Tuning MPL signaling to influence hematopoietic stem cell differentiation and inhibit essential thrombocythemia progenitors

Thrombopoietin (TPO) and the TPO-receptor (TPO-R, or c-MPL) are essential for hematopoietic stem cell (HSC) maintenance and megakaryocyte differentiation. Agents that can modulate TPO-R signaling are highly desirable for both basic research and clinical utility. We developed a series of surrogate protein ligands for TPO-R, in the form of diabodies (DBs), that homodimerize TPO-R on the cell surface in geometries that are dictated by the DB receptor binding epitope, in effect "tuning" downstream signaling responses. These surrogate ligands exhibit diverse pharmacological properties, inducing graded signaling outputs, from full to partial TPO agonism, thus decoupling the dual functions of TPO/TPO-R. Using single-cell RNA sequencing and HSC self-renewal assays we find that partial agonistic diabodies preserved the stem-like properties of cultured HSCs, but also blocked oncogenic colony formation in essential thrombocythemia (ET) through inverse agonism. Our data suggest that dampening downstream TPO signaling is a powerful approach not only for HSC preservation in culture, but also for inhibiting oncogenic signaling through the TPO-R

CD47 prevents the elimination of diseased fibroblasts in scleroderma

Scleroderma is a devastating fibrotic autoimmune disease. Current treatments are partly effective in preventing disease progression but do not remove fibrotic tissue. Here, we evaluated whether scleroderma fibroblasts take advantage of the “don’t-eat-me-signal” CD47 and whether blocking CD47 enables the body’s immune system to get rid of diseased fibroblasts. To test this approach, we used a Jun-inducible scleroderma model. We first demonstrated in patient samples that scleroderma upregulated transcription factor JUN and increased promoter accessibilities of both JUN and CD47. Next, we established our scleroderma model, demonstrating that Jun mediated skin fibrosis through the hedgehog-dependent expansion of CD26+Sca1– fibroblasts in mice. In a niche-independent adaptive transfer model, JUN steered graft survival and conferred increased self-renewal to fibroblasts. In vivo, JUN enhanced the expression of CD47, and inhibiting CD47 eliminated an ectopic fibroblast graft and increased in vitro phagocytosis. In the syngeneic mouse, depleting macrophages ameliorated skin fibrosis. Therapeutically, combined CD47 and IL-6 blockade reversed skin fibrosis in mice and led to the rapid elimination of ectopically transplanted scleroderma cells. Altogether, our study demonstrates the efficiency of combining different immunotherapies in treating scleroderma and provides a rationale for combining CD47 and IL-6 inhibition in clinical trials

Inhibition of Six1 affects tumour invasion and the expression of cancer stem cell markers in pancreatic cancer

Abstract Background Epithelial-to-mesenchymal transition (EMT) and cancer stem cells (CSC) contribute to tumour progression and metastasis. Assessment of transcription factors involved in these two mechanisms can help to identify new targets for an oncological therapy. In this study, we focused on the evaluation of the transcription factor Six1 (Sine oculis 1). This protein is involved in embryologic development and its contribution to carcinogenesis has been described in several studies. Methods Immunohistochemistry against Six1 was performed on a tissue microarray containing specimens of primary pancreatic ductal adenocarcinomas (PDAC) of 139 patients. Nuclear and cytoplasmic expression was evaluated and correlated to histopathological parameters. Expression of Six1 was inhibited transiently by siRNA in Panc1 and BxPc3 cells and stably by shRNA in Panc1 cells. Expression analysis of CDH1 and Vimentin mRNA was performed and cell motility was tested in a migration assay. Panc1 cells transfected with Six1 shRNA or scrambled shRNA were injected subcutaneously into nude mice. Tumour growth was observed for four weeks. Afterwards, tumours were stained against Six1, CD24 and CD44. Results Six1 was overexpressed in the cytoplasm and cellular nuclei in malignant tissues (p < 0.0001). No correlation to histopathological parameters could be detected. Six1 down-regulation decreased pancreatic cancer cell motility in vitro. CDH1 and vimentin expression was decreased after inhibition of the expression of Six1. Pancreatic tumours with impaired expression of Six1 showed significantly delayed growth and displayed loss of the CD24+/CD44+ phenotype. Conclusion We show that Six1 is overexpressed in human PDAC and that its inhibition results in a decreased tumour progression in vitro and in vivo. Therefore, targeting Six1 might be a novel therapeutic approach in patients with pancreatic cancer

Additional file 2: Fig. S1. of Inhibition of Six1 affects tumour invasion and the expression of cancer stem cell markers in pancreatic cancer

Sequence of siRNA against Six1R1. (PPTX 3958 kb

Elucidating the fundamental fibrotic processes driving abdominal adhesion formation

Abdominal adhesions are a common cause of bowel obstruction, but knowledge regarding adhesion biology and anti-adhesion therapies remains limited. Here the authors report a systematic analysis of mouse and human adhesion tissues demonstrating that visceral fibroblast JUN and associated PDGFRA expression promote adhesions, and JUN suppression can prevent adhesion formation