Mycobacteria emulsified in olive oil-in-water trigger a robust immune response in bladder cancer treatment

Abstract

The hydrophobic composition of mycobacterial cell walls leads to the formation of clumps when attempting to resuspend mycobacteria in aqueous solutions. Such aggregation may interfere in the mycobacteria-host cells interaction and, consequently, influence their antitumor effect. To improve the immunotherapeutic activity of Mycobacterium brumae, we designed different emulsions and demonstrated their efficacy. The best formulation was initially selected based on homogeneity and stability. Both olive oil (OO)- and mineral oil-in-water emulsions better preserved the mycobacteria viability and provided higher disaggregation rates compared to the others. But, among both emulsions, the OO emulsion increased the mycobacteria capacity to induce cytokines’ production in bladder tumor cell cultures. The OO-mycobacteria emulsion properties: less hydrophobic, lower pH, more neutralized zeta potential, and increased affinity to fibronectin than non-emulsified mycobacteria, indicated favorable conditions for reaching the bladder epithelium in vivo. Finally, intravesical OO-M. brumae-treated mice showed a significantly higher systemic immune response, together with a trend toward increased tumor-bearing mouse survival rates compared to the rest of the treated mice. The physicochemical characteristics and the induction of a robust immune response in vitro and in vivo highlight the potential of the OO emulsion as a good delivery vehicle for the mycobacterial treatment of bladder cancer.

Mycobacteria-Derived Agents for the Treatment of Urological and Renal Cancers

“…Besides in vivo experiments in the murine BC model showed that M. brumae do not persist neither in the spleen of mice treated intravesically with M. brumae, contrary to BCG, which is found in splenocytes after finishing the intravesical treatment [76,77]. Nevertheless further security studies are needed to confirm the safety of this mycobacterium when it is used in its live form.…”

“…M. brumae also was able to activate a murine macrophage cell line [66,76]. Using the murine orthotopic model of BC, a high percentage of live M. brumae-treated mice survived compared to BCG-treated and non-treated tumor-bearing mice, being the differences significant only in comparison to non-treated-bearing mice [76,77].…”

“…In vitro experiments have demonstrated that M. brumae cells did not persist alive inside both macrophages and BC cells after 72-96 h after infection [76,77]. Besides in vivo experiments in the murine BC model showed that M. brumae do not persist neither in the spleen of mice treated intravesically with M. brumae, contrary to BCG, which is found in splenocytes after finishing the intravesical treatment [76,77].…”

“…In this sense, a critical point for mycobacteria efficacy is the delivery of mycobacteria or mycobacteria antigens into the tumor site. The optimization of mycobacteria formulation could be critical for reducing adverseassociated events [97] and/or improving mycobacteria antitumor efficacy [77]. Moreover, the possibility to manipulate genetically mycobacteria for being vehicle for delivery antigens could lead also a chance to get more potent antitumor tools.…”

Microemulsions as Potent Drug Delivery Systems

“…A recent study demonstrated that etoposide loaded coix seed oil microemulsion system with a droplet size of 35 nm induced apoptosis in A549 human lung carcinoma cells [5]. Another study of olive oil-in-water emulsions preserved the viability of mycobacteria and showed positive response in bladder cancer treatment [6].…”