In Vivio Analysis of Astrocyte Signaling Supporting Syngeneic and Spontaneous Glioma Growth

Author

Alexandra GonsiewskiFollow

Defense Date

2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Biochemistry

First Advisor

Tomasz Kordula

Second Advisor

Sarah Spiegel

Third Advisor

Sandeep Singh

Fourth Advisor

Paula Bos

Fifth Advisor

Devanad Sarkar

Abstract

Glioblastoma multiforme (GBM) is a highly lethal brain tumor characterized by an immunosuppressive tumor microenvironment (TME) that aids in tumor growth and limits the effectiveness of therapeutics. Recently, it was discovered that a subgroup of astrocytes in glioma’s TME expressed phosphorylated STAT3 (pSTAT3). These pSTAT3+ astrocytes greatly increased immunosuppression through upregulating expression of immunosuppressive cytokines and expressed program death-ligand 1 (PD-L1). However, it is not known what molecule persistently activates STAT3 in these astrocytes. We hypothesized that S1P-S1PR1 signaling was responsible for this activation, as it is known to cause prolonged STAT3 activation in several other tissues. To test this prediction, we used a conditional knockout mouse model where S1PR1 is deleted specifically from astrocytes (S1PR1^DAst) We used a Cre driven lentivirus in induce gliomas in our spontaneous model and mouse glioma cell line in the syngeneic glioma model. Both models showed that S1PR1^DAstmice had significantly smaller glioma tumors compared to wild-type or S1PR1^loxp/loxp mice. We discovered that loss of astrocytic S1PR1 significantly increased astrocyte reactivity. S1PR1^DAsthad significantly fewer myeloid cells present in the tumor edge and core and significantly decreased expression of chemokines and cytokines. Further, S1PR1^DAstastrocytes had significantly increased NLRP3 activation, and they also had significantly decreased STAT3 and PD-L1 activation. Altogether, these data suggest that astrocytic S1PR1 creates a unique inflammatory microenvironment that promotes glioma growth. Astrocytic S1PR1 has potential as a future therapeutic target as inhibiting it could decrease the immunologically “cold” state of GBM to allow for a more robust anti-tumor immune response.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

10-1-2024