Insulin-like growth factor (IGF) binding protein (IGFBP6), a 240 amino acid protein, contains an IGFBP N-terminal domain and a thyroglobulin type-1 domain. It modulates the activity of IGF and shows independent effects of IGF, such as growth inhibition and apoptosis. It can decrease the proliferation and survival of cancer cells such as lung cancer cells and naso-pharyngeal cancer cells. IGFBP-6 is distinctive for its 50-fold higher binding affinity for IGF-II over IGF-I and this specificity makes it an attractive potential therapeutic candidate for IGF-II-dependent pediatric malignancies such as rhabdomyosarcoma (RMS).