Tc-99m hydroxymethylene diphosphonate scintigraphy, computed tomography, and magnetic resonance imaging of osteonecrosis in the mandible: Osteoradionecrosis versus medication-related osteonecrosis of the jaw.

PURPOSE: To present characteristic findings of Tc-99m hydroxymethylene diphosphonate (HMDP) scintigraphy, computed tomography (CT), and magnetic resonance (MR) imaging for osteonecrosis in the mandible, especially osteoradionecrosis (ORN) and medication-related osteonecrosis of the jaw (MRONJ). MATERIALS AND METHODS: Thirteen patients with MRONJ and 7 patients with ORN in the mandible underwent Tc-99m HMDP scintigraphy, CT, and MR imaging (T1-weighted images [T1WI], T2-weighted images [T2WI], short inversion time inversion recovery images [STIR]), diffusion-weighted images [DWI], and apparent diffusion coefficient [ADC] mapping). The associations of scintigraphy, CT, and MR imaging findings with MRONJ and ORN were analyzed using the chi-square test with the Pearson exact test. RESULTS: Thirteen patients with MRONJ and 7 patients with ORN in the mandible showed low signal intensity on T1WI and ADC mapping, high signal intensity on STIR and DWI, and increased uptake on scintigraphy. Periosteal bone proliferation on CT was observed in 69.2% of patients with MRONJ (9 of 13) versus 14.3% of patients with ORN (1 of 7) (P=0.019). CONCLUSION: This study presented characteristic imaging findings of MRONJ and ORN on scintigraphy, CT, and MR imaging. Our results suggest that CT can be effective for detecting MRONJ and ORN.

Osteosarcoma of the Mandible: a Case Report with CT, MRI and Scintigraphy.

Osteosarcomas are especially rare in the mandible and maxilla, representing 1.6% of all bony malignant tumours. In this article, we described a case of osteosarcoma of the mandible. Computed tomography (CT) image showed a well-circumscribed homogeneous mass, with nonhomogeneous contrast enhancement. T1-weighted magnetic resonance imaging (MR) image showed intermediate signal intensity on, and after administration the lesion showed signal intensity lower than muscle. T2-weighted MR image showed heterogeneous high signal intensity. Bone scintigraphy revealed monostatic involvement of the mandible with a homogenous intense uptake pattern. Ga-67 citrate scintigraphy revealed significantly increased uptake. Histopathological examination confirmed the diagnosis of osteosarcoma.

A Rare Case of Malignant Melanoma of the Mandible: CT and MRI Findings.

Malignant melanoma of the mandibular gingiva is extremely rare. It is a malignant tumour of melanocytes or their precursor cells, and often misinterpreted as a benign pigmented process. A few reports have described computed tomography (CT) and magnetic resonance imaging (MRI) findings of malignant melanoma in the oral cavity. We report a rare case of malignant melanoma of the mandible and the related CT and MRI findings. Soft tissue algorithm contrast-enhanced CT showed an expansile mass and irregular destruction of alveolar bone in the right side of the mandibular molar area. MR images showed an enhancing mass and the tumour had a low to intermediate signal intensity and a high-signal intensity. Soft tissue algorithm contrast-enhanced CT and MR images showed lymphadenopathy involving the submandibular lymph nodes. Histopathological examination confirmed the diagnosis of malignant melanoma.

Characteristic Multimodal Imaging of Medication-Related Osteonecrosis of the Jaw: Comparison Between Oral and Parenteral Routes of Medication Administration.

BACKGROUND: To assess multimodal imaging features of medication-related osteonecrosis of the jaw (MRONJ) and to analyze the differences between oral and parenteral routes of medication administration. We retrospectively reviewed panoramic radiographs, CT, MRI, and bone scintigraphy of patients with MRONJ. MATERIAL/METHODS: A retrospective study was conducted in 16 patients with MRONJ who underwent panoramic radiography, CT, MRI, and bone scintigraphy. Statistical analysis for the comparison between routes of medication administration and multimodal imaging features was performed with the Pearson's χ2 test. RESULTS: The percentage of cases with sequestrum separation was 25.0% (4/16 cases) on panoramic radiography and 81.3% (13/16 cases) on CT. The percentage of cases with periosteal bone proliferation on CT was 41.7% (5/12 cases) in the oral route of administration vs. 100% (4/4 cases) in the parenteral route of administration (p=0.042). The percentage of cases with spread of soft tissue inflammation to buccal and other spaces on CT and MRI was 33.3% (4/12 cases) in the oral route of administration vs. 100% (4/4 cases) in the parenteral route of administration (p=0.021). CONCLUSIONS: The sequestrum separation on panoramic radiography in patients with MRONJ was unclear in comparison to CT. Furthermore, characteristic CT findings of patients with MRONJ in the parenteral administration group were periosteal bone proliferation and spread of soft tissue inflammation to buccal and other spaces.

Diffusion-Weighted Imaging in the Oral and Maxillofacial Region: Usefulness of Apparent Diffusion Coefficient Maps and Maximum Intensity Projection for Characterization of Normal Structures and Lesions.

BACKGROUND: The aim of this study was to investigate diffusion-weighted imaging (DWI) in the oral and maxillofacial region, with a special focus on the usefulness of apparent diffusion coefficient (ADC) maps and maximum intensity projection (MIP) for characterization of normal structures and lesions. MATERIAL/METHODS: Thirty-five patients who underwent magnetic resonance imaging (MRI) for diagnosis of oral and maxillofacial lesions were included in this prospective study. DWI was performed on a 1.5 T unit, with b factor of 0 and 800 s/mm2; moreover, ADC maps were generated. ADC values were measured for normal structures, odontogenic infections, squamous cell carcinomas (SCC), and hemangiomas. RESULTS: As regards the normal structures, the mean ADC value of the cerebrospinal fluid (3.65±0.60×10-3 mm2/s) in the upper neck area was higher than that of the spinal cord (0.74±0.15×10-3 mm2/s, P=0.000), lymph nodes (0.87±0.17×10-3 mm2/s, P=0.000), and Waldeyer's ring (0.92±0.29×10-3 mm2/s, P=0.000). The mean ADC value of hemangiomas (1.52±0.31×10-3 mm2/s) was higher than that of odontogenic infections (0.85±0.36×10-3 mm2/s, P=0.034) and SCC (1.38±0.22×10-3 mm2/s, P=0.840). Furthermore, MIP (DWI) showed the normal structures and lesions in the oral and maxillofacial region in an improved way. CONCLUSIONS: DWI, ADC maps, and MIP can be used to characterize and differentiate normal structures and lesions in the oral and maxillofacial region.

Structural Variations in Parotid Glands Induced by Radiation Therapy in Patients with Oral Carcinoma Observed on Contrast-Enhanced Computed Tomography.

BACKGROUND: Xerostomia is one of the commonest radiation-induced complications in patients with head and neck carcinoma. The aim of this study was to assess structural variations in parotid glands induced by radiation therapy in patients with oral carcinoma with contras-enhanced computed tomography (CECT). MATERIAL/METHODS: A retrospective study was performed in 41 patients with oral carcinoma who underwent CECT for head and neck malignancies before and after radiotherapy. We analyzed the relationship between parotid density variations, parotid volume change, as seen on CECT, and the mean radiation dose applied to the parotid glands in patients with oral carcinoma immediately after radiotherapy, and 2 and 3 years later. RESULTS: Immediately after radiotherapy, high-density changes on contrast-enhanced CT were observed in 70.5% of the irradiated parotids. Low-density changes due to fat degeneration were seen in 46.2% and 72.2% of the irradiated parotids 2 and 3 years after radiotherapy, respectively. The mean dose applied to the parotids with the low-density changes and without such changes 3 years after radiotherapy was 46.0 Gy and 27.7 Gy, respectively (p=0.049). Furthermore, parotid shrinkage was observed in 63.6% of the irradiated parotids. CONCLUSIONS: This study suggests that the structural variations in parotid glands induced by radiotherapy included high-density changes that were observed immediately after radiotherapy and low-density changes that were seen at late follow-up. This study should be useful for clinicians in the assessment of radiation-induced injuries in the parotids with respect to early prediction of xerostomia.

Abnormal DNA end-joining activity in human head and neck cancer.

In human cells, DNA double-strand breaks (DSBs) are repaired primarily by the DNA end-joining (EJ) process and thus, abnormal DNA EJ activities lead to an accumulation of mutations and/or aneuploidy, resulting in genetic instability of cells. Since genetic instability is the hallmark of cancer cells, we studied the DNA EJ activities of normal, non-malignant immortalized and malignant human epithelial cells to investigate the association between DNA EJ and carcinogenesis. We found a significant diminution of precise (error-free) DNA EJ activities in non-malignant immortalized human oral keratinocytes (HOK-16B) and human head and neck squamous cell carcinoma (HNSCC) cells compared to that in normal human oral keratinocytes (NHOK). Moreover, abnormal DNA EJ activities were detected exclusively in HOK-16B and HNSCC cells due to microhomology-mediated and non-microhomology-mediated end-joining activities in these cells. These data indicated that aberrant DNA EJ activity may be partly responsible for genetic instability and oncogenic transformation.

Immunohistochemical localization of parathyroid hormone-related protein (PTHrP) and serum PTHrP in normocalcemic patients with oral squamous cell carcinoma.

Cancer cells produce parathyroid hormone-related protein (PTHrP) in the early phase of malignancy development, before hypercalcemia occurs. The relationship between PTHrP and the clinicopathologic features of oral squamous cell carcinoma is poorly understood. We studied 60 patients (43 men, 17 women; mean age, 64.8 +/- 11.2 years) with primary oral squamous cell carcinoma, from whom pretreatment biopsy specimens were obtained. We examined the relationship among immunohistochemical PTHrP expression, serum PTHrP levels, clinical characteristics of the tumor, and histopathologic aspects of the tumor. The mean calcium concentration for the 60 patients was 9.1 +/- 0.4 mg/dl. No patients had laboratory evidence of hypercalcemia before treatment. Six patients had serum levels of C-terminal (C)-PTHrP higher than the normal level of 55.3 pmol/l. There were no significant differences in serum C-PTHrP levels according to TNM stages. Abundant positive immunoreactivity for anti-PTHrP (1-34) antibody was recognized diffusely in the whole cytoplasm of many tumor cells. Anti-PTHrP (38-64) antibody staining tended to localize as small granules in the cytoplasm, especially close to the nuclear periphery. There was no correlation between the serum C-PTHrP concentration and the intensity of either immunostain. The intensity of PTHrP was proportionally related to the degree of differentiation or extent of keratinization (P < 0.05) and the histologic malignancy grade of the tumor (P < 0.05), when using antibody against PTHrP (1-34), but not when using antibody against PTHrP (38-64). Serum C-PTHrP levels did not correlate with the intensity of cellular PTHrP expression and characteristics of the tumor at the initial patient visit. The fragment that includes PTHrP (1-34) may be involved in the differentiation of oral squamous cell carcinoma. The differences between immunoreactivities may have been due to differing tissue malignancies and the use of different antibodies. The results suggest the need for caution when interpreting immunoreactivities of PTHrP in malignancies.

Introduction of human telomerase reverse transcriptase to normal human fibroblasts enhances DNA repair capacity.

PURPOSE: From numerous reports on proteins involved in DNA repair and telomere maintenance that physically associate with human telomerase reverse transcriptase (hTERT), we inferred that hTERT/telomerase might play a role in DNA repair. We investigated this possibility in normal human oral fibroblasts (NHOF) with and without ectopic expression of hTERT/telomerase. EXPERIMENTAL DESIGN: To study the effect of hTERT/telomerase on DNA repair, we examined the mutation frequency rate, host cell reactivation rate, nucleotide excision repair capacity, and DNA end-joining activity of NHOF and NHOF capable of expressing hTERT/telomerase (NHOF-T). NHOF-T was obtained by transfecting NHOF with hTERT plasmid. RESULTS: Compared with parental NHOF and NHOF transfected with empty vector (NHOF-EV), we found that (a) the N-methyl-N'-nitro-N-nitrosoguanidine-induced mutation frequency of an exogenous shuttle vector was reduced in NHOF-T, (b) the host cell reactivation rate of N-methyl-N'-nitro-N-nitrosoguanidine-damaged plasmids was significantly faster in NHOF-T; (c) the nucleotide excision repair of UV-damaged DNA in NHOF-T was faster, and (d) the DNA end-joining capacity in NHOF-T was enhanced. We also found that the above enhanced DNA repair activities in NHOF-T disappeared when the cells lost the capacity to express hTERT/telomerase. CONCLUSIONS: These results indicated that hTERT/telomerase enhances DNA repair activities in NHOF. We hypothesize that hTERT/telomerase accelerates DNA repair by recruiting DNA repair proteins to the damaged DNA sites.

Senescence occurs with hTERT repression and limited telomere shortening in human oral keratinocytes cultured with feeder cells.

We investigated the phenotypic and molecular alterations in normal human oral keratinocytes (NHOK) during in vitro replication in two different culture conditions. The cells were cultured either in chemically defined Keratinocyte Growth Medium (KGM) without feeder layers or in serum-containing flavin-adenine dinucleotide (FAD) medium with feeder layers. Primary NHOK underwent 22 +/- 3 population doublings (PDs) in KGM and 42 +/- 4 PDs in FAD medium, reflecting 52% increase in replication capacity with feeder layers. In both culture conditions, exponentially replicating NHOK demonstrated telomerase activity and expression of human telomerase reverse transcriptase (hTERT) gene. Telomerase activity and hTERT expression were rapidly diminished in senescing NHOK, which exhibited small decrease of telomere length for the remaining limited cellular replications until the complete arrest of cell division. However, telomere length in senescent NHOK was 6.7 +/- 0.5 kilobase pairs (kbps), significantly longer than that (5.12 kbps) of senescent human fibroblasts. The onset of senescence was accompanied with marked induction of p16(INK4A), and this occurred in both culture systems using either KGM or FAD medium. These results indicate that replicative senescence of NHOK is associated with loss of telomerase activity followed by limited telomere shortening.

Telomere shortening does not occur during postmaturational aging in situ in normal human oral fibroblasts.

We investigated whether the telomere length, i.e. mean terminal restriction fragment (TRF) length, decreases during in situ aging in normal human oral fibroblasts (NHOF). For this purpose, NHOF cultures were established from 50 different donors and tested after 14 population doublings (PD) when the cells were replicating exponentially. Telomere-specific Southern blotting and digital quantitation showed that the mean (+/-standard error (S.E.)) TRF length of all tested cultures was 7.72+/-0.17 kbps. The plot of TRF mean length versus donor age showed high variability in individual length with an apparent average decline of -7.8 bp per year of age, which was not statistically significant (r=0.11; P>0.1). These data indicate that telomere shortening does not occur during donor aging in situ, and therefore, is not physiologically relevant for NHOF.

Senescence-associated genes in normal human oral keratinocytes.

The current study was undertaken to identify senescence-associated (SA) genes in cultured normal human oral keratinocytes (NHOK). Primary NHOK were serially subcultured in vitro as dispersed cells in low (0.15 mM) Ca(2+) medium until senescence. The SA genes of NHOK were identified by comparing the expression levels of 3195 human genes between exponentially replicating and senescing cultures. Approximately 5% of the screened genes were upregulated in senescing NHOK by a factor greater than 3 compared with rapidly dividing NHOK culture. Among them, we identified discrete gene groups, i.e., cyclin-dependent kinase inhibitors, G-protein-coupled receptors, apolipoproteins, matrix metalloproteinases, and mitochondrial proteins. To validate the microarray results, we confirmed the enhanced expression of a few selected SA genes, i.e., gpr1, apo-D, apo-E, apo-L, mmp-1, mmp-3, cyb561, cyp1b1, and cyp4b1, by reverse transcription-PCR. These SA genes were upregulated in three independent cultures of NHOK at high population doubling (PD) levels compared with those of low PDs. The enhanced expression of these SA genes was also found in senescing NHOK maintained in 3T3 feeder cell system, as well as in the chemically defined medium containing low Ca(2+). These results indicate that the onset of senescence in NHOK is associated with altered expression of the SA genes, which represent discrete gene groups, independently of the donor variation or culture conditions.

Absence of hamTERT gene expression is associated with promoter hypermethylation in immortal hamster buccal pouch epithelial cells.

This study describes the first example of spontaneously immortalized, telomerase-negative hamster cells which replicated in the absence of telomere shortening. Primary hamster buccal pouch epithelial (HBPE) cells were subcultured for approximately 10 population doublings (PDs) before they ceased to divide. Among the non-replicating HBPE cells, a colony of proliferating cells had appeared. These cells named HBPE-SI (spontaneously immortalized) replicated with a mean doubling time of 27 h for 120 PDs in culture and are still replicating. Surprisingly, telomerase activity and hamTERT (hamster telomerase gene) expression were not detectable in HBPE-SI, although an exogenous hamTERT promoter showed promoter activity in these cells. HBPE-SI cells replicated in the apparent absence of apparent telomere shortening during their entire in vitro culture, indicating telomerase-independent mode of telomere maintenance. Analysis of the hamTERT promoter in HBPE-SI cells revealed hypermethylation. Exposure of the cells to 5-aza-2'-deoxycytidine (5-aza CdR) restored expression of endogenous hamTERT mRNA. These results indicated that HBPE-SI cells maintained their telomere length in the absence of telomerase activity, and that hamTERT gene expression in these cells was silenced by hypermethylation of the promoter.