Hedgehog pathway proteins SMO and GLI expression as prognostic markers in head and neck squamous cell carcinoma

Primary cilia-associated signalling in squamous cell carcinoma of head and neck region

Squamous cell carcinoma (SCC) of the head and neck originates from the mucosal lining of the upper aerodigestive tract, including the lip, tongue, nasopharynx, oropharynx, larynx and hypopharynx. In this review, we summarise what is currently known about the potential function of primary cilia in the pathogenesis of this disease. As primary cilia represent a key cellular structure for signal transduction and are related to cell proliferation, an understanding of their role in carcinogenesis is necessary for the design of new treatment approaches. Here, we introduce cilia-related signalling in head and neck squamous cell carcinoma (HNSCC) and its possible association with HNSCC tumorigenesis. From this point of view, PDGF, EGF, Wnt and Hh signalling are discussed as all these pathways were found to be dysregulated in HNSCC. Moreover, we review the clinical potential of small molecules affecting primary cilia signalling to target squamous cell carcinoma of the head and neck area.

Elucidating Hedgehog pathway's role in HNSCC progression: insights from a 6-gene signature

With the emergence of targeted inhibition strategies for Hedgehog signaling in cancer, multiple Hedgehog signaling pathway-related biomarkers have become the focus of research. SsGSEA algorithm was employed to analyze the Hedgehog pathway scores of samples in TCGA-HNSC dataset and divide them into two groups. Weighted co-expression network analysis was performed to identify modules strongly associated with the Hedgehog pathway. Differentially up-regulated genes in tumor samples in comparison to the normal ones were screened by Limma, in which genes belonging to modules strongly related to Hedgehog pathway were further filtered by LASSO reduction and multivariate Cox regression analysis to develop a model. ESTIMATE and CIBERSORT were served to characterize the tumor microenvironment (TME). TIDE assessed immunotherapy response. Hedgehog pathway activity was significantly higher in head and neck squamous cell carcinoma (HNSCC) tissues than in normal tissues and was correlated with HNSCC survival, glycan, cofactors and vitamins, drug metabolism, and matrix scores. Six genes (SLC2A3, EFNB2, OAF, COX4I2, MT2A and TXNRD1) were captured to form a Hedgehog associated 6-gene signature, and the resulting risk score was an independent indicator of HNSCC prognosis. It was significantly positively correlated with stromal score, metabolism, angiogenesis and inflammatory response. Patients in low-risk group with a low TIDE score had higher immunotherapy sensitivity relative to those in high-risk group. This study revealed novel findings of the Hedgehog pathway in HNSCC progression and opened up a Hedgehog pathology-related signature to help identify risk factors contributing to HNSCC progression and help predict immunotherapy outcomes.

New insights into RAS in head and neck cancer

RAS genes are known to be dysregulated in cancer for several decades, and substantial effort has been dedicated to develop agents that reduce RAS expression or block RAS activation. The recent introduction of RAS inhibitors for cancer patients highlights the importance of comprehending RAS alterations in head and neck cancer (HNC). In this regard, we examine the published findings on RAS alterations and pathway activations in HNC, and summarize their role in HNC initiation, progression, and metastasis. Specifically, we focus on the intrinsic role of mutated-RAS on tumor cell signaling and its extrinsic role in determining tumor-microenvironment (TME) heterogeneity, including promoting angiogenesis and enhancing immune escape. Lastly, we summarize the intrinsic and extrinsic role of RAS alterations on therapy resistance to outline the potential of targeting RAS using a single agent or in combination with other therapeutic agents for HNC patients with RAS-activated tumors.

The Role of Hedgehog Signaling Pathway in Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC) is the sixth leading malignancy worldwide, with a poor prognosis and limited treatment options. Molecularly targeted therapies for HNSCC are still lacking. However, recent reports provide novel insights about many molecular alterations in HNSCC that may be useful in future therapies. Therefore, it is necessary to identify new biomarkers that may provide a better prediction of the disease and promising targets for personalized therapy. The poor response of HNSCC to therapy is attributed to a small population of tumor cells called cancer stem cells (CSCs). Growing evidence indicates that the Hedgehog (HH) signaling pathway plays a crucial role in the development and maintenance of head and neck tissues. The HH pathway is normally involved in embryogenesis, stem cell renewal, and tissue regeneration. However, abnormal activation of the HH pathway is also associated with carcinogenesis and CSC regulation. Overactivation of the HH pathway was observed in several tumors, including basal cell carcinoma, that are successfully treated with HH inhibitors. However, clinical studies about HH pathways in HNSCC are still rare. In this review, we summarize the current knowledge and recent advances regarding the HH pathway in HNSCC and discuss its possible implications for prognosis and future therapy.

Keratin19 promotes pancreatic cancer progression and poor prognosis via activating the Hedgehog pathway

Pancreatic cancer is a serious threat to human health, with strong invasiveness, rapid progression and poor prognosis. Tumors expressing keratin 19 (K19) have stronger invasiveness and a worse prognosis. However, the role and mechanism of K19 in pancreatic cancer have remained largely elusive. In the present study, K19 expression was detected in pancreatic cancer tissues, its effect on proliferation, apoptosis and metastasis of pancreatic cancer at the cellular, in vivo preclinical and clinical levels was evaluated and its effect on the Hedgehog pathway was analyzed. K19 was significantly overexpressed in pancreatic cancer, promoted pancreatic cancer proliferation and metastasis, inhibited tumor cell apoptosis and was associated with poor prognosis. Mechanistically, these effects were mediated through the activation of the Hedgehog pathway. In conclusion, K19 may be a novel target molecule for pancreatic cancer treatment.

Targeted therapy for head and neck cancer: signaling pathways and clinical studies

Head and neck cancer (HNC) is malignant, genetically complex and difficult to treat and is the sixth most frequent cancer, with tobacco, alcohol and human papillomavirus being major risk factors. Based on epigenetic data, HNC is remarkably heterogeneous, and treatment remains challenging. There is a lack of significant improvement in survival and quality of life in patients with HNC. Over half of HNC patients experience locoregional recurrence or distal metastasis despite the current multiple traditional therapeutic strategies and immunotherapy. In addition, resistance to chemotherapy, radiotherapy and some targeted therapies is common. Therefore, it is urgent to explore more effective and tolerable targeted therapies to improve the clinical outcomes of HNC patients. Recent targeted therapy studies have focused on identifying promising biomarkers and developing more effective targeted therapies. A well understanding of the pathogenesis of HNC contributes to learning more about its inner association, which provides novel insight into the development of small molecule inhibitors. In this review, we summarized the vital signaling pathways and discussed the current potential therapeutic targets against critical molecules in HNC, as well as presenting preclinical animal models and ongoing or completed clinical studies about targeted therapy, which may contribute to a more favorable prognosis of HNC. Targeted therapy in combination with other therapies and its limitations were also discussed.

Checkpoint Inhibitors in Cancer Therapy: Clinical Benefits for Head and Neck Cancers

Recently, considerable progress has been achieved in cancer immunotherapy. Targeted immune checkpoint therapies have been established for several forms of cancers, which resulted in a tremendous positive impact on patient survival, even in more advanced tumor stages. With a better understanding of cellular responses to immune checkpoint therapies, it will soon be feasible to find targeted compounds which will make personalized medicine practicable. This is a great opportunity, but it also sets tremendous challenges on both the scientific and clinical aspects. Head and neck tumors evade immune surveillance through various mechanisms. They contain fewer lymphocytes (natural killer cells) than normal tissue with an accumulation of immunosuppressive regulatory T cells. Standard therapies for HNSCC, such as surgery, radiation, and chemotherapy, are becoming more advantageous by targeting immune checkpoints and employing combination therapies. The purpose of this review is to provide an overview of the expanded therapeutic options, particularly the combination of immune checkpoint inhibition with various conventional and novel therapeutics for head and neck tumor patients.

The Role of Smoothened-Dependent and -Independent Hedgehog Signaling Pathway in Tumorigenesis

The Hedgehog (Hh)-glioma-associated oncogene homolog (GLI) signaling pathway is highly conserved among mammals, with crucial roles in regulating embryonic development as well as in cancer initiation and progression. The GLI transcription factors (GLI1, GLI2, and GLI3) are effectors of the Hh pathway and are regulated via Smoothened (SMO)-dependent and SMO-independent mechanisms. The SMO-dependent route involves the common Hh-PTCH-SMO axis, and mutations or transcriptional and epigenetic dysregulation at these levels lead to the constitutive activation of GLI transcription factors. Conversely, the SMO-independent route involves the SMO bypass regulation of GLI transcription factors by external signaling pathways and their interacting proteins or by epigenetic and transcriptional regulation of GLI transcription factors expression. Both routes of GLI activation, when dysregulated, have been heavily implicated in tumorigenesis of many known cancers, making them important targets for cancer treatment. Hence, this review describes the various SMO-dependent and SMO-independent routes of GLI regulation in the tumorigenesis of multiple cancers in order to provide a holistic view of the paradigms of hedgehog signaling networks involving GLI regulation. An in-depth understanding of the complex interplay between GLI and various signaling elements could help inspire new therapeutic breakthroughs for the treatment of Hh-GLI-dependent cancers in the future. Lastly, we have presented an up-to-date summary of the latest findings concerning the use of Hh inhibitors in clinical developmental studies and discussed the challenges, perspectives, and possible directions regarding the use of SMO/GLI inhibitors in clinical settings.

GANT61 and Lithium Chloride Inhibit the Growth of Head and Neck Cancer Cell Lines Through the Regulation of GLI3 Processing by GSK3β

Several signaling pathways are aberrantly activated in head and neck squamous cell carcinoma (HNSCC), including the Hedgehog-Gli (HH-GLI), WNT, EGFR, and NOTCH pathways. The HH-GLI pathway has mostly been investigated in the context of canonical signal transduction and the inhibition of the membrane components of the pathway. In this work we investigated the role of downstream inhibitors GANT61 and lithium chloride (LiCl) on cell viability, wound closure, and colony forming ability of HNSCC cell lines. Five HNSCC cell lines were treated with HH-GLI pathway inhibitors affecting different levels of signal transduction. GANT61 and LiCl reduce the proliferation and colony formation capabilities of HNSCC cell lines, and LiCl has an additional effect on wound closure. The major effector of the HH-GLI signaling pathway in HNSCC is the GLI3 protein, which is expressed in its full-length form and is functionally regulated by GSK3β. LiCl treatment increases the inhibitory Ser9 phosphorylation of the GSK3β protein, leading to increased processing of GLI3 from full-length to repressor form, thus inhibiting HH-GLI pathway activity. Therefore, downstream inhibition of HH-GLI signaling may be a promising therapeutic strategy for HNSCC.

Identification of new hypoxia-regulated epithelial-mesenchymal transition marker genes labeled by H3K4 acetylation

Hypoxia-induced epithelial-mesenchymal transition (EMT) involves the interplay between chromatin modifiers histone deacetylase 3 (HDAC3) and WDR5. The histone mark histone 3 lysine 4 acetylation (H3K4Ac) is observed in the promoter regions of various EMT marker genes (eg, CDH1 and VIM). To further define the genome-wide location of H3K4Ac, a chromatin immunoprecipitation followed by massively parallel DNA sequencing (ChIP-seq) analysis was performed using a head and neck squamous cell carcinoma (HNSCC) FaDu cell line under normoxia and hypoxia. H3K4Ac was found to be located mainly around the transcription start site. Coupled with analysis of gene expression by RNA sequencing and using a HDAC3 knockdown cell line, 10 new genes (BMI1, GLI1, SMO, FOXF1, SIRT2, etc) that were labeled by H3K4Ac and regulated by HDAC3 were identified. Overexpression or knockdown of GLI1/SMO increased or repressed the in vitro migration and invasion activity in OECM-1/FaDu cells, respectively. In HNSCC patients, coexpression of GLI1 and SMO in primary tumors correlated with metastasis. Our results identify new EMT marker genes that may play a significant role in hypoxia-induced EMT and metastasis and further provide diagnostic and prognostic implications.

Hedgehog pathway proteins SMO and GLI expression as prognostic markers in head and neck squamous cell carcinoma

Aims

Because the hedgehog signalling pathway plays a major role in many types of cancer and can nowadays be targeted by specific compounds, we aimed to investigate the role of this pathway in squamous cell carcinoma of the head and neck.

Methods and results

Ninety‐eight treatment‐naive head and neck cancer specimens were immunohistologically stained for SMO, GLI‐1, p53 and p16 expression and correlated with clinicopathological factors. Immunoreactivity for SMO and GLI‐1 was found in 20 (20.4%) and 52 (53.1%) cases of tumours, respectively. SMO expression correlated with GLI‐1 expression (ρ = 0.258, P = 0.010) in univariate and multivariate analysis (P = 0.007, t = 2.81). In univariate analysis, high SMO expression was associated with shorter overall survival (HR = 0.56; 95% CI = 0.32–0.98; P = 0.044) and disease‐free survival (HR = 0.53; 95% CI = 0.30–0.95; P = 0.034). In multivariate cox regression analysis SMO expression showed a trend towards an independent predictor for shorter overall survival (HR = 0.57; 95% CI = 0.30–1.05; P = 0.072) and disease‐free survival (HR = 0.53; 95% CI = 0.28–1.02; P = 0.056). In head and neck cancer patients with low tumour p16 expression, SMO expression was an independent factor for overall survival (HR = 0.49; 95% CI = 0.24–0.98; P = 0.043) and disease‐free survival (HR = 0.45; 95% CI = 0.22‐0.96; P = 0.037).

Conclusion

Although it needs to be confirmed in larger cohorts, our results suggest that targeting SMO might be a potentially therapeutic option in patients with head and neck cancer. In line, molecular pathological analyses including mutation analysis in the hedgehog pathway might point to additional therapeutic leads.