The Oncologist, Vol. 12, No. 10, 1225-1236, October 2007; doi:10.1634/theoncologist.12-10-1225 © 2007 AlphaMed Press
Patient Gender Is Associated with Distinct Patterns of Chromosomal Abnormalities and Sex Chromosome–Linked Gene-Expression Profiles in MeningiomasaUnidad de Investigación, IECSCYL-Hospital Universitario de Salamanca, Salamanca, Spain; bNeurosurgery Service, Hospital Universitario de Salamanca, Salamanca, Spain; cNeuropathology Service, Hospital da Universidade de Coimbra, Coimbra, Portugal; dCentro de Investigación del Cáncer, Cytometry General Service and Department of Medicine, University of Salamanca, Salamanca, Spain Key Words. Gender • iFISH • Chromosomal abnormalities • Meningioma • Gene expression • Microarrays Correspondence: Maria Dolores Tabernero Redondo, M.D. Ph.D., Unidad de Investigación, Hospital Universitario de Salamanca, Paseo de San Vicente 58, 37007 Salamanca, Spain. Telephone: 923-29-12-30; Fax: 923-29-46-24; e-mail: taberner{at}usal.es Received June 4, 2007; accepted for publication July 25, 2007. Disclosure: No potential conflicts of interest were reported by the authors, planners, reviewers, or staff managers of this article.
The female predominance of meningiomas has been established, but how this is affected by hormones is still under discussion. We analyzed the characteristics of meningiomas from male (n = 53) and female (n = 111) patients by interphase fluorescence in situ hybridization (iFISH). In addition, in a subgroup of 45 (12 male and 33 female) patients, tumors were hybridized with the Affymetrix U133A chip. We show a higher frequency of larger tumors (p = .01) and intracranial meningiomas (p = .04) together with a higher relapse rate (p = .03) in male than in female patients. Male patients had a higher percentage of del(1p36) (p < .001), while loss of an X chromosome was restricted to tumors from female patients (p = .008). In turn, iFISH studies showed a higher frequency of chromosome losses, other than monosomy 22 alone, in meningiomas from male patients (p = .002), while female patients displayed a higher frequency of chromosome gains (p = .04) or monosomy 22 alone (p = .03) in the ancestral tumor clone. Interestingly, individual chromosomal abnormalities had a distinct impact on the recurrence-free survival rate of male versus female patients. In turn, gene expression showed that eight genes (RPS4Y1, DDX3Y, JARID1D, DDX3X, EIF1AY, XIST, USP9Y, and CYorf15B) had significantly different expression patterns (R2 > 0.80; p < .05) in tumors from male and female patients. In summary, we show the existence of different patterns of chromosome abnormalities and gene-expression profiles associated with patient gender, which could help to explain the slightly different clinical behavior of these two patient groups.
Meningiomas are neoplasias of cells from the meningeal coverings of the brain, most cases corresponding to histologically benign tumors. The incidence of meningiomas in women is more than twice as high as it is in men [1–3]. In addition, it is well known that female patients have a higher frequency of spinal meningiomas and a slightly better clinical outcome than male patients [4–5]. More recently, it was also reported that meningioma tumors in female patients display characteristic cytogenetic patterns that include a lower frequency of monosomy 14 and a greater proportion of cases with numerical abnormalities of chromosomes 22 and X, while complex karyotypes are more frequently observed in male patients [6–13]. Among other cytogenetic abnormalities, losses of chromosome 14 [8], whether associated or not with del(1p36) [9], have been associated with lower recurrence-free survival (RFS) rates in meningioma patients independently of patient gender and tumor histopathology. In addition, gains of chromosomes 11,15, and 22 and losses of chromosomes 10 and 18 have also been shown to have an impact on patient outcome, but they did not show independent prognostic value [8, 14]. For decades, gender-associated differences in the frequency and clinical behavior of meningiomas have been claimed to be most probably related to hormonal factors [15–20]. In line with this, previous reports have shown a higher growth rate of meningiomas during both pregnancy [21–23] and the luteal phase of the menstrual cycle [24], and an association has been observed between meningioma and breast cancer [25–27]. In addition, meningioma tumor cells frequently express progesterone receptors (PRs) [28–30] and, to a lesser extent, estrogen receptors (ERs) [31, 32] and androgen receptors (ARs) [33] as well; PR expression has been correlated with disease outcome [15, 16, 28–30, 34, 35], and progesterone has been shown to modulate the in vitro growth of meningioma cells [36], although modest results were observed after treatment of meningioma patients [37, 38]. Despite these findings, the exact causes and mechanisms leading to the female predominance of meningioma still remain poorly understood; moreover, recent studies [33] failed to detect different patterns of expression of hormone receptors, including PR, ER, and AR, between male and female patients with meningioma tumors. Therefore, the role of sex hormones in determining female predominance in meningioma could involve more complex mechanisms, or alternatively, they could just have a marginal impact. Despite these observations, no study has been reported so far in which the genetic and genomic differences between male and female meningioma patients have been systematically analyzed in a large series of patients. In the present study, we explored the clinical, histopathological, genetic, and prognostic differences between 53 male and 111 female meningioma patients; in addition, in a subgroup of 45 of these patients, we compared the patterns of gene expression between tumors from male and female patients. Our results show that, in addition to a higher frequency of spinal tumors and smaller meningiomas, female patients also display different patterns of chromosomal abnormalities than male patients, with many of the genetic changes observed showing a distinct impact on RFS in each of the two patient groups. Moreover, male and female meningioma patients had different patterns of gene expression, which were restricted to a few genes coded in the X and Y chromosomes.
Patients The study included 164 patients diagnosed with meningioma at the Neurosurgical Service of the University Hospital of Salamanca. Fifty-three (32%) were men and 111 (68%) were women, with a mean age ± standard deviation (SD) of 59 ± 15 years (range, 13–84 years). All except three cases underwent complete tumor resection of Simpson's grade 3 tumors [39]. Tumor diagnosis and classification were performed according to World Health Organization criteria [40]. Histologically, most tumors (91%) were classified as grade I; 8% were grade II (atypical) and 1% were grade III (anaplastic) meningiomas. The distribution of patients according to tumor location and size, as well as the frequency of cases with multifocal meningiomas are summarized in Table 1. Some (39%) of the patients included in this study were also included in a previous report from our group [8].
Follow-up controls for the early detection of relapse included, apart from routine clinical and biological parameters, neuroimaging analysis using axial computerized tomography and magnetic resonance imaging studies. At the close of this study, 26 patients had relapsed and 138 remained disease free; the median RFS and overall survival times for the whole series were 71 months (range, 7–242 months) and 81 months (range, 1–369 months), respectively. None of the patients received adjuvant radiotherapy or chemotherapy after diagnosis and prior to an eventual relapse. The study was approved by the institutional review board, and human investigations were performed after approval by the local ethical committee. Informed consent was obtained from each subject entering the study.
Interphase Fluorescence In Situ Hybridization Studies
RNA Extraction and Microarray Analyses of Gene Expression
Statistical Methods For the analysis of the results of microarray studies, data files containing information about gene expression for the 45 Affymetrix high-density oligonucleotide arrays/tumors analyzed were normalized using the Bioconductor (http://www.bioconductor.org) and R (version 2.3.0; http://www.r-project.org) software programs. Nonbiological background variation was removed using robust microarray normalization (RMA-preprocessing) [44]. For the identification of differentially expressed genes between tumors from male and female patients, the nearest shrunken centroids (Prediction Analysis of Microarrays software version 2.1; Tibshirani Lab, Department of Statistics, University of Stanford, Stanford, CA [45]), multivariate permutation (Significance Analysis of Microarrays software version 2.23 [46]), and Pearson correlation tests were used. Only those probes showing both a coefficient of correlation >0.80 and an adjusted p-value (as assessed by the Bonferroni test) <0.05 were considered to be differentially expressed in tumors from male and female patients. Supervised hierarchical clustering analysis based on the average linkage method and the use of Euclidean distances was performed with Gene Cluster 3.0 software (http://rana.lbl.gov/EisenSoftware.htm) [47] to classify tumors from male and female patients according to the patterns of differentially expressed genes between the two gender-associated tumor groups. The resulting cluster was graphically represented using the Java TreeView 1.0.13 software, which can be freely downloaded from http://jtreeview.sourceforge.net [48].
From a clinicobiological point of view, male patients had a significantly higher frequency of larger (>40 mm) tumors (p = .01) and intracranial meningiomas (p = .04) and a higher relapse rate (p = .03) associated with a slightly lower RFS rate (p = .11), in comparison with female patients (Table 1). In turn, no statistically significant differences were found between male and female meningioma patients regarding the frequency of multifocal tumors, tumor histology and grade, and the patients' overall mean age (Table 1); despite this, a significant predominance of female patients was observed from age 50 onward (p = .01) (Fig. 1).
Regarding the frequency of numerical abnormalities detected for each chromosome analyzed, a significantly higher percentage of cases with del(1p36) was observed among male patients (48% versus 16%; p < .001), whereas loss of chromosome X was restricted to female patients (14% versus 0%; p = .008) (Fig. 2A). Abnormalities of chromosome Y consisted of nulisomy Y and were detected in around one quarter of all male patients (26%). No statistically significant differences were detected between the patient groups for the other chromosomes analyzed (Fig. 2A). In turn, iFISH studies showed the presence of a single tumor cell clone in 67 of the 164 cases analyzed (41%), with similar frequencies in male (38%) and female (42%) patients. The remaining cases showed two to five coexisting tumor cell clones, with no significant difference in the mean number of clones per tumor detected in male versus female patients (mean number of clones per tumor, 2 ± 1 versus 2 ± 1; p > .05). Nevertheless, a more careful analysis of the cytogenetic patterns of the ancestral tumor cell clone showed statistically significant differences between male and female meningioma patients (Fig. 2B). Accordingly, the ancestral tumor cell clone of male meningioma patients more frequently showed one or more chromosome loss other than monosomy 22 alone (p = .002), whereas female patients had a higher frequency of cases carrying chromosome gains (p = .04) and monosomy 22 in the absence of other abnormalities (p = .03) in the ancestral tumor cell clone.
From a prognostic point of view, abnormalities of chromosomes 9, 14, and 22 had a significant impact on RFS in both groups of patients (p .008) (Fig. 3). However, a more detailed analysis of the impact of the abnormalities of these chromosomes on patient outcome showed that, while gain of chromosome 22 was associated with a lower RFS rate in both groups of patients, gain of chromosome 9 and monosomy 14 were associated with a worse prognosis in male patients, whereas loss of chromosome 9 and gain of chromosome 14 were related to a worse clinical outcome in female patients. In addition, losses of chromosomes 10 (p = .009) and 18 (p = .0007) were associated with a poor outcome in male but not in female patients, whereas gains of chromosomes 1q (p = .008), 7 (p = .005), and X (p = .001) had an adverse prognostic impact for female but not for male patients (Fig. 3). Multivariate analysis of prognostic factors showed that, in the whole patient series, loss of chromosome 14 (p = .02) together with tumor size >40 mm (p = .001) was the best combination of independent variables for predicting RFS. However, while in male patients loss of chromosome 14 (p = .02) and gain of chromosome 22 (p = .01) represented the best combination of independent parameters for predicting RFS, in female patients loss of chromosome 9 was the only independent prognostic factor (p = .001).
Analysis of the patterns of gene expression by oligonucleotide-based microarrays in a group of 45 meningiomas (Table 2
In the present study, we show the occurrence of unique patterns of cytogenetic abnormalities and gene-expression profiles in meningioma tumors from male and female patients. Interestingly, none of the differentially expressed genes in male versus female patients appeared to be directly related to the expression and or regulation of the expression of sex hormones and their receptors. Similarly, they did not reflect differences in the frequency of the distinct autosomal chromosome abnormalities observed between male and female meningioma patients. In contrast, all differentially expressed genes were coded in the sex chromosomes, particularly in chromosome Y. Together, these findings support the involvement of nonsteroid hormone–associated genetic factors coded in the sex chromosomes in the development of the disease, indicating that female predominance could be potentially associated with one or more sex chromosome–coded genes. In addition, they also suggest that the reported differences in the frequency of specific abnormalities involving autosomal chromosomes could be related to sex chromosome–inherited differences. So far, attempts aimed at the identification of different patterns of expression of individual sex hormone–associated proteins, such as PR, in male versus female meningioma patients have failed [16, 29, 33]. However, such studies have usually been based on the analysis of a restricted number of proteins, none of which is coded in the sex chromosomes. In the present study, only eight genes displayed a significantly different expression pattern in male versus female meningioma patients, and none of them was directly associated with expression of hormone receptors and genes involved in their regulation. In contrast, all eight genes were localized to the sex chromosomes: two in chromosome X (DDX3X, XIST) and six in chromosome Y (RPS4Y1, DDX3Y, JARID1D, EIF1AY, USP9Y, and CYorf15B). Interestingly, a third subgroup including both female patients with monosomy X and a male patient with nulisomy Y was clearly identified within the major cluster of tumors from female patients, based on the pattern of expression of these genes. A more detailed analysis of these eight genes suggests that some of them could be irrelevant in directly predisposing to the development of meningiomas. Accordingly, XIST is an essential gene for the inactivation of one of the two X chromosomes in female mammalian cells, which transcriptionally silences one X chromosome [49]. In turn, the USP9Y gene is a member of the C19 peptidase family that encodes for a protein similar to ubiquitin-specific proteases, which cleaves the ubiquitin moiety from ubiquitin-fused precursors and ubiquitinylated proteins [50]; mutations in USP9Y have been associated with Sertoli cell-only syndrome and male infertility [51]. In line with this limited evidence of both genes directly contributing to a female predominance in meningioma, XIST and USP9Y have been previously reported to be differentially expressed in normal human blood cells and mouse brain tissues from male versus female individuals [52–54]. In contrast, the exact role of the other six differentially expressed genes in determining the female predominance of meningioma remains to be elucidated. Interestingly, analysis of different Web-based freely accessible microarray gene-expression data sets from brain tissue [55], hematopoietic neoplastic cells from chronic lymphocytic leukemia [56], and renal cancer tissues [57] showed that, apart from the DDX3Y gene, the other genes are also differentially expressed in normal and/or neoplastic tissues from male versus female individuals in the first two data sets. In turn, no significant differences were observed in the expression patterns of these genes in normal somatic meningeal cell samples from the male (n = 2) and female (n = 2) individuals analyzed in this study (data not shown). The DDX3Y DEAD box protein and its homologue in the X chromosome (DDX3X) act as human RNA helicases and are localized close to the nuclear membrane pore, and are involved in exporting RNA outside the nucleus during embryogenesis, spermatogenesis, and both cellular growth and division [58]. Further investigations are necessary to elucidate the exact explanation for the association between the expression of this gene and gender in meningioma patients. In line with preliminary results from our [41, 42] and other [59–62] groups, gender was also associated with the presence of different cytogenetic abnormalities in the ancestral tumor cell clone in meningiomas. Accordingly, while ancestral tumor cell clones of female meningioma patients more frequently showed monosomy 22 alone and gains of individual chromosomes, tumors from male patients were frequently related to the presence of losses of chromosomes other than monosomy 22 and complex karyotypes including nulisomy Y, monosomy 14, and del(1p36) in the ancestral tumor cell clone. Together, these findings further support the existence of different cytogenetic pathways of clonal evolution in meningioma patients [42], providing increasing evidence for the involvement of gender in this process. Based on the type of chromosomal abnormalities detected at different frequencies in male versus female meningioma patients, including those identified in their ancestral tumor cell clones, it could be speculated that deletion of the NF2 gene in chromosome 22 or dysregulation of oncogenes as a result of chromosome gains in a smaller proportion of cases could play a central role in tumor development in female patients, while tumor suppressor genes encoded in chromosomes other than chromosome 22 (e.g., genes coded in chromosomes 1p and 14, among others), alone or in combination with other tumor suppressor genes and/or oncogenes, could determine development and progression of meningiomas in male patients [63–67]. In line with this hypothesis, recent results [43] suggest that spinal tumors, also found in the present series to be almost entirely restricted to female patients, show unique patterns of gene expression associated with the presence of monosomy 22 in the ancestral tumor cell clone. In addition, such differences could also help to explain the slightly higher frequency of grade II or III meningiomas and larger tumors among male patients. However, in the present study, no clear association was found between the patterns of gene expression in male and female patients that could be related to differences in autosomal chromosome gains or losses. This could be because of the fact that, on most occasions, monosomy 14 and del(1p36) are present in only a subset of all meningioma tumor cells [14, 42], and in the present study, the patterns of gene expression were analyzed for the overall tumor and not for specific tumor cell clones. Further studies are necessary to investigate the potential relationship between the differentially expressed genes reported here between male and female patients and the distinct genetic abnormalities found in the two groups of patients. From a prognostic point of view, abnormalities in chromosome 14 have been shown to be a relevant prognostic factor for predicting RFS in meningioma patients independently of patient gender and tumor histopathology [8–10], as also confirmed in the present study. Moreover, to the best of our knowledge, no study has been reported so far in which the prognostic value of tumor cytogenetics has been separately analyzed in male and female patients. In this regard, we found a worse clinical outcome for male patients displaying losses of chromosome 10, 14, and 18, while female patients with gains of chromosomes 1q, 7, 9, 22, and X had a lower RFS rate. Together, these observations further support the hypothesis that loss of different tumor suppressor genes could also be responsible for disease outcome in male patients, while RFS in female patients is mainly affected by gains of certain oncogenes, particularly those localized to chromosomes 1q, 7, 9, 22, and X. The different patterns of clonal evolution found in male and female meningioma patients did not show a clear impact on the patterns of gene expression between the two groups of meningioma patients, which could further help to explain the different prognostic impact observed for most individual chromosomal abnormalities in male versus female patients. In line with this, previous multivariate studies [8, 67] have failed to show independent prognostic value for patient gender and monosomy 14, the latter clearly showing a higher prognostic impact, as also confirmed in the present study. Interestingly, we further show here that monosomy 14 together with a gain of chromosome 22 is the best combination of independent prognostic factors for RFS in male patients, while a gain of chromosome 9, but not the reported abnormalities in chromosomes 14 and 22, appear to be the most relevant prognostic factor in female patients. In summary, in the present study, we show the existence of different patterns of chromosomal abnormalities and gene-expression profiles in male versus female meningioma patients, which could help to explain the slightly different clinical behavior between the two patient groups. The observations that differentially expressed genes in male versus female patients are coded in the sex chromosomes and they are not directly related to sex hormone receptors support the hypothesis that sex chromosome–associated genes are involved in the gender-associated differences reported, although the exact role of hormonal factors remains unclear.
This work was partially supported by grants from the Fondo de Investigaciones Sanitarias (FIS/FEDER 02/0010 and RETICC RD06/0020/0035 from the Instituto de Salud Carlos III, Ministerio de Sanidad y Consumo, Madrid, Spain), Consejeria de Educación (HUS2/03, Junta de Castilla y León, Valladolid, Spain), and Fundación MMA (Madrid, Spain). M.D. Tabernero is supported by IECSCYL. A.B. Espinosa and J.M. Sayagues are supported by grants (FI05/00266 and CP05/00321, respectively) from the Ministerio de Sanidad y Consumo (Madrid, Spain).
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