SEOUL — Derek Hough, three-time winner of “Dancing with the Stars,” and Korean pop star BoA have been cast in dance film “COBU 3D.”The pair play members of rival New York families – the owners of underground night clubs — who compete in a dance contest and fall in love. Pic is helmed by Duane Adler, who penned “Save the Last Dance” and “Step Up,” and their sequels. Robert Cort, who exec produced the “Save the Last Dance” pics, produces, with Korea’s CJ Ent. and BoA’s agency SM Ent. on board. Lionsgate Intl. has taken sales rights for all territories except Korea, China and Japan, which are being handled by CJ Ent. Shooting starts in New York and Toronto in the spring. Pic is set to be released in early 2012.