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Keywords:

  • rhabdomyosarcoma;
  • anaplasia;
  • TP53;
  • germline mutations;
  • Li-Fraumeni syndrome

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. FUNDING SOURCES
  8. CONFLICT OF INTEREST DISCLOSURES
  9. REFERENCES
  10. Supporting Information

BACKGROUND

Rhabdomyosarcoma (RMS) represents a diverse category of myogenic malignancies with marked differences in molecular alterations and histology. This study examines the question if RMS predisposition due to germline TP53 mutations correlates with certain RMS histologies.

METHODS

The histology of RMS tumors diagnosed in 8 consecutive children with TP53 germline mutations was reviewed retrospectively. In addition, germline TP53 mutation analysis was performed in 7 children with anaplastic RMS (anRMS) and previously unknown TP53 status.

RESULTS

RMS tumors diagnosed in 11 TP53 germline mutation carriers all exhibited nonalveolar, anaplastic histology as evidenced by the presence of enlarged hyperchromatic nuclei with or without atypical mitotic figures. Anaplastic RMS was the first malignant diagnosis for all TP53 germline mutation carriers in this cohort, and median age at diagnosis was 40 months (mean, 40 months ± 15 months; range, 19-67 months). The overall frequency of TP53 germline mutations was 73% (11 of 15 children) in pediatric patients with anRMS. The frequency of TP53 germline mutations in children with anRMS was 100% (5 of 5 children) for those with a family cancer history consistent with Li-Fraumeni syndrome (LFS), and 80% (4 of 5 children) for those without an LFS cancer phenotype.

CONCLUSIONS

Individuals harboring germline TP53 mutations are predisposed to develop anRMS at a young age. If future studies in larger anRMS cohorts confirm the findings of this study, the current Chompret criteria for LFS should be extended to include children with anRMS irrespective of family history. Cancer 2014;120:1068–1075. © 2013 American Cancer Society.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. FUNDING SOURCES
  8. CONFLICT OF INTEREST DISCLOSURES
  9. REFERENCES
  10. Supporting Information

Soft tissue sarcomas (STSs) are a group of cancers arising in nonhematopoietic, mesodermal tissues. Rhabdomyosarcoma (RMS), the most common STS in children and adolescents, represents a diverse sarcoma category as evidenced by marked differences in histology, myogenic differentiation, oncogenic pathway activation, and mutational spectrum.[1, 2] The contributions of specific RMS-relevant pathways to the formation of RMS have been tested extensively in mice.[3-5] It is clear that, in mouse models, aberrations in distinct oncogenic pathways correlate with the induction of RMS tumors that share uniform histological appearance,[6] such as pleomorphic RMS due to inactivation of TP53 with or without introduction of oncogenic Kras[3, 5] and highly differentiated RMS due to activation of Sonic Hedgehog signaling.[4, 7]

This study builds on the hypothesis that the phenotype of RMS arising in the setting of sarcoma-predisposing germline lesions may offer a unique window into the genetic origins and biological identity of certain RMS subtypes. In humans, genetic susceptibility to develop RMS has been linked to germline mutations in PTCH1, HRAS, NF1, DICER1, and TP53.[8-16] In a previous study, 3 of 13 children with RMS diagnosed under 3 years of age, including 1 child with alveolar RMS and 2 children with nonalveolar RMS, were found to have TP53 germline mutations. None of 23 children with RMS diagnosed at older than 3 years of age harbored TP53 germline lesions.[11] These findings prompted recommendations to screen children diagnosed with RMS under the age of 36 months for the presence of TP53 germline mutations. Our review of 8 RMS tumors arising in children with TP53 germline mutations revealed that these tumors uniformly exhibited anaplasia, a distinctive histological subtype characterized by enlarged, hyperchromatic nuclei. In addition, 3 of 7 children with anaplastic RMS (anRMS) and previously unknown TP53 germline mutation status were determined to harbor TP53 germline mutations. Median age at diagnosis of anRMS in these 11 TP53 germline mutation carriers was 40 months (range, 19-67 months). These findings support the notion that TP53 pathway activation contributes to the biology of anRMS and, similar to observations in Wilms tumors and medulloblastoma,[17, 18] drives target cells for malignant transformation to assume an anaplastic phenotype.

MATERIALS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. FUNDING SOURCES
  8. CONFLICT OF INTEREST DISCLOSURES
  9. REFERENCES
  10. Supporting Information

Patient Selection and Clinical Data

Patients with RMS were selected as follows: 1) For the first exploratory cohort of patients (Table 1, cases 1-8), 8 children with RMS and TP53 germline mutations seen consecutively at Boston Children's Hospital, Boston, MA, and the Hospital for Sick Children, Toronto, Ontario, Canada since January 1 1985 were identified; and 2) for the expanded cohort (Table 1, cases 9-15), 7 children with anRMS and previously unknown TP53 germline mutation status[19-21] were evaluated. This study was approved by the institutional review boards at both institutions. Pathology specimen from the 3 RMS tumors diagnosed in TP53 germline mutation carriers and reported by Diller et al in 1995 could not be retrieved[11]; these cases therefore were not included in the cohort evaluated here.

Table 1. TP53 Germline Mutations in 15 Children With Anaplastic Rhabdomyosarcoma (anRMS)a
Case IDSexAge at Dx (mo)anRMSTP53 IHCPersonal Hx of CancerFamily Hx of LFS CancerTP53 Germline MutationDe Novo MutationMutation TypeExonPreviously Published
  1. Abbreviations: AC, adenocarcinoma; Dx, diagnosis; Hx, history; IHC, immunohistochemistry; LFS, Li-Fraumeni syndrome; n/a, not available; OS, osteosarcoma.

  2. a

    Cases 1-8 represent an exploratory cohort of 8 consecutive children with known TP53 germline mutations and RMS. Cases 9-15 form a secondary cohort of 7 children with anRMS and previously unknown TP53 germline mutation status. Immunohistochemical staining for TP53 was graded as present (+), absent (0) or not available (n/a). Family history of Li Fraumeni spectrum (LFS) cancers in first- or second-degree relatives was noted as present (+), absent (0) or unknown. Mutations were identified as inherited if one parent was found to carry the same TP53 germline mutation. Cases 2 and 10 carried the same germline TP53 mutation, previously published by Ruijs et al[28] and Bougeard et al.[31]

1M40++Unknown+IVS3-11 C>GInheritedSplice site mutationVarley et al (2001)
2M45+0Unknown+c.375G>A; p.T125TInheritedAltered splicingExon 4Ruijs et al (2010)
3F34++None+c.534C>G; p.H178QUnknownSubstitution, nonsenseExon 5Wozniak et al (2011)
4F64+0AC, Sarcoma+IVS05-1 G>CDe novoSplice site mutation 
5M50++OS, AC0c.1024C>T; p.R324XUnknownSubstitution, nonsenseExon 10Gonzalez et al (2009)
6M33+0OS012138 insC; p.P72fsInheritedInsertion, frameshiftExon 4
7M28++None0c.916C>T; p.R306XUnknownSubstitution, nonsenseExon 8Cornelis et al (1997)
8F24+0Unknown0c.438G>A; p.W146XDe novoSubstitution, nonsenseExon 5
9M19+n/aNone+c.880dup; p.E294fsUnknownDuplication, frameshiftExon 8
10F67+n/aNoneUnknownc.375G>A; p.T125TUnknownAltered splicingExon 4Bougeard et al (2008)
11M40+n/aNoneUnknownIVS376-1 G>AUnknownSplice site mutation
12F120+n/aNoneUnknown
13M75+n/aNoneUnknown
14M43+n/aNone0
15M150+n/aUnknownUnknown

Tumor histology, TP53 germline mutation status, family and personal history of LFS cancers, age at diagnosis, tumor site, International RMS Study Group (IRSG) grouping/staging information, and current clinical outcome were reviewed and recorded. Anaplasia was determined by L.A.T (Table 1, cases 1-15) and G.R.S (Table 1, cases 1-2, 4, 6, 8-15) based on the presence of enlarged hyperchromatic nuclei (at least 3 times the size of neighboring nuclei) with or without atypical mitotic figures.[22, 23] Nuclear staining for TP53 by immunohistochemistry (IHC) was graded as present or absent.

TP53 Mutation Testing

Germline DNA was evaluated for TP53 mutations only. TP53 mutation analysis was performed on genomic DNA extracted from peripheral blood lymphocytes in the clinical CLIA-CAP molecular diagnostic laboratories at both institutions. Germline DNA was collected shortly after diagnosis for 14 of 15 patients (Table 1, cases 1-4 and 6-15) and after the child's third malignant diagnosis for 1 patient (Table 1, case 5). Sequencing of exons 1 through 11 including 20-50 bases into introns and the 5′/3′-untranslated region was performed, in addition to multiplex ligation-dependent probe amplification (MLPA) analysis of gene copy number. All mutations were previously reported in the germline (IARC database, R16, November 2012; Petitjean et al[24]), or predicted aberrant function based on introduction of a termination codon or disruption of a splice site. Mutations were identified as de novo if both parents had normal TP53 germline status. Mutations were identified as inherited if one parent carried the same TP53 germline mutation. Inheritance status was reported as unknown if germline sequencing data on the parents were not available.

Statistics

This study was designed as a retrospective review of a rare pediatric disease. Due to the small sample size, testing for statistical significance was not possible.

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. FUNDING SOURCES
  8. CONFLICT OF INTEREST DISCLOSURES
  9. REFERENCES
  10. Supporting Information

RMS Tumors in TP53 Germline Mutation Carriers Exhibit Anaplastic Histology

To determine whether the presence of TP53 germline mutations correlates with susceptibility to develop RMS with specific histological features, we retrospectively reviewed tumor histology in 8 consecutive patients with RMS and TP53 germline mutations (Table 1, cases 1-8). These 8 children had previously undergone TP53 germline analysis, because they had first- or second degree relatives with cancers of the LFS spectrum (Table 1, cases 1-4), a personal history of multiple LFS cancers (Table 1, case 5) and/or were diagnosed with RMS under the age of 3 years (Table 1, cases 3, 6-8).[11] All 8 tumors exhibited nonalveolar anaplastic morphology (Table 1 and Fig. 1). IHC staining for desmin and myogenin was positive in all tumors (Fig. 1 and data not shown). Nuclear staining for TP53 was positive in ≥ 50% of tumor nuclei in 4 of these tumors (Fig. 1 and Table 1). TP53 staining was absent in the remaining 4 tumors (Table 1). Of note, case 5 (Table 1, Fig. 1B) was originally described as a fusion-negative, solid-variant alveolar RMS in 2002. On re-review by L.A.T, the histological appearance, focal nuclear staining for myogenin, and cytogenetics were most consistent with a diagnosis of nonalveolar RMS. Diffuse anaplasia was present.

image

Figure 1. Histology micrographs show anaplastic rhabdomyosarcoma (anRMS) in TP53 germline mutation carriers. (A) Diffuse anaplasia noted on hematoxylin & eosin (H&E)-stained sections of a RMS in the retroperitoneum of a 34-month-old female TP53 germline mutation carrier (Table 1, case 3). (B) Diffuse anaplasia on H&E-stained sections of a RMS of the lower pelvis in a 50-month-old male TP53 mutation carrier (Table 1, case 5).

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Many Children With anRMS Carry TP53 Germline Mutations

To further evaluate the association of TP53 germline mutations and anRMS, we performed TP53 mutation analysis on genomic DNA obtained from peripheral blood lymphocytes from 7 additional children with anRMS (Table 1, cases 9-15). One of these 7 children had first- and second-degree relatives with LFS cancers (Table 1, case 9). For the remaining 6 children, family history was negative for LFS cancers or not available. Functionally relevant germline mutations at the TP53 locus were detected in 3 of these 7 children (Table 1, cases 9-11). Thus, of 15 children with anRMS included in this study, 11 (73%) had a TP53 germline mutation.

TP53 Germline Mutations in Children With anRMS

TP53 mutations in 6 children with anRMS included in this study comprised single-nucleotide variants (SNVs) in the coding sequence of exons 4, 5, 8, and 10 of human TP53 resulting in nonsense mutations (Table 1, cases 3, 5, 7, 8) or altered splicing (Table 1, cases 2 and 10). SNVs in the non-coding sequence of TP53, resulting in splice site mutations, were observed in 3 patients (Table 1, cases 1, 4, 11). Frameshift mutations in exons 4 and 8 of TP53 were found in 2 patients (Table 1, cases 6 and 9). Aberrations at all 8 mutation sites within the TP53 coding sequence were previously reported in the UMD TP53 database (Table 1, cases 2, 3, 5, 6, 7, 8, 9, 10; http://p53.free.fr/Database/p53_database.html; Soussi et al[25]). Four mutations were previously reported in the Catalogue of Somatic Mutations in Cancer (Table 1, case 3/COSM46163, case 5/COSM306146, case 7/COSM10663, case 8/COSM10727). Six of 11 mutations (Table 1; cases 1, 2, 3, 5, 7, 10) were previously published in patients with LFS.[26-31] The remaining 5 mutations were functionally relevant, because they either encoded a premature termination codon predicting a truncated protein or harbored a mutation predicting disruption of exon splicing.

anRMS in Children With TP53 Germline Mutations Often Presents at a Young Age and May Not Be Associated With LFS Cancers in the Family

Median age at anRMS diagnosis in TP53 germline mutation carriers was 40 months (mean, 40 ± 15 months; range, 19-67 months). Five of 11 TP53 germline mutation carriers were diagnosed with anRMS under the age of 3 years, and the remaining 6 TP53 germline mutation carriers with anRMS were diagnosed between 3 and 7 years of age (Table 2). Thus, all 5 children (100%) diagnosed with anRMS under 3 years, and 6 of 8 children (75%) diagnosed with anRMS between 3 and 7 years of age were TP53 mutation carriers. Two children diagnosed with anRMS between 7 and 13 years of age did not have TP53 germline mutations.

Table 2. Frequency of TP53 Germline Mutations in Children With Anaplastic Rhabdomyosarcoma (anRMS) Based on Age and Family History of LFS Cancers
 Children With anRMS No. (%)Children With anRMS and Mutated TP53 No. (%)
  1. Abbreviations: anRMS, anaplastic rhabdomyosarcoma; LFS, Li-Fraumeni syndrome.

  2. Age at diagnosis was available for review for all 15 children; family history was available for 9 children. Rhabdomyosarcoma was the first malignant diagnosis in all patients. LFS core cancers include soft tissue sarcoma, osteosarcoma, brain tumor, premenopausal breast cancer, adrenocortical carcinoma, leukemia, and lung bronchoalveolar cancer.

Age at diagnosis
0-3 years5 (of 15, 33%)5 (of 5, 100%)
3-7 years8 (of 15, 53%)6 (of 8, 75%)
7-13 years2 (of 15, 13%)0 (of 2, 0%)
Family history in at least one first- or second-degree relative
No LFS cancers5 (of 10, 50%)4 (of 5, 80%)
Any LFS cancers5 (of 10, 50%)5 (of 5, 100%)
LFS core-cancers3 (of 10, 30%)3 (of 3, 100%)

Family history of cancer in first- and second-degree relatives was available for 9 of 11 children with TP53 germline mutations and anRMS (Table 1 and Supporting Table 1; see online supporting information). Five of these children (56%) had at least one first- or second-degree relative with a malignancy on the LFS spectrum, including 3 children with family members with LFS core cancers such as osteosarcoma, glioblastoma, and adrenocortical carcinoma. However, 4 children (36%) with TP53 germline mutations and anRMS did not have any family history of LFS cancers (Table 2). The frequency of germline TP53 mutations in children with anRMS was 100% (5 of 5 children) for those with a family cancer history consistent with Li-Fraumeni syndrome (LFS), and 80% (4 of 5 children) for those without an LFS cancer phenotype.

Current LFS Classification Schemes Do Not Capture All Children With anRMS and TP53 Germline Mutations

Based on family history alone, 3 children in this anRMS cohort fit classic LFS criteria (Table 1 and Supporting Table 1, cases 2 and 9; and Supporting Table 2)[32] or Birch/Eeles criteria for Li-Fraumeni–like syndrome (LFL) (Table 1 and Supporting Table 1, case 1; and Supporting Table 2).[33, 34] Chompret criteria for LFS consider both family and personal history of cancer. Seven children with anRMS and TP53 germline mutations met Chompret criteria at the time of this review (Table 1 and Supporting Table 1, cases 1-6,9; and Supporting Table 2).[19-21] Yet, none of the current LFS classification schemes captured all TP53 germline mutation carriers.

anRMS in TP53 Germline Mutation Carriers Often Present With Group III Tumors at Unfavorable Disease Sites

International RMS Study Group (IRSG) grouping/staging information was available on 9 (stage)/10 (group) germline TP53 mutation carriers in this cohort, and primary tumor site was available on all 11 children (Table 3 and Supporting Table 3). The majority of patients with mutated germline TP53 had IRSG group III tumors (gross residual disease after initial surgical intervention). Distant metastases at diagnosis were only present in one child who carried a TP53 splice site mutation (Table 3, case 1). Seven of 11 anRMS tumors in TP53 germline mutation carriers arose at unfavorable disease sites in the extremities, trunk or parameningeal space (Supporting Table 3).

Table 3. Primary Tumor Site, IRS Group/Stage and Survival of 15 Children With Anaplastic Rhabdomyosarcomaa
Case IDPrimary Tumor SiteIRS Group/StageSurvival
  1. Abbreviations: DOD, dead of disease; DOSM, dead of second malignancy; In Tx, in treatment; IRS, International RMS Study Group; n/a, not available; NED, no evidence of disease.

  2. Cases 1-11 were TP53 germline mutation carriers; cases 12-15 did not have TP53 germline mutations. Two children were undergoing treatment for primary anRMS (case 9) or relapsed anRMS (case 3) at the time of this review.

1ParaspinalGroup IV, stage 4DOD (19 mo)
2Right triceps muscleGroup III, stage 2NED (24 mo)
3RetroperitoneumGroup III, stage 3In Tx (23 mo)
4Oral cavityGroup III, stage 1DOSM (125 mo)
5Lower pelvisGroup III, stage 3NED (123 mo)
6Left gluteus maximusGroup IIIDOSM (128 mo)
7Right thighGroup III, stage 3NED (14 mo)
8Left pterygoid muscleGroup III, stage 3NED (140 mo)
9Right orbitGroup III, stage 1In Tx (1 mo)
10Right masseter musclen/aDOD (62 mo)
11Left chest wallGroup II, stage 2NED (59 mo)
12Left orbitn/aNED (155 mo)
13Right pterygoid muscleGroup III, stage 3DOD (11 mo)
14Right paratesticularGroup I, stage 1NED (39 mo)
15Infratemporal fossan/aDOD (6 mo)

TP53 Germline Mutation Carriers With anRMS Are at Risk for Additional Malignancies

Qualman et al reported 68% 5-year overall survival in pediatric patients with anRMS, and correlated anaplasia with inferior outcome in patients with intermediate-risk embryonal RMS.[23] Of 11 children with anRMS and TP53 germline mutations reported here, 5 children were alive and without evidence of disease at 14 to 155 months after first diagnosis (Table 3 and Supporting Table 3). Yet, 3 TP53 germline mutation carriers with anRMS developed second malignancies typical of the LFS spectrum (including one patient with an osteosarcoma in the radiation field, Table 1, case 5). Two of these children died from their second cancers (Table 3 and Supporting Table 3, cases 4 and 6).

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. FUNDING SOURCES
  8. CONFLICT OF INTEREST DISCLOSURES
  9. REFERENCES
  10. Supporting Information

LFS is an inherited cancer predisposition syndrome characterized by early onset cancers, including but not limited to STS, osteosarcoma, adrenocortical carcinoma, brain tumors and breast carcinoma.[32] The only gene that has been consistently associated with LFS is TP53.[20] Several classification schemes were developed to identify individuals at risk for germline TP53 mutations based on family history of cancer in first- and second-degree relatives.[32-34] More recently, Chompret et al developed criteria that allow for the possibility of a negative family history in individuals with at least 2 LFS spectrum cancers, adrenocortical carcinoma or choroid plexus tumor.[19-21] Adrenocortical carcinoma is considered to be a sentinel cancer in TP53 germline mutation carriers, as the frequency of TP53 germline mutations in 21 children with adrenocortical carcinoma was found to be 67%.[20] We determined that 11 of 15 children with anRMS included in our cohort had TP53 germline mutations. Although adrenocortical carcinomas appeared to be more common in female TP53 germline mutation carriers,[20] 7 of 11 children with anRMS and germline TP53 mutations in this cohort were males (Table 1). Our findings suggest that anRMS represents another sentinel cancer in LFS. If future studies in larger anRMS cohorts confirm these findings, the Chompret criteria for LFS should be extended to include children with anRMS irrespective of family history.

Anaplastic RMS is a distinctive RMS subtype[22, 23] and shares certain histological features with pleomorphic RMS, historically considered a major form of RMS in adults and recently found to account for 19% of RMS in individuals aged > 19 years.[35] Yet, anaplastic histology (the preferred term in the pediatric age group) in children with RMS is rare. Anaplasia was detected in 3% of all cases of RMS studied in the first 3 Intergroup RMS Studies (IRS I-III),[22] and in 13% of RMS included in Intergroup RMS Study Group (IRSG) or COG therapeutic trials from 1995 to 1998.[23] Both studies noted that focal and diffuse patterns of anaplasia were present across the entire RMS spectrum, including alveolar and nonalveolar tumors.[22, 23] In fact, one TP53 germline mutation carrier in this cohort was initially diagnosed with fusion-negative solid-variant alveolar RMS (Table 1, case 5). However, on re-review by LAT, the tumor was reclassified as a nonalveolar tumor with diffuse anaplasia. Thus, all 11 TP53 germline mutation carriers with anRMS included in our cohort had fusion-negative tumors on the nonalveolar spectrum.

TP53 germline mutations were previously linked to both alveolar and nonalveolar RMS, the 2 main RMS subgroups. Many alveolar RMS tumors carry exclusive fusions of the DNA binding domain of the PAX3 or PAX7 genes to the transactivation domain of the Foxo1a gene.[36] TP53 mutations were reported in 2 PAX3:FOXO1a-positive human alveolar RMS cell lines (Rh41 and Rh30),[8, 37] but it is not known if the TP53 mutations in these cell lines originated in the patients' germlines, tumors, or during ex vivo culture. Moreover, Takahashi et al reported TP53 mutations of unknown germline status in 4 alveolar tumors,[38] and Diller et al described a TP53 germline mutation in one child with alveolar RMS.[11] However, the fusion status of these 5 TP53-mutated alveolar tumors was not reported, and we were unable to verify alveolar histology of the case reported by Diller et al,[11] because the pathology specimen could not be retrieved. Future studies are needed to evaluate germline TP53 mutations in children with fusion-positive alveolar RMS and to determine if TP53 germline mutations confer susceptibility to develop human fusion-positive alveolar RMS with or without anaplasia.

Because both anRMS and TP53 germline mutations are rare occurences, it is remarkable that the RMS tumors diagnosed in 11 TP53 germline mutation carriers all exhibit anaplasia. Two lines of evidence in the published literature support the hypothesis that TP53 pathway activation contributes to the biology of anRMS: 1) inactivation of TP53 with or without introduction of oncogenic Kras in skeletal muscle cells results in formation of high-grade pleomorphic RMS in mice[3, 5, 39]; and 2) anaplastic variants of other embryonal tumors (ie, Wilms tumor and medulloblastoma) were previously linked to germline and somatic mutations disrupting the p53 pathway.[17, 18, 40, 41] It is conceivable that early (germline), inactivating TP53 mutations preferentially drive target cells for sarcomatous transformation to assume an anaplastic phenotype, perhaps due to early catastrophic DNA rearrangements as previously reported in medulloblastomas arising in the context of TP53 germline mutations.[41]

Heerema-McKenney et al previously surveyed TP53 staining by IHC in 64 RMS tumors, and reported TP53 positivity in 5% to 50% of tumor nuclei in 10 tumors, and in < 5% of tumor nuclei in 54 tumors.[42] In our cohort, TP53 expression was evaluated by IHC in 8 anRMS tumors arising in TP53 germline mutation carriers (Table 1, cases 1-8). Nuclear TP53 staining was positive in ≥ 50% of tumor cells in 4 tumors arising in children with mutations predicted to stabilize the protein. Absence of TP53 in the remaining 4 tumors correlated with the presence of germline TP53 mutations that predicted a truncated or deleted product. These observations further support that loss of TP53 function contributes importantly to the biology of anRMS.

It is important to note that 4 of 15 children with anRMS included in this cohort did not have TP53 germline mutations. Future studies are needed to investigate the presence of inactivating, somatic mutations in anRMS in children with a wild-type germline TP53 genotype. We also note that, because this study was focused on evaluating TP53 germline mutations in children with anRMS, our findings do not offer insight into the potential contributions of germline mutations in other RMS-relevant genes or into the overall prevalence of pathogenic germline mutations in children with RMS.

Finally, recent efforts to classify other pediatric malignancies such as medulloblastomas into genetically distinct subgroups have identified disease subsets with marked differences in outcome and therapeutic susceptibilities[43]; in a similar fashion, the distinction of TP53-driven anRMS could have clinical implications. In our cohort, 9 of 11 children with TP53 germline mutations and anRMS presented as group III tumors (incomplete resection with gross residual disease) and 7 of 11 arose at unfavorable sites. 5 of 11 TP53 germline mutation carriers with a history of anRMS were alive and without evidence of disease at 14 to 155 months after first diagnosis, but 3 children developed second malignancies (including one patient with an osteosarcoma in the radiation field) and 2 of these died from their second cancers. Extended studies in larger cohorts of patients are needed to define the prevalence, clinical behavior, and specific therapeutic requirements (especially with regards to the use of radiation therapy for local control) of anRMS in TP53 germline mutation carriers.

Early identification of TP53 germline mutations is important, as it may allow for subsequent surveillance and early diagnosis of second malignancies.[44] Here, we report a strong association between germline TP53 mutations and anRMS diagnosed at a young age, and propose considering TP53 mutation screening for children diagnosed with anRMS irrespective of family history. However, in the absence of TP53 germline data on young children diagnosed with nonanaplastic RMS, our findings do not support changes in existing TP53 mutation screening recommendations for young children diagnosed with any type of RMS under the age of 3 years. Extended studies will be needed to define the specific role of TP53, both in the germline and at a somatic level, in anRMS.

FUNDING SOURCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. FUNDING SOURCES
  8. CONFLICT OF INTEREST DISCLOSURES
  9. REFERENCES
  10. Supporting Information

The authors declare no competing financial interests. This work was supported in part by a grant from the Canadian Institutes of Health Research (MOP106639) (DM), by the SickKids Foundation (DM), by a SARC-SPORE career development award (SH) and by a Stand Up To Cancer-American Association for Cancer Research Innovative Research Grant, grant number SU2C-AACR-IRG1111 (AJW). AJW is an Early Career Scientist of the Howard Hughes Medical Institute. Content is solely the responsibility of the authors and does not necessarily represent the official views of the funding sources.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. FUNDING SOURCES
  8. CONFLICT OF INTEREST DISCLOSURES
  9. REFERENCES
  10. Supporting Information

Supporting Information

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. FUNDING SOURCES
  8. CONFLICT OF INTEREST DISCLOSURES
  9. REFERENCES
  10. Supporting Information

Additional Supporting Information may be found in the online version of this article.

FilenameFormatSizeDescription
cncr28507-sup-0001-SuppTables.pdf12KSupporting Information Tables 1-3.
cncr28507-sup-0001-SuppTables.txt3KSupporting Information

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