(S (S (BASENP (JJ Recent) (NNS tests)) (VP (VBP have) (VP (VBN shown) (SBAR (IN that) (S (BASENP (DT an) (JJ inexpensive) (NN drug)) (VP (MD may) (VP (VB be) (ADJP (JJ able) (S (VP (TO to) (VP (VB kill) (NP (BASENP (NN cancer) (NNS cells)) (PP (IN in) (BASENP (NNP humans))))))))))))))) (PERIOD .))