The role of the p38-FOXM1 pathway in the regulation of cancer cell invasion

Head and neck cancer is the sixth most common cancer worldwide and associated with a poor clinical prognosis, due to development of recurrent tumors and metastasis. Tumor recurrence and low patient survival are strongly linked with the ability of tumor cells to invade and infiltrate the surrounding tissue. Stress-activated protein kinases (SAPK), particularly p38, are known to regulate a wide range of cellular phenotypes, including cell invasion via the activity of secreted proteases. The proliferation-associated Forkhead box protein M1 (FOXM1) transcription factor, a p38 downstream target, plays a role in the development and growth of many cancer types. However, only very little is known about the role of p38 and FOXM1 in invasive processes of head and neck cancer and the exact mechanism underlying this process. In this work we examined the downstream events of p38 signaling primarily focusing on the role of FOXM1 transcription factor in regulation of the urokinase-type plasminogen activator (uPA) gene and invasion of head and neck squamous cell carcinoma (HNSCC) cells. Using different HNSCC cell lines, we confirm that p38 regulates FOXM1 expression and provide evidence that p38 signaling driven in vitro invasion of HNSCC cells requires FOXM1 expression. Furthermore, siRNA-mediated FOXM1 knockdown is sufficient to inhibit the invasive behavior of HNSCC cells in vitro. By using reporter gene assays, bioinformatical analysis of the publically available ChIP-Seq data, chromatin immunoprecipitation assays, and transplantation-based mouse model of oral cancer, we identified the molecular mechanism of FOXM1-mediated invasion of HNSCC cells. FOXM1 controls the uPA-dependent invasion via activation of c-Fos and thus drives AP-1 activity on the uPA promoter, which enhances its expression and proteolytic activity. Further, an activated Ras signaling is necessary for a potent FOXM1-mediated uPA activity and tumor formation. The data are supported by a bioinformatical study, demonstrating concomitant up-regulation of FOXM1 and uPA in oral dysplasia and SCCs of head and neck, oesophagus, lung and cervix. In the mouse model of oral cancer we show that uPA expression is upregulated in recurrent tumors compared to primary tumors, giving further evidence for a crucial role of the p38-FOXM1-uPA axis in the development of recurrent tumors. Taken together, we conclude that the stress signalling cascade requires a FOXM1-dependent intermediate step preceding the activation of AP-1 transcription factor to enhance invasive behaviour of tumor cells. This novel mechanism promotes invasion of HNSCC and may provide a potential target for the adjuvant therapy of these highly invasive cancers

Opposing function of MYBBP1A in proliferation and migration of head and neck squamous cell carcinoma cells

BACKGROUND: Head and neck squamous cell carcinoma (HNSCC) is one of the most prevalent and lethal cancers worldwide and mortality mostly results from loco-regional recurrence and metastasis. Despite its significance, our knowledge on molecular, cellular and environmental mechanisms that drive disease pathogenesis remains largely elusive, and there are limited therapeutic options, with only negligible clinical benefit. METHODS: We applied global gene expression profiling with samples derived from a recently established mouse model for oral cancer recurrence and identified a list of genes with differential expression between primary and recurrent tumors. RESULTS: One differentially expressed gene codes for Myb-binding protein 1a (MYBBP1A), which is known as a transcriptional co-regulator that physically interacts with nuclear transcription factors, such as NFκB and p53. We confirmed significantly reduced MYBBP1A protein levels on tissue sections of recurrent mouse tumors compared to primary tumors by immunohistochemistry, and found aberrant MYBBP1A protein levels also in tumor samples of HNSCC patients. Interestingly, silencing of MYBBP1A expression in murine SCC7 and in human HNSCC cell lines elicited increased migration but decreased cell growth. CONCLUSION: We provide experimental evidence that MYBBP1A is an important molecular switch in the regulation of tumor cell proliferation versus migration in HNSCC and it will be a major challenge for the future to proof the concept whether regulation MYBBP1A expression and/or function could serve as a novel option for anti-cancer therapy

The transcription factor FOXM1 regulates the balance between proliferation and aberrant differentiation in head and neck squamous cell carcinoma

Sustained expression of FOXM1 is a hallmark of nearly all human cancers including squamous cell carcinomas of the head and neck (HNSCC). HNSCCs partially preserve the epithelial differentiation program, which recapitulates fetal and adult traits of the tissue of tumor origin but is deregulated by genetic alterations and tumor-supporting pathways. Using shRNA-mediated knockdown, we demonstrate a minimal impact of FOXM1 on proliferation and migration of HNSCC cell lines under standard cell culture conditions. However, FOXM1 knockdown in three-dimensional (3D) culture and xenograft tumor models resulted in reduced proliferation, decreased invasion, and a more differentiated-like phenotype, indicating a context-dependent modulation of FOXM1 activity in HNSCC cells. By ectopic overexpression of FOXM1 in HNSCC cell lines, we demonstrate a reduced expression of cutaneous-type keratin K1 and involucrin as a marker of squamous differentiation, supporting the role of FOXM1 in modulation of aberrant differentiation in HNSCC. Thus, our data provide a strong rationale for targeting FOXM1 in HNSCC. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd

Foxm1 expression in prostate epithelial cells is essential for prostate carcinogenesis.

The treatment of advanced prostate cancer (PCa) remains a challenge. Identification of new molecular mechanisms that regulate PCa initiation and progression would provide targets for the development of new cancer treatments. The Foxm1 transcription factor is highly up-regulated in tumor cells, inflammatory cells, and cells of tumor microenvironment. However, its functions in different cell populations of PCa lesions are unknown. To determine the role of Foxm1 in tumor cells during PCa development, we generated two novel transgenic mouse models, one exhibiting Foxm1 gain-of-function and one exhibiting Foxm1 loss-of-function under control of the prostate epithelial-specific Probasin promoter. In the transgenic adenocarcinoma mouse prostate (TRAMP) model of PCa that uses SV40 large T antigen to induce PCa, loss of Foxm1 decreased tumor growth and metastasis. Decreased prostate tumorigenesis was associated with a decrease in tumor cell proliferation and the down-regulation of genes critical for cell proliferation and tumor metastasis, including Cdc25b, Cyclin B1, Plk-1, Lox, and Versican. In addition, tumor-associated angiogenesis was decreased, coinciding with reduced Vegf-A expression. The mRNA and protein levels of 11β-Hsd2, an enzyme playing an important role in tumor cell proliferation, were down-regulated in Foxm1-deficient PCa tumors in vivo and in Foxm1-depleted TRAMP C2 cells in vitro. Foxm1 bound to, and increased transcriptional activity of, the mouse 11β-Hsd2 promoter through the -892/-879 region, indicating that 11β-Hsd2 was a direct transcriptional target of Foxm1. Without TRAMP, overexpression of Foxm1 either alone or in combination with inhibition of a p19(ARF) tumor suppressor caused a robust epithelial hyperplasia, but was insufficient to induce progression from hyperplasia to PCa. Foxm1 expression in prostate epithelial cells is critical for prostate carcinogenesis, suggesting that inhibition of Foxm1 is a promising therapeutic approach for prostate cancer chemotherapy