Recombinant DNA Advisory Committee - 3/3-4/94 
human lung cancer nude mouse model. These data has been subjected to 
biomathematics analysis with conjQdence intervals between 30 to 100%. Dr. Roth said 
that this number is unexpectedly high. Dr. Straus questioned the interpretation of this 
data. Some of the effect could be explained by the DNA copy number per cell since Dr. 
Roth assumed that every DNA copy represents a cell. Dr. Roth said that single copy 
integration has been observed in the cell line. Dr. Parkman said that 60% efficiency 
would not be surprising for the transduction of a cell line if 100% of cells are in cell 
cycling. What percentage of wild-type tumor cells are in cycling? Dr. Roth said that he 
does not know the answer to that question. Dr. Lang Chang, Institute of Biomedical 
Sciences, Academia Sinica, Taipei, from the audience questioned the interpretation of 
the data on transduction efficiency. 
Dr. Roth said that the antitumor effect of the retroviral constructs on the tumor growth 
is reproducible and significant, regardless of the underlying mechanism. Ms. Grossman 
emphasized that precise knowledge about the proposed constructs is essential for human 
studies. The RAC should not recommend approval of a human trial if the vectors to be 
applied to humans are not adequately characterized. Again, Ms. Grossman raised 
questions on uncertainty regarding the size of DNA fragments from Kpn digests of vector 
transduced cells. Dr. Roth conceded that uncertainty resulted from the problem that the 
sequence of the vector is not presented, thus, he is unable to provide size information. 
Dr. Straus said that the animal data is impressive and justifies the human study. 
However, Dr. Straus agreed with Ms. Grossman's comment that a complete sequence of 
the vector construct is essential, and data demonstrating the integrity of the vector 
structure is necessary in order to proceed with the human study. Dr. Post said that the 
mechanism of the "bystander" effect and transduction efficiency in the animal model are 
not major issues; however, the complete vector sequence and the Southern blot data on 
the vector structure are essential. Dr. Post expressed his dissatisfaction with the data 
regarding the size of the DNA fragments, the Southern blot, and generally the 
characterization of the vector structure. 
Dr. Roth showed a DNA sequence of the vector in an attempt to address the question of 
the Kpn fragment size. Dr. Roth said that in this sequence, a large section of the actin 
promoter of the vector is not included. Dr. Post said that this missing sequence 
information appears to be the source of some of the uncertainty regarding the DNA 
fragment size. Dr. Post said that this missing information raises another question of 
whether there is another Kpn site within this actin promoter segment. Kpn was 
originally presumed by the principal investigator to be a single cut enzyme that digests 
the DNA at a single site in each of the two long terminal repeat regions of the vector. 
Dr. Roth said that an additional Kpn site is unlikely since only two predicted DNA 
fragments are generated by digestion with Kpn. Ms. Grossman questioned the data since 
the digests of the construct with the insert are the same as the vector by itself. Dr. 
Straus said that the gel experiment presented should be able to distinguish a size 
difference of 4 kb between the fragments from the vector and the construct with the 
insert according to the molecular size markers included in this experiment. Dr. Parkman 
said that the data presented is of such poor quality that it cannot be accepted as a basis 
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Recombinant DNA Research, Volume 19 
