Ricardo Santiago Gomez

PTCH Gene Mutations in Odontogenic Keratocysts

An odontogenic keratocyst (OKC) is a benign cystic lesion of the jaws that occurs sporadically or in association with nevoid basal cell carcinoma syndrome (NBCCS). Recently, the gene for NBCCS was cloned and shown to be the human homologue of the Drosophila segment polarity gene Patched (PTCH), a tumor suppressor gene. The PTCH gene encodes a transmembrane protein that acts in opposition to the Hedgehog signaling protein, controlling cell fates, patterning, and growth in numerous tissues, including tooth. We investigated three cases of sporadic odontogenic keratocysts and three other cases associated with NBCCS, looking for mutations of the PTCH gene. Non-radioactive single-strand conformational polymorphism and direct sequencing of PCR products revealed a deletion of 5 base pairs (bp) in exon 3 (518delAAGCG) in one sporadic cyst as well as mutations in two cysts associated with NBCCS, a nonsense (C2760A) and a missense (G3499A) alteration. This report is the first to describe a somatic mutation of PTCH in sporadic odontogenic keratocysts as well as two novel mutations in cysts associated with NBCCS, indicating a similar pathogenesis in a subset of sporadic keratocysts.

Interleukin‐6 expression and gene polymorphism are associated with severity of periodontal disease in a sample of Brazilian individuals

Interleukin (IL)‐6 is an inflammatory mediator involved in bone resorption. G/C polymorphism at position −174 of the IL‐6 gene has been reported to influence IL‐6 expression, with the G allele associated with higher expression levels. The aims of this study were to investigate the expression of IL‐6 as well as the incidence of IL‐6 (−174) gene polymorphism and their correlation to the severity of periodontitis in Brazilians. Peripheral blood mononuclear cells were collected from 12 non‐smoker individuals with periodontitis for evaluation of IL‐6 expression using flow cytometry. We observed a positive correlation between the mean clinical attachment loss and intensity of expression of IL‐6, in which the greater the attachment loss, the higher the expression of IL‐6 (P = 0·007, R2 = 0·52). Also, patients with severe periodontitis displayed a higher intensity of IL‐6 expression compared to moderate periodontitis (P = 0·04). To determine the occurrence of IL‐6 gene polymorphism, DNA was obtained from oral swabs of 209 Brazilian individuals with and without periodontitis. Polymerase chain reaction, restriction endonuclease digestion and electrophoresis were performed, allowing for detection of the IL‐6 (−174) polymorphism. We observed that non‐smokers with moderate periodontitis (P = 0·05) and control (P = 0·04) groups displayed a higher incidence of the G– genotype when compared to severe periodontitis. This suggests that the G– genotype may represent a protective role in severity of periodontitis. Thus, the increased expression of IL‐6 and IL‐6 (−174) polymorphism are associated with periodontal disease severity in Brazilian individuals.

Relationship between the use of full dentures and mucosal alterations among elderly Brazilians

The objective of the present study was to evaluate the prevalence of oral mucosal lesions associated with the use of full dentures (FD) among non-institutionalized individuals of 60 or more years of age in a rural Brazilian population. The sample consisted of 344 individuals aged 60 or more from two rural communities of Brazil. Of this total, 146 were FD users and 198 FD, non-users. Angular cheilitis, denture stomatitis and inflammatory fibrous hyperplasia were statistically associated with prosthesis use. Hygiene and integrity of the prosthesis were related to the presence of oral lesions. While inflammatory fibrous hyperplasia was positively related to FD integrity, denture stomatitis was associated with time of use, hygiene status and integrity of FD. The results indicate the need for oral health care programmes for the elderly and show a relationship between time of use, quality and hygiene of oral prostheses with the presence of mucosal lesions.

Methylation of P16, P21, P27, RB1 and P53 genes in odontogenic keratocysts

BACKGROUND Odontogenic keratocyst (OKC) is a benign neoplasm with an aggressive clinical behavior and a high recurrence rate. Although epigenetic alterations have been reported in different tumors, these events were not investigated in OKC yet. The aim of this study was to investigate the presence of methylation in P16, P21, P27, P53 and RB1 genes in OKC tumors. METHODS Methylation-specific polymerase chain reaction (MSP) was used to evaluate the presence of methylation in 10 samples of OKCs, 10 samples of dental follicles and six samples of normal mucosa. RESULTS The methylation status of the P16 gene was similar among the three groups. In P21 gene, 30% of OKCs were methylated while no methylation could be detected in the other groups. High frequency of P27 methylation (90%) was observed in dental follicles, however, some OKC lesions (10%) and normal mucosa samples (33%) were also methylated. Concerning the RB1 gene, positive results were detected only in dental follicles (40%). No positive result was observed considering P53 gene. CONCLUSIONS Our data show methylation of the promoter of P21 gene in OKCs. In addition, methylation of the P27 and RB1 genes are commonly found in dental follicles. Further studies are necessary to determine the functional relevance of these alterations.

REVIEW ARTICLE: Current concepts of ameloblastoma pathogenesis

Ameloblastoma is a locally destructive and invasive tumour that can recur despite adequate surgical removal. Molecular studies have offered interesting findings regarding ameloblastoma pathogenesis. In the present review, the following topics are discussed regarding its molecular nature: clonality, cell cycle proliferation, apoptosis, tumour suppressor genes, ameloblastin and other enamel matrix proteins, osteoclastic mechanism and matrix metalloproteinases and other signalling molecules. It is clear from the literature reviewed that translational studies are necessary to identify prognostic markers of ameloblastoma behaviour and to establish new diagnostic tools to the differential diagnosis of unicystic from multicystic ameloblastoma. Finally, molecular biology studies are also important to develop more effective alternative approaches to the treatment of this aggressive odontogenic tumour.

Review of the molecular pathogenesis of the odontogenic keratocyst

The odontogenic keratocyst (keratocystic odontogenic tumour) (OKC) is one of the most prevalent odontogenic tumours. Since its initial description, a number of studies have focused on different aspects of this lesion, attempting to explain its distinctive biological behaviour. In this review the authors address the main genetic and epigenetic alterations reported on this tumour. Although most of the knowledge on this field is not being used in the clinical practice, some perspectives of translational studies are discussed.

Analysis of 724 cases of primary head and neck squamous cell carcinoma (HNSCC) with a focus on young patients and p53 immunolocalization

This study evaluated 724 primary head and neck squamous cell carcinoma (HNSCC) in young and old patients, with regard to clinical profile and immunohistochemical expression of p53 protein. Associations among age, epidemiological and clinicopathological parameters, and survival analysis were evaluated. HNSCC in young people occurred in 14.5% (median age 40.7years; male-to-female ratio 5.9:1). A statistical association was demonstrated between age and family history of cancer, and between age and anatomical site. Among older patients, a higher presence of disease was noted in posterior sites. Expression of p53 was found in 71.7% of the samples and a higher expression was noted in lesions of young patients. Survival analysis showed that the age parameter is not a reliable prognostic factor for HNSCC. Among young patients, cervical metastasis was associated with worse survival. The presence of a family history of cancer in young patients could indicate genetic susceptibility and molecular disturbances in the p53 pathway in HNSCC of young and older patients seem to be distinct.

Oral myiasis by screwworm Cochliomyia hominivorax.

We report a rare case of periodontal myiasis by New World screwworm Cochliomyia hominivorax, an obligatory larval parasite, in a 66-year-old woman. The myiasis occurred in the anterior upper jaw associated with a pre-existent generalised periodontitis. About 40 larvae were removed from the lesion. One week later the periodontal tissues were healing normally and the patient was referred to a periodontist. As all of the larvae were in the last stage, they were probably deposited 5-7 days before.

Characterization of the tumor suppressor gene WWOX in primary human oral squamous cell carcinomas

Oral squamous cell carcinoma (OSCC) is the most common malignant neoplasm of the oral cavity, representing ˜90% of all oral carcinomas and accounting for 3–5% of all malignancies. The WWOX gene (WW‐domain containing oxidoreductase) is a candidate tumor suppressor gene located at 16q23.3–24.1, spanning the second most common fragile site, FRA16D. In this report, the role of the WWOX gene was investigated in 20 tumors and 10 normal oral mucosas, and we demonstrated an altered WWOX gene in 50% (10/20) of OSCCs. Using nested RT‐PCR, mRNA transcription was altered in 35% of the tumors, with the complete absence of transcripts in 2 samples as well as absence of exons 6–8 (2 tumors), exon 7 (1 tumor), exon 7 and exon 6–8 (1 tumor) and partial loss of exons 8 and 9 (1 tumor). To determine if the aberrant transcripts were translated, Western blots were performed in all samples; however, only the normal protein was detected. By immunohistochemistry, a reduction in Wwox protein expression was observed, affecting 40% of the tumors when compared with normal mucosa. In addition, a novel somatic mutation (S329F) was found. The presence of alterations in mRNA transcription correlated with the reduced expression of Wwox protein in the tumors. These results show that the WWOX gene is frequently altered in OSCC and may contribute to the carcinogenesis processes in oral cancer.

Familial hyperparathyroidism: surgical outcome after 30 years of follow-up in three families with germline HRPT2 mutations

Background Familial forms of hyperparathyroidism are responsible for approximately 10% of the cases of primary hyperparathyroidism, and their management is different from the sporadic forms. Our objective was to study the gene sequence and expression of HRPT2 and clinical outcome regarding recurrence or persistence rates in three Brazilian kindreds with familial hyperparathyroidism after up to 30 years of follow-up. Methods Clinical and biochemical data, direct sequencing of germline DNA of the HRPT2 gene, and analysis of parafibromin expression (HRPT2 gene product) using RT-PCR and immunohistochemistry of resected parathyroid neoplasms were performed. Results Affected members of kindred A were found to carry a novel, germline, nonsense mutation in exon 1 (c.96G>A; W32X) of HRPT2. Six of seven patients who have undergone less than total parathyroidectomy recurred after up to 30 years of follow-up. An unrelated affected patient from kindred B had a germline mutation in exon 7 (c.686delGAGT), and the disease recurred with several pulmonary metastases after 5 years follow-up. The affected member of kindred C also had a previously described mutation in exon 7 (c.679delAG) and the disease recurred after 10 years of follow-up. All parathyroid neoplasms from these families had diffuse loss of expression by immunohistochemistry. Conclusions An unacceptable recurrence/persistence rate (80%) associated with increasingly difficult re-operations and risk of parathyroid carcinoma in the setting of germline mutations of HRPT2 gene with familial hyperparathyroidism suggest that a more aggressive operative approach should be undertaken in these patients. Parafibromin immunohistochemistry may serve as a cost-effective screen for HRPT2-related aggressive parathyroid disease.