乏氧微环境下STIM1在胰腺癌中的表达调控机制及其功能研究

Calcium (Ca2+) is the important messenger of cellproliferation, differentiation and gene transcription, while stromal interaction molecule 1 (STIM1) located on the endoplasmic reticulum is calcium sensor and can perceive Ca2+ concentration. STIM1 can activate calcium -operated calcium channels and cause extracellular Ca2+ influx. Therefore, STIM1, as an important constituent molecules of calcium pool channel, plays an important role in cell mitosis, proliferation, apoptosis, secretion, adhesion and motility. We found that the expression of STIM1 was increased in pancreatic cancer cells, and its overexpression was corelated with poor prognosis of patients with PC, which may suggested STIM1 is one important molecular in the invasion and metastasis of pancreatic cancer cells. However, its expression regulation mechanism has not been elucidated. Hypoxia is one important microenvironment feature of pancreatic cancer. Our previous studies demonstrated that HIF can promote the expression of STIM1 under hypoxia suggesting the possible role of HIF-1/STIM1/Ca2+/ downstream function molecular involved in the invasion and metastasis of pancreatic cancer. We also found that, under hypoxic conditions, ERK activation was enhanced, which not only promoted the expression of HIF , but also activated STIM1. Therefore, we hypothesized that the presence of STIM1 expression regulation loop ERK/HIF/STIM1 and activation pathway pERK/pSTIM1. In this study, we will focus on the regulation mechanism and activation mechanism of STIM1 in pancreatic cancer under hypoxic microenvironment and explore its role in the invasion and metastasis of pancreatic cancer, and to explore its prognostic significance and clinical applications.

Ca2+是细胞生命活动的重要信使分子，而STIM1 是内质网膜上的Ca2+感受蛋白，能感知Ca2+的浓度，激活钙池操纵钙离子通道，引起细胞外Ca2+内流，因此STIM1 是细胞主动吸收Ca2+的重要分子，控制着细胞增殖、凋亡、粘附、运动。我们发现STIM1 在胰腺癌中表达增加，与患者预后不良密切相关，但其表达调控机制尚未阐明。乏氧是胰腺癌组织重要微环境，前期研究提示，乏氧诱导因子HIF 促进STIM1 的表达，推测乏氧条件下的HIF-1/STIM1/Ca2+/下游分子直接参与了胰腺癌的侵袭转移；我们还发现乏氧条件下ERK的活化增强，不仅促进HIF 的表达，而且进一步活化了STIM1。因此我们推测STIM1 的表达存在ERK/HIF/STIM1 调控环路和pERK/pSTIM1活化通路。本研究拟围绕着STIM1在胰腺癌乏氧微环境下的表达调控和活化机制，探讨其在胰腺癌侵袭中的地位和应用价值。

据报道，在几种癌症的进展中基质相互作用分子1（STIM1）的过表达起重要作用。然而，STIM1过表达的机制及其与胰腺导管腺癌（PDAC）缺氧的关系仍不清楚。我们通过免疫组织化学法检测STIM1和HIF-1α在TMA中的表达，包括胰腺癌和胰腺正常组织，并对其与临床病理参数的关系进行统计学分析。采用Q-PCR，Western blot，CHIP和双荧光素酶检测证实HIF-1α与STIM1在胰腺癌PANC-1细胞中的转录调控关系。与正常组织相比（p <0.05），STIM1和HIF-1α在癌症中表达水平均较高。 Kaplan-Meier方法显示，较高的HIF-1α和STIM1表达水平与无病生存率下降趋势显著相关（分别为p = 0.025和p = 0.029）。在癌组织和胰腺癌细胞系中，HIF-1α的表达与STIM1（rs = 0.3343，p = 0.0011）的表达显著正相关。此外，ChIP和荧光素酶测定显示HIF-1α与STIM1启动子存在结合并调节其在PANC-1细胞中的表达。由此得出在缺氧微环境中，由HIF-1α介导的STIM1的表达上调会促进PDAC进展。 HIF-1α和STIM1是PDAC治疗的潜在预后标志物和/或治疗靶标。