(A-38) Mechanical and contractile properties of bladder cancer cell lines are linked to their invasive potential

Introduction:: Bladder cancer is a debilitating disease and currently the 6th most frequent cancer. However, bladder cancer has the highest lifetime treatment cost per patient amongst all cancers. This is mainly related to its high recurrence rate, prevalence of comorbidities following recurrence and treatment escalation. A major limitation in understanding this cancer evolution is the lack of well characterized cellular models, especially when compared to other cancers such as breast cancer. Mainly, few studies have documented the invasive potential of bladder cancer cell lines and how these cells interact with their microenvironment. In addition, it is now well understood that cellular mechanical properties are a critical determinant of cell behavior. In this context, determining the relationship between bladder cancer cells mechanical properties and their invasiveness is likely a required enabling step toward improving experimental design in the field of bladder cancer research.


Materials and Methods:: Bladder cancer cell lines from grade 1 tumors (SW780, RT4 and MGHU3) and from grade 3 tumors (SW1710 and T24) were used as cellular models. In vitro invasiveness was assessed using transwells chamber assays by seeding 100,000 cells in the upper chamber with FBS used s the chemoattractant in the bottom chamber. Invasion was measured after 6h. Traction force microscopy was performed on collagen-coated polyacrylamide gel of stiffness ranging from 1 kPa to 10 kPa. For spheroid invasion assay and collagen contraction assays, cells were embedded in 1.5 mg/ml type I collagen. Spheroid invasion was monitored every day for 5 days. Cor compaction assays, the gels were allowed to freely float in the media for 3 days. Quantitative polarization microscopy was performed on 3D samples to directly measure cell contractility. Finally, atomic force microscopy was performed on cells seeded on collagen-coated glass slides using a silicon nitride cantilever with a 4.5 µm spherical tip and a nominal spring constant of 0.01 N m^-1.


Results, Conclusions, and Discussions:: To determine the invasive ability of the bladder cancer cells, we first measured their transmigration ability using transwells chamber. Focusing on SW780 and T24 cells, our results showed that the T24 cells were more invasive than the SW780 cells (Fig 1a). Similar results were obtained with the other cell lines. We then proceeded to confirm this invasion potential by assessing spheroids invasion within 3D collagen scaffolds. Similar to the transwells chamber results, T24 spheroids displayed increased outgrowth and invasion within the collagen compared to SW780 spheroids (Fig. 1b). In line with the difference in invasive potential, traction force microscopy further revealed that SW780 cells had minimal contractility levels whereas the T24 cells were highly contractile (Fig1 C and D). Assessment of 3D collagen remodeling and collagen compaction provided similar outcomes, further supporting the difference in cell contractility. These results are consistent with previous observations made on breast and prostate cancer cells. Ongoing experiments aim to expand the contractility measurements to the other bladder cancer cell lines. Overall, this work will provide an in-depth biophysical characterization of bladder cancer cell line that is currently missing. This knowledge will be essential in future studies trying to understand bladder cancer progression.


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