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

Abstract

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.No conflicts of interest were declared. heterogeneous expression of keratins [10][11][12].Despite a large body of evidence that FOXM1 has a role in HNSCC [13][14][15][16], its oncogenic functions in this type of cancer are not yet sufficiently understood. In Figure 3. shRNA-mediated FOXM1 knockdown decreases the number of proliferating cells and facilitates progression towards a more differentiated-like phenotype. (A) H&E staining of CAL27 organotypic cultures demonstrating a squamous-like phenotype after 16 days of culture. Scale bar = 100 μm. (B) Representative pictures of immunostaining for a series of indicated differentiation markers in CAL27 organotypic cultures at day 16. Scale bar = 100 μm. (C) RT-qPCR analysis of organotypes showing a gradual decrease in FOXM1 and its targets CCNF and GTSE1 upon FOXM1 knockdown, while differentiation-related genes such as JUND and IVL were upregulated both by FOXM1 knockdown and by increased time of culture. The data shown are from one experiment. (D) RT-qPCR analysis of FOXM1 and IVL expression levels in a large series of CAL27 shCtr or shFOXM1 organotypic cultures showing a trend for IVL upregulation following FOXM1 knockdown. Each dot represents one organotype. (E) FOXM1 expression was reduced by culturing cells in 3D organotypes as demonstrated by the reduction of FOXM1 transcript level measured by RT-qPCR. Each data point represents one sample under one condition or the other. (F) Computer-assisted quantification of the number of Ki-67-positive cells detected by immunohistochemistry in shCtr and FOXM1-depleted organotypes. Each data point represents one analyzed field of the organotype. (G) Examples for the Ki-67 immunohistochemistry data quantified in panel F. Ki-67-positive cells were detected in the basal layer for both conditions at day 8. In the control, cycling cells were present throughout the organotype at day 16, while they were restricted to the basal layer upon FOXM1 downregu...

Overexpression of HPRT1 is associated with poor prognosis in head and neck squamous cell carcinoma

“…Moreover, several pieces of evidence have reported that upregulation of DNA replication and cell-cycle pathways genes in HNSCC [43][44][45]. Others have proposed that overexpression of the RRM2, GTSE1 and EXO1 genes in HNSCC have active roles in tumor progression and inhibition of the apoptosis pathway [46][47][48][49]. Some researchers have suggested that the HPRT1 gene, as a crucial component of the purine salvage pathway, plays a role in mediating the proliferation, autophagy and apoptosis-related processes in cancer cells [50][51][52].…”

Potential biomarkers and signaling pathways associated with the pathogenesis of primary salivary gland carcinoma: a bioinformatics study

“…Roh et al [ 52 ] demonstrated that FOXM1 contributes to cell cycle promoting function in HNSCC cell lines and is responsible for cell proliferation and metastasis of HNSCC cells. Also, shRNA-mediated FOXM1 knockdown led to the diminished proliferation and reduced cell migration in three-dimensional culture and xenograft tumor models.…”

Expression Analysis of Retinal G Protein-coupled Receptor and its Correlation with Regulation of the Balance between Proliferation and Aberrant Differentiation in Cutaneous Squamous Cell Carcinoma

“…Moreover, to further expand the understanding of the relationship between differentiation and RGR, we assessed the aberrant differentiation of SCC by involucrin staining. Involucrin, a marker of squamous differentiation, is expressed mainly by irreversibly differentiated keratinocytes in the stratum corneum and has been found to be markedly associated with aberrant differentiation in SCC ( 29 , 30 ). Comparison of RGR expression among different regions with different degrees of differentiation in the same sample showed that the degree of differentiation was inversely correlated with RGR expression, but positively correlated with involucrin expression.…”