Interaction of doxorubicin with a regulatory element of hmga1 and its in vitro anti-cancer activity associated with decreased HMGA1 expression

• Doxorubicin (DOX) exhibits stabilizing effect leading to strong complex formation between DOX and hmga1.
• The binding of DOX to DNA is exothermic in nature favoured by negative enthalpy and positive entropy changes.
• DOX causes significant downregulation of HNGA1 both at transcriptional as well as translational level.
• DOX brings in its anti-cancer activity via intercalation resulting in regression in hmga1 expression.

High mobility group A1 (HMGA1) non-histone chromatin protein is known as an architectural transcription factor that regulates transcription of various genes. HMGA1 is highly expressed in almost all human cancers and considered as a potent tumor marker. Because of its association with cancers, hmga1 is considered as a critical target for anti-cancer drugs. In the present study, we report interaction of doxorubicin (DOX) with a short deoxyoligonucleotide (−1917 to −1940) within a regulatory element of hmga1 and its subsequent effect on expression of HMGA1 in breast cancer MCF7 cells. Binding of DOX to DNA was found to be strong (Ka, 5.2 × 105 M−1) and thermodynamically favorable by both negative enthalpy (ΔH, −8.1 ± 0.25 kcal M−1) and positive entropy changes (TΔS, 21.1 ± 5.2 kcal M−1) at 20 °C. A significant increase in melting temperature of DNA in presence of DOX by +10 °C was accompanied by substantial quenching of fluorescence of DOX (∼85%) at 595 nm and hypochromic change (∼40%) at 500 nm absorption spectra of DOX along with a bathochromic shift of ∼5 nm. Reduced expression of HMGA1 by ∼60% both at mRNA and protein level and associated cell death in presence of DOX was observed in breast cancer cells. Therefore, hmga1 is a promising chemotherapeutic target in treating human malignancies.