Recombinant DNA Advisory Committee - 6/9-10/94 
Dr. H. Ginsberg cautioned against assaying for adenovirus in the supernatant of the 
transduced cells since infected cells will not be lysed immediately and released into the 
supernatant. More than 90% of adenovirus is associated with the cell pellets. 
Investigator Response-Dr. Roth 
Dr. Roth hypothesized about the mechanism for the combined effect of p53 and 
cisplatin. The function of wildtype p53 is to cause a delay in cell cycle progression that 
allows for the repair of damaged DNA. If p53 is nonfunctional, the cell will continue to 
divide and DNA damage will accumulate. Introduction of wildtype p53 into cells 
damaged by irradiation induces apoptosis (programmed cell death). A similar 
mechanism might be operative as a result of excessive cisplatin DNA damage. Cisplatin 
is a DNA crosslinking agent. 
In response to the reviewers comments regarding the Informed Consent document. Dr. 
Roth explained that suggestions have been incorporated to the extent allowed by the 
IRB. Paragraphs 10 and 11 regarding the compensation for research-related injuries and 
medical costs including expensive tests or procedures cannot be changed or removed at 
this time. He stated that he will work with the other MD Amderson investigators and the 
IRB on this issue. 
Dr. Roth explained that resectable tumors will be removed surgically. However, due to 
invasion of vascular and bronchial structures, not all tumors confined to a local region 
are surgically resectable. These non-resectable areas, as well as recurrences and isolated 
metastasis, can be injected by a computed tomography (CT) guided needle. Tumors are 
usually soft and easily injected. Dr. Roth presented a slide demonstrating the spread of 
the injected material throughout the tumor mass as indicated by the lacZ marker. 
Distribution of the vector to the peripheral blood circulation is limited. 
Dr. Roth addressed the safety features of the proposed vector construct. The 
cytomegalovirus (CMV) promoter, which expresses p53, is susceptible to inactivation. 
Therefore, p53 expression is transient, and the p53 protein is no longer detectable 15 
days following transduction. If there is any mutation in the p53 gene, the mutant protein 
would be expressed only for a short time. 
Dr. Saha asked if the investigator is capable of detecting a virus with the mutant p53 
gene. Dr. Roth presented data from a spiking experiment in which a transforming 
Abelson leukemia virus was mixed with 1 x 10^° adeno-p53 virus particles. Foci 
formation was not observed upon infection of NIH3T3 cells. Dr. Miller commented that 
Abelson virus is a retrovirus, not an adenovirus. 
Dr. Roth presented diffusion experiments using the lacZ marker gene. Following a 
single injection, the vector was distributed to over 60% of the tumor cells as estimated 
by a planimetric measurement. With the bystander effect of the tumor killing activity of 
the transduced cells, most cells in the tumor mass will be treated. He presented data 
from the orthotopic lung cancer model to verify that this is a highly reproducible system. 
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Recombinant DNA Research, Volume 19 
