published the paper. Data availability All relevant data are available from the corresponding author upon affordable request. Here, we show that DLBCL initiates dissemination through activating STAT3-mediated amoeboid migration. Mechanistically, STAT3 activates transcription, which competes with the RhoGDP dissociation inhibitor RhoGDI 1A-116 to activate RhoA. In addition, activated STAT3 regulates microtubule dynamics and releases ARHGEF2 to activate RhoA. Both the JAK inhibitor ruxolitinib and the microtubule stabilizer Taxol suppress DLBCL cell dissemination in vivo. A clinical DLBCL sample analysis shows that STAT3-driven amoeboid movement is particularly important for the transition from stage I to stage II. This study elucidates the mechanism Rabbit Polyclonal to NCOA7 of DLBCL dissemination and progression and highlights the potential of combating advanced DLBCL with a JAK/STAT inhibitor or microtubule stabilizer to reduce DLBCL motility; these findings may have a great impact on the development of patient-tailored treatments for DLBCL. Introduction Diffuse large B-cell lymphoma (DLBCL), an aggressive lymphoid malignancy that arises primarily from mature B lymphocytes in the germinal center of the lymph node, is the most prevalent type of lymphoma and accounts for 30% of all non-Hodgkins lymphomas in adults1. The clinical presentation of DLBCL is usually a single, rapidly enlarged mass (localized disease) or multiple lymphadenopathies (disseminated disease)1. During dissemination, DLBCL cells lack focal contacts and have a high level of plasticity2. DLBCL treatment yields an excellent response to the localized disease. Nevertheless, the response is usually reduced significantly in the disseminated disease3, indicating the necessity of targeting disseminated lymphoma cells in advanced-stage cases. However, most current therapies overlook the impact of DLBCL cell dissemination and focus mainly on inhibiting proliferation and inducing apoptosis in lymphoma cells. The deregulation of normal B?cell signals that sustain growth and survival is commonly noted in DLBCL. Myc, B-cell lymphoma 6 (BCL6), and B-cell lymphoma 2 (BCL-2) are commonly overexpressed following chromosomal translocation, resulting in the abnormal proliferation of lymphoma cells4C6. Constitutive activation of 1A-116 the NF-B pathway is usually observed predominantly in activated B-cell (ABC)-type DLBCL7. Recent studies have highlighted the importance of deregulated cytokine-mediated signaling pathways in DLBCL progression. Activation of the transcription factor signal transducer and activator of transcription 3 (STAT3) correlates with a worse DLBCL prognosis8. Increased levels of interleukin 6 (IL-6) and interleukin 10 (IL-10), the major upstream cytokines of STAT39, are associated with a poor 1A-116 DLBCL prognosis10. Although the oncogenic signals that sustain DLBCL cell proliferation and survival have been studied extensively, the link between the proliferation/survival signals and mechanisms of DLBCL cell dissemination remains elusive. Amoeboid movement, which refers to the movement of the amoeba, is usually a type of protease-independent movement that is characterized by low adhesion pressure and high actomyosin contractility11. Compared to cells with mesenchymal movement, another type of single cell movement, amoeboid-type cells move faster in 1A-116 three-dimensional (3D) culture systems12. The RhoA-Rho-associated protein kinase (ROCK)-myosin axis is the most well-known mechanism of cell contractility and is the major signaling pathway that induces amoeboid movement13,14. Amoeboid movement has been described as the major movement method for T-lymphocytes and normal hematopoietic cells15. In addition, amoeboid movement has been observed in different types of cancer cells16. However, the clinical impact and driving mechanism of amoeboid movement in DLBCL are unclear. In this study, we describe the impact of amoeboid movement on DLBCL dissemination and the underlying mechanism. We show that STAT3 coordinates DLBCL movement through activating STAT3, which in turn activates or regulates microtubule dynamics to activate RhoA. Inhibiting JAK/STAT3 activity or intercepting microtubule assembly suppresses DLBCL migration. These findings provide valuable information regarding the development of advanced-stage DLBCL. Results Amoeboid movement is critical for DLBCL early dissemination In this study, we investigated the mechanism of DLBCL cell dissemination. We first confirmed the involvement of amoeboid movement in the dissemination of DLBCL. Gene set enrichment analysis (GSEA) showed that this gene expression signature of amoeboid movement, but not mesenchymal movement, was associated with DLBCL Ann Arbor stage IICIV, but not stage I (Fig.?1a and Supplementary Fig.?1a). A significant increase in the phosphorylated myosin light chain (MLC) levels, which indicates the activation of Rho-ROCK signaling and is a marker for amoeboid movement17, was observed in stage IICIV DLBCL patient samples (Fig.?1b, c, Supplementary Fig.?1b and Supplementary Table?1, 2), which supports the involvement of amoeboid movement in the early dissemination of DLBCL. Next, we investigated amoeboid movement in DLBCL using trajectory tracking and in vivo monitoring. Compared to the squamous cell carcinoma (SCC) cell line OEC-M1, which moves using the mesenchymal mechanism18, the DLBCL cell lines SUDHL-5, OCI-Ly3, HT, U2932, and DB displayed an amoeboid morphology in 3D collagen gels.