Graduation Date

Spring 5-9-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Biochemistry & Molecular Biology

First Advisor

Surinder K. Batra

Abstract

Numerous cytokines promote pancreatic ductal adenocarcinoma (PDAC) progression and suppress anti-tumor immune response leading to poor prognosis in PDAC patients. Despite this, many cytokines, have not been investigated in PDAC. Bioinformatic analyses of PDAC microarray and RNA-Seq datasets were used to identify cytokines overexpressed in PDAC, confirm the expression of cognate receptors, determine the association of cytokines with patient survival and define key underlying molecular associations. Bioinformatic findings were validated using immunohistochemical (IHC) staining, comparative cytokine qPCR-array in KrasLSL-G12D:TP53LSL-R172H:Pdx1-Cre (KPC) and KrasLSL-G12D:Pdx1-Cre (KC) PDAC models and multicolor immunofluorescence staining. Tail-vein injections of PDAC cells with/without CXCR3 inhibition were used to study altered metastatic potential in vivo and functional assays were conducted to demonstrate causal relationships between CXCR3 activation and metastatic properties of PDAC cells. CXCR3 ligands CXCL9 and 10 were consistently overexpressed in PDAC datasets. CXCR3 was expressed in the majority of PDAC samples according to RNA-Seq, microarray and IHC analysis. CXCR3 ligands CXCL4, 9 and 10 were associated with poor patient survival and were overexpressed in the aggressive KPC murine model compared to KC mice. CXCR3 was associated with increased overall survival in humans. Pathway analysis showed that CXCR3 is associated with T-cell-related genes while CXCL9/10 were associated with T-cell and immunosuppressive genes. CIBERSORT, gene set enrichment and immunofluorescence analysis supported these findings. With respect to metastasis, inhibition of CXCR3 suppressed the number of cancer cells in the lungs following tail vein injection. Cancer cells treated with activated platelets and/or CXCL4 demonstrated increased ability to survive low attachment conditions and fluid shear stress and to adhere to endothelium, suggesting pleotropic roles in the metastatic process. Overall, CXCR3 ligands are overexpressed in PDAC and are associated with poor survival likely related to alterations in immune cell infiltrate/activity and augmented metastatic potential.

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