i) Combination of the LNL6 virus with other viruses or 
cellular nucleic acid which may lead to a replication competent 
vector which is autonomously replicating within the autologous 
cells. 
ii) Insertional mutagenesis or altered expression of genes 
which then become transforming for the autologous leukemic or 
normal progenitor cells either by virtue of altered levels of 
expression, altered functions, leading to a dominant transforming 
gene product, or due to the inactivation or suppression of an 
antioncogene. The LNL6 marking vector to be used in these 
experiments was the same vector approved for use in the Rosenberg 
N2-TIL clinical protocol previously approved for use in the human 
subjects by the NIH RAC Committee. Authorities agree that the 
safety modifications present within the LNL6 make the probability 
for a marking vector recombination event very low. Moreover, the 
sequences of the LNL6 are not homologous to human sequences. 
Importantly, the same LNL6 NEC virus was approved for use in 
human patients with leukemia (see Malcolm Brenner's AML program, 
approved 2/4/91) . Exposure to the LNL6 vector has been observed 
through 32 monkey years, 70 patient months, and 1500 mice 
equivalents. There has not yet a neoplastic condition (leukemia or 
solid tumor) produced by marking vector insertion. 
There is a potential theoretical difference between the 
experiment of Brenner with AML remission marrow and the CML chronic 
phase or cytogenetic remission marrow after blast crisis: the 
larger number of chronic phase Philadelphia chromosome positive 
cells present in the autologous cells which might lead to an 
increased risk of viral transformation. However, no data exists 
which suggest that CML cells are more susceptible to viral 
transformation than AML cells. The integration frequencies appear 
to be similar for chronic phase marrow (in our data) with that of 
Brenner. Clearly, in the current experiment, if a clonal insertion 
site is identified at relapse, the DNA surrounding this site should 
be characterized to establish if the insertion site of the vector 
in the leukemia was at a transforming gene or not. The probability 
of this occurring is regarded as very low on the basis of data thus 
far reported. 
3. CLINICAL PROCEDURES INCLUDING PATIENT MONITORING 
See clinical protocol document for a summary of patient 
monitoring (Appendix A) . The protocol is similar to one previously 
approved by Malcolm Brenner for AML. The only substantial 
difference is that both peripheral blood and marrow cells will be 
used for reconstitution. This modification is incorporated to 
increase the rate of hematopoietic recovery in the CML patients 
which is slower with marrow alone than that seen in the AML 
patients. 
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Recombinant DNA Research, Volume 14 
