Compositions and methods for NK cell based treatments, and particularly NK cells that express and intracellularly retain IL-2, are presented in which the NK cells are stimulated with a chimeric protein that has a cancer cell targeting portion and an IL-12 portion. Beneficially, such chimeric protein has substantially reduced systemic toxicity and induces IFN-γ secretion in a targeted manner. Moreover, chimeric proteins contemplated herein also significantly enhanced IFN-γ secretion in NK cells that express and intracellularly retain IL-2 as compared to native NK cells. Preferred chimeric proteins comprise SEQ ID NO:1 or SEQ ID NO:2, and SEQ ID NO:3.