Applications of Gene Therapy - Challenges in Delivery of Therapeutic Genomics and Proteomics - page 285

mutations were given cisplatin on day 1 and an escalating dose of Ad/p53 on day 4.
The biopsies results revealed increased tumor necrosis and apoptosis [105] .
6.3.3.3 Inactivation of Oncogenes
The use of vectors containing DNA fragments complementary to oncogenes and
antisense ODNs has been established in a number of cancers, including lung cancer.
In small cells lung carcinoma (SCLC), the various oncogenes that underwent altera-
tion are c-myc, L-myc, N-myc, c-raf, c-myb, c-erb B-1, c- fms , c- rlf , and in NSCLC the
altered genes are K-ras, N-ras, H-ras, c-myc, c-raf, c-fur, c-fes, c-erbB-1 (EGF-R),
c-erbB-2 (Her2, neu), c-sis , and blc-1 [106] . In SCLC cells, the antisense DNA to
L-myc results in the inhibition of cell proliferation under in vitro conditions [107] .
Similarly, when antisense ODN was incubated with L-myc gene overexpressed cell
line, the cells showed inhibition of growth. Moreover, in NSCLC delivery of c-myc
and K-ras antisense resulted in inhibition of cell proliferation in vitro [108,109] .
Introduction of vectors encoding oncoprotein-neutralizing antibody fragments is
another approach to achieve antisense-mediated oncogene inactivation. It was shown
that the introduction of an anti- ras single-chain antibody fragment could mediate
apoptosis in the ras -transformed lung carcinoma cell line H460 [110] . One potential
approach for lung caner involves the introduction of a gene that codes for a ribo-
zyme, which is an RNA that has catalytic activity and can cleave RNA of oncolytic
genes [111] . The K-ras ribozyme against human lung cancer cell line heterotrans-
plants in nude mice was shown to have antitumorigenic effect [112] .
6.3.3.4 Immunotherapy
A number of approaches have been developed for cancer immunotherapy, including
tumor-associated antigen-based vaccines; tumor cell vaccines genetically engineered to
secrete immunologically relevant cytokines; and costimulatory molecule gene-modified
tumor cell vaccines. The majority of NSCLCs (70%) express carcinoembryonic antigen
(CEA) on their surface [113] . Immunization using a recombinant vaccinia virus that
expressed the human CEA gene (rV/CEA) in animal models resulted in antitumoral
activity for CEA expressing cells [114] . Further, the immunogenicity and safety of this
vaccine had been checked in a nonhuman primate such as a monkey. All the vacci-
nated animals exhibited both cellular and humoral responses, with local skin reactions
[115] . A phase I clinical trial was designed to evaluate the combination of a recom-
binant CEA-vaccinia virus vaccine to prime an immune response, with a postvacci-
nation boost using CEA peptide mixed with an adjuvant in patients with NSCLC (in
addition to other malignancies) [116] . Another tumor-associated antigen is Fuc-GM1,
a ganglioside expressed by most small-cell lung cancers (SCLC), but not by most nor-
mal tissues. In a clinical trial, patients were vaccinated with Fuc-GM1 conjugated to
keyhole limpet hemocyanin (KLH). In all of these patients, anti-FucGm1, IgM, and
IgG antibodies were detectable in their serum. Furthermore, these antibodies were
capable of binding to tumor cells expressing Fuc-GM1 and were able to mediate com-
plement-dependent killing of tumor cells [117] . The other tumor-associated antigens
are NY-ESO-1 and human epithelial mucin MUC-1, expressed over the surface of