ALOX5 exhibits anti-tumor and drug-sensitizing effects in MLL-rearranged leukemia

MLL-rearranged acute myeloid leukemia (AML) remains a fatal disease with a high rate of relapse and therapeutic failure due to chemotherapy resistance. In analysis of our Affymetrix microarray profiling of human AML and normal control samples, we found that ALOX5 is especially down-regulated in MLL-rearranged AML. Our colony forming/replating and bone marrow transplantation (BMT) assays showed that Alox5 exhibited a moderate anti-tumor effect both in vitro and in vivo. Strikingly, leukemic cells with Alox5 overexpression showed a significantly higher sensitivity to the standard chemotherapeutic agents, i.e., doxorubicin (DOX) and cytarabine (Ara-C). The drug-sensitizing role of Alox5 was further confirmed in human and murine MLL-rearranged AML cell models in vitro, as well as in the in vivo MLL-rearranged AML BMT model coupled with treatment of “5+3” (i.e. DOX plus Ara-C) regimen. Our RNA-seq analysis showed that Stat and K-Ras signaling pathways were negatively correlated with Alox5 overexpression in MLL-AF9-leukemic blast cells, implying targeting those pathways likely contributes to Alox5’s functions. Collectively, our work shows that ALOX5 plays a moderate anti-tumor role and functions as a drug sensitizer, with a therapeutic potential, in MLL-rearranged AML. To delineate the potential molecular mechanism underlying the anti-tumor and drug-sensitizing effects of Alox5, we performed RNA sequencing (RNA-seq) of two pairs (4 samples) of mouse BM leukemic blast cells collected from the MA9_Ctrl and MA9_Alox5 mice in secondary BMT assays.

伴MLL重排的急性髓系白血病（MLL-rearranged acute myeloid leukemia, AML）仍是一类致死性疾病，因化疗耐药导致复发率高、治疗失败率居高不下。我们通过对人类AML样本与正常对照样本的Affymetrix基因芯片表达谱分析发现，ALOX5在伴MLL重排的AML中呈现显著低表达。我们的集落形成/再铺板实验与骨髓移植（bone marrow transplantation, BMT）实验结果显示，Alox5在体内外均表现出中等强度的抗肿瘤活性。尤为关键的是，过表达Alox5的白血病细胞对标准化疗药物多柔比星（doxorubicin, DOX）与阿糖胞苷（cytarabine, Ara-C）的敏感性显著升高。Alox5的药物增敏作用进一步在人类与小鼠的伴MLL重排AML细胞体外模型中得到验证，同时在联合“5+3”方案（即多柔比星联合阿糖胞苷）治疗的伴MLL重排AML骨髓移植体内模型中也得到了证实。我们的RNA测序（RNA-seq）分析显示，在MLL-AF9白血病原始细胞中，Stat信号通路与K-Ras信号通路的激活水平与Alox5过表达呈负相关，提示靶向这两条通路可能是Alox5发挥生物学功能的潜在机制。综上，本研究证实ALOX5在伴MLL重排的AML中发挥中等强度的抗肿瘤作用，并可作为药物增敏剂，具备潜在治疗价值。为阐明Alox5抗肿瘤与药物增敏作用的潜在分子机制，我们对二次骨髓移植实验中取自MA9_Ctrl与MA9_Alox5小鼠的骨髓白血病原始细胞进行了RNA测序，共设置2对样本（合计4份）。