Squamous Cell Carcinoma of the Oral Cavity and Oropharynx

TLN1: an oncogene associated with tumorigenesis and progression

Talin-1 (TLN1), encoded by the TLN1 gene, is a focal adhesion-related protein capable of binding various proteins in the cytoskeleton. It is also expressed at high levels in many cancers wherein it influences cellular adhesion and the activation of integrins. TLN1 is also capable of promoting tumor cell invasivity, proliferation, and metastatic progression, in addition to being a relevant biomarker and therapeutic target in certain cancers. The present review offers a comprehensive overview of current knowledge regarding TLN1 with respect to its structural properties, functions, and role in tumor development.

Rhopaloic acid A triggers mitochondria damage-induced apoptosis in oral cancer by JNK/BNIP3/Nix-mediated mitophagy

BACKGROUND

Oral squamous cell carcinoma (OSCC) is a frequently occurring type of head and neck cancer with a high mortality and morbidity rate. Rhopaloic acid A (RA), a terpenoid derived from sponges, has demonstrated a promising anti-tumor activity, but its effectiveness for treating OSCC remains unknown.

PURPOSE

The aim of this study was to investigate whether RA inhibits the growth of OSCC.

METHODS

Cell viability was evaluated using CCK-8 assays in OSCC cells (Ca9-22, HSC-3 and SAS) and in normal cells (HGF-1) treated with RA. DAPI staining, AO staining, JC-1 staining and immunofluorescence were used to determine apoptosis, mitochondrial membrane potential and autophagy in RA-treated OSCC cells. Protein expression levels were determined by western blotting. Furthermore, the anti-tumor effect of RA was confirmed in vivo using a zebrafish oral cancer xenotransplantation model.

RESULTS

OSCC cells had a significantly reduced viability after RA treatment, but normal cells were not affected. Treatment with RA caused chromatin condensation in OSCC cells, which increased their expression of autophagy- and apoptosis-related proteins. Furthermore, RA caused mitochondrial damage and increased autophagosome formation. Mitophagy was also induced by RA through the JNK/BNIP3/Nix/LC3B pathway. The JNK inhibitor SP600125 prevented both RA-mediated cell death and mitophagy of OSCC cells. A zebrafish xenograft model demonstrated that RA inhibits OSCC growth.

CONCLUSION

In conclusion, RA showed a potent anticancer activity in in vitro and in in vivo oral cancer models by promoting mitochondrial damage-induced apoptosis and mitophagy, which suggests that RA may be useful as a novel and effective treatment for OSCC.

P16 and HPV status in head and neck sarcomas and sarcomatoid carcinomas

Human papillomavirus (HPV)-positive oropharyngeal carcinoma is a distinct type of head and neck carcinoma with improved prognosis. p16 immunostaining is often used as a surrogate marker for HPV infection in this particular setting. The aim of this study is to estimate the prevalence of p16 staining and HPV infection in head and neck sarcomatoid carcinomas as well as head and neck sarcomas. 21 sarcomatoid carcinomas and 28 head and neck sarcomas were tested for p16 positivity using immunohistochemical staining, and for high-risk HPV infection using In situ hybridization (ISH). 24 % of sarcomatoid carcinomas and 21 % of sarcomas were positive for p16 staining. All 49 cases were negative for HPV ISH. The results confirm that p16 staining is not specific and may not be associated with HPV infection in non-oropharyngeal head and neck sites. They also indicate that non-oropharyngeal head and neck sarcomatoid carcinomas are not likely to be HPV related.

Difference between Keratinized- and Non-Keratinized-Originating Epithelium in the Process of Immune Escape of Oral Squamous Cell Carcinoma

Immune checkpoint inhibitors (ICIs), including anti-programmed cell death 1 ligand 1 (PD-L1) antibodies, are significantly changing treatment strategies for human malignant diseases, including oral cancer. Cancer cells usually escape from the immune system and acquire proliferative capacity and invasive/metastatic potential. We have focused on the two immune checkpoints, PD-1/PD-L1 and CD47/SIRPα, in the tumor microenvironment of oral squamous cell carcinoma (OSCC), performed a retrospective analysis of the expression of seven immune-related factors (PD-L1, PD-1, CD4, CD8, CD47, CD56 and CD11c), and examined their correlation with clinicopathological status. As a result, there were no significant findings relating to seven immune-related factors and several clinicopathological statuses. However, the immune checkpoint-related factors (PD-1, PD-L1, CD47) were highly expressed in non-keratinized epithelium-originated tumors when compared to those in keratinized epithelium-originated tumors. It is of interest that immunoediting via immune checkpoint-related factors was facilitated in non-keratinized sites. Several researchers reported that the keratinization of oral mucosal epithelia affected the immune response, but our present finding is the first study to show a difference in tumor immunity in the originating epithelium of OSCC, keratinized or non-keratinized. Tumor immunity, an immune escape status of OSCC, might be different in the originating epithelium, keratinized or non-keratinized.

Inhibition of autophagy initiation: A novel strategy for oral squamous cell carcinomas

BACKGROUND

Oral squamous cell carcinoma (OSCC) is one of the most common forms of oral cancer and is known to have poor prognostic outcomes. Autophagy is known to be associated with aggressive tumor biology of OSCC. Hence, this study aimed to develop a novel therapeutic strategy against OSCC by targeting the autophagic pathway.

METHODS

Immunoblotting, and confocal microscopy were used to examine the effect of tumor microenvironmental stressors on the autophagy activity. Cellular proliferation and migration assays were performed to assess the anti-cancer activity of standard chemotherapy and autophagy initiation inhibitors, either alone or in combination. High resolution mass-spectrometry based proteomic analysis was utilized to understand the mechanisms behind chemoresistance in OSCC models. Finally, immunohistochemistry was performed to determine associations between autophagy markers and clinicopathological characteristics.

RESULTS

Tumor microenvironmental stressors were shown to induce autophagy activity in OSCC cell lines. Novel combinations of chemotherapy and autophagy inhibitors as well as different classes of autophagy inhibitors were identified. Combination of MRT68921 and SAR405 demonstrated marked synergy in their anti-proliferative activity and also showed synergy with chemotherapy in chemoresistant OSCC cell models. Autophagy was identified as one of the key pathways involved in mediating chemoresistance in OSCC. Furthermore, TGM2 was identified as a key upstream regulator of chemoresistance in OSCC models. Finally, positive staining for autophagosome marker LC3 was shown to be associated with low histological grade OSCC.

CONCLUSION

In conclusion, this study identified a combination of novel autophagy inhibitors which can potently inhibit proliferation of both chemosensitive as well as chemoresistant OSCC cells and could be developed as a novel therapy against advanced OSCC tumors.

Diversity of the Origin of Cancer Stem Cells in Oral Squamous Cell Carcinoma and Its Clinical Implications

Simple Summary

Oral squamous cell carcinoma (OSCC) histopathologically accounts for ≥90% of oral cancer. In this review article, we focus on the diversity of the origin of OSCC and also discuss cancer stem cells (CSCs). CSCs are a subset of cancer cells that occupy a very small portion of the cancer mass and have characteristics of stem cells. When gene abnormalities accumulate in somatic stem cells, those cells transform into CSCs. CSCs as the origin of cancer then autonomously grow and develop into cancer. The histopathological phenotype of cancer cells is determined by the original characteristics of the somatic stem cells and/or surrounding environment. OSCC may be divided into the following three categories with different malignancy based on the origin of CSCs: cancer from oral epithelial stem cell-derived CSCs, cancer from stem cells in salivary gland-derived CSCs, and cancer from bone marrow-derived stem cell-derived CSCs.

Abstract

Oral squamous cell carcinoma (OSCC) histopathologically accounts for ≥90% of oral cancer. Many clinicopathological risk factors for OSCC have also been proposed, and postoperative therapy is recommended in guidelines based on cancer stage and other risk factors. However, even if the standard treatment is provided according to the guidelines, a few cases rapidly recur or show cervical and distant metastasis. In this review article, we focus on the diversity of the origin of OSCC. We also discuss cancer stem cells (CSCs) as a key player to explain the malignancy of OSCC. CSCs are a subset of cancer cells that occupy a very small portion of the cancer mass and have characteristics of stem cells. When gene abnormalities accumulate in somatic stem cells, those cells transform into CSCs. CSCs as the origin of cancer then autonomously grow and develop into cancer. The histopathological phenotype of cancer cells is determined by the original characteristics of the somatic stem cells and/or surrounding environment. OSCC may be divided into the following three categories with different malignancy based on the origin of CSCs: cancer from oral epithelial stem cell-derived CSCs, cancer from stem cells in salivary gland-derived CSCs, and cancer from bone marrow-derived stem cell-derived CSCs.

Emerging Role of Autophagy in the Development and Progression of Oral Squamous Cell Carcinoma

Autophagy is a cellular catabolic process, which is characterized by degradation of damaged proteins and organelles needed to supply the cell with essential nutrients. At basal levels, autophagy is important to maintain cellular homeostasis and development. It is also a stress responsive process that allows the cells to survive when subjected to stressful conditions such as nutrient deprivation. Autophagy has been implicated in many pathologies including cancer. It is well established that autophagy plays a dual role in different cancer types. There is emerging role of autophagy in oral squamous cell carcinoma (OSCC) development and progression. This review will focus on the role played by autophagy in relation to different aspects of cancer progression and discuss recent studies exploring the role of autophagy in OSCC. It will further discuss potential therapeutic approaches to target autophagy in OSCC.

CYLD mutation characterizes a subset of HPV-positive head and neck squamous cell carcinomas with distinctive genomics and frequent cylindroma-like histologic features

Mutations in the tumor suppressor CYLD, known to be causative of cylindromas, were recently described in a subset of high-risk (hr) HPV-positive head and neck squamous cell carcinomas (HNSCC). Pathologic and genetic characterization of these CYLD-mutant carcinomas, however, remains limited. Here, we investigated whether CYLD mutations characterize a histopathologically and genomically distinct subset of hrHPV-positive HNSCC. Comprehensive genomic profiling via hybrid capture-based DNA sequencing was performed on 703 consecutive head and neck carcinomas with hrHPV sequences, identifying 148 unique cases (21%) harboring CYLD mutations. Clinical data, pathology reports, and histopathology were reviewed. CYLD mutations included homozygous deletions (n = 61/148; 41%), truncations (n = 52; 35%), missense (n = 26; 18%) and splice-site (n = 9; 6%) mutations, and in-frame deletion (n = 1; 1%). Among hrHPV-positive HNSCC, the CYLD-mutant cohort showed substantially lower tumor mutational burden than CYLD-wildtype cases (n = 555) (median 2.6 vs. 4.4 mut/Mb, p < 0.00001) and less frequent alterations in PIK3CA (11% vs. 34%, p < 0.0001), KMT2D (1% vs. 16%, p < 0.0001), and FBXW7 (3% vs. 11%, p = 0.0018). Male predominance (94% vs. 87%), median age (58 vs. 60 years), and detection of HPV16 (95% vs. 89%) were similar. On available histopathology, 70% of CYLD-mutant HNSCC (98/141 cases) contained hyalinized material, consistent with basement membrane inclusions, within crowded aggregates of tumor cells. Only 7% of CYLD-wildtype cases demonstrated this distinctive pattern (p < 0.0001). Histopathologic patterns of CYLD-mutant HNSCC lacking basement membrane inclusions included nonkeratinizing (n = 22, 16%), predominantly nonkeratinizing (nonkeratinizing SCC with focal maturation; n = 10, 7%), and keratinizing (n = 11, 8%) patterns. The latter two groups showed significantly higher frequency of PTEN alterations compared with other CYLD-mutant cases (38% [8/21] vs. 7% [8/120], p = 0.0004). Within our cohort of hrHPV-positive HNSCCs, CYLD mutations were frequent (21%) and demonstrated distinctive clinical, histopathologic, and genomic features that may inform future study of prognosis and treatment.

Role of Autophagy in the Microenvironment of Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma, the most common type of oral cancer, affects more than 275,000 people per year worldwide. Oral squamous cell carcinoma is very aggressive, as most patients die after 3 to 5 years post-diagnosis. The initiation and progression of oral squamous cell carcinoma are multifactorial: smoking, alcohol consumption, and human papilloma virus infection are among the causes that promote its development. Although oral squamous cell carcinoma involves abnormal growth and migration of oral epithelial cells, other cell types such as fibroblasts and immune cells form the carcinoma niche. An underlying inflammatory state within the oral tissue promotes differential stress-related responses that favor oral squamous cell carcinoma. Autophagy is an intracellular degradation process that allows cancer cells to survive under stress conditions. Autophagy degrades cellular components by sequestering them in vesicles called autophagosomes, which ultimately fuse with lysosomes. Although several autophagy markers have been associated with oral squamous cell carcinoma, it remains unclear whether up- or down-regulation of autophagy favors its progression. Autophagy levels during oral squamous cell carcinoma are both timing- and cell-specific. Here we discuss how autophagy is required to establish a new cellular microenvironment in oral squamous cell carcinoma and how autophagy drives the phenotypic change of oral squamous cell carcinoma cells by promoting crosstalk between carcinoma cells, fibroblasts, and immune cells.

Preventive measures in oral cancer: An overview

Worldwide oral cancer is creating an alarming situation and it's a matter of global concern as it is the 11th most common carcinoma around the globe. After cardiovascular ailments, cancer is the next biggest killer. Approximately 90% of the total oral malignancies are squamous cell carcinomas. The etiological base of oral cancer is tobacco intake, smoking, smokeless tobacco (snuff or chewing tobacco), alcohol and areca nut intake, excessive sunlight exposure, reverse end smoking and Human Papilloma Virus (HPV). The treatment measures for oral cancer are very costly and affordability is low. So, taking preventive measures at the first place itself is of immense importance. Preventive measure is a multidisciplinary approach involving co-ordinated efforts from all the sectors of the society. The preventive measures are categorised into primary, secondary and tertiary measures. Along with the various screening tests employed to detect oral cancer the review focuses on biomarkers, melatonin, tea constituents, polyphenols, chemoprevention, Chios mastic gum extract, Poly (ADP-ribose) Polymerase 1 (PARP1) targeted optical imaging agent, and their role in oral cancer prevention and control. The review gives a brief outline on the preventive measures to be adopted to help prevent oral cancer and improve the quality of life.