Background
Leukemic inhibitory factor (LIF) is an IL-6 family member which has pleiotropic effects on tumour, stromal and immune cells. LIF can alter macrophage phenotype and chemokine release in the TME, so pharmacological targeting of LIF may enhance the activity of T-cell checkpoint inhibitors. CAFs express LIF receptor (LIFR) and produce LIF, therefore LIF targeting may alter CAF biology. AZD0171 decreases bioactive LIF in the TME and is being evaluated in a Ph2 clinical trial in pancreatic cancer in combination with chemotherapy and aPDL1 in NCT04999969.
Methods
Monocytes were isolated from donated human blood and treated with M-CSF and tumour conditioned media from the MDA-MB-231 cell line in the presence or absence of AZD0171 or isotype control antibody to generate tumour associated macrophages (TAMs). Murine AZD0171 (mAZD0171) was tested as a monotherapy and in combination with αPDL1 in the CT-26 tumour model, with follow up studies combining mAZD0171 + αPDL1 with taxane-based chemotherapies. mAZD0171 was also tested in the D2A1-m2 breast orthoptic mouse model as monotherapy and in combination with αPDL1.
Results
AZD0171 decreases LIF mRNA and decreases bioactive LIF levels in the supernatant from TAMs during conditioning. This was associated with an alteration of transcripts and surface marker expression in TAMs in vitro. AZD0171 decreases bioactive LIF abundance in supernatant from a lung derived CAF line and was associated with a decrease in pro-tumorigenic factors. In the CT-26 model, mAZD0171 lowered bioactive LIF in tumour lysates and altered myeloid abundance and phenotype at both an RNA and protein level. When combined with αPDL1 in the CT-26 model, mAZD0171 promoted an anti-tumour TAM phenotype, increased T cell infiltration and enhanced response to treatment. This was also observed with a combination of mAZD0171 with chemotherapy (docetaxel) and αPDL1.
In the CAF rich D2A1-m2 orthotopic model, mAZD0171 in combination with αPDL1 resulted in significant transcriptomic changes that were not observed in the monotherapy arms; including alterations in CAF and myeloid populations and functional pathways. These changes were associated with an increase in CD8 T cell infiltration, measured using IHC, and a decrease in tumour volume.
Conclusions
AZD0171 monotherapy can alter TAM and CAF phenotype both in vitro and in vivo. In combination with chemotherapy and αPDL1 this is associated with increased T infiltration and tumour growth inhibition. Overall, this indicates agents which can target the TME to influence myeloid and CAF populations have potential utility in combination with standard of care.
Ethics Approval
This study was conducted in accordance with international, national, and institutional guidelines as well as all relevant laws and regulations regarding research involving animals. All animal protocols were approved by the institutional AWERB (Animal Welfare and Ethical Review Board) as well as by the UK Govt. Home Office under project licence number PP5259481.