Immunohistochemical demonstration of p53 protein in colorectal adenomas and adenocarcinomas. Reliable application of the heat-induced antigen retrieval method to formalin-fixed, paraffin-embedded material

Differential expression of p53 and p504s in hyperplastic polyp, sessile serrated adenoma and traditional serrated adenoma

AIMS

Known collectively as serrated polyps, hyperplastic polyps (HP), sessile serrated adenomas (SSA/SSP) and traditional serrated adenoma (TSA) may represent a spectrum of increasing malignant potential with characteristic immunological markers. There is increasing evidence that HP, SSA/SSP and TSA are biologically different and are likely to represent a spectrum along the serrated polyp pathway. Although there is general consensus about the diagnostic features of serrated polyps, the morphological differences between the categories are often subtle. This study compares the expression of p53 and P504S among serrated polyps. Sixty seven randomly selected biopsies (n = 59) and resection specimens (n = 8) histologically diagnosed for SSA/SSP, TSA and HP (19, 30 and 18 specimens, respectively) were obtained.

METHODS AND RESULTS

There was a significant difference in p53 (P < 0.001) and P504S (P < 0.001) immunopositivity and distribution among the serrated polyps. In particular, there is diffuse expression p53 and P504S in TSA compared to HP and SSA/SSP where p53 and P504S expression was more frequently confined to the lower 1/3 of the crypts. In addition, percentage of cells expressing p53 and p504S expression was higher in TSA than those of HP and SSA/SSP.

CONCLUSION

Immunostains, p53 and P504S, may be useful adjuncts to morphological diagnosis of serrated polyps.

Advanced colorectal polyps with the molecular and morphological features of serrated polyps and adenomas: concept of a 'fusion' pathway to colorectal cancer

AIM

To establish and explain the pattern of molecular signatures across colorectal polyps.

METHODS AND RESULTS

Thirty-two sessile serrated adenomas (SSA), 10 mixed polyps (MP), 15 traditional serrated adenomas (SA), 49 hyperplastic polyps (HP) and 84 adenomas were assessed for mutation of KRAS and BRAF and aberrant expression of p53. The findings were correlated with loss of expression of O-6-methylguanine DNA methyltransferase (MGMT). KRAS mutation occurred more frequently (26.5%) than BRAF mutation (4.8%) in adenomas (P < 0.001) and particularly in adenomas with villous architecture (50%). Loss of expression of MGMT correlated with KRAS mutation in small tubular adenomas (P < 0.04). BRAF mutation was frequent in HPs (67%) and SSAs (81%), while KRAS mutation was infrequent (4% and 3%, respectively). Of MPs and SAs, 72% had either BRAF or KRAS mutation. Aberrant expression of p53 was uncommon overall, but occurred more frequently in MPs and SAs (12%) than adenomas (1%) (P < 0.04) and there was concordant loss of expression of MGMT.

CONCLUSIONS

Molecular alterations that are characteristic of the serrated pathway and adenoma-carcinoma sequence can co-occur in a minority of advanced colorectal polyps that then show morphological features of both pathways. These lesions account for only 2% of colorectal polyps, but may be relatively aggressive.

Immunohistochemical evaluation of tissue-specific proteolytic enzymes in adenomas containing foci of early carcinoma: correlations with cathepsin D expression and other malignant features

BACKGROUND

Cathepsin D (CD) is an aspartyl lysosomal protease, and the prognostic value of CD expression has been studied in a variety of tumors, however, its role in early adenocarcinomas remains unclear.

AIM OF THE STUDY

We evaluated the expression of CD in a series of colorectal adenomas with severe dysplasia containing foci of early carcinoma and compared the results to several histopathological and immunohistochemical features.

METHODS

Adenomas were obtained by endoscopic polypectomy from 33 patients. Twenty-four of the 33 adenomas contained well-differentiated adenocarcinomas and nine adenomas contained moderately differentiated adenocarcinomas.

RESULTS

Positive CD expressions were observed in 25% of well-differentiated adenocarcinomas and in 66.7% of moderately differentiated adenocarcinomas (p < 0.05). Of the 12 adenocarcinomas with positive CD expression, four had positive CD expression in their adenomas (p < 0.01), 6 showed positive Ki-67 expression in their adenomas (NS), and 10 had positive p53 expression in their adenomas (p < 0.05). No significant association was seen between the level of CD expression and adenoma size.

CONCLUSIONS

The expression of CD in adenocarcinoma correlated significantly with differentiation, and with the levels of CD and p53 expression in the adenomas of the polyp.

Cell differentiation and chemotherapy influence p53 and Mdm2 immunoreactivity in human HT29 colon cancer cells grown in scid mice

Absence of a functional p53 gene product can lead to increased p53 accumulation in cancer cells. In this contribution, the association between cell differentiation, chemotherapy and p53 immunoreactivity in human HT29 colon cancer cells grown in scid mice as undifferentiated cells and as mucin containing signet-ring cells was investigated. Mutated p53 was more frequently expressed in the undifferentiated tumour cells than in the signet-ring cells. 5-fluorouracil (5FU) treatment resulted in a substantial increase in the p53-positive signet-ring cell population (from 17% to 45%) and in an increased Mdm2 immunoreactivity. These findings indicate that mutated p53 expression is related to the differentiation pattern and that tumour cells devoid of mutated p53 immunoreactivity are preferentially eliminated by 5FU treatment.

bFGF induces differentiation and death of olfactory neuroblastoma cells

Olfactory neuroblastoma (ONB) is a highly vascularized and malignant tumor arising in olfactory neuronal precursors from the paranasal sinuses. Previously, we showed that treatment of JFEN cells with transforming growth factor (TGF)-alpha caused them to differentiate and respond to chemical odorants, whereas basic fibroblast growth factor (bFGF) treated cells differentiated and died. In the present study we show that established ONB tumors treated with bFGF upregulate the bFGF receptor (FGFR1) prior to differentiation. This cellular differentiation was evidenced by bFGF-induced expression of the human runt homologue AML1 (PEBP2 alpha B, CBFA-2) that is highly expressed in developing olfactory neuroepithelium and TrkA, a preferred nerve growth factor receptor. Since TrkA is expressed in supporting cells, but not in mature olfactory neurons, we hypothesize that the expression of AML1 and TrkA in bFGF-treated JFEN cells induced supporting cell differentiation. Collectively, these results have implications for the treatment of patients afflicted with ONB.

Clinicopathological features of superficial depressed-type colorectal neoplastic lesions

OBJECTIVE

We performed this study to analyze the endoscopic findings, dissecting microscopic features, and p53 immunostaining in superficial depressed-type (depressed) colorectal neoplastic lesions.

METHODS

Dissecting stereomicroscopy was used to ascertain the size and pit pattern of lesions removed by endoscopic snare polypectomy. Immunohistochemical staining of p53 was performed with an antigen retrieval system using a monoclonal antibody to p53.

RESULTS

All depressed neoplastic lesions (submucosal carcinoma, n = 6; high-grade dysplasia, n = 14; and adenoma, n = 30) were small (< 1 cm in diameter) and were detected as a depression with or without a marginal elevation on colonoscopic examination. In the dissecting microscopic study, submucosal carcinomas and lesions of high-grade dysplasia almost exclusively showed irregular small pits, with the exception of four malignant lesions with moderate submucosal invasion in which the pit structure was absent. In contrast, adenomas had either regular small (29/30 lesions) or oval pits (1/30 lesions). Rates of p53 positivity were 100%, 64%, and 7% in depressed submucosal carcinomas, lesions of high-grade dysplasia, and adenomas, respectively, thus the prevalence of p53 positivity was significantly higher in the former two groups than in the adenoma group.

CONCLUSIONS

The high frequency of invasive carcinoma and high-grade dysplasia found in depressed colorectal neoplastic tumors, despite their small size, indicates that these lesions may be a subtype of colorectal tumor with more aggressive malignant potential at an earlier stage.

Immunophenotyping of human HT29 colon cancer cell primary tumours and their metastases in severe combined immunodeficient mice

The immunophenotype of HT29 human colon cancer cells implanted into severe combined immunodeficient mice was assessed in primary tumours and their metastases in the lungs using an indirect immunohistochemical method. After primary tumours were surgically removed, the metastases were given time to develop, thus paralleling the clinical situation. While vimentin was negative in both primary and secondary tumours, E-cadherin was present as membrane-bound labelling in the primary tumours only. Whereas the markers p53, MIB1, PCNA and CEA were consistently positive in both primary and metastatic tumours, CD44 variant 6 and CA125 were negative in metastases but positive in the primary tumours. There was a significant increase in the percentage of cells labelled for p53 in the primary tumours compared with the metastases. For the proliferation markers, there was no significant difference in labelling between primary tumours and metastases for MIB1. Of the cytokeratins examined, CK 20 gave the strongest and most consistent reaction in both primary and secondary tumours. The results indicate that, for certain immunohistochemical markers, results are the same in both primary tumours and metastases. Hence, in these cases, antigens that are expressed on the primary tumour as well as on the metastases can serve as target molecules for immunologically based forms of treatment of metastases.

Antigen retrieval immunohistochemistry: past, present, and future

The antigen retrieval (AR) technique, which is predominantly based on high-temperature heating of tissues, is used as a non-enzymatic pretreatment for immunohistochemical staining of formalin-fixed, paraffin-embedded tissue sections. It has been widely applied in pathology and analytical morphology. The existence of a growing body of literature on the AR technique raises a number of interesting issues for the further development of AR. These issues include the use of a "test battery" and the concept of "maximal retrieval" applied to the selection of optimal test protocols for the standardization of AR.

Antigen retrieval, signal amplification and intensification in immunohistochemistry

In this overview we emphasize new methods of improving immunohistochemical results in formaldehyde-fixed tissue samples. The benefit of heat-induced antigen retrieval in demasking of concealed epitopes is demonstrated. We provide guidance on the influence of heat-induced antigen retrieval in commonly applied monoclonal and polyclonal antibodies. Moreover, we show the promising methods of signal amplification using biotinylated tyramine and signal intensification of diaminobenzidine reaction products by metallic ions.

Heat-induced antigen retrieval of proliferating cell nuclear antigen and p53 protein in formalin-fixed, paraffin-embedded sections

Immunohistochemical demonstration of proliferating cell nuclear antigen (PCNA) and p53 protein is important, particularly for the surgical diagnosis of neoplastic disorders. An effective, simple and reproducible method was established for observing the expression of these intranuclear antigens in routinely processed, formalin-fixed paraffin-embedded sections. Dramatic improvement of the antigenicity was obtained when the deparaffinized sections were heated in a hot water bath at 90 degrees C for 120 min in 0.01 mol/L citrate buffer, pH 6.0, for PCNA and in 0.01 mol/L phosphate-buffered saline, pH 7.2, for p53 protein. These reliable pretreatments are useful for the detailed comparative analysis of the expression of PCNA and p53 protein and fine histologic architecture and for retrospective study using a large number of archival specimens.