NF-κB介导的炎症调控通路在苦参碱抗白血病作用中的分子机制研究

Nuclear factor NF-κB functions as a central point linking inflammation and cancer. Its downstream targeted gene interleukin 6 (IL-6) and IL-6-mediated JAK/STAT3 signaling pathway plays an important role in leukemogenesis. Matrine is an alkaloid compound purified from Sophora flavescensm, which shows anti-inflammatory and anti-cancer acivities both in vitro and in vivo. However, the exact molecular targets or pathways contribute to its anti-cancer activities remains unclear. Our previous study found treatment with matrine could suppress the cell proliferation of human myeloid leukemia cells K562 significantly and down-regulate the expression of IL-6 in both transcriptional and protein level. Further investigations found that matrine could down-regulate the phosphorylation of STAT3 and JAK2 as well as that of nuclear factor κB（NF-κB). Based on these,findings, it is speculated that the anti-leukemia effects of matrine might be mediated via its regulating the activities of NF-κB signaling cohort in leukemia cells. In the present study, we aim to further validate the exact role of matrine in regulating the activities of NF-κB/IL-6 signaling cohort in molecular, cellular and mice model levels by using a matrine-treated leukimia cells model based studies. The findings in this study would decipher the molecular mechanisms via which matrine exert its anti-leukemia effect and shed some light on building novel strategies for treatment of leukemia.

NF-κB是联系炎症与肿瘤的关键核转录因子，其下游靶基因IL-6在白血病发生过程中发挥重要功能。苦参碱是中药苦参中分离出的一种生物碱，具有较为明确的抗炎抗肿瘤活性，但其是否通过NF-κB通路发挥抗肿瘤作用目前尚不清楚。我们的前期研究发现，苦参碱可显著抑制人白血病K562细胞增殖，降低其IL-6表达，同时抑制细胞内NF-κB及JAK2、STAT3的磷酸化。我们推测：苦参碱可能通过抑制NF-κB转录活性下调IL-6表达及其下游的JAK/STAT3通路活性，发挥抗白血病作用。本项目拟以苦参碱处理的白血病细胞为模型，从分子、细胞和整体动物水平确认苦参碱对NF-κB表达及转录活性作用，探讨NF-κB及其介导的IL-6/JAK/STAT3通路在苦参碱抗白血病作用中的分子机制，以期阐明苦参碱的抗白血病作用机制，为探索白血病治疗新策略提供实验依据。

苦参碱是中药苦参中分离出的一种生物碱，具有较为明确的抗炎抗肿瘤活性。我们的研究证实，苦参碱可显著抑制人白血病细胞增殖、抑制细胞IL-6表达及细胞内NF-κB、JAK2/STAT3信号通路关键分子的磷酸化。我们认为，IL-6及其介导的JAK/STAT3信号通路活性抑制是苦参碱作用的重要分子机制。但我们也发现，不同条件下苦参碱对IL-6及NF-κB分子的作用并不完全一致。0.8mg/mL浓度的苦参碱显著抑制NF-κB p65分子磷酸化，但更高浓度苦参碱（1.6 mg/mL）作用反而促进p65磷酸化。此外，尽管IL-6可增强细胞内JAK2及STAT3分子磷酸化、促进细胞增殖，但IL-6与苦参碱共处理却不能逆转或抵消苦参碱对白血病细胞的增殖抑制，提示IL-6及其下游的JAK2/STAT3信号通路可能并非苦参碱作用的单一的机制。我们目前的研究结果尚不能证实本研究的前期假设，即苦参碱通过抑制 NF-κB 进而调控下游的IL-6/JAK/STAT3通路，发挥抗白血病作用。进一步研究除了需要对苦参碱对NF-κB通路作用进一步明确外，苦参碱的抗白血病作用是否还存在其他相关的分子调控机制也是亟待回答的问题。.此外，我们研究发现，苦参碱可显著抑制白血病细胞c-Myc基因及其前体基因mRNA的表达，c-Myc是苦参碱处理后细胞中最早也是最快响应的分子，苦参碱处理后细胞中下调最显著的基因集也为c-Myc靶基因组。c-Myc基因敲除细胞对苦参碱作用的敏感性较野生型也明显降低。研究还观察到，苦参碱可显著抑制细胞内糖酵解关键酶HK2蛋白分子表达，这一作用也与c-Myc的表达调控相关。作为细胞内一种极为重要的转录因子，c-Myc调控的下游靶基因广泛参与细胞增殖、凋亡、代谢、分化及免疫调控等过程，c-Myc的转录也受细胞内多种膜受体信号通路的调控，在肿瘤包括白血病的发生发展过程发挥重要作用。结合课题组现有的研究结果，我们认为c-Myc可能才是苦参碱作用的关键靶点分子，此前研究中观察到的苦参碱的多种生物学效应，如细胞增殖抑制、凋亡诱导、周期阻滞、代谢调节及其对细胞内信号通路分子及相关激酶的作用可能都与c-Myc基因的调控有关，c-Myc可能是苦参碱关键作用的关键分子靶点介导了苦参碱的抗白血病效应。