ABSTRACT
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.
Subject(s)
Carcinoma, Squamous Cell , Drug Resistance, Neoplasm , Epithelial-Mesenchymal Transition , Skin Neoplasms , rho GTP-Binding Proteins , Actins/drug effects , Actins/metabolism , Carcinoma, Squamous Cell/drug therapy , Carcinoma, Squamous Cell/metabolism , Carcinoma, Squamous Cell/pathology , Cell Line, Tumor , Drug Resistance, Neoplasm/drug effects , Drug Resistance, Neoplasm/genetics , Epithelial-Mesenchymal Transition/drug effects , Proteomics , rho GTP-Binding Proteins/genetics , rho GTP-Binding Proteins/metabolism , Animals , Mice , Skin Neoplasms/drug therapy , Skin Neoplasms/metabolism , Skin Neoplasms/pathology , Gene Expression Profiling , GenomeABSTRACT
FAT1, which encodes a protocadherin, is one of the most frequently mutated genes in human cancers1-5. However, the role and the molecular mechanisms by which FAT1 mutations control tumour initiation and progression are poorly understood. Here, using mouse models of skin squamous cell carcinoma and lung tumours, we found that deletion of Fat1 accelerates tumour initiation and malignant progression and promotes a hybrid epithelial-to-mesenchymal transition (EMT) phenotype. We also found this hybrid EMT state in FAT1-mutated human squamous cell carcinomas. Skin squamous cell carcinomas in which Fat1 was deleted presented increased tumour stemness and spontaneous metastasis. We performed transcriptional and chromatin profiling combined with proteomic analyses and mechanistic studies, which revealed that loss of function of FAT1 activates a CAMK2-CD44-SRC axis that promotes YAP1 nuclear translocation and ZEB1 expression that stimulates the mesenchymal state. This loss of function also inactivates EZH2, promoting SOX2 expression, which sustains the epithelial state. Our comprehensive analysis identified drug resistance and vulnerabilities in FAT1-deficient tumours, which have important implications for cancer therapy. Our studies reveal that, in mouse and human squamous cell carcinoma, loss of function of FAT1 promotes tumour initiation, progression, invasiveness, stemness and metastasis through the induction of a hybrid EMT state.
Subject(s)
Cadherins/deficiency , Epithelial-Mesenchymal Transition/genetics , Gene Deletion , Neoplasm Metastasis/genetics , Neoplasms/genetics , Neoplasms/pathology , Adaptor Proteins, Signal Transducing/metabolism , Animals , Cadherins/genetics , Cadherins/metabolism , Carcinoma, Squamous Cell/genetics , Carcinoma, Squamous Cell/pathology , Disease Progression , Enhancer of Zeste Homolog 2 Protein/metabolism , Epithelial Cells/metabolism , Epithelial Cells/pathology , Epithelial-Mesenchymal Transition/drug effects , Gene Expression Regulation, Neoplastic , Humans , Hyaluronan Receptors/metabolism , Lung Neoplasms/genetics , Lung Neoplasms/pathology , Mesoderm/metabolism , Mesoderm/pathology , Mice , Neoplasm Metastasis/drug therapy , Neoplasms/drug therapy , Neoplastic Stem Cells/metabolism , Neoplastic Stem Cells/pathology , Phenotype , Phosphoproteins/analysis , Phosphoproteins/metabolism , Proteomics , SOXB1 Transcription Factors/metabolism , Signal Transduction , Skin Neoplasms/genetics , Skin Neoplasms/pathology , Transcription Factors/metabolism , YAP-Signaling Proteins , Zinc Finger E-box-Binding Homeobox 1/metabolism , src-Family Kinases/metabolismABSTRACT
The nongenetic mechanisms required to sustain malignant tumor state are poorly understood. During the transition from benign tumors to malignant carcinoma, tumor cells need to repress differentiation and acquire invasive features. Using transcriptional profiling of cancer stem cells from benign tumors and malignant skin squamous cell carcinoma (SCC), we identified the nuclear receptor NR2F2 as uniquely expressed in malignant SCC. Using genetic gain of function and loss of function in vivo, we show that NR2F2 is essential for promoting the malignant tumor state by controlling tumor stemness and maintenance in mouse and human SCC. We demonstrate that NR2F2 promotes tumor cell proliferation, epithelial-mesenchymal transition and invasive features, while repressing tumor differentiation and immune cell infiltration by regulating a common transcriptional program in mouse and human SCCs. Altogether, we identify NR2F2 as a key regulator of malignant cancer stem cell functions that promotes tumor renewal and restricts differentiation to sustain a malignant tumor state.
