Pancreatic Cancer: Oncomicrobes, Electric Fields, and Fluid Flow

Abstract

The pancreatic tumor microenvironment exhibits remarkable complexity, prompting critical investigations into how the microbiota influences tumor progression and how stromal elements impact interstitial fluid dynamics. This dissertation examines dual aspects of this complexity: first, by elucidating the specific contributions of Fusobacterium nucleatum (F. nucleatum) to pancreatic cancer pathogenesis and developing a novel therapeutic approach for eliminating these intracellular bacteria; and second, by analyzing how a stromal-targeted therapy directed at hyaluronic acid modulates interstitial fluid flow within pancreatic tumors using clinical patient data. We demonstrated that F. nucleatum invade both pancreatic cancer cells and normal pancreatic epithelial cells (nPECs). This invasion process was partially mediated by the bacterial adhesin Fap2. nucleatum infection induced a distinct cytokine secretion profile, characterized by elevated IL-8, CXCL1, MIP-3α, and GM-CSF. F. nucleatum invasion promoted migration and proliferation in Panc1 and BxPC3 cancer cell lines. Conditioned media from infected BxPC3 cells stimulated migration in both uninfected BxPC3 and Panc1 cells, suggesting paracrine effects. While F. nucleatum-infected nPECs exhibited a similar cytokine profile, they did not display increased proliferation or self-migration. However, conditioned media from infected nPECs enhanced BxPC3 cancer cell migration, indicating potential cross-talk. Building on these findings, we engineered an electro-antibacterial therapy (EAT) that enhances antibiotic delivery into the intracellular compartment. This approach employs pulsed electric fields to achieve controlled permeabilization of host cell membranes through precise modulation of electric field strength. By combining pulsed electric fields with a standard-of-care antibiotic, we achieved greater than 99% clearance of intracellular F. nucleatum from pancreatic cancer cells. We next examined the broader biophysical features of the tumor microenvironment. We characterized interstitial fluid flow in pancreatic cancer patients, recognizing that desmoplasia creates significant barriers to treatment and influences interstitial fluid pressure. Our analysis of patients treated with PEGPH20, a hyaluronidase enzyme, revealed a transient reduction in velocity magnitudes one day post-treatment, though values generally returned to baseline by the conclusion of the dosing cycle. We observed substantial heterogeneity of velocity magnitudes both within individual tumors and across multiple tumors within the same patient. In one patient with five distinct tumors, we identified variable treatment responses that correlated with tumor size, though velocity magnitude itself did not emerge as a reliable predictor of treatment response.