Recombinant DNA Advisory Committee - 06/1-2/92 
Dr. Murray called on Dr. Gansbacher to respond to the questions presented by the 
primary and secondary reviewers. Dr. Gansbacher explained that experiments have 
demonstrated that melanoma tumor-associated antigens exist. Data suggest that HLA- 
A2 is the best antigen presenter. HLA-A2 is expressed in 30-40% of Caucasians. Other 
investigators have demonstrated that HeLa cells or T lymphocytes can be sensitized 
against peptides presented by HLA-A2, and that these peptides can be recognized on 
allogeneic cells. 
Dr. Gansbacher described one study in which an HLA-A2(-) melanoma cell line was 
transfected with the HLA-A2 gene, and that these cells were then capable of expressing 
a peptide recognized by HLA-A2 specific CTL. He detailed another study in which a 
gene has been identified, MAGE-1, that is expressed in melanoma antigens and some 
other tumors but not in normal cells. This MAGE-1 gene is found in a CTL defined 
epitope. He described another study in which the CTL precursor frequency in Stage III 
and IV patients was examined. The analysis demonstrated that melanoma patients 
exhibit a wide range of frequency of CTL precursors. 
Dr. Gansbacher stated that the information derived from these experiments is evidence 
for the validity of this protocol. An allogeneic HLA-A2( + ) melanoma cell line will be 
irradiated and used to immunize HLA-A2( + ) patients with Stage IV disease. 
Dr. Gansbacher noted that only the HLA-A2 haplotype was chosen because HLA-A2 
presents a peptide that is recognized by allogeneic HLA-A2 specific CTL clones; 
therefore, it is not necessary to match any other locus. He hypothesized that the 
allogeneic response will be very strong, eliciting an effector cell population that may 
contain appropriate T cell receptor rearrangement to react against weakly immunogenic 
tumor antigens. 
Dr. Kelley asked Dr. Gansbacher if he plans to re-immunize these patients or will one 
immunization probably be effective? Dr. Gansbacher responded that the patients will 
receive four vaccinations every two weeks. 
Dr. Kelley asked if patients reject their melanoma cells, is there also the possibility that 
they will reject normal melanocytes? Dr. Gansbacher responded to Dr. Kelley's previous 
question regarding the choice of the SK-MEL-29 melanoma cell line for the in vitro 
experiments. Dr. Gansbacher stated that SK-MEL-29 is the second most widely studied 
melanoma cell line that exists. This cell line has already been used in other patients 
using the same variables such as number of cells, irradiation, and administration of non- 
identical HLA types. Although no side effects were observed, there was no response to 
treatment. 
Dr. Gansbacher explained that Sk-MEL-29 expresses four melanocyte differentiation 
Recombinant DNA Research, Volume 15 
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