Supplemental Figure S2 from Treatment-Induced Tumor Cell Apoptosis and Secondary Necrosis Drive Tumor Progression in the Residual Tumor Microenvironment through MerTK and IDO1
posted on 2023-03-31, 02:23authored byThomas A. Werfel, David L. Elion, Bushra Rahman, Donna J. Hicks, Violeta Sanchez, Paula I. Gonzales-Ericsson, Mellissa J. Nixon, Jamaal L. James, Justin M. Balko, Peggy A. Scherle, Holly K. Koblish, Rebecca S. Cook
Supplemental Figure S2. Schematic representation of treatment groups and experimental timeline to measure the impact of PtdSer liposomes on the TME of 4T1 mouse mammary tumors IHC to detect CD3, and FoxP3 in tumors collected on treatment day 7. Quantitation of the number of positive cells per 200X field is shown. Each data point is the average of 5 random fields per tumor, midlines are the average of N = 3 samples, {plus minus}S.D. P values, Student's unpaired 2-tailed T-test.
Funding
NIH
CTSA
National Center for Advancing Translational Sciences
History
ARTICLE ABSTRACT
Efferocytosis is the process by which apoptotic cells are cleared from tissue by phagocytic cells. The removal of apoptotic cells prevents them from undergoing secondary necrosis and releasing their inflammation-inducing intracellular contents. Efferocytosis also limits tissue damage by increasing immunosuppressive cytokines and leukocytes and maintains tissue homeostasis by promoting tolerance to antigens derived from apoptotic cells. Thus, tumor cell efferocytosis following cytotoxic cancer treatment could impart tolerance to tumor cells evading treatment-induced apoptosis with deleterious consequences in tumor residual disease. We report here that efferocytosis cleared apoptotic tumor cells in residual disease of lapatinib-treated HER2+ mammary tumors in MMTV-Neu mice, increased immunosuppressive cytokines, myeloid-derived suppressor cells (MDSC), and regulatory T cells (Treg). Blockade of efferocytosis induced secondary necrosis of apoptotic cells, but failed to prevent increased tumor MDSCs, Treg, and immunosuppressive cytokines. We found that efferocytosis stimulated expression of IFN-γ, which stimulated the expression of indoleamine-2,3-dioxegenase (IDO) 1, an immune regulator known for driving maternal-fetal antigen tolerance. Combined inhibition of efferocytosis and IDO1 in tumor residual disease decreased apoptotic cell- and necrotic cell-induced immunosuppressive phenotypes, blocked tumor metastasis, and caused tumor regression in 60% of MMTV-Neu mice. This suggests that apoptotic and necrotic tumor cells, via efferocytosis and IDO1, respectively, promote tumor ‘homeostasis’ and progression.
These findings show in a model of HER2+ breast cancer that necrosis secondary to impaired efferocytosis activates IDO1 to drive immunosuppression and tumor progression.