Loss of p53 gene mutation after irradiation is associated with increased aggressiveness in recurring head and neck cancer.

The p53 gene plays a pivotal role in the control of a checkpoint during G1 and in the apoptotic program. It has been postulated that alterations of p53 may influence radio-sensitivity and prognosis in several malignancies. We studied the p53 gene status of 35 consecutive head and neck cancer patients who failed primary radiotherapy (RT) in preirradiated and postirradiated tumor samples using DNA single-strand conformational polymorphism analysis. Sixteen of 35 (46%) preirradiated samples presented with band shifts suggestive of point mutations in one or two exons. Eleven of these tumors (69%) showed the same shift even in the postirradiated samples. Exons 5 and 8 were prevalently affected in this group. Five tumors (31%) lost the mutation following RT. The missed mutations clustered in exon 7. All mutations were confirmed by sequencing. Actuarial analysis demonstrated increased survival in patients with tumors bearing a p53 gene mutation in both preirradiated and postirradiated samples (P = 0.05 and P = 0.01, respectively). We also found that loss of p53 gene mutation in postirradiated cancers is associated with a significantly shorter disease-free interval (P < 0.02) and a worse prognosis (P < 0.05). A possible explanation in such cases is clonal selection by RT of more aggressive and radioresistant cell subpopulations, which are wild-type for the p53 gene. Taken together, our data suggest that not only p53 gene status but also the pattern of mutations could modulate the response of tumor cell to RT in vivo.

Immunohistochemical vs molecular biology methods. Complementary techniques for effective screening of p53 alterations in head and neck cancer.

The purpose of this study was to correlate p53 gene alterations and their expression in 85 head and neck squamous cell carcinomas. Genomic p53 was amplified with the polymerase chain reaction (PCR) from formalin-fixed, paraffin-embedded tissues. Exons 5 through 8 were screened for mutations by means of non-isotopic single-strand conformation polymorphism (SSCP) analysis. p53 expression was detected by means of immunohistochemistry (IHC) with the p53 monoclonal antibody DO-7. Twenty-three lesions (27%) showed both SSCP variants and DO-7 immunostaining, whereas 37 (44%) demonstrated both SSCP normal patterns and negative staining. Twenty-five lesions (29%) were discordant, including 12 IHC-positive (14%) and 13 SSCP-positive (15%) lesions. However, discordant IHC-negative, SSCP-positive lesions could have been easily interpreted after sequencing of the abnormal samples. Had these been screened with IHC only, all nonsense or frameshift p53 mutations would have been missed. IHC-positive, SSCP-negative lesions were interpreted in light of current models of p53 immunodetection. Had these been screened with SSCP or sequencing only, a sizeable number of tumors expressing p53 protein abnormalities would have been undetected. Therefore, simultaneous use of both methods increases the number of p53 abnormalities detected, and is warranted.

The evolution of the histidine biosynthetic genes in prokaryotes: a common ancestor for the hisA and hisF genes.

The hisA and hisF genes belong to the histidine operon that has been extensively studied in the enterobacteria Escherichia coli and Salmonella typhimurium where the hisA gene codes for the phosphoribosyl-5-amino-1-phosphoribosyl-4-imidazolecarboxamide isomerase (EC 5.3.1.16) catalyzing the fourth step of the histidine biosynthetic pathway, and the hisF gene codes for a cyclase catalyzing the sixth reaction. Comparative analysis of nucleotide and predicted amino acid sequence of hisA and hisF genes in different microorganisms showed extensive sequence homology (43% considering similar amino acids), suggesting that the two genes arose from an ancestral gene by duplication and subsequent evolutionary divergence. A more detailed analysis, including mutual information, revealed an internal duplication both in hisA and hisF genes in each of the considered microorganisms. We propose that the hisA and hisF have originated from the duplication of a smaller ancestral gene corresponding to half the size of the actual genes followed by rapid evolutionary divergence. The involvement of gene elongation, gene duplication, and gene fusion in the evolution of the histidine biosynthetic genes is also discussed.

Genotype-related fingerprints from HLA-DPB1 exon 2 low-stringency PCR.

Techniques based on the formation of heteroduplexes between relevant heterologous amplified HLA loci have proved to be simple and cost-effective screening methods for the detection of DNA sequence diversity. However, the banding patterns produced may not be as complex as required. We used the original procedure of Pena et al. (Proceedings of the National Academy of Sciences USA 91, 1946-1949, 1994) to generate fingerprints from a specific, polymorphic PCR product. HLA-DPB1 exon 2 was amplified, recovered from agarose gel, and used as a template for subsequent low-stringency (30 degrees C) amplification cycles (LS-PCR) in the presence of a single primer. The LS-PCR products were run on 8% PAGE and silver-stained. In total, 22 subjects were characterized by this method. The issues of the reproducibility and specificity of the patterns obtained were addressed by comparing fingerprints from individuals with the same genotype. The results showed that LS-PCR was robust. A further step was the evaluation of the diversity that can be generated, i.e. the sensitivity of the method. Genotype-related fingerprints were produced, and differences as small as a single nucleotide in heterozygous samples could be detected. We then demonstrated the usefulness of LS-PCR in the evaluation of donor/recipient pairs. We believe that LS-PCR may be a valuable adjunct to the battery of tests aimed at the verification of HLA matching before unrelated bone marrow transplantation. We suggest that it could be used to speed up the search process when several candidate donors are retrieved from registries before embarking on SSOP typing or sequencing.

Cumulative prognostic value of p53 mutations and bcl-2 protein expression in head-and-neck cancer treated by radiotherapy.

We investigated the prognostic significance of p53-gene mutation (exon 5-9) and bcl-2-protein expression in primary squamous-cell carcinoma of the head and neck (HNSCC) treated by curative radiotherapy (RT). Primary squamous-cell carcinomas for analysis were obtained from 85 consecutive head-and-neck-cancer patients, with complete follow-up data. We detected bcl-2 protein in 24% (20/85) of HNSCC studied; 38 (45%) of the 85 tumours had cells bearing p53 mutations. A strong association was observed between tobacco exposure and bcl-2-protein expression (p = 0.003), an association also evident in those patients who had a p53-mutated carcinoma (p = 0.049). Moreover, we found that most of the bcl-2-positive cancers (70%) were also mutated in the p53 gene (p = 0.010). In univariate and in multivariate analyses, the simultaneous detection of bcl-2 expression and a p53-gene mutation in a tumour biopsy specimen was associated with greater risk of locoregional failure (p = 0.002 and 0.001 respectively) and worse survival (p = 0. 045 and 0.033) within 5 years in HNSCC patients treated by RT. The present study shows a cumulative prognostic value of simultaneous detection of bcl-2 over-expression and p53-gene aberration in some primary HNSCC treated with conventional RT, and provides further evidence for cross-talk between p53 and bcl-2, suggesting that these genes are important determinants of radiation-induced apoptosis, thereby modulating resistance to RT. Int. J. Cancer (Pred. Oncol.) 84:573-579, 1999.

Potential biomarkers in predicting progression of epithelial hyperplastic lesions of the larynx.

Factors contributing to malignant transformation of laryngeal pre-neoplastic lesions remain largely unknown. Potential etiologic factors may be related to a genetically controlled sensitivity to environmental carcinogens. In this study, we investigated bleomycin-induced chromosome fragility in 15 patients with laryngeal keratoses who experienced a malignant transformation of pre-neoplastic lesions during follow-up, as compared with chromosome fragility in 15 historical controls with no progression of laryngeal keratoses during a 10-year follow-up, in a match-paired analysis. Chromosomal analysis demonstrated a higher sensitivity to clastogens in patients with malignant progression of laryngeal pre-neoplastic lesions than that of control patients with no evolution of their original laryngeal keratoses (p < 0.01). Furthermore, in the attempt to identify possible prognostic markers we studied proliferative activity (MIB-1 expression) and p53 gene aberration in biopsy samples from non-invasive and invasive laryngeal lesions in both groups. p53 immunostaining was observed in 10/15 (66.7%) of pre-neoplastic lesions and in 11/15 (73.3%) of metachronous laryngeal cancers. No differences in terms of p53 expression were noted between transformed and not-transformed lesions. Mutations at p53 gene were observed in 3/15 (20%) of pre-invasive biopsies and in 4/5 (80%) of the laryngeal cancers analyzed. Our data suggest that p53 alteration is an early event in the genesis of a subset of laryngeal carcinomas and that there is no conclusive data about the possible clonal development of metachronous laryngeal carcinoma from a p53 mutated pre-invasive disease in the same patient. MIB-1 expression was found to progressively increase with degree of epithelial hyperplasia and dysplasia in both transformed (p = 0.007) and not-transformed (p < 0.1) lesions. Surprisingly, pre-invasive lesions with tumor evolution showed a lower proliferative activity when compared with laryngeal lesions without malignant transformation (p = 0.013). These data suggests that subjects with pre-neoplastic laryngeal lesion showing an increased susceptibility to carcinogens and with less proliferative disease could be at a higher risk for development of laryngeal carcinoma.

Epstein-Barr virus infection and P53 expression in HIV-related oral large B cell lymphoma.

BACKGROUND: Head and neck non-Hodgkin's lymphomas in HIV positive patients are highly related with Epstein-Barr virus (EBV) infection. In general, viral agents can alter p53 protein levels by enhancing degradation of cellular p53 or by increasing its half-life by viral protein-p53 interaction. Moreover, it has been reported that modifications of p53 gene can modulate tumor cells' response to radio- and chemotherapy. METHODS: To assess a possible role of EBV infection, p53 protein deregulation, and p53 gene alterations in exons 5 to 8, we have studied six cases of HIV-related primary oral large B-cell lymphoma. We used in situ hybridization (ISH) for EBV-DNA and EBV-encoded nuclear RNA-1 (EBER-1), immunohistochemistry (IHC) for EBV latent membrane protein -1 (LMP-1) and p53 proteins expression, and single strand conformational polymorphism (SSCP) analysis to screen p53 gene mutations in exons 5 to 8. RESULTS: The EBV-DNA was present in all specimens, according to conventional DNA-ISH. No evidence for EBER-1 was found by ISH. The presence of EBV-DNA was correlated with the LMP-1 expression in all but one case. Moreover, p53 protein expression was negative in three cases and strongly positive in the others. However, mutational analysis of p53 gene in exons 5-8 showed no alteration. CONCLUSIONS: Our data may suggest that both EBV infection and LMP-1 expression may cause p53 loss of function even in the absence of p53 gene mutations, as assessed by SSCP. We speculate that the presence of EBV-infection and p53 protein deregulation may be responsible for radio- and chemotherapy resistance, by influencing apoptosis of cancer cells.

A method for point mutation analysis that links SSCP and dye primer fluorescent sequencing.

A method is presented for mutation detection directly from single-strand conformational polymorphism (SSCP) variants. This approach is based on: (i) amplification of the exons to be analysed by SSCP using the forward primer with an eight-base tail to form a universal SSCP cassette; (ii) excision from the gel of the shifted silver-stained bands; (iii) reamplification of the eluted DNAs using, as the forward primer, a 26-base universal adaptor primer corresponding to the 18-base-21M13 sequence plus the eight nucleotides of the universal SSCP cassette; and (iv) direct sequencing of the purified products using the standard-21M13 fluorescent primer. This procedure presents several advantages including the avoidance of a cloning step which leads to significant time reduction, while maintaining comparable accuracy at relatively low costs. In conclusion, the presence of the universal SSCP cassette and subsequent reamplification with the same adaptor primer for direct sequencing makes the method universal for scanning and identification of gene alterations.

Mutation and polymorphism analysis of the human homogentisate 1, 2-dioxygenase gene in alkaptonuria patients.

Alkaptonuria (AKU), a rare hereditary disorder of phenylalanine and tyrosine catabolism, was the first disease to be interpreted as an inborn error of metabolism. AKU patients are deficient for homogentisate 1,2 dioxygenase (HGO); this deficiency causes homogentisic aciduria, ochronosis, and arthritis. We cloned the human HGO gene and characterized two loss-of-function mutations, P230S and V300G, in the HGO gene in AKU patients. Here we report haplotype and mutational analysis of the HGO gene in 29 novel AKU chromosomes. We identified 12 novel mutations: 8 (E42A, W97G, D153G, S189I, I216T, R225H, F227S, and M368V) missense mutations that result in amino acid substitutions at positions conserved in HGO in different species, 1 (F10fs) frameshift mutation, 2 intronic mutations (IVS9-56G-->A, IVS9-17G-->A), and 1 splice-site mutation (IVS5+1G-->T). We also report characterization of five polymorphic sites in HGO and describe the haplotypic associations of alleles at these sites in normal and AKU chromosomes. One of these sites, HGO-3, is a variable dinucleotide repeat; IVS2+35T/A, IVS5+25T/C, and IVS6+46C/A are intronic sites at which single nucleotide substitutions (dimorphisms) have been detected; and c407T/A is a relatively frequent nucleotide substitution in the coding sequence, exon 4, resulting in an amino acid change (H80Q). These data provide insight into the origin and evolution of the various AKU alleles.

Canine visceral leishmaniasis: a remarkable histopathological picture of one asymptomatic animal reported from Belo Horizonte, Minas Gerais, Brazil

A remarkable histopathological picture of one asymptomatic dog naturally infected with Leishmania infantum (syn. chagasi) has been presented. Intracellular parasites were ease found in macrophages of all exanimated organs, especially in skin. Embedded paraffin tissues of liver, spleen, axillary and popliteal lymph nodes, and skin (ear, muzzle and abdomen) were stained by hematoxylin and eosin and by immunocytochemical reaction (streptoavidin-peroxidase method) to detect parasites. All organs showed an intense parasitism associated to severe pathological changes. All lymph nodes had conspicuous histological architecture alterations. Lymphocytes were replaced by macrophages stuffed with an intense number of amastigotes forms of Leishmania. The lymphoid nodules (without germinal centers) and the mantle zones in the cortex that surround the follicles were markedly attenuated. Livers showed small intralobular granulomas composed by macrophages loaded with amastigotes. Spleens had an intense depression of the white pulp whereas the lymphocytes were replaced by parasitized macrophages. All fragments of different anatomical region of skin (ear, muzzle and abdomen) showed a diffuse chronic inflammation. The cellular exudate was composed by macrophages, plasmocytes and lymphocytes. Macrophages loaded with amastigotes were ease found in all tissue fragments, but more intense in ear and muzzle. Thus, this fact enhances the importance of asymptomatic dogs in the epidemiology of visceral leishmaniasis.

Relata-se um quadro histológico caracterizado por lesões acentuadas em tecidos de um cão assintomático naturalmente infectado por Leishmania infantum (sin. chagasi). Cortes parafinados de fígado, baço, linfonodos (cervical, axilar e poplíteo) e pele (orelha, espelho nasal e abdome) foram corados pela técnica de hematoxilina-eosina e pela técnica imunoistoquímica de estreptoavidina-peroxidase para detecção de formas amastigotas de Leishmania. Os linfonodos apresentaram profundas alterações estruturais. Em todos observou-se depleção linfocitária, principalmente da córtex, com substituição dos linfócitos por macrófagos abarrotados de formas amastigotas de Leishmania. No fígado, observou-se a presença de pequenos granulomas intralobulares compostos por macrófagos intensamente parasitados, plasmócitos e raros linfócitos. No baço, a alteração marcante foi a depressão da polpa branca. Os folículos linfóides foram substituídos por macrófagos intensamente parasitados com as formas amastigotas de Leishmania. Fragmentos de pele de orelha, espelho nasal e abdome apresentaram reação inflamatória crônica e difusa com exsudato celular composto por macrófagos, plasmócitos e linfócitos. Parasitos foram detectados em todos os tecidos estudados e mais numerosos na pele da orelha e focinho. Os achados mostram a importância de cães assintomáticos na epidemiologia da leishmaniose visceral.