High mobility group A1 and cancer: potential biomarker and therapeutic target.

The High Mobility Group A1 (HMGA1, formerly HMG-I/Y) gene is highly expressed during embryogenesis and in virtually all aggressive human cancers studied to date, although its role in these settings is only beginning to emerge. Moreover, high levels of expression portend a poor prognosis in some tumors. Increasing evidence suggests that the HMGA1 protein functions as a master regulator with a critical role in normal development and tumor progression in diverse malignancies. These proteins contain AT-hook DNA binding domains that mediate binding to AT-rich regions of chromatin. After binding to DNA, HMGA1 alters DNA structure, and orchestrates the assembly of a transcriptional complex or "enhanceosome" to regulate gene expression. Previous studies indicate that HMGA1 participates in regulating fundamental cellular processes, including transcription, cell cycle progression, embryonic development, neoplastic transformation, differentiation, senescence, viral integration, and DNA repair by virtue of its ability to interact with other proteins, bind to DNA, and modulate gene expression. Recent studies also link HMGA1 expression to poor differentiation status and a refractory, stem cell-like state in aggressive cancers. Together, these findings suggest that HMGA1 could serve as a useful biomarker and therapeutic target in advanced malignancies. Here, we focus on prior studies implicating HMGA1 in the pathogenesis of refractory human tumors arising from diverse tissues and its potential role as a biomarker. We also review previous attempts to target HMGA1 pathways in cancer. Further study of HMGA1 promises to have a major impact on our ability to understand and treat cancer.