Proliferative and apoptotic responses in cancers with special reference to oral cancer

Identification of autophagy-related biomarker and analysis of immune infiltrates in oral carcinoma

Background

Autophagy plays a vital role in the progression of the tumor. We aimed to investigate the expression, prognostic value, and immune infiltration of autophagy‐related genes in oral carcinoma via bioinformatics analysis.

Methods

The microarray datasets (GSE146483 and GSE23558) of oral carcinoma were downloaded from Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) between normal and diseased groups were identified by the Limma package. The screened autophagy‐related gene was further validated by the human protein atlas (HPA) database, TCGA database, and GSE78060 dataset.

Results

A total of 18 upregulated (top 10: EGFR, TNF, FADD, AURKA, E2F1, CHEK1, BRCA1, BIRC5, EIF2AK2, and CSF2) and 31 downregulated (top 10: MAP1LC3A, PARK2, AGT, IGF1, TP53INP1, CXCL12, IKBKB, SESN1, ULK2, and RRAGD) autophagy‐related (DEGs) were identified, and FADD was found to be related to the prognosis of oral cancer patients. Gene set enrichment analysis indicated that FADD‐associated genes were significantly enriched in immune‐related pathways. Moreover, correlation analysis revealed that FADD expression was associated with immune infiltrates. Upregulation of FADD is associated with poor survival and immune infiltrates in oral cancer.

Conclusion

We speculated that FADD is involved in the immune regulation of oral cancer, as well as autophagy.

The oxidant/antioxidant status and cell death mode in oral squamous cell carcinoma

OBJECTIVE

Oxidative stress and imbalance in the oxidant/antioxidant system have a critical role in carcinogenesis by affecting necrosis and apoptosis. The aim of this study is to evaluate the oxidant/antioxidant status and cell death modes in patients with oral squamous cell carcinoma (OSCC).

MATERIALS AND METHODS

Twenty-nine patients with OSCC and 29 control subjects were included in the study. The levels of malondialdehyde (MDA), advanced oxidation protein products (AOPP) and ferric reducing antioxidant power (FRAP) were determined in plasma samples of all subjects. The necrotic and apoptotic cell death modes were evaluated with M65 ELISA and M30 ELISA, respectively.

RESULTS

MDA and AOPP values as oxidative stress markers were higher in patients with OSCC than in the control group. FRAP values evaluating plasma antioxidant status increased in OSCC patients. M65 and M30 levels indicating necrosis and apoptosis were significantly higher in OSCC patients compared to controls. There were significant correlations between MDA, AOPP and FRAP; M65 and M30 values.

CONCLUSIONS

The elevated levels of oxidative stress markers together with the increase of antioxidant capacity and the presence of a strong correlation between MDA, AOPP and FRAP suggest an activation of antioxidant defense against accentuated oxidative stress determined in OSCC. Enhanced oxidation of lipids and proteins may cause decomposition of cell membranes with subsequent leakage of cytoskeletal cytokeratins as CK18 and caspase-cleaved CK18 (evaluated as M65 and M30, respectively) in the circulation, suggesting that both cell death modes are affected in OSCC.

The hamster model of sequential oral oncogenesis

Oral squamous cell carcinoma (OSCC) is a common cancer characterised by low survival rate and poor prognosis. The multistep process of oral carcinogenesis is affected by multiple genetic events such as alterations of oncogenes and tumour suppressor genes. The use of appropriate experimental animal models that accurately represent the cellular and molecular changes which are associated with the initiation and progression of human oral cancer is of crucial importance. The Syrian golden hamster cheek pouch oral carcinogenesis model is the best known animal system that closely correlates events involved in the development of premalignant and malignant human oral cancers. Therefore, we established an experimental system of chemically induced oral carcinogenesis in hamsters, in order to study different stages of tumour formation: normal mucosa, hyperkeratosis, hyperplasia, dysplasia, early invasion, well differentiated OSCC and moderately differentiated OSCC. We investigated the expression of oncogenes EGFR, erbB2, erbB3, FGFR-2, FGFR-3, c-myc, N-ras, ets-1, H-ras, c-fos and c-jun, apoptosis markers Bax and Bcl-2, tumour suppressor genes p53 and p16, and cell proliferation marker Ki-67 in the sequential stages of hamster oral oncogenesis. Here, we describe the findings of the experimental model in regard to the involvement of signal transduction pathways in every stage of cancer development. Increased apoptosis and cell proliferation were observed in early stages of oral oncogenesis. Furthermore, the increased expression of transmembrane receptors (EGFR, erbB2, FGFR-2 and FGFR-3) as well as the increased expression of nuclear transcriptional factors in early stages of oral cancer indicates that these molecules may be used as early prognostic factors for the progression of OSCC. Since the expression of both H-ras and N-ras do not seem to affect signal transduction during oral oncogenesis, it can be assumed that a different signalling pathway, such as the PI3K and/or PLCgamma pathway, may be implicated in the pathogenesis of OSCC.

Cell cycle dysregulation in oral cancer

The dysregulation of the molecular events governing cell cycle control is emerging as a central theme of oral carcinogenesis. Regulatory pathways responding to extracellular signaling or intracellular stress and DNA damage converge on the cell cycle apparatus. Abrogation of mitogenic and anti-mitogenic response regulatory proteins, such as the retinoblastoma tumor suppressor protein (pRB), cyclin D1, cyclin-dependent kinase (CDK) 6, and CDK inhibitors (p21(WAF1/CIP1), p27(KIP1), and p16(INK4a)), occur frequently in human oral cancers. Cellular responses to metabolic stress or genomic damage through p53 and related pathways that block cell cycle progression are also altered during oral carcinogenesis. In addition, new pathways and cell cycle regulatory proteins, such as p12(DOC-1), are being discovered. The multistep process of oral carcinogenesis likely involves functional alteration of cell cycle regulatory members combined with escape from cellular senescence and apoptotic signaling pathways. Detailing the molecular alterations and understanding the functional consequences of the dysregulation of the cell cycle apparatus in the malignant oral keratinocyte will uncover novel diagnostic and therapeutic approaches.

Analysis of apoptosis-associated genes and pathways in oral cancer cells

BACKGROUND

Cancer cells can resist apoptosis that is induced by stimuli such as detachment or differentiation, but may be more susceptible to apoptosis when exposed to chemotherapeutic drugs. The pattern of gene expression that produces this phenotype is unknown.

METHODS

We compared gene expression patterns of normal human epidermal keratinocytes (NHEK cells) and the oral cancer cell line Tu183 when the cells were exposed to different apoptosis-inducing stimuli.

RESULTS

Pathway analysis revealed that the phenotype difference could be best explained by the simultaneous existence of both proapoptosis and antiapoptosis signals in the cancer cells. Microarray analysis, supported by immunoblotting, showed that one gene that was likely to be involved in the proapoptosis signal was TNFRSF5, which encodes the receptor CD40. When Tu183 cells were exposed to the CD40 ligand they showed apoptosis, while NHEK cells did not.

CONCLUSIONS

The effects of different apoptotic stimuli on normal cells and oral cancer cells can be explained by expression of proapoptosis genes, including the gene that encodes CD40.

Apoptosis in normal and diseased oral tissues

Apoptotic cell death plays an important role in maintenance of the normal physiological state and in the pathogenesis of diseases in the body. Over the last three decades the molecular mechanisms of apoptosis have been unravelled leading to development of novel therapeutic approaches. This paper aims to present current knowledge of the role of apoptosis in normal oral tissues and in the development of oral diseases.

Apoptosis in primary oral squamous cell carcinomas without lymph node metastases

The apoptosis in primary oral squamous cell carcinomas (OSCCs) without lymph node (IN) metastases and its relation with clinical stages and pathological grades was investigated. The terminal deoxynucleotidyl trasferase (TdT)-mediated dUTP nick end labeling (TUNEL) was used to detect the apoptotic cells in 15 cases of OSCCs. The percentage of apoptotic cells among tumor cells were calculated as apoptotic index (AI). The results showed that in all 15 cases of OSCCs, apoptotic cells could be visualized by TUNEL with AI ranging from 0.03 to 0.92 (average 0.32). AI was significantly negatively correlated with pathological grades (P < 0.05). It was concluded that the apoptotic rate was related to the malignant degree of OSCCs without LN metastases.

The role of apoptosis in oral disease: mechanisms; aberrations in neoplastic, autoimmune, infectious, hematologic, and developmental diseases; and therapeutic opportunities

Apoptosis is a genetically programmed form of cell death, which primarily functions to eliminate senescent or altered cells that are useless or harmful for the multicellular organism. Contrary to necrosis, apoptosis represents a physiologic cellular mechanism, normal function and control of which are critical for the development and homeostasis of multicellular organisms. In contrast, aberrations of the apoptotic mechanisms that cause excessive or deficient programmed cell death have been linked to a wide array of pathologic conditions. This review briefly summarizes the major apoptotic pathways and molecules and presents the most important oral diseases that are related to dysregulation of apoptosis. Knowledge of the association between aberrations in apoptotic mechanisms and human pathology hopefully will be implemented for the design of improved diagnostic and prognostic assays and the development of novel, more efficient, therapeutic strategies.

Cell death regulation in oral squamous cell carcinoma: methodological considerations and clinical significance

In the last three decades, more work has been done on apoptosis and its role in the pathogenesis of many diseases including cancer. In almost all instances of cancer, dysregulation of cell death (apoptosis) and cell proliferation have been found to play a major role in tumourigenesis. A lot of progress has been made on understanding the molecular basis of apoptosis and its regulatory mechanisms. This review focuses on current knowledge on the regulation of apoptosis in oral squamous cell carcinoma, current methodologies and methodological consideration in estimation of cell death in tissue sections and the clinical significance of apoptosis related molecules in progression of oral squamous cell carcinoma.

Mucosal tissue injury in cancer therapy. More than muscositis and mouthwash

PURPOSE

The purpose of this article is as follows: 1) to describe the characteristics and scope of mucosal tissue injury associated with cancer treatment; 2) to discuss recent advances in related basic and clinical science; and 3) to articulate research needs and opportunities to be addressed through collaborative interdisciplinary research.

OVERVIEW

Mucosal tissue injury is both a direct and indirect consequence of cancer therapy, with manifestations that include damage and a number of other potentially serious sequelae. Current research in mucosal tissue injury is focused on the biology, immunology, and genetics of mucosal injury; clinical problems; assessment and management; and processes and outcomes of care.

CLINICAL IMPLICATIONS

Results from these various areas of research enhance the understanding of the mechanisms of mucosal tissue injury, provide direction for the development of policy and for clinical practice, and help to define research needs and opportunities. Future research on the complex process of mucosal tissue injury will be interdisciplinary and will cross the boundaries among basic, translational, and clinical science.

Biology of oral mucosa and esophagus

The mucosal lining of the oral cavity and esophagus functions to protect the underlying tissue from mechanical damage and from the entry of microorganisms and toxic materials that may be present in the oropharynx. In different regions, the mucosa shows adaptation to differing mechanical demands: Masticatory mucosa consists of a stratified squamous keratinized epithelium tightly attached to the underlying tissues by a collagenous connective tissue, whereas lining mucosa comprises a nonkeratinized epithelium supported by a more elastic and flexible connective tissue. The epithelium is constantly replaced by cell division in the deeper layers, and turnover is faster in the lining than in the masticatory regions. Chemotherapeutic agents and radiation limit proliferation of the epithelium so that it becomes thin or ulcerated; this will first occur in the lining regions. The principal patterns of epithelial differentiation are represented by keratinization and nonkeratinization. As keratinocytes enter into differentiation, they become larger and begin to flatten and to accumulate cytokeratin filaments. In addition to the keratins, the differentiating keratinocytes synthesize and retain a number of specific proteins, including profilaggrin, involucrin, and other precursors of the thickening of the cell envelope in the most superficial layers. The concept of epithelial homeostasis implies that cell production in the deeper layers will be balanced by loss of cells from the surface. There is a rapid clearance of surface cells, which acts as a protective mechanism by limiting colonization and invasion of microorganisms adherent to the mucosal surface.

H-7 and fetal calf serum (FCS) act synergistically to increase apoptosis in the KB line of human oral carcinoma cells

There is a high incidence of oral squamous cell carcinoma (SCC) worldwide. The survival rate is among the lowest of the major cancers and has not improved significantly over the past two decades. The KB line of human oral carcinoma cells is a useful experimental system for studies of the biology of oral SCC. In a previous study, we reported inhibition of KB cell proliferation and stimulation of desmosome formation in confluent cultures treated with 20 microM H-7 (1-(5-isoquinolinylsulfonyl)-2-methylpiperazine). In the present study, the effects of this protein kinase C (PKC) inhibitor on the survival of KB cells were investigated. Apoptotic cells were detected using a combination of Hoechst 33258 nuclear stain, TUNEL technique and ultrastructural analysis. Our results indicated that H-7 significantly increased apoptosis in KB cells in a dose-dependent manner. Maximal stimulation occurred at 100 microM, the highest dose of H-7 tested. Apoptotic cells exhibited nuclear fragmentation, chromatin condensation and apoptotic bodies. Interestingly, H-7 and fetal calf serum (FCS) acted synergistically to increase apoptosis in KB cells, suggesting that there is a serum activated subpopulation of H-7 target cells in the cultures. The underlying mechanism of activation remains to be elucidated. Our study suggests that the PKC inhibitor H-7 is a potentially useful cytostatic agent for oral carcinoma cells.

doc-1--mediated apoptosis in malignant hamster oral keratinocytes

PURPOSE

Cell cycle mediators involved in inducing apoptosis are frequently deregulated during carcinogenesis. Deleted in oral cancer-1 (doc-1) is an S-phase regulator that is inactivated during oral carcinogenesis. Transfection of doc-1 into malignant oral keratinocytes leads to increased cell loss. It is hypothesized that ectopic expression of doc-1 in hamster oral cancer cells induces apoptosis.

MATERIALS AND METHODS

Malignant hamster oral keratinocytes (wt-HCPC-1), which lack measurable doc-1 mRNA and protein, were previously transfected with either a CMV-doc-1 expression vector construct (doc-HCPC-1) or the parental control vector pcDNA3 (cv-HCPC-1). A trypan blue exclusion assay was performed to examine cell death in the parental or wild-type HCPC-1 keratinocytes, HCPC-1 transfected with the parental pcDNA3 vector, and the doc-1 transfected HCPC-1 cells. To examine whether ectopic expression of doc-1 mediates gross cellular changes consistent with apoptosis, toluidine blue-safranin differential staining and the quantitative fluorescent microscopy assays were performed. To identify early apoptotic cytochemical changes observed in the cell membrane and nucleus, annexin V/propidium iodide (PI) fluorescence-activated cell sorter (FACS) analysis and the terminal deoxytransferase-mediated dUTP nick-end labeling (TUNEL) assay were performed.

RESULTS

Doc-HCPC-1 showed elevated numbers of dead cells over wt-HCPC-1 and cv-HCPC-1 in the trypan blue exclusion assay. Toluidine blue-safranin staining and quantitative fluorescent microscopy showed significant morphologic changes in the doc-1 transfectants consistent with apoptosis (P < .05). TUNEL assays (P < .05) and annexin V/PI FACS analysis (P < .05) also showed early cytochemical changes in the doc-HCPC-1 transfectants, confirming that ectopic expression of doc-1 induces apoptosis.

CONCLUSIONS

These data suggest that doc-1 induces apoptosis in malignant hamster oral keratinocytes. It is hypothesized that doc-1 is a mediator of apoptosis that is inactivated during hamster oral carcinogenesis.