Abstract 3574: Novel roles of an axon-guidance molecule, semaphorin 3E, in pancreatic cancer

Background: Pancreatic ductal adenocarcinoma (PDAC) is the 4th leading cause of cancer death in the US with a 5-year survival rate of less than 6%. There is an urgent need for a better understanding of PDAC in order to find better therapeutic targets. Two recent large-scale genomic analyses of human PDAC have uncovered increased copy numbers of an axon-guidance gene SEMA3E that codes for Semaphorin-3E (Sema3E). Several recent reports have implicated Sema3E in metastasis of breast and colon cancers, particularly in promoting tumor cell migration and invasion, as well as inducing epithelial-to-mesenchymal transition (EMT). We hypothesize a possible new role of an axon-guidance gene Sema3E in PDAC progression by promoting cell proliferation, invasion, and metastasis. Materials and Methods: To determine expression levels of Sema3E in human PDAC, qRT-PCR and IHC analysis was performed on resected PDAC samples and matched tissue controls. To determine Sema3E levels in mouse PDAC, IHC analysis was performed on pancreas tissue from a genetically engineered spontaneous PDAC mouse model, the PDX-1-Cre; KrasG12D; P53R172H (KPC) mouse. To generate Sema3E-overexpressing stable cells, human PDAC cell lines Mia PaCa-2 and Panc-48 cells were transduced with Sema3E-expressing lentivirus or vector control. QRT-PCR and western blot analyses were performed to verify the overexpression of Sema3E. Colony formation assay (CFA) and MTT assay were performed on Sema3E-transduced cells to determine the effects of Sema3E on cell survival and proliferation respectively, while a wound healing assay and boyden chamber assay were performed to determine effects of Sema3E on cell migration and invasion respectively. Results: Sema3E was found to be significantly upregulated in 46% of patient PDAC samples (n = 24), with an average fold-change of 9.54 across the samples. IHC analyses of patient and mouse PDAC revealed higher expression of Sema3E in tumor cells compared to normal cells. Interestingly, Sema3E expression was concentrated in the nuclei of tumor cells while it has been reported in current literature to be a secreted protein found in normal tissues. Sema3E-transduced PDAC cell lines Mia PaCa-2-Sema3E and Panc-48-Sema3E had higher Sema3E expression in cell lysates and culture supernatant compared to control cells. Mia PaCa-2-Sema3E had a 60.4% higher rate of colony formation than the control (p = 0.005), while both Mia PaCa-2-Sema3E and Panc-48-Sema3E had higher proliferation rates