Genetic analysis of the human oncoprotein MDM2 in benign and malignant tumors of the salivary gland.

INTRODUCTION: Genetic alterations of oncogene MDM2 promote malignant transformation of several human tumors. In tumors of the salivary gland, however, the genetic status of MDM2 has not been evaluated so far. METHODS AND RESULTS: Benign and malignant tumors of the salivary gland (6 pleomorphic adenomas, 3 Warthin's tumors, 1 adenocarcinoma, 1 basal cell adenocarcinoma, 1 mucoepidermoid carcinoma, 3 acinic cell carcinomas, 2 adenoid cystic carcinoma, 1 squamous cell carcinoma) were analyzed by fluorescence-based PCR techniques and immunochemistry for MDM2 gene amplification, MDM2 gene expression, MDM2 gene mutation, MDM2 RNA splicing and MDM2 accumulation. Data show that all samples contained nonamplified MDM2 genes with nonmutant zinc finger regions. However, in two benign and two malignant samples, novel MDM2 mRNA splicing variant types 1 and 2 were detected. Furthermore, three malignant tumors revealed significant nuclear MDM2 accumulation. Correlation between levels of MDM2 mRNA and MDM2 protein could not be detected in the specimens. CONCLUSION: The present study suggests that MDM2 gene mutation and gene amplification do not contribute to MDM2 accumulation detected in malignant tumors of the salivary gland. However, the role of novel MDM2 splicing variants in MDM2 expression and malignant transformation must be elucidated further.

Relationship between DNA ploidy-related parameters and the deletions in mismatch repair genes MLH1 and MSH2 in lentigo maligna and malignant melanomas.

Defects in DNA mismatch repair genes MLH1 and MSH2, first described in hereditary nonpolyposis colon cancer (HNPCC), have been postulated to be responsible for malignant transformation in several tumours. To date there are no data on cutaneous tumours. Using a PCR assay it was possible to identify deletions in MSH2 (exonic regions 12 and 13) in 16 of 47 lentigos maligna and in 10 of 36 malignant melanomas. Deletions in MLH1 (exonic regions 15 and 16) were found in 11 of 47 lentigos and in 15 of 36 melanomas. Comparison of DNA ploidy-related parameters between lentigos with and without exonic deletions in MSH2 and MLH1 did not show any significant differences. In contrast, melanomas positive and negative for exons 12 and 13 (MSH2) (26/36 and 10/36, respectively) differed significantly with respect to the percentages of diploid cells (P = 0.0179) and tetraploid cells (P = 0.0042). Comparison of melanomas positive and negative for exons 15 and 16 (MLH1) (21/36 and 15/36, respectively) showed significant differences in the percentage of aneuploid cells between 2c and 4c (P = 0.0141) and tetraploid cells (P = 0.0404). In summary, deletions in DNA mismatch repair proteins MSH2 and MLH1 were present both in lentigo maligna and in melanomas and correlated with DNA ploidy-related parameters in malignant melanomas.

Fragments of human oncoprotein MDM2 reveal variable distribution within and on cultivated human hepatoma cells.

Human oncoprotein MDM2 reveals a MHC class I binding motif HMDM441 characterizing MDM2 as a potential tumor antigen. To analyze the distribution of MDM2 proteins containing this motif in liver cancer cells we produced rabbit anti-HMDM441 serum. The novel antibodies bound to an MDM2 fragment of approximately 55 kDa which lacked the N-terminal region and was present in lysate and supernatant of a human hepatoma cell line overexpressing normal 90-kDa MDM2. The 55-kDa fragment was detected in the cytoplasm and nucleoli and at the nuclear envelope of hepatoma cells, whereas normal hepatocytes were negative. Double-fluorescence labeling indicated that the MDM2 fragments and MHC class I molecules were coexpressed on the surface of the hepatoma cells. Further studies must clarify whether MDM2 fragments containing motif HMDM441 are novel targets of immunotherapy and immunochemical tumor diagnosis.

Gene expression analysis of the catalytic subunit of human telomerase (hEST2) in the differential diagnosis of serous effusions.

Diagnostic accuracy in effusion cytology based on morphologic examination is not always satisfactory. Therefore, various diagnostic adjuncts such as immunocytochemistry or deoxyribonucleic acid cytometry are employed in this diagnostic field. Recently, demonstration of telomerase activity has been proposed as a possible marker for malignancy. In this study a seminested reverse transcription-polymerase chain reaction (RT-PCR) strategy for expression analysis of the catalytic subunit of human telomerase (hEST2) was used in 58 serous effusions. RT-PCR results correlated with cytologic diagnoses in 14 of 17 malignant effusions. In eight effusions cytologically suspicious for malignancy, PCR results were in accordance with the clinical follow-up. However, hEST2 RT-PCR was also positive in six of 15 cytologically benign effusions that consisted predominantly of inflammatory and mesothelial cells. Using the telomeric repeat amplification protocol, it could be demonstrated that cultured, proliferating benign mesothelial cells may present a weak telomerase activity, as is known in other benign cells including activated lymphocytes. In conclusion, the simple and rapid method of hEST2 RT-PCR serves to support the cytologic diagnosis of malignancy, but false-positive PCR results resulting from activated lymphocytes and proliferating mesothelial cells must be considered.

Relation between DNA ploidy status and the expression of the DNA-mismatch repair genes MLH1 and MSH2 in cytological specimens of melanoma lymph node and liver metastases.

DNA-mismatch repair is essential for preventing genetic instability, and its important protective role has been demonstrated in several tumors. The main aim of this study was to investigate the expression of MLH1 and MSH2 (on the RNA level) in melanoma liver and lymph node metastases, and to define the relation between DNA ploidy status and mismatch repair gene expression. MLH1 was found in 29/33 melanoma lymph node and in 5/17 melanoma liver metastases. MSH2 was present in 26/33 lymph node and 5/17 liver metastases. A comparison of MLH1 and MSH2 positive and negative melanoma metastases showed that there were highly significant differences in the percentages of diploid cells, aneuploid cells between 4c and 8c, octaploid cells, and 5c exceeding rate. This fact confirms the strong relation between the loss of DNA-mismatch repair gene expression and advanced DNA aneuploidy status in melanoma metastases.

Analysis of the DNA content in the progression of recurrent and metastatic melanomas.

Ploidy status and ploidy related parameters of 18 primary melanomas, 32 recurrences and 18 lymphatic metastases were investigated applying CAS200 image analyzer. All the tumours investigated were either suspicious for aneuploidy (Auer III) or clearly aneuploid (Auer IV). Primary melanomas differed from recurrent tumours concerning the percentage of aneuploid cells between 4c and 8c and 5c ER. Comparison of cutaneous tumours with lymphatic metastases showed a significant difference concerning the percentage of aneuploid cells between 2c and 4c. An already high aneuploidy rate in primary tumours suggests that recurrent and metastatic clones of cells are present in early stages and that aneuploidy status in primary melanomas could be regarded as one of the risk factors of recurrences and metastases.

Prognostic significance of newly defined ploidy related parameters in melanoma.

5c exceeding rate is the parameter, most frequently showing prognostic impact. The CAS200 image analyzer makes possible the measurement of additional parameters defining single subfractions of cells, as for example the ratios of diploid, aneuploid, tetraploid, octaploid and 16-ploid cells. The main objective of this study was to define the prognostic significance of these new parameters in 106 primary melanomas with known survival time. 29 out of 106 melanomas were euploid. 77 out of 106 showed an aneuploid histogram. Multivariate analysis with Cox regression demonstrated that the percentage of aneuploid cells between 2c and 4c and the percentage of aneuploid cells between 4c and 8c, but not 5c exceeding rate, were able to influence survival time.

Relationship between GAGE-1/-2 expression, EBV infection and interferon-gamma expression in undifferentiated carcinoma of nasopharyngeal type.

GAGE-1/-2 proteins are novel tumour markers, functionally related to tumour rejection. The objective of the present study was to identify the existence of a relationship between GAGE-1/-2 expression, Epstein Barr Virus (EBV) infection and viral infection-induced cytokine expression in cultivated tumour cells and archival specimens of undifferentiated carcinoma of nasopharyngeal type (UCNT). PCR and in situ hybridization techniques were employed. In cultivated UCNT cells, interferon-gamma (IFN-gamma) induced synthesis of GAGE-1/-2 mRNA. In archival tumour specimens (n = 10) however, GAGE-1/-2 gene expression was detected in only 3/8 cases with coincident EBV infection and IFN-gamma expression. In conclusion, EBV infection appears to induce IFN-gamma gene expression in most tumors, but GAGE-1/-2 expression in only some tumours. The role of IFN-gamma and other factors in triggering GAGE-1/-2 gene activation must be elucidated further. The relevance of GAGE-1/-2 gene expression and its detection by PCR for future immunotherapy is discussed.

Proliferative activity in the progression of pigmented skin lesions, diagnostic and prognostic significance.

Proliferative compartments of a tumour can be determined cytophotometrically, by in situ hybridisation or by immunohistochemical detection of Ki67 antigen. The main objective of this study was to analyse the proliferative activity during the progression of pigmented skin lesions with respect to differential diagnostic and prognostic applications. The material investigated consisted of 209 pigmented skin lesions (31 naevi, 30 dysplastic naevi, 106 primary melanomas, 20 lymphatic and 22 organ melanoma metastases). Comparison of the ratios of cells in the S-phase gained by two different methods (cytometry, in situ hybridisation) did not show any significant differences. The correlations between Ki67 and S-phase indices in every diagnostic group were highly significant. The results of forward and backward Cox regression were identical and only Ki67 showed an independent prognostic influence (p < 0.001, coefficient in regression 0.02) with change in risk 2% and confidence limit ranging between 1.1% and 2.9%.

Comparison of the DNA content in liver cell adenoma, hepatocellular carcinoma and regenerative nodules.

With regard to neoplasms of hepatocytes, diagnostic pitfalls have been reported for differentiation of liver cell adenoma (LCA) from well differentiated hepatocellular carcinoma (HCC). Since cytophotometric analysis of the DNA content with the help of image analysis has proven to be of diagnostic value in various neoplasms, we examined its ability to discriminate between LCA and HCC as well as regenerative liver nodules. The material investigated consisted of 54 cases of HCC, 10 benign liver tumours and 10 cases suspicious for HCC. All the benign liver tumours demonstrated an euploid histogram. 9 out of 10 borderline tumours were euploid while 1 out of 10 was suspiciously aneuploid. Among HCC, 21 out of 54 were euploid, 18 out of 54 suspiciously and 15 out of 54 clearly aneuploid. 5c exceeding rate differed significantly between benign liver changes and borderline lesions (p = 0.0474) as well as between borderline lesions and malignant tumours (p = 0.0108). We conclude that the use of image cytometry is helpful as an additional criterion for more diagnostic accuracy in morphologically difficult cases.

Cytologic diagnosis of medullary carcinoma of the thyroid gland.

The cytomorphologic features in fine-needle aspiration (FNA) biopsies from 91 histologiacally verified medullary carcinomas of the thyroid (MCT) were investigated. FNA was able to diagnose neoplasms with indications of surgical removal in 98.9% of cases and moreover, was accurate in specific tumor typing in 89% of cases. The most important cytologic criteria of MCT with FNA are: dispersed cell-pattern of polygonal or triangular cells, azurophilic cytoplasmic granules, and extremely eccentrically placed nuclei with coarse granular chromatin and amyloid. These and other cytologic features of MCT are discussed in detail. Fourteen cases of thyroid tumors originally diagnosed as MCT by cytology are illustrated to discuss the differential diagnosis of MCT and its potential pitfalls. If MCT is cytologically presumed but amyloid and azurophilic cytoplasmic granules are not demonstrated, the use of immunostaining is necessary for a correct tumor typing. The application of immunocytochemistry in MCT is discussed.

Comparative study of the expression of DNA mismatch repair genes, the adenomatous polyposis coli gene and growth arrest DNA damage genes in melanoma recurrences and metastases.

The main goal of this study was to examine the expression of DNA mismatch repair genes (MLH1, MSH2, PMS1 and PMS2), the adenomatous polyposis coli (APC) gene and growth arrest DNA damage inducible (GADD) genes (GADD34, GADD45 and GADD153) in the different stages of melanoma recurrences and metastases, and to identify any mutual consistencies in their expression pattern. All the cases of primary melanoma examined showed a reduced expression of DNA repair genes. These results demonstrate that disturbances of DNA repair begin in the early stages of melanoma. No significant differences were found in the expression of these markers between cutaneous melanomas and their recurrences and metastases (P> 0.05). Eighteen significant correlations between markers were found in the primary melanomas, and 10 significant correlations were observed in the first recurrences of melanoma. In contrast, 27 statistically significant relationships were demonstrated in metastatic lymph nodes. The different correlations found in primary and metastatic tumours confirmed the hypothetical difference in marker interaction in the diagnostic groups investigated. Our results suggest that DNA repair genes may play an important role in the recurrence and metastasis of melanomas.

Analysis of the DNA mismatch repair proteins expression in malignant melanomas.

The importance of properly functioning DNA mismatch repair has been shown in several tumour types both hereditary and sporadic, but not yet in malignant melanomas. The aim of this study was to examine the expression of DNA mismatch repair genes (MLH1, MSH2, PMS1 and PMS2) in primary melanomas and to define their possible prognostic impact in 106 primary melanomas. MLH1 was found in 64 and MSH2 in 61 out of 106 melanomas. PMS1 and PMS2 proteins were present in 69 and 67 tumours, respectively. Loss of the expression of DNA mismatch repair proteins correlated with the increase of Clark levels. Cox regression analysis demonstrated some prognostic significance for PMS1 (forward p = 0.0018 and backward selections p = 0.0277), MLH1 (only forward selection p = 0.0081) and MSH2 (only backward selection p = 0.0115).

MAGE-1, GAGE-1/-2 gene expression in FNAB of classic variant of papillary thyroid carcinoma and papillary hyperplasia in nodular goiter.

Differentiation of the papillary variant of papillary thyroid carcinoma (PTC) from papillary hyperplasia in nodular goiter may be difficult in fine-needle aspiration biopsy (FNAB) by means of morphology alone. To improve cytodiagnostic accuracy the occurrence of MAGE-1, GAGE-1/-2 gene expression was analyzed by means of RT-PCR. The genes investigated are recognized by autologous T lymphocytes and are expressed in carcinomas of various sites e.g. lung, ovary, colon but not in non-neoplastic tissue except testis. Routinely obtained smears with cytologic diagnosis of PTC confirmed by histology (n=20) and diagnosis of nodular goiter (n=10) were investigated. The MAGE-1, GAGE-1/-2 PCR products were found in 6/20 of the carcinomas but in none of the benign lesions. To identify PCR products automatic gene-sequencing in all positive cases was performed. The data indicate that MAGE-1, GAGE-1/-2 gene expression may give additional information to delineate PTC from papillary hyperplasia in FNAB.

Expression of DNA mismatch repair genes in naevi.

The significant difference of DNA mismatch repair genes expression between naevi and melanomas was demonstrated by our research group in the previous study. The main aim of this study was to compare the expression of MLH1, MSH2, PMS1 and PMS2 in 31 naevus cell naevi, 12 fibromatous naevi and 30 dysplastic naevi. The expression of DNA mismatch repair proteins was found in all naevi investigated. However, the expression (percentage of positively stained cells) was significantly higher in naevus cell naevi than in dysplastic and fibromatous ones.

Relation between two independent DNA-repair pathways in different groups of naevi.

The relation between 2 DNA-repair systems was investigated in 3 groups of naevi (naevus cell naevi, dysplastic naevi, fibromatous naevi) using the correlation coefficient according to Spearman. In the group of naevus cell naevi, only 1 significant correlation between MSH2 and GADD34 expression was found. In the group of dysplastic naevi, 9 significant and highly significant correlations between GADD genes and mismatch repair genes were found. In the group of fibromatous naevi, MLH1 correlated significantly with GADD45 and highly significant with GADD34 expression. Different correlations in naevi groups investigated show the different functional connections between the genes of DNA repair.

Growth arrest DNA damage gene expression in naevi.

Thirty-one naevus cell naevi, 30 dysplastic naevi and 12 fibromatous naevi were stained for the presence of p53 and Growth Arrest DNA Damage genes. All naevus cell naevi and fibromatous naevi were highly positive for GADD genes and negative for p53. Dysplastic naevi had significantly lower GADD34 and GADD153 expression as well as higher p53 expression in relation to the other naevi groups. The absence or decrease of GADD genes expression in naevus may indicate a potential malignant transformation.

Bcl2 and Bax expression in naevi and melanomas and their relation to ploidy status and proliferation.

Twenty-five naevi, 53 primary melanomas, 36 melanoma metastases were stained immunohistochemically for the presence of Bcl2, Bax and Ki-67 antigen in order to define the relation between apoptosis regulators and proliferative activity. Additionally, ploidy status and S-phase were measured. Bax demonstrated a tendency to increase and Bcl2 was decreasing along with melanoma progression. In the group of euploid cases Bcl2 showed a strong significant correlation with Bax expression (p = 0.0001) and both Bcl2 and Bax correlated with Ki-67 expression and S-phase. In the group of aneuploid cases only the correlation Bcl2-Ki-67 was preserved. Others did not reach the level of statistical significance.

Different gene expression of MDM2, GAGE-1, -2 and FHIT in hepatocellular carcinoma and focal nodular hyperplasia.

Overexpression and/or mutations of oncogenes, tumour suppressor genes and tumour rejection genes have been observed in several human malignancies. Their analyses might be of diagnostic importance. Therefore, malignant hepatocytes derived from hepatocellular carcinoma (HCC) tissue as well as non-malignant hepatocytes derived from focal nodular hyperplasia (FNH) were studied. Samples containing normal human hepatocytes (HC) served as controls. Cellular material was obtained by fine-needle aspiration biopsy guided by ultrasound. Cells were analysed for expression and mutation of the oncogene MDM2, the genes GAGE-1, -2 coding for tumour-associated antigens and the candidate tumour suppressor gene FHIT. Different patterns of non-mutant FHIT transcripts including precise deletion of exons were found in 7/10 HCC, 2/10 FNH and 2/10 HC. However, expression of non-mutant GAGE-1, -2 RNA was demonstrated exclusively in 6/10 HCC samples. Further genetic features specific of HCC were point mutations in a zinc-finger motif of MDM2 (3/10 HCC samples). Neither GAGE-1, -2 expression nor MDM2 mutations were observed in the FNH samples, or in normal hepatocytes. Our findings suggest that occurrence of variable FHIT transcripts is not restricted to hepatic malignant tumours. In contrast, MDM2 mutations and GAGE-1, -2 expression were associated with HCC specimens. Therefore, the RT-PCR assays for GAGE-1, -2 and MDM2 might be useful adjuncts in cytodiagnosis of liver neoplasms.

How can one explain aneuploidy status in fibromatous and lipomatous naevus cell naevus?

34 lightly fibromatous, 23 heavily fibromatous, 5 lipomatous and 10 naevus cell naevi were stained with Feulgen kit in order to evaluate their ploidy status with CAS 200 image analyzer. 26/34 lightly fibromatous, 18/23 heavily fibromatous, and 5/5 lipomatous naevi were either suspicious for aneuploidy (Auer III) or clearly aneuploid (Auer IV). In contrast all 10/10 naevus cell naevi were euploid. Proliferation (S-phase) was not increased in naevi fibromatously and lipomatously changed. The mechanisms leading to aneuploidy are discussed.