Noninvasive PET imaging of tumor PD-L1 expression with 64Cu-labeled Durvalumab

Breast cancer (BrCa) ranks as the most prevalent malignant neoplasm affecting women worldwide. The expression of programmed death-ligand 1 (PD-L1) in BrCa has recently emerged as a biomarker for immunotherapy response, but traditional immunohistochemistry (IHC)-based methods are hindered by spatial and temporal heterogeneity. Noninvasive and quantitative PD-L1 imaging using appropriate radiotracers can serve to determine PD-L1 expression in tumors. This study aims to demonstrate the viability of PET imaging with 64Cu-labeled Durvalumab (abbreviated as Durva) to assess PD-L1 expression using a murine xenograft model of breast cancer. Durvalumab, a human IgG1 monoclonal antibody against PD-L1, was assessed for specificity in vitro in two cancer cell lines (MDA-MB-231 triple-negative breast cancer cell line and AsPC-1 pancreatic cancer cell line) with positive and negative PD-L1 expression by flow cytometry. Next, we performed the in vivo evaluation of 64Cu-NOTA-Durva in murine models of human breast cancer by PET imaging and ex vivo biodistribution. Additionally, mice bearing AsPC-1 tumors were employed as a negative control. Tumor uptake was quantified based on a 3D region-of-interest (ROI) analysis of the PET images and ex vivo biodistribution measurements, and the results were compared against conventional IHC testing. The radiotracer uptake was evident in MDA-MB-231 tumors and showed minimal nonspecific binding, corroborating IHC-derived results. The results of the biodistribution showed that the MDA-MB-231 tumor uptake of 64Cu-NOTA-Durva was much higher than 64Cu-NOTA-IgG (a nonspecific radiolabeled IgG). In Conclusion, 64Cu-labeled Durvalumab PET/CT imaging offers a promising, noninvasive approach to evaluate tumor PD-L1 expression.

Breast Cancer Cell-Derived Adenosine Enhances Generation and Suppressor Function of Human Adaptive Regulatory T Cells

Introduction: Adaptive regulatory T cells (Tr1) are induced in the periphery by environmental stimuli. CD73 expression and adenosine (ADO) production by tumor cells may influence Tr1 generation and their immunosuppressive activity. Material and Methods: Tr1 were generated in co-cultures of CD4+CD25neg T cells, autologous immature dendritic cells (iDC), and irradiated ADO-producing CD73+ or non-producing CD73neg breast cancer (BrCa) cell lines (TU). The expression of ectonucleotidases and other surface markers on Tr1 was determined by flow cytometry. Tr1-mediated suppression of proliferation was evaluated in CFSE-based assays. Luciferase-based ATP detection assays and mass spectrometry were used to measure ATP hydrolysis and ADO levels. Cytokine levels were measured by ELISA or Luminex. CD73 expression on tumor cells or T cells in TU tissues was assessed by immunofluorescence. Results: CD73+ TU induced higher numbers of Tr1 cells (p < 0.01) than CD73neg TU. Tr1TU73+ hydrolyzed more exogenous ATP, produced more ADO, and mediated higher suppression than Tr1TU73neg (p < 0.05 for all). ARL67156, an ectonucleotidase inhibitor, and ZM241385, A2A receptor antagonist, reduced suppression of proliferation mediated by Tr1TU73+ cells (p < 0.01). Basal-like primary BrCa cells expressed higher levels of ectonucleotidases and induced more Tr1 than less aggressive primary luminal-like BrCa. Conclusion: BrCa producing ADO (CD73+ TU) favor the induction of Tr1, which expresses CD39 and CD73, hydrolyzes ATP to ADO, and effectively suppresses anti-tumor immunity.

Restoration of GATA4 expression impedes breast cancer progression by transcriptional repression of ReLA and inhibition of NF-κB signaling

There are increasing reports of aberrant expression of GATA4, correlated with oncogenesis and malignant progression in some solid tumors, but whether GATA4 functions as an oncogenic driver or a tumor suppressor in carcinogenesis remains controversial. Because the role and mechanism of GATA4 in breast cancer (BrCa) remain poorly understood, we focused on the expression of GATA4 in BrCa cell lines and tissues and its mechanism in breast oncogenesis. Semiquantitative real-time polymerase chain reaction (RT-PCR), quantitative RT-PCR, Western blot analysis, and immunohistochemistry were used to detect expression of GATA4 in BrCa cell lines and adjacent breast tissues. Methylation statuses of the GATA4 promoter were studied using methylation-specific PCR in BrCa cell lines.The effects of GATA4 on proliferation, invasion, and cell cycle were also analyzed. Compared with adjacent breast tissue, GATA4 expression in BrCa tissue and cell lines was obviously lower and low expression levels of GATA4 predicted poor outcome. Methylation of GATA4 occurred in almost all of BrCa cell lines . GATA4 overexpression decreased viability, invasion, migration, and epithelial-to-mesenchymal transition of MB-231 and BT549 cells, and markedly induced cell cycle arrest and apoptosis. Exogenous expression GATA4 accompanied a significant alteration of MMP2, MMP3, E-cadherin, and N-cadherin expression and induction of the caspase-8 pathway. Moreover, GATA4 could directly repress RelA (p65) transcription, reduce the nuclear phosphorylation-p65 and upregulate inhibitor kappa B expression. Altogether, GATA4 plays a tumor-suppressive role via repression of NF-κB signaling in BrCa cells. Our findings suggest that GATA4 is a potential prognostic biomarker and gene therapeutic target for human BrCa.