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The tumor suppressor SMAD4 acts through WNT signaling in progression from benign lesions to oral squamous cell carcinoma

ABSTRACT: SMAD4 is a tumor suppressor mutated or silenced in multiple cancers including oral squamous cell carcinoma (OSCC). Human clinical samples and cell lines, mouse models and organoid culture were used to investigate the role that SMAD4 plays in progression from benign disease to invasive OSCC. Human OSCC lost detectable SMAD4 protein within tumor epithelium in 24% of cases and this loss correlated with worse progression free survival independent of other major clinical and pathological features. In a mouse model, Kras mutation induced benign papillomas while additional loss of Smad4 expression resulted in rapid development of invasive carcinoma. Examining regulatory pathways in organoids from SMAD4+ and SMAD4- mouse tumors, we found that either loss of SMAD4 or inhibition of TGFb signaling upregulated the WNT pathway and altered the extracellular matrix. The gene signature of the mouse tumor organoids lacking SMAD4 was highly similar to the gene signature of human head and neck squamous cell carcinoma. In summary, this work has uncovered novel mechanisms by which SMAD4 acts as a tumor suppressor in OSCC.

ORGANISM(S): Mus musculus

PROVIDER: GSE228584 | GEO | 2024/05/14

REPOSITORIES: GEO

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Project description:Carcinogenesis is a multistep process in which cells accumulate multiple genetic alterations, as they progress to a more malignant phenotype. It has been proposed that sequential accumulation of gene abnormalities in specific genes drives the transition from non-tumorous epithelia through preneoplastic lesion/benign tumor to cancer. Histologically, progression to invasive oral squamous cell carcinoma (OSCC) follows multistep ordered series beginning with mucosal epithelial cell hyperplasia, followed by dysplasia, carcinoma in situ and invasive carcinoma. It is therefore speculated that genetic alterations-mediated multistep carcinogenesis would be involved in OSCC development, but their detailed molecular mechanisms are unknown. Herein, we clarified the comprehensive gene expression patterns and carried out an enrichment analysis using DNA microarray data obtained from an OSCC pathological specimen, which consists of non-tumor region, carcinoma in situ lesion and invasive carcinoma lesion. Numerous numbers of gene expression and signal activation were altered in the OSCC development. Of them, the expression of p63 was increased and MEK/ERK-MAPK pathway was activated in carcinoma in situ lesion as well as in invasive carcinoma lesion. Immunohistochemical analyses revealed that p63 was initially upregulated in carcinoma in situ lesions and ERK was sequentially activated in invasive carcinoma lesions in OSCC specimens. ADP-ribosylation factor (ARF)-like 4c (ARL4C), the expression of which is reportedly induced by p63 and/or MEK/ERK-MAPK pathway in OSCC cells, has been shown to promote tumorigenesis. Immunohistochemically, in OSCC specimens, ARL4C was more frequently detected in tumor lesions, especially in invasive carcinoma lesions than in carcinoma in situ lesions. Additionally, ARL4C and phosphorylated ERK were merged at high frequency in invasive carcinoma lesions. Loss-of-function experiments using inhibitors and siRNAs revealed that p63 and EGFR-MEK/ERK-MAPK cooperatively induce ARL4C expression in OSCC cells. These results suggest that the stepwise activation of p63 and EGFR-MEK/ERK-MAPK contributes to OSCC tumor cell growth though regulation of ARL4C expression.

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The tumor suppressor SMAD4 acts through WNT signaling in progression from benign lesions to oral squamous cell carcinoma

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