Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease with a dismal five-year survival rate of 9% even with current treatments. There are two molecular tumor subtypes of PDAC; basal-like PDAC is more aggressive and associated with shorter survival times. Recent clinical trials have found that basal-like PDAC patients fail to respond to first-line chemotherapies including FOLFIRINOX, so it is critical to find better treatment options for this subtype. To study PDAC subtypes, organoids are utilized as they have been shown to represent both molecular subtypes, unlike conventional 2D cell lines. First, this study aims to identify genes whose depletion increases basal-like PDAC sensitivity to FOLFIRINOX using a CRISPR/Cas9 loss-of-function screen targeting 395 basal-like marker genes in basal-like PDAC organoids. The synthetic lethality hits may be studied in the future as drug targets for use in combination with FOLFIRINOX as a more efficacious therapeutic strategy for basal-like PDAC. To study the biology of basal-like PDAC, I will investigate the role of dysregulation of cell polarity in the PDAC subtypes using organoid models. Preliminary data suggest that basal-like PDAC is characterized by a loss of cell polarity while classical PDAC maintains it. Basal-like organoids do not organize to form hollow lumens like classical organoids and the most differentially phosphorylated proteins and pathways between subtypes involve cell adhesion and cell polarity. Dysregulation of cell polarity may increase cancer cell invasion, potentially contributing to poor outcomes in basal-like PDAC. Using fluorescence microscopy, this study will determine whether the localization of cell polarity markers is altered in basal-like PDAC compared to classical in a manner consistent with a loss of cell polarity. It will also be tested whether genetic depletion of cell polarity genes results in a shift from classical to basal-like phenotype, as measured by loss of organoid lumens and increased invasion. Understanding this facet of subtype biology could lead to future therapeutic strategies leveraging cell polarity to convert basal-like PDAC to a more classical phenotype, as classical PDAC is more responsive to current treatments. Overall, this project will advance our understanding of the biology underlying PDAC subtypes and move toward the development of therapeutic strategies for basal-like PDAC. This project will be supported by the extensive resources of the UNC Chapel Hill and the Department of Pharmacology as well as by co-mentorship by Drs. Jen Jen Yeh and Gaorav Gupta.
The basal-like molecular subtype of pancreatic cancer is associated with poor outcomes and fails to respond to the first-line chemotherapy FOLFIRINOX. The proposed project uses CRISPR/Cas9 screening to identify genes that exhibit synthetic lethality with FOLFIRINOX that may be studied in the future as drug targets to sensitize basal-like PDAC to FOLFIRINOX. It also investigates cell polarity loss in basal-like PDAC and whether it contributes to invasiveness.
