The function and composition of B cells in patients with Glioblastoma treated with and without Dexamethasone

Glioblastoma is the most frequent and aggressive form of brain cancer and has a
poor prognosis with a life expectancy of 15-17 months due to its rapid and
invasive growth. The current standard of care (Stupp protocol); (Stupp et al.,
2005) was introduced in 2005 and consist of surgery followed by
chemo-radiotherapy (temozolomide) but has only added approximately 3 months to
the total life expectancy of patients with glioblastoma. Yet, in all patients
the tumor recurs and second line treatment strategies have a very low response
rate (less than 20%) with usually a short duration
Currently, there is great interest in targeting the immune system to promote
antitumor response as a new means of treating cancers, including glioblastoma.
Despite the presence of potential antitumor effector cells within the
microenvironment, the growth of glioblastomas persist (Li et al., 2016). A
possible explanation for the lack of effective antitumor immune response is the
presence of an immunosuppressive microenvironment (Raychaudhuri et al., 2011).
This is likely due to a number of factors, including immune checkpoint
signaling, T cell exhaustion, glucose depletion, hypoxia, and the presence of
immunosuppressive cells, such as regulatory T cells, tolerogenic dendritic
cells, and myeloid-derived suppressor cells. Another factor that could
contribute to the limited immune response is the low mutational load of
glioblastoma, which does not allow for the recognition and removal of cancer
cells by the immune system (Charoentong et al., 2017). All of these factors
combined have led to the testing of checkpoint inhibitors in clinical trials,
which demonstrated that the antigen-specific T cell responses do not always
correlate with tumor regression, suggesting that the immunosuppressive
microenvironment limits the potential of T cell activation (Lim et al., 2018).
While this degree of immunosuppression in glioblastoma appears extreme, it is
consistent with the unique immunosuppressive architecture off the brain and
may, thus, be more difficult to reverse than with tumors in other locations.
Given these barriers to the use of immunotherapy approaches, identifying
mechanisms of peripheral and tumoral immunosuppression in glioblastoma is an
immediate priority.
Our recent work on biomarker identification in the peripheral blood of
glioblastoma patients has led to the identification of a significant increase
in the frequency of a subset of B cells characterized by high expression of
regulatory-associated molecules such as CD25 and the inhibitor receptor
CD95Fas. This atypical B cell subset accounted in a group of glioblastoma
patients for more than 10 % of total peripheral blood mononuclear cells.
Moreover, correlation network analysis demonstrated a dramatic decrease in
correlations of this subset with other immune cell subsets, suggesting a B cell
intrinsic cause for their deregulation. Multiple regression analysis allowed us
to pinpoint a strong association of dexamethasone administration to higher
frequencies of atypical B cells. These atypical memory B cells may well
correspond to regulatory B cells, a B cell subset that is recently gaining
interest due to its immunosuppressive functions that support immunological
tolerance and may also have detrimental effects through contribution to the
immune escape of cancer cells (Sarvaria et al., 2017). Mechanisms of
suppression include the acquisition of inhibitory ligand expression,
phosphorylation of STAT3, and induction of anti-inflammatory cytokines as IL-10
and TGF-β. Regulatory B cell suppressive activity is mainly cytokine-dependent
and may affect diverse cell subtypes, including T effector cells, NK cells,
myeloid derived suppressor cells and/or tumor associated macrophages.
Regulatory B cells may also directly promote tumorigenesis through recruitment
of inflammatory cells, and upregulation of pro-angiogenic genes and
prometastatic collagenases. Regulatory B cell infiltration has been identified
in a variety of solid tumors including, amongst others, ovarian, gastric,
non-small cell lung cancer, pancreatic, esophageal, head and neck, and
hepatocellular carcinomas. In glioblastomas, several reports have demonstrated
the presence of B cells in the tumor infiltrate, and we have preliminary data
that confirms the presence of B cells in surgical material derived from
glioblastoma patients. Increasing evidence suggests that recruitment of B cells
and acquisition of suppressive activity within the tumor bed may be an
important mechanism through which B cells may modulate innate and/or adaptive
anti-tumor immunity. Regulatory B cell depletion in the clinic using anti- CD20
antibodies and/or inhibitors of BTK and/or other signaling pathways, may be a
useful strategy for augmenting the anti-tumor immune response. Conversely,
understanding the reasons causing an increase in regulatory B cell frequencies
may open the door to more effective immunotherapies.

Identify if dexamethasone treatment alters the frequency and functionality of
atypic B cells in blood.

In order to address a potential causative relationship between dexamethasone
administration and the increase of atypical B cell frequencies in the blood of
glioblastoma patients, one would have to design a double-blind randomized
intervention study where patients would be administered dexamethasone or not.
However, such a study cannot be performed in our setting because dexamethasone
is a first line therapy for the neurological complaints associated to edema in
glioblastoma patients. Importantly, not all glioblastoma patients receive
dexamethasone, which allows as to address our question by means of an
observational casecontrol study. According to this reasoning, we proposed the
following case-control study:
- Case group: 10 consecutive newly diagnosed patients with a clinical
indication for of dexamethasone due to their neurological symptoms will be
included to this study. Bloodwill be collected at the time of admission to the
study (prior to the administration of dexamethasone) and two weeks (± 3 days)
later (prior to surgery).
- Control group: The control group will be 10 consecutive newly diagnosed
patients that do not require the administration of dexamethasone. The control
group will also be sampled at the time of the admission to the study and two
weeks (± 3 days) later (prior to surgery).
The duration of the observation will be approximately 2 weeks (the time it
takes between diagnosis of a glioblastoma and the surgical intervention).

Patients won*t benefit personally of being enrolled in this study. There are no
significant risks for patients included in this study. The burden for patients
consists of withdrawing 56 milliliter of blood. Patients do not have to come to
the hospital just for the study. Blood drawl is combined with a regular visit.
Patients do not have to come to the hospital only for study purposes. There are
no direct risks for participating subjects because of the observational nature
of the study.