Abdollahi Touraj, Robertson Noreen M, Abdollahi Abbas, Litwack Gerald
Department of Biochemistry and Molecular Pharmacology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Cancer Res. 2003 Aug 1;63(15):4521-6.
Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is known to trigger apoptosis in many malignant cells. Whereas cancer cells are responsive to TRAIL-induced cell death when used alone or in combination with other agents, normal cells are known to be relatively less sensitive to the ligand, making it a desirable therapeutic compound to target a variety of cancers. TRAIL induces apoptosis through its interaction with its two proapoptotic death receptors (DRs), DR4 and DR5. In addition, it may also bind the decoy receptors (DcRs), DcR1 and DcR2, which lack an intracellular signaling domain, thus negatively regulating TRAIL-induced apoptosis. Previously, it has been shown that interleukin (IL)-8 is elevated in the ascites of patients with ovarian cancer. Therefore, we examined the role that IL-8 may play in modulating sensitivity to TRAIL-mediated apoptosis. We treated the TRAIL-sensitive cell line OVCAR3 with TRAIL over a period of time with or without pretreatment with IL-8. Here we show the novel findings that IL-8 blocks TRAIL-induced cell death and was able to turn the TRAIL-sensitive cell line into a TRAIL-resistant one. We hypothesized that decreased expression of DRs DR4 and DR5 may contribute to TRAIL resistance. Both reverse transcription-PCR and flow cytometry revealed a decrease in DR4 expression after pretreatment of OVCAR3 cells with IL-8. We have also shown that TRAIL was able to induce caspase-8 cleavage in these cells, whereas pretreatment with IL-8 blocked this caspase cleavage. Through array analysis and confirmation with other techniques, we have determined that IL-8 regulates the expression of a member of the mitogen-activated protein kinase superfamily, p38gamma. These findings provide important insights into the modulation of apoptosis by TRAIL and IL-8 in ovarian cancer. The data suggest a potentially important role of IL-8 in protecting ovarian cancer cells from TRAIL-mediated apoptosis and signify a new potential chemotherapeutic target to augment TRAIL therapy.
肿瘤坏死因子相关凋亡诱导配体（TRAIL）已知可在许多恶性细胞中触发凋亡。当单独使用或与其他药物联合使用时，癌细胞对TRAIL诱导的细胞死亡有反应，而正常细胞已知对该配体相对不敏感，这使其成为治疗多种癌症的理想化合物。TRAIL通过与两种促凋亡死亡受体（DRs）DR4和DR5相互作用诱导凋亡。此外，它还可能与缺乏细胞内信号结构域的诱饵受体（DcRs）DcR1和DcR2结合，从而负向调节TRAIL诱导的凋亡。此前已表明，卵巢癌患者腹水中白细胞介素（IL）-8水平升高。因此，我们研究了IL-8在调节对TRAIL介导的凋亡敏感性中可能发挥的作用。我们用TRAIL处理TRAIL敏感细胞系OVCAR3一段时间，期间有或没有用IL-8预处理。在此我们展示了新的发现，即IL-8可阻断TRAIL诱导的细胞死亡，并能够将TRAIL敏感细胞系转变为TRAIL抗性细胞系。我们推测DR4和DR5表达降低可能导致TRAIL抗性。逆转录聚合酶链反应和流式细胞术均显示，用IL-8预处理OVCAR3细胞后，DR4表达降低。我们还表明，TRAIL能够在这些细胞中诱导半胱天冬酶-8裂解，而用IL-8预处理可阻断这种半胱天冬酶裂解。通过阵列分析并用其他技术进行验证，我们确定IL-8调节丝裂原活化蛋白激酶超家族成员p38γ的表达。这些发现为TRAIL和IL-8在卵巢癌中对凋亡的调节提供了重要见解。数据表明IL-8在保护卵巢癌细胞免受TRAIL介导的凋亡中可能发挥重要作用，并表明增强TRAIL治疗的新潜在化疗靶点。
