BPIFB1基因通过CXCL12/CXCR4调节轴参与鼻咽癌发生发展的分子机制

In our previous projects, we have found that the downregualtion of BPIFB1 gene in nasopharyngeal carcinoma (NPC) was a poor NPC prognosis factor, and was negatively associated with the degrees of tumor associated marcrophage (TAM) infiltration and the expression levels of IL-6 in NPC tissues. Re-expression of BPIFB1 could inhibit NPC cell proliferation, induce NPC cell arrest and promote NPC cell apoptosis through STAT3 and MAPK pathways. But as a secreted protein, how BPIFB1 regulates intracellular signaling pathways and its impact on the tumor microenvironment of NPC has not been studied in depth. Using a yeast two-hybrid strategy, we have found that BPIFB1 may interact with cytokine CXCL12. Whereas it was reported that CXCR4, the receptor of CXCL12, was highly expressed in NPC, the mechanisms of the CXCL12/CXCR4 axis in the pathogenesis of nasopharyngeal carcinoma is worthy of further investigation. In the proposed project, we intend to elucidate, in detail, the interaction between BPIFB1 and CXCL12/CXCR4 axis, the impact on their downstream signaling pathways, the malignant phenotype of NPC, and on the regulation of the NPC microenvironment. We are intending to preliminarily clarify the function of BPIFB1 in the carcinogenesis and progression of NPC. We will also investigate the mechanisms of the regulation of BPIFB1 in NPC and study the feasibility of small molecule components to induce BPIFB1 re-expression and its potential clinical applications in NPC.

我们发现BPIFB1基因低表达是鼻咽癌不良预后因素，且与癌组织中巨噬细胞浸润及IL-6等因子分泌负相关，重表达BPIFB1可通过STAT3、MAPK等通路阻滞鼻咽癌细胞增殖诱导凋亡。但分泌性蛋白BPIFB1如何调控细胞内的信号通路，及它对肿瘤微环境的影响还有待深入研究。经酵母双杂交我们发现BPIFB1可与趋化因子CXCL12结合，而CXCL12的受体CXCR4在鼻咽癌中高表达已有报道，但CXCL12/CXCR4调节轴在鼻咽癌发病过程中的机制值得进一步探讨。本项目拟研究BPIFB1与CXCL12及CXCR4的相互作用，并通过CXCL12/CXCR4调节轴对鼻咽癌细胞内信号通路及恶性生物学表型的影响，以及对鼻咽癌细胞微环境的调控，初步明晰BPIFB1在鼻咽癌发生发展过程中的作用机制；通过探讨BPIFB1在鼻咽癌中的表达调控机制，考察小分子药物诱导BPIFB1重表达的可行性及潜在的临床应用前景。

BPIFB1（别名LPLUNC1），是BPI折叠蛋白家族成员。该基因是我室在前期研究中利用cDNA微阵列技术联合抑制性消减杂交（suppression-subtractive hybridization，SSH）分离鉴定的鼻咽部相对特异表达基因。BPIFB1在鼻咽癌中表达显著下调，且其低表达与鼻咽癌患者的不良预后相关。放射治疗是目前鼻咽癌临床治疗中的主要手段，尽管放疗可以达到较好的局部控制效果，但仍有较高比例患者出现放疗抵抗，导致局部复发和远处转移，成为治疗失败的主要原因。因此在本课题中我们对BPIFB1在鼻咽癌放疗抵抗及侵袭转移过程中发挥的作用进行了探究。.我们首次验证了我室自主克隆的鼻咽部相对特异表达基因BPIFB1可以抑制鼻咽癌的侵袭与转移，促进鼻咽癌的放疗敏感性。具体来说，BPIFB1可以在细胞膜表面结合细胞外基质蛋白VTN以及间质细胞标志物VIM，一方面，BPIFB1通过结合抑制VTN，进而抑制VTN/ITGAV复合物的形成及下游FAK-Src-ERK信号通路的激活。此外，BPIFB1还可以抑制VTN、VIM介导的EMT进程，最终抑制鼻咽癌的侵袭与转移；另一方面，BPIFB1通过结合VTN，进而抑制ATM-Chk2和ATR-Chk1修复通路的激活，降低放疗后鼻咽癌细胞的增殖能力，促进细胞的凋亡，最终增强细胞的放疗敏感性。所以，我们首次找到BPIFB1的相互作用蛋白VTN和VIM，以及它们在鼻咽癌发生发展中发挥的作用及机制，它们有望成为鼻咽癌诊断和预后的新的分子标记，靶向BPIFB1和VTN及VIM之间的相互作用可以成为鼻咽癌潜在的治疗新策略。