Suppression of Mammary Tumorigenesis in Transgenic Mice by the RXR-Selective Retinoid, LGD1069

The study demonstrated that the RXR-selective retinoid LGD1069 effectively suppressed mammary tumorigenesis in C3(1)-SV40 Tag transgenic mice without observable toxicity, unlike the RAR-selective retinoid TTNPB, which showed modest chemopreventive effects but was highly toxic. LGD1069 extended the median time to tumor development from 129 to 156 days and reduced tumor multiplicity by approximately 50% at the higher dose. In contrast, TTNPB delayed tumor development but did not affect tumor multiplicity and caused significant toxicity, including skin erythema and hair loss. These findings suggested that receptor-selective retinoids could separate cancer preventive effects from toxic effects, highlighting their potential as breast cancer prevention agents.