The resistance of cancer cells to therapy is responsible for the death of most patients with cancer1. Epithelial-to-mesenchymal transition (EMT) has been associated with resistance to therapy in different cancer cells2,3. However, the mechanisms by which EMT mediates resistance to therapy remain poorly understood. Here, using a mouse model of skin squamous cell carcinoma undergoing spontaneous EMT during tumorigenesis, we found that EMT tumour cells are highly resistant to a wide range of anti-cancer therapies both in vivo and in vitro. Using gain and loss of function studies in vitro and in vivo, we found that RHOJ-a small GTPase that is preferentially expressed in EMT cancer cells-controls resistance to therapy. Using genome-wide transcriptomic and proteomic profiling, we found that RHOJ regulates EMT-associated resistance to chemotherapy by enhancing the response to replicative stress and activating the DNA-damage response, enabling tumour cells to rapidly repair DNA lesions induced by chemotherapy. RHOJ interacts with proteins that regulate nuclear actin, and inhibition of actin polymerization sensitizes EMT tumour cells to chemotherapy-induced cell death in a RHOJ-dependent manner. Together, our study uncovers the role and the mechanisms through which RHOJ acts as a key regulator of EMT-associated resistance to chemotherapy.
© 2023. The Author(s).

Atypical teratoid rhabdoid tumor (ATRT) is a highly aggressive pediatric brain tumor. Despite radiation, aggressive chemotherapy and autologous stem cell rescue, children usually have a poor survival time. In the present study, the role of TP53/MDM2 interaction in ATRT was investigated. A functional genomic screen identified the TP53/MDM2 axis as a therapeutic target in the central nervous system (CNS) ATRT. Gene expression analysis revealed that all ATRT sub‑groups expressed high levels of MDM2, which is a negative regulator of TP53. Using cell viability, colony formation and methylcellulose assays it was found that genetic MDM2 inhibition with short hairpin RNA or chemical MDM2 inhibition with small molecule inhibitors, Nutlin3 and idasanutlin (RG7388) decreased the growth of ATRT cell lines. Furthermore, idasanutlin significantly decreased the growth of intracranial orthotopic ATRT brain tumors, as evaluated using T2 MRI, and prolonged survival time relative to control animals. MRI of intracranial tumors showed that diffusion coefficient, an effective marker for successful treatment, significantly increased with idasanutlin treatment showing tumor necrosis/apoptosis. Immunohistochemistry revealed an increased number of caspase‑3‑positive cells in the idasanutlin treatment group, confirming the induction of apoptosis in vivo. Using flow cytometry and western blot analysis we show that inhibition of MDM2 enhanced radiation sensitivity in vitro by potentiating DNA damage via the induction of the TP53/Bax/Puma proapoptotic axis. Furthermore, DNA damage was associated with increased mitochondrial reactive oxygen species accumulation. The present study demonstrated that MDM2 expression level was increased in ATRT patient samples and MDM2 inhibition suppressed ATRT cell growth in vitro, and leads to apoptosis in vivo. MDM2 inhibition potentiates DNA damage and sensitizes ATRT cells to radiation. These findings highlight the TP53/MDM2 axis as a rational therapeutic target in CNS ATRT.

Potassium 5-cyano-4-methyl-6-oxo-1,6-dihydropyridine-2-olate (CPBMF65) is a potent inhibitor of the uridine phosphorylase 1 (UPP1) enzyme. Its non-ionized analog has already demonstrated biological properties by reducing adverse effects caused by the chemotherapeutic 5-fluorouracil (5-FU). In addition, it has been demonstrated that uridine inhibits inflammation and fibrosis in bleomycin lung injury, decreasing collagen production. The purpose of this study was to investigate the in vitro and in vivo effects of CPBMF65 on activated hepatic stellate cells (HSC) and on carbon tetrachloride-induced liver fibrosis in mice. After incubation with CPBMF65, decreased cell proliferation and phenotype reversion were observed in vitro. In addition, CPBMF65 promoted a protective effect on tetrachloride-induced liver fibrosis in mice, demonstrated by its antifibrotic and anti-inflammatory actions. The results of the present study indicate that the UPP1 inhibitor (CPBMF65) may have potential as a novel therapeutic agent for the treatment of liver fibrosis.
Copyright © 2020 Elsevier B.V. All rights reserved.

Hematopoietic stem and progenitor cells (HSPCs) depend on regulatory cytokines from the marrow microenvironment. From an unbiased cytokine screen of murine marrow supernatants, we identified C-C motif chemokine ligand 5 (CCL5) as an endothelial cell-secreted hematopoietic growth factor. Following treatment with CCL5, hematopoietic regeneration is accelerated and survival is prolonged after radiation. In mice with deletion of Ccr5, hematopoietic regeneration is delayed compared to control mice. Deletion of Ccr5 specifically in hematopoietic cells was sufficient to delay regeneration, while the deletion of Ccr5 in stromal/endothelial cells was not. Mechanistically, CCL5 promotes hematopoietic cell cycling and cell survival. Like murine hematopoietic cells, human hematopoietic cells (cord blood, healthy marrow, and peripheral blood) increase CCR5 expression after radiation exposure to promote cell survival. These data establish that CCL5 and CCR5 signaling play critical roles in hematopoietic regeneration and could serve as therapeutic targets to shorten the duration of myelosuppression.
Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.