Mutant Kras Alters Extracellular Vesicle Microrna Sorting In Pancreatic Cystic Neoplasms

Author

Rachel L. Dittmar, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical SciencesFollow

Author ORCID Identifier

https://orcid.org/0000-0002-0567-2450

Date of Graduation

12-2021

Document Type

Dissertation (PhD)

Program Affiliation

Human and Molecular Genetics

Degree Name

Doctor of Philosophy (PhD)

Advisor/Committee Chair

Subrata Sen, Ph.D.

Committee Member

Ann Killary, Ph.D.

Committee Member

Anirban Maitra, M.B.B.S.

Committee Member

Pierre McCrea, Ph.D.

Committee Member

Stanley Hamilton, M.D.

Committee Member

Jody Vykoukal, Ph.D.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest cancers by organ site with a 5-year survival rate of just 10.8%. This is largely because most patients do not experience symptoms until the disease has already metastasized. The best hope to cure PDAC is surgery, which can only be done with a curative intent at an early stage when the disease is localized. There are no reliable circulating, body-fluid-based biomarkers to detect early stage PDAC or its precursor lesions in a timely manner for effective surgical intervention. When potential PDAC precursor lesions, such as mucinous pancreatic cysts are found, there are no reliable molecular markers to determine which of these lesions will become to PDAC.

The most frequently mutated gene in PDAC, the oncogene KRAS, remains largely undruggable, except for KRAS^G12C mutations, which may be inhibited by sotorasib. Activating mutations in the oncogene KRAS are believed to be the earliest genetic mutation in the development of this disease, occurring in up to 95% of PDACs and 60% of mucinous cysts. While it is well-known that mutant KRAS deregulates many biological processes, little is known about the effect of KRAS on loading of cargo into extracellular vesicles (EVs). EVs are released into body fluids by normal and pre-malignant/malignant cells, which, by virtue of their function involvement in intercellular communications, play critical roles in the development and progression of cancer. These vesicles harbor an assortment of biomolecules shielded from degradation within their membrane bound lumen. For this reason, EVs offer a unique opportunity to study biomolecules in circulation and could provide a snapshot of disease biology, including cancer, in real time. In recent years, EV microRNAs (miRNAs) small, noncoding, epigenetic modulators of gene expression, have been of interest due to their well-documented role in cancer.

Herein, we demonstrate that mutations in KRAS are associated with alteration to the EV miRNome in a cell line disease progression model system and mucinous pancreatic cysts. We have investigated the functional significance of mutant KRAS in the generation of altered EV miRNA content.

Keywords

pancreatic cancer, extracellular vesicle, exosome, liquid biopsy, KRAS, early detection, pancreatic cyst, microRNA, genetics, SRSF1