Cancer Therapy Vol 1, 299-314, 2003.
Dendritic cell based vaccines for
immunotherapy of cancer
Asim Saha, Sunil K. Chatterjee, Kartik Mohanty,
Kenneth A. Foon1, Malaya Bhattacharya-Chatterjee*
Department of Internal Medicine and the Barrett Cancer
Center, University of Cincinnati, Ohio 45267
1University of Pittsburgh Cancer Institute,
Pittsburgh, PA 15232
__________________________________________________________________________________
*Correspondence: Malaya Bhattacharya-Chatterjee, PhD, The Vontz Center
for Molecular Studies, Room 1316, University of Cincinnati, 3125 Eden Avenue,
Cincinnati, OH 45267-0509. Tel: (513) 558-0425; Fax: (513) 558-1096; e-mail:
malaya.chatterjee@uc.edu
Key Words: vaccines, dendritic cells,
cancer, immunotherapy
Abbreviations: Dendritic
cells (DCs); antigen presenting cells (APCs); ELISA method (ELISPOT);
Carcinoembryonic antigen (CEA)
Summary
Researchers and clinicians have tried for decades
to use specific and non-specific immunotherapy for the fight against cancer.
Initial attempts were based on soluble immune mediators such as antibodies or
cytotoxic proteins for the therapy of malignancies. Major improvements in our
understanding of the induction and regulation of cellular immunity have now
made it possible to generate effector cells in cancer patients that can
specifically recognize and destroy malignant cells. Human tumors express a number
of protein antigens that can be recognized by T cells, thus providing potential
targets for cancer immunotherapy. Tumor antigens have to be presented to T
cells in order to activate them and drive them into clonal expansion. This is
done by antigen presenting cells (APCs). Dendritic cells (DCs) are professional
APCs, which have an extraordinary capacity to stimulate na•ve T cells and
initiate primary immune responses. This established function of DCs has now
offered the hope to apply DC-based immunotherapy for cancers. Pilot clinical
trials of DC vaccination have established the safety and feasibility of this
approach and have produced encouraging evidence of therapeutic efficacy.
Importantly, significant advances in our understanding of the DC biology can be
used to support the design of new vaccines in order to elicit effective
cellular immune responses for the treatment of cancer. In this review, recent
findings of DC immunotherapy for a variety of tumors including colon cancer
have been discussed. Also, the development of DC-based vaccines in preclinical
models of colorectal cancer as a prelude to clinical trials has been
summarized.
Colorectal
cancer is one of the most common malignancies in men and women representing 10%
of all cancer deaths in the United States with ~ 130,000 new cases diagnosed
annually (Landis et al, 1998). Progression of the disease occurs through
invasion of the colonic wall, involvement of regional lymph nodes, and distant
metastasis. At the time of diagnosis, almost 50% of the patients have tumors
invading through the bowel wall with spread to regional lymph nodes; in
addition, 10% of the patients present with synchronous metastatic cancer to the
liver. There have been important advances in our understanding of the biology
and genetics of this disease, and if diagnosed early, colorectal cancer is
curable. Surgery is associated with a 90% five-year survival rate in patients
with tumors involving only the mucosa or submucosa. However, for majority of
the patients having metastasis of the disease in local lymph nodes and adjacent
organs, survival is substantially worse (Greenlee et al, 2000). Systemic
chemotherapy with 5-flurouracil-based regimens or newer agents such as
irinotecan has improved survival of these patients with high-risk disease
(Moore and Haller, 1999). Despite this, only 60% of all patients diagnosed with
colorectal cancer survive more than ten years. At present there is no
therapeutic regime capable of curing unresectable metastatic disease. Clearly,
more effective treatments are necessary for this disease.
Vaccines against infectious diseases are the success
story of immunology. Smallpox has been eradicated and vaccination strategies
have saved countless people from tetanus, polio, measles and hepatitis.
Consequently, there is a hope for the generation of effective cancer
vaccine(s). However, to date, human anti-tumor vaccination has not delivered on
its promises. Reasons for failure include tumor immune escape mechanisms,
limited availability of tumor specific antigens, as well as failure to deliver
tumor antigens in the right immunological context. Progress in immunology and
molecular biology has provided technologies to detect an ever increasing choice
of new tumor specific antigens. One of the most important issues is to deliver
these tumor antigens in an effective way to induce immune responses in cancer
patients. However, recent insights into the role of DCs as the pivotal APCs
that initiate immune response may provide the basis for generating more
effective antitumor immune responses in patients. Our understanding of the DC
biology has opened new ways for the application of these cells for
immunotherapy of cancer.
Immunotherapy is an attractive approach to cancer
therapy. The aim of immunotherapy is to induce or increase the ability of the
host to mount antitumor immune responses in vivo. Convincing evidence now exists that the effector cells of the immune
system (T, B, and NK cells), when appropriately activated, are able to lyse
tumor cells through specific recognition of tumor associated antigens (TAAs)
(Rosenberg, 1996; Finn and Lotze, 1998). Although a variety of both humoral and
cellular antitumor immune responses have been documented, T cells, and in
particular CD8+ cytotoxic T lymphocytes, are likely to play an
important role in antitumor immunity (Maeurer and Lotze, 1997). Identification
of TAAs together with a better understanding of the mechanisms involved in the
immune response against cancer, have given investigators tools to manipulate the
immune system to induce an efficient immune response in the tumor bearing host
(Pardoll, 2000; Van Gool et al, 2000; Borrello and Sotomayor, 2002; Drake and
Pardoll, 2002).
DCs were originally discovered as antigen presenting
cells critical for the induction of primary T cell dependent immune responses
(Steinman, 1991). DCs represent only 0.5% of blood leukocytes. Like other cell
types within the immune system, they arise from a common CD34+
progenitor in the bone marrow whose expansion and differentiation is influenced
by a variety of cytokine growth factors including stem cell factor, fetal liver
tyrosine kinase-3 (Flt-3) ligand, IL-3, granulocyte/macrophage colony
stimulating factor (GM-CSF), TNF-a and TGF-b (Shortman and Caux, 1997; Pulendran et al, 2001).
Mature DCs have a distinct morphology characterized by the presence of numerous
membrane processes that can take the form of dendrites, pseudopods, or veils.
Morphologic features of DCs include high concentrations of intracellular
structures related to antigen processing such as endosomes, lysosomes, and the
Birbeck granules of Langerhans cells of the epidermis.
DCs are also characterized by abundant expression of
molecules used for their specialized interactions with T cells. These include
the antigen-presentation molecules CD1 and the class I and class II MHC
proteins, the adhesion molecules CD11a (LFA-1a), CD11b, CD11c, CD50 (ICAM-2), CD54 (ICAM-1), CD58
(LFA-3), and CD102 (ICAM-3), although all of these markers can also be found on
monocytes and macrophages (Hart and Prickett, 1993). Costimulatory molecules
such as CD80 (B7.1) and CD86 (B7.2), and molecules regulating costimulation
such as CD40 are also expressed on mature myeloid DCs. DCs do not express
surface differentiation antigens found on B cells (CD19, CD20), T cells (CD3),
monocytes (CD14), and natural killer cells (CD56). Several antibodies have been
described that preferentially but not exclusively stain mature DCs. Antibodies
reactive against human DCs include anti-CD83 and CMRF-44 (Zhou et al, 1992; Hock et al, 1994).
Antibodies directed at mouse DCs include 33D1, N418 (anti-CD11c), and DEC-205
(Kraal et al, 1986; Metlay et al, 1990).
DCs originate from the bone marrow and their
precursors home via the bloodstream to almost all organs, where they can be
found as sentinels in an immature state with high endocytic and phagocytic
capacity. The current view is that these immature interstitial DCs are the
precursors of the mature interdigitating DCs found in the T cell rich area of
secondary lymphoid organs. Upon contact with bacterial DNA, LPS, dsRNA, and
inflammatory cytokines such as TNF-a or IL-1 the interstitial DCs change their phenotype
and function and migrate to the germinal centers of regional lymph nodes, where
they present antigens captured in the periphery to resting or na•ve T cells and
induce antigen-specific T cell responses.
With DC activation and migration from the tissue,
antigen uptake activity and the associated antigen receptors are down regulated,
resulting in a switch in APC function from antigen uptake to antigen
presentation (Hart and McKenzie, 1988). DCs are capable of processing antigen
via classical pathways: endogenous antigens via the proteasome into the MHC
class I compartment, and exogenous antigens via endocytic lysosomes into the
MHC class II compartment (Lanzavecchia, 1996). DCs also process alternative
pathways of antigen processing and can route exogenous antigen into the MHC
class I pathway through a mechanism known as cross-priming (Norbury et al,
1997). DCs may also utilize molecular chaperones such as heat shock proteins
(hsp96) to deliver antigens via the class I pathway (Arnold-Schild et al,
1999).
The family of human DC displays considerable
heterogeneity and plasticity at the level of phenotype and function (Banchereau
et al, 2000). DC may be derived from two potential lineages: myeloid or
lymphoid. Myeloid progenitors give rise to two main precursors: CD14+
CD11c+ precursors and CD14- CD11c+ precursors (Caux et al,
1996). CD14+ CD11c+ cells differentiate in the presence
of IL-4 and GM-CSF into interstitial DCs that correspond to dermal DCs in
vivo (Grassi et al, 1998).
In the presence of M-CSF, CD14+ CD11c+ precursor cells
acquire characteristics of macrophages. CD11c+ DCs may be also
reverted to macrophages under the same conditions. CD14- CD11c+ precursors yield DC of
the Langerhans cell type in response to GM-CSF, IL-4 and TGF-b. Immature
dermal or Langerhans type DC correspond to tissue resident sentinels in
peripheral tissue sites. Upon encounter of T cell derived signals such as CD40L
or microbial products such as LPS, they might be further driven along their
differentiation pathway to mature DC. Mature DC resides in T cell areas of
lymph nodes and marginal zone of spleen with stable phenotype and function. A
third major subset of DC are CD14- CD11c- IL-3Ra+ DC precursors (Grouard et al,
1997). These cells depend on IL-3 as survival factor and may be matured through
CD40 signaling. Further surface markers include CD45RA and ILT-3 (Cella et al,
1999). They display low phagocytic activity and are the major source of IFN-a production in
response to viral infection (Siegal et al, 1999).
III. What is the role of dendritic cell for the
induction of tumor immunity?
Effector mechanisms
against endogenous tumors include both cellular and humoral immunity. The
majority of experimental systems clearly demonstrate that tumor immunity is
largely provided by CD4+ T lymphocytes (Hung et al, 1998; Dembic et
al, 2000; Qin and Blankenstein, 2000), CD8+ T lymphocytes (Celluzzi
et al, 1996; Jenne et al, 2000; Terheyden et al, 2000) or NK cells (Fernandez
et al, 1999). T cells, and possibly also NK cells, however, require activation
by APCs, and in this context DCs are pivotal for this process. To activate
na•ve T cells, DCs take up, process and present antigen by their MHC molecules
(Banchereau and Steinman, 1998). In addition, T cell activation requires
engagement of co-stimulatory receptors on the T cell, adequate types and
concentrations of T cell activating cytokines and T cell attracting chemokines,
and maintenance of the activation signal over a sufficient period of time.
Currently, the list of family of co-stimulatory molecules is increasing
dramatically, and it appears likely that DCs can minutely control the outcome
of immune activation by means of differential surface receptor expression
(Coyle and Gutierrez-Ramos, 2001), and that T cells in turn signal back to
modulate the function of DCs (Bennett et al, 1998; Ridge et al, 1998; Schoenberger
et al, 1998). Activation of NK cells and of macrophages is less well
understood, but an interaction between DCs and these cell types has been
demonstrated (Fernandez et al, 1999). Apart from generating a powerful
antitumor immune response, DCs may also play an active role in the eradication
of tumors themselves, since DCs have been shown to kill tumor cells via
expression of death receptor ligands (Fanger et al, 1999), and recent data
suggest that DCs activated by pro-inflammatory cytokines or LPS can directly
inhibit the growth of tumor cell lines (Chapoval et al, 2000). Thus DCs are at
the very center of a developing tumor-specific immune response, and are
involved both in the initiation of tumor-specific immunity and the generation
of immune effector functions.
Promising results obtained in a variety of murine tumor models using DCs presenting tumor antigens as well as the identification of a growing number of T cell epitopes presented by human malignant cells prompted the rationale for evaluating the efficacy of DC-based vaccines in clinical studies.
IV. Generation of dendritic cells for cancer immunotherapy
Clinical trials of DC vaccination
have been made possible by the development of methods for obtaining large
numbers of human DCs. Three general approaches have been exploited for use in
clinical trials (Table 1). Myeloid DCs can be directly purified from blood by
density-gradient centrifugation procedures (Hsu et al, 1996). The systemic
administration of Flt-3
ligand or G-CSF increases blood DC numbers several fold (Maraskovsky et al,
2000; Pulendran et al, 2000). Alternatively, DCs can be prepared from CD14+
blood monocytes by in vitro culture with GM-CSF and IL-4 for 5-7 days, and
differentiation with maturation stimuli (Bender et al, 1996; Romani et al,
1996). Maturation is essential to prevent reversion to monocytes. Autologous
monocyte conditioned medium (MCM), CD40L or a cocktail of TNF-a, IL-1b, IL-6 and PGE-2 are available for
the maturation of DCs (Reddy et al, 1997; Thurner et al, 1999). CD34+
hematopoietic progenitor cells obtained from bone marrow, umbilical cord blood
or peripheral blood following treatment with GM-CSF or G-CSF are also source of
DC precursors. Following culture in GM-CSF and TNF-a (Caux et al, 1997), and stem cell
factor or Flt-3 ligand, a mixed population of immature DCs with characteristics
of both Langerhans cells and interstitial DCs has been obtained. Comparative
studies will be required to establish differences between these various sources
of DCs.
Apart from choosing the
right source of DC, critical issues for successful vaccination involve choice
of antigen, antigen loading, route and schedule of administration, as well as
immuno-monitoring.
The choice of DC is
likely to depend on the type of antigen used. The cellular machinery required
for processing antigen differs according to whether it is delivered as a
peptide, protein or genetic vaccine. Immature DCs, which are actively endocytic
and can internalize exogenous antigens efficiently, may be most suitable for
the delivery of protein or complex antigens that require processing by the DC.
In contrast, mature DCs, with higher expression of MHC molecules, may be more
suitable for peptide-based protocols. Strategies to enhance DC function
genetically to improve vaccine delivery and the subsequent induction of a
powerful immune response are also being evaluated. These include genetic
manipulation of DC to express cytokines or immuno-stimulatory molecules that can
potentiate DC-T-cell interactions (Philip et al, 1998).
Wide range of antigenic
preparations are available for loading of DC (Table 2). Peptide antigens are
well defined antigenic epitopes binding to a defined set of MHC molecules, and
easily accessible for immuno-monitoring of a peptide specific T cell response.
However, peptide approaches are limited by the requirement of analysis of the
MHC background of patients and the
Table 1. DC types available for clinical studies
Peripheral
blood DC populations
Directly isolated from
blood or expanded in vivo by
growth factors, such as Flt-3 ligand or G-CSF DCs derived
from CD14+ monocytes
Monocytes enriched by
anti-CD14 immunomagnetic beads or by plastic adherence DCs derived
from CD34+ hematopoietic progenitors
From bone marrow,
peripheral blood or cord blood |
knowledge of the sequence of the
relevant peptide epitope. The use of whole protein antigens, DNA, RNA or
recombinant viruses encoding the antigen of choice allows host HLA molecules to
select the appropriate peptide epitope for presentation as peptide-MHC complex
on the cell surface. This approach does not require analysis of MHC molecules,
although we have to be aware of the fact that spectrum of epitopes seen by
effector T cells might be restricted, since certain peptides are not presented
by DC due to incomplete processing at the level of the proteasome (Morel et al,
2000). Recently, other approaches have been applied to use the entire antigenic
content of a tumor cell for vaccination to present as many tumor antigens as
possible to the immune system and minimize the occurrence of immune escape
variants. This might be achieved by either pulsing DCs with whole tumor cell
lysate (Ashley et al, 1997), tumor derived RNA (Nair et al, 1998), DNA (Philip
et al, 1998) or fusion of tumor cells and DCs (Hart and Colaco, 1997). This
technique does not require the definition of the TAA or MHC haplotype of the
patients and has the potential for broad clinical application. The limitation
of this approach is the availability of tissue serving as a source of tumor
lysate or tumor derived RNA. A major disadvantage in using whole tumor in the
form of lysates, RNA or DC-tumor fusions is that monitoring effector cells
functions in vitro and in vivo is difficult to achieve.
After pulsing with tumor
antigen, DCs need to be administered in an effective way to the cancer
patients. Subcutaneous, intradermal, intravenous and intranodal approaches to
deliver DCs have been evaluated clinically. The intranodal approach (Nestle et
al, 1998) bypasses the requirement for vaccine-loaded DCs to migrate to
lymphoid tissue and simply relies on their capacity to express effective T cell
stimulatory capacity. The intravenous route results in the accumulation of DCs
to lung, liver, spleen and bone marrow, but not the lymph nodes or tumor sites
(Morse et al, 1999). In contrast, studies using intradermal injection of
monocyte derived DCs have demonstrated direct migration of DCs to the draining
lymph nodes. However, these particular studies used immature DCs, and only ~1%
of DCs migrated to the regional lymph node, the majority remained at the
injection site (Thomas et al, 1999). In contrast, monocyte-derived DCs matured in
vitro
have shown impressive immune responses (Schuler-Thurner et al, 2000). It is
unclear whether this effect was due to efficient migration and
antigen-presentation induced by in vitro activation of DCs.
Detection of an antigen specific
immune response is an important surrogate marker to control for an effective
vaccination strategy even though correlation with clinical response will be the
most important issue. The classic way to detect CTL activity is measurement of
lytic activity against 51Cr labeled target cells. Since precursor
frequencies are low, in vitro re-stimulations are often necessary in order to reach a CTL
frequency detectable by cytotoxicity assays. Although these techniques are time
consuming, still this method is the gold standard since it measures lytic
activity of effector cells.
Table
2. Delivery of antigens by dendritic
cells
|
Known tumor associated
antigens: Synthetic or eluted
peptides Recombinant or purified
protein Non-peptide antigens, such
as carbohydrates (e.g. MUC-1) or glycolipids (e.g. GM2) Transfection with cDNA or
RNA encoding known tumor-associated antigen Recombinant viruses
(adenoviruses, vaccinia, or retroviruses) Approaches when antigens
are unknown: Differentiation of DCs from
malignant cells (acute myelogenous leukemia, chronic myeloid leukemia) Tumor-DC fusions DC-derived exosomes Tumor RNA Apoptotic or necrotic tumor
cells Tumor lysates |
These
tests quantify antigen-specific T cells in the blood. It is unclear whether the
blood is the best place to look for evidence of emerging immunity against
vaccination, or whether the tumor site or draining lymph nodes may be more
appropriate. Recently introduced methods rely on measurement of release of
cytokines by CTL after contact with antigen (Romero et al, 1998). Cytokines may
be measured by an ELISA method (ELISPOT) or quantified by intracellular
cytokine staining and detection by flow cytometry. Detection of cytokine
release does not necessarily correlate with the cytolytic activity of a given
cell. Peptide-MHC tetrameric complex is another tool for detection of an
antigen specific immune response. However, this technique may not be able to
detect low or intermediate affinity T cells, which are important in the context
of vaccination against self-antigens. An additional method is delayed type
hypersensitivity (DTH) testing for peptide specific immune responses. Peptide
DTH testing was demonstrated in humans (Nestle et al, 1998) and this technique
is easy to perform even though objective read out might be a problem and is
observer dependent. DTH reactions are important since it measures induction of
an antigen specific immune response. It is therefore crucial to develop
appropriate immunological assays that may predict clinical responses more
closely.
Table 3. Published clinical trials conducted with DC-based
vaccines against cancer
|
Disease type |
Antigen |
DC type
|
Route
|
Investigator |
Melanoma
Lymphoma
Myeloma |
a) Melan-A, gp100, tyrosinase b) MAGE-1, MAGE-3, Melan-A,
gp100, tyrosinase c) MAGE-3 d) MAGE-1, MAGE-3, Melan-A, gp100, tyrosinase e) MART-1, gp100 f) Melan-A, MAGE-3, gp100, tyrosinase g) Tulys h) tumor cell-DC fusion i) Mart-127-35 peptide j) tumor cells k) acid-eluted peptides a) idiotype b) idiotype c) Tulys a) idiotype b) idiotype c) idiotype |
mDC mDC mDC CD34-DC mDC CD34-DC mDC mDC mDC mDC mDC PBDC PBDC mDC mDC PBDC CD34-DC |
i.v. intranodal s.c., i.v. i.v. i.v. s.c. i.d. s.c. i.v., or i.d. i.d. i.d. i.v., s.c. boost. i.v. s.c. boost intranodal i.v. i.v. s.c. boost s.c., s.c. boost |
Lotze MT et al (1997) Nestle FO et al (1998) Schuler- Thurner B et al (2000) Mackensen A et al (2000) Panelli MC et al (2000) Banchereau J et al (2001) Chang AE et al (2002) Krause SW et al (2002) Butterfield LH et al (2003) OŐRourke MGE et al (2003) Smithers M et al (2003) Hsu FJ et al (1996) Timmerman JM et al (2002) Maier T et al (2003) Lim SH et al (1999) Reichardt VL et al (1999) Titzer S et al (2000) |
|
Prostate RCC Liver Various Bladder CEA-expressing malignant Lung, colon Stomach, esophagus, colon
Colon |
a) PSMA b) Fusion protein (PAP+GM-CSF) c) Fusion protein (PAP+GM-CSF) d) PSM-P1, PSM-P2 e) rmPAP a) Tulys b) tumor cell-DC fusion c) Tulys d) Tulys e) tumor cell-DC fusion f) tumor RNA Tulys Tulys MAGE-3 CAP-1 (CEA peptide) 610D (CEA peptide) MAGE-3 CEA mRNA |
mDC PBDC PBDC mDC PBDC Allogeneic mDC Allogeneic mDC mDC mDC Allogeneic mDC mDC mDC mDC mDC mDC FL mobilized, density purified DC mDC mDC |
i.v. i.v., s.c. i.v. i.v. i.v., i.d., or intranodal i.v. s.c., s.c. boost i.d. s.c. i.d. i.v., i.d. intranodal i.d. s.c. i.v., i.d. i.v. i.v. i.v., i.d. |
Tjoa BA et al (1999) Burch PA et al (2000) Small EJ et al (2000) Lodge PA et al (2000) Fong L, Brockstedt D et al
(2001) Holtl L et al (1999) Kugler A et al (2000) Oosterwijk- Wakka JC et al (2002) Marten A et al (2002) Marten A et al (2003) Su Z et al (2003) Iwashita Y et al (2003) Geiger J et al (2001) Nishiyama T et al (2001) Morse MA et al (1999) Fong L et al (2001) Sadanaga N et al (2001) Morse MA et al (2003) |
__________________________________________________________________________________________________
mDC,
monocyte-derived DCs; CD34-DC, DCs derived from CD34-positive progenitors;
PBDC, peripheral blood-derived DCs; i.v. intravenous; s.c., subcutaneous; i.d.,
intradermal; MAGE, melanoma antigen; PSMA, prostate-specific membrane antigen;
PAP, prostatic acid phosphatase; PSM-P, prostate-specific membrane
antigen-derived peptide; rm, recombinant mouse; RCC, renal-cell carcinoma;
Tulys, tumor lysate; FL, Flt-3 ligand.
Numerous trials are currently ongoing or planned in
the very fast moving field of DC immunotherapy trials. We will only discuss
published trials in DC vaccination that includes malignant melanoma,
non-hodgkin lymphoma, multiple myeloma, prostate cancer, renal-cell carcinoma, liver
cancer, pediatric solid tumor, bladder cancer and colorectal cancer (Table 3).
A. Melanoma
Many immunologically
relevant melanoma antigens including differentiation antigens Melan-A, gp100,
and tyrosinase, as well as cancer-testis antigens, such as those of the
melanoma antigen (MAGE) family are currently being investigated in DC-based
clinical studies.
Lotze and co-workers
(Lotze et al, 1997; Lotze et al, 1998) used monocyte-derived DCs to treat
HLA-A2 positive patients with metastatic melanoma. DCs were pulsed with
peptides derived from Melan-A, gp100, or tyrosinase. Twenty-eight patients
received weekly intravenous and subcutaneous infusions of peptide-pulsed DCs
for four weeks. Two patients achieved a complete response and 1 patient
responded partially, although, one of the complete responders later developed
overt rheumatoid arthritis.
Nestle and colleagues
(Nestle et al, 1998; Nestle, 2000) used monocyte-derived DCs pulsed with MAGE-1
and MAGE-3 peptides (for patients expressing HLA-A1), Melan-A, gp100 and
tyrosinase peptides (for patients expressing HLA-A2), or MAGE-3 and tyrosinase
peptides (for patients expressing HLA-B44). Patients with metastatic melanoma
received weekly intranodal vaccinations for four weeks with a fifth injection
in week 6 and then patients had monthly injections for up to 10 months,
depending on clinical response. Vaccinations were well tolerated and 8 of 30
patients had clinical responses, with 3 complete and 5 partial remissions.
Thurner and colleagues
(Thurner et al, 1999) used monocyte-derived DCs pulsed with MAGE-3 peptides to
treat HLA-A1 positive patients with metastatic melanoma. Five vaccinations
(three subcutaneous followed by two intravenous) were given on every 2 weeks.
Six of 11 patients had mixed responses. Eight patients showed an increase in
MAGE-3-specific CTL responses. A follow-up study (Schuler-Thurner et al, 2000)
involving 12 patients with stage IV melanoma used the same procedure as
described by Thurner and colleagues. Three to five vaccinations with mature,
monocyte derived DCs loaded with HLA-A2 restricted peptides for MAGE-3 and for
influenza matrix generated vigorous immune responses as detected by in vitro assays in all eight
vaccinated patients. However, no significant clinical responses were observed
after final vaccination. Four patients died early in the treatment period due
to disease progression. Only 1 patient had stable disease, but disease
progressed in all remaining patients.
Mackensen and colleagues
(Mackensen et al, 2000) did perform a phase I study in 14 patients with
advanced melanoma using CD34 derived DCs matured with TNF-a. DCs were pulsed with MAGE-1 and MAGE-3 peptides (for patients
expressing HLA-A1) or Melan-A, gp100 and tyrosinase peptides (for patients
expressing HLA-A2). Patients received at least four intravenous vaccinations,
biweekly. Patients with stable or responding disease continued to receive
vaccination every four weeks until disease progression. The vaccines were
tolerated. One patient had a mixed response and six patients had stable disease
for 3 to 8 months. Peptide-specific DTH response was observed in 4 patients and
expansion of peptide specific CTL response was observed in 1 patient. A similar
study was conducted (Banchereau et al, 2001) in 18 HLA-A*0201+ patients with stage
IV melanoma using CD34 derived DCs. Patients were immunized with DCs pulsed
with peptides derived from four melanoma antigens (MelAgs) Melan-A/MART-1,
tyrosinase, MAGE-3, and gp 100 subcutaneously every two weeks for a total of
four vaccinations. DC injections were well tolerated except for two patients.
DC vaccination resulted enhanced immunity to ³ 1 MelAgs in 16 of 18
patients. Ten of 14 evaluated patients developed DTH to at least one peptide
after repeated DC vaccination. The development of T cell response to multiple
tumor antigens on peptide-pulsed DCs in this study was associated with a
favorable early clinical outcome. Seven of 17 evaluable patients experienced
tumor progression. The remaining 10 patients did not progress at this time point
(10 weeks from study entry). Among these, four patients had regression of tumor
metastases at one or more disease sites and three patients cleared any evidence
of disease.
Recently, Butterfield and colleagues (Butterfield et al, 2003) have conducted a phase I study in 18 HLA-A*