Background A deep understanding of the spatial distribution of immune cells and cell-to-cell interactions within the tumor microenvironment (TME) is critical for unraveling the interplay between immunity and tumor growth, especially in the context of variable responses to immune checkpoint blockade (ICB) therapy

Methods Here, we report the application of multiplex imaging and new computational methods for extraction of spatial patterns within the TME for the analysis of biopsy samples of recurrent ovarian cancer patients enrolled in a phase II study of the PARP inhibitor olaparib and anti-PD-L1 durvalumab (NCT02484404).¹ Paired fresh tumor biopsies (collected at baseline and cycle 1 day 15, C1D15) were available in 12 patients. Response was evaluated by RECIST v1.1. Clinical benefit was defined as a complete or partial response, or stable disease for ³ 4 months. We performed 21-plex iterative bleaching extends multiplexing (IBEX) of sections from formalin-fixed paraffin-embedded tumor biopsies that identified cytokeratin, CD68, CD163, CD3, CD4, CD8, PD-1, Foxp3, VEGFA, VEGFC, CD34, Lyve-1, a-SMA, CD15, CD14, HLA-DR, CD11b, CD11c, CD20, and CXCR5.

Results Using a novel pixel-based analytical framework called SPACE, we found that at baseline, there was more co-occurrence of monocytic-myeloid suppressor cells (M-MDSCs) with M2 macrophages in patients with no clinical benefit (NCB group, n=7) compared to patients with clinical benefit (CB group, n= 5; p=0.0253). In contrast, co-localization of M1 macrophages and CD4 T cells was observed in the CB group (p=0.0377). Object-based histocytometry showed more suppressor monocytes and granulocytic MDSCs (gMDSCs) at C1D15 in the NCB group (n=7) relative to the CB group (n=6; p=0.03 and p=0.04, respectively). At C1D15, pixel-based analysis showed higher VEGFA signal in the NCB group (p=0.0147) and more effector CD8 T cells in the CB group (p=0.0087).

Conclusions Collectively, these results provide new insights into the relationship between the spatial distribution of immune cells in the TME and the clinical benefit of ICB therapy in recurrent ovarian cancer, providing a lead towards eventual personalized predictions of immunotherapy response or resistance.

Acknowledgements This work was supported by the Intramural Research program of NIAID, NIH.

Trial Registration Yes, the abstract is related to a clinical trial; the number registration is the one that I put in the abstract (NCT02484404)

Reference

1. Lampert EJ, et al. Combination of PARP inhibitor olaparib, and PD-L1 inhibitor durvalumab, in recurrent ovarian cancer: a proof-of-concept phase II study. Clin Cancer Res 2020;26:4268–4279.

Ethics Approval The study has been conducted in accordance with ethical principles that have their origin in the Declaration of Helsinki and are consistent with the International Council on Harmonization guidelines on Good Clinical Practice, all applicable laws and regulatory requirements, and all conditions required by a regulatory authority and/or institutional review board. The study protocol was approved by the Institutional Review Board of the Center for Cancer Research, National Cancer Institute.

Consent All patients, including 13 participants in this research project, provided written informed consent before enrolment and on using their samples for research.