01. Gene therapy Boulikas.pdf - Gene therapy & Molecular Biology

Figure 18. A clinical protocol for adoptive immunotherapy
of advanced melanoma patients. Adapted from Chang et al
(1996).
A number of RAC-approved human gene therapy
protocols use GM-CSF cDNA transfer. These are
protocols 35, 53, 63, 113, 149, 150, 162, and 181 in
Appendix 1.
I. Cancer immunotherapy with the IFN-γ
gene
Solid tumors in nude mice have been successfully
eradicated with treatment with tumor cell lines stably
transfected with an IFN gene. A number of human tumor
cell lines including 293, HeLa, K562, and Eskol (a
malignant immunoblastic lymphoma) were infected with a
rAAV carrying a synthetic type I interferon gene and the
bacterial neomycin-resistant gene and geneticin-resistant
cells were selected; when injected into nude mice, 293,
K562, and Eskol cells failed to form tumors for a duration
of up to 3 months; on the contrary, mice receiving
nontransduced cells developed tumors within 7 to 10 days;
in addition, treatment of an established Eskol tumor with
transduced 293 cells resulted in tumor regression (Zhang
et al, 1996).
Three RAC-approved human gene therapy protocols
use IFN-γ cDNA transfer. These are protocols 36, 54, and
71 in Appendix 1.
J. Immunotherapy with synthetic tumor
peptide vaccines
Progress in the identification of tumor-specific
antigens, that is proteins expressed at high levels by a
specific tumor cell type such as prostate or breast cancer,
most of which are surface glycoproteins easily
recognizable by the immune system, as well as the
Boulikas: An overview on gene therapy
50
deciphering of the mechanisms for enhancing the response
of cytotoxic T cell lymphocytes have advanced the
potential for developing cancer vaccines.
Cancer immunotherapies based on synthetic tumor
peptide vaccines have been developed. Tumor-specific
CD8 +
cytotoxic T lymphocytes (CTLs) recognize short
peptide epitopes presented by MHC class I molecules that
are expressed on the surface of cancer cells. Bone marrowderived
dendritic cells, grown in vitro in media containing
combinations of GM-CSF + IL-4, when pulsed with
synthetic tumor peptides (which are loaded on the surface
of the dendritic cells) became potent antigen-presenting
cells (APCs) capable of generating a protective antitumor
immune response. Injection of these cells into naive mice
protected the mice against a subsequent lethal tumor
challenge; in addition, treatment of mice bearing C3
sarcoma or 3LL lung carcinoma tumors with the same
type of cells resulted in sustained tumor regression in over
80% of the animals (Mayordomo et al, 1995).
One of the obstacles of this method has been the
difficulty in obtaining sufficient numbers of APCs;
dendritic APCs have been isolated from CD34 +
hematopoietic progenitor cells drawn from cord blood and
expanded in cell culture in the presence of GM-CSF and
TNF-α; TNF-α inhibits the differentiation of dendritic
cells into granulocytes. Human peripheral blood
mononuclear cells or mouse bone marrow cells depleted of
lymphocytes could also yield dendritic cells when cultured
in the presence of GM-CSF + IL-4 (Mayordomo et al,
1995).
K. DNA vaccines
Vaccines may be one of the first successful
applications of foreign genes into mammalian cells under
control of heterologous promoters and enhancers (Felgner
and Rhodes, 1991; Thompson, 1992; Gilboa and Smith,
1994). Vaccination with DNA has been shown to be a
promising approach for immunization against a variety of
infectious diseases (Wang et al, 1993; Michel et al, 1995;
Huygen et al, 1996; Kuhober et al, 1996). The method
consists in introducing the gene of a viral or bacterial
antigen which is uptaken and expressed by the host’s cells
to elicit an antigen-specific immune response. DNA
coding for an antigen can be directly injected into muscle
or skin and stimulate an immune response against the
expressed antigen; the gene can either code for surface
molecules, which are often used for conventional peptide
vaccines, or from internal microbial proteins.
During this approach the antigens are produced
intracellularly where they are correctly folded and can be
presented to the immune system to stimulate cytotoxic T
cells; the method is safe and simple and has shown
promising results on animals (reviewed by Moelling,
1997). For example, mice injected intramuscularly with an