Spectrum Of Mutations Research Articles

Clinical features and genetic analysis of 15 Chinese children with dent disease

Objective The clinical characteristics, genetic mutation spectrum, treatment strategies and prognoses of 15 children with Dent disease were retrospectively analyzed to improve pediatricians’ awareness of and attention to this disease. Methods We analyzed the clinical and laboratory data of 15 Chinese children with Dent disease who were diagnosed and treated at our hospital between January 2017 and May 2023 and evaluated the expression of the CLCN5 and OCRL1 genes. Results All 15 patients were male and complained of proteinuria, and the incidence of low-molecular-weight proteinuria (LMWP) was 100.0% in both Dent disease 1 (DD1) and Dent disease 2 (DD2) patients. The incidence of hypercalciuria was 58.3% (7/12) and 66.7% (2/3) in DD1 and DD2 patients, respectively. Nephrocalcinosis and nephrolithiasis were found in 16.7% (2/12) and 8.3% (1/12) of DD1 patients, respectively. Renal biopsy revealed focal segmental glomerulosclerosis (FSGS) in 1 patient, minimal change lesion in 5 patients, and small focal acute tubular injury in 1 patient. A total of 11 mutations in the CLCN5 gene were detected, including 3 missense mutations (25.0%, c.1756C > T, c.1166T > G, and c.1618G > A), 5 frameshift mutations (41.7%, c.407delT, c.1702_c.1703insC, c.137delC, c.665_666delGGinsC, and c.2200delG), and 3 nonsense mutations (25.0%, c.776G > A, c.1609C > T, and c.1152G > A). There was no significant difference in age or clinical phenotype among patients with different mutation types (p > 0.05). All three mutations in the OCRL1 gene were missense mutations (c.1477C > T, c.952C > T, and c.198A > G). Conclusion Pediatric Dent disease is often misdiagnosed. Protein electrophoresis and genetic testing can help to provide an early and correct diagnosis.

A novel pathogenic mitochondrial DNA variant m.4344T>C in tRNAGln causes developmental delay.

Mitochondrial diseases are a group of genetic diseases caused by mutations in mitochondrial DNA and nuclear DNA. However, the genetic spectrum of this disease is not yet complete. In this study, we identified a novel variant m.4344T>C in mitochondrial tRNAGln from a patient with developmental delay. The mutant loads of m.4344T>C were 95% and 89% in the patient's blood and oral epithelial cells, respectively. Multialignment analysis showed high evolutionary conservation of this nucleotide. TrRosettaRNA predicted that m.4344T>C variant would introduce an additional hydrogen bond and alter the conformation of the T-loop. The transmitochondrial cybrid-based study demonstrated that m.4344T>C variant impaired the steady-state level of mitochondrial tRNAGln and decreased the contents of mitochondrial OXPHOS complexes I, III, and IV, resulting in defective mitochondrial respiration, elevated mitochondrial ROS production, reduced mitochondrial membrane potential and decreased mitochondrial ATP levels. Altogether, this is the first report in patient carrying the m.4344T>C variant. Our data uncover the pathogenesis of the m.4344T>C variant and expand the genetic mutation spectrum of mitochondrial diseases, thus contributing to the clinical diagnosis of mitochondrial tRNAGln gene variants-associated mitochondrial diseases.

[Genetic analysis of a fetus with cryptophthalmos due to variants of FREM2 gene].

To explore the genetic etiology of a fetus with cryptophthalmos detected by prenatal ultrasonography. A fetus undergoing induced labor at 32nd gestational week due to absence of bilateral eye fissures detected by prenatal ultrasonography in January 2017 was selected as the study subject. Umbilical cord blood sample from the fetus and peripheral blood samples from its parents were collected for the extraction of genomic DNA. Pathogenic variants were screened through whole exome sequencing (WES) and verified by Sanger sequencing. Pathogenicity of candidate variants was verified by bioinformatic analysis and protein structure simulation. Based on the results of genetic testing, prenatal diagnosis was provided to the couple upon their subsequent pregnancy. The couple had four adverse pregnancies previously. The aborted fetus was the fifth, with fused bilateral upper and lower eyelids, poorly developed eyeballs, adhesion of the cornea with the upper eyelid, low-set ears, and abnormal plantar creases, and was diagnosed with cryptophthalmos. WES and Sanger sequencing revealed that the fetus has harbored compound heterozygous variants of the FREM2 gene, namely c.4537G>A (p.D1513N) and c.7292C>T (p.T2431M). Both variants were unreported associated with cryptophthalmos previously. Protein structure simulation showed that they may lead to loss of hydrogen bonds in the protein product. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), both variants were predicted to be likely pathogenic (PM1_Supporting+PM2_Supporting+PM5+PP3+PP4; PM2_Supporting+PM3+PP3+PP4). The mother was performed prenatal diagnosis in her sixth pregnancy based on the variants detected in this family, and delivered a daughter with normal phenotype. The FREM2: c.4537G>A and c.7292C>T compound heterozygous variants probably underlay the pathogenesis of cryptophthalmos in this fetus. Above finding has enriched the mutational spectrum of the FREM2 gene.

[Clinical and genetic analysis of a patient with Baraitser-Winter syndrome due to variant of ACTG1 gene].

To explore the clinical features and genetic etiology of a child with Baraitser-Winter syndrome (BWS). A BWS child who had sought medical attention at the Linyi People's Hospital on April 8, 2022 was selected as the study subject. Clinical data of the child was collected, and peripheral blood samples were obtained from the child and his parents. Whole exome sequencing (WES) was carried out, and candidate variant was verified by Sanger sequencing and bioinformatic analysis. The child, a 5-year-and-6-month-old male, had typical clinical features of BWS including congenital non-myogenic ptosis, arched eyebrows, wide philtrum, and pointed chin. Neurological symptoms included microcephaly, developmental delay, epilepsy, and deafness. Cranial MRI revealed enlarged frontal lobes, decreased white matter, and hydrocephalus. WES has identified a heterozygous c.430G>A (p.Asn144Tyr) missense variant in the ACTG1 gene. Sanger sequencing confirmed that neither of his parents has carried the same variant. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was classified as likely pathogenic (PS2+PM2_Supporting+PP3_Moderate+PP4). The heterozygous c.430G>A (p.Asn144Tyr) missense variant of the ACTG1 gene probably underlay the pathogenesis of BWS in this child. Above finding has enriched the mutation spectrum of BWS-related genes and provided a basis for clinical diagnosis and genetic counseling.

Clinical features and mutational spectrum of Chinese patients with primary hyperoxaluria type 2.

Primary hyperoxaluria type 2 (PH2) is a rare hereditary disease that causes nephrolithiasis, nephrocalcinosis and kidney failure. This study aimed to investigate the clinical features and mutational spectrum of Chinese patients with PH2. A retrospective cohort study was performed on PH2 patients admitted to our center over seven years. We also systematically reviewed all the articles on Chinese PH2 patients published from January 2000 to May 2023 and conducted a meta-analysis. A total of 25 PH2 patients (10 from our center and 15 from published studies) were included in this study. The median age of onset in patients from our center was 8.50 (1.00, 24.00) years, and 50% were male. Among the full cohort of 25 Chinese patients, the median age of onset was 8.00 (0.40, 26.00) years, and 64% of them were male. Seven patients progressed to end-stage kidney disease, with a median age of 27.50 (12, 31) years. The cumulative renal survival rates were 100%, 91.67%, 45.83% and 30.56% at 10, 20, 30 and 40 years of age, respectively. A total of 18 different variants were identified, and c.864_865del was the dominant variant, accounting for 57.69% of the total alleles. Patients who were heterozygous for c.864_865del were more susceptible to nephrocalcinosis than those who were homozygous for c.864_865del and those harboring other mutations (83.33% versus 33.3% and 0%, respectively) (p = 0.025). The clinical features and mutational spectrum of Chinese PH2 patients were described. This study helps to expand awareness of the phenotypes and genotypes of Chinese PH2 patients and contributes to the improvement of diagnostic and treatment strategies for PH2 patients.

[Genetic analysis of a Chinese pedigree affected with Brachydactyly type B1 due to a novel variant of ROR2 gene].

To explore the genetic basis for a Chinese pedigree affected with Brachydactyly type B1 (BDB1) through whole exome sequencing (WES). A BDB1 pedigree admitted to the Affiliated Women and Children's Hospital of Qingdao University on June 25, 2021 was selected as the study subject. Clinical data of the pedigree was collected with informed consent. WES was carried out for the proband, and candidate variant was verified by Sanger sequencing and bioinformatic analysis. WES and Sanger sequencing had identified a heterozygous c.2257delT variant in the ROR2 gene of the proband and his affected father, which has conformed to an autosomal dominant pattern of inheritance. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was classified to be likely pathogenic (PVS1_Strong+PM2 Supporting+PP4). The c.2257delT variant of the ROR2 gene was unreported previously and is strongly correlated with the BDB1-like phenotype in this pedigree. Above finding has enriched the mutational spectrum of the ROR2 gene and facilitated the diagnosis and genetic counseling for this pedigree.

A novel NTRK1 splice site variant causing congenital insensitivity to pain with anhidrosis in a Chinese family

BackgroundCongenital insensitivity to pain with anhidrosis (CIPA, OMIM #256800), also known as hereditary sensory and autonomic neuropathy type Ⅳ (HSAN-IV), is a rare autosomal recessive disorder characterized by recurrent episodic fevers, anhidrosis, insensitivity to noxious stimuli, self-mutilating behavior and intellectual disability. CIPA can be caused by the variants in NTRK1 gene, which encodes a high-affinity tyrosine kinase receptor for nerve growth factor. To ascertain the hereditary cause of a patient with CIPA accompanied by the additional symptoms of mild growth retardation, prone to fracture, underdeveloped nails of fingers and toes, irregular tooth alignment, enamel hypoplasia, postoperative wound healing difficulty, hand and limb deformity, and dislocation of hip joint, whole exome sequencing was used and revealed a compound heterozygous variant in NTRK1.MethodsDNA was extracted from peripheral blood samples of pediatric patients and their parents, and subjected to comprehensive analysis using whole-exome sequencing (WES), followed by verification of variant sites in the NTRK1 gene through Sanger sequencing. To elucidate the functional impact of the newly discovered variants, an in vitro experimental system was established. Splicing analysis was conducted using PCR and Sanger sequencing, while expression levels were assessed through qPCR and Western blot techniques.ResultsOne hotspot variant c.851-33T>A(ClinVar ID: 21308) and a novel variant c.850 + 5G>A(ClinVar ID:3069176) was inherited from her father and mother, respectively, identified in the affected individuals. The c.850 + 5G>A variant in NTRK1 resulted in two forms of aberrant mRNA splicing: 13bp deletion (c.838_850del13, p. Val280Ser fs180) and 25bp deletion (826_850del25, p. Val276Ser fs180) in exon 7, both leading to a translational termination at a premature stop codon and forming a C-terminal truncated protein. The expression of two abnormal splicing isoforms was decreased both in the level of mRNA and protein.ConclusionIn conclusion, this study elucidated the genetic cause of a patient with CIPA and identified a novel variant c.850 + 5G>A in NTRK1, which broadened the and enriched the NTRK1 mutation spectrum.

[Clinical analysis and genetic diagnosis of three children with Isoleucine metabolic disorders due to variants of HSD17B10 and ACAT1 genes].

To explore the clinical, biochemical and genetic characteristics of three children with Isoleucine metabolic disorders due to variants of HSD17B10 and ACAT1 genes. Two children with 17β hydroxysteroid dehydrogenase 10 (HSD17B10) deficiency and a child with β-ketothiolase deficiency (BKD) diagnosed at Shanghai Children's Hospital between 2014 and 2021 were selected as the study subjects. Clinical data of the children were collected. The children were subjected to blood acylcarnitine, urinary organic acid and genetic testing, and candidate variants were analyzed with bioinformatic tools. The main symptoms of the three children had included epilepsy, developmental delay, hypotonia and acidosis. Their blood acylcarnitine methylcrotonyl carnitine (C5:1), 3-hydroxyisovalerylcarnitine (C5-OH) and 3-hydroxybutylcarnitine (C4OH) were increased to various extents, and urine organic acids including methyl crotonylglycine and 2-methyl-3-hydroxybutyric acid were significantly increased. Child 1 and child 2 were respectively found to harbor a c.347G>A (p.R116Q) variant and a c.274G>A (p.A92T) variant of the HSD17B10 gene, and child 3 was found to harbor compound heterozygous variants of the ACAT1 gene, namely c.547G>A (p.G183R) and a c.331G>C (p.A111P). Among these, the c.274G>A (p.A92T) and c.331G>C (p.A111P) variants were unreported previously. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), they were respectively classified as variant of unknown significance (PP3_Strong+PM2_supporting) and likely pathogenic (PM3+PM2_Supporting+PP3_Moderate+PP4). Both the HSD17B10 deficiency and BKD can lead to Isoleucine metabolism disorders, which may be difficult to distinguish clinically. Genetic testing can further confirm the diagnosis. Discoveries of the HSD17B10: c.274G>A (p.A92T) variant and the ACAT1: c.331G>C (p.A111P) variant have enriched the mutational spectrum of the two diseases.

[Genetic analysis of a child with Multiple congenital anomalies-hypotonia-seizures syndrome 1 due to variant of PIGN gene].

To analyze the clinical phenotype and genetic etiology of a child with Multiple congenital anomalies-hypotonia-seizures syndrome 1 (MCAHS1). Clinical data of a 2-year-old boy who had presented at the Affiliated Hospital of Qingdao University in March 2023 for "intermittent limb twitching for 2 years" was collected. Peripheral blood samples were collected from the child and his parents for whole-exome sequencing (WES). Candidate variants were verified by Sanger sequencing and bioinformatic analysis based on the guidelines from the American College of Medical Genetics and Genomics (ACMG). The child had manifested with distinctive facial features, limb deformities, hypotonia, motor and intellectual delays, and epileptic seizures. WES revealed that he has harbored compound heterozygous variants of the PIGN gene, namely c.963G>A (p.Q321=) and c.994A>T (p.I332F), which were inherited from his phenotypically normal mother and father, respectively. Based on the ACMG guidelines, the c.963G>A was classified as a pathogenic variant (PVS1+PM2_Supporting+PM3), whilst the c.994A>T was classified as a variant of uncertain significance (PM2_Supporting+PP3). Above discovery has expanded the mutational spectrum of the PIGN gene variants associated with MCAHS1, which may facilitate delineation of its genotype-phenotype correlation.

Clinico-genomic findings, molecular docking, and mutational spectrum in an understudied population with breast cancer patients from KP, Pakistan

In this study, we report the mutational profiles, pathogenicity, and their association with different clinicopathologic and sociogenetic factors in patients with Pashtun ethnicity for the first time. A total of 19 FFPE blocks of invasive ductal carcinoma (IDC) from the Breast Cancer (BC) tissue and 6 normal FFPE blocks were analyzed by whole-exome sequencing (WES). Various somatic and germline mutations were identified in cancer-related genes, i.e., ATM, CHEK2, PALB2, and XRCC2. Among a total of 18 mutations, 14 mutations were somatic and 4 were germline. The ATM gene exhibited the maximum number of mutations (11/18), followed by CHEK2 (3/18), PALB2 (3/18), and XRCC2 (1/18). Except one frameshift deletion, all other 17 mutations were nonsynonymous single-nucleotide variants (SNVs). SIFT prediction revealed 7/18 (38.8%) mutations as deleterious. PolyPhen-2 and MutationTaster identified 5/18 (27.7%) mutations as probably damaging and 10/18 (55.5%) mutations as disease-causing, respectively. Mutations like PALB2 p.Q559R (6/19; 31.5%), XRCC2 p.R188H (5/19; 26.31%), and ATM p.D1853N (4/19; 21.05%) were recurrent mutations and proposed to have a biomarker potential. The protein network prediction was performed using GeneMANIA and STRING. ISPRED-SEQ indicated three interaction site mutations which were further used for molecular dynamic simulation. An average increase in the radius of gyration was observed in all three mutated proteins revealing their perturbed folding behavior. Obtained SNVs were further correlated with various parameters related to the clinicopathological status of the tumors. Three mutation positions (ATMp. D1853N, CHEK2 p.M314I, and PALB2 p.T1029S) were found to be highly conserved. Finally, the wild- and mutant-type proteins were screened for two drugs: elagolix (DrugBank ID: DB11979) and LTS0102038 (a triterpenoid, isolated from the anticancer medicinal plant Fagonia indica). Comparatively, a higher number of interactions were noted for normal ATM with both compounds, as compared to mutants.

Identification of rare and novel PHEX variants in X-linked hypophosphatemia.

X-linked hypophosphatemia (XLH) is a rare metabolic bone disease caused by inactivation mutations in the PHEX gene. Despite the extensive number of reported PHEX variants, only a few cases of chromosomal abnormalities have been documented. We aimed to identify the pathogenic variants in six unrelated families with a clinical diagnosis of XLH and to propose a genetic workflow for hypophosphatemia patients suspected of XLH. Multiple genetic testing assays were used to analyze the six families' genetic profiles, including whole exome sequencing, multiplex ligation-dependent probe amplification, whole genome sequencing, reverse transcript polymerase chain reaction, Sanger sequencing, and karyotyping. The study identified six novel pathogenic variants, including one mosaic variant (exon 16-22 deletion), three chromosomal abnormalities (46, XN, inv[X][pter→p22.11::q21.31→p22.11::q21.31 →qter], 46, XN, inv[X][p22.11p22.11], and XXY), a nonclassical intron variant (NM_000444.6, c.1701_31A > G), and a deletion variant (NM_000444.6, c.64_5464-186 del5215) of PHEX. Additionally, a genetic testing workflow was proposed to aid in diagnosing patients suspected of XLH. Our research expands the mutation spectrum of PHEX and highlights the significance of utilizing multiple genetic testing methods to diagnose XLH.

Novel WFS1 Variants in Two Moroccan Families with Wolfram Syndrome

Novel <i>WFS1</i> Variants in Two Moroccan Families with Wolfram Syndrome

Genotype-phenotype association and functional analysis of hnRNPA1 mutations in amyotrophic lateral sclerosis

Background Pathogenic variants in hnRNPA1 have been reported in amyotrophic lateral sclerosis (ALS) patients. However, studies on hnRNPA1 mutant spectrum and pathogenicity of variants were rare. Methods We performed whole exome sequencing of ALS-associated genes and subsequent verification of rare variants in hnRNPA1 in our ALS patients. The hnRNPA1 mutations reported in literature were reviewed and combined with our results to determine the genotype-phenotype relationship. Functional analysis of the novel variant p.G195A was performed in vitro by transfection of mutant hnRNPA1 into 293T cell. Results Among 207 ALS patients recruited, 3 rare hnRNPA1 variants were identified (mutant frequency 1.45%), including two recurrent mutations (p.P340S and p.G283R), and a novel rare variant p.G195A. In combination with previous reports, there are 27 ALS patients with 15 hnRNPA1 mutations identified. Disease onset age was 47.90 ± 1.52 years with predominant limb onset. The p.P340S mutation caused flail arm syndrome (FAS) in two independent families with extended life expectancy. The newly identified p.G195A mutation, lying at the start of the PrLD (“prion-like” domain)/LCD (low-complexity domain), causes local structural changes in 3D protein prediction. Upon sodium arsenite exposure, mutant hnRNPA1 retained in the nucleus but deficit of cytoplasmic G3BP1-positive stress granule clearance was observed. This is different from the p.P340S mutation which caused both cytoplasmic translocation and stress granule formation. No cytoplasmic TDP-43 translocation was observed. Conclusion Mutations in hnRNPA1 are overall minor in ALS patients. The p.P340S mutation is associated with manifestation of FAS. Mutations in LCD of hnRNPA1 cause stress granule misprocessing.

Genetic and clinical profile of 15 Chinese families with GDAP1-related Charcot-Marie-Tooth disease and identification of H256R as a frequent mutation.

Mutations in ganglioside-induced differentiation-associated protein 1 (GDAP1) cause axonal or demyelinating Charcot-Marie-Tooth disease (CMT) with autosomal dominant or recessive inheritance. In this study, we aim to report the genotypic and phenotypic features of GDAP1-related CMT in a Chinese cohort. Clinical, neurophysiological, genetic data, and available muscle/brain imaging information of 28 CMT patients with GDAP1 variants were retrospectively collected. We identified 16 GDAP1 pathogenic variants, among which two novel variants c.980dup(p.L328FfsX25) and c.480+4T>G were first reported. Most patients (16/28) presented with AR or AD CMT2K phenotype. Clinical characteristics in our cohort demonstrated that the AR patients presented earlier onset, more severe phenotype compared with the AD patients. Considerable intra-familial phenotypic variability was observed among three AD families. Muscle atrophy and fatty infiltration in the lower extremity were detected by Muscle magnetic resonance imaging (MRI) scans in four patients. MRI showed two AR patients showed more severe muscle involvement of the posterior compartment than those of the anterolateral compartment in the calf. One patient carrying Q38*/H256R variants accompanied with mild periventricular leukoaraiosis. In this study, we conducted an analysis of clinical features of the GDAP1-related CMT patients, expanded the mutation spectrum in GDAP1 by reporting two novel variants, and presented the prevalent occurrence of the H256R mutation in China. The screening of GDAP1 should be particularly emphasized in Chinese patients with CMT2, given the incomplete penetrance and pathogenic inheritance patterns involving dominant and recessive modes.

Detection of Oncogene Hotspot Mutations in Female NSCLC Tumor DNA and Cell-Free DNA.

Non-small-cell lung cancer (NSCLC) is the most prevalent type of lung cancer, with extensively characterized mutational spectra. Several biomarkers (such as EGFR, BRAF, KRAS gene mutations, etc.) have emerged as predictive and prognostic markers for NSCLC. Unfortunately, the quality of the available tumor biopsy and/or cytology material is not always adequate to perform the necessary molecular testing, prompting the search for alternatives. Cell-free DNA (cfDNA) found in plasma is emerging as a highly promising avenue or a supplementary method for assessing the efficacy of cancer treatments. This is especially valuable in instances where conventional biopsy specimens, like formalin-fixed, paraffin-embedded (FFPE), or freshly frozen tumor tissues prove inadequate for conducting molecular pathology analyses subsequent to the initial diagnostic procedures. By leveraging cfDNA from plasma, clinicians gain an additional tool to gauge the effectiveness of cancer therapies, thereby enhancing their ability to optimize tailored treatment strategies. In this study, 51 Lithuanian females with NSCLC were analyzed, with adenocarcinoma being the predominant pathology diagnosis in 40 cases (78%). Target mutations were identified in 38 out of 51 patients (74.5%) in tumor tissue samples, while in plasma samples, they were identified in only 10 patients' samples (19.6%). Even though we did not have enough voluminous plasma samples in our study, gene mutations were detected in plasma from ten women, three of whom were diagnosed with early stages of lung cancer (stages I and II). For these patients, the following mutations were detected: deletion in exon 19 of the EGFR gene and single nucleotide polymorphisms in the TP53 and MET genes. All other women were diagnosed with stages III or IV of lung cancer. This indicates that the later stages of cancer contribute more cfDNA in plasma, making extraction less complicated.

A de novo Mutation (p.Gln277X) of Cyclin D2 is Responsible for a Child with Megalencephaly-Polymicrogyria-Polydactyly-Hydrocephalus Syndrome.

Megalencephaly-polymicrogyria-polydactyly-hydrocephalus syndrome (MPPH), a type of overgrowth syndrome, is characterized by progressive megalencephaly, cortical brain malformations, and distal limb anomalies. Previous studies have revealed that the overactivity of the phosphatidylinositol 3-kinase-Protein kinase Bpathway and the increased cyclin D2 (CCND2) expression were the main factors contributing to this disease. Here, we present the case of a patient who exhibited megalencephaly, polymicrogyria, abnormal neuronal migration, and developmental delay. Serum tandem mass spectrometry and chromosome examination did not detect any metabolic abnormalities or copy number variants. However, whole-exome sequencing and Sanger sequencing revealed a de novo nonsense mutation (NM_001759.3: c.829C>T; p.Gln277X) in the CCND2 gene of the patient. Bioinformatics analysis predicted that this mutation may disrupt the structure and surface charge of the CCND2 protein. This disruption could potentially prevent polyubiquitination of CCND2, leading to its resistance against degradation. Consequently, this could drive cell division and growth by altering the activity of key cell cycle regulatory nodes, ultimately contributing to the development of MPPH. This study not only presents a new case of MPPH and expands the mutation spectrum of CCND2 but also enhances our understanding of the mechanisms connecting CCND2 with overgrowth syndromes.

Abstract PO5-16-01: Clinicogenomic analysis reveals genomic associations of brain metastatic tropism in breast cancer

Abstract Introduction: Recent progress in imaging and therapeutics has led to improvements in the treatment of advanced breast cancer. However, the incidence of brain metastasis (BM) in breast cancer is increasing and continues to be associated with poor prognosis and significant morbidity. Herein, we describe genomic enrichments associated with brain tropism from a large institutional clinico-genomic cohort. Methods: Patients who underwent tumor and matched normal sequencing utilizing hybridization-capture based targeted exonic sequencing (MSK-IMPACT) from April 2014 to March 2023 were included in this analysis; this cohort included 6,377 samples from 5,135 patients. We analyzed genomic data to inform the full spectrum of somatic and germline mutations, copy number changes and structural variants enriched in samples in resected BM specimens (n = 179), compared to primary tumors (n = 2980), stratified by receptor status. Enrichment analysis was conducted using a Fisher exact test for each respective receptor status. Similar analyses were conducted between extracranial metastatic (ECM) sites (n = 3186) and primary tumors, to differentiate the unique genomic features driving the emergence of BM as compared to general metastatic propensity. Multiple hypothesis testing was performed using Benjamini-Hochberg. Further genomic analysis, including allele specific copy number changes and mutational signatures will be reported at the 2023 SABCS meeting. Results: Oncogenic alterations in several genes were found to be enriched in BM samples compared to primary tumor, with an odds ratio exceeding that of the corresponding ECM comparison. For example, in the HR+/HER2- subset (4329 samples from 3476 patients), pathogenic variants in the following genes were enriched in BM:Primary analysis: NF1 (OR 6.4 [2.9 – 13.7], q = 0.001, 15.5% of BM), MYC (OR 3.9 [2.0 – 7.4], q = 0.001, 24.4% of BM), AGO2 (5.2 [2.4 – 10.9], q= 0.002, 15.5% of BM), CDKN2A (OR 3.9 [1.6 – 9.4], q = 0.06, 10.3% of BM), ERBB2 (OR 3.6 [1.5 – 8.6], q = 0.06, 10.3% of BM), RB1 (OR 4.2 [1.5 – 11.4], q = 0.06, 8.6% of BM), TP53 (OR 2.0 [1.1 – 3.5], q = 0.07, 40% of BM). In contrast, ESR1 variants were enriched in BM:Primary (OR 14.0 [6.7 – 28.2], but at the same level as ECM:Primary (OR 12.3 [8.7 – 17.7]). When considering HER2+ tumors (919 samples from 739 patients), only NKX.3 was enriched in the BM:Primary comparison (OR 11.5 [3.2 – 42.3], q = 0.004, 11.6% of BM). Although no TNBC samples met significance thresholds after adjustment for multiple hypothesis testing, CDH1, NTRK1, EGFR, and TP53 emerged as putatively significant. Conclusions: In a large cohort of genomically-profiled breast cancer samples, we find recurrent involvement of genes involved in cell cycle regulation (RB1, CDKN2A, TP53); these have been found to be enriched in brain metastases from other cancer types and are implicated in resistance to common lineage-directed therapies. Our approach also uncovered several targets for which therapies are actively in development (ERBB2, MYC). Further study of genomic evolution of breast cancer in the context of brain metastasis and therapeutic resistance will uncover conserved site-specific genomic changes and will identify novel, rational therapeutic targets. Citation Format: Anton Safonov, Deborah Smith, Emanuela Ferraro, Junchao Shen, Ishaani Khatri, Rahul Kumar, Julia An, Mark Robson, Sarat Chandarlapaty, Adrienne Boire, Nikolaus Schultz, Nelson Moss, Luke Pike, Pedram Razavi. Clinicogenomic analysis reveals genomic associations of brain metastatic tropism in breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-16-01.

Abstract PO2-16-03: ESR1 genomic alterations (GAs) and coexistent putative resistance alterations in comprehensive genomic profiling (CGP) of metastatic breast cancer (MBC)

Abstract Background: ESR1 mutations (ESR1mut) are an established biomarker of endocrine therapy (ET) resistance in patients (pts) with hormone receptor positive (HR+) MBC. Moreover, ESR1mut acquired in response to standard-of-care ET now confer access to novel ET recently approved by health authorities. However, the nuanced genomic landscape beyond the simple presence or absence of ESR1mut may be critically important. We report on detailed ESR1 GAs detected by tissue and liquid biopsies (TBx, LBx) and examine the prevalence of co-occurring GAs in other genes reported to confer intrinsic or acquired resistance to ET. Methods: CGP results from MBC biopsies were retrospectively analyzed (TBx 33,653 pts; LBx 7,134 pts) using FoundationOne® CDx and FoundationOne® Liquid CDx, hybrid-capture based sequencing platforms profiling 324 cancer-related genes. Foundation Medicine’s ctDNA tumor fraction (TF) is a composite algorithm prioritizing aneuploidy at higher levels to avoid germline signal and prioritizing variant allele frequency (VAF) of canonical alterations at lower levels to maximize dynamic range. Results: ESR1mut were detected in 3,755 (11.2%) TBx and 1,513 (21.2%) LBx. Among samples with ESR1mut, multiple ESR1mut were more common in LBx (19% 2, 12% 3+) than in TBx (6% 2, 0.5% 3+), with up to 10 different ESR1mut seen in one LBx. The most common mutations were D538G (39% and 52% of TBx and LBx with ESR1mut), Y537S (27%, 38%), Y537N (10%, 15%), and E380Q (10%, 14%). Activating ESR1 insertion-deletion mutations (indels) were detected in 81 TBx and 62 LBx (2% and 4%), representing 23 distinct variants at the protein level, including V422del (107), indels affecting codons 532-538 (29), G344_L345insC (7), and Y328_S329del (6). 28 fusions of the ESR1 DNA binding domain to 13 unique gene partners were detected; 10/28 (36%) were ESR1-CCDC170 fusions. ESR1 amplifications (ESR1amp) were detected in 704 (2.1%) TBx; 62 (8.8%) also harbored ESR1mut. ESR1amp were detected among 34 (0.5%) LBx; 8 (24%) also had ESR1mut. In TBx with ESR1mut and LBx collected from the same pt within 8 months (43 pairs), LBx sensitivity of detection of ESR1mut was 96% (26/27, 95% confidence interval CI [95%CI]: 79%-99%) when TF was ≥1%, but only 6% (1/16, 95%CI: 0.3%-32%) when LBx had TF &amp;lt; 1%. In 988/1,513 (65%) of LBx with ESR1mut, ≥1 mutations or fusions in genes associated with alternative ET resistance pathways were detected, including PIK3CA (46% of ESR1mut LBx), RB1 (12%), PTEN (10%), NF1 (7%), ARID1A (7%), AKT1 (5%), FGFR2 (4%), and KRAS (4%) and ERBB2 (3%). Prevalence of co-occurring GA associated with ET resistance was higher in LBx than in TBx (RB1, NF1, FGFR2, PTEN, EGFR, KRAS, PIK3CA, FDR &amp;lt; 0.001). Moreover, prevalence was higher in 240 LBx where ESR1 was a minor allele (VAF/TF &amp;lt; 10%) compared to 1,273 LBx were ESR1 was a major allele (FGFR2, PIK3CA, FGFR3, BRAF, ERBB2, RB1, FDR &amp;lt; 0.05). In pts with ESR1mut LBx and a historical TBx collected &amp;lt; 5 years earlier (182 pairs), GAs in RB1, FGFR2, KRAS, EGFR, and BRAF were detected primarily on the LBx but not the preceding TBx. Conclusions: CGP detects a wide spectrum of mutations in ESR1, including missense and indel mutations and fusions. When LBx TF is &amp;lt; 1%, sensitivity for ESR1mut is reduced and repeat testing should be considered. ESR1mut can coexist with complementary or competing resistance mechanisms, particularly when ESR1 is a minor allele, which could impact benefit from novel ET approved for patients with ESR1 mutations. Currently, CGP of LBx informs therapeutic recommendations for pts with HR+ MBC based on the binary presence or absence of ESR1mut; however, the clinical implications of the ESR1 mutation spectrum described herein and the potential impact of co-expression of other key pathway signals warrant further investigation. Citation Format: Heather McArthur, Hanna Tukachinsky, Alexa Schrock, Russell Madison, Oliver Holmes, Smruthy Sivakumar, Ethan Sokol, Ryon Graf, Julia Quintanilha, Kali Dougherty, Lincoln Pasquina, Geoffrey Oxnard, Mia Levy, Eric Winer. ESR1 genomic alterations (GAs) and coexistent putative resistance alterations in comprehensive genomic profiling (CGP) of metastatic breast cancer (MBC) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-16-03.

Abstract PO2-14-08: Development and characterization of breast cancer organoids representing epithelial heterogeneity and drug response

Abstract Organoids serve as an important preclinical model in multiple cancers including breast cancer, demonstrating preservation of biological features and feasibility of drug screening, with reasonable cost and high scalability. It has been reported that patient-derived organoids (PDOs) can be robustly derived from both primary and metastatic breast tumors, with high resemblance to source tissues in histological, genomic, and transcriptomic features, as well as consistency in drug response compared to xeno-transplantations or patients (Sachs et al, 2018). Since 2018, the Institute for Precision Medicine (IPM) has developed a panel of breast cancer organoids. The current inventory now consists of 128 PDOs from 94 primary tumors, 12 metastases, 12 rapid-autopsy tumors, and 10 normal breast tissues with a 60% success rate of culture; as well as 33 organoids from animal models including 11 patient-derived xenograft organoids (PDXOs), 15 rat (RDO) and 7 mouse (MDO) tumor organoids with 85% success rate. For PDOs, the protocol includes in-lab processing of fresh, deidentified tissue within 60 minutes of surgical operation, thanks to close collaboration with surgeons, consented patients, and an institutional biospecimen core. BC organoids have been comprehensively characterized in terms of morphology, histology, genomics, transcriptomics, and functional experiments. Key biological features are preserved. PDOs (n=56) exhibit a mutational spectrum consistent with human breast cancers. ER expression is detectable in a subset of cultures with robust estradiol response indicated by GREB1 expression; and PDOs from invasive lobular carcinoma (ILC) mostly showed more discohesive structures than PDOs from no special type (NST), with clear E-cadherin loss under immunofluorescence. We have also successfully constructed transcriptionally and genetic modified BC PDOs with shRNA and CRISPR, which showed replicable performance in proliferation assay, drug response, and signaling by western blot. Of note, longitudinal tracking of PDOs with single cell RNA-sequencing (scRNA-seq) revealed well-preserved heterogeneity compared to primary tumor, while transcriptomic clonality was mildly decreased in later passages from pilot data. Future work will include expansion of current collection from various sources, longitudinal characterization with scRNA-seq and DNA sequencing, as well as more functional studies. We aim to construct a robust resource of well-characterized and reliably-usable model bank for preclinical breast cancer research. Citation Format: Daniel Brown, Kai Ding, Fangyuan Chen, Jian Chen, Steffi Oesterreich, Peter Lucas, Priscilla McAuliffe, Jennifer Atkinson, ADRIAN LEE. Development and characterization of breast cancer organoids representing epithelial heterogeneity and drug response [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-14-08.

The full spectrum of SLC22 OCT1 mutations illuminates the bridge between drug transporter biophysics and pharmacogenomics

Mutations in transporters can impact an individual's response to drugs and cause many diseases. Few variants in transporters have been evaluated for their functional impact. Here, we combine saturation mutagenesis and multi-phenotypic screening to dissect the impact of 11,213 missense single-amino-acid deletions, and synonymous variants across the 554 residues of OCT1, a key liver xenobiotic transporter. By quantifying in parallel expression and substrate uptake, we find that most variants exert their primary effect on protein abundance, a phenotype not commonly measured alongside function. Using our mutagenesis results combined with structure prediction and molecular dynamic simulations, we develop accurate structure-function models of the entire transport cycle, providing biophysical characterization of all known and possible human OCT1 polymorphisms. This work provides a complete functional map of OCT1 variants along with a framework for integrating functional genomics, biophysical modeling, and human genetics to predict variant effects on disease and drug efficacy.