<i>ABL</i> Genomic Editing Sufficiently Abolishes Oncogenesis of Human Chronic Myeloid Leukemia Cells In Vitro and In Vivo

• Main Authors: Shu-Huey Chen, Yao-Yu Hsieh, Huey-En Tzeng, Chun-Yu Lin, Kai-Wen Hsu, Yun-Shan Chiang, Su-Mei Lin, Ming-Jang Su, Wen-Shyang Hsieh, Chia-Hwa Lee
• Format: Article
• Language: English
• Published: MDPI AG 2020-05-01
• Series: Cancers
• Subjects: CRISPR/Cas9; gene edit; Philadelphia chromosome; BCR-ABL; CML
• Online Access: https://www.mdpi.com/2072-6694/12/6/1399

Chronic myelogenous leukemia (CML) is the most common type of leukemia in adults, and more than 90% of CML patients harbor the abnormal Philadelphia chromosome (Ph) that encodes the BCR-ABL oncoprotein. Although the ABL kinase inhibitor (imatinib) has proven to be very effective in achieving high remission rates and improving prognosis, up to 33% of CML patients still cannot achieve an optimal response. Here, we used CRISPR/Cas9 to specifically target the <i>BCR</i>-<i>ABL</i> junction region in K562 cells, resulting in the inhibition of cancer cell growth and oncogenesis. Due to the variety of <i>BCR</i>-<i>ABL</i> junctions in CML patients, we utilized gene editing of the human <i>ABL</i> gene for clinical applications. Using the <i>ABL</i> gene-edited virus in K562 cells, we detected 41.2% indels in <i>ABL</i> sgRNA_2-infected cells. The <i>ABL-</i>edited cells reveled significant suppression of BCR-ABL protein expression and downstream signals, inhibiting cell growth and increasing cell apoptosis. Next, we introduced the <i>ABL</i> gene-edited virus into a systemic K562 leukemia xenograft mouse model, and bioluminescence imaging of the mice showed a significant reduction in the leukemia cell population in <i>ABL</i>-targeted mice, compared to the scramble sgRNA virus-injected mice. In CML cells from clinical samples, infection with the <i>ABL</i> gene-edited virus resulted in more than 30.9% indels and significant cancer cell death. Notably, no off-target effects or bone marrow cell suppression was found using the <i>ABL</i> gene-edited virus, <i>ensuring both </i>user safety<i> and</i> <i>treatment efficacy</i>. This study demonstrated the critical role of the <i>ABL</i> gene in maintaining CML cell survival and tumorigenicity in vitro and in vivo. <i>ABL</i> gene editing-based therapy might provide a potential strategy for imatinib-insensitive or resistant CML patients.