Co-occurrence of RUNX1 and ASXL1 mutations underlie poor response and outcome for MDS patients treated with HMAs

The molecular determinants of the clinical response to Hypomethylating agents (HMAs) in patients with myelodysplastic syndromes (MDS) are unclear. We analyzed 84 adult patients with MDS who received hypomethylating agents (HMAs) and identified somatic mutations and their relationship to clinical response and survival. The results showed in the MDS patients with ASXL1 mutations,the most frequent co-occurring mutations were RUNX1 mutations, with a significant higher frequency of 43% compared to 17% in wild-type ASXL1 (P = 0.032). ASXL1 mutation demonstrated a significant negative overall response rate (8% vs. 29.4%, x2 = 5.228, P = 0.022), particularly when co-occurring with RUNX1 mutations (P = 0.008). And all patients with RUNX1 and ASXL1 mutations died with a shorter median overall survival of only 14 months (P = 0.002). Moreover, TP53 mutations were associated with unfavorable-risk cytogenetic changes, and responded well to HMAs, with the exception of one case with RUNX1 and ASXL1 gene mutation. In a word, RUNX1 mutations are frequently found in MDS patients with ASXL1-mutations, and Co-occurrence of RUNX1 and ASXL1 mutations are associated with poor response to HMAs and inferior survival.