Wenqun Zhong

Abstract The desmoplastic stroma in solid tumors presents a formidable challenge to immunotherapies that rely on endogenous or adoptively transferred T cells, however, the mechanisms are poorly understood. To define mechanisms involved, here we treat established desmoplastic pancreatic tumors with CAR T cells directed to fibroblast activation protein (FAP), an enzyme highly overexpressed on a subset of cancer-associated fibroblasts (CAFs). Depletion of FAP + CAFs results in loss of the structural integrity of desmoplastic matrix. This renders these highly treatment-resistant cancers susceptible to subsequent treatment with a tumor antigen (mesothelin)-targeted CAR T cells and to anti-PD-1 antibody therapy. Mechanisms include overcoming stroma-dependent restriction of T cell extravasation and/or perivascular invasion, reversing immune exclusion, relieving T cell suppression, and altering the immune landscape by reducing myeloid cell accumulation and increasing endogenous CD8 + T cell and NK cell infiltration. These data provide strong rationale for combining tumor stroma- and malignant cell-targeted therapies to be tested in clinical trials.

The development of head and neck squamous cell carcinoma (HNSCC) is closely associated with inflammation. Tumor associated macrophages (TAMs), the largest population of inflammatory cells in the tumor stroma, serve an important role in accelerating cancer progression. The present study aimed to investigate the role of TAMs in the metastasis of HNSCC. TAM biomarkers and epithelial to mesenchymal transition (EMT)‑associated proteins were detected using immunohistochemical and immunofluorescence staining in HNSCC. Then, direct and indirect co‑culture systems of TAMs and HNSCC cells were established. The EMT‑associated proteins and associated signaling pathways in HNSCC cells of the co‑culture system were measured by reverse transcription‑quantitative polymerase chain reaction and western blotting. Finally, hierarchical clustering was performed to analyze associations among TAM biomarkers, epidermal growth factor receptor (EGFR), activated extracellular signal‑regulated protein kinase 1/2 (ERK1/2) and EMT‑associated proteins in HNSCC tissues. The results indicated that the expression of EMT‑associated proteins was positively associated with M2 macrophage biomarkers in HNSCC tissues. Cal27 cells were isolated from the co‑culture system by fluorescence‑activated cell sorting, and it was identified that E‑cadherin was downregulated in Cal27 cells, while Vimentin and Slug were upregulated. Furthermore, the results indicated that EGF released by M2 macrophages in the co‑culture served an important role by activating ERK1/2. The correlation and cluster analyses indicated that activated ERK1/2 was positively correlated with cluster of differentiation‑163, EGFR, Vimentin and Slug. This suggested that TAMs may induce the EMT of cancer cells by activating the EGFR/ERK1/2 signaling pathway in HNSCC, which may be a promising approach to suppressing cancer metastasis.