Alessandro Canella

Dickkopf-1 (DKK1) is a 266-amino-acid secreted glycoprotein originally identified as a high-affinity antagonist of the canonical Wnt/β-catenin signaling pathway and has emerged as a complex regulator in oncology. While historically considered as a tumor suppressor due to its ability to abrogate Wnt-driven proliferation, recent discoveries highlight a paradoxical pro-oncogenic role across various malignancies. The molecular mechanisms by which DKK1 promotes tumor progression, metastasis, and immune evasion are driven by its interaction with cell-surface receptors, specifically LRP5/6 and CKAP4. The DKK1-CKAP4 axis independently activates PI3K/AKT signaling, facilitating epithelial–mesenchymal transition (EMT), chemoresistance, and the formation of osteolytic bone lesions. Furthermore, DKK1 serves as a critical orchestrator of the tumor microenvironment (TME) by driving comprehensive immune reprogramming. It mediates the recruitment of myeloid-derived suppressor cells (MDSCs) and inactivates cytotoxic CD8⁺ T cells and natural killer (NK) cells, thereby fostering an immunosuppressive tumor microenvironment and resistance to checkpoint inhibitors. Interestingly, cancer-associated fibroblasts (CAFs) are a primary source of DKK1 in the stroma, where they facilitate immune evasion. Clinically, elevated circulating DKK1 levels correlate with advanced disease stages, increased metastatic potential, and poor overall survival in solid and hematological tumors. When used in combination with established biomarkers, serum DKK1 levels demonstrate significant utility for early detection and therapeutic monitoring. Given its intricate impact on malignancy, DKK1 has become a promising therapeutic target, with ongoing clinical trials investigating neutralizing antibodies such as DKN-01 to disrupt its oncogenic and immunosuppressive signaling. Understanding the context-dependent nature of DKK1 signaling remains essential for refining its application as both a biomarker and a component of emerging precision immunotherapy strategies. By prioritizing the literature from the last decade, this review characterizes DKK1 as a key mediator of tumor progression and immune reprogramming, while assessing its clinical potential as a biomarker and therapeutic target.

High-grade gliomas (HGGs) are among the most aggressive brain tumors in pediatric, adolescent, and young adult (AYA) cancer patients, with a median survival of 12–15 months post-diagnosis. Their poor prognosis is driven by a highly immunosuppressive tumor immune microenvironment (TIME), which inhibits cytotoxic immune infiltration and anti-tumor response. This study investigated the involvement of long non-coding RNAs (lncRNAs) in shaping the immune phenotype of HGGs using two murine models: RCAS-PDGFb representing an immunosuppressive TME, and RCAS-BRAF V600E characterized by a signature more consistent with a pro-inflammatory TME. Transcriptomic analysis of tumor-infiltrating immune cells identified distinct lncRNA signatures associated with immunosuppressive and pro-inflammatory TMEs. Single-cell RNA sequencing and spatial transcriptomics supported context-dependent expression of these lncRNAs in high-grade glioma-associated immune cells, such as myeloid, T, and NK cells, and revealed their spatial distribution within the glioblastoma (GBM) TME. Several lncRNAs were enriched at the tumor edge and within necrotic regions in GBM patient samples, correlating with immunosuppression reprogramming and immune evasion mechanisms. These findings highlight specific immunomodulatory lncRNAs as potential players in the immunosuppressive glioma TME, and likely candidates for future studies aimed at developing novel therapeutic strategies to overcome immune suppression and improve clinical outcomes.

Despite promising results shown in hematologic tumors, immunotherapies for the treatment of solid tumors have mostly failed so far. The immunosuppressive tumor microenvironment and phenotype of tumor infiltrating macrophages are among the more prevalent reasons for this failure. Tumor associated macrophages (TAMs, M2-macrophages) are circulating myeloid cells recruited to the local tumor microenvironment, and together with regulatory T cells (T-regs), are reprogrammed to become immune suppressive. This results in the inactivation or hampered recruitment of cytotoxic CD8 + T and Natural Killer (NK) cells. Recently, attempts have been made to try to leverage specific myeloid functions and properties, including their ability to reach the TME and to mediate the phagocytosis of cancer cells. Additionally, myeloid cells have been used for drug delivery and reprogramming the tumor microenvironment in cancer patients. This approach, together with the advancements in genome editing, paved the way for the development of novel cell-mediated immunotherapies. This article focuses on the latest studies that detail the therapeutic properties of genetically engineered or pharmacologically modulated myeloid cells in cancer preclinical models, limitations, pitfalls, and evaluations of these approaches in patients with cancer.