(S (S (PP (IN Besides) (S (VP (VBG determining) (NP (NP (BASENP (DT the) (NN gene) (POS 's)) (NN importance)) (PP (TO to) (BASENP (DT the) (NN immune) (NN system))))))) (COMMA ,) (S (BASENP (NNP Choi) (CC and) (NNS colleagues)) (VP (VBP have) (VP (VBN developed) (NP (BASENP (NN technology)) (VP (VBN needed) (S (VP (TO to) (VP (VP (VB spur) (NP (BASENP (DT the) (NN creation)) (PP (IN of) (BASENP (NN natural) (NNS killers))))) (PP (IN from) (NP (BASENP (DT a) (NN person) (POS 's)) (BASENP (JJ own) (NN bone) (NN marrow) (NN stem) (NNS cells))))))))))))) (PERIOD .))