Construction of the systemic anticancer immune environment in tumour-bearing humanized mouse by using liposome-encapsulated anti-programmed death ligand 1 antibody-conjugated progesterone

Abstract

Immune checkpoint inhibitors highlight the importance of anticancer immunity. However, their clinical utility and safety are limited by the low response rates and adverse effects. We focused on progesterone (P4), a hormone produced by the placenta during pregnancy, because it has multiple biological activities related to anticancer and immune regulation effects. P4 has a reversible immune regulatory function distinct from that of the stress hormone cortisol, which may drive irreversible immune suppression that promotes T cell exhaustion and apoptosis in patients with cancer. Because the anticancer effect of P4 is induced at higher than physiological concentrations, we aimed to develop a new anticancer drug by encapsulating P4 in liposomes. In this study, we prepared liposome-encapsulated anti-programmed death ligand 1 (PD-L1) antibody-conjugated P4 (Lipo-anti-PD-L1-P4) and evaluated the effects on the growth of MDA-MB-231 cells, a PD-L1-expressing triple-negative breast cancer cell line, in vitro and in NOG-hIL-4-Tg mice transplanted with human peripheral blood mononuclear cells (humanized mice). Lipo-anti-PD-L1-P4 at physiological concentrations reduced T cell exhaustion and proliferation of MDA-MB-231 in vitro. Humanized mice bearing MDA-MB-231 cells expressing PD-L1 showed suppressed tumor growth and peripheral tissue inflammation. The proportion of B cells and CD4+ T cells decreased, whereas the proportion of CD8+ T cells increased in Lipo-anti-PD-L1-P4-administrated mice spleens and tumor-infiltrated lymphocytes. Our results suggested that Lipo-anti-PD-L1-P4 establishes a systemic anticancer immune environment with minimal toxicity. Thus, the use of P4 as an anticancer drug may represent a new strategy for cancer treatment.

Liposome-encapsulated progesterone efficiently suppresses B-lineage cell proliferation

“…Lipo-P4 and empty control liposomes (Lipo-Emps) were prepared as described previously [ 13 ]. Details are provided in the Supplemental Materials.…”

“…Human PBMCs (5 × 10 6 cells) were intravenously injected into 8-week-old NOG-hIL-4-Tg mice (hu-PBL NOG-IL-4-Tg mice). Female mice were used, while previous studies with hu-PBL NOG IL-4-Tg mice showed no influence of sex with respect to the lymphocyte engraftment [ 13 , 19 ]. On the same day, Lipo-anti-PD-L1-P4 was administered intraperitoneally, and this treatment continued every five days, for a total of six times.…”

“…In some studies, the effect of P4 has been reported to depend on its concentration and receptor expression [ 12 ]. To deliver a higher amount of P4 to cancer cells in vivo , we used a liposome-encapsulated form (Lipo-P4) and developed an anticancer drug candidate, Lipo-P4-aPDL1, which is a Lipo-P4 conjugated with atezolizumab [ 13 ].…”

“…However, the reconstruction of the individual immune environment is difficult because peripheral blood mononuclear cells (PBMCs) should be used for the reconstruction of human immunity in mice; however, PBMCs induce graft versus host disease when they are transplanted into severely immunodeficient mice. Therefore, we developed a new tumor-bearing humanized mouse system constructed by transplanting human PBMCs into a tumor-bearing NOG-hIL-4-Tg mouse system (PBL-NOG-hIL-4-Tg) to evaluate the effects of human immune drugs [ 13 ]. In the humanized NOG-hIL-4-Tg mouse system, human T and B cells were engrafted efficiently, whereas other PBL-humanized mice could not maintain human B cells [ 14 ].…”

“…B cells secrete antigen-specific antibodies via immunization [ 19 ]. Lipo-P4-aPDL1 effectively suppressed the growth of the triple-negative breast cancer cell line MDA-MB231, which expresses PD-L1 when transplanted into PBL-NOG-hIL-4-Tg cells [ 13 ]. Moreover, we found that the proportion of human immune B cells engrafted in mice was significantly decreased, suggesting that Lipo-P4-aPDL1 may efficiently suppress the survival of the B-cell lineage.…”