RESUMO
Toll-like receptors (TLRs) expressed on immune cells trigger inflammatory responses. TLRs are also expressed on ovarian cancer (OvCa) cells, but the consequences of signaling by the TLR4/MyD88 pathway in these cells are unclear. Here, TLR4 and MyD88 expression in OvCa tissues (n=20) and cell lines (OVCAR3, SKOV3, AD10, A2780 and CP70) was evaluated by reverse transcriptase-PCR, western blots and immunohistochemistry. Cell growth, apoptosis, nuclear factor-kappaB (NF-kappaB) translocation, IRAK4 and TRIF expression and cJun phosphorylation were measured following tumor cell exposure to the TLR4 ligands, lipopolysaccharide (LPS) or paclitaxel (PTX). Culture supernatants were tested for cytokine levels. TLR4 was expressed in all tumors, tumor cell lines and normal epithelium. MyD88 was detectable in tumor tissues and in 3/5 OvCa lines but not in normal cells. In MyD88(+) SCOV3 cells, LPS or PTX binding to TLR4 induced IRAK4 activation and cJun phosphorylation, activated the NF-kappaB pathway and promoted interleukin (IL)-8, IL-6, vascular endothelial growth factor and monocyte chemotactic protein-1 production and resistance to drug-induced apoptosis. Silencing of TLR4 in SCOV3 cells with small interference RNA resulted in phosphorylated-cJun (p-cJun) downregulation and a loss of PTX resistance. In PTX-sensitive, MyD88(neg) A2780 cells, TLR4 stimulation upregulated TRIF, and TLR4 silencing eliminated this effect. Thus, TLR4/MyD88 signaling supports OvCa progression and chemoresistance, promoting immune escape.
Assuntos
Carcinoma/patologia , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Lipopolissacarídeos/farmacologia , Neoplasias Ovarianas/patologia , Paclitaxel/farmacologia , Receptor 4 Toll-Like/fisiologia , Carcinoma/genética , Carcinoma/metabolismo , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Citocinas/metabolismo , Resistencia a Medicamentos Antineoplásicos/genética , Feminino , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Fator 88 de Diferenciação Mieloide/genética , Fator 88 de Diferenciação Mieloide/fisiologia , NF-kappa B/metabolismo , NF-kappa B/fisiologia , Neoplasias Ovarianas/genética , Neoplasias Ovarianas/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Receptor 4 Toll-Like/genética , Receptor 4 Toll-Like/metabolismo , Células Tumorais Cultivadas , Evasão Tumoral/efeitos dos fármacos , Evasão Tumoral/genética , Regulação para Cima/efeitos dos fármacosRESUMO
IRX-2 is a cytokine-based biologic agent that has the potential to enhance antitumor immune responses. We investigated whether IRX-2 can protect T cells from tumor-induced apoptosis. Tumor-derived microvesicles (MV) expressing FasL were purified from supernatants of tumor cells and incubated with activated CD8(+) T cells. MV induced significant CD8(+) T-cell apoptosis, as evidenced by Annexin binding (64.4+/-6.4%), caspase activation (58.1+/-7.6%), a loss of mitochondrial membrane potential (82.9+/-3.9%) and DNA fragmentation. T-cell pretreatment with IRX-2 prevented apoptosis. IRX-2-mediated cytoprotection was dose and time dependent and was comparable to effects of IL-2, IL-7 or IL-15. IRX-2 prevented MV-induced downregulation of JAK3 and TCRzeta chain and induced STAT5 activation in T cells. IRX-2 prevented MV-induced Bax and Bim upregulation (P<0.005-0.05), prevented cytochrome c release and Bid cleavage, and concurrently restored the expression of Bcl-2, Bcl-xL, FLIP and Mcl-1 (P<0.005-0.01) in T cells. In addition, IRX-2 reversed MV-induced inhibition of the PI3K/Akt pathway. An Akt inhibitor (Akti-1/2) abrogated protective effects of IRX-2, suggesting that Akt is a downstream target of IRX-2 signaling. Thus, ex vivo pretreatment of CD8(+) T cells with IRX-2 provided potent protection from tumor-induced apoptosis. IRX-2 application to future cancer biotherapies could improve their effectiveness by bolstering T-cell resistance to tumor-induced immunosuppression.