Tumor suppressor genes and the practice of surgical pathology

Clinical significance of P16INK4A and retinoblastoma proteins in non-small-cell lung carcinoma

This study was performed to determine the frequency of expression loss of p16 and pRb; their relations with each other, tumour histology, tumour stage, nodal status, and survival in formalin fixed, paraffin embedded tumour tissues of patients with non-small-cell lung carcinoma (NSCLC). P16 and/or pRb expression loss is observed in 72 (75.8%) out of 95 patients, and 70 (73.7%) of them showed inverse correlation (P<0.05). Thirty-six (37.9%) of the p16 positive cases usually showed weak or moderate immunohistochemical staining. Loss of p16 expression was found to be significantly greater in squamous cell carcinoma than in adenocarcinoma cases, whilst no relation was observed with other clinical parameters. Immunohistochemical reactivity for pRb was generally moderate or strong. PRb expression loss was observed in 15.8% of the cases, and no relation was found between pRb loss and age, sex, tumour histology, tumour stage, or nodal status. PRb negative squamous cell carcinoma cases had significantly shorter survival independent of nodal status. These results suggest that disruption of p16/pRb pathway is frequently involved in NSCLC, and pRb expression loss in cases with squamous cell carcinoma may predict clinical outcome.

p53 protein accumulation and p53 gene mutation in colorectal cancer

Comparison of immunohistochemical methods for detection of protein p53 accumulation and molecular techniques for analysis p53 gene mutation in colorectal cancer is presented. Thirty eight patients were included: all underwent surgery without preoperative treatment. Sex of patients, tumor localisation, macro and microscopic type of cancer and staging according to Astler-Coller and Jass classifications were evaluated. Protein p53 accumulation was detected by the streptavidin-biotin method using DO-7 (Dako) antibody. The number of cells stained were classified semiquanititatively according to a scoring system: (-)no positive cells, (+) : 10-30% positive cells, (++) : 40-70% positive cells, (+++) : >70% positive cells. For all cancer samples, exons 5 to 9 of p53 gene were amplified from isolated genomic DNA. PCR products were subjected to single standed conformational polymorphism analysis. All product were also directly sequenced on ABI PRISM 377 apparatus using fluorescent dideoxyterminators chemistry. The protein p53 accumulation was detected in 53% (20/38), whereas p53 gene mutation was seen in 55% (21/38). Among them, 15 patients (39%) with overexpression showed mutation in exon 5-8 gene p53. Discrepancies between results were noted in 29%. In conclusion, the necessity of both methods immunohistochemical and molecular is indicated for the objective evaluation of functional and structural status of p53 gene and protein.

p53 immunohistochemistry of ulcerative colitis-associated with dysplasia and carcinoma

In order to evaluate the usefulness of p53 immunohistochemistry (IHC) in the diagnosis of ulcerative colitis-associated colorectal carcinoma (UCACRC), ordinary paraffin sections were examined in 61 cases with ulcerative colitis (UC) and 29 control cases without UC. Among the 61 cases with UC, 11 were complicated by carcinoma coexisting with dysplasia, three with dysplasia, and two cases with adenoma. There were a total of 38 dysplasias, including 33 low grade dysplasias (LGD) and five mixed low and high grade dysplasias (LGD + HGD). The results of p53 IHC were divided into diffuse, nested, scattered and sporadic patterns for 29 control cases. Diffuse and nested patterns were presumed to reflect mutant forms of p53 protein and were defined as overexpression of p53 protein. In non-neoplastic mucosa of UC, the frequency of p53 positive tubules was significantly higher in active phase (13.5-17.9%) than in resolving phase (3.9-6.5%) and in remission (0.7-2.4%), regardless of association with neoplasia. Eight of the 37 lesions of dysplasia (21. 6%) showed p53 overexpression: 12.5% in LGD and 80.0% in LGD + HGD. The rate of p53 overexpression was significantly higher in UCACRC (90.9%) than in non-neoplastic mucosa of UC (0%), LGD and sporadic colorectal carcinoma (54.5%), but it did not differ between UCACRC and LGD + HGD. Interestingly, the mucosa without dysplasia showed p53 overexpression in one case of UCACRC. The biopsy specimen taken 4 years before the diagnosis of carcinoma revealed p53 overexpression in another case with UCACRC. These results suggest that p53 abnormalities play an important role in UC-associated tumorigenesis in its relatively early phase. For the diagnosis of dysplasia and carcinoma in UC, p53 IHC seems to be useful.

p53 Protein accumulation as a prognostic marker of preoperative radiotherapy and/or chemotherapy in advanced squamous cell esophageal carcinoma--preliminary report

The correlation between immunohistochemical detection (IH) of p53 protein and tumor response to preoperative chemotherapy and/or radiotherapy in advanced esophageal squamous cell carcinoma was evaluated. Fifty-six patients with advanced esophageal squamous cell carcinoma were included in the study. All patients were staged and diagnosed microscopically before treatment. Patients were divided into three groups: 17 patients treated with chemotherapy and radiotherapy preoperatively (group I) (cisplatin and 5-fluorouracil, cobalt-60 therapy; total dose 3000 Gy); 19 patients treated with chemotherapy only (group II); and 20 patients who did not receive preoperative therapy (group III). The response of the tumor tissue to preoperative treatment was evaluated macroscopically and microscopically in operated specimens according to the classification: CR, complete response; PR1, major partial response with regression of at least 50% of initial tumor mass; PR2, minor partial response with regression of less than 50% of initial tumor mass. In all 56 patients immunohistochemistry was used to detect anti-p53 antibody (Dako, DO-7) in normal mucosa and cancer tissue. The response of the tumor was similar in both group I and group II. p53 protein was not expressed in the normal esophageal mucosa. A high level of p53 in operated specimens was associated with unfavorable tumor response to preoperative treatment. Therefore, immunohistochemical detection of p53 protein can be considered to predict the outcome of preoperative therapy.

Analysis of bcl-2 expression in normal, inflamed, dysplastic nasopharyngeal epithelia, and nasopharyngeal carcinoma: association with p53 expression

To further characterize bcl-2 expression in nasopharyngeal carcinoma (NPC), the authors analyzed bcl-2 expression immunohistochemically in biopsy specimens from 101 cases of NPC, of which 65 had the component of normal nasopharyngeal epithelium (NPE), 24 with dysplastic lesions adjacent to carcinoma, and 14 with both primary and metastatic lesions. An additional 25 nasopharyngeal biopsies of NPE from patients with chronic inflammation of nasopharynx were also included. The percentage of detectable bcl-2 expression shown in NPC (80%) and adjacent dysplastic lesions (71%) was significantly higher than in adjacent NPE (37%) and NPE from patients with chronic inflammation of the nasopharynx (30%) (P < .05). In both normal and inflamed NPE, the detectable bcl-2 expression was restricted to the basal cells; however, in dysplastic lesions, the bcl-2 staining distribution was increased with the dysplastic cell layers, and in entire layers of epithelium in severe dysplasia or carcinoma in situ. In addition, the staining intensity of bcl-2 in carcinomas and adjacent dysplastic lesions was generally stronger than that of adjacent NPE. These observations suggest that the expression of bcl-2 in dysplasia and carcinoma is enhanced relative to that of adjacent NPE. Enhanced bcl-2 expression to prevent apoptosis seems to occur from the early stages and may play an important role in the carcinogenesis of NPC. Furthermore, up to 77% of NPC with the coexpression of bcl-2 and p53 was observed and suggested that the association of bcl-2 and p53 expression seems to occur from the early stages of the development of NPC. The overexpression of p53 protein in NPC suggests that the mutation of p53 gene or altered function of wild-type p53 protein may contribute to the pathogenesis. It is conceivable that the presence of both enhanced bcl-2 expression and altered p53 functions may play a crucial synergistic effect in the carcinogenesis of NPC.

bcl-2 expression in the spectrum of preinvasive breast lesions

BACKGROUND

The bcl-2 gene encodes for a protein that blocks apoptosis. Although the bcl-2 protein has been identified in some invasive breast cancers, its expression in preinvasive breast lesions has not been well characterized.

METHODS

We studied bcl-2 expression using immunohistochemistry in cases of normal breast tissue (n = 10), ductal hyperplasia (n = 18), atypical ductal hyperplasia (ADH) (n = 10), atypical lobular hyperplasia/lobular carcinoma in situ (lobular neoplasia, LN) (n = 10), and ductal carcinoma in situ (DCIS) (n = 42). We also related bcl-2 expression to p53 expression in these lesions because the p53 gene is altered in many invasive breast cancers and is also involved in the regulation of apoptosis.

RESULTS

bcl-2 was consistently expressed in the epithelial cells in all normal breast tissue, ductal hyperplasia, ADH, and LN lesions. In contrast, bcl-2 expression was present in 76% of the DCIS cases and was related to the histologic grade of DCIS. Staining for bcl-2 was observed in 100% of the well differentiated DCIS cases, 90% of intermediately differentiated cases, and 33% of poorly differentiated cases (P < 0.001). No immunoreactivity for the p53 protein was seen in any of the cases of normal breast tissue, ductal hyperplasia, ADH, or LN lesions. However, 24% of the DCIS cases were p53 positive. The bcl-2+/p53- phenotype, as seen in all cases of normal breast tissue, ductal hyperplasia, ADH, and LN was also observed in 67% of the DCIS cases. In contrast, the remaining 33% of DCIS cases showed combinations of bcl-2 and p53 expression that differed from that of normal breast epithelium and the other pathologic lesions studied. Most lesions with altered bcl-2/p53 phenotypes, including all bcl-2-/p53+ cases, represented examples of poorly differentiated DCIS.

CONCLUSIONS

The bcl-2 protein is consistently expressed in normal breast epithelium, ductal hyperplasia, ADH, and LN. bcl-2 expression is variable in DCIS. Among DCIS cases, bcl-2 is most common in well differentiated and intermediately differentiated lesions. Most DCIS lesions are bcl-2+ and p53-, similar to normal epithelium, benign proliferative lesions, and LN. However, a minority of DCIS lesions show combinations of bcl-2 and p53 expression that differ from normal breast epithelium and from the other pathologic lesions studied. It is possible that such lesions may represent a subset of DCIS in which the regulation of apoptosis is no longer under normal control mechanisms, resulting in enhanced tumor cell survival and tumor growth.