Suppression of HSP70 expression sensitizes NSCLC cell lines to TRAIL-induced apoptosis by upregulating DR4 and DR5 and downregulating c-FLIP-L expressions

Abstract

Many cancer cell types are resistant to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. Here, we examined whether HSP70 suppression by small interfering RNA (siRNA) sensitized non-small cell lung cancer (NSCLC) cells to TRAIL-induced apoptosis and the underlying mechanisms. We demonstrated that HSP70 suppression by siRNA sensitized NSCLC cells to TRAIL-induced apoptosis by upregulating the expressions of death receptor 4 (DR4) and death receptor 5 (DR5) through activating NF-κB, JNK, and, subsequently, p53, consequently significantly amplifying TRAIL-mediated caspase-8 processing and activity, cytosolic translocation of cytochrome c, and cell death. Consistently, the pro-apoptotic proteins Bad and Bax were upregulated, while the anti-apoptotic protein Bcl-2 was downregulated. The luciferase activity of the DR4 promoter was blocked by a NF-κB pathway inhibitor BAY11-7082, suggesting that NF-κB activation plays an important role in the transcriptional upregulation of DR4. Additionally, HSP70 suppression inhibited the phosphorylation of ERK, AKT, and PKC, thereby downregulating c-FLIP-L. A549 xenografts in mice receiving HSP70 siRNA showed TRAIL-induced cell death and increased DR4/DR5 levels and reduced tumor growth. The combination of psiHSP70 gene therapy with TRAIL also significantly increased the survival benefits induced by TRAIL therapy alone. Interestingly, HSP27 siRNA and TRAIL together could not suppress tumor growth or prolong the survival of tumor-bearing mice significantly, although the combination could efficiently induce the apoptosis of A549 cells in vitro. Our findings suggest that HSP70 suppression or downregulation might be promising to overcome TRAIL resistance in cancer.

Targeting HSP70 and GRP78 in canine osteosarcoma cells in combination with doxorubicin chemotherapy

“…HSPs, such as those from the 70 kDa family, are known to complete protein translocation, maturation, folding, and degradation duties within the cell under both stressed and non-stressed states (Feder and Hofmann 1999). Acting in this fashion, HSP70s intervene in the apoptotic cascade and prevent protein aggregation, ultimately hindering apoptosis by an ATP-dependent mechanism (Beere et al 2000;Elmore 2007;Gabai et al 2002;Gotoh et al 2004;Gurbuxani et al 2003;Li et al 2010;Ruchalski et al 2003;Zhuang et al 2013).…”

Triptolide reduces the viability of osteosarcoma cells by reducing MKP-1 and Hsp70 expression

“…Under non-stress conditions, Hsp70 has multiple functions, including protein folding and translocation of newly synthesized proteins, and serving as a signaling molecule (26). In colon and lung cancers, Hsp70 expression is correlated with metastasis and poor prognosis (27,28). Since Hsp70 is crucially involved in multiple steps of cancer developments (29), the present study investigated the potential of triptolide to be used as a treatment for osteosarcoma, possibly via a mechanism associated with the regulation of MKP-1 and Hsp70.…”

N-Acetyl-Glucosamine Sensitizes Non-Small Cell Lung Cancer Cells to TRAIL-Induced Apoptosis by Activating Death Receptor 5

“…Upon TRAIL activation, DRs on the targeted cell surfaces cluster, and DISC is assembled at the inner surface of the plasma membrane [39]. Only clustered receptors on the cell surface can promote DISC formation and initiate apoptosis [41-43]. TRAIL-resistant cells have defective stimulation of caspase-8 processing and exhibit weaker receptor-mediated DISC formation and caspase-8 recruitment [35].…”