Mutations In Tumor Suppressor Gene Research Articles

Gαs (GNAS) suppression of the p53 genomic‐stability checkpoint unleashes RAS‐driven oncogenesis

As one of the most frequently mutated oncogenes, mutant RAS has been well established to drive proliferative cell programs that are exploited by cancer. Interestingly, RAS, like many oncogenes, has been found in benign tumors that never progress to cancer. Although seemingly counterintuitive, RAS mutant tumors require an additional mutational insult to progress to malignancy. Using an unbiased, pan‐cancer analysis from patient sequencing data, we discovered that RAS mutations significantly co‐occur with mutations in GNAS, the gene encoding the Gαs subunit of G protein couple receptors (GPCRs). Given the established tractability of GPCRs as drug targets, we aimed to explore GNAS as a potential co‐driver in RAS mutant cancers. To first validate the ability of mutations in RAS and GNAS to cooperate to induce malignancy, we expressed the constitutive active mutations, KRASG12D and GNASR201C in the skin of adult mice. These double mutant mice rapidly developed skin papillomas, while mice with either mutation alone had no phenotype. Furthermore, when GNASR201C mice were treated with the chemical carcinogen DMBA, known to induce Hras mutations, mice rapidly developed squamous cell carcinoma in only 3 weeks. Analysis of the lesions revealed a surprising lack of mutations in the Trp53 tumor suppressor gene, which controls genomic stability. In vitro experiments revealed that activation of signaling through Gαs, or its downstream kinase PKA, was sufficient to block DNA damage‐induced p53 protein accumulation. Analysis of the underlying mechanisms demonstrated that MDM2, the cognate p53 E3 ubiquitin ligase, is a direct substrate of PKA, which phosphorylates MDM2 on S166 resulting in enhanced ligase activity. In vitro ubiquitination assays revealed that activation of Gαs or PKA increased MDM2‐mediated p53 ubiquitination and degradation. In patients, appendix cancer is the best example of the GNAS‐KRAS co‐driver state, with 70% of patients harboring this co‐mutation. Ongoing experiments are aimed at validating the mechanism of Gαs‐PKA regulation of MDM2‐p53 growth checkpoints in relevant murine and human intestinal organoid models. In summary, we have uncovered a significant co‐occurrence of RAS and GNAS mutations in cancer and demonstrated that these mutations cooperate to initiate carcinogenesis in vivo. Mechanistically, the cooperation of RAS and GNAS can be explained by the ability of Gαs to functionally repress p53, through PKA mediated phosphorylation of MDM2, releasing the normal brakes that check aberrant RAS‐driven growth.Support or Funding InformationDana Steffen was supported by the National Science Foundation Graduate Research Fellowship Program (NSF GRFP) and the UCSD Graduate Training Program in Cellular and Molecular Pharmacology through an institutional training grant from the National Institute of General Medical Sciences (T32 GM007752). This study is supported in part by the San Diego NCI Cancer Centers Council (C3) Collaborative Translational Cancer Research Pilot Grant.

Therapy of Sporadic and NF2-Related Vestibular Schwannoma.

Vestibular schwannoma (VS) is a benign primary brain tumor that occurs sporadic or as part of a genetic syndrome. The most common cause is the mutation of the NF2 tumor suppressor gene that is involved in the production of the protein merlin. Merlin plays a role in cell growth and cell adhesion. In patients with NF2, the VSs arise bilaterally and coincide with other brain tumors. In sporadic VS, the tumor is typically unilateral and does not coincide in combination with other tumors. MRI is the standard imaging technique and can be used to assess the size and aspect of the tumor as well as the progression of disease. The preferred management of large VS in both VS types is surgery with or without adjuvant radiation. The management for the medium- or small-sized VS includes wait and scan, radiotherapy and/or surgery. This choice depends on the preference of the patient and institutional protocols. The outcomes of surgical and radiotherapy treatments are improving due to progress in surgical equipment/approaches, advances in radiation delivery techniques and dose optimizations protocols. The main purpose of the management of VS is preserving function as long as possible in combination with tumor control.

The first pancreatic neuroendocrine tumor in Li-Fraumeni syndrome: a case report

BackgroundLi-Fraumeni syndrome is a cancer predisposition syndrome caused by germline TP53 tumor suppressor gene mutations, with no previous association with pancreatic neuroendocrine tumors (PNETs). Here we present the first case of PNET associated with Li-Fraumeni syndrome.Case presentationThis is a 43-year-old female who underwent laparoscopic distal pancreatectomy at age 39 for a well-differentiated grade 2 cystic PNET. When the patient was 41 years old, her seven-year-old daughter was found to have an astrocytoma and a germline TP53 mutation. While undergoing surveillance with 68Gallium-DOTATATE positron emission tomography/computed tomography for her PNET, the patient was found to have a large choroid plexus papilloma in her right temporal lobe. She underwent genetic counseling and testing that identified a germline pathogenic variant in TP53, leading to the diagnosis of Li-Fraumeni syndrome. Her PNET had a hemizygous pathogenic TP53 mutation with loss of the wild-type alternate allele, consistent with loss of heterozygosity and the two-hit hypothesis. She was enrolled in a Li-Fraumeni syndrome protocol and continues surveillance screening with our service.ConclusionsThis is the first PNET reported in association with Li-Fraumeni syndrome. Pancreatic cancer risk is elevated in this syndrome, and our case highlights the need for vigilance in screening for pancreatic neoplasms in these patients.

Tumor renal de células claras como debut de la enfermedad de Von Hippel-Lindau: reporte de caso

Antecedentes: La enfermedad de Von Hippel Lindau se debe a mutaciones del gen VHL (un supresor tumoral) que provoca aparición de distintas neoplasias en sistema nervioso central, ojo y abdomen. Su incidencia es baja y su importancia estriba en que el carcinoma renal de células claras representa la entidad con mayor tasa de letalidad en pacientes afectados por esta enfermedad.
 Caso clínico: Femenino de 45 años que presenta múltiples antecedentes familiares de neoplasias del sistema nervioso central y abdomen, que acude por aparición de tumoración abdominal. Se corrobora por imagen una neoplasia renal por lo que se somete a nefrectomía radical izquierda y se confirma el diagnóstico de carcinoma renal de células claras. En su abordaje posterior se integra el diagnóstico de Enfermedad de Von Hippel Lindau tipo I.
 Conclusiones: La enfermedad de Von Hippel Lindau presenta diversas manifestaciones neoplásicas de las cuales el carcinoma renal de células claras representa la entidad con mayor morbimortalidad, por lo que su detección temprana cuando existen antecedentes familiares es esencial para mejorar el pronóstico y diagnosticar a tiempo otras neoplasias vistas en la enfermedad.

Clear cell renal cell carcinoma detection leading to von Hippel-Lindau disease diagnosis: A case report

Background: Von Hippel-Lindau disease is caused by mutations of the VHL tumor-suppressor gene and results in the development of different neoplasias in the central nervous system, eye, and abdomen. Its incidence is low, but patients that develop clear cell renal cell carcinoma have the highest mortality rate. 
 Clinical case: A 45-year-old woman, with a family history of central nervous system and abdominal neoplasias, sought medical attention due to a progressively growing mass in the left flank. A kidney tumor was corroborated through an imaging study, and she underwent left radical nephrectomy. The diagnosis of clear cell renal cell carcinoma was confirmed. In the subsequent approach, she was also diagnosed with von Hippel-Lindau type I disease. 
 Conclusions: Von Hippel-Lindau disease presents with different neoplastic manifestations, and that of clear cell renal cell carcinoma has the highest morbidity and mortality rates. When there is a family history, its early detection is essential for improving outcome and opportunely diagnosing other neoplasias resulting from the disease.

Changes in the genetic landscape during the malignization of high grade squamous intraepithelial lesion into cervical cancer

In 5 patients, a change in the genetic landscape from HPV16 positive high-grade squamous intraepithelial lesion (HSIL) to squamous cervical cancer was traced, which occurred in these patients within the period from 7 months to 5 years after diagnosing HSIL. Materials and Methods: The DNA from paraffin blocks of dysplasia tissue and the tumor that emerged afterwards was used for the study, which was analyzed using the OncoScan FFPE microarray Assay Kit Affymetrix (USA) for genome-wide determination of gene abundance and 65 key somatic driver mutations of oncogenes and tumor suppressor genes. Results: In the study of HSIL material, somatic mutations were observed in 4/5 cases, 18 different somatic driver mutations of the NRAS, EGFR, BRAF, KRAS, IDH2 oncogenes and TP53 suppressor genes were found and almost no CNA-Copy Number Aberration was identified. HSIL malignization is associated with the appearance of secondary driver mutations in oncogenes and tumor suppressor genes and a large number of structural and numerical CNA, the frequency of which correlates with the time of dysplasia malignization into cancer with a very high correlation coefficient r = 0.98, P = 0.004. The trees of dysplasia evolution into tumor were constructed for each patient. Conclusion: According to the results of the work, it is assumed that the initiation of the development of mucosa dysplastic changes is due to primary driver mutations. The formation of secondary driver mutations and CNA are genetic mechanisms of malignant transformation, while the scenarios of the evolution of dysplasia into a tumor are individual and very diverse.

P.L105Vfs mutation in a family with thymic neuroendocrine tumor combined with MEN1: a case report

BackgroundMultiple endocrine neoplasia type 1 (MEN1) is a rare autosomal dominant disorder arising from mutations of the MEN1 tumor suppressor gene on chromosome 11q13; MEN1 is characterized by the development of neuroendocrine tumors, including those of the parathyroid, gastrointestinal endocrine tissue and anterior pituitary. Additionally, thymic neuroendocrine tumors in MEN1 are also rarely reported.Case presentationThis case report observed a family that presented with MEN1 p.L105Vfs mutation, and two of the family members had been diagnosed with thymic neuroendocrine tumor combined with MEN1. To the best of our knowledge, this is the first time such a mutation in the MEN1 gene has been reported. The proband presented with thymic neuroendocrine tumor, parathyroid adenoma and rectum adenocarcinoma. The son of the proband presented with thymic neuroendocrine tumor, gastrinoma, hypophysoma and parathyroid adenoma. Genetic testing revealed the frameshift mutation p.L105Vfs, leading to the identification of one carrier in the pedigree (the patient’s younger sister). The proband then underwent parathyroidectomy at the age of 26 years (in 1980) for a parathyroid adenoma. Subsequently, the patient underwent thymectomy, radiotherapy and chemotherapy. The patient is now 64 years old, still alive and still undergoing Lanreotide therapy.ConclusionThymic neuroendocrine MEN1 is rare, but it accounts for almost 20% of MEN1-associated mortality. Consequently, we should focus on regular clinical screening of the thymus in MEN1 patients.

Mechanisms of Hippo pathway in the pancreatic cancer

Abstract Pancreatic ductal adenocarcinoma (PDAC) is a lethal, aggressive, and incurable disease. The patients with PDAC are often diagnosed at the advanced stage, leading to poor overall survival because of no current effective treatment. Further exploration of the mechanism is needed urgently to provide insights on the prevention, detection, or intervention of pancreatic cancer. Oncogenic KRAS and mutated tumor suppressor genes serve essential roles in PDAC tumorigenesis. Different groups of scientists indicated that yes-associated protein and transcriptional coactivator with PDZ-binding motif, which are the main effectors of the Hippo pathway, are the center in the development of PDAC. Here, we will focus on the recent advances of the molecular mechanisms of core components in the Hippo kinases cascade and discuss their clinical implications.

HEREDITARY PITUITARY TUMOR SYNDROMES: GENETIC AND CLINICAL ASPECTS.

The pituitary gland is responsible for the synthesis and secretion of various hormones that play a key role in regulating endocrine function and homeostasis. Pituitary adenomas (PA) are benign epithelial tumors arising from the endocrine cells of the anterior pituitary gland. Clinically relevant PA are relatively common and they occur in 0.1% of the general population. They are mostly benign monoclonal neoplasms that arise from any of the five hormone-secreting cell types of the anterior pituitary gland. PA are categorized as either functioning or non-functioning, depending on whether or not they produce a hormonal hypersecretion syndrome. Both functioning and non-functioning adenomas can produce symptoms or signs resulting from compression of the optic chiasm or invasion of cavernous sinuses. Only 5% of PA occur within the context of hereditary syndromes with reasonably well-defined oncogenic mechanisms. The vast majority of PA are sporadic, and their etiopathogenesis remains largely unknown. Pituitary tumor oncogenesis involves several mechanisms that eventually lead to abnormal cell proliferation and dysregulated hormone production. Among these factors, we found inactivating mutations of tumor suppressor genes, activating mutation of oncogenes and the participation of hormonal signals coming from the hypothalamus, all resulting in cell-cycle regulation abnormalities. In this review, we summarize the clinical and pathophysiological aspects of the different hereditary pituitary tumor syndromes.

MYCN amplification and ATRX mutations are incompatible in neuroblastoma

Aggressive cancers often have activating mutations in growth-controlling oncogenes and inactivating mutations in tumor-suppressor genes. In neuroblastoma, amplification of the MYCN oncogene and inactivation of the ATRX tumor-suppressor gene correlate with high-risk disease and poor prognosis. Here we show that ATRX mutations and MYCN amplification are mutually exclusive across all ages and stages in neuroblastoma. Using human cell lines and mouse models, we found that elevated MYCN expression and ATRX mutations are incompatible. Elevated MYCN levels promote metabolic reprogramming, mitochondrial dysfunction, reactive-oxygen species generation, and DNA-replicative stress. The combination of replicative stress caused by defects in the ATRX–histone chaperone complex, and that induced by MYCN-mediated metabolic reprogramming, leads to synthetic lethality. Therefore, ATRX and MYCN represent an unusual example, where inactivation of a tumor-suppressor gene and activation of an oncogene are incompatible. This synthetic lethality may eventually be exploited to improve outcomes for patients with high-risk neuroblastoma.

Prognosis, Biology, and Targeting of TP53 Dysregulation in Multiple Myeloma.

Multiple myeloma (MM) is the second most common hematological cancer and is characterized by genetic features including translocations, chromosomal copy number aberrations, and mutations in key oncogene and tumor suppressor genes. Dysregulation of the tumor suppressor TP53 is important in the pathogenesis of many cancers, including MM. In newly-diagnosed MM patients, TP53 dysregulation occurs in three subsets: monoallelic deletion as part of deletion of chromosome 17p (del17p) (~8%), monoallelic mutations (~6%), and biallelic inactivation (~4%). Del17p is an established high-risk feature in MM and is included in current disease staging criteria. Biallelic inactivation and mutation have also been reported in MM patients but are not yet included in disease staging criteria for high-risk disease. Emerging clinical and genomics data suggest that the biology of high-risk disease is complex, and so far, traditional drug development efforts to target dysregulated TP53 have not been successful. Here we review the TP53 dysregulation literature in cancer and in MM, including the three segments of TP53 dysregulation observed in MM patients. We propose a reverse translational approach to identify novel targets and disease drivers from TP53 dysregulated patients to address the unmet medical need in this setting.

Gorlin-like phenotype in a patient with a PTCH2 variant of uncertain significance

Gorlin syndrome, also known as Nevoid Basal-Cell Carcinoma Syndrome (NBCCS), is an autosomal dominant tumor predisposition syndrome that presents early in life with characteristic congenital malformations and tumors. This syndrome most commonly results from germline mutations of the PTCH1 tumor suppressor gene, which shows high penetrance and great intra and interfamilial phenotypic variability, as well as the SUFU tumor suppressor gene. Recently, the PTCH2 gene has also been implicated as a cause of Gorlin syndrome. Notably, these patients displayed milder phenotypes of Gorlin syndrome when considered against PTCH1 and SUFU-related disease. We report a patient with a novel PTCH2 mutation inherited from his father. The proband displays several minor diagnostic features of Gorlin syndrome, supporting the pathogenic role of this gene. Features in the proband include macrocephaly, a wide face, prominent forehead, hypertelorism/telecanthus, large eyes, cleft lip and palate, thin vertical palmar creases, penoscrotal inversion, and a hyperpigmented spot on his penis. His father displays macrocephaly, several nevi on his back and shoulders, and a single palmar pit on his left hand, raising suspicion for Gorlin syndrome. Whole exome sequence (trio) found that the proband and father are heterozygous for NM_003738.4:c.3347C>T;p.(Pro1116Leu) in exon 21 of PTCH2, found also in his mildly affected brother. This semi-conservative amino acid substitution has been reported in the literature, but its significance is unclear. Notably, the proband, brother, and father do not meet clinical criteria for Gorlin syndrome. However, the clinical findings described in this family support the association between PTCH2 mutations and Gorlin-like phenotypes.

S100A11/ANXA2 belongs to a tumour suppressor/oncogene network deregulated early with steatosis and involved in inflammation and hepatocellular carcinoma development

ObjectiveHepatocellular carcinoma (HCC) development occurs with non-alcoholic fatty liver disease (NAFLD) in the absence of cirrhosis and with an increasing incidence due to the obesity pandemic. Mutations of tumour suppressor...

In Vitro Establishment of a Genetically Engineered Murine Head and Neck Cancer Cell Line using an Adeno-Associated Virus-Cas9 System.

The use of primary normal epithelial cells makes it possible to reproducibly induce genomic alterations required for cellular transformation by introducing specific mutations in oncogenes and tumor suppressor genes, using clustered regulatory interspaced short palindromic repeat (CRISPR)-based genome editing technology in mice. This technology allows us to accurately mimic the genetic changes that occur in human cancers using mice. By genetically transforming murine primary cells, we can better study cancer development, progression, treatment, and diagnosis. In this study, we used Cre-inducible Cas9 mouse tongue epithelial cells to enable genome editing using adeno-associated virus (AAV) in vitro. Specifically, by altering KRAS, p53, and APC in normal tongue epithelial cells, we generated a murine head and neck cancer (HNC) cell line in vitro,which is tumorigenic in syngeneic mice. The method presented here describes in detail how to generate HNC cell lines with specific genomic alterations and explains their suitability for predicting tumor progression in syngeneic mice. We envision that this promising method will be informative and useful to study tumor biology and therapy of HNC.

Centenarian Exomes as a Tool for Evaluating the Clinical Relevance of Germline Tumor Suppressor Mutations.

Objectives:The aim of the present study was to evaluate the clinical relevance of mutations in tumor suppressor genes using whole-exome sequencing data from centenarians and young healthy individuals.Methods:Two pools, one of centenarians and one of young individuals, were constructed and whole-exome sequencing was performed. We examined the whole-exome sequencing data of Bulgarian individuals for carriership of tumor suppressor gene variants.Results:Of all variants annotated in both pools, 5080 (0.06%) are variants in tumor suppressor genes but only 46 show significant difference in allele frequencies between the two studied groups. Four variants (0.004%) are pathogenic/risk factors according to single nucleotide polymorphism database: rs1566734 in PTPRJ, rs861539 in XRCC3, rs203462 in AKAP10, and rs486907 in RNASEL.Discussion:Based on their high minor allele frequencies and presence in the centenarian group, we could reclassify them from pathogenic/risk factors to benign. Our study shows that centenarian exomes can be used for re-evaluating the clinically uncertain variants.

Neurodegenerative diseases and cancer: sharing common mechanisms in complex interactions.

Several epidemiological studies support low cancer rates in patients with neurodegenerative disorders, including Parkinson's disease, Huntington's disease, and Alzheimer's disease. Different mechanisms were raised as possible causes, from mutated tumor suppressor genes (PARKIN, PINK1) to small interfering RNA based on the CAG trinucleotide repeat expansions located in introns or untranslated regions. However, as every rule has an exception, some tumors have an increased incidence in these neurodegenerative diseases such as breast and skin cancer (melanoma). This mini-review aims to establish the epidemiology between these neurodegenerative disorders and cancer to determine the possible mechanisms involved and therefore set eventual therapeutic applications. According to our findings, we conclude the presence of an inverse relationship among most cancers and the aforementioned neurodegenerative disorders. However, this concept needs to be considered cautiously considering specific genetic and extra-genetic linkage factors for particular tumors.

ACB-PCR Quantification of Low-Frequency Hotspot Cancer-Driver Mutations.

Allele-specific competitive blocker PCR (ACB-PCR) is a sensitive and quantitative approach for the selective amplification of a specific base substitution. Using the ACB-PCR technique, hotspot cancer-driver mutations (tumor-relevant mutations in oncogenes and tumor suppressor genes, which confer a selective growth advantage) are being developed as quantitative biomarkers of cancer risk. ACB-PCR employs a mutant-specific primer (with a 3'-penultimate mismatch relative to the mutant DNA sequence, but a double 3'-terminal mismatch relative to the wild-type DNA sequence) to selectively amplify rare mutant DNA molecules. A blocker primer having a non-extendable 3'-end and a 3'-penultimate mismatch relative to the wild-type DNA sequence, but a double 3'-terminal mismatch relative to the mutant DNA sequence is included in ACB-PCR to selectively repress amplification from abundant wild-type molecules. Consequently, ACB-PCR can quantify the level of a single base pair substitution mutation in a DNA population when present at a mutant:wild-type ratio of 1×10-5 or greater. Quantification of rare mutant alleles is achieved by parallel analysis of unknown samples and mutant fraction (MF) standards (defined mixtures of mutant and wild-type DNA sequences). The ability to quantify specific mutations with known association to cancer has several important applications in evaluating the carcinogenic potential of chemical exposures in rodent models. Further, the measurement of cancer-driver mutant subpopulations is important for precision cancer treatment (selecting the most appropriate targeted therapy and predicting the development of therapeutic resistance). This chapter provides a step-by-step description of the ACB-PCR methodology as it has been used to measure human PIK3CA codon 1047, CAT→CGT (H1047R) mutation.

Biochemical and structural analyses reveal that the tumor suppressor neurofibromin (NF1) forms a high-affinity dimer

Biochemical and structural analyses reveal that the tumor suppressor neurofibromin (NF1) forms a high-affinity dimer

Tuberous Sclerosis Complex : A Case Report

Tuberous Sclerosis Complex (TSC) is an autosomal dominant inherited neurocutaneous disorder. Tuberous Sclerosis Complex is caused by mutations in tumor suppressor gene (TSC), both TSC1 and TSC2. In approximately two-thirds of cases neither parent has signs of TSC and the disease is caused by a de novo mutation. Tuberous Sclerosis Complex is classically identified by the Vort's triad in the presence of angiofibroma, mental retardation, and epilepsy. A 17-year-old woman with a major complaint of a facial bump that appeared at birth and got bigger when she reached puberty. There are white patches on the patient's body from birth. On the scalp obtained the presence of skin color plaque, while at the back and right knee obtained shagreen patch. Patientwas diagnosed with epilepsy and mental retardation by the pediatric department. No family history has the same complaints as patient. Histopathologic examination of facial bumps taken by shaving biopsy suggests the presence of hemangiomas. Based on the clinical diagnostic criteria from International Tuberous Sclerosis Complex Consensus Conference 2012, the patient meets two major criteria, macular hypopigmentation and shagreen patch so it is included in "definite diagnosis".

CANCER GENE MUTATION PROFILING IN CALCIFYING EPITHELIAL ODONTOGENIC TUMOR

Objective To identify in calcifying epithelial odontogenic tumor (CEOT) mutations in oncogenes and tumor suppressor genes. Study Design A panel of 50 genes commonly mutated in cancer was sequenced in CEOT by next-generation sequencing. Sanger sequencing was used to cover the region of the frameshift deletion identified in one sample. Results Missense single nucleotide variants (SNV) with minor allele frequency (MAF) 1%. Conclusions CEOT harbor mutations in the tumor suppressor PTEN and CDKN2A and in the oncogenes JAK3 and MET. As these mutations occurred in only 1 case each, they are probably not driver mutations for these tumors.