Apoptosis in epithelial hyperplastic laryngeal lesions

Apoptosis and Vocal Fold Disease: Clinically Relevant Implications of Epithelial Cell Death

PURPOSE

Vocal fold diseases affecting the epithelium have a detrimental impact on vocal function. This review article provides an overview of apoptosis, the most commonly studied type of programmed cell death. Because apoptosis can damage epithelial cells, this article examines the implications of apoptosis on diseases affecting the vocal fold cover.

METHOD

A review of the extant literature was performed. We summarized the topics of epithelial tissue properties and apoptotic cell death, described what is currently understood about apoptosis in the vocal fold, and proposed several possible explanations for how the role of abnormal apoptosis during wound healing may be involved in vocal pathology.

RESULTS AND CONCLUSIONS

Apoptosis plays an important role in maintaining normal epithelial tissue function. The biological mechanisms responsible for vocal fold diseases of epithelial origin are only beginning to emerge. This article discusses speculations to explain the potential role of deficient versus excessive rates of apoptosis and how disorganized apoptosis may contribute to the development of common diseases of the vocal folds.

Evaluation of Dying Vocal Fold Epithelial Cells by Ultrastructural Features and TUNEL Method

Cell death is a regulated mechanism of eliminating cells to maintain tissue homeostasis. This study described 2 methodological procedures for evaluating cell death in the epithelium of immobilized, approximated and vibrated vocal folds from 12 New Zealand white breeder rabbits. The gold standard technique of transmission electron microscopy evaluated high-quality ultrastructural criteria of cell death and a common immunohistochemical marker, the terminal deoxynucleotidyl transferase dUTP nick end labeling method, to confirm cell death signaling. Results revealed that ultrastructural characteristics of apoptotic cell death, specifically condensed chromatin and apoptotic bodies, were observed after vocal fold vibration and approximation. Although episodes of necrosis were rare, few enlarged cell nuclei were present after vibration and approximation. The vocal fold expresses an immunohistochemical marker for apoptosis along the apical surface of the epithelium. This study provides a solid foundation for future investigations regarding the role of cell death in vocal fold health and disease.

Analysis of metallothionein and vimentin immunoreactivity in pharyngeal squamous cell carcinoma and its microenvironment

Metallothionein (MT) has been shown to have pro-proliferative anti-apoptotic activity and to be involved in microenvironment remodeling. The aim of this study has been to determine whether the changes in MT and vimentin immunoreactivity observed in cancer and its microenvironment are related to the local spread of the disease. The immunoreactivity levels of both MT and vimentin were evaluated together with CD56 and CD57 antigens in 49 tissue samples taken from patients with squamous cell carcinoma originating from the palatine tonsils and in 20 tissue samples derived from patients with chronic tonsillitis (the reference group). MT immunoreactivity levels were statistically significantly higher in the tissue samples from squamous cell carcinoma than in those of the reference group and also higher in the squamous cell carcinoma samples compared with the stromal samples. Moreover, stromal fibroblasts exhibited high vimentin and MT immunoreactivity levels. Statistically significantly higher MT immunoreactivity levels within the tumor cells were identified in patients with the presence of lymph node metastases in contrast to those patients without such metastases. Vimentin was detected in both the tumor and the stromal tissue samples and presented an interesting pattern of staining strongly expressed within the stroma and the septal architecture of the tumor. The number of CD56- and CD57-positive lymphocytes identified in tissue samples both from squamous cell carcinoma and from the stroma was statistically significantly lower than that in the reference group. MT expression by tumor cells is thus associated with an aggressive phenotype of the tumor and the ability to create metastases.

The Potential Role of MT and Vimentin Immunoreactivity in the Remodeling of the Microenvironment of Parotid Adenocarcinoma

A tumor stimulates the remodeling of its microenvironment in order to control and accelerate its own growth and to initiate metastases. To create metastases the tumor cells must first acquire the ability to detach from the main tumor and to adhere to, invade, and degrade the adjacent extracellular matrix. The cells must then be able to enter the lumen of the vessels where they home the distant tissues and organs by forming secondary tumors. The acquisition of this phenotype is related to the phenomenon of epithelial-to-mesenchymal transition. On the molecular level, this process is typified by a change in the expression of epithelial markers and by the enhancement of the expression of mesenchymal markers like vimentin that are responsible for cell migration and invasion. Metallothioneins have been shown to help protect against apoptosis. The expression of MT by tumor cells plays an important and complex role not only because of its pro-proliferative, anti-apoptotic activity, but also because it inhibits the immune response. The aim of the present study was to evaluate the immunoreactivity of vimentin and MT in the salivary gland adenocarcinoma and its stroma in order to observe the phenomenon of stromal remodeling. The tissue samples of salivary gland adenocarcinomas and their stromas and the palatine tonsils which constituted the reference group were obtained during routine surgical procedures. The immunoreactivity of vimentin, metalothionein, CD56, CD57 antigens was evaluated by the immunohistochemistry method in 30 tissue samples of parotid adenocarcinoma. The patient's consent was obtained in each case. A statistically significantly higher level of MT immunoreactivity was observed in the adenocarcinoma tissue slides than in either the stromal slides or the reference slides while no differences in MT immunoreactivity were detected when the stroma and reference tissue slides were compared. A statistically significantly higher vimentin immunoreactivity level was identified in the tumor microenvironment tissue slides than in the tumor tissue slides, and a statistically significantly higher level of vimentin immunoreactivity was identified in the tumor microenvironment slides than in the slides of the reference tissue, while no differences were identified between the adenocarcinoma tissue slides and the reference slides with respect to vimentin immunoreactivity. A statistically significantly higher number of CD56- and CD57-expressing cells were identified in the reference tissue slides than in either the adenocarcinoma or stromal slides. In conclusion, the stroma of salivary gland adenocarcinoma in this study has been characterized by remodeling. The remodeling is represented by the expression of both vimentin and MT and by a deficit of CD57- and CD58-expressing cell infiltration. This situation would seem to be the result of immune tolerance for the tumor developing within the tumor microenvironment. Furthermore, the presence of MT and vimentin immunoreactivity in the fibroblasts of the tumor stroma may constitute a marker of active tissue remodeling.

RCAS1, MT, and vimentin as potential markers of tumor microenvironment remodeling

A tumor stimulates the remodeling of its microenvironment for its own survival. To protect its own growth and induce angiogenesis, the tumor changes the structure of extracellular matrix and the function of existing cells; it thus chemo-attracts immune system cells altering their function. In our study, we discuss the potential markers of tumor microenvironment remodeling. For instance, RCAS1 is a protein responsible for tumor escape from host immunologic surveillance that additionally seems to be involved in the remodeling of the microenvironment. Another protein, metallothionein, which is both anti-apoptotic and pro-proliferative, is also responsible for modulating the response of immune system cells. Most likely, the expression of this protein by the fibroblasts of tumor microenvironment is related to the remodeled phenotype of these cells because of the tumor influence on cancer-associated fibroblasts. Lastly, vimentin is a protein that would appear to be the marker for the mesenchymal transition of cells from the epithelial phenotype. These cells seem to acquire the mesenchymal phenotype to migrate so that they can facilitate the development of metastases. Interestingly, the expression of vimentin has also been observed in the tumor microenvironment as well and may serve as a marker of a remodeled stroma in the process of facilitating tumor spread.

Ear asymmetries in middle-ear, cochlear, and brainstem responses in human infants

In 2004, Sininger and Cone-Wesson examined asymmetries in the signal-to-noise ratio (SNR) of otoacoustic emissions (OAE) in infants, reporting that distortion-product (DP)OAE SNR was larger in the left ear, whereas transient-evoked (TE)OAE SNR was larger in the right. They proposed that cochlear and brainstem asymmetries facilitate development of brain-hemispheric specialization for sound processing. Similarly, in 2006 Sininger and Cone-Wesson described ear asymmetries mainly favoring the right ear in infant auditory brainstem responses (ABRs). The present study analyzed 2640 infant responses to further explore these effects. Ear differences in OAE SNR, signal, and noise were evaluated separately and across frequencies (1.5, 2, 3, and 4 kHz), and ABR asymmetries were compared with cochlear asymmetries. Analyses of ear-canal reflectance and admittance showed that asymmetries in middle-ear functioning did not explain cochlear and brainstem asymmetries. Current results are consistent with earlier studies showing right-ear dominance for TEOAE and ABR. Noise levels were higher in the right ear for OAEs and ABRs, causing ear asymmetries in SNR to differ from those in signal level. No left-ear dominance for DPOAE signal was observed. These results do not support a theory that ear asymmetries in cochlear processing mimic hemispheric brain specialization for auditory processing.

Metallothionein expression in human neoplasia

The metallothionein family is a class of low-molecular-weight, cysteine-rich proteins with high affinity for metal ions. Four major isoforms (metallothionein-1, -2, -3, and -4) have been identified in mammals, involved in many pathophysiological processes, including metal ion homeostasis and detoxification, protection against oxidative damage, cell proliferation and apoptosis, drug and radiotherapy resistance and several aspects of the carcinogenic process. In the present review we examine the expression of metallothionein in different human tumours and its correlation with histopathological variables, tumour cell proliferation or apoptosis, resistance to radiation or chemotherapy, patient survival and prognosis. A variable profile of metallothionein and its isoforms' expression has been observed in different cancer types. Although metallothionein expression has been implicated in carcinogenic evolution, its use as a marker of tumour differentiation, cell proliferation and prognosis predictor remains unclear. Detailed studies focused on the expression of metallothionein isoforms and isotypes in different tumour types could elucidate the role of this group of proteins in the carcinogenic process, delineating its possible clinical significance for the management of patients.

Application of SEC-ICP-MS for comparative analyses of metal-containing species in cancerous and healthy human thyroid samples

Size exclusion chromatography (SEC) was coupled on-line to inductively coupled plasma mass spectrometry (ICP-MS) for speciation study of trace metals in cancerous thyroid tissues in comparison to healthy thyroids aimed to estimation of changes in metalloprotein speciation in pathological tissue. The study showed a presence of species binding Cu, Zn, Cd and Pb in healthy thyroid tissue with a good reproducibility of chromatographic results, whereas the same species could not be detected in cancerous tissues. Thus, remarkable differences with respect to metal-binding species were revealed between healthy and pathological thyroid samples, pointing out a completely different distribution of trace metals in cancerous tissues. The metal-binding species could not be identified in the frame of this work because of a lack of appropriate standards. Nevertheless, the results obtained confirm the suitability of SEC-ICP-MS for monitoring of changes in trace metal distribution in cancerous tissue and will help to better understand the role of metal-containing species in thyroid pathology.

Prognostic significance of apoptosis in laryngeal cancer. A quantitative immunomorphological study

The main purpose of the study was to investigate the prognostic significance of apoptosis of cancer cells and to examine the relationship between apoptosis and morphological markers of the host immune response in laryngeal cancer. Apoptotic tumour cells, detected by the TUNEL technique, expression of HLA DR (an antigen belonging to human leukocyte-associated antigens class II) in cancer cells, the number of tumour infiltrating T cells (CD45RO+ cells), B cells (CD20+ cells), macrophages (CD68+ cells) and mast cells as well as the mitotic index were investigated in 28 laryngeal cancers. Sections were studied morphometrically using image analysis. Significant inverse correlations between the number of apoptotic tumour cells and HLA DR-positive tumour cells as well as between the number of apoptotic tumour cells and the number of CD45RO+ cells at the tumour periphery were observed. Analysis of survival showed that patients with high rates of apoptosis had significantly worse prognosis as compared to patients with low apoptotic rates. Differences in HLA DR expression and numbers of CD45RO+ cells were also found between groups of patients with high and low numbers of apoptotic cells. Whether these findings are due to immunosuppressive effects of apoptosis needs further investigation.

Significance of Fas protein in squamous cell carcinoma of the larynx

The purpose was to elucidate the clinical significance of Fas protein in laryngeal squamous cell carcinoma (LSSC). Medical records of 30 patients who were operated for LSCC between 1991 and 1997 were reviewed, and histopathological and immunohistochemical studies of the archival tumor tissues were performed. Conventional histopathology included tumor grading, mitotic counting (MC) and status of the cervical lymph nodes. The monoclonal antibodies to Fas (DAKO M 3554) and nm23 (DAKO A0096 Lot 035) proteins were used for immunohistochemical staining. Streptavidin-Biotin, horseradish method was used. Positive staining for both Fas and nm23 was obtained in 27 (90%) tumor samples. There was no correlation between neck metastasis and Fas positivity (r = 0.126, p = 0.505 and chi2 = 0.062, p = 0.996, respectively). Fas positivity did not correlate to grade (r = 0.282, p = 0.130), tumor size or T (r = 0.0457, p = 0.810, chi2 = 0.0.018, p = 0.999) or laryngeal site of involvement (chi2 = 0.0937, p = 0.992). However, a correlation was found between Fas and MC (r = 0.482. p = 0.007). There was also a correlation between Fas and nm23 positivity (r = 0.614, p < 0.0001). Fas protein expression has no prognostic value in LSCC, because the Fas values do not correlate with grade, stage or nodal status of neck. However, 90% of LSCCs expressed Fas protein. Understanding the functional status of the Fas receptor proteins may lead to development of new therapeutic options for LSSC in the future.

Immunohistochemically stained markers (p53, PCNA, bcl-2) in dysplastic lesions of the larynx

The percentage of malignant transformation of laryngeal dysplastic lesions is difficult to estimate. There is a need for new histological markers which could enable more objective assessment of the premalignant stages of the larynx and help in estimation of the potential of future neoplastic progression. We performed a retrospective study to determine whether immunohistochemical staining for the proliferating cell nuclear antigen (PCNA), tumour suppressor gene protein p53 and antiapoptotic protein bcl-2 may be prognostic factors in laryngeal epithelial lesions. Staining was performed on 57 paraffin-embedded biopsies from patients with clinically detected precancerous stages of the larynx. Histopathologic examination revealed normal epithelium in six cases, mild dysplasia in 20 cases, moderate dysplasia in 18 cases, severe dysplasia in seven cases, CA in situ in four cases, papilloma in one case and CA invasivum in one case. The p53 count in mild and moderate dysplasia was 26.8 and 38.6%, respectively. This difference was statistically significant. There was significant correlation between PCNA and p53 scores. There was also a relationship between the scores of these markers and bcl-2 expression. In ten out of 45 cases of dysplastic lesions the invasive cancer developed in 4 years of follow-up. The correlation between PCNA score and malignant progression of the dysplastic lesions was on the statistical borderline. There was significant relationship between malignant transformation and age of the patients.

CNS wound healing is severely depressed in metallothionein I- and II-deficient mice

To characterize the physiological role of metallothioneins I and II (MT-I+II) in the brain, we have examined the chronological effects of a freeze injury to the cortex in normal and MT-I+II null mice. In normal mice, microglia/macrophage activation and astrocytosis were observed in the areas surrounding the lesion site, peaking at approximately 1 and 3 d postlesion (dpl), respectively. At 20 dpl, the parenchyma had regenerated. Both brain macrophages and astrocytes surrounding the lesion increased the MT-I+II immunoreactivity, peaking at approximately 3 dpl, and at 20 dpl it was similar to that of unlesioned mice. In situ hybridization analysis indicates that MT-I+II immunoreactivity reflects changes in the messenger levels. In MT-I+II null mice, microglia/macrophages infiltrated the lesion heavily, and at 20 dpl they were still present. Reactive astrocytosis was delayed and persisted at 20 dpl. In contrast to normal mice, at 20 dpl no wound healing had occurred. The rate of apoptosis, as determined by using terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling, was drastically increased in neurons of ipsilateral cortex of the MT-I+II null mice. Our results demonstrate that MT-I+II are essential for a normal wound repair in the CNS, and that their deficiency impairs neuronal survival.

Enhanced apoptosis correlates with poor survival in patients with laryngeal cancer but not with cell proliferation, bcl-2 or p53 expression

The purpose of the current study was to analyse apoptosis and bcl-2 expression in laryngeal squamous cell carcinoma (SCC) with special reference to their prognostic significance, correlation with the clinical and pathological characteristics as well as cell proliferation and p53 accumulation. 172 patients with primary laryngeal SCC were followed-up for a median of 67 months. The volume corrected apoptotic (A/V) index was analysed using an in situ end labelling method (TUNEL) in 85 randomly selected patients. The expression of bcl-2 and p53 was analysed with monoclonal antibodies. The proliferative activity was measured both with Ki-67 (MIB-1) antibody and the volume corrected mitotic (M/V) index. The A/V index was not associated with p53 (P = 0.6) or bcl-2 (P = 0.6) expression or with proliferative parameters (P = 0.9 for M/V and P = 0.3 for MIB-1). The 10-year overall survival in patients with a high A/V index was poorer when compared with patients with a low index (47% versus 81%, P = 0.005), while accumulation of bcl-2 had no prognostic significance (P = 0.5). In Cox multivariate analysis of the whole cohort, stage (P < 0.0005) and histological grade (P = 0.04) were predictors of overall survival. In the subset of patients with an A/V index available, predictors of survival were stage (P = 0.05), A/V index (P = 0.02) and histological grade (P = 0.04). A high A/V index was an independent predictor of poor survival in laryngeal SCC. This effect was not associated with tumour cell proliferation. Accumulations of p53 and bcl-2 were not associated with apoptosis. Expression of bcl-2 lacks any prognostic significance in laryngeal SCC. We propose that assessment of the A/V index may help in selecting patients with poor prognosis.