Ali M. Idris

Mutations of the p53 gene in oral squamous-cell carcinomas from sudanese dippers of nitrosamine-rich toombak and non-snuff-dippers from the Sudan and Scandinavia

Using PCR‐SSCP/DNA sequencing methods, we analyzed 14 oral squamous‐cell carcinomas (OSCCs) and 8 pre‐malignant oral lesions from different Sudanese patients for prevalence of mutations in exons 5 to 9 of the p53 gene in relation to toombak‐dipping status. OSCCs (14 from Sudan, 28 from Scandinavia), and 3 pre‐malignant oral lesions from Sudanese non‐dippers were used as controls. A statistically significant increased incidence in mutations of the p53 gene was found in OSCCs from toombak dippers (93%; 13/14), as compared with those from non‐dippers in Sudan (57%; 8/14) and in Scandinavia (61%; 17/28) respectively. In OSCCs from dippers, mutations were found in exons 5 to 9, while in those from non‐dippers they were found in exons 5, 7, 8, 9, and no mutations were found in exon 8 in any of the OSCCs from Sudan. Certain types of mutations, however, were similar with respect to exposure to toombak. OSCCs from dippers showed 15 transversions, 9 transitions, 3 insertions and one deletion, compared with 7 transversions, 2 transitions and one deletion found in OSCCs from Sudanese non‐dippers, and 9 transversions, 17 transitions and 2 insertions found in those from non‐dippers in Scandinavia. No mutations were found in any of the non‐malignant oral lesions in relation to dipping or non‐dipping status. These findings suggest that (i) the use of toombak plays a significant role in induction of increased p53 gene mutations, (ii) mutations observed were similar to those induced by tobacco‐specific N‐nitrosamines (TSNAs) in experimental animal models and those already reported in toombak dippers, (iii) types of mutations associated with TSNAs were similar in the exposed and the control groups, (iv) a novel mutation in exon 6 was found in the OSCCs from toombak dippers, (v) the p53 exons 5 (codon 130), 6 (codons 190, 216) and 7 (codons 229, 249, 252) mutations are probable hot spots for toombak‐related OSCCs. Further studies are necessary to validate the increased incidence and exon locations of the p53‐gene mutations as a biomarker of malignant transformation in populations in which the oral use of tobacco is habitual. Int. J. Cancer 81:527–534, 1999.

Expression of keratin 13, 14 and 19 in oral squamous cell carcinomas from Sudanese snuff dippers: Lack of association with human papillomavirus infection

In stratified squamous epithelia, altered expression of keratins (Ks) is one possible marker of malignant potential. In the epithelium of the uterine cervix, presence of human papillomaviruses (HPVs) is increasingly regarded as a marker of risk for cervical cancer. However, a similar role in oral cancer and precancer remains controversial. To address these questions, formalin‐fixed, paraffin‐embedded oral carcinomas from Sudanese snuff dippers (n=14) and oral carcinomas from Sudanese (n=14), Swedish (n=19) and Norwegian (n=41) non‐snuff dippers were examined by immunohistochemistry for expression of K types 13, 14 and 19 using monoclonal antibodies. HPV infection was searched for in all the carcinomas by in situ hybridization (ISH) using the cocktail HPV OmniProbe and the ViraType probe. Carcinomas from Sudanese (snuff dippers/non‐snuff dippers) were also examined for HPV infection by polymerase chain reaction (PCR) using the general HPV primers GP5+/GP6+. For the oral carcinomas from snuff dippers, moderate to intense expression of K13 (71%; 10/14), K14 (86%; 12/14) and K19 (93%; 13/14) was found. For the oral carcinomas from non‐snuff dippers, weak to moderate expression of K13 (64%; 47/74), K14 (43%; 32/74) and K19 (45%; 33/74) was found. HPV DNA was not detected in any of the carcinomas from three countries when examined by ISH. The Sudanese (from snuff dippers/non‐snuff dippers) oral carcinomas were also negative for HPV DNA with the PCR. The present study shows that (i) there is a high level of expression of K13, K14 and K19 in oral carcinomas from snuff dippers compared to those from non‐snuff dippers, (ii) this high level of expression may arise from dysregulation of keratinocyte proliferation and maturation caused by damaging effects of snuff, (iii) the HPV genome is not found in Sudanese (snuff dippers/non‐snuff dippers), Swedish or Norwegian oral carcinomas, and (iv) this may suggest that these viruses do not play a prominent role in the aetiology of oral carcinomas from these countries.

Immunohistochemical detection of p53 in non-malignant and malignant oral lesions associated with snuff dipping in the Sudan and Sweden

Immunohistochemistry was used to examine the expression of p53 in pre‐malignant oral lesions and oral squamous‐cell carcinomas (SCCs) from Swedish and Sudanese snuff‐dippers, as well as in pre‐malignant oral lesions and oral SCCs from non‐snuff‐dippers from the Sudan, Sweden and Norway. Of the 14 SCCs from Sudanese snuff‐dippers, 21% (3/14) expressed p53. Of the 14, 60 and 41 SCCs from non‐snuff‐dippers from the Sudan, Sweden and Norway, 64% (9/14), 65% (39/60) and 68% (28/41) expressed p53, respectively. A statistically significant difference in expression of p53 was found in SCCs from Sudanese snuff‐dippers compared to those from non‐snuff‐dippers from all/or any of the 3 countries. None of the suspected pre‐malignant oral lesions from Sudanese snuff dippers or non‐snuff‐dippers expressed p53. Only 2 out of the 15 oral fibro‐epithelial hyperplastic lesions from Swedish snuff‐dippers expressed p53. Some of the oral epithelial dysplastic lesions, as well as the carcinoma in situ lesions from Norwegian non‐snuffdippers, expressed p53, while the oral fibro‐epithelial hyperplastic lesions did not. The low relative frequency of p53 expression found in oral SCCs from snuff‐dippers compared to those from non‐snuff‐dippers might suggest differences in mechanisms of oncogenic action induced by snuff. Alternatively, the pathogenesis of malignant oral lesions from snuff‐dippers may follow a p53‐independent pathway. In view of the unusually high levels of the tobacco‐specific nitrosamines (TSNA) found in the type of snuff used in the Sudan, investigations of p53 mutations or oncogenes are needed.

Actinomycetoma of the mandibular region causing ankylosis

A case of mycetoma of the mandibular region caused by Actinomadura madurae is presented. Diagnostic procedures and rationale for treatment are discussed. In tropical and subtropical areas where mycetoma is endemic it should be included in the differential diagnosis of tumours of the facio-maxillary region.