Time-resolved single-cell transcriptomics defines immune trajectories in glioblastoma

Deciphering the cell-state transitions underlying immune adaptation across time is fundamental for advancing biology. Empirical in vivo genomic technologies that capture cellular dynamics are currently lacking. We present Zman-seq, a single-cell technology recording transcriptomic dynamics across time by introducing time stamps into circulating immune cells, tracking them in tissues for days. Applying Zman-seq resolved cell-state and molecular trajectories of the dysfunctional immune microenvironment in glioblastoma. Within 24 hours of tumor infiltration, cytotoxic natural killer cells transitioned to a dysfunctional program regulated by TGFB1 signaling. Infiltrating monocytes differentiated into immunosuppressive macrophages, characterized by the upregulation of suppressive myeloid checkpoints Trem2, Il18bp, and Arg1, over 36 to 48 hours. Treatment with an antagonistic anti-TREM2 antibody reshaped the tumor microenvironment by redirecting the monocyte trajectory toward pro-inflammatory macrophages. Zman-seq is a broadly applicable technology, enabling empirical measurements of differentiation trajectories, which can enhance the development of more efficacious immunotherapies.

Cellular Plasticity and Tumor Microenvironment in Gliomas: The Struggle to Hit a Moving Target

Brain tumors encompass a diverse group of neoplasias arising from different cell lineages. Tumors of glial origin have been the subject of intense research because of their rapid and fatal progression. From a clinical point of view, complete surgical resection of gliomas is highly difficult. Moreover, the remaining tumor cells are resistant to traditional therapies such as radio- or chemotherapy and tumors always recur. Here we have revised the new genetic and epigenetic classification of gliomas and the description of the different transcriptional subtypes. In order to understand the progression of the different gliomas we have focused on the interaction of the plastic tumor cells with their vasculature-rich microenvironment and with their distinct immune system. We believe that a comprehensive characterization of the glioma microenvironment will shed some light into why these tumors behave differently from other cancers. Furthermore, a novel classification of gliomas that could integrate the genetic background and the cellular ecosystems could have profound implications in the efficiency of current therapies as well as in the development of new treatments.

Functional Blockade of E-Selectin in Tumor-Associated Vessels Enhances Anti-Tumor Effect of Doxorubicin in Breast Cancer

Chemotherapy is a mainstay of treatment for solid tumors. However, little is known about how therapy-induced immune cell infiltration may affect therapy response. We found substantial CD45⁺ immune cell density adjacent to E-selectin expressing inflamed vessels in doxorubicin (DOX)-treated residual human breast tumors. While CD45 level was significantly elevated in DOX-treated wildtype mice, it remained unchanged in DOX-treated tumors from E-selectin null mice. Similarly, intravenous administration of anti-E-selectin aptamer (ESTA) resulted in a significant reduction in CD45⁺ immune cell density in DOX-treated residual tumors, which coincided with a delay in tumor growth and lung metastasis in MMTV-pyMT mice. Additionally, both tumor infiltrating T-lymphocytes and tumor associated-macrophages were skewed towards T_H2 in DOX-treated residual breast tumors; however, ESTA suppressed these changes. This study suggests that DOX treatment instigates de novo intratumoral infiltration of immune cells through E-selectin, and functional blockade of E-selectin may reduce residual tumor burden as well as metastasis through suppression of T_H2 shift.

TRIM59 loss in M2 macrophages promotes melanoma migration and invasion by upregulating MMP-9 and Madcam1

The culture supernatant from macrophages overexpressing TRIM59 has a cytotoxic effect on melanoma, but the mechanism remains unclear. To investigate whether deletion of TRIM59 in macrophages affects the metastatic potential of melanoma cells, we polarized control and TRIM59-deficient bone marrow-derived macrophages to the M2 phenotype and collected the respective conditioned media (CM). Exposure to CM from TRIM59^-/--M2 cultures significantly promoted migration and invasion by B16-F0 and B16-F10 cells. Cytokine profiling indicated a ~15-fold increase in TNF-α production in CM from TRIM59^-/--M2 cultures, and neutralizing TNF-α activity abrogated the referred stimulatory effects on cell motility. Transcriptome analysis revealed significant upregulation of MMP-9 and Madcam1 in melanoma cells exposed to TRIM59^-/--M2 CM. Inhibitory experiments determined that these changes were also TNF-α-dependent and mediated by activation of ERK signaling. Independent knockdown of MMP9 and Madcam1 in B16-F10 cells impeded epithelial-mesenchymal transition and inhibited subcutaneous tumor growth and formation of metastatic lung nodules in vivo. These data suggest TRIM59 expression attenuates the tumor-promoting effect of tumor-associated macrophages, most of which resemble the M2 phenotype. Moreover, they highlight the relevance of TRIM59 in macrophages as a potential regulator of tumor metastasis and suggest TRIM59 could serve as a novel target for cancer immunotherapy.