Additonally, the pChk2 and H2AX levels also showed increase in their levels upon combination treatment (Fig. resulted downregulation of MICA, and reduced V2V2 T cells-mediated cytotoxicity. Alternately, stimulating ATM pathway enhanced expression of MICA, and sensitized ovarian cancer cells for cytotoxic lysis by V2V2 T cells. We further show that combining Isradipine currently approved chemotherapeutic drugs, which induced ATM signal transduction, along with V2V2 T cells enhanced cytotoxicity of resistant ovarian cancer cells. These findings indicate that ATM/ATR pathway plays an important role in tumor recognition, and drugs promoting ATM signaling pathway might be considered as a combination therapy together with V2V2 T cells for effectively treating resistant ovarian cancer cells. Isradipine and reinjected into the patients with tumors [14, 15]. Adoptive T-cell therapy in renal cancer patients showed no adverse events, and 3 of 5 patients showed slower tumor progression. Patients documented positive response showed an increased number of V2V2 T cells in the peripheral blood and a strong response to phosphoantigen stimulation [14]. Various trials show promise for development of autologous V2V2 T cell therapies in eligible patients. However, for ovarian cancer, there is currently no effective immunotherapy. Interestingly, chemotherapeutic brokers were shown to induce immunogenic tumor cell death, which is crucial for tumor eradication and long-term protection against relapse. Moreover, V2V2 T cells were recruited to the tumor bed after immunogenic chemotherapy and appear to be contributors to the efficacy of chemotherapy [16]. So, developing a combination therapy using chemotherapeutic reagent and V2V2 T cells will be a valuable option to be tested. The V2V2 T cells induce cytotoxicity in many ovarian tumor cells via induction of apoptosis [17]. However, some of the ovarian tumor cells evade the apoptosis process and became resistant towards V2V2 T cells-mediated cytotoxicity. These resistant cell lines (such as A2780) showed slower proliferation compared to the sensitive cell line (such as OV4); interestingly, we found that the resistant cell line has reduced expression of MICA [17]. We proposed that this tumor cells may evade the V2V2 T cells cytotoxicity by down-regulating their MICA expression and at the same time enter into a dormancy stage, in which their proliferation were slowed down. In the current study, we further investigated the molecular mechanisms involved in the immune escape process. It has been shown that genotoxic stress or inhibitors of DNA-replication could up-regulate the expression of NKG2D ligand through activation of ATM (ataxia telangiectasia mutated) and ATR (ATM- and Rad3-related) protein kinase pathway in human fibroblast and in mouse tumor cell lines, which led to enhance cytotoxic lysis by NK cells [18, 19]. ATM and ATR are activated in response to DNA damage, oxidative stress, and replication stress resulting in apoptosis or cell cycle arrest. After activation ATM phosphorylates Chk2, and ATR phosphorylates Chk1 to start a cascade of downstream signaling events [20]. Activated Chk1 and Chk2 phosphorylate Cdc25 phosphatases, to inhibit their function, and the cells delay progression though Isradipine the cell cycle [20]. After activation ATR and ATM also phosphorylates H2A variant H2AX at Ser-139 (H2AX) at the damage sites, or where chromosomes are fragmented by oxidative stress [21]. The H2AX has been used as a marker for DNA damage, oxidative stress, and replication stress. It was also shown that inhibition of ATM pathway by using synthetic inhibitor such as KU-55933 suppressed cell proliferation and induced apoptosis [22]. In this study, we examined whether the ATM and ATR protein kinases play a role in V2V2 T cells-mediated recognition of ovarian cancer cells. We found that treatment of ovarian cancer cells with V2V2 T cells results in down regulation of ATR and ATM Rabbit Polyclonal to MUC13 signal transduction in resistant cells, but remain unchanged in sensitive cells. When we treated the cells with V2V2 T cells along with drugs activating ATM pathway, it resulted a significant increase in cytotoxicity of tumor cells. Thus, ATM-Chk2 signal transduction plays a critical role in regulating tumor survival in ovarian cancer upon.
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