Immune cells in tumor microenvironment play a prominent role in tumor progression and metastasis. represents an important player in innate and adaptive immunity by regulating differentiation, maturation and activation of macrophages, dendritic cells, B cells and T cells. However, the role of miR-155 expression in immune cells in solid tumor development is less elucidated. Our current study showed that both B16-F10 melanoma and Lewis lung carcinoma tumors grew much faster in bic/miR-155 knockout (miR-155 2/2 ) mice along with an increase of myeloid-derived suppressor cells (MDSCs) accumulation in tumors, compared to that in wild-type mice. Bone marrow transplantation study showed that bone marrow miR-155 deficiency could replicate the above tumor-promoting phenotype. In vitro study demonstrated that tumor-infiltrating miR-155 2/2 MDSCs showed greater migration ability and expressed higher level of multiple chemokines. Furthermore, we found that the level of HIF1a, a direct target of miR-155, was increased in miR-155 deficient MDSCs, and that the increased HIF-1a upregulated CXCL1, CXCL3 and CXCL8 expression in MDSCs, contributing to the enhanced recruitment of miR-155 2/2 MDSCs to the tumors. Moreover, miR-155 2/2 MDSCs showed enhanced immunosuppressive and pro-angiogenic capacities. Taken together, our study, for the first time, demonstrated that miR-155 deficiency promoted solid tumor growth through increasing the recruitment of MDSCs to tumor microenvironment and enhancing the tumor-promoting functions of the recruited MDSCs. Thus, upregulating miR-155 expression in MDSCs may be developed as a therapeutic approach to halt tumor development.Tumor progression is supported by chronic inflammatory microenvironment which is characterized by continuous secretion of inflammatory factors and infiltration of a variety of leukocytes. 1-4 Among them, myeloid-derived suppressor cells (MDSCs), defined as Gr-1 1 CD11b 1 cells in mice, represent one of the most important players. 5 MDSCs have been demonstrated to promote tumor progression by disturbing host immune responses, promoting tumor cell proliferation, migration and invasion, and enhancing angiogenesis. [6][7][8][9][10] In addition, infiltration of MDSCs in primary tumor sites and metastatic organs is a major obstacle to effective antitumor therapies. 11,12 For example, recruitment of MDSCs in certain tumors is responsible for the refractoriness to anti-VEGF treatment. 11 Thus, better understanding the molecular mechanisms underlying MDSC expansion, recruitment and activation is critical for developing more effective cancer therapeutic strategies.It has been show that microRNA-155 (miR-155) is upregulated in several solid tumors and B-cell lymphomas, and overexpression of miR-155 in tumor cells correlates with tumor aggressiveness in animal models. [13][14][15] Clinical studies have also suggested that high expression level of miR-155 in Tumor Immunology

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Facial mimicry has been suggested to be a behavioral index for emotional empathy. The present study is the first to investigate the link between facial muscle activity and empathy for pain by facial electromyographic (EMG) recording while observers watched videos depicting real-life painful events. Three types of visual stimulus were used: an intact painful scene and arm-only (needle injection) and face only (painful expression) scenes. Enhanced EMG activity of the corrugator supercilii (CS) and zygomaticus major (ZM) muscles was found when observers viewed others in pain, supporting a unique pain expression that is distinct from the expression of basic emotions. In the intact video stimulus condition, CS activity was correlated positively with the empathic concern score and ZM activity, suggesting facial mimicry mediated empathy for pain. Cluster analysis of facial EMG responses revealed markedly different patterns among stimulus types, including response category, ratio, and temporal dynamics, indicating greater ecological validity of the intact scene in eliciting pain empathy as compared with partial scenes. This study is the first to quantitatively describe pain empathy in terms of facial EMG data. It may provide important evidence for facial mimicry as a behavioral indicator of pain empathy.

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