Germline PTEN Research Articles

A Saturation Mutagenesis Approach to Understanding PTEN Lipid Phosphatase Activity and Genotype-Phenotype Relationships

Phosphatase and tensin homolog (PTEN) is a tumor suppressor frequently mutated in diverse cancers. Germline PTEN mutations are also associated with a range of clinical outcomes, including PTEN hamartoma tumor syndrome (PHTS) and autism spectrum disorder (ASD). To empower new insights into PTEN function and clinically relevant genotype-phenotype relationships, we systematically evaluated the effect of PTEN mutations on lipid phosphatase activity invivo. Using a massively parallel approach that leverages an artificial humanized yeast model, we derived high-confidence estimates of functional impact for 7,244 single amino acid PTEN variants (86% of possible). We identified 2,273 mutations with reduced cellular lipid phosphatase activity, which includes 1,789 missense mutations. These data recapitulated known functional findings but also uncovered new insights into PTEN protein structure, biochemistry, and mutation tolerance. Several residues in the catalytic pocket showed surprising mutational tolerance. We identified that the solvent exposure of wild-type residues is a critical determinant of mutational tolerance. Further, we created a comprehensive functional map by leveraging correlations between amino acid substitutions to impute functional scores for all variants, including those not present in the assay. Variant functional scores can reliably discriminate likely pathogenic from benign alleles. Further, 32% of ClinVar unclassified missense variants are phosphatase deficient in our assay, supporting their reclassification. ASD-associated mutations generally had less severe fitness scores relative to PHTS-associated mutations (p = 7.16× 10-5) and a higher fraction of hypomorphic mutations, arguing for continued genotype-phenotype studies in larger clinical datasets that can further leverage these rich functional data.

Unexpected cancer-predisposition gene variants in Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome patients without underlying germline PTEN mutations.

Patients with heritable cancer syndromes characterized by germline PTEN mutations (termed PTEN hamartoma tumor syndrome, PHTS) benefit from PTEN-enabled cancer risk assessment and clinical management. PTEN-wildtype patients (~50%) remain at increased risk of developing certain cancers. Existence of germline mutations in other known cancer susceptibility genes has not been explored in these patients, with implications for different medical management. We conducted a 4-year multicenter prospective study of incident patients with features of Cowden/Cowden-like (CS/CS-like) and Bannayan-Riley-Ruvalcaba syndromes (BRRS) without PTEN mutations. Exome sequencing and targeted analysis were performed including 59 clinically actionable genes from the American College of Medical Genetics and Genomics (ACMG) and 24 additional genes associated with inherited cancer syndromes. Pathogenic or likely pathogenic cancer susceptibility gene alterations were found in 7 of the 87 (8%) CS/CS-like and BRRS patients and included MUTYH, RET, TSC2, BRCA1, BRCA2, ERCC2 and HRAS. We found classic phenotypes associated with the identified genes in 5 of the 7 (71.4%) patients. Variant positive patients were enriched for the presence of second malignant neoplasms compared to patients without identified variants (OR = 6.101, 95% CI 1.143–35.98, p = 0.035). Germline variant spectrum and frequencies were compared to The Cancer Genome Atlas (TCGA), including 6 apparently sporadic cancers associated with PHTS. With comparable overall prevalence of germline variants, the spectrum of mutated genes was different in our patients compared to TCGA. Intriguingly, we also found notable enrichment of variants of uncertain significance (VUS) in our patients (OR = 2.3, 95% CI 1.5–3.5, p = 0.0002). Our data suggest that only a small subset of PTEN-wildtype CS/CS-like and BRRS patients could be accounted for by germline variants in some of the known cancer-related genes. Thus, the existence of alterations in other and more likely non-classic cancer-associated genes is plausible, reflecting the complexity of these heterogeneous hereditary cancer syndromes.

Identification of a PTEN mutation with reduced protein stability, phosphatase activity, and nuclear localization in Hong Kong patients with autistic features, neurodevelopmental delays, and macrocephaly.

PTEN is a tumor suppressor gene inactivated in over 30% of human cancers. It encodes a lipid phosphatase that serves as a gatekeeper of the phosphoinositide 3‐kinase signaling pathway. Germline mutation frequently occurs in this gene in patients diagnosed with PTEN Hamartoma Tumor Syndrome (PHTS). PHTS individuals are characterized by macrocephaly, benign growth of multiple tissues and increased tumor risk. In addition, autistic phenotypes are found in 10–20% of individuals carrying the germline PTEN mutation with macrocephaly. In this report, 13 suspected PHTS patients were screened for mutation in the PTEN gene. A missense variant (c. 302T > C) substituting the isoleucine at codon 101 to a threonine, a single nucleotide insertion (c. 327‐328insC) causing a frame shift mutation and termination at codon 109, and a nonsense variant (c. 1003C > T) truncated the protein at codon 335 were identified. The I101T mutation significantly reduced PTEN protein expression levels by 2.5‐ to 4.0‐fold. Mechanistically, I101T reduced the protein half‐life of PTEN possibly due to enhanced polyubiquitination at Lysine 13. However, the I101T mutant retained almost 30% of the lipid phosphatase activity of the wild‐type protein. Finally, the I101T mutant has reduced phosphorylation at a PTEN auto‐dephosphorylation site at Threonine 366 and a lowered ratio of nuclear to cytosolic protein level. These partial losses of multiple PTEN biochemical functions may contribute to the tissue overgrowth and autistic features of this PHTS patient. Autism Res 2018, 11: 1098–1109. © 2018 The Authors Autism Research published by International Society for Autism Research and Wiley Periodicals, Inc.Lay SummaryThe genetics of autism spectrum disorders is highly complex with individual risk influenced by both genetic and environmental factors. Mutation in the human PTEN gene confers a high risk of developing autistic behavior. This report revealed that PTEN mutations occurred in 23% of a selected group of Hong Kong patients harboring autistic features with gross overgrowth symptoms. Detailed characterization of a PTEN mutation revealed reduced protein stability as one of the underlying mechanisms responsible for reduced PTEN activity.

Novel Germline PTEN Mutation Associated with Cowden Syndrome and Osteosarcoma

Cowden syndrome (CS) is a rare autosomal-dominant inherited disorder characterized by multiple hamartomas. While the hamartomas are benign, patients with CS have increased risk of osteosarcoma and of breast, thyroid, endometrial, soft-tissue and colonic neoplasms. Germline mutations of phosphatase and tensin homolog (PTEN) are implicated in CS and in the development of osteosarcoma. We report a patient with CS who presented with osteosarcoma, ganglioneuromatosis and a benign breast mass. Osteosarcoma, as presentation of CS, is rare (only one report in the English literature). Genomic DNA from the patient's peripheral blood was quantified by spectrophotometry, then underwent sequence enrichment, polymerase chain reaction and next-generation sequencing. Molecular analysis revealed a non-synonymous c.17_18delAA frameshift mutation in exon 1 of PTEN and a c.116G>T (p.R39L) missense mutation of serine/threonine kinase 11 (STK11) of unknown significance. We report a patient with CS presenting with ganglioneuromatosis, benign breast mass and osteosarcoma, harboring a novel molecular alteration in PTEN which to our knowledge has not been previously reported.

Hamartoma-like lesions in the mouse retina: an animal model of Pten hamartoma tumour syndrome.

ABSTRACTPTEN hamartoma tumour syndrome (PHTS) is a heterogeneous group of rare, autosomal dominant disorders associated with PTEN germline mutations. PHTS patients routinely develop hamartomas, which are benign tissue overgrowths comprised of disorganized ‘normal’ cells. Efforts to generate PHTS animal models have been largely unsuccessful due to the early lethality of homozygous germline mutations in Pten, together with the lack of hamartoma formation in most conditional mutants generated to date. We report herein a novel PHTS mouse model that reproducibly forms hamartoma-like lesions in the central retina by postnatal day 21. Specifically, we generated a Pten conditional knockout (cKO) using a retinal-specific Pax6::Cre driver that leads to a nearly complete deletion of Pten in the peripheral retina but produces a mosaic of ‘wild-type’ and Pten cKO cells centrally. Structural defects were only observed in the mosaic central retina, including in Müller glia and in the outer and inner limiting membranes, suggesting that defective mechanical integrity partly underlies the hamartoma-like pathology. Finally, we used this newly developed model to test whether rapamycin, an mTOR inhibitor that is currently the only PHTS therapy, can block hamartoma growth. When administered in the early postnatal period, prior to hamartoma formation, rapamycin reduces hamartoma size, but also induces new morphological abnormalities in the Pten cKO retinal periphery. In contrast, administration of rapamycin after hamartoma initiation fails to reduce lesion size. We have thus generated and used an animal model of retinal PHTS to show that, although current therapies can reduce hamartoma formation, they might also induce new retinal dysmorphologies.This article has an associated First Person interview with the first author of the paper.

The microbiome in PTEN hamartoma tumor syndrome.

Germline PTEN mutations defining PTEN hamartoma tumor syndrome (PHTS) confer heritable predisposition to breast, endometrial, thyroid and other cancers with known age-related risks, but it remains impossible to predict if any individual will develop cancer. In the general population, gut microbial dysbiosis has been linked to cancer, yet is unclear whether these are associated in PHTS patients. In this pilot study, we aimed to characterize microbial composition of stool, urine, and oral wash from 32 PTEN mutation-positive individuals using 16S rRNA gene sequencing. PCoA revealed clustering of the fecal microbiome by cancer history (P = 0.03, R 2 = 0.04). Fecal samples from PHTS cancer patients had relatively more abundant operational taxonomic units (OTUs) from family Rikenellaceae and unclassified members of Clostridia compared to those from non-cancer patients, whereas families Peptostreptococcaceae, Enterobacteriaceae, and Bifidobacteriaceae represented relatively more abundant OTUs among fecal samples from PHTS non-cancer patients. Functional metagenomic prediction revealed enrichment of the folate biosynthesis, genetic information processing and cell growth and death pathways among fecal samples from PHTS cancer patients compared to non-cancer patients. We found no major shifts in overall diversity and no clustering by cancer history among oral wash or urine samples. Our observations suggest the utility of an expanded study to interrogate gut dysbiosis as a potential cancer risk modifier in PHTS patients.

Identification of mutations in the PI3K-AKT-mTOR signalling pathway in patients with macrocephaly and developmental delay and/or autism

BackgroundMacrocephaly, which is defined as a head circumference greater than or equal to + 2 standard deviations, is a feature commonly observed in children with developmental delay and/or autism spectrum disorder. Although PTEN is a well-known gene identified in patients with this syndromic presentation, other genes in the PI3K-AKT-mTOR signalling pathway have also recently been suggested to have important roles. The aim of this study is to characterise the mutation spectrum of this group of patients.MethodsWe performed whole-exome sequencing of 21 patients with macrocephaly and developmental delay/autism spectrum disorder. Sources of genomic DNA included blood, buccal mucosa and saliva. Germline mutations were validated by Sanger sequencing, whereas somatic mutations were validated by droplet digital PCR.ResultsWe identified ten pathogenic/likely pathogenic mutations in PTEN (n = 4), PIK3CA (n = 3), MTOR (n = 1) and PPP2R5D (n = 2) in ten patients. An additional PTEN mutation, which was classified as variant of unknown significance, was identified in a patient with a pathogenic PTEN mutation, making him harbour bi-allelic germline PTEN mutations. Two patients harboured somatic PIK3CA mutations, and the level of somatic mosaicism in blood DNA was low. Patients who tested positive for mutations in the PI3K-AKT-mTOR pathway had a lower developmental quotient than the rest of the cohort (DQ = 62.8 vs. 76.1, p = 0.021). Their dysmorphic features were non-specific, except for macrocephaly. Among the ten patients with identified mutations, brain magnetic resonance imaging was performed in nine, all of whom showed megalencephaly.ConclusionWe identified mutations in the PI3K-AKT-mTOR signalling pathway in nearly half of our patients with macrocephaly and developmental delay/autism spectrum disorder. These patients have subtle dysmorphic features and mild developmental issues. Clinically, patients with germline mutations are difficult to distinguish from patients with somatic mutations, and therefore, sequencing of buccal or saliva DNA is important to identify somatic mosaicism. Given the high diagnostic yield and the management implications, we suggest implementing comprehensive genetic testing in the PI3K-AKT-mTOR pathway in the clinical evaluation of patients with macrocephaly and developmental delay and/or autism spectrum disorder.

Germline TTN variants are enriched in PTEN-wildtype Bannayan\u2013Riley\u2013Ruvalcaba syndrome

Bannayan–Riley–Ruvalcaba syndrome (BRRS) is a rare congenital disorder classically characterized by macrocephaly in combination with intestinal hamartomatous polyposis, vascular malformations, lipomas, and genital lentiginosis. Germline PTEN mutations have been reported in up to 60% of BRRS patients. The remaining cases are of unknown genetic etiology. We exome-sequenced 35 unrelated PTEN-wildtype patients with classic presentation of BRRS and identified TTN germline missense variants in 12/35 (34%) patients. TTN encodes TITIN, a key structural and functional muscle protein. Exome and TTN-targeted sequencing in an additional unrelated series of 231 BRRS-like patients revealed 37 (16%) additional patients with germline TTN variants. All variants were predicted to be deleterious and equally distributed between the A-band and I-band protein domains. Rare TTN variants (MAF ≤ 0.0001) are enriched in classic BRRS patients compared to BRRS-like (OR = 2.7, 95% CI 1.21-5.94, p = 1.6 × 10-2) and multiple population controls (OR = 2.2, 95% CI 1.01-4.20, p = 4.7 × 10-2). Germline TTN mutations of different genotypes, inheritance patterns, and protein domain enrichment have been identified in multiple cardiac and/or skeletal muscular disorders. Functional interrogation of I-band variant p.Cys5096Arg identified in one of our classic BRRS patients, using CRISPR-Cas9 genome-edited cell lines, reveals an increased growth and lack of contact inhibition phenotype associated with increased levels of or phosphorylation of focal adhesion kinase (FAK) in mutant cells. These findings suggest that TITIN could play a role in overgrowth-relevant pathways and phenotypes. In summary, our observations suggest TTN as a candidate predisposing gene in classic PTEN-wildtype BRRS patients, perhaps suggesting this syndrome join the growing list of Titinopathies.

Severe Radiation Toxicity Associated with a Germline PTEN Mutation

Severe Radiation Toxicity Associated with a Germline PTEN Mutation

Characterization of cryptic splicing in germline PTEN intronic variants in Cowden syndrome.

Germline mutations in the tumor‐suppressor gene PTEN predispose to subsets of Cowden syndrome (CS), Bannayan–Riley–Ruvalcaba syndrome, and autism. Evidence‐based classification of PTEN variants as either deleterious or benign is urgently needed for accurate molecular diagnosis and gene‐informed genetic counseling. We studied 34 different germline PTEN intronic variants from 61 CS patients, characterized their PTEN mRNA processing, and analyzed PTEN expression and downstream readouts of P‐AKT and P‐ERK1/2. While we found that many mutations near splice junctions result in exon skipping, we also identified the presence of cryptic splicing that resulted in premature termination or a shift in isoform usage. PTEN protein expression is significantly lower in the group with splicing changes while P‐AKT, but not P‐ERK1/2, is significantly increased. Our observations of these PTEN intronic variants should contribute to the determination of pathogenicity of PTEN intronic variants and aid in genetic counseling.

Cowden syndrome-associated germline succinate dehydrogenase complex subunit D (SDHD) variants cause PTEN-mediated down-regulation of autophagy in thyroid cancer cells.

Thyroid cancer is a major component cancer of Cowden syndrome (CS), a disorder typically associated with germline mutations in PTEN. Germline variants in succinate dehydrogenase genes (SDHx) co-occurring with PTEN germline mutations confer a 2-fold increased prevalence (OR 2.7) of thyroid cancer compared to PTEN-associated CS but 50% decreased prevalence (OR 0.54) of thyroid cancer compared to SDHx-associated CS. We have previously shown that CS-associated SDHD variants G12S and H50R induce PTEN oxidation and nuclear accumulation in thyroid cancer. Our current study shows that SDHD-G12S and -H50R variants cause down-regulation of autophagy, demonstrating a role for SDHD in autophagy-associated pathogenesis of differentiated thyroid cancer. These findings could explain the increased prevalence of thyroid cancer in CS patients with SDHx germline mutations compared to those with PTEN mutations alone. Importantly, we demonstrate the dependence of this process on functional wild-type PTEN with reversal of decreased autophagy after PTEN knockdown. The latter could explain the clinically observed decrease in thyroid cancer prevalence in patients with co-existent PTEN mutations and SDHx variants. We also show that SDHD-G12S/H50R promotes mono-ubiquitination of PTEN, causing its translocation into the nucleus, upregulation of AKT and consequent phosphorylation of FOXO3a. Furthermore, SDHD-G12S/H50R-mediated increase in acetylation of FOXO3a further enhances AKT-associated phosphorylation of FOXO3a. This combination of phosphorylation and acetylation of FOXO3a results in its nuclear export for degradation and consequent down-regulation of FOXO3a-target autophagy-related gene (ATG) expression. Overall, our study reveals a novel mechanism of crosstalk amongst SDHD, PTEN and autophagy pathways and their potential roles in thyroid carcinogenesis.

The Dosage of Pten Is Critical in Determining the Disease Severity - a Mouse Model Differentially Mimicking JMML and CMML

Juvenile myelomonocytic leukemia (JMML) and chronic myelomonocytic leukemia (CMML) are mixed myelodysplastic syndromes (MDS)/myeloproliferative neoplasms (MPNs) that share similar clinical manifestations, but differ in prognosis and ages at diagnosis. Both are characterized by monocytosis and monocytic infiltration in vital organs. JMML is extremely aggressive, with death occurring within one year after diagnosis in children (<6 Yrs) without therapy, whereas CMML presents in adults with a more indolent course. A dysregulated RAS pathway is the key mechanism of JMML and CMML, but the number of non-synonymous mutations per tumor in JMML patients is ranked among the least of all human cancers. Previously, we reported that mice with somatic Pten deletion and germline mutant Nf1 (PtenΔ/ΔNf1wt/-) mimic human MPNs with features of a pediatric mixed MDS/MPNs, in terms of age of onset and organ infiltration with myelomonocytic cells, but lack a key feature of JMML with respect to GM-CSF hypersensitivity (Blood 2016; 127:1912). In order to simulate the molecular dynamics observed in JMML, we introduced Nf1 Loss-Of-Heterozygosity (Nf1LOH) by somatically deleting the second copy of Nf1 in mice on postnatal day 8 (PND8, equivalent to a full-term newborn age in humans).We generated mice with PtenfloxP/floxPNf1Fcr/floxPMx1-Cre+ on a C57BL6/129 genetic background, and conditionally deleted Pten and the second copy of Nf1 myeloid-specifically by intraperitoneal injection of Poly(I:C). Mice with bi-allelic Pten deletion and Nf1LOH (PtenΔ/ΔNf1LOH) were born healthy but revealed signs of sickness in the 2nd week of life, and all died by age 4 weeks (equivalent to 1-3 years old in humans); whereas mice with heterozygous Pten deletion and Nf1LOH (Ptenwt/ΔNf1LOH) did not show obvious signs of disease until age 2 months, and possessed a lifespan longer than 3 months. The natural lifespan of PtenΔ/ΔNf1LOH mice (n=8) was significantly shorter than littermates with PtenΔ/ΔNf1wt/Δ (n=18), Ptenwt/ΔNf1LOH (n=10), or wild type (ptenwtNf1wt, hereafter referred asWT, n=14, p<0.001). We analyzed 13 PtenΔ/ΔNf1LOH mice at age PND18-21 along withtheir littermates. Substantial hepatosplenomegaly was observed in mice with Pten deletion and correlated with the loss of copy number of Pten and Nf1 inthe following order: PtenΔ/ΔNf1LOH >PtenΔ/ΔNf1wt/Δ >Ptenwt/ΔNf1LOH > WT (median spleen weight: 228>180>134>56mg, respectively, p<0.001). Mice with PtenΔ/ΔNf1LOH(n=13) or Ptenwt/ΔNf1LOH (n=12) had significantly elevated white blood cells (WBCs) and a lower hemoglobin than PtenΔ/ΔNf1wt/Δ (n=21) or WT littermates (n=15). HE stained tissue sections of formalin-fixed organs revealed increased cellularity in bone marrow (BM), and severe infiltration of mature myeloid cells in the spleens, livers, and lungs of mice with PtenΔ/ΔNf1LOH. Flow cytometry analysis (FACS) revealed that PtenΔ/ΔNf1LOH mice had significantly increased monocyte/macrophages and granulocytes in BM and peripheral blood (PB), but significant reduction in T-cells and B-cells in PB and spleen. A significant increase in Ter119+CD71high cells was also found in PtenΔ/ΔNf1LOH mice, indicating MDS or leukemia. Interestingly, splenic marginal zone B-cells were significantly lower exclusively in PtenΔ/ΔNf1LOH mice. Mice with Ptenwt/ΔNf1LOH had the similar FACS profile with less disease severity at age PND18-21. They lived longer than 3 months without obvious signs of disease except increased WBCs and mild anemia. BM cells from PtenΔ/ΔNf1LOH mice at an age of 3 weeks were hypersensitive to GM-CSF, but Ptenwt/ΔNf1LOH mice did not display this until an age of 2 months. Based on the Bethesda proposals for classification of non-lymphoid hematopoietic neoplasms in mice, we have developed a mouse model of a mixed MDS/MPNs with features of JMML and CMML, in terms of age of onset and organ infiltration with myelomonocytic cells, and GM-CSF hypersensitivity.In conclusion, our data demonstrate that bi-allelic Pten deletion and Nf1LOH at an early age results in JMML in mice, whereas single-allelic Pten deletion with Nf1LOH induces CMML. This is the first mouse model that differentially resembles pediatric and adult mixed MDS/MPNs, and closely mimics the true genetic and epigenetic dynamics in humans. It provides a novel tool for studying the mechanisms underlying pediatric and adult mixed MDS/MPNs. DisclosuresNo relevant conflicts of interest to declare.

Hidden association of Cowden syndrome, PTEN mutation and meningioma frequency

Cowden syndrome (CS) is clinically presented by multiple hamartomas, often with mucocutaneous lesions, goiter, breast cancer and gastrointestinal polyps. CS is a genetic disorder of autosomal dominant inheritance and is one distinct syndrome of the phosphatase and tensin homolog on chromosome 10 (PTEN) hamartoma tumor spectrum. Noteworthy, PTEN germline mutations are related to a wide range of brain tumors. We performed a systematic analysis and review of the medical literature for Cowden syndrome and meningioma and additionally present the case of a 29-year- old CS patient diagnosed with multiple meningiomas. We found strong evidence for high incidence of brain tumors in CS patients. In particular meningiomas and gangliocytomas/Lhermitte-Duclos disease were often associated with 8% and 9% respectively in CS patients. Since aberrations in chromosome 10q are associated with meningiomas, it is likely that the underlying mutations in CS drive to a certain extent neoplastic meningioma growth. We propose to include meningiomas and brain tumors in the major criteria spectrum of CS-related disorders. This could warrant early diagnosis of brain lesions and close therapy, as well as better monitoring of patients with CS.

Immune dysregulation in patients with PTEN hamartoma tumor syndrome: Analysis of FOXP3 regulatory T cells

BackgroundPatients with heterozygous germline mutations in phosphatase and tensin homolog deleted on chromosome 10 (PTEN) experience autoimmunity and lymphoid hyperplasia.ObjectivesBecause regulation of the phosphoinositide 3-kinase (PI3K) pathway is critical for maintaining regulatory T (Treg) cell functions, we investigate Treg cells in patients with heterozygous germline PTEN mutations (PTEN hamartoma tumor syndrome [PHTS]).MethodsPatients with PHTS were assessed for immunologic conditions, lymphocyte subsets, forkhead box P3 (FOXP3)+ Treg cell levels, and phenotype. To determine the functional importance of phosphatases that control the PI3K pathway, we assessed Treg cell induction in vitro, mitochondrial depolarization, and recruitment of PTEN to the immunologic synapse.ResultsAutoimmunity and peripheral lymphoid hyperplasia were found in 43% of 79 patients with PHTS. Immune dysregulation in patients with PHTS included lymphopenia, CD4+ T-cell reduction, and changes in T- and B-cell subsets. Although total CD4+FOXP3+ Treg cell numbers are reduced, frequencies are maintained in the blood and intestine. Despite pathogenic PTEN mutations, the FOXP3+ T cells are phenotypically normal. We show that the phosphatase PH domain leucine-rich repeat protein phosphatase (PHLPP) downstream of PTEN is highly expressed in normal human Treg cells and provides complementary phosphatase activity. PHLPP is indispensable for the differentiation of induced Treg cells in vitro and Treg cell mitochondrial fitness. PTEN and PHLPP form a phosphatase network that is polarized at the immunologic synapse.ConclusionHeterozygous loss of function of PTEN in human subjects has a significant effect on T- and B-cell immunity. Assembly of the PTEN-PHLPP phosphatase network allows coordinated phosphatase activities at the site of T-cell receptor activation, which is important for limiting PI3K hyperactivation in Treg cells despite PTEN haploinsufficiency.

Autism-relevant behaviors are minimally impacted by conditional deletion of Pten in oxytocinergic neurons.

Germline heterozygous mutations in Pten (phosphatase and tensin homolog) are associated with macrocephaly and autism spectrum disorders (ASD). Pten germline heterozygous (Pten+/- ) mice approximate these mutations, and both sexes show widespread brain overgrowth and impaired social behavior. Strikingly similar behavior phenotypes have been reported in oxytocin (Oxt) and/or oxytocin receptor (OxtR) knockout mice. Thus, we hypothesized that the behavioral phenotypes of germline Pten+/- mice may be caused by reduced Pten function in Oxt-expressing cells. To investigate this, we tested mice in which Pten was conditionally deleted using oxytocin-Cre (Oxt-Cre+ ; PtenloxP/+ , Oxt-Cre+ ; PtenloxP/loxP ) on a battery including assays of social, repetitive, depression-like, and anxiety-like behaviors. Minimal behavioral abnormalities were found; decreased anxiety-like behavior in the open field test in Oxt-Cre+ ; PtenloxP/loxP males was the only result that phenocopied germline Pten+/- mice. However, Oxt cell size was dramatically increased in Oxt-Cre+ ; PtenloxP/loxP mice in adulthood. Thus, conditional deletion of Pten using Oxt-Cre has a profound effect on Oxt cell structure, but not on ASD-relevant behavior. We interpret these results as inconsistent with our starting hypothesis that reduced Pten function in Oxt-expressing cells causes the behavioral deficits observed in germline Pten+/- mice. Autism Res 2016, 9: 1248-1262. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.

Type 1 serrated polyposis represents a predominantly female disease with a high prevalence of dysplastic serrated adenomas, without germline mutation in MUTYH, APC, and PTEN genes.

The aim of this article is to clarify the epidemiologic, clinical, endoscopic, biological and genetic characteristics of type 1 serrated polyposis patients. Consecutive patients responding to the WHO definition of type 1 serrated polyposis in one reference center for polyposis patients accepted genetic counseling. Detailed data on previous endoscopies, histology, and life habits were recorded, after informed consent, germline analysis of MUTYH, APC, and PTEN germline mutations. Molecular biology was tested on available fixed tissue from different lesion types. We included 29 patients (mean age 53.5 years, 21 women (72.4%)), four with a personal history of colorectal cancer (CRC), with a mean of 11.6 SSAs, with associated hyperplastic polyps in 93.1% and adenomas in 82.8%. SSAs showed no dysplasia in 46.9% of lesions (three of 29 patients), LGD in 51.9% (22/29 patients), and HGD in 1.2% (four of 29 patients). Dysplasia was more frequent in proximal SSAs and in women. Colectomy 15 patients (51.7%), upper digestive neoplasms: eight patients (27.5%); smokers: 24 patients (82.8%); family history of CRC: 16 patients (55.2%). Biology: MSI-H phenotype in one SSA, V600E BRAF mutation in 95% of SSAs; MGMT hypermethylation in three of 17 SSAs. No germline mutation was detected in MYH, APC or PTEN genes. Type 1 serrated polyposis corresponds to a majority of women, with a high prevalence of smokers, a high prevalence of dysplastic serrated adenomas, particularly in females, without identified germline mutation in targeted predisposing genes.

Phase I study of veliparib with gemcitabine and radiation therapy in patients with borderline resectable and locally advanced unresectable pancreatic cancer.

TPS487 Background: Targeted inhibition of PARP1/2 is one way to further exploit the well-known synergy between gemcitabine (G) and radiotherapy (RT) in locally advanced pancreatic cancer (LAPC). PARP1/2 inhibitors, such as veliparib (V), have shown excellent anti-tumor activity when used with other cytotoxic therapies. This synergy may be further exploited in pancreatic cancer by targeting tumors with pre-existing defects in double- strand DNA repair. Extrapolating from our own laboratory findings (Tuli et al, Transl Oncol, 2014) and based on our hypothesis that PARP1/2 inhibition with G and RT will result in enhanced tumor control, we are conducting an IRB- approved phase I study in patients with borderline resectable and LAPC. Methods: The primary objective of this study is to determine the maximum tolerated dose (MTD) of V, which is defined as the dose level resulting in a probability (θ = 0.4) that a dose limiting toxicity (DLT) will occur within six weeks. Treatment cycle is 3 weeks followed by weekly evaluation for an additional 3 weeks. G (1000 mg/m2) is administered on days 1, 8, 15. RT (36 Gy) is given in 15 fractions (2.4 Gy/day). V is administered BID in 20 mg increments beginning at a dose of 20 mg. Inclusion criteria: histolopathological diagnosis of borderline resectable or LAPC, age &gt; 18 years, KPS &gt; 70%, life expectancy &gt; 6 months, normal organ and marrow function, and negative pregnancy test. Dose escalation follows a Bayesian escalation without control (EWOC) design, where time to DLT is modeled using a proportional hazards model with constant baseline hazard rate. Secondary objectives: 1) measure clinical activity using RECIST 1.1 for PFS, OS; 2) evaluate pre-treatment tumor biopsy specimen and longitudinal blood samples for baseline levels of DNA repair proteins (ERCC1, XRCC1, PAR, etc.) as potential prognostic, predictive and correlative biomarkers; and 3) assess BRCA1/2, PALB2, PTEN germline and somatic mutations using validated gene sequencing, immunohistochemical and quantitative PCR methods. Since December 2013, 26 patients have consented with 22 enrolled. Clinical trial information: NCT01908478.

Breast cancer risk and clinical implications for germline PTEN mutation carriers.

PTEN Hamartoma Tumor syndrome (PHTS) encompasses a clinical spectrum of heritable disorders including Cowden syndrome (CS), Bannayan-Riley-Ruvalcaba syndrome, and Proteus and Proteus-like syndrome that are associated with germline mutations in the PTEN tumor suppressor gene. Breast cancer risk estimates (67-85%) for women with germline PTEN mutations are similar to those quoted for patients with germline mutations in the BRCA1/2 genes. With PTEN on several germline gene testing panels, finding PTEN mutations and variants have increased exponentially. PHTS can be differentiated from other hereditary cancer syndromes including Hereditary Breast Ovarian Cancer syndrome, Lynch syndrome, and hamartomatous polyposis syndromes based on personal as well as family history. However, many of the benign features of CS are common in the general population, making the diagnosis of CS challenging. Breast cancer patients with an identified germline PTEN mutation are at increased risk of endometrial, thyroid, renal, and colorectal cancers as well as a second breast cancer. Increased screening for the various component cancers as well as predictive testing in first-degree relatives is recommended. Prophylactic mastectomy may be considered especially if breast tissue is dense or if repeated breast biopsies have been necessary. Management of women with breast cancer suspected of CS who test negative for germline PTEN mutations should be managed as per a mutation carrier if she meets CS diagnostic criteria, and should be offered enrollment in research to identify other predisposition genes.

Methods for PTEN in Stem Cells and Cancer Stem Cells.

PTEN (phosphatase and tensin homologue) is the first tumor suppressor identified to have phosphatase activity and its gene is the second most frequently deleted or mutated tumor-suppressor gene associated with human cancers. Germline PTEN mutations are the cause of three inherited autosomal dominant disorders. Phosphatidylinositol 3,4,5,-triphosphate (PIP3), the product of the PI3 kinase, is one of the key intracellular targets of PTEN's phosphatase activity, although PTEN's phosphatase-independent activities have also been identified. PTEN is critical for stem cell maintenance, which contributes to its controlled tumorigenesis. PTEN loss leads the development of cancer stem cells (CSCs) that share properties with somatic stem cells, including the capacity for self-renewal and multi-lineage differentiation. Methods to isolate and functionally test stem cells and CSCs are important for understanding PTEN functions and the development of therapeutic approaches to target CSCs without having adverse effects on normal stem cells. Here, we describe protocols for the isolation and functional analysis of PTEN deficient embryonic stem cells, hematopoietic stem cells and leukemia-initiating cells (LICs), neural stem cells, and prostate stem cells and CSCs.

Germline PTEN Mutation Analysis for PTEN Hamartoma Tumor Syndrome.

Clinically, deregulation of PTEN function resulting in reduced PTEN expression and/or activity is implicated in human disease. Cowden syndrome (CS) is an autosomal dominant disorder characterized by benign and malignant tumors. CS-related individual features occur commonly in the general population. Approximately 25 % of patients diagnosed with CS have pathogenic germline PTEN mutations, which increase lifetime risks of breast, thyroid, uterine, renal, and other cancers. PTEN testing and intensive cancer surveillance allow for early detection and treatment of these cancers for mutation-positive patients and their relatives. In this methods chapter, we highlight our protocol for identifying patients at risk of harboring a germline PTEN mutation.