Novel therapeutic strategies are urgently required for the clinical management of chemoresistant ovarian carcinoma, which is the most lethal of the gynecological malignancies. MicroRNAs (miRNAs) hold promise because they play a critical role in determining the cell phenotype by regulating several hundreds of targets, which could constitute vulnerabilities of cancer cells. A combination of gain of function miRNA screening and real-time continuous cell monitoring allows the identification of miRNAs with robust cytotoxic effects in chemoresistant ovarian cancer cells. Focusing on miR-3622b-5p, we show that it induces apoptosis in several ovarian cancer cell lines by both directly targeting Bcl-xL and EGFR mediating BIM upregulation. MiR-3622b-5p also sensitizes cells to cisplatin by inhibiting Bcl-xL in ovarian cancer cell lines escaping BIM induction. MiR-3622b-5p also exerts anti migratory capacities by targeting both LIMK1 and NOTCH1. These wide ranging antitumor properties of miR-3622b-5p in ovarian cancer cells are mimicked by the associations of pharmacological inhibitors targeting these proteins. The combination of an EGFR inhibitor together with a BH3-mimetic molecule induced a large decrease in cell viability in a panel of ovarian cancer cell lines and several ovarian patient derived tumor organoids, suggesting the value of pursuing such a combination therapy in ovarian carcinoma. Altogether, our work highlights the potential of phenotype based miRNA screening approaches to identify lethal interactions which might lead to new drug combinations and clinically applicable strategies. Copyright ©2020, American Association for Cancer Research.Tumor-associated M2-macrophages are one of the most abundant immunosuppressive cell types in the PDAC TME. However, the molecular mechanisms responsible for the generation of M2-macrophages are unclear. Here we demonstrated that overexpression of DCLK1-isoform2 in AsPC1 and MIA PaCa2 cells resulted in the polarization of M1-macrophages towards an M2-phenotype via secreted chemokines/cytokines. These M2-macrophages enhanced parental PDAC cell migration, invasion, and self-renewal and this was associated with increased expression of Snail and Slug. We observed distinct expression of Dclk-isoform2, marked infiltration of M2-macrophages and a marginal increase of CD8+ T-cells in 20-week-old KPCY mice pancreas compared to 5-week-old. Utilizing an autochthonous mouse model of pancreatic adenocarcinoma, we observed distinct immunoreactive Dclk1 and arginase1 in tissues where CD8+ T-cell infiltration was low and observed a paucity of DCLK1 and arginase1 staining where CD8+ T-cell infiltration was high. Finally, we found that DCLK1-isoform2 tumor educated M2-macrophages inhibits CD8+ T-cells proliferation and Granzyme-B activation. Inhibition of DCLK1 in an organoid co-culture system enhanced CD8+ T-cell activation and associated organoid death. We conclude that DCLK1-isoform2 is a novel initiator of alternate macrophage activation that contributes to the immunosuppression observed in the PDAC TME. These data suggest that tumor DCLK1-isoform2 may be an attractive target for PDAC therapy, either alone or in conjunction with immunotherapeutic strategies. Copyright ©2020, American Association for Cancer Research.Multiple myeloma (MM) is a plasma cell malignancy that grows in the bone marrow (BM). The major population of cells in the BM is represented by neutrophils and they can form neutrophil extracellular traps (NETs). Here, we investigated whether MM cells induce NET formation and whether targeting this process would delay MM progression. We demonstrated that murine and human MM cells stimulate citrullination of histone H3 and NET formation by neutrophils and that this process is abrogated by pharmacological targeting of peptidylarginine deiminase 4 (PAD4) with a novel specific small molecule inhibitor BMS-P5. Administration of BMS-P5 to MM-bearing mice delays appearance of symptoms and disease progression. Taken together, our data demonstrate that targeting PAD4 may be beneficial for treatment of MM.  https://www.selleckchem.com/products/blu-285.html  Copyright ©2020, American Association for Cancer Research.Clear cell renal cell carcinoma (ccRCC) remains a common cause of cancer mortality. Better understanding of ccRCC molecular drivers resulted in the development of anti-angiogenic therapies that block the blood vessels that supply tumors with nutrients for growth and metastasis. Unfortunately, most ccRCC patients eventually become resistant to initial treatments creating a need for alternative treatment options. We investigated the role of the small GTPase Rac1 in ccRCC. Analysis of ccRCC clinical samples indicates that Rac signaling drives disease progression and predicts patients with poorer outcomes. Investigation of Rac1 identifies multiple roles for Rac1 in the pathogenesis of ccRCC. Rac1 is overexpressed in renal cell carcinoma cell lines and drives proliferation and migratory/metastatic potential. Rac1 is also critical for endothelial cells to grow and form endothelial tubular networks potentiated by angiogenic factors. Importantly, Rac1 controls paracrine signaling of angiogenic factors including VEGF from renal carcinoma cells to surrounding blood vessels. A novel Rac1 inhibitor impaired the growth and migratory potential of both renal carcinoma cells and endothelial cells and reduced VEGF production by renal cell carcinoma cells thereby limiting paracrine signaling both in vitro and in vivo. Lastly, Rac1 was shown to be downstream of VEGF receptor (VEGFR) signaling and required for activation of MAPK signaling. In combination with VEGFR2 inhibitors, Rac inhibition provides enhanced suppression of angiogenesis. Therefore, targeting Rac in ccRCC has the potential to block the growth of tumor cells, endothelial cell recruitment, and paracrine signaling from tumor cells to other cells in the tumor microenvironment. Copyright ©2020, American Association for Cancer Research.Most osteosarcoma (OS) patients have subclinical pulmonary micrometastases at diagnosis. Mounting evidence suggests that macrophages facilitate metastasis. As the epidermal growth factor receptor (EGFR) has been implicated in carcinoma-macrophage crosstalk, in this study we asked whether gefitinib, an EGFR inhibitor, reduces OS invasion and metastatic outgrowth using the K7M2-Balb/c syngeneic murine model. Macrophages enhanced OS invasion in vitro, which was suppressed by gefitinib. Oral gefitinib inhibited tumor extravasation in the lung and reduced the size of metastatic foci, resulting in reduced metastatic burden. Gefitinib also altered pulmonary macrophage phenotype, increasing MHCII and decreasing CD206 expression compared to controls. Surprisingly, these effects are mediated through inhibition of macrophage receptor interacting protein kinase 2 (RIPK2), rather than EGFR. Supporting this, lapatinib, a highly specific EGFR inhibitor that does not inhibit RIPK2, had no effect on macrophage-promoted invasion, and RIPK2-/- macrophages failed to promote invasion.