PTHLH and neoplasm: However, in order to determine whether PTHrP overexpression might influence tumor formation caused by an established oncogene, we bred the MMTV-PyMT transgene onto Tet-PTHrP mice to generate MMTV-rtTA;TetO-PTHrP;MMTV-PyMT (Tet-PTHrP;PyMT) mice [68].