SOX9 in chemoresistance of intracellular cholangiocarcinoma (iCCA)

在大多数肝内胆管细胞癌（iCCA）患者中，全身化疗（如接受吉西他滨）仍然是唯一的方法，使他们有资格进行手术和姑息治疗，因为肿瘤在诊断时过于先进。然而，iCCA对当前治疗的反应非常弱。我们最近的研究发现，胆管细胞的主要转录因子9（SOX 9）的性别决定区Y盒（SRY-box）通过影响细胞周期检查点和下游p53信号在CCA细胞对吉西他滨治疗的化疗耐药性中起着至关重要的作用。我们进一步观察到iCCA中的S 0X 9表达受视黄酸-视黄酸受体（RAR）β轴调节。视黄酸主要在肝星状细胞活化过程中产生，这是导致纤维化的关键事件，并由炎症诱导。基于这些发现，我们在该项目中提出了两个假设：（I）在化疗期间，iCCA细胞经历细胞周期停滞，以避免通过细胞周期检查点蛋白的SOX 9依赖性激活而导致细胞死亡，以及（II）慢性炎症通过激活的HSC（释放视黄酸）在上调iCCA细胞中的SOX 9表达中起着至关重要的作用。为了证明所提出的假设，我们将解决五个关键问题：（1）RA-RAR如何调节iCCA中SOX 9的表达？(2)疾病环境（炎症和纤维化）调节SOX 9表达的机制是什么？(3)SOX 9是否通过上游调控ATR参与CHK 1转录激活？(4)SOX 9是否影响ATM-CHK 2-p53通路？(5)SOX 9如何介导iCCA的化疗耐药性？这些实验将阐明SOX 9如何促进iCCA中的化学抗性的详细分子机制，并提供在临床实践中克服SOX 9依赖性化学抗性的新方法。

In most patients of intrahepatic cholangiocarcinoma (iCCA), systemic chemotherapy such as receiving gemcitabine remains the only approach to render them eligible for surgery and palliative treatment, given that tumors are too advanced at the time of diagnosis. However, the response of iCCA to current treatments is very weak. Our recent study found that sex-determining region Y-box (SRY-box) containing gene 9 (SOX9), the master transcription factor of cholangiocytes, plays a crucial role in chemoresistance of CCA cells to gemcitabine therapy through impacting on cell cycle check points and downstream p53 signaling. We further observed that SOX9 expression in iCCA is regulated by the retinoic acid – retinoic acid receptor (RAR) axis. Retinoic acid is largely produced during activation of hepatic stellate cells, the key event leading to fibrogenesis and induced by inflammation. Based on these findings, we propose two hypotheses in this project: (I) During chemotherapy, iCCA cells undergo cell cycle arrest to avoid cell death through SOX9-dependent activation of cell cycle checkpoint proteins, and (II) chronic inflammation plays a crucial role in upregulating SOX9 expression in iCCA cells through activated HSC, which release retinoic acid. To prove the proposed hypotheses, we will address five key questions: (1) How does RA-RAR regulate expression of SOX9 in iCCA? (2) What are the mechanisms of the disease environment (inflammation and fibrosis) that modulate SOX9 expression? (3) Does SOX9 contribute to activation of CHK1 transcription through upstream modulation of ATR? (4) Whether, and if yes, how SOX9 influences the ATM-CHK2-p53 pathway? (5) How does SOX9 mediate chemoresistance of iCCA? These experiments will clarify detailed molecular mechanisms of how SOX9 contribute to chemoresistance in iCCA and provide a novel approach to overcome SOX9-dependent chemoresistance in clinical practice.