- Email: [email protected]
p53 Point Mutation is Rare in Meningiomas from Singaporean Patients
Original Article
p53 Point Mutation is Rare in Meningiomas from Singaporean Patients Asha Das, Wan-Loo Tan1 and Duncan R. Smith,2 Maxine Dunitz Neurosurgical Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA, 1Department of Neurology, National Neuroscience Institute, Singapore, and 2Laboratory of Molecular Pathology, Institute of Molecular Biology and Genetics, Mahidol University, Nakorn Pathom, Thailand.
In Asian populations, meningiomas account for up to 35% of all central nervous system tumours, a significantly higher incidence than in Caucasian populations. While several studies have examined p53 both at the level of the gene and the protein in both benign and malignant meningiomas, its role remains controversial, particularly with regard to the discrepancy between p53 over-expression and gene mutation. We examined 19 benign meningiomas, all of which were known to over-express p53, and eight malignant meningiomas, of which three were known to over-express p53, for mutations in the p53 gene using polymerase chain reaction amplification and direct sequencing of exons 4 to 9, inclusive. Only one single mutation was detected in a benign meningioma, confirming that p53 over-expression in meningiomas is commonly found in the absence of gene mutations, and that despite the significantly higher incidence of meningiomas in some Asian populations, this is not associated with a significantly higher rate of p53 mutations. [Asian J Surg 2005;28(1):7–10] Key Words: p53, tumour suppressor, meningioma, mutation
Introduction Meningiomas are an extremely common form of central nervous system tumour. Arising from the arachnoidal cells of the meninges,1–3 meningiomas are predominantly benign, although in up to 10% of cases, they may show overt signs of malignancy such as nuclear pleomorphism, architectural disorganization, necrosis, prominent nucleoli and increased mitosis.4 The often critical location of meningiomas may make complete resection difficult, often leading to rapid recurrence.5 While meningiomas make up approximately 20% of central nervous system tumours in Western populations,6,7 they can represent up to 35% of central nervous system tumours in Asian and African populations.8–10 As yet, it is unclear why meningiomas are more common in Asian populations; significant differences in tumour aetiology between
meningiomas from Western cohorts and those from studies in Asia have not been documented. Mutations in the p53 tumour suppressor gene are present in many different tumours, often at a high rate.11 Such mutations often lead to over-expression of the p53 protein, as detected by immunohistochemistry, due to stabilization of the mutant protein and, therefore, p53 over-expression is often used as a marker for p53 point mutation. Many studies have examined benign and atypical/malignant meningiomas for over-expression of the p53 protein with diverse results:12–24 p53 over-expression has been reported in 0–10% of benign, 50–72.7% of atypical and 77–88.9% of anaplastic or malignant meningiomas.10,19,22,23 Despite the differing rates, all of the studies are consistent, with atypical/malignant tumours showing higher rates of over-expression than benign meningiomas. However, studies on the biological sig-
Address correspondence and reprint requests to Dr. Duncan R. Smith, Laboratory of Molecular Pathology, Institute of Molecular Biology and Genetics, Mahidol University, Salaya Campus, 25/25 Phutamonton Sai 4, Nakorn Pathom 73170, Thailand. E-mail: [email protected] • Date of acceptance: 15 March 2003 © 2005 Elsevier. All rights reserved.
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nificance of p53 over-expression are highly contradictory. While over-expression of p53 has been associated with recurrence in some studies,14,15,19 no association has been found in others,13,18,24 and still other studies have suggested that expression of high levels of p53 may be protective against recurrence.25 Fewer studies, however, have examined the p53 gene directly for mutations,19–23,26–28 and these studies typically have not observed mutations in the p53 gene,19–21,26–28 although rare mutants have been described.22,27 One group working on specimens from Korean patients has documented a rate of nearly 40% of p53 over-expressing meningiomas as having mutations, and observed that the mutation rate was associated with both histological grade and recurrence.23 In light of the high rate of p53 mutants documented in Asian patients in the Korean study, we sought to determine whether wellcharacterized meningiomas from our earlier series10,24 also showed evidence of high levels of mutations in the p53 gene.
Materials and methods Patients and tumours Meningioma samples were selected from two previously analysed series of meningiomas.10,24 The first of these series consisted of 20 benign and 20 malignant meningiomas examined for p53 and bax over-expression as well as for the presence of apoptotic cells,10 while the second series consisted of 90 benign meningiomas examined for over-expression of p53, mdm2 and the progesterone receptor.24 A total of 27 samples were selected, 19 benign meningiomas and eight malignant meningiomas. All 19 benign meningiomas stained positive for p53 over-expression (12 with positive nuclear expression and 7 with cytoplasmic staining); they came from 13 male patients aged 44–75 years and six female patients aged 39–69 years. Of the eight malignant meningiomas, three had positive nuclear
staining and five were negative for p53 over-expression; they came from three males aged 51–78 years and five female patients aged 28–79 years. The whole cohort consisted of 16 male and 11 female patients.
p53 mutation analysis Genomic DNA was prepared from one 10 +m thick section of paraffin-embedded tissue from each selected tumour. The tissue section was placed in a 1.5 mL centrifuge tube together with 1 mL of xylene and incubated in a tube rotator for 30 minutes at room temperature. The contents were subsequently pelleted by centrifugation. Two further resuspension and pelleting steps were undertaken. The pellet was washed twice with absolute ethanol, air dried, resuspended in 100 +L water containing 20 mg proteinase K (Boehringer Mannheim GmBH, Penzburg, Germany) and 5% sodium dodecylsulfate and incubated overnight at 50$C. Proteinase K was inactivated by heating to 90$C and the debris was pelleted by centrifugation. The supernatant was extracted twice with an equal volume of phenol and once with chloroform. DNA was precipitated by addition of 2.5 volumes ice-cold ethanol and sodium acetate to 0.3 M and incubating at –80$C for 15 minutes. The DNA was pelleted by centrifugation and resuspended in sterile distilled water. Exons 4 to 9, inclusive, of the p53 gene were amplified separately by polymerase chain reaction (PCR) using specific primer pairs (Table). The amplification products were purified by agarose gel electrophoresis and excised from the gel matrix, after which templates were purified using the Geneclean III Kit (Bio101, Vista, CA, USA) and subjected directly to DNA sequence analysis. DNA sequencing reactions were performed using the Big Dye Termination Reaction Kit (PE Applied Biosystems, Foster City, CA, USA) on approximately 60–90 ng of purified template. Analysis was undertaken on an automated ABI 377-18 DNA sequencer (PE Applied Biosystems).
Table. Primer pairs Exon 4 5 6 7 8 9
8
Size (bp) 460 264 217 232 344 275
Forward primer
Reverse primer
5'-AAGGACAAGGGTTGGGC-3' 5'-TTGTGCCCTGACTTTCAA-3' 5'-AGACGACAGGGCTGGTT-3' 5'-TTGCCACAGGTCTCCCCAA-3' 5'-TGGTTGGGAGTAGATGGA-3' 5'-AGCACTAAGCGAGGTAA-3'
5'-AGGAATCCCAAAGTTCCA-3' 5'-AACCAGCCCTGTCGTCTCT-3' 5'-ACCCTTAACCCCTCCTC-3' 5'-GTCAGAGGCAAGCAGA-3' 5'-AGGAAAGAGGCAAGGAAA-3' 5'-TGCCCCAATTGCAGGTAAA-3'
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■ p53 IN MENINGIOMAS ■
*
Figure. DNA sequencing electropherogram of a portion of exon 6 of the p53 gene from a benign meningioma. The position of the mutation (CCG to CTG) is indicated by an asterisk.
Results A single transition mutation was detected in exon 6 at codon 223 (CCG to CTG) in a sample from a benign meningioma with nuclear p53 over-expression (Figure). This mutation changed the encoded proline to a leucine (Pro223Leu).
Discussion Our detection of a single mutation in a benign meningioma contrasts sharply with the results of Cho et al, who documented p53 mutations in up to 40% of Korean patients,23 but is more in accord with those of other studies.19–22,26–28 The discrepancy between our study and that of Cho et al is unlikely to arise from the extent of the p53 gene investigated, as while Cho et al studied exons 5 to 8,23 our study examined exons 4 to 9 inclusive, a region known to contain the vast majority of all p53 mutations.29 One other study that has examined all p53 exons in meningioma cases also failed to find a high level of mutation. While it is possible that our methodology of direct sequencing of all exons failed to detect some mutants, the single-strand conformational polymorphism pre-screening methodology used by Cho and co-workers can also miss mutants as the mutation may not introduce a large enough alternate conformation.30 Several endogenous cellular mechanisms have been proposed for the over-expression of p53 in the absence of stabilizing mutations,31 but the primary cause of p53 over-expression in meningiomas remains to be discovered. Possible mechanisms include complexing with viral proteins or the mdm2 protein,32 deletion of the INK4a-ARF gene,33 cytoplasmic sequestration34 or even lesions in the ubiquitination pathway that targets p53 for degradation.35 In the absence of any evidence suggesting a viral aetiology for meningiomas, it would seem likely that one of the latter pathways may provide the reason for over-expression of p53 in
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meningiomas without p53 mutations. Studies that have examined over-expression of the mdm2 protein provide little evidence for a correlation between mdm2 over-expression and p53 over-expression.19,24,36 Perhaps the most pressing question at present is whether the over-expressed p53 in meningiomas retains some, or even all, of its function. Evidence showing that the over-expressed p53 retains function suggests that a critical molecular lesion lies further downstream in the molecular pathway, possibly with one of the mediators of cellular apoptosis,37 and we have started to investigate proteins involved in the mediation of apoptosis in meningiomas.38
Acknowledgements This study was supported by Singapore National Medical Research Council Grant Number NRN 99/003.
References 1. Al-Mefty O, Origitano TC. Meningiomas. In: Rengachary SS, Wilkins RH, eds. Principles of Neurosurgery. London: Wolfe Publishing, 1994: 28.1–28.12. 2. Black PM. Meningiomas. Neurosurgery 1993;32:643–57. 3. Cushing H. Intrakranielle Tumouren. Berlin: Springer, 1935. 4. Prayson RA. Malignant meningioma: a clinicopathologic study of 23 patients including MIB1 and p53 immunohistochemistry. Am J Clin Pathol 1996;105:719–26. 5. Langford LA. Pathology of meningiomas. J Neurooncol 1996;29: 217–21. 6. Kepes JJ. Meningiomas. Biology, Pathology and Differential Diagnosis. New York: Masson, 1982. 7. Rachlin JR, Rosenblum ML. Etiology and biology of meningiomas. In: Al-Mefty O, ed. Meningiomas. New York: Raven Press, 1991:27–36. 8. Bondy M, Ligon BL. Epidemiology and etiology of intracranial meningiomas: a review. J Neurooncol 1996;29:197–205. 9. Wen-qing H, Shi-ju Z, Qing-sheng T, et al. Statistical analysis of central nervous system tumors in China. J Neurosurg 1982;56:555–64.
9
■ DAS et al ■
10. Das A, Tang WY, Smith DR. Meningiomas in Singapore: demographic and biological characteristics. J Neurooncol 2000;47:153–60. 11. Soussi T. The p53 tumor suppressor gene: from molecular biology to clinical investigation. Ann NY Acad Sci 2000;910:121–37. 12. Amatya VJ, Takeshima Y, Sugiyama K, et al. Immunohistochemical study of Ki-67 (MIB-1), p53 protein, p21WAF1, and p27KIP1 expression in benign, atypical, and anaplastic meningiomas. Hum Pathol 2001;32:970–5. 13. Lanzafame S, Torrisi A, Barbagallo G, et al. Correlation between histological grade, MIB-1, p53, and recurrence in 69 completely resected primary intracranial meningiomas with a 6 year mean follow-up. Pathol Res Pract 2000;196:483–8. 14. Kamei Y, Watanabe M, Nakayama T, et al. Prognostic significance of p53 and p21WAF1/CIP1 immunoreactivity and tumor micronecrosis for recurrence of meningiomas. J Neurooncol 2000;46:205–13. 15. Konstantinidou AE, Pavlopoulos PM, Patsouris E, et al. Expression of apoptotic and proliferation markers in meningiomas. J Pathol 1998;186:325–30. 16. Ng HK, Chen L. Apoptosis is associated with atypical or malignant change in meningiomas. An in situ labelling and immunohistochemical study. Histopathology 1998;33:64–70. 17. Karamitopoulou E, Perentes E, Tolnay M, et al. Prognostic significance of MIB-1, p53, and bcl-2 immunoreactivity in meningiomas. Hum Pathol 1998;29:140–5. 18. Perry A, Stafford SL, Scheithauer BW, et al. The prognostic significance of MIB-1, p53, and DNA flow cytometry in completely resected primary meningiomas. Cancer 1998;82:2262–9. 19. Ohkoudo M, Sawa H, Hara M, et al. Expression of p53, MDM2 protein and Ki-67 antigen in recurrent meningiomas. J Neurooncol 1998;38:41–9. 20. Nagashima G, Aoyagi M, Yamamoto M, et al. P53 overexpression and proliferative potential in malignant meningiomas. Acta Neurochir (Wien) 1999;141:53–61. 21. Ellison DW, Lunec J, Gallagher PJ, et al. Accumulation of wildtype p53 in meningiomas. Neuropathol Appl Neurobiol 1995;21:136– 42. 22. Wang JL, Zhang ZJ, Hartman M, et al. Detection of TP53 gene mutation in human meningiomas: a study using immunohistochemistry, polymerase chain reaction/single-strand conformation polymorphism and DNA sequencing techniques on paraffinembedded samples. Int J Cancer 1995;64:223–8. 23. Cho H, Ha SY, Park SH, et al. Role of p53 gene mutation in tumor aggressiveness of intracranial meningiomas. J Korean Med Sci 1999; 14:199–205.
10
24. Das A, Tan WL, Teo J, et al. Overexpression of mdm2 and p53 and association with progesterone receptor expression in benign meningiomas. Neuropathology 2002;22:194–9. 25. Hakin-Smith V, Battersby RD, Maltby EL, et al. Elevated p53 expression in benign meningiomas protects against recurrence and may be indicative of senescence. Neuropathol Appl Neurobiol 2001;27:40–9. 26. Verheijen FM, Sprong M, Kloosterman JM, et al. TP53 mutations in human meningiomas. Int J Biol Markers 2002;17:42–8. 27. Joachim T, Ram Z, Rappaport ZH, et al. Comparative analysis of the NF2, TP53, PTEN, KRAS, NRAS and HRAS genes in sporadic and radiation-induced human meningiomas. Int J Cancer 2001;94:218– 21. 28. Ohgaki H, Eibl RH, Schwab M, et al. Mutations of the p53 tumor suppressor gene in neoplasms of the human nervous system. Mol Carcinog 1993;8:74–80. 29. Olivier M, Eeles R, Hollstein M, et al. The IARC TP53 database: new online mutation analysis and recommendations to users. Hum Mutat 2002;19:607–14. 30. Inoue Y, Nishio H, Shirakawa T, et al. Detection of mutations in the COL4A5 gene in over 90% of male patients with X-linked Alport’s syndrome by RT-PCR and direct sequencing. Am J Kidney Dis 1999; 34:854–62. 31. Harris CC. Structure and function of the p53 tumour suppressor gene: clues for rational cancer therapeutic strategies. J Natl Cancer Inst 1996;88:1442–55. 32. Vogelstein B, Kinzler KW. p53 function and dysfunction. Cell 1992; 70:523–6. 33. Vogelstein B, Lane D, Levine AJ. Surfing the p53 network. Nature 2000;408:307–10. 34. Moll UM, LaQuaglia M, Benard J, et al. Wild-type p53 protein undergoes cytoplasmic sequestration in undifferentiated neuroblastomas but not in differentiated tumors. Proc Natl Acad Sci USA 1995;92:4407–11. 35. Chowdary DR, Dermody JJ, Jha KK, et al. Accumulation of p53 in a mutant cell line defective in the ubiquitin pathway. Mol Cell Biol 1994;14:1997–2003. 36. Pykett MJ, Landers J, George DL. Expression patterns of the p53 tumor suppressor gene and the mdm2 proto-oncogene in human meningiomas. J Neurooncol 1997;32:39–44. 37. Fridman JS, Lowe SW. Control of apoptosis by p53. Oncogene 2003; 22:9030–40. 38. Das A, Tan WL, Smith DR. Expression of the inhibitor of apoptosis protein survivin in benign meningiomas. Cancer Lett 2003;193:217– 23.
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p53 Point Mutation is Rare in Meningiomas from Singaporean Patients Asha Das, Wan-Loo Tan1 and Duncan R. Smith,2 Maxine Dunitz Neurosurgical Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA, 1Department of Neurology, National Neuroscience Institute, Singapore, and 2Laboratory of Molecular Pathology, Institute of Molecular Biology and Genetics, Mahidol University, Nakorn Pathom, Thailand.
In Asian populations, meningiomas account for up to 35% of all central nervous system tumours, a significantly higher incidence than in Caucasian populations. While several studies have examined p53 both at the level of the gene and the protein in both benign and malignant meningiomas, its role remains controversial, particularly with regard to the discrepancy between p53 over-expression and gene mutation. We examined 19 benign meningiomas, all of which were known to over-express p53, and eight malignant meningiomas, of which three were known to over-express p53, for mutations in the p53 gene using polymerase chain reaction amplification and direct sequencing of exons 4 to 9, inclusive. Only one single mutation was detected in a benign meningioma, confirming that p53 over-expression in meningiomas is commonly found in the absence of gene mutations, and that despite the significantly higher incidence of meningiomas in some Asian populations, this is not associated with a significantly higher rate of p53 mutations. [Asian J Surg 2005;28(1):7–10] Key Words: p53, tumour suppressor, meningioma, mutation
Introduction Meningiomas are an extremely common form of central nervous system tumour. Arising from the arachnoidal cells of the meninges,1–3 meningiomas are predominantly benign, although in up to 10% of cases, they may show overt signs of malignancy such as nuclear pleomorphism, architectural disorganization, necrosis, prominent nucleoli and increased mitosis.4 The often critical location of meningiomas may make complete resection difficult, often leading to rapid recurrence.5 While meningiomas make up approximately 20% of central nervous system tumours in Western populations,6,7 they can represent up to 35% of central nervous system tumours in Asian and African populations.8–10 As yet, it is unclear why meningiomas are more common in Asian populations; significant differences in tumour aetiology between
meningiomas from Western cohorts and those from studies in Asia have not been documented. Mutations in the p53 tumour suppressor gene are present in many different tumours, often at a high rate.11 Such mutations often lead to over-expression of the p53 protein, as detected by immunohistochemistry, due to stabilization of the mutant protein and, therefore, p53 over-expression is often used as a marker for p53 point mutation. Many studies have examined benign and atypical/malignant meningiomas for over-expression of the p53 protein with diverse results:12–24 p53 over-expression has been reported in 0–10% of benign, 50–72.7% of atypical and 77–88.9% of anaplastic or malignant meningiomas.10,19,22,23 Despite the differing rates, all of the studies are consistent, with atypical/malignant tumours showing higher rates of over-expression than benign meningiomas. However, studies on the biological sig-
Address correspondence and reprint requests to Dr. Duncan R. Smith, Laboratory of Molecular Pathology, Institute of Molecular Biology and Genetics, Mahidol University, Salaya Campus, 25/25 Phutamonton Sai 4, Nakorn Pathom 73170, Thailand. E-mail: [email protected] • Date of acceptance: 15 March 2003 © 2005 Elsevier. All rights reserved.
ASIAN JOURNAL OF SURGERY VOL 28 • NO 1 • JANUARY 2005
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■ DAS et al ■
nificance of p53 over-expression are highly contradictory. While over-expression of p53 has been associated with recurrence in some studies,14,15,19 no association has been found in others,13,18,24 and still other studies have suggested that expression of high levels of p53 may be protective against recurrence.25 Fewer studies, however, have examined the p53 gene directly for mutations,19–23,26–28 and these studies typically have not observed mutations in the p53 gene,19–21,26–28 although rare mutants have been described.22,27 One group working on specimens from Korean patients has documented a rate of nearly 40% of p53 over-expressing meningiomas as having mutations, and observed that the mutation rate was associated with both histological grade and recurrence.23 In light of the high rate of p53 mutants documented in Asian patients in the Korean study, we sought to determine whether wellcharacterized meningiomas from our earlier series10,24 also showed evidence of high levels of mutations in the p53 gene.
Materials and methods Patients and tumours Meningioma samples were selected from two previously analysed series of meningiomas.10,24 The first of these series consisted of 20 benign and 20 malignant meningiomas examined for p53 and bax over-expression as well as for the presence of apoptotic cells,10 while the second series consisted of 90 benign meningiomas examined for over-expression of p53, mdm2 and the progesterone receptor.24 A total of 27 samples were selected, 19 benign meningiomas and eight malignant meningiomas. All 19 benign meningiomas stained positive for p53 over-expression (12 with positive nuclear expression and 7 with cytoplasmic staining); they came from 13 male patients aged 44–75 years and six female patients aged 39–69 years. Of the eight malignant meningiomas, three had positive nuclear
staining and five were negative for p53 over-expression; they came from three males aged 51–78 years and five female patients aged 28–79 years. The whole cohort consisted of 16 male and 11 female patients.
p53 mutation analysis Genomic DNA was prepared from one 10 +m thick section of paraffin-embedded tissue from each selected tumour. The tissue section was placed in a 1.5 mL centrifuge tube together with 1 mL of xylene and incubated in a tube rotator for 30 minutes at room temperature. The contents were subsequently pelleted by centrifugation. Two further resuspension and pelleting steps were undertaken. The pellet was washed twice with absolute ethanol, air dried, resuspended in 100 +L water containing 20 mg proteinase K (Boehringer Mannheim GmBH, Penzburg, Germany) and 5% sodium dodecylsulfate and incubated overnight at 50$C. Proteinase K was inactivated by heating to 90$C and the debris was pelleted by centrifugation. The supernatant was extracted twice with an equal volume of phenol and once with chloroform. DNA was precipitated by addition of 2.5 volumes ice-cold ethanol and sodium acetate to 0.3 M and incubating at –80$C for 15 minutes. The DNA was pelleted by centrifugation and resuspended in sterile distilled water. Exons 4 to 9, inclusive, of the p53 gene were amplified separately by polymerase chain reaction (PCR) using specific primer pairs (Table). The amplification products were purified by agarose gel electrophoresis and excised from the gel matrix, after which templates were purified using the Geneclean III Kit (Bio101, Vista, CA, USA) and subjected directly to DNA sequence analysis. DNA sequencing reactions were performed using the Big Dye Termination Reaction Kit (PE Applied Biosystems, Foster City, CA, USA) on approximately 60–90 ng of purified template. Analysis was undertaken on an automated ABI 377-18 DNA sequencer (PE Applied Biosystems).
Table. Primer pairs Exon 4 5 6 7 8 9
8
Size (bp) 460 264 217 232 344 275
Forward primer
Reverse primer
5'-AAGGACAAGGGTTGGGC-3' 5'-TTGTGCCCTGACTTTCAA-3' 5'-AGACGACAGGGCTGGTT-3' 5'-TTGCCACAGGTCTCCCCAA-3' 5'-TGGTTGGGAGTAGATGGA-3' 5'-AGCACTAAGCGAGGTAA-3'
5'-AGGAATCCCAAAGTTCCA-3' 5'-AACCAGCCCTGTCGTCTCT-3' 5'-ACCCTTAACCCCTCCTC-3' 5'-GTCAGAGGCAAGCAGA-3' 5'-AGGAAAGAGGCAAGGAAA-3' 5'-TGCCCCAATTGCAGGTAAA-3'
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■ p53 IN MENINGIOMAS ■
*
Figure. DNA sequencing electropherogram of a portion of exon 6 of the p53 gene from a benign meningioma. The position of the mutation (CCG to CTG) is indicated by an asterisk.
Results A single transition mutation was detected in exon 6 at codon 223 (CCG to CTG) in a sample from a benign meningioma with nuclear p53 over-expression (Figure). This mutation changed the encoded proline to a leucine (Pro223Leu).
Discussion Our detection of a single mutation in a benign meningioma contrasts sharply with the results of Cho et al, who documented p53 mutations in up to 40% of Korean patients,23 but is more in accord with those of other studies.19–22,26–28 The discrepancy between our study and that of Cho et al is unlikely to arise from the extent of the p53 gene investigated, as while Cho et al studied exons 5 to 8,23 our study examined exons 4 to 9 inclusive, a region known to contain the vast majority of all p53 mutations.29 One other study that has examined all p53 exons in meningioma cases also failed to find a high level of mutation. While it is possible that our methodology of direct sequencing of all exons failed to detect some mutants, the single-strand conformational polymorphism pre-screening methodology used by Cho and co-workers can also miss mutants as the mutation may not introduce a large enough alternate conformation.30 Several endogenous cellular mechanisms have been proposed for the over-expression of p53 in the absence of stabilizing mutations,31 but the primary cause of p53 over-expression in meningiomas remains to be discovered. Possible mechanisms include complexing with viral proteins or the mdm2 protein,32 deletion of the INK4a-ARF gene,33 cytoplasmic sequestration34 or even lesions in the ubiquitination pathway that targets p53 for degradation.35 In the absence of any evidence suggesting a viral aetiology for meningiomas, it would seem likely that one of the latter pathways may provide the reason for over-expression of p53 in
ASIAN JOURNAL OF SURGERY VOL 28 • NO 1 • JANUARY 2005
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meningiomas without p53 mutations. Studies that have examined over-expression of the mdm2 protein provide little evidence for a correlation between mdm2 over-expression and p53 over-expression.19,24,36 Perhaps the most pressing question at present is whether the over-expressed p53 in meningiomas retains some, or even all, of its function. Evidence showing that the over-expressed p53 retains function suggests that a critical molecular lesion lies further downstream in the molecular pathway, possibly with one of the mediators of cellular apoptosis,37 and we have started to investigate proteins involved in the mediation of apoptosis in meningiomas.38
Acknowledgements This study was supported by Singapore National Medical Research Council Grant Number NRN 99/003.
References 1. Al-Mefty O, Origitano TC. Meningiomas. In: Rengachary SS, Wilkins RH, eds. Principles of Neurosurgery. London: Wolfe Publishing, 1994: 28.1–28.12. 2. Black PM. Meningiomas. Neurosurgery 1993;32:643–57. 3. Cushing H. Intrakranielle Tumouren. Berlin: Springer, 1935. 4. Prayson RA. Malignant meningioma: a clinicopathologic study of 23 patients including MIB1 and p53 immunohistochemistry. Am J Clin Pathol 1996;105:719–26. 5. Langford LA. Pathology of meningiomas. J Neurooncol 1996;29: 217–21. 6. Kepes JJ. Meningiomas. Biology, Pathology and Differential Diagnosis. New York: Masson, 1982. 7. Rachlin JR, Rosenblum ML. Etiology and biology of meningiomas. In: Al-Mefty O, ed. Meningiomas. New York: Raven Press, 1991:27–36. 8. Bondy M, Ligon BL. Epidemiology and etiology of intracranial meningiomas: a review. J Neurooncol 1996;29:197–205. 9. Wen-qing H, Shi-ju Z, Qing-sheng T, et al. Statistical analysis of central nervous system tumors in China. J Neurosurg 1982;56:555–64.
9
■ DAS et al ■
10. Das A, Tang WY, Smith DR. Meningiomas in Singapore: demographic and biological characteristics. J Neurooncol 2000;47:153–60. 11. Soussi T. The p53 tumor suppressor gene: from molecular biology to clinical investigation. Ann NY Acad Sci 2000;910:121–37. 12. Amatya VJ, Takeshima Y, Sugiyama K, et al. Immunohistochemical study of Ki-67 (MIB-1), p53 protein, p21WAF1, and p27KIP1 expression in benign, atypical, and anaplastic meningiomas. Hum Pathol 2001;32:970–5. 13. Lanzafame S, Torrisi A, Barbagallo G, et al. Correlation between histological grade, MIB-1, p53, and recurrence in 69 completely resected primary intracranial meningiomas with a 6 year mean follow-up. Pathol Res Pract 2000;196:483–8. 14. Kamei Y, Watanabe M, Nakayama T, et al. Prognostic significance of p53 and p21WAF1/CIP1 immunoreactivity and tumor micronecrosis for recurrence of meningiomas. J Neurooncol 2000;46:205–13. 15. Konstantinidou AE, Pavlopoulos PM, Patsouris E, et al. Expression of apoptotic and proliferation markers in meningiomas. J Pathol 1998;186:325–30. 16. Ng HK, Chen L. Apoptosis is associated with atypical or malignant change in meningiomas. An in situ labelling and immunohistochemical study. Histopathology 1998;33:64–70. 17. Karamitopoulou E, Perentes E, Tolnay M, et al. Prognostic significance of MIB-1, p53, and bcl-2 immunoreactivity in meningiomas. Hum Pathol 1998;29:140–5. 18. Perry A, Stafford SL, Scheithauer BW, et al. The prognostic significance of MIB-1, p53, and DNA flow cytometry in completely resected primary meningiomas. Cancer 1998;82:2262–9. 19. Ohkoudo M, Sawa H, Hara M, et al. Expression of p53, MDM2 protein and Ki-67 antigen in recurrent meningiomas. J Neurooncol 1998;38:41–9. 20. Nagashima G, Aoyagi M, Yamamoto M, et al. P53 overexpression and proliferative potential in malignant meningiomas. Acta Neurochir (Wien) 1999;141:53–61. 21. Ellison DW, Lunec J, Gallagher PJ, et al. Accumulation of wildtype p53 in meningiomas. Neuropathol Appl Neurobiol 1995;21:136– 42. 22. Wang JL, Zhang ZJ, Hartman M, et al. Detection of TP53 gene mutation in human meningiomas: a study using immunohistochemistry, polymerase chain reaction/single-strand conformation polymorphism and DNA sequencing techniques on paraffinembedded samples. Int J Cancer 1995;64:223–8. 23. Cho H, Ha SY, Park SH, et al. Role of p53 gene mutation in tumor aggressiveness of intracranial meningiomas. J Korean Med Sci 1999; 14:199–205.
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