Recombinant DNA Advisory Committee - 12/1-2/94 
expectancy. 
Dr. Frank Sturtz (Progenitor, Inc.) raised several concerns regarding the use of the wild-type p53 gene to treat 
cancer patients. The p53 gene was first recognized as an oncogene. Mutation of the CFTR gene render the 
gene nonfunctional. Mutation of the wild-type p53 gene at several "hot spots" can produce mutant p53 proteins 
that are very oncogenic. The proposed strategy has the potential for risk. If oncogenic mutations in the p53 
gene occur during vector preparation, both subjects and health care workers could be at possible risk. 
Dr. Miller inquired about the frequency of transforming p53 mutations in the adenovirus vector preparations. 
Dr. Sturtz responded that he was not knowledgeable about the frequency of such mutations. However, 
introducing a mutant p53 gene can transform an astrocytoma to a higher grade malignant tumor. Dr. Miller 
said that adenovirus vector stocks should be screened for such mutations. Dr. Saha said that 50% of human 
cancers have p53 mutations at several "hot spots," and that he is not aware of any assays available to detect 
such mutations in adenovirus vector stocks. Dr. Glorioso noted that the frequency of stable human 
transformation with this vector is extremely low since two separate low frequency events are required for 
transformation to occur, i.e., oncogenic mutation of the p53 gene and integration of adenovirus sequences. Dr. 
Sam uls ki agreed that adenovirus sequences do not normally integrate into host cell chromosomes. However, 
high level expression could interfere with the cell cycle and move the cell along a hyperplastic pathway. 
Between 4 and 5 p53 mutation "hot spots" have been identified; therefore, a PCR assay could be developed to 
detect such mutations in the virus stocks. 
Dr. Haselkom said that the RAC should focus its discussion on the two significant issues: (1) development of 
an assay to identify the potentially oncogenic viruses, and (2) duration of p53 expression in both normal and 
tumor cells. The period of p53 expression will determine the degree of risk that a p53 mutant poses to normal 
cells. Dr. Glorioso said that HSV has a mutation frequency of 1 in 1 x 10 6 per cell cycle; therefore, a 1 x lO 10 
pfu virus stock would have an enormous number of mutations. Dr. SamuLski added that p53 mutations will 
accumulate since this gene is nonfunctional. An experiment should be conducted involving the transduction of 
normal cells with a mutant p53 construct to determine the effect of high level expression. 
Dr. Walters asked the reviewers to clarify what are the principal differences between the present protocol for 
squamous cell carcinoma of head and neck and Dr. Roth’s non-small cell lung cancer protocol that was 
reviewed by the RAC at the June 1994 meeting (Protocol #9406-079). Dr. Smith stated that these same safety 
issues were raised during the review of Dr. Roth’s protocol. Bronchoscopic delivery of Ad2CMV-p53 to the 
lung (Dr. Roth’s protocol) could present a higher degree of risk than this direct injection head and neck tumor 
study. Dr. Roth’s protocol includes a greater possibility of horizontal transmission due to aerosol distribution 
of the vector. Dr. Saha expressed serious concern about the possibility of oncogenic p53 mutations in Dr. 
Roth’s previously reviewed protocol. Dr. Walters noted that Dr. Roth’s protocol was approved by the RAC 
contingent on the review and approval of additional safety data. The NIH Director has not yet approved Dr. 
Roth’s study. 
Dr. DeLeon asked the investigators to address the issue of p53 overexpression in normal cells. Dr. Saha 
suggested Dr. Arnold Levine of Princeton University should be invited as an ad hoc consultant to address p53 
issues. Dr. Ross asked if there is any concern about the present protocol that is not pertinent to Dr. Roth’s 
study. Dr. Smith noted that Dr. Roth’s contingencies were: (1) intra-pleural administration of the adenovirus 
vector will be eliminated from the protocol; therefore, a revised protocol and Informed Consent document are 
required; (2) the protocol will be revised to include patient sputum titration assays on 293 cells (for both wild- 
type and mutant vector) to be conducted until virus is no longer detectable (patients will be isolated for a 
period of 1 week). The RAC did not address the safety issues raised during this discussion as part of Dr. 
Roth’s contingencies for approval Dr. Secundy noted the necessity for adequate autopsy data for this 
protocoL Dr. Samulski said that most of the safety concerns could have been avoided if the adenovirus vector 
had been constructed differently, Le., include a promoter that preferentially expresses p53 in tumor cells and 
not in normal cells. 
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Recombinant DNA Research, Volume 20 
