Chimeric Antigen Receptor T Cell Therapy Targeting Epithelial Cell Adhesion Molecule in Gastric Cancer: Mechanisms of Tumor Resistance

Epithelial cell adhesion molecule (EpCAM) is a tumor-associated antigen that is frequently overexpressed in various carcinomas. We have developed chimeric antigen receptor (CAR) T cells specifically targeting EpCAM for the treatment of gastric cancer. This study sought to unravel the precise mechanisms by which tumors evade immune surveillance and develop resistance to CAR T cell therapy. Through a combination of whole-body CAR T cell imaging and single-cell multiomic analyses, we uncovered intricate interactions between tumors and tumor-infiltrating lymphocytes (TILs). In a gastric cancer model, tumor-infiltrating CD8 T cells exhibited both cytotoxic and exhausted phenotypes, while CD4 T cells were mainly regulatory T cells. A T cell receptor (TCR) clonal analysis provided evidence of CAR T cell proliferation and clonal expansion within resistant tumors, which was substantiated by whole-body CAR T cell imaging. Furthermore, single-cell transcriptomics showed that tumor cells in mice with refractory or relapsing outcomes were enriched for genes involved in major histocompatibility complex (MHC) and antigen presentation pathways, interferon-γ and interferon-α responses, mitochondrial activities, and a set of genes (e.g., CD74, IDO1, IFI27) linked to tumor progression and unfavorable disease prognoses. This research highlights an approach that combines imaging and multiomic methodologies to concurrently characterize the evolution of tumors and the differentiation of CAR T cells

[¹⁸F]Fluoroethyltriazolyl Monocyclam Derivatives as Imaging Probes for the Chemokine Receptor CXCR4

Determining chemokine receptor CXCR4 expression is significant in multiple diseases due to its role in promoting inflammation, cell migration and tumorigenesis. [68Ga]Pentixafor is a promising ligand for imaging CXCR4 expression in multiple tumor types, but its utility is limited by the physical properties of 68Ga. We screened a library of >200 fluorine-containing structural derivatives of AMD-3465 to identify promising candidates for in vivo imaging of CXCR4 expression by positron emission tomography (PET). Compounds containing fluoroethyltriazoles consistently achieved higher docking scores. Six of these higher scoring compounds were radiolabeled by click chemistry and evaluated in PC3-CXCR4 cells and BALB/c mice bearing bilateral PC3-WT and PC3-CXCR4 xenograft tumors. The apparent CXCR4 affinity of the ligands was relatively low, but tumor uptake was CXCR4-specific. The tumor uptake of [18F]RPS-534 (7.2 ± 0.3 %ID/g) and [18F]RPS-547 (3.1 ± 0.5 %ID/g) at 1 h p.i. was highest, leading to high tumor-to-blood, tumor-to-muscle, and tumor-to-lung ratios. Total cell-associated activity better predicted in vivo tumor uptake than did the docking score or apparent CXCR4 affinity. By this metric, and on the basis of their high yielding radiosynthesis, high tumor uptake, and good contrast to background, [18F]RPS-547, and especially [18F]RPS-534, are promising 18F-labeled candidates for imaging CXCR4 expression

Detection of ephrin-B2 expression in human tissue arrays.

<p>(A&B) Immunostaining of ephrin-B2 expression in human tumor tissue arrays using EC8. Control denotes immunostaining without EC8 as a primary antibody. Tumor and stromal cells were indicated with arrowhead and arrow, respectively. Scale bar = 20 µm. PAC = Papillary Adenocarcinoma; AC = Adenocarcinoma; BR = Bronchus; AL = Alveoli; SC = Squamous Cell Carcinoma; SAC = Serous Adenocarcinoma. IDC = Nonspecific Infiltrating Duct Carcinoma. (C) Immunofluorescence staining on human colon tumor tissue demonstrating that EC8 (red) detects ephrin-B2 expressions in both cancer cells and tumor-associated vasculature (green). Blow up views of the two areas indicated with dashed box are shown in the right panel. Scale bar = 100 µm.</p

Detection of ephrin-B2 expression in human cancer cell lines and tumor xenograft in mice.

<p>(A) Flow cytometry measurements of EC8 binding to COLO205 and HCT116 cells (solid line) in comparison to the isotype control (shaded area). CHO cells with no ephrin-B2 expression were also included for comparison. (B) RT-PCR detection of ephrin-B2 expression in different cell lines. (C) Immunostaining of ephrin-B2 on human colon cancer xenografted in mice. Control denotes immunostaining without EC8 as a primary antibody. Tumor and stromal cells were indicated with arrowhead and arrow, respectively. Circle indicates murine endothelium stained with EC8. Scale bar = 20 µm.</p

¹⁸F‑Positron Emitting/Trimethine Cyanine-Fluorescent Contrast for Image-Guided Prostate Cancer Management

[^18/19F]-<b>4</b>, an anionic GCPII/PSMA inhibitor for image-guided intervention in prostate cancer, is described. [¹⁹F]-<b>4</b> is radiolabeled with a radiochemical yield that is ≥27% and a molar activity of 190 ± 50 mCi/μmol in a <1 h, one-step, aqueous isotopic exchange reaction. [¹⁹F]-<b>4</b> allows PSMA expression to be imaged by fluorescence (FL) and [¹⁸F]-PET. PC3-PIP (PSMA-positive, EC₅₀ = 6.74 ± 1.33 nM) cancers are specifically delineated in mice that bear 3 million (18 mg) PC3-PIP and PC3 (control, PSMA-negative) cells. Colocalization of [^18/19F]-<b>4</b> PET, fluorescence, scintillated biodistribution, and PSMA expression are observed