Several preclinical studies have demonstrated that certain cytotoxic drugs enhance metastasis, but the importance of host responses triggered by chemotherapy in regulating cancer metastasis has not been fully explored. Here, we showed that multidose gemcitabine (GEM) treatment promoted breast cancer lung metastasis in a transgenic spontaneous breast cancer model. GEM treatment significantly increased accumulation of CCR2 ⁺ macrophages and monocytes in the lungs of tumor-bearing as well as tumor-free mice. These changes were largely caused by chemotherapy-induced reactive myelopoiesis biased toward monocyte development. Mechanistically, enhanced production of mitochondrial ROS was observed in GEM-treated BM Lin ⁻ Sca1 ⁺ c-Kit ⁺ cells and monocytes. Treatment with the mitochondria targeted antioxidant abrogated GEM-induced hyperdifferentiation of BM progenitors. In addition, GEM treatment induced upregulation of host cell–derived CCL2, and knockout of CCR2 signaling abrogated the pro-metastatic host response induced by chemotherapy. Furthermore, chemotherapy treatment resulted in the upregulation of coagulation factor X (FX) in lung interstitial macrophages. Targeting activated FX (FXa) using FXa inhibitor or F10 gene knockdown reduced the pro-metastatic effect of chemotherapy. Together, these studies suggest a potentially novel mechanism for chemotherapy-induced metastasis via the host response–induced accumulation of monocytes/macrophages and interplay between coagulation and inflammation in the lungs.

Background: The role of B cells in antitumor immunity remains controversial, with studies suggesting the protumor and antitumor activity. This controversy may be due to the heterogeneity in B cell populations, as the balance among the subtypes may impact tumor progression. The immunosuppressive regulatory B cells (Breg) release interleukin 10 (IL-10) but only represent a minor population. Additionally, tumor-specific antibodies (Abs) also exhibit antitumor and protumor functions dependent on the Ab isotype. Transcription factor c-Maf has been suggested to contribute to the regulation of IL-10 in Breg, but the role of B cell c-Maf signaling in antitumor immunity and regulating Ab responses remains unknown. Methods: Conditional B cell c-Maf knockout (KO) and control mice were used to establish a KPC pancreatic cancer model and B16.F10 melanoma model. Tumor progression was evaluated. B cell and T cell phenotypes were determined by flow cytometry, mass cytometry, and cytokine/chemokine profiling. Differentially expressed genes in B cells were examined by using RNA sequencing (RNA-seq). Peripheral blood samples were collected from healthy donors and patients with melanoma for B cell phenotyping. Results: Compared with B cells from the spleen and lymph nodes (LN), B cells in the pancreas exhibited significantly less follicular phenotype and higher IL-10 production in naïve mice. c-Maf deficiency resulted in a significant reduction of CD9⁺ IL-10-producing Breg in the pancreas. Pancreatic ductal adenocarcinoma (PDAC) progression resulted in the accumulation of circulating B cells with the follicular phenotype and less IL-10 production in the pancreas. Notably, B cell c-Maf deficiency delayed PDAC tumor progression and resulted in proinflammatory B cells. Further, tumor volume reduction and increased effective T cells in the tumor-draining LN were observed in B cell c-Maf KO mice in the B16.F10 melanoma model. RNA-seq analysis of isolated B cells revealed that B cell c-Maf signaling modulates immunoglobulin-associated genes and tumor-specific Ab production. We furthermore demonstrated c-Maf-positive B cell subsets and an increase of IL-10-producing B cells after incubation with IL-4 and CD40L in the peripheral blood of patients with melanoma. Conclusion: Our study highlights that B cell c-Maf signaling drives tumor progression through the modulation of Breg, inflammatory responses, and tumor-specific Ab responses.

Myocardial infarction (MI) triggers acute inflammation, marked by neutrophil infiltration. Although neutrophils are central to this response, the exact role of various neutrophil‐derived factors is not fully understood. Clinical studies have linked one such enigmatic factor, chitinase‐3 like‐1, to MI outcomes. Hence, we investigated its role in post‐MI remodeling. We found that chitinase‐3 like‐1 (CHI3L1) is upregulated after MI and secreted by activated neutrophils but does not directly affect neutrophil activity. To assess whether increased CHI3L1 influences ventricular remodeling, we subjected mice to non‐reperfused MI and administered recombinant CHI3L1. Increased CHI3L1 levels worsened ventricular remodeling. In contrast, CHI3L1‐deficient mice showed reduced ventricular remodeling after MI. To explore the underlying mechanisms, we assessed interactions with other cells known to be important in ventricular remodeling. Immunoprofiling of infarcted CHI3L1‐deficient mouse hearts revealed a faster decline in neutrophil and monocyte numbers, indicating quicker resolution of inflammation. These findings provide direct evidence that CHI3L1 exacerbates ventricular inflammation and remodeling following MI through gain‐ and loss‐of‐function approaches.

Background/Objectives: Tumor-draining lymph nodes (TDLNs) play a critical role in shaping a pre-metastatic and immunosuppressive niche that facilitates tumor dissemination. However, a robust in vivo model that recapitulates regional lymph node and distant metastasis remains elusive. We sought to establish and characterize an animal model that reliably mimics spontaneous human melanoma progression from primary tumor to regional lymph node and distant organ metastasis. Methods: B16F10-Luc2 melanoma cells were subcutaneously implanted from the hock area into the lower medial thigh of C57BL/6J mice to establish a metastatic melanoma mouse model with reliable regional lymph node metastasis and distant metastasis. Tumor growth was monitored over time. ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) and bioluminescence imaging (BLI) were used to track lymph node and lung metastases in vivo. Immunocytochemistry (IHC) was performed to confirm the metastatic melanoma cells in tissues. The immune landscape of metastatic lymph nodes was characterized by Cytometry by Time-Of-Flight (CyTOF). Results: This implantation strategy resulted in consistent primary tumor growth accompanied by reproducible metastasis to ipsilateral inguinal lymph nodes (IILN) and subsequent lung metastasis. Multi-modal imaging (PET/CT and BLI) enabled non-invasive monitoring of metastatic progression in vivo. Histological analyses confirmed melanoma cell infiltration in lymph nodes and lung tissues. Notably, CyTOF profiling revealed a distinct immunological remodeling within the TDLN, characterized by immunosuppressive phenotypes in the tumor-draining ipsilateral inguinal lymph node (IILN) compared with naïve nodes, indicative of a potential immunotolerant environment in tumor-bearing mice associated with metastatic progression. Conclusions: We present a reproducible and clinically relevant syngeneic melanoma mouse model that recapitulates lymphatic dissemination to regional lymph nodes and distant lung metastasis, and mimics the immunosuppressive phenotypes in the tumor-draining lymph node microenvironment seen in human melanoma patients. This model provides a valuable platform for investigating the mechanisms of lymphatic metastasis and the immunological dynamics of TDLNs, with potential applications in evaluating therapeutic strategies targeting metastatic progression.

Background/Objectives: Ulcerative colitis (UC) is a chronic, relapsing inflammatory bowel disease (IBD) lacking therapies that directly promote mucosal healing, an important clinical endpoint and therapeutic goal for achieving remission and improved long-term outcomes. Epithelial restitution is a key component of effective mucosal healing. EPICERTIN, a novel biotherapeutic candidate, has previously demonstrated epithelial repair activity in dextran sulfate sodium (DSS)-induced colitis models and enhanced epithelial cell viability in human IBD colon explants. To further substantiate its therapeutic efficacy in a UC-relevant context, we evaluated EPICERTIN in acute oxazolone (OXA)-induced colitis in BALB/c mice, a model reflecting the adaptive immune-driven inflammation and histopathologic characteristics of human UC. Methods: Orally administered EPICERTIN, at escalating doses (0.3 µg, 3 µg, and 30 µg), was assessed for therapeutic efficacy in male and female mice through body weight, Disease Activity Index (DAI) scores, and histopathology. Wound healing and immune impacts were examined using qRT-PCR, Imaging Mass Cytometry (IMC), and Cytometry by Time of Flight (CyTOF) in male mice. Results: EPICERTIN effectively mitigated acute OXA-induced colitis. The 3 µg dose provided the greatest benefit, improving body weight recovery and reducing DAI and histopathological damage scores. Treatment reduced Il1b while increasing Cdh1 expression, accompanied by higher levels of epithelial markers (pan-cytokeratin (PanCK), E-cadherin, epithelial cell adhesion marker (EpCAM)) and decreased fibrotic markers (collagen type I, alpha-smooth muscle actin (α-SMA), fibronectin). Moreover, EPICERTIN reduced inflammatory lymphoid and myeloid cells while increasing γδ T cells in the colon lamina propria. Conclusions: Collectively, these results demonstrate that EPICERTIN promotes epithelial restitution, suppresses inflammation, and supports mucosal healing, substantiating its therapeutic potential for UC.