Sequestration and suppressed synthesis of oncogenic HMGA1 using engineered adenoviruses decreases human pancreatic and breast cancer cell characteristics

HMGA1, an architectural transcription factor that plays a crucial role in tumorigenesis, chemotherapy resistance and cancer stem cell transformation in many human cancers, is intrinsically disordered and cannot be targeted by conventional small molecule drug therapy. While HMGA1 is required and essential for normal growth and development, HMGA1 expression occurs at very low levels in normal healthy adult cells. In contrast, HMGA1 is expressed at very high levels in many different types of human cancer cells. Since HMGA1 cannot be targeted using conventional small molecule drug therapy, alternative approaches are needed to target HMGA1 in new cancer therapies. Here, we explored the use of serotype 5 adenoviruses (Ad5) engineered 1) to sequester overexpressed HMGA1 in cancer cells using an HMGA1 hyper binding site (HBS) inserted into the Ad5 genome and 2) to suppress HMGA1 synthesis in cancer cells by incorporating exogenous genes into the Ad5 genome that encode an artificial HMGA1 cis-antisense transcript (AAT) and that encode a gene to express an HMGA1-targeted shRNA transcript (shRNA). The three engineered Ad5s were tested in MiaPaCa-2, PANC-1 and BxPC-3 human pancreatic cancer cell lines and in the ZR-75 human breast cancer cell line. Cancer cell viabilities and cell migration capability decreased by ~50-75% with HBS viruses and by 25-50% for shRNA and AAT viruses. Anchorage-independent migration capacity decreased by 60-70% with all three HBS, shRNA and AAT viruses. HMGA1 mRNA transcripts levels varied from 100 to 300 copies per cell in untreated cells and these levels were not significantly affected by treatment with the HBS and shRNA viruses, however the HMGA1 mRNA levels increased by ~3-fold upon AAT virus treatment. HMGA1 protein levels decreased in the range of 40, 50 and 70% with shRNA, AAT and HBS viruses, respectively. The HBS virus designed to sequester HMGA1 proved most effective overall in suppressing HMGA1 oncogenic activity in these in vitro cell-based studies compared to the AAT and shRNA viruses.