The development of novel therapies for the treatment of breast cancer is a major unmet need. In recent years, immune checkpoint inhibitors including anti-PD-1, anti-PD-L1 and anti-CTLA-4 have shown promise as antitumor agents, and are approved for the treatment of several malignancies. Clinical trials in breast cancer patients have shown that about 20% of triple negative breast cancers (TNBC) respond favorably to anti-PD-1 antibodies and Atezolizumab, an anti-PD-L1 antibody in combination with nab-paclitaxel (Abraxane) is now FDA approved for advanced stage TNBC patients with positive PDL-1 expression. However, many TNBC patients are resistant to anti-PD-1/PDL-1 and anti-CTLA-4 treatments which could be due to weak immunogenicity of the tumors and poor inflammatory but highly immune suppressive tumor microenvironment. In recent years TGF? has been shown to be a strong immune suppressor and can potentially produce a tumor microenvironment that is resistant to anti-PD-1 and anti-CTLA-4 therapy. To overcome resistance to anti-PD-1 and anti-CTLA-4 we have developed adenoviruses (Ad) expressing sTGF?RIIFc (soluble TGF? receptor II fused with human IgG Fc). sTGF?RIIFc acts as a TGF? decoy, and can inhibit TGF? pathways. Initially, we created Ad5 based Ad.sT expressing sTGF?RIIFc. To reduce hepatic/systemic toxicity associated with systemic delivery of Ad.sT, we created mHAd.sT, a liver-detargeted virus, by replacing hypervariable regions (HVRs) (1-7) of Ad.sT with Ad48 HVRs. To enhance tumor specificity, we have now created mHAdLyp.sT by introducing LyP-1 peptide, a 9-amino acid long tumor homing-cell peptide, into the HI loop of the mHAd.sT fiber. In this proposal, we will test the hypotheses that systemic administration of mHAdLyp.sT in mice bearing 4T1 triple negative mammary tumors will result in reduced hepatic/systemic toxicity but produce high levels of sTGF?RIIFc and inhibit TGF? pathways. This will alter the tumor microenvironment, induce tumor immunity, and overcome resistance to anti-PD-1 and anti-CTLA-4., and examine the expression profiles of TGF?-1, TGF?-1 regulated genes, and PD-1 and CTLA-4 signaling pathways. We will examine immuno-phenotypes in tumors, peripheral blood and spleen (Aim 1). Next, we will examine mHAdLyp.sT, anti-PD-1 and anti-CTLA-4 combination therapies in mouse tumor models. We will conduct RNA-Seq analysis of the whole transcriptomes, and examine the role of immune activation in mediating the anti-tumor responses (Aim 2). We will test the hypothesis that systemic administration of mHLypAd.sT, in combination with anti-PD-1 and anti- CTLA-4 in mice with pre-established metastases will be effective (Aim 3). To guide us for the combination therapy trials with mHAdLyp.sT, anti-PD-1 and anti-CTLA-4, we will examine human TNBC tumors by Nanostring technology for RNA profiling, and will further examine the TGF?-1 and other relevant biomarkers and TILS in human TNBC tumors. We will also screen the human population for the Ad neutralizing antibodies titers (Aim 4). We believe that our research described here is critical to bring forward our oncolytic virus mHAdLyp.sT targeting TGF? in combination with anti-PD-1 and anti-CTLA-4 for clinical evaluation in TNBC patients.
In recent years there has been a significant interest in developing anti-checkpoint inhibitors such as anti-PD-1 and anti-CTLA-4 for the treatment of breast cancer. Although some triple negative breast cancer patients respond well to these treatments, most women are resistant to this therapy. We are proposing to develop a safe and effective virus in combination with anti-immune checkpoint inhibitors for the treatment of triple negative breast cancer. This will lead to future combination therapy trials with anti-PD-1 and anti-CTLA-4 in breast cancer patients.
