Dendritic cell vaccination in patients with Lynch Syndrome or colorectal cancer with MSI

Ex vivo generated and tumor-antigen-loaded dendritic cells (DC) are currently
used in clinical vaccination protocols in cancer patients. DC vaccines are
safe, with minimal side effects. Evaluating more than 200 patients treated the
past ten years we found that clinical responses measured in several patients
directly coincide with specific cytotoxic T cell responses. The majority of
studies investigated the therapeutic effects of DC vaccines in late-stage
cancer patients with metastasis. In these (heavily) pretreated patients the
immune system is compromised. Based on our observations that a specific immune
response is indicative for a good clinical outcome we believe that the full
potential of these immunostimulatory cells has to be exploited in high-risk
patients with low tumor burden or in a precancerous state.
A good clinical model are carriers of a germline mutation in one of the DNA
mismatch repair (MMR) genes, such as patients with Lynch syndrome (also known
as Hereditary Non-Polyposis Colorectal Cancer or HNPCC). These persons have a
lifetime risk of 60-80% for colorectal cancer that has developed within a few
years develops from a precancerous adenoma. The immune system is thought to be
of potential great importance as the colorectal cancer in Lynch syndrome is
characterized by a strong lymphocyte infiltration, even at he stage of
adenomas. In affected cancer lesions, MMR dysfunction results in frameshift
mutations at short, repetitive DNA sequences referred to as microsatellites. In
coding regions these mutations destroy gene function and have been demonstrated
to lead to the production of neopeptides [9]. These neopeptides are 1) tumor
specific, because frameshift mutations only occur in tumor cells and their
premalignant progenitors and 2) immunogenic, since cytotoxic T cells (CTL) and
helper T cells could be induced in vitro from blood of patients with Lynch
syndrome. Similar mechanisms occur in sporadic colon cancer with MMR
dysfunction, which represents about 10-15% of all colorectal cancers.

The primary objective is the safety and feasibility of CEA/frameshift derived
neopeptide loaded DC in patient with MSI-positive colorectal cancer and persons
who are known to be carrier of a germline MMR-gene mutation with no signs of
disease yet.
The secondary objectives of the study are to evaluate whether peptide-loaded DC
can induce or enhance an immune response to tumor-associated antigen CEA and
specific frameshift-derived neoantigens in the study population and the
pathological and or clinical responses, e.g. disease-free survival, determined
according to the standard protocol.

This study is an open label phase I/II study.

Treatment of subjects
Curative: MMR mutation carriers with CRC (group I)
MMR-gene mutation carriers with a carcinoma will be asked to participate in
this study. HLA-A2.1 positive CRC patients will be vaccinated 3 times every
week with DC loaded with CEA-derived and frameshift mutation-derived
neopeptides. All DC will be pulsed with KLH as an immune control. DC will be
simultaneously administered intradermally (i.d.) in the upper leg and
intravenously (i.v.) 10 and 20 x 106 cells, respectively. After the 3
vaccinations a DTH will be performed, from which biopsies will be taken for T
cell analysis. If no relapse occurs, we will repeat this cycle two more times
with a 6 months interval. Thereafter, patients will be scheduled for regular
follow-up and will receive surveillance colonoscopy every 1-2 years.
Preventative: MMR mutation carriers with no signs of disease (group II)
These healthy individuals will be treated with DC loaded with frameshift
mutation-derived neopeptides and with DC loaded with CEA, as described above
for group I, 5-6 weeks prior to the regularly scheduled surveillance
colonoscopy, with regular follow up and surveillance colonoscopy every 1-2
years. If no carcinomas are developed, we will repeat this cycle two more times
with a 6 months interval.

Based on our experience with peptide-pulsed DC, we expect that these DC will be
well tolerated. Common and expected side effects of DC vaccination are usually
mild and include flu-like symptoms and local reaction at injection site, both
common toxicity criteria (CTC) grade 1.
Patient material that will be requested during the study in addition to
standard procedures is summarized in the table below.

Day Event
Patient material
-21 to -28 Inclusion (HLA-typing, virus testing) 30 ml blood
-9 Apheresis
Mononuclear cells, 5 ml serum
0 DC vaccination I i.d./i.v. 1 skin biopsy
7 DC vaccination II i.d./i.v. 80 ml heparin
blood, 5 ml serum
14 DC vaccination III i.d./i.v. 80 ml heparin
blood, 5 ml serum
19 DTH 90
ml heparin blood, 5 ml serum
21 Biopsies of DTH lesions 4 + 1 (=control) skin
biopsies