PROJECT SUMMARY
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 TGFβ 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 sTGFβRIIFc (soluble TGFβ receptor II
fused with human IgG Fc). sTGFβRIIFc acts as a TGFβ decoy, and can inhibit TGFβ pathways. Initially, we
created Ad5 based Ad.sT expressing sTGFβRIIFc. 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
sTGFβRIIFc and inhibit TGFβ 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 TGFβ-1,
TGFβ-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 TGFβ-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 TGFβ in combination with anti-PD-1 and anti-CTLA-4 for clinical evaluation in TNBC
patients.
