Background Colorectal cancer is the third most commonly diagnosed malignant tumor, taking fourth place in terms of cause of cancer deaths worldwide.1 Unfortunately, the ability of the immune system to distinguish its own from foreign cells is often limited. One of the overexpressed receptors is receptor CD47 - widely distributed glycoprotein on the cell surface of various kind of tumors. It plays a role as ‘don’t eat me’ signal by binding with receptor SIRPα, presents on the cell surface of macrophages.2 Calreticulin, protein occurring on the surface of tumor cells and phagocytes, acts as protein with pro-phagocytic properties. Several natural bioactive substances are predicted to induce immunogenic cell death by translocation calreticulin on the surface of cancer cells which significantly increases the efficiency of their phagocytosis. Moreover, one of the well-known TLR-7 receptor agonists - imiquimod, is involved in phosphorylation of Bruton’s tyrosine kinase leading to the appearance of calreticulin on the surface of macrophages, which increases the efficiency of phagocytosis of tumor cells.3 Combination therapy composed of berberine and imiquimod can be highlighted as effective immunotherapy for colon cancer. However, such an approach remains very limited. Liposomes can serve as promising carriers for targeting delivery and controlled release of anti-cancer agents.
Material and Methods Liposomes were prepared by the thin-film hydration method followed by extrusion. Human colon cancer cell line (LS180 I SW620) and human monocytic cell line (THP-1) were used for experiments. Calreticulin was detected by using confocal microscopy.
Results The work presented aimed to develop novel liposomal formulations of berberine and imiquimod which were examined for their efficacy in combination against colorectal cancer cell lines. Liposomal formulations of both compounds were successfully prepared using active loading method with different pH generating agents. All loading methods showed desired characteristics in terms of mean liposome size and polydispersity. The encapsulation efficiency was higher than 95% for almost all used formulations. The in vitro study proved cytotoxicity of berberine loaded liposomal formulations on tested colon cancer cell lines. The results of the immunofluorescence staining indicated that the both compounds triggered calreticulin on the cell surface (colon cancer or macrophages).
Conclusions The combination of both substances in the liposomal form may generate a synergistic effect on phagocytosis of colon cancer cells.
Arnold M, Sierra MS, Laversanne M, et al. Global patterns and trends in colorectal cancer incidence and mortality. Gut 2017;66:683–691.
Sick E, Jeanne A, Schneider C, Dedieu S, Takeda K, Martiny L. CD47 update: a multifaceted actor in the tumor microenvironment of potential therapeutic interest, Br J Pharmacol 2012, 167(7):1415–30.
M. Feng, et al., Macrophages eat cancer cells using their own calreticulin as a guide: Roles of TLR and Btk. PNAS 2015;112( 7):2145–2150.
Disclosure Information M. Mianowska: B. Research Grant (principal investigator, collaborator or consultant and pending grants as well as grants already received); Significant; National Science Center, Poland. M. Zaremba-Czogalla: None. A. Zygmunt: None. J. Gubernator: None.
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