Inflammatory pathways and predictive biomarkers in sarcoidosis

Despite decades of both basic and clinical research, our understanding of
sarcoidosis is only beginning. At present, treatment options for sarcoidosis are
both limited as well as hampered by a high prevalence of bothersome side effects.
Consequently, there is need for more research to unravel the molecular basis of
the disease, its various phenotypes/endotypes and identify associated biomarkers.
This pursuit is not only important for improving patient care but also to provide the
patient with better prediction of the long-term outcome. This thesis aimed
to pave the way for precision medicine for sarcoidosis care by identifying novel
predictive and therapeutic biomarkers in form of proteins or signaling pathways.
Chapter 2 will provide an overview of current knowledge on biomarkers and
disease pathology in sarcoidosis. In addition to existing biomarkers, this overview
will also explore new biomarkers for diagnosis and prognosis as well as predictive
for response to treatment of sarcoidosis.
In the search for potential new biomarkers, there has been an increased interest
in extracellular vesicles (EVs). Chapter 3 will focus on the use of EVs as a
new medium for predictive biomarkers. In this pilot study, the predictive potential
of four proteins is studied, comparing their concentration in serum to that in EVs.
In Chapter 4 targeted proteomics by OLINK will be used to identify potential
biomarkers predictive for treatment response. Of the 92 proteins studied in patient
cohorts treated with either prednisone or methotrexate, twenty-five proteins are
identified. A replication cohort will be used to confirm the predictability of the
identified proteins and to study their related pathways with the aim of finding
mechanisms of action of prednisone or methotrexate.
In Chapter 5 we will continue our search for potential biomarkers in EV proteins
by performing a proteomics approach using LC-MS/MS. Proteins that are
significantly different between patients with sarcoidosis and healthy controls will
be studied further to see what pathways are involved in the disease. In addition,
proteins that are differently expressed between responders and non-responders
to treatment with either prednisone or methotrexate are also identified. The top
10 differently expressed proteins will be validated by measuring them in a larger
second cohort. Moreover, protein concentrations are measured over time in an
additional prospective cohort to see how they behave during treatment.
Data on successful treatment of sarcoidosis patients with JAK/STAT and mTORC1
inhibitors suggest that these immunological pathway could also be
explored as predictive biomarkers or therapeutic targets. In Chapter 6 the
activation of the mTORC1 signaling pathway will be studied with the use of
immunohistochemistry in granulomas of Dutch patients with sarcoidosis, GPA,
EGPA and HP. Results of the staining will be studied in relation to disease course.
Chapter 7 will continue the exploration of immunological pathways as predictive
biomarkers and will demonstrate the activation of the JAK-STAT and the NLRP3
inflammasome signaling pathways in Dutch patients with sarcoidosis. In this
chapter specific ‘signaling endotypes’ will be evaluated in relation to disease
course.