p53, PCNA and Ki-67 expression in oral squamous cell carcinomas: the vagaries of fixation and microwave enhancement of immunocytochemistry

Effects of different fixatives over different fixation times, including Antigenfix, on immunohistochemical studies

Tissue fixation is an essential step in the performance of ancillary studies, including immunohistochemistry. The aim of this study was to compare the effect of various fixatives and fixative times on immunohistochemistry (IHC) in bovine and porcine endometrium using progesterone receptors and SOX2 antibodies. Immunohistochemical staining with progesterone receptors and SOX2 was performed on tissue samples fixed in formalin, Antigenfix, Greenfix, Bouin’s solution and methacarn at 1.5, 8.5, 15.5, 29.5, 64.5, 189.5, 249.5, 309.5 and 369.5 days of fixation. Formalin and Antigenfix proved to be the best fixative for both short-term and long-term fixation for IHC. Bouin’s solution was partially applicable for short-term (24 h) fixation. Greenfix and methacarn were absolutely inappropriate fixatives for IHC (completely negative staining using methacarn). These results were obtained on an automated immunostainer using EDTA buffer pH 8.4 as the antigen retrieval solution. When the staining procedure was performed manually and citrate buffer with different pH values was used, weakly positive results were obtained with both progesterone receptors (pH 8 and 9) and SOX2 (pH 7.2); however, significantly lower staining quality was obtained using the methacarn fixative compared to aldehyde fixatives. The reported findings demonstrated the superiority of aldehyde fixatives (formalin and Antigenfix) over alcohol fixatives (methacarn) and fixatives combining both denaturing and cross-linking proteins (Greenfix and Bouin’s solution) for IHC. Antigen retrieval-IHC using EDTA buffer was found to be excellent for aldehyde fixatives, but proved to be completely unsuitable for methacarn, Greenfix, and Bouin’s solution.

Expression of Ki-67 in normal oral epithelium, leukoplakic oral epithelium and oral squamous cell carcinoma

Aims and Objective:

To demonstrate the presence, location and pattern of cell proliferation in different histological grades of oral epithelial dysplasia (OED), oral squamous cell carcinoma (OSCC) and normal oral epithelium (NOE) using an antibody directed against the Ki-67 antigen and its intensity of staining evaluated respectively.

Materials and Methods:

A total number of 100 archival paraffin embedded blocks obtained from Department of Oral and Maxillofacial Pathology were studied. The case details were retrieved which consisted of histopathologically diagnosed cases of OSCC (n = 20), low risk OED (n = 30), high risk OED (n = 30) and normal appearing mucosa (n = 20) were taken as standard for comparison. Ki-67 immunostaining was detected. Ki-67 positive cells were counted in the five random high power fields in each case.

Results:

Ki-67 labeling Index (LI) was restricted to the basal and parabasal layers of the normal oral epithelium irrespective of age, sex and site whereas it was seen in the basal, suprabasal and spinous layers in OED. Ki-67 LI is increased in high risk cases than the low risk cases of OED. Ki-67 positive cells in OSCC were located in the periphery of the tumor nests than the center, where frequent mitoses were observed.

Conclusion:

The architectural alteration evaluated by Ki-67 antibody in proliferating cell distribution in the layers of epithelial dysplasias may provide useful information to evaluate the grading of OED. Ki-67 LI increased in high risk cases than low risk cases of OED. This study showed that over expression of Ki-67 antigen between well-differentiated and poorly differentiated OSCC was in accordance with histologic grade of malignancy but not in accordance with moderately differentiated OSCC.

Expression of Cyr61 in primary salivary adenoid cystic carcinoma and its relation to Ki-67 and prognosis

Cysteine-rich protein 61 (Cyr61) selectively binds heparin and insulin-like growth factors and mediates a variety of biological actions, including cell adhesion, differentiation, proliferation, migration, angiogenesis, and tumorigenesis. Cyr61 is also a prognostic factor for tumor progression and survival of individuals with various types of tumors. This study investigated the relationship between the expression level of Cyr61 and clinicopathological features, as well as the prognostic significance of Cyr61 expression in human salivary adenoid cystic carcinoma (SACC). The expression of Cyr61 and Ki-67, a cell-proliferation marker, was examined immunohistochemically in paraffin embedded tissue specimens from 60 SACC patients who underwent radical surgery between 1995 and 2004. A chi-square test was used to investigate the relationship between Cyr61 and Ki-67 expression and clinicopathological features. Survival analysis was performed to determine the prognostic significance of Cyr61 expression. Cyr61 expression was observed in 39 cases (39/60, 65%) of SACC, and Cyr61 expression was positively correlated with Ki-67 expression (P=0.002). A high expression of Cyr61 was significantly associated with solid subtype, perineural invasion, vascular invasion or cancer embolus, advanced stage, recurrence, and metastasis (P<0.05). The survival rate of patients with high expression of Cyr61 or Ki67 was significantly lower than that of patients with low expression. Multivariate Cox's proportional hazards analysis showed that vascular invasion, TNM stage, recurrence, distant metastasis, Ki-67 expression, and Cyr61 expression were independent prognostic factors of overall survival (P<0.05). Cyr61 expression is significantly correlated with Ki-67 expression and may have potential value in screening high-risk cases for recurrence and metastasis, as well as identifying poor prognosis in SACC patients.

mRNA expression of the DNA replication-initiation proteins in epithelial dysplasia and squamous cell carcinoma of the tongue

BACKGROUND

The tongue squamous cell carcinomas (SCCs) are characterized by high mitotic activity, and early detection is desirable. Overexpression of the DNA replication-initiation proteins has been associated with dysplasia and malignancy. Our aim was to determine whether these proteins are useful biomarkers for assessing the development of tongue SCC.

METHODS

We analyzed the mRNA expression of CDC6, CDT1, MCM2 and CDC45 in formalin-fixed, paraffin-embedded benign and malignant tongue tissues using quantitative real-time PCR followed by statistical analysis.

RESULTS

We found that the expression levels are significantly higher in malignant SCC than mild precancerous epithelial dysplasia, and the expression levels in general increase with increasing grade of precancerous lesions from mild, moderate to severe epithelial dysplasia. CDC6 and CDC45 expression is dependent of the dysplasia grade and lymph node status. CDT1 expression is higher in severe dysplasia than in mild and moderate dysplasia. MCM2 expression is dependent of the dysplasia grade, lymph node status and clinical stage. The expression of the four genes is independent of tumor size or histological grade. A simple linear regression analysis revealed a linear increase in the mRNA levels of the four genes from the mild to severe dysplasia and SCC. A strong association was established between CDC6 and CDT1, and between MCM2 and CDC45 expression. The nonparametric receiver operating characteristic analysis suggested that MCM2 and CDC45 had a higher accuracy than CDC6 and CDT1 for distinguishing dysplasia from tongue SCC.

CONCLUSION

These proteins can be used as biomarkers to distinguish precancerous dysplasia from SCC and are useful for early detection and diagnosis of SCC as an adjunct to clinicopathological parameters.

State of the art in antigen retrieval for immunohistochemistry

The masking effects of antigens by chemical fixation, processing, embedding media interactions, represent a serious problem for immunohistochemical purposes. Fortunately, different approaches in antigen retrieval exist. These techniques are relatively recent and continuously expanding. This review focuses on the present state of the art in antigen retrieval methods for immunohistochemistry in light and electron microscopy. Moreover, a brief discussion on the chemical aspects of fixation, mechanism of retrieval, as well as its efficacy, is given.

Carcinoma ex pleomorphic adenoma of the salivary gland: an immunohistochemical study

The proliferative activity of the tumor cells and the expression of tumor-associated genes and sex steroid hormone receptors were investigated immunohistochemically in ten cases of carcinoma ex pleomorphic adenoma (Ca-ex-PA) of the salivary glands. These were analyzed in benign and malignant components separately, and then were compared with ten cases of the other malignant tumors [adenocarcinomas, not otherwise specified (ACN) and salivary duct carcinomas (SDC)] and ten cases of pleomorphic adenomas (PA). The results obtained in this study were as follows: (1) malignant component of Ca-ex-PA showed a higher incidence of PCNA and Ki67 than benign component of Ca-ex-PA. A significant difference between benign component of Ca-ex-PA and PA was not observed. (2) A significant difference in the incidence of p53, c-erbB-2, EGFR overexpression was observed only between malignant component of Ca-ex-PA and benign component of Ca-ex-PA. (3) The incidence of PCNA, Ki67, p53, c-erbB-2 overexpression in malignant component of Ca-ex-PA showed the highest data among the four groups. These results suggest that Ca-ex-PA acquired the particular biological behavior in contrast to the other salivary neoplasms in the long-standing process while PA undergoes malignant transformation.

Quantification of silver-staining nucleolar organizer region in epithelial cells of tongue of mice after exposure to, or intake of, alcohol

The purpose of the current study was to evaluate the effect of alcohol on the proliferative activity of epithelial cells in the lingual mucosa of mice by means of silver-staining nucleolar organizer region (AgNOR) count and area measurements. Forty-eight CF1 mice were separated into three groups. The test groups were submitted to topical exposure to, or intake of, 40% (volume/volume) ethyl alcohol. Biopsy specimens were collected from the middle third of the dorsal tongue at 0, 6, and 12 months, and samples were stained according to the AgNOR technique. Mean number and mean area of AgNOR per nucleus were calculated for 50 basal layer cells and 50 intermediate layer cells. Increases in mean number and mean area of AgNOR per nucleus in intermediate cells were observed at 12 months in the alcohol intake group (P < .05). Results showed that intake of 40% alcohol increased epithelial cell proliferation in the dorsal surface of lingual mucosa.

Expression of peroxisome proliferator-activated receptors in the liver of gray mullet (Mugil cephalus)

During the last decade, peroxisome proliferation has emerged as a novel biomarker of exposure to certain organic chemical pollutants in aquatic organisms. Peroxisome proliferation is mediated by nuclear receptors, peroxisome proliferator-activated receptors (PPARs). Three PPAR subtypes have been described in mammals: PPAR alpha, PPAR beta and PPAR gamma. PPARs have also been discovered in several fish species. The aim of the present study was to investigate the expression of PPAR subtypes and their cellular distribution patterns in the liver of gray mullet Mugil cephalus, a fish species widely distributed in estuaries and coastal areas in Europe and used as sentinel of environmental pollution. For this purpose, antibodies were generated against the three subtypes of mouse PPARs and different protocols of antigen retrieval were used. In western blots, main bands were detected of approximately 44 kDa for PPAR alpha, two bands of 44 and 58 kDa for PPAR beta and a single band of 56 kDa for PPAR gamma. Similar results were obtained in mouse liver and may indicate antibody recognition of two forms of the protein in certain cases. PPAR alpha was the subtype most markedly expressed in gray mullet liver, being expressed mainly in melanomacrophages, nuclei of hepatocytes and sinusoidal cells and connective tissue surrounding bile ducts. PPAR beta was expressed in the same cell types but immunolabeling was generally weaker than for PPAR alpha. PPAR gamma showed very weak expression; positivity was mainly found in melanomacrophages and connective tissue surrounding bile ducts. Our results demonstrate that all the three PPAR subtypes are expressed in gray mullet liver but in different intensities. The cellular distribution patterns of PPAR subtypes in gray mullet liver resembled partly those found in mouse liver with PPAR alpha as the main subtype expressed in hepatocytes. The fact that melanomacrophages, cells of the immune system in fish, show strong expression of both PPAR alpha and PPAR beta whereas PPAR gamma expression is almost restricted to this cell type suggest a significant role of PPAR-mediated regulation of cell function in melanomacrophages.

Expression of vascular endothelial growth factor in salivary gland carcinomas and its relation to p53, Ki-67 and prognosis

BACKGROUND

Vascular endothelial growth factor (VEGF) has been demonstrated to play an important role in tumor angiogenesis and to influence prognosis in many cancers. But, its significance in salivary gland carcinomas has not been elucidated. The authors investigated the association between VEGF expression and clinicopathological factors, p53, and Ki-67 to verify its validity as a prognostic factor.

METHODS

Surgical specimens from 45 patients with salivary gland carcinoma were examined for VEGF, p53, and Ki-67 expression by immunohistochemical staining. The results were compared with the clinicopathological factors and the relationships were correlated.

RESULTS

VEGF expression was low in 14 cases, moderate in 15 cases, and high in 16 cases. It was significantly correlated with a variety of clinicopathological factors such as TNM stage, perineural and vascular invasion, and recurrence. VEGF showed significant association with the expression of p53 but not with that of Ki-67. Univariate analysis showed that age, gender, lymph node metastasis, vascular invasion, p53, Ki-67, and VEGF expression correlate with prognosis. Multivariate analysis demonstrated that VEGF is an independent prognostic factor for patients with salivary gland carcinomas.

CONCLUSIONS

The results of this study suggest that VEGF expression is correlated with p53 expression and that it may have prognostic value in salivary gland carcinomas.

Comparison of cell proliferation in the centre and advancing fronts of oral squamous cell carcinomas using Ki-67 index

The cell proliferation status of 60 oral squamous cell carcinomas from Sri Lankan subjects was examined by immunohistochemistry using the Ki-67 index. A comparison was made between the indices derived from the centre of the tumours and those derived from the invasive fronts of the same tumours. There was a positive correlation between the two indices suggesting a clonal expansion of malignant cells, but the mean index derived for the invasive fronts (29.75 11.64) was significantly higher than the mean index for the body of these tumours (25.65 11.64). Thus, at a given time, more peripheral cells at the invasive front are proliferating and this compartment is likely to be more informative in prognostic and other behavioural studies involving the cell cycle. In squamous carcinomas, increased and uncontrolled cell proliferation at the invasive front may be one feature contributory to the invasion.

Cell kinetics and apoptosis in laryngeal carcinoma patients

Cellular proliferation and apoptosis are both implicated in the process of carcinogenesis. The objective of this study was to access the prognostic significance of the expression of proliferating cell nuclear antigen (PCNA) and the apoptosis-related genes (bax, bcl-2, and p53) in laryngeal carcinoma patients. Thirty consecutive patients with stage I to IV squamous cell laryngeal carcinoma were treated in our department from 1992 to 1994. We immunohistochemically studied the expression of PCNA and bax, bcl-2, and p53 genes in their tumor specimens. Five healthy men were used as the control group. The staining results were correlated with clinicopathologic data. The PCNA protein expression was correlated with a significantly worse survival in those patients who were bax-negative (0% versus 42.86%, p = .0445). Similarly, the presence of PCNA led to an unfavorable clinical outcome in those patients who were bax-negative, bcl-2-negative, and p53-negative (0% versus 50%, p = .0278). Expression of bcl-2 protein was found to be an independent prognostic factor related to an unfavorable clinical outcome (p = .0262). The expression of bcl-2 protein appears to predict survival in laryngeal carcinoma patients. Furthermore, the combined study of proliferation markers and apoptosis-related genes helped us to identify a high-risk group of patients who may benefit from a more aggressive treatment protocol.

Antigen retrieval on formaldehyde-fixed paraffin sections: its potential drawbacks and optimization for double immunostaining

It is well known that the major artifact induced by formaldehyde fixation is the masking of tissue antigens due to cross-linking of protein amino acid residues. Recently many antigen retrieval techniques have been devised to unmask the hidden antigen epitopes and recover immunoreactivity. In this study, some practical problems of two common unmasking techniques, i.e. heat-induced epitope retrieval and enzyme digestion have been reviewed in immunostaining of proliferating cell nuclear antigen (PCNA) on formaldehyde-fixed paraffin-embedded sections. As the heating conditions became more severe, false-positive staining and/or nonspecific background staining occurred. Based on the principle of protein inactivation/denaturation and the possible mechanisms of antigen retrieval, it has been suggested that the antigen retrieval itself can also denature proteins in tissues, just as many other protein inactivation processes. Thus, the total magnitude of protein conformational change caused by the overall unmasking procedure is in practice crucial. To prove this hypothesis and to overcome such undesirable drawbacks after antigen retrieval, a new combination technique of a mild heating condition (microwaved at 80 degrees C for 15-20min) and pepsin digestion was devised. This technique led to a strong specific immunoreactivity of PCNA, without any undesirable false positive or background staining. The procedure was also adapted for double immunostaining of PCNA together with alpha-actin, bromodeoxyuridine, keratin, type IV collagen and vimentin.

Evaluation of p53, PCNA, Ki-67, MDM2 and AgNOR in oral peripheral and central giant cell lesions

OBJECTIVES

Peripheral giant cell lesion (PGCL) and central giant cell lesion (CGCL) of the jaws have a distinct clinical behaviour. Whether such biological differences are supported by a distinct pattern of proliferation markers or cell cycle associated proteins expression is not known. Therefore the purpose of the present study was to compare the immunohistochemical expression of p53, MDM2, Ki-67, PCNA and the histochemical expression of argyrophilic nuclear organiser region (AgNOR) on PGCL and CGCL of the jaws.

MATERIALS AND METHODS

Paraffin wax blocks of 14 cases of PGCL and 12 cases of CGCL were retrieved. A biotin-streptavidin amplified system was used for identification of the antigens. The AgNOR number was also evaluated.

RESULTS

Ki-67 immunoreactivity was greater in the mononuclear cells of PGCL compared to CGCL. PCNA and AgNOR staining were similar in PGCL and CGCL. Prominent MDM2 immunoreactivity was observed in all tissues investigated. By contrast, there was no p53 immunoreactivity.

CONCLUSIONS

Although CGCL present a more aggressive clinical behaviour, it has a decreased proliferative activity compared to PGCL. Finally, p53, MDM2, PCNA, Ki-67 immunohistochemical expression and AgNOR histochemical expression do not reflect their distinct biological behaviour.

The association between epithelial proliferation and disease progression in the oral mucosa

The purpose of this study was to examine the possible association between epithelial proliferation and disease progression in the oral mucosa. Archival specimens of normal oral mucosa (n = 12), dysplasia (n = 17) and squamous cell carcinoma (n = 18) were sectioned and proliferating cells visualised by staining with Ki-67 antibody. The proliferative index of the epithelium (PI) was determined by total cell counts and point counting. Similar results were obtained using either method. Comparison of the three groups of tissues by one-way analysis of variance showed a significant increase in PI with increasing lesion severity (p < 0.001). The PI of both dysplasia and carcinoma groups was significantly higher than that of normal oral mucosa (p < 0.001). However, the difference between dysplasia and carcinoma groups was not significant. PI was not associated with tobacco or alcohol consumption. We therefore conclude that Ki-67 expression is an early marker of disease progression in the oral mucosa but, on its own, is not a good indicator of neoplastic transformation.