HMGB1/GSK-3β/HIF-2a轴调控放疗后残存胰腺癌细胞去分化机制研究

It was the main cause of tumor recurrence that residual tumor cells’ dedifferentiation obtained stem cells phenotype and function following radiotherapy . Stem cell related transcription factors and inflammatory mediators in the microenvironment are associated with the tumor cell dedifferentiation. However, the exact mechanism is still unclear. HIF-2a is the check point in regulating stem cell related transcription factor ativation. Our preliminary experimental data indicated that HMGB1 was obviously increased in the plasma of recurrence pancreatic cancer patients. Exogenous HMGB1 could induce the radiotherapy resistant pancreatic non cancer stem cells’ dedifferentiation which is assocaited with the phosphorylation of GSK-3β and HIF-2a up-regulation. Therefore, we hypothesized that HMGB1 induced the dedifferentiation of radiotherapy resistant pancreatic cancer cells by GSK-3β/HIF-2a pathway. To confirm the hypothesis, in vitro, firstly, we will clarify the function of HMGB1/HIF-2a mediating the radiotherapy resistant pancreatic cancer cells’ dedifferentiation; then we will prove the mechanism of GSK-3β modulating HIF-2a phosphorylation. And in vivo, we will furthering confirm the mechanism that HMGB1/GSK-3β/HIF-2a axis modulated radiotherapy resistant pancreatic cancer cells’ dedifferentiation leading to cancer recurrence through copying the orthotopic pancreatic cancer model with wide type and TLR2-/- mice. The present work will give us a new idea for the therapy of pancreatic cancer recurrence.

放疗抵抗的残存肿瘤细胞去分化而获得干细胞表型和功能是导致肿瘤复发的主要原因。肿瘤微环境中的炎症介质及细胞干性转录因子激活与去分化密切相关，然而其确切机制尚未阐明。研究表明HIF-2a是激活肿瘤细胞干性转录因子的核心分子，且我们预实验发现胰腺癌复发患者血清HMGB1表达水平升高，体外HMGB1可诱导放疗抵抗细胞去分化，这一现象与GSK-3β磷酸化及核内HIF-2a表达增高相关，提示HMGB1可能通过调控GSK-3β/HIF-2a诱导胰腺癌细胞去分化。为证实以上假说：我们将首先通过体外实验明确HMGB1/HIF-2a途径在胰腺癌细胞去分化中的作用；然后，探明GSK-3β调控HIF-2a稳定性和活性的机制；最后用WT及TLR2-/-小鼠胰腺癌原位瘤模型观察HMGB1/GSK-3β/HIF-2a轴对胰腺癌复发、肿瘤细胞去分化的影响，从而为肿瘤复发的治疗提供新靶点。

放疗在促进胰腺癌细胞死亡的同时，也诱导残存肿瘤细胞干性增强，进而导致肿瘤复发，然而确切机制仍不明确。本课题通过分析TCGA数据库，临床标本和人胰腺癌细胞系，检测发现放疗后HMGB1表达水平明显增高；体内外分子生物学研究发现，HMGB1可以促进放疗残存胰腺癌细胞发生EMT转化，进而促进转移；可以促进CD133+细胞自我更新和增殖，维持CD133+细胞的干性，而HMGB1受体TLR2和TLR4在这一过程中发挥着相反的生物学作用；促进CD133-去分化获得干性，主要是通过GSK3-YAP-HIF-1a发挥作用。相关的研究成果，已经发表在Plose one, Journal of Experimental & Clinical Cancer Research, EBioMedicne等杂志。本课题的实施明确了放疗后炎症因子在肿瘤复发转移中的用，尤其是HMGB1通过调控胰腺癌细胞去分化增强干性的确切作用及机制，从而为肿瘤复发的治疗提供新靶点。