RESUMO
FOXM1 is an oncogenic transcriptional factor and includes several isoforms generated by alternative splicing. Inclusion of alternative exon 9 produces FOXM1a, a transcriptionally inactive isoform. However, the role of FOXM1a in tumorigenesis remains unknown. In addition, the regulatory mechanisms of exon 9 splicing are also unclear. In the present study, we found that overexpression of FOXM1a significantly reduced cell proliferation and colony formation of oral squamous cell carcinoma (OSCC) cell proliferation in vitro. Importantly, OSCC cells with FOXM1a overexpression showed significantly slower tumor formation in nude mice. Moreover, we identified a U-rich exonic splicing suppressor (ESS) which is responsible for exon 9 skipping. Splicing factor heterogeneous nuclear ribonucleoprotein C (hnRNP C) can bind to the ESS and suppress exon 9 inclusion and FOXM1a expression. Silence of hnRNP C also significantly suppresses OSCC cell proliferation. HnRNP C is significantly co-expressed with FOXM1 in cancers. Our study uncovered a novel regulatory mechanism of oncogene FOXM1 expression in OSCC.
Assuntos
Proteína Forkhead Box M1 , Ribonucleoproteínas Nucleares Heterogêneas Grupo C , Neoplasias Bucais , Carcinoma de Células Escamosas de Cabeça e Pescoço , Animais , Camundongos , Processamento Alternativo , Ribonucleoproteínas Nucleares Heterogêneas Grupo C/genética , Ribonucleoproteínas Nucleares Heterogêneas Grupo C/metabolismo , Camundongos Nus , Neoplasias Bucais/genética , Oncogenes , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Carcinoma de Células Escamosas de Cabeça e Pescoço/genética , Humanos , Proteína Forkhead Box M1/genética , Proteína Forkhead Box M1/metabolismoRESUMO
Oral squamous cell carcinoma (OSCC) is one of the most common malignancies in the world, with a high mortality rate. RAN is a member of the Ras GTPase family and is overexpressed in a range of cancers, however, the relationship between RAN and OSCC is rarely reported. In this study, we found that RAN is overexpressed in OSCC tissues. RAN inhibition retarded OSCC cell proliferation and led to apoptosis and cell cycle arrest. Knockdown of RAN inhibited tumor growth in vivo. Strikingly, we found that RAN and oncogene Y-box binding protein-1 (YBX1) are positively associated with the immune infiltrates of CD4+ Th2 cells in multiple types of cancer, and can promote IL-4 expression. IL-4 treatment can partially rescue RAN knockdown-induced cell apoptosis in OSCC cells. Moreover, overexpression of RAN could rescue cell growth inhibition caused by knockdown of YBX1. Furthermore, patients with low expression of both RAN and YBX1 had better overall survival than others. Collectively, these findings indicate that RAN is a target of YBX1. RAN and YBX1 are required for cell proliferation and IL-4 expression. RAN and YBX1 are co-expressed and can serve as potential co-biomarkers for poor prognosis in OSCC.
Assuntos
Biomarcadores Tumorais/metabolismo , Carcinoma de Células Escamosas/patologia , Regulação Neoplásica da Expressão Gênica , Interleucina-4/metabolismo , Neoplasias Bucais/patologia , Proteína 1 de Ligação a Y-Box/metabolismo , Proteína ran de Ligação ao GTP/metabolismo , Animais , Apoptose , Biomarcadores Tumorais/genética , Carcinoma de Células Escamosas/genética , Carcinoma de Células Escamosas/metabolismo , Ciclo Celular , Movimento Celular , Proliferação de Células , Feminino , Humanos , Interleucina-4/genética , Masculino , Camundongos , Camundongos Nus , Pessoa de Meia-Idade , Neoplasias Bucais/metabolismo , Prognóstico , Estudos Retrospectivos , Taxa de Sobrevida , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de Xenoenxerto , Proteína 1 de Ligação a Y-Box/genética , Proteína ran de Ligação ao GTP/genéticaRESUMO
STAT3 plays very important roles in the initiation and development of tumors. Despite of extensive studies in repressing its activation and function via multiple ways, so far, there are few effective therapeutic methods to inhibit STAT3 in the clinic. STAT3 has two isoforms generated by alternative splicing of exon 23. STAT3α is the longer isoform and encodes the full-length oncogenic STAT3α protein. STAT3ß is shorter and encodes the truncated and tumor-suppressive STAT3ß protein. It remains unknown how the alternative splicing of STAT3 exon 23 is regulated. Here, we discovered that there is an exonic splicing suppressor (ESS) in exon 23. Importantly, splicing factor PCBP1 binds to this ESS. Overexpression of PCBP1 significantly reduced the proportion of STAT3α /STAT3ß isoforms and the expression of STAT3α protein. Moreover, increased PCBP1 inhibited the growth of oral squamous cell carcinoma and breast cancer cells, and the expression of STAT3 target genes. Our results demonstrated that PCBP1 is the key splicing factor that promotes the switch from oncogenic isoform STAT3α to tumor-suppressive isoform STAT3ß. Our results pave the way for finding new anti-STAT3 methods for cancer treatment.
Assuntos
Proteínas de Ligação a DNA/fisiologia , Proteínas de Ligação a RNA/fisiologia , Fator de Transcrição STAT3/genética , Processamento Alternativo , Sítios de Ligação , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Carcinoma de Células Escamosas/genética , Carcinoma de Células Escamosas/patologia , Linhagem Celular Tumoral , Proliferação de Células , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/metabolismo , Éxons , Regulação da Expressão Gênica , Humanos , Neoplasias Bucais/genética , Neoplasias Bucais/patologia , Isoformas de Proteínas/química , Isoformas de Proteínas/metabolismo , Isoformas de Proteínas/fisiologia , Proteínas de Ligação a RNA/química , Proteínas de Ligação a RNA/metabolismo , Sequências Reguladoras de Ácido Nucleico , Fator de Transcrição STAT3/química , Análise de Sequência de DNA , Survivina/genética , Survivina/metabolismo , Proteína bcl-X/genética , Proteína bcl-X/metabolismoRESUMO
Antisense oligonucleotides (ASOs) have been widely used to regulate alternative splicing of pre-mRNA by targeting splice sites, branch points, or exonic splice enhancers to increase exon skipping or intron retention. So far, few studies have used ASOs to block exonic splicing suppressor (ESS) and increase exon inclusion. Previously, we demonstrated that serine and arginine rich splicing factor 3 (SRSF3) (also called SRp20) is an oncogene. The inclusion of its alternative exon 4 down-regulates its expression. An ESS motif is responsible for the skipping of alternative exon 4. Here, we used an economical method to screen effective anti-ESS ASO. We discovered that an ASO targeting the ESS motif can promote the inclusion of exon 4, reduce SRSF3 expression, and inhibit cell growth in oral cancer cells. Our results suggested that using anti-ESS ASOs can efficiently increase exon inclusion and be used as a potential anti-cancer drug.
