Oral squamous cell carcinoma: electron microscopic and immunohistochemical characteristics

Altered iron metabolism as a target for ferroptosis induction in head and neck cancer

Iron is a mineral micronutrient essential for survival and vital functions in many biological processes in living organisms. Iron plays a crucial role as a cofactor of iron-sulfur clusters in energy metabolism and biosynthesis by binding with enzymes and transferring electrons to targets. Iron can also impair cellular functions by damaging organelles and nucleic acids by producing free radicals from redox cycling. Iron-catalyzed reaction products can induce active-site mutations in tumorigenesis and cancer progression. However, the boosted pro-oxidant iron form may contribute to cytotoxicity by increasing soluble radicals and highly reactive oxygen species via the Fenton reaction. An increased redox-active labile iron pool is required for tumor growth and metastasis, but the increased cytotoxic lipid radicals also lead to regulated cell death, such as ferroptosis. Therefore, this may be a major target for selectively killing cancer cells. This review intends to understand altered iron metabolism in cancers and discuss iron-related molecular regulators highly associated with iron-induced cytotoxic radical production and ferroptosis induction, focusing on head and neck cancer.

Paradoxical Roles of Desmosomal Components in Head and Neck Cancer

Desmosomes are intercellular adhesion complexes involved in various aspects of epithelial pathophysiology, including tissue homeostasis, morphogenesis, and disease development. Recent studies have reported that the abnormal expression of various desmosomal components correlates with tumor progression and poor survival. In addition, desmosomes have been shown to act as a signaling platform to regulate the proliferation, invasion, migration, morphogenesis, and apoptosis of cancer cells. The occurrence and progression of head and neck cancer (HNC) is accompanied by abnormal expression of desmosomal components and loss of desmosome structure. However, the role of desmosomal components in the progression of HNC remains controversial. This review aims to provide an overview of recent developments showing the paradoxical roles of desmosomal components in tumor suppression and promotion. It offers valuable insights for HNC diagnosis and therapeutics development.

Cellular localization of Visudyne as a function of time after local injection in an in vivo model of squamous cell carcinoma: an investigation into tumor cell death

OBJECTIVE

To evaluate the effects of time on cellular localization of Visudyne after local injection.

ANIMALS

Twenty athymic nude mice.

PROCEDURES

A squamous cell carcinoma (SCC) cell line (A-431) was injected into right and left dorsolumbar subcutaneous tissue of each mouse, representing treatment (T) and control (C) tumors. In experiment 1 (Exp 1; n = 10) and 2 (Exp 2; n = 10), the T tumors received a local injection of Visudyne (0.1 mg/cm(3)), and C tumors received an equal dose of 5% dextrose in water (D5W). Mice were randomly subdivided into two groups (A and B; n = 5 per group). Mice in Exp 1A and B were sacrificed 1 and 30 min after local injection, respectively. Experiment 1A and B tumors were evaluated by fluorescence microscopy to determine drug localization. Experiment 2A and B tumors were exposed to LED illumination 1 and 30 min after injection, respectively, and evaluated by transmission electron microscopy (TEM) to determine ultrastructural tumor cell damage.

RESULTS

Fluorescence was detected within the cytoplasm of T tumors in both Exp 1A and B. Significance was detected in fluorescence intensity between T1 min vs. T30 min (P = 0.03) and between T1 min and C1 min tumors (P = 0.01), respectively. Tumors in Exp 2A and B demonstrated evidence of apoptotic cell death.

CONCLUSIONS

Fluorescence microscopy demonstrated higher Visudyne concentration within SCC cytoplasm of 1 min compared with 30-min tumors. Transmission electron microscopy results revealed that tumors treated by photodynamic therapy (PDT) within 30 min of local injection undergo cellular apoptosis.

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.

Ultravlolet-B induced expression of hypoxia-inducible factor 1α, transferrin receptor through EGFR/PI3K/AKT/DEC1 pathway

The aim of this research was to explore the effects and signaling pathway of ultraviolet-B (UVB) irradiation on the expression of hypoxia-inducible factor 1α (HIF-1α) and transferrin receptor (TfR). HIF-1α protein was measured by Western blot method. Expressions of epidermal growth factor receptor (EGFR), phosphor-EGF-R and TfR after UVB irradiation were determined with flow cytometry. After UVB irradiation, mRNA levels of HIF-1α and TfR were detected by real time-PCR. Results showed that compared with control groups, UVB was able to induce HIF1α and TfR protein expression in a dose-and time-dependent manner in HaCat cells (P < 0.05). TfR mRNA was expressed in a dose-dependent manner and reached a peak at the 8th hour in HaCat cells (P < 0.05) whereas HIF-1α mRNA expression was not affected by UVB treatment (P>0.05). The EGFR/PI3K/AKT signaling pathway was required for the induction of HIF-1α and TfR expression induced by UVB. UVB induced activation of EGFR in HaCat cells and EGFR regulated expression of TfR and HIF-1α. EGFR (-/-) MEF did not increase the HIF1 expression following UVB irradiation (P>0.05). In contrast, EGFR (+/+) MEF strongly enhanced HIF1α expression after UVB irradiation (P < 0.05). PD153035, a selective inhibitor of EGFR tyrosine kinase, inhibited the TfR protein expression in UVB-treated cells in a dose-dependent manner (P < 0.05). PI3K inhibitors, LY294002 and wortmannin, inhibited HIF-1α and TfR expressions induced by UVB (P < 0.05). The DEC1 (-/-) HaCat cells did not increase their TfR and HIF-1α expressions following UVB irradiation (P>0.05). In contrast, DEC1 (+/+) HaCat cells strongly enhanced TfR and HIF-1α protein expression after UVB irradiation (P < 0.05). We conclude that UVB induces TfR and HIF-1α expressions via EGFR/PI3K/AKT/DEC1 signaling pathway.

Possible etiology of calculi formation in salivary glands: biophysical analysis of calculus

Sialolithiasis is one of the common diseases of the salivary glands. It was speculated that, in the process of calculi formation, degenerative substances are emitted by saliva and calcification then occurs around these substances, and finally calculi are formed. However, the exact mechanism of the formation of calculi is still unclear. In this study, we identify some possible etiologies of calculi formation in salivary glands through biophysical analysis. Calculi from 13 patients with submandibular sialolithiasis were investigated by transmission electron microscopy, scanning electron microscopy, X-ray microanalyzer, and electron diffraction. Transmission electron microscopic observation of calculi was performed in the submandibular gland (n = 13). In 3 of the 13 cases, a number of mitochondria-like structures and lysosomes were found near calcified materials. Scanning electron microscopic examination of these materials revealed that there were lamellar and concentric structures and that the degree of calcification was different among the calculi. X-ray microanalysis disclosed the component elements in the calculi to be Ca, P, S, Na, etc., and the main constituents were Ca and P. The calcium-to-phosphorus ratio was 1.60-1.89. Analysis of the area including mitochondria-like structures, lysosomes, and the fibrous structures by electron diffraction revealed the presence of hydroxyapatite and calcified materials. It is speculated that mitochondria and lysosomal bodies from the ductal system of the submandibular gland are an etiological source for calcification in the salivary gland.

Expression of cell cycle-regulated proteins pRB2/p130, p107, E2F4, p27, and pCNA in salivary gland tumors: prognostic and diagnostic implications

The retinoblastoma family consists of the tumor suppressor nuclear phosphoprotein pRb/p105 and related proteins p107 and pRb2/p130. Recent immunohistochemical studies of the retinoblastoma family of proteins in lung and endometrial cancer and choroidal melanomas show a tight inverse correlation between the histologic grading in the most aggressive tumor types and pRb2/p130 expression. This led us to investigate the role of pRb2/p130 in salivary tumors. We studied the expression of pRb2/p130, p107, E2F4, p27, and PcNA by immunohistochemistry in a panel of 44 salivary gland tumors. We found a direct correlation between the cytoplasmic expression of pRb2/p130 and tumor grading and the presence of metastasis that was highly statistically significant (P < 0.001). Additionally, increased cytoplasmic pRb2/p130 expression was significantly correlated with a decreased probability of survival (P < 0.001). Interestingly, p107 nuclear expression showed a strong direct correlation when compared with the same variables. pRb2/p130 showed the highest percentage of undetectable nuclear levels in the specimens examined and the tightest inverse correlation (P < 0.0001) with both the histologic grading and pCNA expression in malignant salivary tumors. Additionally, E2F4 showed an identical localization pattern as to that of pRb2/p130. These data suggests an important role for pRb2/p130 in the pathogenesis and progression of certain salivary gland cancers.

Copy number changes of target genes in chromosome 3q25.3-qter of esophageal squamous cell carcinoma: TP63 is amplified in early carcinogenesis but down-regulated as disease progressed

AIM: By using comparative genomic hybridization, gain of 3q was found in 45-86% cases of esophageal squamous cell carcinoma (EC-SCC). Chromosome 3q25.3-qter is the minimal common region with several oncogenes found within this region. However, amplification patterns of these genes in EC-SCC have never been reported. The possible association of copy number changes of these genes with pathologic characteristics is still not clear.

METHODS: Real-time quantitative PCR (Q-PCR) was performed to analyze the copy number changes of 13 candidate genes within this region in 60 primary tumors of EC-SCC, and possible association of copy number changes with pathologic characteristics was analyzed by statistics. Immunohistochemistry (IHC) study was also performed on another set of 111 primary tumors of EC-SCC to verify the association between TP63 expression change and lymph node metastasis status.

RESULTS: The average copy numbers (±SE) per haploid genome of individual genes in 60 samples were (from centromere to telomere): SSR3: 4.19 (±0.69); CCNL1: 5.24 (±0.67); SMC4L1: 2.01 (±0.16); EVI1: 2.02 (±0.12); hTERC: 5.28 (±0.54); SKIL: 2.71 (±0.14); EIF5A2: 1.95 (±0.12); ECT2: 9.18 (±1.68); PIK3CA: 8.13 (±1.17); EIF4G1: 1.07 (±0.05); SST: 3.07 (±0.25); TP63: 2.51 (±0.22); TFRC: 2.42 (±0.19). Four clusters of amplification were found: SSR3 and CCLN1 at 3q25.31; hTERC and SKIL at 3q26.2; ECT2 and PIK3CA at 3q26.31-q26.32; and SST, TP63 and TFRC at 3q27.3-q29. Patients with lymph node metastasis had significantly lower copy number of TP63 in the primary tumor than those without lymph node metastasis. IHC study on tissue arrays also showed that patients with lymph node metastasis have significantly lower TP63 staining score in the primary tumor than those without lymph node metastasis.

CONCLUSION: This study showed that different amplification patterns were seen among different genes within 3q25.3-qter in EC-SCC, and several novel candidate oncogenes (SSR3, SMC4L1, ECT2, and SST) were identified. TP63 is amplified in early stage of EC-SCC carcinogenesis but down-regulated in advanced stage of disease.

Transferrin receptor is a marker of malignant phenotype in human pancreatic cancer and in neuroendocrine carcinoma of the pancreas

Transferrin receptor (TFRC) is a membrane-bound protein expressed in larger amounts in proliferating, e.g., malignant, cells than in quiescent cells. The specific expression of TFRC can represent a diagnostic tool or a therapeutic target in solid tumours expressing this antigen. Whether TFRC is expressed in human pancreatic tumours is unknown. The aim of this study was the investigation of the expression of TFRC and transferrin in human pancreatic cancer and in neuroendocrine tumours of the pancreas. Fifty one specimens of human pancreatic cancer and 14 samples of pancreatic neuroendocrine tumours were obtained after surgery. The expression of TFRC, transferrin and cytokeratin was studied by standard immunohistochemistry. Flow cytometry was used for the investigation of TFRC expression in nine cell lines of ductal pancreatic cancer in vitro. In contrast to normal tissue, 93% of pancreatic tumour cells showed positive (82%) or heterogeneous (11%) expression of TFRC. It was strongly expressed by malignant epithelial cells; normal stromal and endothelial cells were not stained by anti-TFRC antibodies. Primary tumours and metastases showed a similar frequency of TFRC expression. Three neuroendocrine carcinomas showed positive expression of TFRC by malignant tumour cells. The expression of TFRC was negative in benign neuroendocrine tumours of the pancreas. The cell lines of pancreatic cancer were characterised by a low expression of TFRC in vitro. In contrast to normal pancreatic tissue and benign neuroendocrine tumours of the pancreas, pancreatic cancer and neuroendocrine carcinoma are therefore characterised frequently by high expression of TFRC. Hence, TFRC represents a marker of malignant transformation in the pancreas that could be applied as potential diagnostic and therapeutic target.

Expression of E-cadherin, alpha-catenin, and beta-catenin in the process of lymph node metastasis in oral squamous cell carcinoma

Regional lymph node metastasis is a very important prognostic indicator. In the metastatic process, reduction in cell to cell adhesion including E-cadherin-catenin cell adhesion complex is an essential step. We investigated immunohistochemical expression of E-cadherin, alpha-catenin and beta-catenin in 159 tissue samples from patients with oral squamous cell carcinoma and examined the correlation between their expressions and the presence of regional lymph node metastasis. Significantly greater reduction in expression levels of E-cadherin, alpha-catenin and beta-catenin was found in the metastatic group (n=64) compared to the nonmetastatic group (n=95) (P=0.007, 0.001, 0.001, respectively). However, there was no significant correlation between their expressions and the features of the regional metastasis, the number of metastatic lymph nodes or the presence of extracapsular metastasis. These data suggest that evaluation of the immunohistochemical expression of E-cadherin, alpha-catenin and beta-catenin is extremely valuable for the diagnosis of metastatic occurrence.