Breast cancer remains one of the leading causes of cancer-related death, with triple-negative breast cancer (TNBC) accounting for 15–20% of cases. TNBC, characterized by the absence of ER, PR, and HER2 protein, is an aggressive form of breast cancer that is unresponsive to hormonal therapies and HER2-targeted treatments, with fewer treatment options and poorer prognosis. Oncolytic adenoviruses (Ad) are a potential treatment option for TNBC but require coxsackievirus and adenovirus receptors (CAR) to effectively enter and transduce cancer cells. This study investigates a novel neoadjuvant therapy to improve the efficacy of an oncolytic Ad with human telomerase reverse transcriptase (Ad-hTERT) in CAR-low TNBC tumors using folate surface-modified liposomes to enhance delivery. This therapy helps deescalate treatment by reducing or eliminating the need for checkpoint inhibitors or toxic chemotherapy combinations. In vitro studies using CAR-low TNBC murine 4T1-eGFP cells, CAR-high TNBC human MDA-MB-231-GFP cells and several other TNBC human cancer cell lines with varying CAR expression demonstrated significantly higher cytotoxicity with encapsulated Ad-hTERT compared to Ad-hTERT. Similar results were observed in patient-derived primary TNBC cells. In vivo studies in immunocompetent mice with CAR-low 4T1-eGFP tumors revealed that encapsulated Ad-hTERT, administered as neoadjuvant therapy, resulted in stable or reduced tumor sizes, improved survival rates, higher apoptosis of cancer cells, lower cancer cell proliferation, and increased T-cell infiltration in resected tumors. Furthermore, encapsulated Ad-hTERT prevented lung metastasis and tumor recurrence at the primary site, resulting in higher survival rates in mice. Thus, liposomal encapsulation of Ad may be a viable strategy for treating TNBC.

Background/Objectives: While adenovirus (Ad) therapies have been proven to be effective in local administration, systemic Ad treatments have shown limited success due to pre-existing antibodies in the human blood that neutralize the virus. We developed a liposome coating procedure that protects the Ad from pre-existing neutralizing antibodies in human blood. To assess the in vivo stability of the liposomes, the present study used a novel in vivo method to quantitatively assess the protective capabilities of liposome-encapsulated Ad (DfAd) from neutralizing antibodies. Methods: The assay systemically administers DfAd with a green fluorescent protein transgene (DfAd-GFP) into pre-immunized mice and allows it to circulate in the presence of neutralizing antibodies; the infected blood is extracted and used to transduce HEK293 cells, which emits fluorescence in the presence of protected, un-neutralized Ad. Results: The PEGylated liposome formulation provides 12× protection in vivo relative to unencapsulated Ads. In vitro optimization of the liposome coating reveals a strong correlation between the structural stability of liposomes and protection against anti-Ad neutralizing antibodies, where DSPE-PEG2000-carboxylic acid (DSPE-PEG2000-CA) is a critical component for liposome stability and increasing protection against antibody neutralization of the encapsulated Ad. Conclusions: The findings in the present study confirm that the DfAd liposome can protect against neutralizing antibodies in blood circulation. The novel in vivo assay for liposome protection against neutralizing antibodies and in vitro experiments in the present study provide new tools and insights toward designing liposome–Ad complexes for the systemic treatment of cancer.

Viral vectors such as adenovirus (Ad) and lentivirus (LV) are central to gene therapy owing to their transduction efficiency and broad applicability; however, their clinical translation is often limited by immunogenicity, rapid clearance, and reduced bioavailability. Non-enveloped Ad vectors are highly susceptible to neutralization by pre-existing antibodies, while enveloped LVs remain vulnerable to immune surveillance and off-target clearance. In this study, a biomimetic encapsulation strategy using erythrocyte-derived membranes (EDMs) is reported to enhance viral immune resilience and functional gene delivery. Ad-GFP and LV-mCherry were successfully encapsulated within EDM using an extrusion-based assembly approach, resulting in uniform membrane-coated particles with physicochemical properties characteristic of erythrocyte membranes. EDM encapsulation significantly enhanced in vitro transduction efficiency of both viral platforms across multiple cancer cell lines without compromising viral activity. Notably, EDM-Ad-GFP demonstrated robust protection against neutralizing antibodies, achieving significantly higher transduction of HEK293 cells in the presence of diluted human serum compared to unencapsulated Ad. These findings indicate that EDM encapsulation can effectively shield viral vectors from immune recognition while improving cellular uptake and transduction performance. Collectively, this work establishes EDM encapsulation as a versatile and scalable platform to enhance the efficacy, durability, and translational potential of viral gene delivery systems.