Background
FDA approval of immune checkpoint inhibitors (ICIs) as a treatment for head and neck squamous cell carcinoma (HNSCC) confirmed the power of harnessing the immune system for HNSCC therapy. As response rates remain low, research aimed at defining new therapeutic targets that can improve ICI therapy outcomes. Among novel therapeutic strategies, AZD1775 selectively inhibits the WEE1 kinase, causing premature mitosis and tumor cell death; this drug is being tested in clinical trials for patients with a variety of cancers including HNSCC. AZD1775 was recently shown to augment the efficacy of ICIs and other immune-targeted therapies in several models of solid tumors.
Methods
To study the immunomodulatory potential of AZD1775 in HPV+ HNSCC, we used the syngeneic HPV+ mEER model driven by HPV16 E6, E7 and mutated Ras. We evaluated the antitumor efficacy of AZD1775 in wild-type immunocompetent C57BL/6 mice, as well as in NSG mice which lack adaptive immunity. Noting that HPV16 E7 inhibits STING function, and that innate immune signaling via the dsDNA-sensing cGAS/STING pathway is a mechanism of AZD1775-induced antitumor immunity, we also evaluated AZD1775’s antitumor efficacy in STING-deficient C57BL/6 mice. Follow-up immunophenotyping approaches including single-cell whole transcriptome sequencing (scRNAseq), flow cytometry and bulk mRNA expression analysis using the Nanostring nCounter immune profiling panel of mEER tumors from wild-type C57BL/6 treated ± AZD1775.
Results
Our preliminary data shows that AZD1775 monotherapy caused tumor regression and prolonged survival in the immunocompetent wild-type mEER-bearing mice but not in mice lacking innate or adaptive immunity. We also observed a selective increase in cytotoxic CD8+ T cell and NK cell accumulation in AZD1775-treated tumors and activated several immune checkpoints. Our bulk transcriptomic analysis revealed an upregulation in genes involved in interferon gamma-induced genes as well as genes involved in lymphovascular endothelial cells (LECs) in AZD1775-treated tumors. Our scRNAseq analysis revealed an expansion of the LEC compartment in the AZD1775-treated tumors suggesting a role for lymphatic vasculature remodeling in promoting immune infiltration and surveillance following WEE1 inhibition. Ongoing studies are dissecting how WEE1 inhibition modulates tumor lymph vasculature as a means to promoting antitumor immunity against HPV+ HNSCCs.
Conclusions
Our data suggests that WEE1 inhibition can remodel the tumor lymphatic vasculature to promote antitumor immunity against HPV+ HNSCC tumors. A mechanistic understanding of how cell cycle checkpoint inhibition and HPV infection alter the larger tumor microenvironment may help inform the development of immunomodulatory therapy regimens that maximize the antitumor efficacy of WEE1 inhibition.
Acknowledgements
This research was supported by a Technology Pilot Award from the Fred Hutch Pathogen Associated Malignancies Integrated Research Center and a k99DE030194 from the National Institute of Dental and Craniofacial Research to Ahmed Diab.