Author ORCID Identifier

0000-0002-0599-9744

Date of Graduation

8-2021

Document Type

Dissertation (PhD)

Program Affiliation

Cancer Biology

Degree Name

Doctor of Philosophy (PhD)

Advisor/Committee Chair

John F. Hancock

Committee Member

Jeffrey Frost

Committee Member

E. Scott Kopetz

Committee Member

Dung-Fang Lee

Committee Member

Yong Zhou

Abstract

The small GTPase KRAS, which is frequently mutated in human cancers, must be localized to the plasma membrane (PM) for biological activity. We recently showed that the KRAS C-terminal membrane anchor exhibits exquisite lipid-binding specificity for select species of phosphatidylserine (PtdSer). We therefore investigated whether reducing PM PtdSer content is sufficient to abrogate KRAS oncogenesis. Oxysterol-related binding proteins ORP5 and ORP8 exchange PtdSer synthesized in the ER for phosphatidylinositol-4-phosphate (PI4P) synthesized in the PM. We show that depletion of ORP5 or ORP8 reduced PM PtdSer levels, resulting in extensive mislocalization of KRAS from the PM. Concordantly, ORP5 or ORP8 depletion significantly reduced proliferation and anchorage-independent growth of multiple KRAS-dependent cancer cell lines, and attenuated KRAS signaling in vivo. Similarly, functionally inhibiting ORP5 and ORP8 by inhibiting PI4KIIIα-mediated synthesis of PI4P at the PM selectively inhibited the growth of KRAS-dependent cancer cells over normal cells in vitro and in vivo. Hence, inhibiting KRAS function through regulating PM PtdSer content may represent a viable strategy for KRAS-driven cancers.

Keywords

KRAS, PI4KA, ORP5, ORP8, phosphatidylserine, PI4P, cancer, drug repurposing

Available for download on Friday, July 29, 2022

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