Liposome-induced immunosuppression and tumor growth is mediated by macrophages and mitigated by liposome-encapsulated alendronate

Abstract

Liposomal nanoparticles are the most commonly used drug nano-delivery platforms. However, recent reports show that certain pegylated liposomal nanoparticles (PLNs) and polymeric nanoparticles have the potential to enhance tumor growth and inhibit antitumor immunity in murine cancer models. We sought herein to identify the mechanisms and determine whether PLN-associated immunosuppression and tumor growth can be reversed using alendronate, an immune modulatory drug. By conducting in vivo and ex vivo experiments with the immunocompetent TC-1 murine tumor model, we found that macrophages were the primary cells that internalized PLN in the tumor microenvironment and that PLN-induced tumor growth was dependent on macrophages. Treatment with PLN increased immunosuppression as evidenced by increased expression of arginase-1 in CD11b+Gr1+ cells, diminished M1 functionality in macrophages, and globally suppressed T-cell cytokine production. Encapsulating alendronate in PLN reversed these effects on myeloid cells and shifted the profile of multi-cytokine producing T-cells towards an IFNγ+ perforin+ response, suggesting increased cytotoxic functionality. Importantly, we also found that PLN-encapsulated alendronate (PLN-alen), but not free alendronate, abrogated PLN-induced tumor growth and increased progression-free survival. In summary, we have identified a novel mechanism of PLN-induced tumor growth through macrophage polarization and immunosuppression that can be targeted and inactivated to improve the anticancer efficacy of PLN-delivered drugs. Importantly, we also determined that PLN-alen not only reversed protumoral effects of the PLN carrier, but also had moderate antitumor activity. Our findings strongly support the inclusion of immune-responsive tumor models and in-depth immune functional studies in the preclinical drug development paradigm for cancer nanomedicines, and the further development of chemo-immunotherapy strategies to co-deliver alendronate and chemotherapy for the treatment of cancer.

Immunological and Toxicological Considerations for the Design of Liposomes

“…Similarly, Sabnani et al and Rajan et al found that compared to the vehicle control (e.g., 5% dextrose solution, saline), empty pegylated liposomes accelerated the growth of subcutaneous TC-1 tumors in mice [109,112]. The accelerated tumor growth was attributed to diminished macrophage function and number of tumor-specific T cells [112], as well as a 66% decrease in M1-TAMs and a 100% increase in M2-TAMs [109]. Based on these results, strategies to overcome immunosuppression and tumor progression triggered by liposomes may potentially improve the efficacy of some liposomal anticancer drugs.…”

“…In an orthotopic ovarian carcinoma (ID8-VEGF-GFP) mouse model, La-Beck et al showed that empty liposomes increased tumor volume by over 3-fold and doubled the number of metastatic sites, compared to the vehicle control [107]. Similarly, Sabnani et al and Rajan et al found that compared to the vehicle control (e.g., 5% dextrose solution, saline), empty pegylated liposomes accelerated the growth of subcutaneous TC-1 tumors in mice [109,112]. The accelerated tumor growth was attributed to diminished macrophage function and number of tumor-specific T cells [112], as well as a 66% decrease in M1-TAMs and a 100% increase in M2-TAMs [109].…”

“…Research groups have also shown that within the tumor microenvironment, liposomes can polarize tumor-associated macrophages (TAMs) [107][108][109]. The reprogramming of classically activated (M1) TAMs, which have a role in eradicating tumor cells in their early stages, to alternatively activated M2-like TAMs has been shown to promote tumor growth and metastasis, as shown in Figure 2 [110,111].…”

Emerging Role of Immunosuppression in Diseases Induced by Micro- and Nano-Particles: Time to Revisit the Exclusive Inflammatory Scenario

“…Other pioneer studies unexpectedly discovered that dendrimer nanoparticles improved disease scores in animal models of granulomatous, autoimmune, and edema diseases ( 116 ). Another example illustrating the immunosuppressive properties of nanoparticles is the study by Rajan ( 117 ). Liposomal nanoparticles possess the ability to elicit an immunosuppressive cell environment that subsequently suppress anti-tumor immunity and favor tumor progression.…”

Estrogen-functionalized liposomes grafted with glutathione-responsive sheddable chotooligosaccharides for the therapy of osteosarcoma

“…Liposomes are the most successful drug delivery nano-carriers for tumor targeted drug delivery (Rajan et al., 2017 ) through the enhanced permeability and retention (EPR) effect (Maeda, 2001 ). To improve the degree of internalization to cancer cells, specific ligand-anchored liposomes have been explored which can be specifically recognized by cancer cells through their over-expressed receptors, for example, the estrogen receptors (Wicki et al., 2015 ).…”