PTEN Variants Research Articles

Comparative analysis of mutational patterns in triple negative breast cancer before and after neoadjuvant chemotherapy in patients with residual disease

Triple-negative breast cancer (TNBC) is a heterogeneous disease with poor survival compared to other subtypes. Patients with residual disease after neoadjuvant chemotherapy (NAC) face an increased risk of relapse and death. We aimed to characterize the mutational landscape of this subset to offer insights into relapse pathogenesis and potential therapeutic targets. We retrospectively analyzed archived paired (pre- and post-NAC) tumor samples from 25 patients with TNBC with residual disease using a targeted 72-gene next-generation sequencing panel. Our findings revealed a stable mutational burden in both pre- and post-NAC samples, with a median count of 12 variants (IQR 7–17.25) per sample. TP53, PMS2, PTEN, ERBB2, and NOTCH1 variants were observed in pre-NAC samples predominantly. Notably, post-NAC samples exhibited a significant increase in AR gene mutations, suggesting potential prognostic and predictive implications. No difference in mutational burden was found between patients who did and did not receive platinum (p = 0.94), or between those with and without recurrence (p = 0.49). We employed K-means clustering to categorize the patients based on their variant profiles, aiding in the prediction of possible patterns associated with recurrence. Our study was limited by its small sample size and retrospective design, suggesting the need for further validation in larger prospective cohorts.

A Bi-Institutional Study of Gastrointestinal and Hepatic Manifestations in Children With PTEN Hamartoma Tumor Syndrome

PTEN hamartoma tumor syndrome (PHTS) confers a high risk of specific cancers and is the most common genetic cause of autism spectrum disorder (ASD). Gastrointestinal (GI) phenotypes in PHTS are poorly characterized in children. Thus, we aimed to characterize the GI and hepatic manifestations in children with PHTS and to investigate genotype-phenotype associations. We performed a retrospective chart review of prospectively accrued children with PHTS at 2 tertiary-care centers. Wilcoxon rank-sum, Chi-squared, and Fisher's exact tests and Firth's logistic regression were utilized to explore associations between variables. This series included 80 children with disease-causing PTEN variants. Common GI manifestations included constipation in 41 (51%), feeding issues in 31 (39%), and polyps in 22 (28%) children. The polyps were of mixed histologic types. Eosinophilic gastrointestinal disorders were observed in 5 (6%) children. Crohn's disease, celiac disease, and protein-losing enteropathy were observed once each. Eosinophilic gastrointestinal disorders were observed exclusively in patients without ASD (P= .052). Nonsense PTEN variants were enriched in those with polyps (P= .029). Missense PTEN variants (OR 2.9, P= .034) and upper GI polyps (OR 4.4, P= .018) were associated with increased odds of constipation. Constipation and feeding issues are common in children with PHTS. Polyps are more prevalent in children with PHTS than previously described and associated with nonsense PTEN variants. Children without ASD represent a distinct patient subset with a predisposition to eosinophilic gastrointestinal disorders and possibly upper GI polyps. Endoscopic evaluation should continue to be performed in symptomatic children with PHTS, with consideration of closer follow-up in those without ASD.

Classification of PTEN missense VUS through exascale simulations.

Classification of PTEN variants affecting its lipid phosphatase activity is important for understanding the roles of PTEN variation in the pathogenesis of hereditary and sporadic malignancies. Of the 3000 variants identified in PTEN, 1296 (43%) were assigned as VUS. Here, we applied MD and REMD simulations to investigate the effects of PTEN missense VUS on the structural integrity of the PTEN phosphatase domain consisting the WPD, P and TI active sites. We classified a total of 147 missense VUS into 66 deleterious and 81 tolerated variants by referring to the control group comprising 54 pathogenic and 12 benign variants. The classification was largely in concordance with these classified by experimental approaches.

UV-radiation and MC1R germline mutations are risk factors for the development of conventional and spitzoid melanomas in children and adolescents

Genomic characterisation has led to an improved understanding of adult melanoma. However, the aetiology of melanoma in children is still unclear and identifying the correct diagnosis and therapeutic strategies remains challenging. Exome sequencing of matched tumour-normal pairs from 26 paediatric patients was performed to study the mutational spectrum of melanomas. The cohort was grouped into different categories: spitzoid melanoma (SM), conventional melanoma (CM), and other melanomas (OT). In all patients with CM (n=10) germline variants associated with melanoma were found in low to moderate melanoma risk genes: in 8 patients MC1R variants, in 2 patients variants in MITF, PTEN and BRCA2. Somatic BRAF mutations were detected in 60% of CMs, homozygous deletions of CDKN2A in 20%, TERTp mutations in 30%. In the SM group (n=12), 5 patients carried at least one MC1R variant; somatic BRAF mutations were detected in 8.3%, fusions in 25% of the cases. No SM showed a homozygous CDKN2A deletion nor a TERTp mutation. In 81.8% of the CM/SM cases the UV damage signatures SBS7 and/or DBS1 were detected. The patient with melanoma arising in giant congenital nevus (CNM) demonstrated the characteristic NRAS Q61K mutation. UV-radiation and MC1R germline variants are risk factors in the development of conventional and spitzoid paediatric melanomas. Paediatric CMs share genomic similarities with adult CMs while the SMs differ genetically from the CM group. Consistent genetic characterization of all paediatric melanomas will potentially lead to better subtype differentiation, treatment, and prevention in the future. Found in Acknowledgement.

Longitudinal analysis of cancer risk in children and adults with germline PTEN variants

Longitudinal analysis of cancer risk in children and adults with germline PTEN variants

SHH medulloblastoma and very early onset of bowel polyps in a child with PTEN hamartoma tumor syndrome.

Phosphatase and tensin homolog (PTEN) hamartoma tumor syndrome (PHTS) is a cancer predisposition syndrome characterized by an increased risk of developing benign and malignant tumors, caused by germline pathogenic variants of the PTEN tumour suppressor gene. PTEN gene variants often present in childhood with macrocephaly, developmental delay, and/or autism spectrum disorder while tumors and intestinal polyps are commonly detected in adults. PHTS is rarely associated with childhood brain tumors with only two reported cases of medulloblastoma (MB). We report the exceptional case of an infant carrying a germline and somatic pathogenic variant of PTEN and a germline and somatic pathogenic variant of CHEK2 who developed a MB SHH in addition to intestinal polyposis.

Novel anti-PTEN C2 domain monoclonal antibodies to analyse the expression and function of PTEN isoform variants.

PTEN is a major tumor suppressor gene frequently mutated in human tumors, and germline PTEN gene mutations are the molecular diagnostic of PTEN Hamartoma Tumor Syndrome (PHTS), a heterogeneous disorder that manifests with multiple hamartomas, cancer predisposition, and neurodevelopmental alterations. A diversity of translational and splicing PTEN isoforms exist, as well as PTEN C-terminal truncated variants generated by disease-associated nonsense mutations. However, most of the available anti-PTEN monoclonal antibodies (mAb) recognize epitopes at the PTEN C-terminal tail, which may introduce a bias in the analysis of the expression of PTEN isoforms and variants. We here describe the generation and precise characterization of anti-PTEN mAb recognizing the PTEN C2-domain, and their use to monitor the expression and function of PTEN isoforms and PTEN missense and nonsense mutations associated to disease. These anti-PTEN C2 domain mAb are suitable to study the pathogenicity of PTEN C-terminal truncations that retain stability and function but have lost the PTEN C-terminal epitopes. The use of well-defined anti-PTEN mAb recognizing distinct PTEN regions, as the ones here described, will help to understand the deleterious effects of specific PTEN mutations in human disease.

Integrating somatic CNV and gene expression in breast cancers from women with PTEN hamartoma tumor syndrome

Women with germline PTEN variants (PTEN hamartoma tumor syndrome, PHTS) have up to 85% lifetime risk of female breast cancer (BC). We previously showed that PHTS-derived BCs are distinct from sporadic BCs both at the clinical and genomic levels. In this study, we examined somatic copy number variations (CNV) and transcriptome data to further characterize the somatic landscape of PHTS-derived BCs. We analyzed exome sequencing data from 44 BCs from women with PHTS for CNV. The control group comprised of 558 women with sporadic BCs from The Cancer Genome Atlas (TCGA) dataset. Here, we found that PHTS-derived BCs have several distinct CNV peaks compared to TCGA. Furthermore, RNA sequencing data revealed that PHTS-derived BCs have a distinct immunologic cell type signature, which points toward cancer immune evasion. Transcriptomic data also revealed PHTS-derived BCs with pathogenic germline PTEN variants appear to have vitamin E degradation as a key pathway associated with tumorigenesis. In conclusion, our study revealed distinct CNV x transcript features in PHTS-derived BCs, which further facilitate understanding of BC biology arising in the setting of germline PTEN mutations.

The mitochondrial genome as a modifier of autism versus cancer phenotypes in PTEN hamartoma tumor syndrome.

Cancer and autism spectrum disorder/developmental delay (ASD/DD) are two common clinical phenotypes in individuals with germline PTEN variants (PTEN hamartoma tumor syndrome, PHTS). Burgeoning studies have shown that genomic and metabolomic factors may act as modifiers of ASD/DD versus cancer in PHTS. Recently, we showed copy number variations to be associated with ASD/DD versus cancer in these PHTS individuals. We also found that mitochondrial complex II variants occurring in 10% of PHTS individuals modify breast cancer risk and thyroid cancer histology. These studies suggest that mitochondrial pathways could act as important factors in PHTS phenotype development. However, the mitochondrial genome (mtDNA) has never been systematically studied in PHTS. We therefore investigated the mtDNA landscape extracted from whole-genome sequencing data from 498 PHTS individuals, including 164 with ASD/DD (PHTS-onlyASD/DD), 184 with cancer (PHTS-onlyCancer), 132 with neither ASD/DD nor cancer (PHTS-neither), and 18 with both ASD/DD and cancer (PHTS-ASDCancer). We demonstrate that PHTS-onlyASD/DD has significantly higher mtDNA copy number than PHTS-onlyCancer group (p= 9.2×10-3 in all samples; p= 4.2×10-3 in the H haplogroup). PHTS-neither group has significantly higher mtDNA variant burden than PHTS-ASDCancer group (p= 4.6×10-2); the PHTS-noCancer group (PHTS-onlyASD/DD and PHTS-neither groups) also shows higher variant burden than the PHTS-Cancer group (PHTS-onlyCancer and PHTS-ASD/Cancer groups; p=3.3×10-2). Our study implicates the mtDNA as a modifier of ASD/DD versus cancer phenotype development in PHTS.

Whole genome sequencing and disease pattern in patients with juvenile polyposis syndrome: a nationwide study.

Juvenile polyposis syndrome (JPS) is a hereditary hamartomatous polyposis syndrome characterized by gastrointestinal juvenile polyps and increased risk of gastrointestinal cancer. Germline pathogenic variants are detected in SMAD4 or BMPR1A, however in a significant number of patients with JPS, the etiology is unknown. From Danish registers, and genetic department and laboratories, we identified all patients in Denmark with a clinical diagnosis of JPS and/or a pathogenic variant in BMPR1A or SMAD4. In patients where no variant had been detected, we performed genetic analysis, including whole genome sequencing. We collected clinical information on all patients to investigate the phenotypic spectrum. Sixty-six patients (mean age 40years) were included of whom the pathogenic variant was unknown in seven patients. We detected a pathogenic variant in SMAD4 or PTEN in additional three patients and thus ≈95% of patients had a pathogenic germline variant. Endoscopic information was available in fifty-two patients (79%) and of these 31 (60%) fulfilled the clinical criteria of JPS. In 41 patients (79%), other types of polyps than juvenile had been removed. Our results suggest that almost all patients with a clinical diagnosis of JPS has a pathogenic variant in mainly BMPR1A, SMAD4, and more rarely PTEN. However, not all patients with a pathogenic variant fulfil the clinical criteria of JPS. We also demonstrated a wide clinical spectrum, and that the histopathology of removed polyps varied.

Variants in PTEN Are Associated With a Diverse Spectrum of Cortical Dysplasia

BackgroundInactivating mutations in PTEN are among the most common causes of megalencephaly. Activating mutations in other nodes of the PI3K/AKT/MTOR signaling pathway are recognized as a frequent cause of cortical brain malformations. Only recently has PTEN been associated with cortical malformations, and analyses of their prognostic significance have been limited. MethodsRetrospective neuroimaging analysis and detailed chart review were conducted on 20 participants identified with pathogenic or likely pathogenic mutations in PTEN and a cortical brain malformation present on brain magnetic resonance imaging. ResultsNeuroimaging analysis revealed four main cerebral phenotypes—hemimegalencephaly, focal cortical dysplasia, polymicrogyria (PMG), and a less severe category, termed “macrocephaly with complicated gyral pattern” (MCG). Although a high proportion of participants (90%) had neurodevelopmental findings on presentation, outcomes varied and were favorable in over half of participants. Consistent with prior work, 39% of participants had autism spectrum disorder and 19% of participants with either pure-PMG or pure-MCG phenotypes had epilepsy. Megalencephaly and systemic overgrowth were common, but other systemic features of PTEN-hamartoma tumor syndrome were absent in over one-third of participants. ConclusionsA spectrum of cortical dysplasias is present in individuals with inactivating mutations in PTEN. Future studies are needed to clarify the prognostic significance of each cerebral phenotype, but overall, we conclude that despite a high burden of neurodevelopmental disease, long-term outcomes may be favorable. Germline testing for PTEN mutations should be considered in cases of megalencephaly and cortical brain malformations even in the absence of other findings, including cognitive impairment.

Identification of a novel pathogenic deep intronic variant in PTEN resulting in pseudoexon inclusion in a patient with juvenile polyps.

Colorectal, hamartomatous juvenile polyps occur as part of different hereditary syndromes, including Juvenile polyposis syndrome and PTEN-hamartoma tumour syndrome. However, based on clinical manifestations alone, it is difficult to differentiate between the syndromes, and genetic analysis with an NGS-panel is often used to aid diagnostics. We report a 59-year-old male with colorectal juvenile polyps, who had been referred to genetic testing but had normal genetic analysis. He did not fulfil the clinical criteria of PTEN- hamartoma tumour syndrome, but the clinical criteria of Juvenile polyposis syndrome. With Whole Genome Sequencing we detected a novel intronic variant of unknown significance in PTEN (NC_000010.11:g.89687361 A > G(chr10, hg19), NM_000314.8:c.209 + 2047 A > G). RNA analysis classified the variant as likely pathogenic as it results in a pseudoexon inclusion introducing a frameshift and a premature stop codon. The patient was then diagnosed with PTEN-hamartoma Tumour syndrome. To our knowledge this is the first report of a variant resulting in pseudoexon inclusion in PTEN.

Clinical Multigene Panel Testing Identifies Racial and Ethnic Differences in Germline Pathogenic Variants Among Patients With Early-Onset Colorectal Cancer.

The early-onset colorectal cancer (EOCRC) burden differs across racial/ethnic groups, yet the role of germline genetic predisposition in EOCRC disparities remains uncharacterized. We defined the prevalence and spectrum of inherited colorectal cancer (CRC) susceptibility gene variations among patients with EOCRC by race and ethnicity. We included individuals diagnosed with a first primary CRC between age 15 and 49 years who identified as Ashkenazi Jewish, Asian, Black, Hispanic, or White and underwent germline genetic testing of 14 CRC susceptibility genes performed by a clinical testing laboratory. Variant comparisons by racial and ethnic groups were evaluated using chi-square tests and multivariable logistic regression adjusted for sex, age, CRC site, and number of primary colorectal tumors. Among 3,980 patients with EOCRC, a total of 530 germline pathogenic or likely pathogenic variants were identified in 485 individuals (12.2%). By race/ethnicity, 12.7% of Ashkenazim patients, 9.5% of Asian patients, 10.3% of Black patients, 14.0% of Hispanic patients, and 12.4% of White patients carried a germline variant. The prevalence of Lynch syndrome (P = .037), as well as APC, CHEK2, MLH1, monoallelic MUTYH, and PTEN variants, varied by race/ethnicity among patients with EOCRC (all P < .026). Ashkenazim and Hispanic patients had significantly higher odds of presenting with a pathogenic APC variant, which included p.I1307K (odds ratio [OR], 2.67; 95% CI, 1.30 to 5.49; P = .007) and MLH1 variant (OR, 8.69; 95% CI, 2.68 to 28.20; P = .0003), respectively, versus White patients in adjusted models. Germline genetic features differed by race/ethnicity in young patients with CRC, suggesting that current multigene panel tests may not be representative of EOCRC risk in diverse populations. Further study is needed to optimize genes selected for genetic testing in EOCRC via ancestry-specific gene and variant discovery to yield equitable clinical benefits for all patients and to mitigate inequities in disease burden.

Novel dermatological and skeletal features associated with PTEN variant in PTEN hamartoma tumor syndrome

PTEN hamartoma tumor syndromes (PHTS) comprise hamartomatous overgrowth syndromes associated with PTEN germline mutations. In this case report, we describe a variant identified by next generation sequencing causing peculiar dermatological and skeletal features not yet described in the literature. Being cognizant of such unique disease presentations in PHTS, that manifest at a very young age, could help facilitate a timely diagnosis by clinicians and thus the early education of families on active cancer surveillance. This specific case also strengthens the concept of variable presentation of PHTS and the need for genetic testing early on, even if not all criteria for PHTS are met for a formal clinical diagnosis.

Validation of a breast cancer polygenic risk score in 15,490 Brazilians using exome sequencing.

10631 Background: Brazil has a highly admixed population with significant Southern European, African and Native American genetic ancestries. Approximately 75% of the population has two or more continental ancestries. Therefore, breast cancer polygenic risk scores (PRS) developed in predominantly European populations requires validation in the Brazilian population. Compared with genotyping arrays and whole genome sequencing, affordable and scalable whole exome sequencing (WES) allows genotyping of both rare and common variants in the targeted regions and imputation of common variants not directly captured. In this study we validate a previously developed 3820-variant PRS using WES in 15,490 Brazilians. Methods: The cohort consisted of 6,362 women with a history of breast cancer (mean age 49.6, stddev 11.6) and 9,128 unphenotyped adults as controls (mean age 41.6, stddev 13.3). WES were performed on germline DNA and variants were called and curated. Imputation was done using the 1000 Genomes Phase 3 reference panel for variants falling outside the WES captured regions. After excluding subjects with known pathogenic or likely pathogenic variants in BRCA1, BRCA2, PALB2, PTEN, or TP53, and first or second-degree relatives of the probands, 14,577 individuals remained in the final analysis (5,730 cases and 8,847 controls). We restricted PRS calculation to 2,893 of the original 3,820 variants with an estimated global imputation accuracy of 96%. Odds ratios (OR) were adjusted using the top 10 principal components. Results: The breast cancer PRS showed a highly significant correlation with cancer risk (p-value = 7.1e-81, OR = 1.43, 95% confidence interval (CI) = 1.38-1.48 per PRS standard deviation). Compared with women in the middle deciles, those in the highest 10% had an OR of 1.93, while those in the lowest 10% had an OR of 0.52 (Table). Conclusions: In this study we show that WES can capture 76% of the variants included in a previously developed and validated breast cancer PRS, and the calculated PRS is correlated with breast cancer risk in the admixed Brazilian population. This opens the door for clinical studies into the application of PRS in Brazil, particularly in women without mutations in breast cancer high-penetrance genes. In addition, our WES-based PRS strategy can be quickly, affordably, and seamlessly adopted by labs that already offer Hereditary Breast Cancer panels that use WES as a backbone. [Table: see text]

PTEN Deficiency: a phenocopy phenomenon

BackgroundActivated PI3K delta syndrome 1 (APDS1) is caused by mutations in PI3KCD. The phosphatidylinositol 3-kinase (PI3K) signaling pathway is essential to cell survival, proliferation, and metabolism. PI3K plays a crucial role in the regulation of function and differentiation of immune cells. Phosphatase and tensin homolog (PTEN) serves to antagonize the PI3K pathway. Overlapping immune features of PTEN deficiency and APDS include high IgM, low IgG, increased transitional B cells, specific antibody deficiencies, autoimmunity, and lymphoproliferation. Because PTEN antagonizes PI3K activity, patients with PTEN loss-of-function mutations exhibit a similar phenotype to those with gain-of-function mutations of PI3K and can respond to mTOR inhibition like APDS patients. Overactivation of PI3K due to PTEN deficiency can lead to generalized immune dysregulation. Here we describe a patient with PTEN deficiency who presents as a phenocopy of APDS1 patients. MethodsRetrospective chart review was performed to obtain data on clinical labs of the PTEN deficient patient and APDS1 patients who presented with a similar clinical phenotype. An Epstein-barr virus (EBV) transformed B cell line (BLCL) was created from the patient PBMCs for functional studies to evaluate the PBK/AIKT/mTOR pathway. Patients were consented on an IRB approved protocol. ResultsThe patient was referred to immunology clinic for autoimmune cytopenias (Evan’s syndrome) and hypogammaglobulinemia. WES revealed De novo heterozygous c.406T>C (p.C136R) pathogenic variant in PTEN. Immune profiling showed elevated transitional B cells, increased naïve B cells and a decreased amount of class-switched memory B cells along with hyper IgM and low IgG. An abdominal ultrasound revealed significant splenomegaly with peri-splenic lymphadenopathy and hyper-echoic lesions in the spleen. Functional studies on BLCLs were reserved for confirmation of dysregulated PI3k/AKT/pS6 signaling. The patient was treated with sirolimus and IgG replacement therapy. After sirolimus therapy, lymphoproliferation and splenic findings resolved. DiscussionPTEN deficiency is a clinical and mechanistic phenocopy of APDS1 due to loss of negative regulation by PTEN to control over-activation of PI3 K. While Evan’s syndrome is reported in APDS1 more readily, it is not as prominent in PTEN. Treatment strategies employed for APDS1 and 2 are viable options for controlling the disease manifestations seen in PTEN deficiency.

Longitudinal Analysis of Cancer Risk in Children and Adults With Germline PTEN Variants

Identifying hereditary cancer predisposition facilitates high-risk organ-specific cancer surveillance and prevention. In PTEN hamartoma tumor syndrome (PHTS), longitudinal studies remain lacking, and there are insufficient data on cancers in children and young adults, as well as individuals with neurodevelopmental disorders (NDD). To evaluate lifetime cancer risks, including second malignant neoplasms (SMN), among patients with PHTS. Prospective longitudinal cohort study (September 1, 2005, through January 6, 2022). General population risks from the Surveillance, Epidemiology, and End Results database. Patients with PHTS, molecularly defined as carrying germline PTEN variants, were accrued from community and academic medical centers throughout North America, South America, Europe, Australia, and Asia. Data were analyzed from July 2022 to February 2023. Review of physical and electronic medical records, and follow-up through clinical visits or telephone interviews. Lifetime cancer risks in PHTS relative to the general population. A total of 7302 patients were prospectively accrued, 701 of whom had germline PTEN variants (median [IQR] age at consent, 38 [12-52] years; 413 female patients [59%]). Longitudinal follow-up data could be obtained for 260 patients (37%), with a median (IQR) follow-up of 4 (2-8) years. Of the 701 patients, 341 (49%) received at least 1 cancer diagnosis, with 144 (42%) of those having SMN. The study found significantly elevated lifetime risks for breast (91%), endometrial (48%), thyroid (33%), kidney (30%), and colorectal cancers (17%), as well as melanoma (5%). Cancer diagnoses were also observed in children and young adults with PHTS (15%) and in patients with PHTS with neurodevelopmental disorders (11%). Elevated risks (P < .001) of thyroid (age-adjusted standardized incidence ratios [SIR], 32.1; 95% CI, 26.0-39.0), kidney (SIR, 26.5; 95% CI, 18.8-36.3), endometrial (SIR, 26.0; 95% CI, 19.5-34.1), breast (SIR, 20.3; 95% CI, 17.3-23.7), and colorectal (SIR, 7.9; 95% CI, 5.2-11.7) cancers, and melanoma (SIR, 6.3; 95% CI, 3.5-10.5) were observed. Of the 341 patients with PHTS with cancer, 51 (15%) had 1 or more cancers diagnosed at age 29 years or younger, and 16 (31.4%) of those developed SMN at final follow-up. Twenty-three patients with PHTS with NDD and cancer were identified, with 5 (22%) having developed SMN at final follow-up. Individuals with PHTS and NDD showed higher lifetime cancer risks compared with individuals with PHTS but without NDD (hazard ratio, 2.7; 95% CI, 1.7-4.2; P < .001). This cohort study found consistently elevated lifetime cancer risks in PHTS. Organ-specific surveillance should continue in patients with PHTS. Additional study is required to ascertain elevated cancer risks in patients with PHTS with NDD.

Abstract 3845: Structural mechanisms of how PTEN mutations degrade function at the membrane and life expectancy of carriers of mutations in the human brain

Abstract PTEN negatively regulates PI3K/AKT/mTOR signaling through dephosphorylation of PIP3 to PIP2. PTEN dysfunction triggers disease phenotypes, ranging from cancer and PHTS to NDDs such as ASD. The most common PTEN mutations, nonsense, frameshift, and deletion/insertion, may cause premature termination of translation. PTEN has a considerable number of missense mutations that may result in loss of protein function through reduced catalytic activity and protein stability. To decipher mechanistic details of the mutations and structural features of the mutant proteins, comprehensive computational studies were performed for PTEN mutants at an anionic lipid bilayer containing PC, PS, PIP2, and PIP3. Six PTP mutations (Y68H, H93R, A126T, R130Q, G132D, R173C) and two C2 mutations (F241S, D252G) were considered. The PTP mutations are known to associate with cancer, PHTS, macrocephaly, and ASD, while the C2 mutations are exclusively related to macrocephaly and ASD. Our studies indicate that the PTEN mutants can effectively absorb the anionic lipid bilayer, similar to wild-type PTEN. However, Y68H significantly disrupts the core of PTP domain, reducing protein stability. H93R hijacks the substate PIP3, interrupting the catalytic site residues recruitment of the substate for catalysis. A126T, R130Q, and G132D in the P loop directly influence the dynamics of the loop, yielding a collapsed loop conformation. The collapsed P loop loses the interaction with the WPD loop, leading to dehydration in the catalytic site. R173C and D252G at the interface between two major domains disrupt the domain-domain interaction, allosterically biasing the P loop dynamics. However, F241S in C2 exhibits less effective allosteric connection to the catalytic site than that observed in the wild type. PCA of the sampled conformations found that the macrocephaly and ASD-related H93R and F241S are likely to sample the conformations present in the wild type. In contrast, the sampled conformations for the cancer and PHTS-related Y68H, A126T, and G132D are different from those for the wild type. These distinct structural features seem to correlate with mutation strength and timing of the expression of the genes that determine the cancer and NDD outcomes. The isoform expression data extracted from the BrainSpan indicate that exon 5 is impacted by NDD or non-NDD mutations. Interestingly, PTEN splicing isoforms that do not carry exon 5 are exclusively impacted by the NDD mutations, F241S and D252G. The increased life expectancy of PTEN variants carriers carrying exons 5 and 7 is highly correlated to increased lifetime risk for certain cancers. Our results underscore the detailed structural and functional mechanisms of PTEN with mutations at the membrane, and suggest that tissue-specific splicing isoform expression should be taken into consideration while predicting the effect of mutations in various diseases. Citation Format: Hyunbum Jang, Jiaye Chen, Lilia M. Iakoucheva, Ruth Nussinov. Structural mechanisms of how PTEN mutations degrade function at the membrane and life expectancy of carriers of mutations in the human brain. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3845.

Racial/ethnic differences of germline pathogenic variants in cancer susceptibility genes among patients with early-onset colorectal cancer.

19 Background: The burden of early-onset colorectal cancer (CRC diagnosed before age 50 years) differs across racial/ethnic groups. Yet the distinct prevalence and spectrum of germline pathogenic variants associated with early-onset CRC by race/ethnicity is uncharacterized. Methods: We identified 3,980 early-onset CRC patients unselected for family CRC history who underwent clinical multi-gene panel testing of 14 CRC susceptibility genes ( MLH1, MSH2, MSH6, PMS2, SMAD4, APC, BMPR1, CHEK2, EPCAM, MUTYH, PTEN, STK11, CDH1, and TP53) performed by a nationwide clinical testing laboratory from 2012 to 2016 and identified as Ashkenazi Jewish, Asian, Black, Hispanic, or White. Multi-gene panel testing was performed by targeted custom capture and sequencing and chromosome rearrangement analysis. Clinical and individual/family histories were ascertained from clinician-completed test requisition forms. Germline variant prevalence and spectrum in early-onset CRC was determined by race/ethnicity. Pathogenic variant comparisons by race/ethnicity were evaluated using chi-square tests and multivariable logistic regression adjusted for sex, age, CRC site and sequence. Results: Among 3,980 early-onset CRC patients, a total of 503 germline genetic variants were identified in 481 individuals (12.1%). By race/ethnicity, 12.7% of Ashkenazi Jewish, 8.6% of Asian, 10.3% of Black, 14.0% of Hispanic, and 12.3% of White individuals presented with a pathogenic variant in a CRC susceptibility gene. Nearly 7% of early-onset CRC patients (n = 268) presented with a germline pathogenic mutation in a mismatch repair gene—with the prevalence of Lynch Syndrome in early-onset CRC differing across racial/ethnic groups ( P= 0.037). The prevalence of germline APC, CHEK2, MLH1, monoallelic MUTYH, and PTEN variants also varied by race/ethnicity (all P&lt; 0.02). Overall, Asian individuals with early-onset CRC had 49% lower odds of carrying a pathogenic germline variant in a CRC susceptibility gene versus White individuals in adjusted models (Odds Ratio [OR] = 0.51, 95% Confidence Interval [CI]: 0.26-0.99, P= 0.046). Ashkenazim and Hispanic individuals had higher odds of presenting with pathogenic APC and MLH1 variants, respectively, compared with White individuals in adjusted models ( APC: OR = 8.69, 95% CI: 2.68-28.21, P= 0.0003; MLH1: OR = 2.67, 95% CI: 1.30-5.49, P= 0.007). Conclusions: Of 3,980 patients with early-onset CRC unselected for family history, the prevalence and spectrum of pathogenic germline variants differed across racial/ethnic populations. Beyond multigene panel testing for all early-onset CRC patients, further study is needed to optimize genes selected for germline genetic testing in early-onset CRC across diverse groups—which would have clinical implications for disease surveillance and intervention.

Pathologists’ overview of prior biopsies of women with germline PTEN mutations may expedite the identification of this rare cancer predisposition syndrome

PTEN hamartoma tumour syndrome (PHTS) is a rare cancer predisposition syndrome, caused chiefly by pathogenic and likely pathogenic (P/LP) variants in the PTEN gene. The rarity of this disease, involvement of multiple sites and the absence of pathognomonic features hamper early diagnosis, limiting opportunities for cancer screening. We wondered whether PHTS patients’ prior biopsies may provide clues to this syndrome. With ethics approval, through a collaboration with our state-wide Adult Genetics Unit, we undertook a 28-year survey (1990–2018) of prior biopsies of 12 women known to have P/LP PTEN variants. One woman had a family history of PHTS. The earliest biopsy was at age 19. Multiple benign mucocutanous lesions affected 10 women, including benign vascular lesions: eight patients, fibromatous skin and mucosal lesions: six patients, one ganglioneuroma and one juvenile polyp. Ten women developed breast cancer, four under 40 years. Five women developed a second breast cancer, two synchronously and three at interval of 3–11 years. Other neoplasms included endometrial carcinoma two patients and dysplastic cerebellar gangliocytoma three patients. Overview of the biopsy histories of PTEN P/LP variant carriers may be a clue to the diagnosis, so clinical and genetic counselling and evaluation may be considered.