Login to Access Video or Poster Abstract: MP65-01
Sources of Funding: None

Introduction

Intravesical Bacillus Calmette-Guérin (BCG) immunotherapy has been used to treat non-muscle invasive bladder cancer (BC) for nearly 40 years but its underlying mechanism remains largely unknown. It is generally believed that BCG adheres to integrin ?5?1 in the urothelial lining by interacting with fibronectin, then triggers an immune response cascade. Extracellular vesicles (EVs), small membrane-bound vesicles, act as immune modulators by transferring molecular cargos to recipient cells. We hypothesize that EVs derived from BC cells play key roles in mediating BCG-induced anti-tumor host immune responses, and the patient derived EVs may serve as predictive biomarkers that can differentiate BCG responders from non-responders.

Methods

BC cell lines, human T24 and murine MB49, and immortalized bladder SV-HUC cells were treated with 1-4x106 CFU/ml live BCG. After 12-72 hours, secreted EVs were isolated by serial ultracentrifugation and analyzed by Nanoparticle Tracking Analysis. Cell lysate and total RNA was collected for immuno-molecular profiling by quantitative PCR and Western blotting analyses. The alterations in EV secretion, gene and protein expression, and molecules from BC derived EVs in response to BCG were compared. Urinary EVs were collected and purified before and after BCG patients’ 1st and 3rd BCG instillations and EV secretion profiles were compared.

Results

In response to BCG, SV-HUC cells showed decreased EV secretion and their immuno- molecules were significantly reduced compared with EVs from naïve SV-HUC cells. In contrast, in BC cells the EV secretion rate was significantly induced by BCG as well as the expression of the key molecules in modulating immune response, such as MHC and co-stimulatory molecules at gene and protein levels. Critically, we found that BC cells, but not SV-HUC cells, released immuno-molecules containing EVs in response to BCG. Importantly, we found that urinary EV numbers were increased significantly after the 3rd BCG instillation in BCG responders, but not in BCG-non-responders in a pilot study.

Conclusions

We conclude that BCG treatment resulted in increased EV release from BC cells as well as in increased EVs in urine of BC patients. In addition, BCG induced expression of key immuno-modulatory molecules in BC cells and within the EVs. This up-regulated expression of immuno-molecules in response to BCG supports the hypothesis that EVs have a role in activating the immune system during BCG immunotherapy. The immunologically active EVs detected in patients’ urine can be further explored as predictive biomarkers.

Funding

None