的自噬水平，也导致凋亡群体的减少，表明此处自噬促进凋亡。然而，加入半胱天冬酶-9 抑制剂 Z-LEHD-FMK 增加了自噬水平，抑制了形态学凋亡，但不能防止细胞死亡。接下来，我们发现菠萝蛋白酶下调细胞外信号调节激酶 1/2（ERK1/2）的磷酸化，而 JNK 和 p38 激酶的磷酸化上调。此外，MA 对抑制 ERK1/2 激活的菠萝蛋白酶没有影响，但下调了 JNK 和 p38 的激活。此外，加入丝裂原活化蛋白激酶（MAPK）抑制剂增强了自噬比率，这表明 MAP 激酶在菠萝蛋白酶诱导的自噬中起作用。三种 MAPK 都被观察到在整个时间内持续激活。菠萝蛋白酶诱导自噬相关蛋白，即轻链 3 蛋白 B II（LC3BII）和 beclin-1 的表达。使用 ERK1/2 抑制剂，LC3BII 和 beclin-1 的表达增加，而 p38 和 JNK 抑制剂则降低了该蛋白的表达，表明菠萝蛋白酶诱导的自噬是由 p38 和 JNK 正向调节，而由 ERK1/2 负向调节。菠萝蛋白酶的自噬诱导特性可进一步用于乳腺癌治疗。
