ABSTRACT
Objective:To investigate the clinical characteristics and prognosis of patients with RUNX1-RUNX1T1 fusion gene-positive acute myeloid leukemia (AML) with ASXL2 gene mutation.Methods:The clinical data of 145 newly diagnosed RUNX1-RUNX1T1 fusion gene-positive AML patients treated at the Second Hospital Center of Shanxi Medical University from October 2010 to March 2021 were retrospectively analyzed. Sanger sequencing was used to detect the gene mutation. According to the presence or absence of ASXL2 gene mutation, the patients were divided into mutation group and non-mutation group. The clinical characteristics, gene mutations and prognosis were compared among the two groups.Results:Among 145 AML patients with positive RUNX1-RUNX1T1 fusion gene, we identified recurrent mutations of c-kit, ASXL2, N/KRAS, FLT3, ASXL1, TET2, NPM1 and DNMT3A genes, with mutation rates of 40.7% (59/145), 20.7% (30/145), 15.9% (23/145), 12.4% (18/145), 11.7% (17/145), 11.0% (16/145), 5.5% (8/145), and 2.1% (3/145), respectively. A total of 18 mutation sites were detected in 30 patients with ASXL2 gene mutations including 5 point mutations and 13 frameshift mutations, which mainly occured in the exons 12 and 13. Lactate dehydrogenase (LDH) at initial diagnosis of 30 AML patients with ASXL2 mutation was lower than that of those with ASXL2 non-mutation ( Z = 2.34, P = 0.020), while prothrombin time (PT) of AML patients with ASXL2 mutation was longer than that of those with ASXL2 non-mutation ( Z = 1.99, P = 0.047). A total of 21 (21/30, 70%) patients simultaneously had other gene mutations. The incidence of RAS mutations in patients with ASXL2 mutation was higher than that those with ASXL2 non-mutation, and the difference was statistically significant [30.0% (9/30) vs. 12.1% (14/115), χ2 = 4.41, P = 0.036]. There were no statistically significant differences in complete remission rate [86.7% (26/30) vs. 74.8% (86/115)] and recurrence rate [43.3% (13/30) vs.31.3% (36/115)] of patients with ASXL2 mutation and ASXL2 non-mutation ( χ2 = 0.39, P = 0.534; χ2 = 0.54, P = 0.432). The median overall survival (OS) time was 26 months (1-135 months) and 30 months (1-120 months), respectively in patients with ASXL2 mutation and ASXL2 non-mutation; the median disease-free survival (DFS) time was 14 months (0-60 months) and 13 months (0-94 months), respectively in patients with ASXL2 mutation and ASXL2 non-mutation; and the differences in OS and DFS were not statistically significant of both groups ( χ2 = 0.05, P = 0.822; χ2 = 0.34, P = 0.562). Compared with ASXL1 mutant patients, cases with ASXL2 mutation had higher OS and DFS rates, and the differences were statistically significant ( P = 0.003, P = 0.007). The differences in OS and DFS between patients with ASXL2 mutations and those with positive mutations of c-kit, RAS, FLT3, TET2, NPM1, DNMT3A were not statistically significant (all P > 0.05). Conclusions:RUNX1-RUNX1T1 positive AML patients with ASXL2 mutation tend to have low LDH and high PT, and often coexist with RAS mutations, and their prognosis is better than that in patients with ASXL1 positive mutation.
ABSTRACT
Objective To knock out Asxl2 gene in murine embryonic fibroblast cell line NIH3T3 using CRISPR/Cas9n system. Methods A pair of sgRNAs which targeted exon 5 of Asxl2 gene were designed and subcloned into the pX462 vec?tor. The recombined plasmids were verified by sequencing and transfected into NIH3T3 cell line. Single cells were isolated through serial dilutions, followed by an expansion period to obtain new monoclonal cell lines. The genomic DNA of the new monoclonal cell lines was extracted and a DNA fragment flanked the target site was amplified by genotyping PCR then se?quenced. Lastly, western blotting were applied to confirm whether Asxl2 was successfully knocked out. Results The CRIS?PR/Cas9n plasmids that targeted Asxl2 were successfully constructed. NIH3T3 cells were co-transfected with the two recom?binant constructs. After puromycin selection, subclonal cell lines were obtained and one of them was validated by genotyping PCR-sequencing. Western blotting also confirmed that Asxl2 was completely depleted in the NIH3T3 cell line. Conclu?sion CRISPR/Cas9n plasmids that targeted Asxl2 were successfully constructed therefore a Asxl2 knockout NIH3T3 stable cell line was established via this system.