MLL2 promotes cancer cell lymph node metastasis by interacting with RelA and facilitating STC1 transcription

Esophageal squamous cell carcinoma (ESCC) presents with lymph node metastasis in the early stages, limiting the opportunities for curative local resection, including endoscopic submucosal dissection (ESD). ESD is regarded as the standard treatment for early-stage ESCCs. However, radical surgery is recommended when lymph node metastasis risk exists. More efforts are needed to find the markers for early prediction and clarify the molecular mechanism underlying the pathogenesis of lymph node metastasis. Recently, aberrant regulation of gene expression by histone methylation modifiers has emerged as an important mechanism for cancer metastasis. Herein, we demonstrated that mixed-lineage leukemia 2 (MLL2) positively regulates gene expression programs associated with ESCC cell migration. MLL2 interacts with RelA in the nucleus to enhance transcription of stanniocalcin-1 (STC1) and to facilitate cancer metastasis. Meanwhile, MLL2 knockdown resulted in a significant decrease in the migration of ESCC cells. Clinically, high level of MLL2 was significantly associated with early-stage ESCC lymph node metastasis. In summary, these findings discovered a previously unidentified molecular pathway underlying the coordinated regulation of metastasis-related STC-1 expression by MLL2 and RelA and highlighted the critical role of MLL2 in ESCC.