Inherited germline TP53 mutation encodes a protein with an aberrant C-terminal motif in a case of pediatric adrenocortical tumor

A first report of a rare TP53 variant associated with Li-Fraumeni syndrome manifesting as invasive breast cancer and malignant solitary fibrous tumor

Background

Li-Fraumeni is a rare autosomal dominant cancer predisposition syndrome. The basis is a germline mutation of TP53 gene which encodes tumor suppressor protein resulting in early onset of tumors, most often breast cancer, soft tissue sarcomas, brain tumors, adrenocortical carcinomas, and leukemia.

Case report

We present a case of a young woman with a positive family history for cancer diagnosed with malignant solitary fibrous tumor and luminal B-like invasive breast cancer. Breast cancer and sarcomas account for the majority of tumors associated with Li-Fraumeni syndrome, yet solitary fibrous tumor is a rare clinical entity with no established guidelines for treatment. Even though both primary tumors were successfully resected, the sarcoma relapsed in the form of lung metastases. The NGS analysis revealed single nucleotide variant (c.1101-1G>A) in TP53 gene, affecting the acceptor splice site at intron 10. Until now, only one case of this genetic variant has been documented with conflicting interpretations of pathogenicity.

Conclusions

The knowledge of TP53 mutation status is essential since the management of these patients requires different approach to avoid excessive toxicity due to the risk of developing secondary malignancy. Using the clinical criteria to screen for affected individuals facilitates appropriate early genetic counseling of patients and their families. Following the American College of Medical Genetics criteria, we believe that the reported single nucleotide variant (c.1101-1G>A) in TP53 gene should be considered pathogenic.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-021-02370-8.

Perspectives in Pediatric Pathology, Chapter 22. Testicular Involvement in Systemic Diseases

Normal testicular physiology requires appropriate function of endocrine glands and other tissues. Testicular lesions have been described in disorders involving the hypothalamus-hypophysis, thyroid glands, adrenal glands, pancreas, liver, kidney, and gastrointestinal tract. Testicular abnormalities can also associate with chronic anemia, obesity, and neoplasia. Although many of the disorders that affect the above-mentioned glands and tissues are congenital, acquired lesions may result in hypogonadism in children and adolescents.

TERT promoter mutations and prognosis in solitary fibrous tumor

Solitary fibrous tumor is a mesenchymal neoplasm exhibiting a broad spectrum of biological behavior and harboring the NAB2-STAT6 fusion. Clinicopathologic parameters are currently used in risk-prediction models for solitary fibrous tumor, but the molecular determinants of malignancy in solitary fibrous tumors remain unknown. We proposed that the activation of telomere maintenance pathways confers a perpetual malignant phenotype to these tumors. Therefore, we investigated telomerase reverse transcriptase (TERT) reactivation induced by promoter mutations as a potential molecular mechanism for aggressive clinical behavior in solitary fibrous tumor. The retrospective study included tumor samples from 94 patients with solitary fibrous tumor (31 thoracic and 63 extra-thoracic). Follow-up information was available for 68 patients (median, 46 months). TERT promoter mutation analysis was performed by PCR and Sanger sequencing, and TERT mRNA expression was assessed by real-time quantitative reverse transcription PCR. Patients were stratified into clinicopathologic subgroups (high-risk (n=20), moderate-risk (n=28), and low-risk (n=46)) according to the risk-stratification model proposed by Demicco et al. TERT promoter mutations were identified in 26 of 94 (28%) solitary fibrous tumors: -124C>T in 23 tumors (88%), -124C>A in 1 tumor (4%), and -146C>T in 2 tumors (8%). Real-time quantitative reverse transcription PCR revealed that TERT mRNA expression was higher in all solitary fibrous tumors with the mutant TERT promoter than those with the wild-type TERT promoter. TERT promoter mutations were strongly associated with high-risk clinicopathologic characteristics and outcome. An adverse event (relapse, death) occurred in 16 of 68 (24%) patients, 12 with solitary fibrous tumors with TERT promoter mutations and 4 with the wild-type TERT promoter. TERT promoter mutations were strongly associated with older age (P=0.006), larger tumor size (P=0.000002), higher risk classifications (P=2.9 × 10^-9), and a worse event-free survival (P=0.0082). Thus, TERT promoter mutations in solitary fibrous tumor influence gene expression and are associated with adverse patient outcome. Integrating TERT promoter mutational status with existing multivariable risk-prediction models might improve risk prediction in patients with solitary fibrous tumor.

The dark matter of the cancer genome: aberrations in regulatory elements, untranslated regions, splice sites, non-coding RNA and synonymous mutations

Cancer is a disease of the genome caused by oncogene activation and tumor suppressor gene inhibition. Deep sequencing studies including large consortia such as TCGA and ICGC identified numerous tumor‐specific mutations not only in protein‐coding sequences but also in non‐coding sequences. Although 98% of the genome is not translated into proteins, most studies have neglected the information hidden in this “dark matter” of the genome. Malignancy‐driving mutations can occur in all genetic elements outside the coding region, namely in enhancer, silencer, insulator, and promoter as well as in 5′‐UTR and 3′‐UTR. Intron or splice site mutations can alter the splicing pattern. Moreover, cancer genomes contain mutations within non‐coding RNA, such as microRNA, lncRNA, and lincRNA. A synonymous mutation changes the coding region in the DNA and RNA but not the protein sequence. Importantly, oncogenes such as TERT or miR‐21 as well as tumor suppressor genes such as TP53/p53,APC,BRCA1, or RB1 can be affected by these alterations. In summary, coding‐independent mutations can affect gene regulation from transcription, splicing, mRNA stability to translation, and hence, this largely neglected area needs functional studies to elucidate the mechanisms underlying tumorigenesis. This review will focus on the important role and novel mechanisms of these non‐coding or allegedly silent mutations in tumorigenesis.

Splice-acceptor site mutation in p53 gene of hu888 zebrafish line

The p53 transcription factor is a key tumor suppressor and a central regulator of the stress response, which has been a subject of intense research for over 30 years. Recently, a zebrafish line which carries splice site mutation (G>T) in intron 8 of p53 gene (p53^hu888), encoding the p53 paralogue, was developed (The Zebrafish Mutation Project). To uncover molecular effects of the mutation, we raised hu888 zebrafish line to adulthood and analyzed DNA, mRNA data, and protein levels of p53 to assess their potential contribution in molecular mechanisms of the mutant fish. To obtain zebrafish individuals homozygous for the point mutation, p53^hu888 carriers were repeatedly incrossed but only heterozygous mutants (p53^hu888/+) or p53-wild type hu888 zebrafish (p53^+/+) were identified in their progeny. By evaluation of p53 expression changes in the liver of mutant and wild type hu888 zebrafish as well as of Tübingen reference strain, we demonstrated that two types of splicing occurred in each case: a classical one and the alternative splicing which involves the activation of cryptic splice-acceptor site in the exon 9 of zebrafish p53 pre-mRNA. The alternative splicing event results in a deletion 12 nucleotides in the mature mRNA, and produces a shortened variant of p53 protein. Interestingly, expression of p53 protein in liver of both heterozygous and wild type hu888 zebrafish was highly reduced compared to that in the reference strain.

Pediatric adrenocortical tumors: diagnosis, management and advancements in the understanding of the genetic basis and therapeutic implications

Adrenocortical tumors (ACTs) may be sporadic or related to inherited genetic syndromes. Uncovering the molecular defects underlying these genetic syndromes has revealed key signaling pathways involved in adrenocortical tumorigenesis. Although the understanding of ACT biology has improved, to date, very few potential prognostic molecular markers of childhood ACTs have been identified. In this review, we summarize the current knowledge of the epidemiology, clinical presentation, diagnosis, prognosis and treatment options for pediatric patients with ACTs. A review of the genetic basis of adrenocortical tumorigenesis is presented, focusing on the main molecular abnormalities involved in the tumorigenic process and potential novel therapy targets that have been generated, or are being generated, with the discovery of these molecular defects.

A differential diagnosis of inherited endocrine tumors and their tumor counterparts

Inherited endocrine tumors have been increasingly recognized in clinical practice, although some difficulties still exist in differentiating these conditions from their sporadic endocrine tumor counterparts. Here, we list the 12 main topics that could add helpful information and clues for performing an early differential diagnosis to distinguish between these conditions. The early diagnosis of patients with inherited endocrine tumors may be performed either clinically or by mutation analysis in at-risk individuals. Early detection usually has a large impact in tumor management, allowing preventive clinical or surgical therapy in most cases. Advice for the clinical and surgical management of inherited endocrine tumors is also discussed. In addition, recent clinical and genetic advances for 17 different forms of inherited endocrine tumors are briefly reviewed.

Functional studies of a novel germline p53 splicing mutation identified in a patient with Li-Fraumeni-like syndrome

Most p53 mutations identified in Li-Fraumeni syndrome (LFS) are missense mutations; splicing mutations have rarely been reported. A novel splicing p53 mutation was identified in a patient with Li-Fraumeni-like syndrome (LFL). Usually, p53 missense mutants identified in LFS and cancer cells function as dominant negative mutations interfering with wild-type p53 function. However, the mechanism by which p53 haploinsufficiency causes carcinogenesis is not well characterized. In this study, we describe a novel splicing mutation that results in the loss-of-function of p53. These findings suggest a linkage between the loss-of-function type p53 mutation and a LFL phenotype.

Towards an understanding of the role of p53 in adrenocortical carcinogenesis

Adrenocortical carcinoma (ACC) is recognized to be a component tumor of the Li Fraumeni Syndrome (LFS), a familial cancer predisposition resulting from germline mutations in the p53 tumor-suppressor. p53 activity is tightly regulated by multiple post-translational mechanisms, disruption of which may lead to tumorigenesis. ACC is present in disproportionately high rates among p53-mutation carriers, suggesting tissue-specific manifestations of p53 deficiency. Additionally, p53-associated ACC demonstrates a strong predominance in infants and children. Several of the p53 alleles associated with pediatric ACC, however, retain significant wild-type activity and demonstrate incomplete penetrance, a finding distinct from other LFS-component tumors. In this review, we discuss the relationship between p53 and adrenocortical carcinogenesis, with specific focus on disease-specific alleles, tumorigenesis in the context of adrenal development and potential therapeutic approaches to p53-associated ACC.

TP53-Associated Pediatric Malignancies

Although the majority of pediatric malignancies express wild-type p53, it is well established that germline TP53 mutations or functional inactivation of this pathway by other means contribute to childhood cancer. Epidemiology studies have revealed the existence of diverse inherited mutant TP53 alleles that display different levels of tumor suppressor activity, which correlate with cancer risk in terms of penetrance, age of onset, and tumor types. In this monograph, the authors describe those childhood cancers associated with functional inactivation of TP53 focusing on adrenocortical carcinoma as a model for tissues that are highly sensitive to loss of p53 activity.