LyP-1-modified oncolytic adenoviruses targeting transforming growth factor β inhibit tumor growth and metastases and augment immune checkpoint inhibitor therapy in breast cancer mouse models.

: We report here the development of oncolytic adenoviruses (Ads) that have reduced toxicity, enhanced tumor tropism, produce strong antitumor response, and can overcome resistance to immune checkpoint inhibitor therapy in breast cancer. We have shown that LyP-1 receptor (p32) is highly expressed on the surface of breast cancer cells and tumors from cancer patients, and that increased stromal expression of TGFβ-1 is associated with triple negative breast cancer (TNBC) . Therefore, we constructed oncolytic Ads, AdLyp.sT and mHAdLyp.sT, in which p32-binding LyP-1 peptide was genetically inserted into adenoviral fiber protein. Both AdLyp.sT and mHAdLyp.sT express sTGFβRIIFc, a TGFβ decoy that can inhibit TGFβ pathways. mHAdLyp.sT is an Ad5/48 chimeric hexon virus in which hypervariable regions (HVRs 1-7) of Ad5 are replaced with the corresponding Ad48 HVRs. AdLyp.sT and mHAdLyp.sT exhibited better binding, replication and produced higher sTGFβRIIFc protein levels in breast cancer cell lines compared to Ad.sT or mHAd.sT control viruses without LyP-1 peptide modification. Systemic delivery of mHAdLyp.sT in mice resulted in reduced hepatic/systemic toxicity compared to Ad.sT and AdLyp.sT. Intravenous delivery of AdLyp.sT and mHAdLyp.sT elicited strong anti-tumor response in a human MDA-MB-231 bone metastasis model in mice, as indicated by bioluminescence imaging (BLI), radiographic tumor burden, serum TRACP 5b and calcium, and body weight analyses. Furthermore, intra-tumoral delivery of AdLyp.sT in 4T1 model in immunocompetent mice inhibited tumor growth and metastases, and augmented anti-PD-1 and anti-CTLA-4 therapy. Based on these studies, we believe that AdLyp.sT and mHAdLyp.sT can be developed as potential targeted immunotherapy agents for the treatment of breast cancer.