Crystal structure of the secretory chorismate mutase protein of Mycobacterium tuberculosis (MtbCM) reveals presence of a proline rich region on its surface that serve as a recognition site for protein-protein interaction. This study shows that MtbCM upregulates IL-10 which favors M. tuberculosis by affecting PKCε-MKP-1-p38 MAPK signaling. MtbCM translocates to the Golgi-network where it interacts with AKAP9 via its SH3-binding domain to inhibit AKAP9-PKCε interaction and reducing PKCε phosphorylation. In the absence of phosphorylated PKCε, IRAK3 fails to stabilize MKP-1 resulting in higher p38 MAPK activation and IL-10 production. M. smegmatis expressing MtbCM survived better in infected mice. Mutation in SH3-binding domain ablated MtbCM-AKAP9 interaction resulting in IL-10 production and decreased bacterial survival. This study highlights the importance of SH3-binding domain in host-pathogen interaction and a role of MtbCM in modulation of cytokine response and mycobacterial virulence in addition to its role in shikimate pathway.
© 2024 The Author(s).

Osteosarcoma is a highly common malignant bone tumor. Its highly metastatic properties are the leading cause of mortality for cancer. Niclosamide, a salicylanilide derivative, is an oral antihelminthic drug of known anticancer potential. However, the effect of niclosamide on osteosarcoma cell migration, invasion and the mechanisms underlying have not been fully clarified. Therefore, this study investigated niclosamide's underlying pathways and antimetastatic effects on osteosarcoma. In this study, U2OS and HOS osteosarcoma cell lines were treated with niclosamide and then subjected to assays for determining cell migration ability. The results indicated that niclosamide, at concentrations of up to 200 nM, inhibited the migration and invasion of human osteosarcoma U2OS and HOS cells and repressed the transforming growth factor beta-induced protein (TGFBI) expression of U2OS cells, without cytotoxicity. After TGFBI knockdown occurred, cellular migration and invasion behaviors of U2OS cells were significantly reduced. Moreover, niclosamide significantly decreased the phosphorylation of ERK1/2 in U2OS cells and the combination treatment of the MEK inhibitor (U0126) and niclosamide resulted in the intensive inhibition of the TGFBI expression and the migratory ability in U2OS cells. Therefore, TGFBI derived from osteosarcoma cells via the ERK pathway contributed to cellular migration and invasion and niclosamide inhibited these processes. These findings indicate that niclosamide may be a powerful preventive agent against the development and metastasis of osteosarcoma.

h4>S ummary /h4> Cancer cells disseminate during very early and sometimes asymptomatic stages of tumor progression. Granted that biological barriers to tumorigenesis exist, there must also be limiting steps to early dissemination, all of which remain largely unknown. We report that the orphan nuclear receptor NR2F1/COUP-TF1 serves as a barrier to early dissemination. High-resolution intravital imaging revealed that loss of function of NR2F1 in HER2+ early cancer cells increased in vivo dissemination without accelerating mammary tumor formation. NR2F1 expression was positively regulated by the tumor suppressive MMK3/6-p38-MAPK pathway and downregulated by HER2 and Wnt4 oncogenic signaling. NR2F1 downregulation by HER2 in early cancer cells led to decreased E-cadherin expression and β-catenin membrane localization, disorganized laminin 5 deposition, and increased expression of CK14, TWIST1, ZEB1 and PRRX1. Our findings reveal the existence of an inhibitory mechanism of dissemination regulated by NR2F1 downstream of HER2 signaling.

In order to investigate the molecular mechanisms by which the oncogenic mutant KIT/D816V causes transformation of cells, we investigated proteins that selectively bind KIT/D816V, but not wild-type KIT, as potential mediators of transformation. By mass spectrometry several proteins were identified, among them a previously uncharacterized protein denoted XKR5 (XK-related protein 5), which is related to the X Kell blood group proteins. We could demonstrate that interaction between XKR5 and KIT/D816V leads to phosphorylation of XKR5 at Tyr 369, Tyr487, and Tyr 543. Tyrosine phosphorylated XKR5 acts as a negative regulator of KIT signaling, which leads to downregulation of phosphorylation of ERK, AKT, and p38. This led to reduced proliferation and colony forming capacity in semi-solid medium. Taken together, our data demonstrate that XKR5 is a novel type of negative regulator of KIT-mediated transformation.

Activating signaling mutations are common in acute leukemia with KMT2A (previously MLL) rearrangements (KMT2A-R). These mutations are often subclonal and their biological impact remains unclear. Using a retroviral acute myeloid mouse leukemia model, we demonstrate that FLT3 ITD , FLT3 N676K , and NRAS G12D accelerate KMT2A-MLLT3 leukemia onset. Further, also subclonal FLT3 N676K mutations accelerate disease, possibly by providing stimulatory factors. Herein, we show that one such factor, MIF, promotes survival of mouse KMT2A-MLLT3 leukemia initiating cells. We identify acquired de novo mutations in Braf, Cbl, Kras, and Ptpn11 in KMT2A-MLLT3 leukemia cells that favored clonal expansion. During clonal evolution, we observe serial genetic changes at the Kras G12D locus, consistent with a strong selective advantage of additional Kras G12D . KMT2A-MLLT3 leukemias with signaling mutations enforce Myc and Myb transcriptional modules. Our results provide new insight into the biology of KMT2A-R leukemia with subclonal signaling mutations and highlight the importance of activated signaling as a contributing driver.