Recombinant DNA Advisory Committee - 06/1-2/92 
the tissues tested. Dr. Culver said that the investigators will add a section outlining this 
data. 
Dr. Leventhal stated that a sentence should be included about the number of brain 
tumors that have been examined. Dr. Culver agreed to include this sentence. 
Dr. Krogstad reiterated his concerns about hypersensitivity of patients to these murine 
cells. Dr. Parkman stated that these concerns were not warranted. Dr. Leventhal stated 
that anaphylaxis could be treated if it occurs as a result of hypersensitivity; there is no 
method for predicting anaphylaxis in this case. 
Dr. Parkman referred the investigators to the section in the protocol that defines the 
injection sites of surgically inaccessible patients. The areas that would be excluded, e.g., 
the midbrain, are not listed as the investigators have indicated. Dr. Parkman stated that 
the areas of the brain excluded from treatment should be clearly defined. Dr. Leventhal 
suggested that an alternative statement regarding this issue would be that "patients in 
whom it is considered that necrosis of brain tumor would result in significant anatomic injury 
would be excluded from this protocol". Dr. Oldfield said that this statement could be 
added to the protocol. 
Dr. Murray asked if the tissues that were assayed were examined by p-galactosidase (p- 
gal) staining or by PCR. Dr. Oldfield replied that they had used p-gal staining. 
Dr. Culver addressed the issue of the bystander effect. Dr. Geiduschek asked if any 
effect was observed on neighboring cells as a result of producer cell injection into the 
brain and subsequent administration of ganciclovir. Dr. Culver responded that they have 
observed no in vivo bystander effect on normal cells in either rat or murine models. 
However, significant in vitro bystander effects have been observed on several tumor cell 
lines, e.g., human glioblastoma, melanoma, and the 205 mouse fibrosarcoma. This in 
vitro bystander effect is similar to the effect that has been observed in the in vivo rat 
gliosarcoma experiments. 
Dr. Culver described in vitro thymidine incorporation assays where transduced and non- 
transduced tumor cells were mixed and treated with ganciclovir following overnight 
culture. When the transduced cell fraction approached 50%, a decrease in cell 
proliferation was observed equivalent to tumor cell populations that were 100% 
transduced. 
Dr. Parkman was concerned about the interpretation of these thymidine incorporation 
experiments since these cells contained TK. Some of the cell lines which have been 
assayed could be grown in semi-solid agar. If the cells were treated with ganciclovir and 
then set up in a clonogenic assay, the investigators could observe the degree to which the 
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