Lithocholic acid induces endoplasmic reticulum stress, autophagy and mitochondrial dysfunction in human prostate cancer cells

Abstract

Lithocholic acid (LCA) is a secondary bile acid that is selectively toxic to human neuroblastoma, breast and prostate cancer cells, whilst sparing normal cells. We previously reported that LCA inhibited cell viability and proliferation and induced apoptosis and necrosis of androgen-dependent LNCaP and androgen-independent PC-3 human prostate cancer cells. In the present study, we investigated the roles of endoplasmic reticulum (ER) stress, autophagy and mitochondrial dysfunction in the toxicity of LCA in PC-3 and autophagy deficient, androgen-independent DU-145 cells. LCA induced ER stress-related proteins, such as CCAAT-enhancer-binding protein homologous protein (CHOP), and the phosphorylation of eukaryotic initiation factor 2-alpha (p-eIF2α) and c-Jun N-terminal kinases (p-JNK) in both cancer cell-types. The p53 upregulated modulator of apoptosis (PUMA) and B cell lymphoma-like protein 11 (BIM) levels were decreased at overtly toxic LCA concentrations, although PUMA levels increased at lower LCA concentrations in both cell lines. LCA induced autophagy-related conversion of microtubule-associated proteins 1A/1B light chain 3B (LC3BI–LC3BII), and autophagy-related protein ATG5 in PC-3 cells, but not in autophagy-deficient DU-145 cells. LCA (>10 µM) increased levels of reactive oxygen species (ROS) concentration-dependently in PC-3 cells, whereas ROS levels were not affected in DU-145 cells. Salubrinal, an inhibitor of eIF2α dephosphorylation and ER stress, reduced LCA-induced CHOP levels slightly in PC-3, but not DU-145 cells. Salubrinal pre-treatment increased the cytotoxicity of LCA in PC-3 and DU-145 cells and resulted in a statistically significant loss of cell viability at normally non-toxic concentrations of LCA. The late-stage autophagy inhibitor bafilomycin A1 exacerbated LCA toxicity at subtoxic LCA concentrations in PC-3 cells. The antioxidant α-tocotrienol strongly inhibited the toxicity of LCA in PC-3 cells, but not in DU-145 cells. Collectively, although LCA induces autophagy and ER stress in PC-3 cells, these processes appear to be initially of protective nature and subsequently consequential to, but not critical for the ROS-mediated mitochondrial dysfunction and cytotoxicity of LCA. The full mechanism of LCA-induced mitochondrial dysfunction and cytotoxicity in the similarly sensitive DU-145 cells remains to be elucidated.

Whole-Transcriptome Analysis of CD133+CD144+ Cancer Stem Cells Derived from Human Laryngeal Squamous Cell Carcinoma Cells

“…Previous studies have suggested the endoplasmic reticulum stress could determine apoptosis and cell death in cancers [37,38]. SSR1, regulated by miR-4521, was associated with the pathway of protein processing.…”

Indoxylsulfate, a Metabolite of the Microbiome, Has Cytostatic Effects in Breast Cancer via Activation of AHR and PXR Receptors and Induction of Oxidative Stress

“…In this study, we identified a novel bacterial metabolite, IS, that possesses cytostatic features in breast cancer, similar to the short-chain fatty acids [ 61 , 62 ], lithocholic acid [ 16 , 45 , 50 , 78 , 79 , 80 , 81 ], cadaverine [ 17 , 51 ], and indole propionic acid [ 40 ]. Despite the conflicting results, the majority of breast cancer microbiome studies show suppressed diversity and biosynthetic capacity in breast cancer-associated oncobiosis [ 1 , 2 , 3 , 4 , 5 , 8 , 9 , 12 , 13 , 14 , 15 , 48 ], leading to limited biosynthetic capacity that lowers the level of protective bacterial metabolites in patients [ 16 , 52 ].…”

“…IS administration reduces cell proliferation, infiltration into the surrounding tissues, and metastasis formation in cellular and animal models. This feature is a common trait for other cytostatic metabolites in breast cancer [ 16 , 17 , 40 , 45 , 50 , 51 , 61 , 62 , 78 , 79 , 80 , 81 ]. At the same time, IS did not affect non-transformed cells, again a common trait for bacterial cytostatic metabolites in breast cancer [ 16 , 17 , 40 , 78 ], suggesting that these metabolites have tumor cell-specific effects.…”

Astrocyte elevated gene 1 (AEG‐1) promotes anoikis resistance and metastasis by inducing autophagy in hepatocellular carcinoma

“…Accordingly, autophagy and anoikis resistance induced by AEG‐1 were inhibited by siRNA against ATF4. Studies have shown that ER stress is strongly associated with autophagy in cancers (Cerezo & Rocchi, ; Gafar et al, ; Williams, Hou, Ni, & Ding, ). However, to our knowledge, it has not been reported before that ER stress may play a role in protective autophagy induced by AEG‐1.…”