亚砷酸撤除过程中PML-RARa蛋白溶性的改变及其与早幼粒细胞白血病复发的关系研究

亚砷酸是世界公认的治疗APL的有效药物之一，可特异性诱导致癌蛋白PML-RARa由核质转移直至核基质（即可溶转变不可溶），随后经蛋白酶体降解，最终达到治疗目的。但是，随着临床的广泛应用，患者经该药治疗后出现病情复发和耐药等现象，直接威胁其生命。因此，揭示APL复发和耐药的机制迫在眉睫。研究表明，砷剂诱导PML-RARa融合蛋白的溶性转变是治疗APL的关键。我们课题组首次发现，当APL细胞或PML-RARa高表达293T细胞亚砷酸处理后再移除砷，该融合蛋白由不可溶回复至可溶。本项目致力于研究砷剂撤除过程中 PML-RARa（或PML）蛋白溶性逆向改变的机制及在疾病复发过程中的生理学意义，进而为治疗APL疾病的复发和耐药提供理论依据，并有望为As2O3治疗APL病人的有效性提供预测指标。

PML-RARa fusion protein (containing PML zinc finger protein and retinoic acid receptor alpha) is a unique and characteristic feature of human acute promyelocytic leukemia (APL). This fusion protein often plays a key role in driving the development and progression of the APL disease. Arsenic trioxide (As2O3) is a highly effective treatment for patients with refractory relapsed acute promyelocytic leukemia. In addition, it was also reported that As2O3 improves event-free survival and overall survival of adult APL when As2O3 is used as a consolidation treatment after obtaining the first remission. Regarding the mechanism of PML proteins degradation, it has been demonstrated that As2O3 directly binds to cysteine residues of Zinc Fingers in RBCC domain of PML-RARα fusion protein (i.e., replacement of zinc by As2O3), resulted in facilitating oligomerization of PML-RARa oncoprotein and then induces the nucleoplasmic PML-RARαfusion (and PML) protein toward the nuclear matrix, finally degraded by proteasome pathway. Recently, a few reports indicated that there are many APL patients relapsed after the arsenic therapy, and some of them are showed much resistance to arsenic. However, it is unclear about the detailed molecular mechanism why the APL patient is able to relapse after arsenic treatment, and it should be clearly identified in the near future. In fact, PML-RARα proteins in nucleoplasmic toward the nuclear matrix is a key condition for PML-RARα proteins degradation (i.e., mobility shift). Surprisingly, in our preliminary experiment we found that PML-RARα fusion protein in matrix was re-returned to nucleoplasmic (namely, PML-RARα fusion protein expressed again in cells) when we removed the As2O3 in culture medium of NB4 cell or PML-RARα transfected HEK293T cells. Thus, we are much interested in this phenomenon why removing the As2O3 is able to reverse the PML-RARα fusion protein form matrix to nucleoplasmic? Does it related with APL patients relapsing after the finishing arsenic treatment (i.e., period of without arsenic treatment)? Given these discoveries, the interesting new results call into questions what is the exact molecular mechanism of PML protein mobility changes following exposure to arsenic? (2) Is PML-RARα protein from matrix to nucleoplasmic related with relapsing, etc? Our results are expected to explain the exact mechanism of PML-RARa fusion protein mobility changes, which will improve the life span of APL patients after treatment of arsenic in near future.