PBX1 gene transcription is directly stimulated by the NOTCH3 coactivator complex (Park et al. 2008). NOTCH3 gene is amplified in high-grade ovarian serous carcinoma and NOTCH3 overexpression contributes to cancer cell growth (Park et al. 2006). Overexpression of NOTCH3 in high-grade ovarian serous carcinoma correlates with overexpression of PBX1 (Park et al. 2006, Park et al. 2008). PBX1 gene encodes a homeodomain transcription factor PBX1 which is a B cell leukemia (B-ALL) oncogene (Nourse et al. 1990, Kamps et al. 1991) and is also overexpressed in melanoma (Shiraishi et al. 2007).