Prognostic values of DLK1 for surgery and imatinib mesylate adjuvant therapy in gastrointestinal stromal tumors

The Delta-like 1 homolog (DLK1) gene is a paternal imprinting gene located on human chromosome 14q32, a site associated with frequent chromosomal mutations in GIST. The expression level of DLK1 is closely associated with the outcome of tumours. However, no study has reported the DLK1 expression in GIST. Here, we demonstrated that DLK1 showed low expression in GIST patients with low risk according to the modified National Institute of Health (NIH) criteria. With increasing tumour risk level, DLK1 gene and protein expression levels gradually increased. In the test cohort, tissue microarray data showed that DLK1 protein expression was significantly associated with tumour size, mitotic figure count, NIH risk level, and Ki67 expression. In terms of either disease-free survival (DFS) or overall survival (OS), the long-term outcome was significantly better in DLK1-negative patients than in DLK1-positive patients. Univariate and multivariate analyses suggested that DLK1 expression was an independent risk factor influencing tumour DFS. Additionally, for intermediate/high-risk GIST patients received postoperative IM adjuvant therapy, Kaplan-Meier analysis showed that IM adjuvant therapy was associated with a better outcome in DLK1-negative patients than in DLK1-positive patients. All of the above results were verified in the validation cohort. Taken together, DLK1 is a promising prognostic biomarker for GISTs that may help to predict surgical outcomes and guide adjuvant IM therapy.