Co-evolution of tumor cells and hepatocytes fostered by SLIT2-ROBO1 axis facilitates liver metastasis of pancreatic ductal adenocarcinoma

To explore the mechanism of co-evolution and potential driver of which in pancreatic ductal adenocarcinoma (PDAC) metastasis to liver, we studied key molecules involved in this progress and their translational values. Pre-metastatic niche (PMN) and macro metastatic niche (MMN) formation in mouse model were recognized via CT combined 3D organ reconstruction bioluminescence imaging. We next confirmed the expressions and distributions of SLIT2 and ROBO1 in 35 cases of human matched liver metastasis and primary PDAC samples, 14 case human PDAC liver metastasis transcriptional analysis, intrasplenic mouse models and KrasG12D/Trp53R172H/Pdx1-Cre (KPC) mouse models. Translational value was assessed on Slit2fl/fl/Alb1-Cre (Slit2 CKO) mice, KPC mouse model and Ex vivo tests via administration of neutralizing antibody targeting ROBO1. We also analyzed prognosis of 266 cases human PDAC tissue with or without SLIT2-ROBO1 fostered co-evolution and demonstrated the dependence receptor (DR) characteristics of ROBO1 in the following-up mechanism study. Experiments on Slit2 CKO, Slit2 CKO-RE and KPC mouse models demonstrated that disturbing SLIT2-ROBO1 mediated co-evolution in liver microenvironment via preventing their interaction could significantly attenuate liver metastasis of PDAC. We have demonstrated that co-evolution took advantage of DR characteristics in PMN and MMN. Targeting SLIT2-ROBO1 axis could be a therapeutic strategy towards metastatic PDAC.

Suppressing MDSC Recruitment to the Tumor Microenvironment by Antagonizing CXCR2 to Enhance the Efficacy of Immunotherapy

Myeloid-derived suppressor cells (MDSCs) are a heterogenous population of cells derived from immature myeloid cells. These cells are often associated with poor responses to cancer therapy, including immunotherapy, in a variety of tumor types. The C-X-C chemokine receptor 2 (CXCR2) signaling axis plays a key role in the migration of immunosuppressive MDSCs into the tumor microenvironment (TME) and the pre-metastatic niche. MDSCs impede the efficacy of immunotherapy through a variety of mechanisms. Efforts to target MDSCs by blocking CXCR2 is an active area of research as a method for improving existing and novel immunotherapy strategies. As immunotherapies gain approval for a wider array of clinical indications, it will become even more important to understand the efficacy of CXCR2 inhibition in combating immunotherapy resistance at different stages of tumor progression.

Role of pre-metastatic niche in organ specificity of breast cancer metastasis. Influence on metastatic potential as a basis for CDK4/6-inhibition efficacy in early therapy of disseminated hormone-receptor-positive disease

Influencing the pre-metastatic niche is a very perspective cancer treatment strategy in order of preventing metastases formation. It was found that bone marrow progenitor cells and tumor cells secreting biological compounds are key components in the formation of the pre-metastatic niche. Myeloid suppressor cells (MSCs) are the main type of bone marrow cells in pre-metastatic niches. At the same time, tumor-associated chronic inflammation induces the expression of proinflammatory cytokines triggering myeloid cells differentiation into myeloid suppressor cells. When circulating tumor cells enter the circulatory channel, their interaction with immune cells is observed, which additionally influences the pre-metastatic site preparation. Studies have shown that the entire spectrum of immune cells is capable of influencing the metastasis formation by circulating tumor cells. The epithelialmesenchymal transition with the tumor cell transporting form appearence was found to be related to the function of the ZEB1 protein. Its activity is regulated by numerous signaling mechanisms at the transcriptional level, including TGFβ, Wnt and Notch. This initiates epithelial-mesenchymal transition of breast cancer cells. Zhang Z.et al. proved that CDK4/6 blocking leads ZEB1 protein stability decreasing, preventing metastasis in breast cancer in vitro and in vivo. Moreover, USP51 deubiquitinase has been identified as a target of cyclin-dependent 4/6 kinases. At the molecular level, CDK4/6 phosphorylate and activates USP51, which then influences ZEB1 deubiquitination and stabilization. A positive correlation was demonstrated between the expression of p-RB (an indicator of CDK4/6 activity), p-USP51 and ZEB1 in breast cancer samples. Thus, the CDK4/6-USP51-ZEB1 axis may play a key role in the metastasis of breast cancer. In breast cancer cells, inhibition of CDK4/6 was shown to increase the expression of E-cadherin but decrease the expression of mesenchymal markers, reducing the migratory ability and invasiveness of breast cancer cell lines. This biological effect may also explain the clinical efficacy of the CDK4/6 inhibitor Abemaciclib in early-line therapy of metastatic breast cancer as well as in adjuvant combination hormone therapy for the prevention of metastatic lesions in patients at high risk of recurrence and progression in the MONARCH E study. Besides, there were no response predictors evaluated in trials investigating CDK4/6 in breast cancer treatment and it is unknown if there any differences in treatment response according to the metastatic site. The clinical cases demonstrate abemaciclib clinical efficacy in metastatic breast cancer treatment regardless of metastatic site.

Emerging Role of Extracellular Vesicles and Cellular Communication in Metastasis

Communication between cancer cells and the surrounding stromal cells of the tumor microenvironment (TME) plays a key role in promoting metastasis, which is the major cause of cancer death. Small membrane-bound particles called extracellular vesicles (EVs) are released from both cancer and stromal cells and have a key role in mediating this communication through transport of cargo such as various RNA species (mRNA, miRNA, lncRNA), proteins, and lipids. Tumor-secreted EVs have been observed to induce a pro-tumorigenic phenotype in non-malignant cells of the stroma, including fibroblasts, endothelial cells, and local immune cells. These cancer-associated cells then drive metastasis by mechanisms such as increasing the invasiveness of cancer cells, facilitating angiogenesis, and promoting the formation of the pre-metastatic niche. This review will cover the role of EV-mediated signaling in the TME during metastasis and highlight the therapeutic potential of targeting these pathways to develop biomarkers and novel treatment strategies.

The regulatory effect of hyaluronan on human mesenchymal stem cells’ fate modulates their interaction with cancer cells in vitro

Metastatic spread of cancer cells into a pre-metastatic niche is highly dependent on a supporting microenvironment. Human bone marrow-derived mesenchymal stem cells (bmMSCs) contribute to the tumor microenvironment and promote cancer metastasis by inducing epithelial-to-mesenchymal transition and immune evasion. The underlying mechanisms, however, are incompletely understood. The glycosaminoglycan hyaluronan (HA) is a central component of the extracellular matrix and has been shown to harbor pro-metastatic properties. In this study we investigated the highly disseminating breast cancer and glioblastoma multiforme cell lines MDA-MB-321 and U87-MG which strongly differ in their metastatic potential to evaluate the impact of HA on tumor promoting features of bmMSC and their interaction with tumor cells. We show that adipogenic differentiation of bmMSC is regulated by the HA-matrix. This study reveals that MDA-MB-231 cells inhibit this process by the induction of HA-synthesis in bmMSCs and thus preserve the pro-tumorigenic properties of bmMSC. Furthermore, we show that adhesion of MDA-MB-231 cells to bmMSC is facilitated by the tumor cell-induced HA-rich matrix and is mediated by the HA-receptor LAYN. We postulate that invasive breast cancer cells modulate the HA-matrix of bmMSC to adapt the pre-metastatic niche. Thus, the HA-matrix provides a potential novel therapeutic target to prevent cancer metastasis.

Mesothelial-to-Mesenchymal Transition and Exosomes in Peritoneal Metastasis of Ovarian Cancer

Most patients with ovarian cancer (OvCA) present peritoneal disseminated disease at the time of diagnosis. During peritoneal metastasis, cancer cells detach from the primary tumor and disseminate through the intraperitoneal fluid. The peritoneal mesothelial cell (PMC) monolayer that lines the abdominal cavity is the first barrier encountered by OvCA cells. Subsequent progression of tumors through the peritoneum leads to the accumulation into the peritoneal stroma of a sizeable population of carcinoma-associated fibroblasts (CAFs), which is mainly originated from a mesothelial-to-mesenchymal transition (MMT) process. A common characteristic of OvCA patients is the intraperitoneal accumulation of ascitic fluid, which is composed of cytokines, chemokines, growth factors, miRNAs, and proteins contained in exosomes, as well as tumor and mesothelial suspended cells, among other components that vary in proportion between patients. Exosomes are small extracellular vesicles that have been shown to mediate peritoneal metastasis by educating a pre-metastatic niche, promoting the accumulation of CAFs via MMT, and inducing tumor growth and chemoresistance. This review summarizes and discusses the pivotal role of exosomes and MMT as mediators of OvCA peritoneal colonization and as emerging diagnostic and therapeutic targets.

Tenascin-C expression in the lymph node pre-metastatic niche in muscle-invasive bladder cancer

Background Markers of stromal activation at future metastatic sites may have prognostic value and may allow clinicians to identify and abolish the pre-metastatic niche to prevent metastasis. In this study, we evaluate tenascin-C as a marker of pre-metastatic niche formation in bladder cancer patient lymph nodes. Methods Tenascin-C expression in benign lymph nodes was compared between metastatic (n = 20) and non-metastatic (n = 27) patients with muscle-invasive bladder cancer. Urinary extracellular vesicle (EV) cytokine levels were measured with an antibody array to examine potential correlation with lymph node inflammation. The ability of bladder cancer EVs to activate primary bladder fibroblasts was assessed in vitro. Results Lymph node tenascin-C expression was elevated in metastatic patients vs. non-metastatic patients, and high expression was associated with worse survival. Urinary EVs contained four cytokines that were positively correlated with lymph node tenascin-C expression. Bladder cancer EVs induced tenascin-C expression in fibroblasts in an NF-κB-dependent manner. Conclusions Tenascin-C expression in regional lymph nodes may be a good predictor of bladder cancer metastasis and an appropriate imaging target. It may be possible to interrupt pre-metastatic niche formation by targeting EV-borne tumour cytokines or by targeting tenascin-C directly.

Exosome-Derived ADAM17 Promotes Liver Metastasis in Colorectal Cancer

Exosomes derived from cancer cells are deemed important drivers of pre-metastatic niche formation at distant organs, but the underlying mechanisms of their effects remain largely unknow. Although the role of ADAM17 in cancer cells has been well studied, the secreted ADAM17 effects transported via exosomes are less understood. Herein, we show that the level of exosome-derived ADAM17 is elevated in the serum of patients with metastatic colorectal cancer as well as in metastatic colorectal cancer cells. Furthermore, exosomal ADAM17 was shown to promote the migratory ability of colorectal cancer cells by cleaving the E-cadherin junction. Moreover, exosomal ADAM17 overexpression as well as RNA interference results highlighted its function as a tumor metastasis-promoting factor in colorectal cancer in vitro and in vivo. Taken together, our current work suggests that exosomal ADAM17 is involved in pre-metastatic niche formation and may be utilized as a blood-based biomarker of colorectal cancer metastasis.