Oral Presentation Asia-Pacific Vaccine and Immunotherapy Congress 2024

Investigating regulators of CXCL9 and CXCL10 expression to improve T cell infiltration and immunotherapy responses in solid tumors. (#7)

Emily B Derrick 1 2 , Imran G House 1 2 , Junyun Lai 1 2 , Phillip K Darcy 1 2 , Paul A Beavis 1 2
  1. Peter MacCallum Cancer Centre, Melbourne, VICTORIA, Australia
  2. The Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, VIC, Australia

Immune checkpoint blockade (ICB) has revolutionised the treatment of numerous cancer types, including melanoma and non-small cell lung carcinoma. ICB targets immune-inhibitory molecules on the surface of T cells, unleashing their anti-tumour potential. Despite ICB’s success, a high frequency of patients fail to respond to this therapy. A key limiting factor to ICB responses is the number of T cells that infiltrate the tumour microenvironment. T cell infiltration in the context of ICB has been shown to be dependent on chemoattractant molecules CXCL9 and CXCL10. The expression of these chemokines is also predictive of a positive response to ICB across multiple cancer types, highlighting their importance in ICB efficacy (Litchfield et al, Cell 2021). We have previously demonstrated that these chemokines are predominantly produced by intratumoral macrophages (House et al. Clinical Cancer Research 2020). Therefore, we aimed to identify genes that we could target to enhance CXCL9/10 production in macrophages as a strategy to improve T cell infiltration and ICB responses in solid tumors. To this end, we performed CRISPR/Cas9 screening on a macrophage cell line to identify novel regulators of CXCL9 and CXCL10. To screen for secreted factors, we utilised a CRISPR-HDR technique we have previously validated (House, Derrick et al. Cell Reports 2023) to generate a macrophage cell line that expressed GFP and BFP as a bona fide readout of CXCL9/10 production. This screen identified PTPN2 as a key negative regulator of both CXCL9 and CXCL10 production. With PTPN2 inhibitors currently in clinical trials (Baumgertner et al. Nature 2023), we sought to define how PTPN2 depletion in macrophages might play a role in anti-tumor immunity. PTPN2 deletion enhanced CXCL9/10 production by primary murine/human macrophages in vitro. Myeloid-specific depletion of PTPN2 in vivo improved CXCL9 expression in both intratumoral macrophages and dendritic cells, and improved T cell infiltration when combined with ICB in a murine breast cancer model. Importantly, T cell infiltration was improved without elevating Treg numbers  This work has uncovered a novel role for PTPN2 inhibition through the elevation of chemokine production by macrophages. It also provides further rationale to combine PTPN2 inhibitors with ICB for improved responses to immunotherapy.

  1. Litchfield, K., Reading, J.L., Puttick, C., Thakkar, K., Abbosh, C., Bentham, R., Watkins, T.B., Rosenthal, R., Biswas, D., and Rowan, A. (2021). Meta-analysis of tumor-and T cell-intrinsic mechanisms of sensitization to checkpoint inhibition. Cell 184, 596-614. e514
  2. House, I.G., Savas, P., Lai, J., Chen, A.X., Oliver, A.J., Teo, Z.L., Todd, K.L., Henderson, M.A., Giuffrida, L., and Petley, E.V. (2020). Macrophage-derived CXCL9 and CXCL10 are required for antitumor immune responses following immune checkpoint blockade. Clinical Cancer Research 26, 487-504.
  3. House, I.G., Derrick, E.B., Sek, K., Chen, A.X.Y., Li, J., Lai, J., Todd, K.L., Munoz, I., Michie, J., Chan, C.W., et al. (2023). CRISPR-Cas9 screening identifies an IRF1-SOCS1-mediated negative feedback loop that limits CXCL9 expression and antitumor immunity. Cell Rep 42, 113014. 10.1016/j.celrep.2023.113014
  4. Baumgartner, C.K., Ebrahimi-Nik, H., Iracheta-Vellve, A., Hamel, K.M., Olander, K.E., Davis, T.G.R., McGuire, K.A., Halvorsen, G.T., Avila, O.I., Patel, C.H., et al. (2023). The PTPN2/PTPN1 inhibitor ABBV-CLS-484 unleashes potent anti-tumour immunity. Nature 622, 850-862. 10.1038/s41586-023-06575-7.