The phenotypic transformation of well-differentiated epithelial carcinoma into a mesenchymal-like state provides cancer cells with the ability to disseminate locally and to metastasise. Different degrees of epithelial–mesenchymal transition (EMT) have been found to occur in carcinomas from breast, colon and ovarian carcinoma (OC), among others. Numerous studies have focused on bona fide epithelial and mesenchymal states but rarely on intermediate states. In this study, we describe a model system for appraising the spectrum of EMT using 43 well-characterised OC cell lines. Phenotypic EMT characterisation reveals four subgroups: Epithelial, Intermediate E, Intermediate M and Mesenchymal, which represent different epithelial–mesenchymal compositions along the EMT spectrum. In cell-based EMT-related functional studies, OC cells harbouring an Intermediate M phenotype are characterised by high N-cadherin and ZEB1 expression and low E-cadherin and ERBB3/HER3 expression and are more anoikis-resistant and spheroidogenic. A specific Src-kinase inhibitor, Saracatinib (AZD0530), restores E-cadherin expression in Intermediate M cells in in vitro and in vivo models and abrogates spheroidogenesis. We show how a 33-gene EMT Signature can sub-classify an OC cohort into four EMT States correlating with progression-free survival (PFS). We conclude that the characterisation of intermediate EMT states provides a new approach to better define EMT. The concept of the EMT Spectrum allows the utilisation of EMT genes as predictive markers and the design and application of therapeutic targets for reversing EMT in a selective subgroup of patients.

CXCR4 is a G-protein-coupled receptor that mediates recruitment of blood cells toward its ligand SDF-1. In cancer, high CXCR4 expression is frequently associated with tumor dissemination and poor prognosis. We evaluated the novel CXCR4 probe [68Ga]Pentixafor for in vivo mapping of CXCR4 expression density in mice xenografted with human CXCR4-positive MM cell lines and patients with advanced MM by means of positron emission tomography (PET). [68Ga]Pentixafor PET provided images with excellent specificity and contrast. In 10 of 14 patients with advanced MM [68Ga]Pentixafor PET/CT scans revealed MM manifestations, whereas only nine of 14 standard [18F]fluorodeoxyglucose PET/CT scans were rated visually positive. Assessment of blood counts and standard CD34+ flow cytometry did not reveal significant blood count changes associated with tracer application. Based on these highly encouraging data on clinical PET imaging of CXCR4 expression in a cohort of MM patients, we conclude that [68Ga]Pentixafor PET opens a broad field for clinical investigations on CXCR4 expression and for CXCR4-directed therapeutic approaches in MM and other diseases.

R e s e a R c h a R t i c l e5. Group 2 correlated with high STAT3 expression (i.e., STAT3 activation). (G) GSEA showed a significantly different distribution of the STAT3 activation-associated genes, with group 1 being negatively correlated (NES, -1.97; P < 0.001). Figure 1A; supplemental material available online with this article; doi:10.1172/JCI69094DS1). Gene set enrichment analysis (GSEA) showed a significantly different distribution of the STAT3 activation-associated genes among the hierarchical clustering-defined gene expression groups (normalized enrichment score [NES], -1.97; nominal P < 0.001; Figure 1G). In addition, mining the public repository Oncomine (www.oncomine. org) showed that STAT3 target genes were elevated in MM versus control tissue (Supplemental Figure 1B). Furthermore, we found the STAT3 signaling gene expression pattern to be associated with low bone disease, the MMSET groups, and the presence of a gain of the 1q21 locus, whereas we identified an inverse correlation with hyperdiploid disease (Supplemental Figure 1, C-E). Thus, STAT3 phosphorylation and target gene activation seems to be a major hallmark of a large subgroup of human MM. Constitutive GP130 signaling induces myeloma formation in a murine BM transduction-transplantation model. To test whether constitutive activation of GP130 signaling enables B cells to proliferate independently of cytokine stimulation, the IL-3-dependent Analysis of the malignant plasma cells revealed a t(12;15) translocation involving c-Myc (16). While Eμ-Myc transgenic mice (in which MYC expression is under control of the Eμ enhancer) develop aggressive pro-/pre-B cell lymphomas early in life (17), activationinduced deaminase-dependent expression of MYC in germinal center B cells leads to a high incidence of MM with a median survival of approximately 2 years (4). Transgenic mice expressing abnormally high levels of XBP-1, a protein involved in the terminal differentiation of B cells, develop monoclonal gammopathy of undetermined significance (MGUS), and some develop MM later in life (18). The Journal of Clinical Investigation R e s e a R c h a R t i c l e5In the present study, we showed that constitutive activation of GP130/JAK/STAT3 signal transduction in a retroviral murine BM transduction-transplantation model was sufficient to induce or facilitate MM development in mice. This model was characterized by very high penetrance and relatively short latency. Importantly, constitutive GP130 activation efficiently cooperated with MYC overexpression by driving cell growth and differentiation of malignant plasma cells. Our data indicate that constitutive GP130 signal transduction is a critical early step in myelomagenesis. Results STAT3 phosphorylation and target gene activation is a hallmark of human MM.Activation of the IL-6/IL-6R/GP130 complex is crucial for survival and proliferation of human myeloma (6,11,13), and the JAK/STAT3 pathway is a major target downstream of IL-6R/GP130 signaling (8,14). We therefore evaluated a series of BM biopsies from pati...

Cyclin-dependent kinase subunit 1 (Cks1) is a critical rate-limiting component of the Skp1-Cullin1-Skp2 (SCF(Skp2)) ubiquitin ligase that controls cell cycle inhibitor abundance. Cyclin-dependent kinase (Cdk) inhibitors (CKIs) regulate hematopoietic stem cell (HSC) self-renewal, regeneration after cytotoxic stress and tumor cell proliferation. We thus studied the role of Cks1 in HSC and in a prototypic stem cell disorder, chronic myeloid leukemia (CML). Cks1 transcript was highly expressed in Lin-Sca-1+Kit+ (LSK) HSC, and the loss resulted in accumulation of the SCF(Skp2)/Cks1 substrates p21, p27, p57 and p130 particularly in CD150+ LSK cells. This accumulation correlated with decreased proliferation and accumulation of Cks1(-/-) HSC, slower regeneration after stress and prolonged HSC quiescence. At the hematopoietic progenitor (HPC) level, loss of Cks1 sensitized towards apoptosis. In CML, Cks1 expression was increased, and treatment with the Abl kinase inhibitor, imatinib, reduced Cks1 expression. Also, we found that Cks1 is critical for Bcr-Abl-induced cytokine-independent clonogenic activity. In conclusion, our study presents a novel function of Cks1 in maintaining HSC/HPC homeostasis and shows that Cks1 is a possible target in therapies aimed at the SCF(Skp2)/Cks1 complex that controls CKI abundance and cancer cell proliferation.

The Cks1 component of the SCFSkp2 complex is necessary for p27Kip1 ubiquitylation and degradation. Cks1 expression is elevated in various B cell malignancies including Burkitt lymphoma and multiple myeloma. We have previously shown that loss of Cks1 results in elevated p27Kip1 levels and delayed tumor development in a mouse model of Myc-induced B cell lymphoma. Surprisingly, loss of Skp2 in the same mouse model also resulted in elevated p27Kip1 levels but exhibited no impact on tumor onset. This raises the possibility that Cks1 could have other oncogenic activities than suppressing p27Kip1. To challenge this notion we have targeted overexpression of Cks1 to B cells using a conditional retroviral bone marrow transduction-transplantation system. Despite potent ectopic overexpression, Cks1 was unable to promote B cell hyperproliferation or B cell malignancies, indicating that Cks1 is not oncogenic when overexpressed in B cells. Since Skp2 overexpression can drive T-cell tumorigenesis or other cancers we also widened the quest for oncogenic activity of Cks1 by ubiquitously expressing Cks1 in hematopoetic progenitors. At variance with c-Myc overexpression, which caused acute myeloid leukemia, Cks1 overexpression did not induce myeloproliferation or leukemia. Therefore, despite being associated with a poor prognosis in various malignancies, sole Cks1 expression is insufficient to induce lymphoma or a myeloproliferative disease in vivo.