Discipline: Technology and Engineering
Subcategory: Biomedical Engineering
Alex Avendano - Ohio State University
Co-Author(s): Jonathan Chang, Jason R. Pitarresi, Michael C. Ostrowski, and Jonathan W. Song, Ohio State University, Columbus, OH Christina Ennis, Kenyon College, Gambier, OH Amanda Stratton, Lehigh University, Bethlehem, PA
The tumor stroma has emerged as an important mediator of pancreatic cancer growth and metastasis to distant sites of the body. In particular, loss of the tumor suppressor gene phosphatase and tensin homolog (PTEN) in pancreatic cancer associated fibroblasts (CAFs) within the tumor stroma has been shown to accelerate tumor progression and therapeutic resistance, resulting in a more aggressive tumors. However, knowledge of how loss of PTEN in CAFs function to produce this effect is limited, due in part to difficulties of current in vitro approaches to model the tumor stroma and in vivo approaches to isolate and quantify the individual effects of CAFs. Using a microfluidic 3D model of the tumor stroma, this study set out to characterize how loss of PTEN in CAFs alters two biophysical properties of the tumor microenvironment: i) collagen fiber alignment and ii) hydraulic permeability or the ability of fluid to flow through a porous medium. Aligned collagen fibers have been shown to provide contact guidance for tumor cells to metastasize while hydraulic permeability is an indicator of how well flow and drugs can penetrate into the tumor. We hypothesized that loss of PTEN would result in more aligned collagen fibers and decreased hydraulic permeability, characteristic of very aggressive pancreatic tumors. To evaluate our hypothesis, a microfluidic model of the tumor stroma was designed, fabricated, and optimized to measure collagen fiber alignment and hydraulic permeability as a function of PTEN deletion in CAFs. The microfluidic model consisted of polydimethylsiloxane devices fabricated using soft lithography. The devices consisted of a single straight channel (5mmx500umx1mm) with 4mm inlet/outlet ports. Pancreatic CAFs, isolated from human pancreatic tumors, were suspended in a rat tail type I collagen hydrogel, injected into the channel, and cultured between 2 days for hydraulic permeability measurements or 4 days for collagen fiber alignment measurements. The conditions tested were control pancreatic CAFs(shnc), pancreatic CAFs with PTEN silenced with shRNA(shPTEN), and acellular collagen Type I hydrogel. We detected no significant differences in collagen fiber alignment when comparing shnc, shPTEN, and acellular collagen conditions. In contrast, the hydraulic permeability decreased significantly for the shPTEN condition. These results indicate that loss of PTEN in CAFs results in decreased hydraulic permeability of the tumor stroma that is independent of collagen fiber alignment. Furthermore, the decrease in the hydraulic permeability conferred by shPTEN fibroblasts can explain why loss of PTEN in pancreatic tumors results in resistance to therapy since decreased hydraulic permeability impedes delivery of therapeutic agents into the tumor. Since fiber alignment was not observed to be impacted by expression of PTEN in CAFs, we suspect that this decrease in hydraulic permeability is mediated by the deposition of extra-fibrillar matrix molecules that increase the hydraulic resistance through the porous medium. Future studies will use our developed in vitro system to investigate what biochemical changes occur in the stroma as a function of loss of PTEN in CAFs, and to develop strategies to prevent/reverse this effect. This approach can potentially yield new therapeutic strategies that can improve the poor outcome of current standard of care therapies for pancreatic cancer, currently one of the deadliest malignant solid tumors.
Funder Acknowledgement(s): American Cancer Society; American Heart Association; Ohio State University Institute for Materials Research Pelotonia
Faculty Advisor: Jonathan Song, firstname.lastname@example.org
Role: Alex Avendano was responsible for developing the research, microdevice fabrication, cell culture, data analysis, and training undergraduate students to perform the research.