425 Investigation of Wnt ligand signaling regulators as a predictor of Anti-PD-1 response in metastatic melanoma

Background Responses to anti-PD-1 antibodies (aPD1) have changed the therapeutic landscape of metastatic melanoma, however predictive biomarkers of resistance are lacking. Beta-catenin pathway activation has been inversely correlated with tumor-infiltrating T lymphocytes in melanoma as well as several other solid tumors.1 However, activating mutations involving this pathway are rare, implying that the modulation of upstream Wnt ligand/Fzd receptor (Wnt/Fzd) signaling could be a critical regulator of anti-tumor immunity. Indeed, expression of certain Wnt ligands has been associated with inferior responses to checkpoint inhibitor immunotherapy in metastatic melanoma patients.2 In addition, we have further found tumor-derived paracrine and autocrine Wnt ligand signaling to drive dendritic cell tolerization and to be associated with escape from aPD1 therapy in transgenic mouse models.3 4 No studies to date have focused on the impact of the various regulators and components of proximal Wnt/Fzd receptor signaling on resistance to aPD1 therapy in melanoma patients. We therefore developed a unique Wnt/Fzd pathway panel using Nanostring technology to examine alterations in Wnt ligands, their receptors, and regulators as a predictor of aPD1 resistance. Methods To test whether this panel could identify aPD1 resistant patients, Nanostring analysis was performed on archival FFPE tissue specimens of 12 responding (R) and 12 nonresponding (NR) metastatic melanoma patients (pts) taken prior to aPD1 monotherapy. Response was assessed radiographically by week 12 RECIST criteria. Results Several components of both canonical and non-canonical Wnt ligand signaling, including regulators of autocrine/paracrine signaling, were upregulated in aPD1 NR pts compared to R pts (figure 1, table 1). GZMB, CD8, and IFNG were among cytotoxic T cell related genes upregulated in Rs. Upregulation of SFRP2 and DKK2 in NR pts, classically negative feedback regulators of Wnt ligands, are a reflection of enhanced Wnt ligand signaling activity. Conclusions This study supports the importance of paracrine and autocrine Wnt ligand signaling in the regulation of effector T cell responses and aPD1 resistance in cancer. In addition to predicting response to aPD1 checkpoint inhibitor immunotherapy, these findings further suggest that this Wnt signaling panel could serve as a predictive marker of immunologic response to Wnt ligand inhibitors, such as the PORCN inhibitors, which are currently under development. We continue to accrue additional pts to further validate these findings. Future studies will include a comparison of pre-treatment and on-treatment biopsies to evaluate these markers as predictors of adaptive aPD1 resistance. Acknowledgements Holly Dressman, PhD of the Duke Center for Genomic and Computational Biology for her assistance with the Nanostring samples; Jenna Goodwin, Carol Ann Wiggs, and Jennifer Nixon of the Duke Clinical Melanoma Research Team for their assistance with the melanoma tissue acquisition protocol; Tadas Rimkus of Nanostring for his assistance with analysis Trial Registration NCT02694965 Ethics Approval This study was approved by Duke University’s Institutional Review Board, protocol number Pro00059349 Consent Not applicable References Luke JJ, B.R., Spranger S, Sweis RF, Lingen MW, Lengyel E, Zha Y, Gajewski TF. Wnt/Beta-catenin pathway activation correlates with immune exclusion across most human cancers. Journal of Clinical Oncology 2016;34(15). Hugo W, et al. Genomic and transcriptomic features of response to anti-pd-1 therapy in metastatic melanoma. Cell 2016;165(1): p. 35–44. DeVito NC, X.C., Zhao F, Evans KS, Theivanthiran B, Lewicki J, Hoey T, Hurwitz H, Strickler JH, Hanks BA. Paracrine wnt-β-catenin signaling inhibition as a strategy to enhance the efficacy of anti-PD-1 antibody (Ab) therapy in a transgenic model of melanoma. Journal of Clinical Oncology, 2017. 35(no. 15_suppl). Zhao F, et al. Paracrine Wnt5a-beta-Catenin signaling triggers a metabolic program that drives dendritic cell tolerization. Immunity 2018;48(1): p. 147–160 e7.