# C3-Liposome Delivery of MUC1 Peptide and TLR Agonists Enhances Adaptive Immunity and Results in Sex-Based Tumor Growth Differences

## TL;DR

A new cancer vaccine using C3-liposomes and MUC1 peptides boosts immunity and shows different effectiveness in male and female mice.

## Contribution

C3-liposome delivery of MUC1 peptide with TLR agonists reveals sex-based differences in tumor suppression and immune response.

## Key findings

- MUC1 C3-liposome vaccines significantly reduced tumor growth in both male and female mice compared to free MUC1 or PBS.
- Male mice vaccinated with TLR agonists showed greater tumor suppression than females, linked to higher MDSC levels in females.
- The vaccine induced strong adaptive immunity, including increased IFN-γ T cells and MUC1-specific IgG antibodies.

## Abstract

Background: Mucin-1 (MUC1) is a glycoprotein that is hypoglycosylated and overexpressed in most adenocarcinomas, making it a promising target for cancer vaccines. Our group previously demonstrated that C3 (OPSS)-liposomes enhance antigen uptake by antigen-presenting cells (APCs) via the complement C3 pathway and, when combined with toll-like receptor (TLR) agonists, reduce tumor growth in murine cancer models. Methods: In the present study, we evaluate the immunogenicity of MUC1 peptide vaccines encapsulated in C3-liposomes, with and without TLR agonists, using MUC1-tolerant transgenic mice challenged with Lewis lung carcinoma (LLC.MUC1) cells. To assess vaccine effectiveness, tumor volumes were measured, and flow cytometry and ELISA and ELISPOT assays were used to assess the immune response. Results: Both male and female C57BL/6 transgenic mice vaccinated with MUC1 C3-liposomes developed significantly smaller tumors than those vaccinated with free MUC1 peptide or PBS. Notably, a sex-dependent response emerged in mice vaccinated with MUC1 C3-liposomes with TLR agonists (TLR4, TLR7/8, and TLR9); male mice exhibited greater tumor suppression than females. Flow cytometry analysis revealed that female mice had significantly higher levels of CD11b+, LY6C+, and LY6G+ MDSC cells, suggesting a potential mechanism for the sex difference. Additionally, MUC1 C3-liposome vaccination elicited robust adaptive immune responses, including significantly higher levels of IFN-γ-producing T cells and MUC1-specific IgG antibodies compared to non-encapsulated MUC1 or TLR adjuvant-only formulations. Conclusions: These findings underscore the potential of C3-liposome-based antigen vaccines to enhance anti-tumor immunity and highlight the impact of sex differences in vaccine efficacy.