tokens: These E1a reiteration mutants could be propagated in HeLa , A549 , and KB cells ; they were genetically stable ; and they killed CREF cells at a strikingly high frequency .
folded_tokens: these e1a reiteration mutants could be propagated in hela , a549 , and kb cells ; they were genetically stable ; and they killed cref cells at a strikingly high frequency .
labels: O B-virus I-virus I-virus O O O O B-cell_line O B-cell_line O O B-cell_line I-cell_line O O O O O O O O O B-cell_line I-cell_line O O O O O O