An exploratory study: Dendritic cells for immunotherapy of metastatic endometrial cancer patients

Dendritic cell vaccination
Prevention of infectious diseases through immunization is one of the greatest
achievements of modern medicine. Nonetheless, considerable challenges remain
for improving the efficacy of existing vaccines for therapeutic immunizations
for diseases such as cancer. We were amongst the first groups worldwide that
introduced tumor antigen-loaded dendritic cell (DC)-based vaccines in the
clinic1-3. Effective immune responses and favorable clinical outcomes have
indeed been observed4-7. Thus far, mainly conventional in vitro generated
monocyte-derived DCs (moDC) have been used in clinical trials worldwide. In the
past 14 years we have treated more than 375 patients and proven that DC therapy
is feasible and non-toxic. We observed that long lasting tumor specific T
cell-mediated immunological responses are clearly linked to increased
progression free survival as well as overall survival8.
However, moDC may not be the optimal source of DCs for DC vaccination studies,
due to extensive culture periods and compounds required to obtain mature moDC.
Peripheral blood-derived DC (plasmacytoid dendritic cells (pDC) and myeloid
dendritic cells (myDC)) are possibly a better alternative since they do not
require extensive culture periods. We recently completed a clinical trial in
stage IV melanoma patients using plasmacytoid pDC. The results on both
immunological outcome as well as clinical outcome are promising. These freshly
isolated natural pDC prolonged median overall survival to 22 months in
comparison to 7.6 months in matched historical melanoma patients who had
received standard chemotherapy9. In patients receiving moDC-vaccinations, we
did not observe such a clear increase in overall survival, suggesting that
pDC-vaccines may induce even more potent anti-tumor responses than
moDC-vaccines. In terms of immunological outcome transcription of both
interferon-alpha (IFN-*) and interferon-beta (IFN-*) genes was clearly induced
4 hours after vaccination and decreased 20 hours later. An IFN gene signature
is known to be highly important for eradication of viruses. This signature is
indicative for a temporal systemic induction of type I IFNs. Type I IFN might
also stimulate myDC and enhance their ability to cross-prime CD8+ T cells,
thereby inducing more efficient anti-tumor T cell responses when compared with
in vitro generated DC. This is supported by studies in mice: type I IFN were
critical for the induction of anti-tumor immune responses10,11. In the 14 stage
IV melanoma patients included in our myDC trial we observed already in 3
patients highly functional tumour-specific T-cells in peripheral blood and in
DTH sites coinciding with tumour regression12. For comparison: in our trials
with monocyte-derived DC, less bonafide T cell responses were seen after DC
vaccination, suggesting that blood myDC induce more potent immune responses
compared to monocyte-derived DC.
In conclusion, based on all these observations we are convinced that pDC and
myDC employ different, and probably more optimal mechanisms to combat cancer.
In addition, based on in vitro data and preclinical studies that suggest that
blood pDC and myDC act synergistically, we hypothesize that the combination of
myDC and pDC may induce stronger anti-tumor immune responses as compared to pDC
or myDC alone, or moDC.

Immunotherapy in endometrial cancer
Endometrial cancer is the only gynaecologic malignancy with a rising incidence
and mortality. While cure is routinely achieved with surgery alone or in
combination with adjuvant pelvic radiotherapy when disease is confined to the
uterus, patients with metastatic or recurrent disease exhibit limited response
rates to cytotoxic chemotherapy, targeted agents, or hormonal therapy. Some
figures: at the time of diagnosis, 67% of women have disease confined to the
uterus and an associated 5-year survival rate of 95%. In contrast, the 8% of
patients with distant metastases at the time of diagnosis have a 5-year
survival rate of 17% and face the prospect of cytotoxic chemotherapy (primarily
with taxanes, platinum and anthracyclines).
Given the unmet clinical need in this patient population, exploration of novel
therapeutic approaches is warranted, and attention is turning to
immunomodulation. Existing evidence suggests that endometrial cancer is
sufficiently immunogenic to be a reasonable candidate for immunotherapy.

Dendritic cell vaccination after chemotherapy
Tumors exploit several mechanisms to suppress anti-tumor immune responses,
including the recruitment of suppressive cells, such as myeloid-derived
suppressor cells (MDSCs), into the tumor microenvironment13. The presence of
MDSCs in the suppressive tumor microenvironment is correlated with decreased
efficacy of several immunotherapies, including DC vaccination and
ipilimumab14,15. Data obtained in our lab indicates that MDSCs can be targeted
with platinum-based chemotherapeutics. In head-and-neck squamous cell carcinoma
patients treated with six weekly dosages of cisplatin, the frequency as well as
suppressive capacity of MDSCs were significantly inhibited two weeks after the
last dose. Treating the patients with DC vaccination after six cycles of
chemotherapy with carboplatin, might therefore have a positive impact on the
clinical outcome of DC vaccination.

Antigen loading of dendritic cells
To be effective as an antigen-presenting cell, the MHC molecules of a DC must
be loaded with antigenic cargo. In this study, DC will be loaded with
well-defined common tumor antigens in the form of long peptides of two tumor
associated antigens frequently shared by endometrial cancer, survivin and MUC1.

The primary objective of this exploratory study is to show immunologic efficacy
of tumor-peptide and tumor lysate-loaded natural DC in mEC patients undergoing
chemotherapy. The immune-monitoring will include: a) functional response and
dextramer analysis of DTH infiltrating lymphocytes against tumor peptides, b)
type I IFN gene expression in PBMC shortly after vaccination, and c)
proliferative, effector cytokine- and humoral responses to keyhole limpet
hemocyanin (KLH), an immunogenic protein providing T cell help.

The secondary objectives are the safety, feasibility and quality of life of
natural DC vaccinations in combination with chemotherapy.

This study is a single arm exploratory, single-centre study.

Our study population consists of 8 mEC patients who receive chemotherapy with
carboplatin and paclitaxel in a weekly schedule on week 1, 2, 3 and week 5, 6
and 717. In week 8, myeloid and plasmacytoid DC (nDC) loaded with tumor lysate
and survivin and NY-ESO PepTivators will be injected intranodally. In all
patients, extensive immunomonitoring will be performed. Patients who
demonstrate stable disease, partial response or complete response continue with
extended three-weekly chemotherapy17 with intranodal injection of nDC in week
17, 20 and 23.

Based on the experience with nDC inoculations in melanoma patients, we expect
that the nDC will be well tolerated by mEC patients. More common and expected
side effects of nDC vaccination are usually mild and include flu-like symptoms
and local reaction at injection site, both not greater than Common Terminology
Criteria for Adverse Events (CTCAE) grade 1. The side effects are completely
reversible within 24-48 hours. Because of this the risk classification in
relation to the chance of adverse events and the severity of the expected
adverse events is defined as being negligible.
Weekly carboplatin paclitaxel is an effective used schedule in endometrial
cancer17. Side effects of weekly carboplatin paclitaxel are bone marrow
toxicity, with resulting granulocytopenia, decreased platelets and anaemia,
nausea, vomiting, diarrhea and constipation and neuropathy.