Prognostic implications of the phosphatidylinositol 3-kinase/Akt signaling pathway in oral squamous cell carcinoma: overexpression of p-mTOR indicates an adverse prognosis

Exploring the potential of dietary factors and plant extracts as chemopreventive agents in oral squamous cell carcinoma treatment

Oral cancer, particularly oral squamous cell carcinoma (OSCC), is a prevalent malignancy having a significant fatality rate worldwide. Despite advancements in conventional treatment modalities, the overall survival rate for OSCC remains low. Therefore, there is a critical need to explore alternative therapeutic approaches that can improve patient outcomes. This review focuses on the potential of dietary factors and plant extracts as chemopreventive agents in treating oral cancer. These compounds possess diverse biological functions encompassing a range of attributes, such as antioxidative, anti-inflammatory, and anticancer capabilities. By targeting multiple cellular pathways involved in carcinogenesis, they possess the capacity to hinder tumor growth and development, promote programmed cell death, and impede the progression of oral cancer. Signaling pathways targeted by natural compounds that have been included in this review include Akt/mTOR/NF-κB signaling, Hippo-Tafazzin signaling pathway, notch signaling pathway, mitochondrial pathway, and Sonic Hedgehog pathway.

Role of tissue markers associated with tumor microenvironment in the progression and immune suppression of oral squamous cell carcinoma

Head and neck cancers (HNC) continues to dominate major cancers contributing to  mortality worldwide. Squamous cell carcinoma is the major type of HNC. Oral Squamous Cell Carcinoma grouped under HNC is a malignant tumor occurring in the oral cavity. The primary risk factors of OSCC are tobacco, alcohol consumption, etc. This review focuses on modulations, mechanisms, growth and differentiation of oral squamous cell carcinoma. Cancer cell surrounds itself with a group of elements forming a favorable environment known as tumor microenvironment (TME). It consists of numerous cells which includes immune cells, blood cells and acellular components that are responsible for the progression, immunosuppression, metastasis and angiogenesis of cancer. This review highlights the most important tissue biomarkers (mTOR, CAF, FOXp3, CD163, CD33, CD34) that are associated with TME cells. mTOR remains as the primary regulator responsible in cancer and its importance towards immune-suppression is highlighted. Tumor-associated macrophages associated with cancer development and its relationship with immunomodulatory mechanism and Tregs, which are potential blockers of immune response and its mechanism and aberrations are discussed. Cancer-associated fibroblasts that are a part of TME and their role in evading the immune response and myeloid derived suppressor cells that have slight control over the immune response and their mechanism in the tumor progression is further explained. These markers have been emphasised as therapeutic targets and are currently in different stages of clinical trials.

Role of PI3K/AKT pathway in squamous cell carcinoma with an especial focus on head and neck cancers

PI3K/AKT pathway is an important pathway in the carcinogenesis since it has central impacts in the regulation of metabolic pathways, cell proliferation and survival, gene expression and protein synthesis. This pathway has been reported to be dysregulated in several types of cancers. In the current review, we summarize the role of this signaling pathway in squamous cell carcinomas (SCCs) originated from different parts of body cervix, oral cavity, head and neck and skin. The data presented in the current review shows the impact of dysregulation of PI3K/AKT pathway in survival of patients with SCC. Moreover, targeted therapies against this pathway have been found to be effective in reduction of tumor burden both in animal models and clinical settings. Finally, a number of molecules that regulate PI3K/AKT pathway can be used as diagnostic markers for different types of SCCs.

Chrysophanol Suppresses Cell Growth via mTOR/PPAR-α Regulation and ROS Accumulation in Cultured Human Tongue Squamous Carcinoma SAS Cells

Oral cancer, a type of head and neck cancer, can pose a significant risk of death unless diagnosed and treated early. Alternative treatments are urgently needed owing to the high mortality rate, limitations of conventional treatments, and many complications. The anthraquinone compound chrysophanol acts as a tumor suppressor on some types of cancer cells. To date, it has not been clarified how chrysophanol affects human tongue squamous carcinoma. This study was aimed to examine the effects of chrysophanol on oral cancer treatment. The results show that chrysophanol caused cell death, reduced the expression of the mammalian target of rapamycin (mTOR)/peroxisome proliferator-activated receptor-alpha (PPAR-α), and increased reactive oxygen species (ROS) production. We also used two ion chelators, deferoxamine (DFO) and liproxstatin-1 (Lipro), to further determine whether chrysophanol inhibits cell growth and regulates mTOR/PPAR-α expression and ROS production, both of which are involved in iron homeostasis. The results show that DFO and Lipro reversed the increase in cell death, downregulation of mTOR/PPAR-α, and decrease in ROS accumulation. In conclusion, chrysophanol inhibits the growth of oral squamous cell carcinoma cells by modulating mTOR/PPAR-α and by causing ROS accumulation.

Prognostic potential of Akt, pAkt(Ser473) and pAkt(Thr308) immunoreactivity in relation to HPV prevalence in head and neck squamous cell carcinoma patients

BACKGROUND

The prognosis of squamous cell carcinoma of head and neck (HNSCC) patients remains relatively poor over the last years. Tobacco, alcohol and active human papillomavirus (HPV) infection are involved in HNSCC development. Akt is a serine-threonine protein kinase with main phosphorylation sites at Thr308 and Ser473, which are critical to generate a high level of Akt activity.

MATERIALS AND METHODS

The aim of the study was to compare the expression and prognostic potential of total Akt and its 2 phosphorylated forms - pAkt(Ser473) and pAkt(Thr308) in relation to HPV status in HNSCC patients. The expression levels of proteins were assessed immunohistochemically. To select independent prognostic factors univariate and multivariate analyses with Cox proportional regression model were performed.

RESULTS

Among HNSCC with active HPV16 infection significantly more tumors with high Akt (67.86%, p = 0.026) and low pAkt(Ser473) (64.29%, p = 0.000) expressions were found as compared to those with HPV negativity, while there was no significant difference in the pAkt(Thr308) expression level between HPV positive and negative tumors (p = 0.359). In the whole group of HNSCC patients independent favorable prognostic factors were low T stage, low pAkt(Thr308) expression, HPV16 active infection presence (for OS and DFS) and female gender (for OS only).

CONCLUSIONS

Our results indicate an important role of pAkt(Thr308) as prognostic biomarker for HNSCC patients. There is a high probability that using Akt inhibitors would improve therapeutical benefits and treatment effectiveness, especially in HNSCC patients with high expression of pAkt.

Overview of oral cavity squamous cell carcinoma: Risk factors, mechanisms, and diagnostics

Oral cavity squamous cell carcinoma (OCSCC) is the most common malignancy of the oral cavity. The substantial risk factors for OCSCC are the consumption of tobacco products, alcohol, betel quid, areca nut, and genetic alteration. However, technological advancements have occurred in treatment, but the survival decreases with late diagnosis; therefore, new methods are continuously being investigated for treatment. In addition, the rate of secondary tumor formation is 3-7% yearly, which is incomparable to other malignancies and can lead to the disease reoccurrence. Oral cavity cancer (OCC) arises from genetic alterations, and a complete understanding of the molecular mechanism involved in OCC is essential to develop targeted treatments. This review aims to update the researcher on oral cavity cancer, risk factors, genetic alterations, molecular mechanism, classification, diagnostic approaches, and treatment.

Oncogenic role of MiR-130a in oral squamous cell carcinoma

Aberrant activation of the PI3K/AKT/mTOR pathway is attributed to the pathogenesis of oral squamous cell carcinoma (OSCC). In recent years, increasing evidence suggests the involvement of microRNAs (miRNAs) in oral carcinogenesis by acting as tumor suppressors or oncogenes. TSC1, as a component of the above pathway, regulates several cellular functions such as cell proliferation, apoptosis, migration and invasion. Downregulation of TSC1 is reported in oral as well as several other cancers and is associated with an unfavourable clinical outcome in patients. Here we show that oncogenic miR-130a binds to the 3′UTR of TSC1 and represses its expression. MiR-130a-mediated repression of TSC1 increases cell proliferation, anchorage independent growth and invasion of OSCC cells, which is dependent on the presence of the 3′UTR in TSC1. We observe an inverse correlation between the expression levels of miR-130a and TSC1 in OSCC samples, suggesting that their interaction is physiologically relevant. Delivery of antagomiR-130a to OSCC cells results in a significant decrease in xenograft size. Taken together, the findings of the study indicate that miR-130a-mediated TSC1 downregulation is not only a novel mechanism in OSCC, but also the restoration of TSC1 levels by antagomiR-130a may be a potential therapeutic strategy for the treatment of OSCC.

Autophagy-A Hidden but Important Actor on Oral Cancer Scene

The duration of denture use, oral hygiene, smoking and male sex were identified as risk factors for oral mucosal lesions. As it is well known, all the oral mucosal lesions associated with risk factors have an important degree of malignity. Chronic mechanical irritation can be another cause of oral cancer and it is produced by the constant action of a deleterious agent from the oral cavity. Autophagy represents a complex evolutionary conserved catabolic process in which cells self-digest intracellular organelles in order to regulate their normal turnover and remove the damaged ones with compromised function to further maintain homeostasis. Autophagy is modulated by mTOR kinase and indirectly by PI3K/AKT survival pathway. Due to its dual capacity to either induce cell death or promote cell survival, important evidence pointed that autophagy has a two-faced role in response to chemotherapy in cancer. In conclusion, understanding how to overcome cytoprotective autophagy and how to take advantage of autophagic cell death is critical in order to enhance the cancer cells sensitivity to particular therapeutic agents.

Targeting AKT/mTOR in Oral Cancer: Mechanisms and Advances in Clinical Trials

Oral cancer (OC) is a devastating disease that takes the lives of lots of people globally every year. The current spectrum of treatment modalities does not meet the needs of the patients. The disease heterogeneity demands personalized medicine or targeted therapies. Therefore, there is an urgent need to identify potential targets for the treatment of OC. Abundant evidence has suggested that the components of the protein kinase B (AKT)/ mammalian target of rapamycin (mTOR) pathway are intrinsic factors for carcinogenesis. The AKT protein is central to the proliferation and survival of normal and cancer cells, and its downstream protein, mTOR, also plays an indispensable role in the cellular processes. The wide involvement of the AKT/mTOR pathway has been noted in oral squamous cell carcinoma (OSCC). This axis significantly regulates the various hallmarks of cancer, like proliferation, survival, angiogenesis, invasion, metastasis, autophagy, and epithelial-to-mesenchymal transition (EMT). Activated AKT/mTOR signaling is also associated with circadian signaling, chemoresistance and radio-resistance in OC cells. Several miRNAs, circRNAs and lncRNAs also modulate this pathway. The association of this axis with the process of tumorigenesis has culminated in the identification of its specific inhibitors for the prevention and treatment of OC. In this review, we discussed the significance of AKT/mTOR signaling in OC and its potential as a therapeutic target for the management of OC. This article also provided an update on several AKT/mTOR inhibitors that emerged as promising candidates for therapeutic interventions against OC/head and neck cancer (HNC) in clinical studies.

Nimbolide, a neem limonoid inhibits cytoprotective autophagy to activate apoptosis via modulation of the PI3K/Akt/GSK-3β signalling pathway in oral cancer

Of late, nimbolide, a limonoid from the neem tree (Azadirachta indica) has gained increasing research attention owing to its potent antiproliferative and apoptosis-inducing effects. The present study was designed to investigate the effect of nimbolide on autophagy and the time point at which the phosphorylation status of GSK-3β and PI3K dictate the choice between autophagy and apoptosis in SCC131 and SCC4 oral cancer cells. Additionally, we analysed changes in the expression of proteins involved in autophagy and apoptosis after therapeutic intervention with nimbolide in a hamster model of oral oncogenesis. Furthermore, we also demonstrate changes in the expression of key genes involved in apoptosis and autophagy during the stepwise evolution of hamster and human OSCCs. Nimbolide-induced stereotypical changes in oral cancer cells characteristic of both apoptosis and autophagy. Time-course experiments revealed that nimbolide induces autophagy as an early event and then switches over to apoptosis. Nimbolide negatively regulates PI3K/Akt signalling with consequent increase in p-GSK-3βTyr216, the active form of GSK-3β that inhibits autophagy. Downregulation of HOTAIR, a competing endogenous RNA that sponges miR-126 may be a major contributor to the inactivation of PI3K/Akt/GSK3 signalling by nimbolide. Analysis of key markers of apoptosis and autophagy as well as p-AktSer473 during sequential progression of hamster and human OSCC revealed a gradual evolution to a pro-autophagic and antiapoptotic phenotype that could confer a survival advantage to tumors. In summary, the results of the present study provide insights into the molecular mechanisms by which nimbolide augments apoptosis by overcoming the shielding effects of cytoprotective autophagy through modulation of the phosphorylation status of Akt and GSK-3β as well as the ncRNAs miR-126 and HOTAIR. Development of phytochemicals such as nimbolide that target the complex interaction between proteins and ncRNAs that regulate the autophagy/apoptosis flux is of paramount importance in cancer prevention and therapeutics.