SLC26A4 Gene Research Articles

The role of SLC26A4 in bony labyrinth development and otoconial mineralization in mouse models.

Inner ear malformations are predominantly attributed to developmental arrest during the embryonic stage of membranous labyrinth development. Due to the inherent difficulty in clinically assessing the status of the membranous labyrinth, these malformations are diagnosed with radiographic imaging, based on the morphological characteristics of the bony labyrinth. While extensive research has elucidated the intricacies of membranous labyrinth development in mouse models, comprehensive investigations into the developmental trajectory of the bony labyrinth, especially about its calcification process, have been notably lacking. One of the most prominent types of inner ear malformations is known as incomplete partition (IP), characterized by nearly normal external cochlear appearance but pronounced irregularities in the morphology of the modiolus and inter-scalar septa. IP type II (IP-II), also known as Mondini dysplasia, is generally accompanied by an enlargement of the vestibular aqueduct and is primarily attributed to mutations in the SLC26A4 gene. In the case of IP-II, the modiolus and inter-scalar septa of the cochlear apex are underdeveloped or missing, resulting in the manifestation of a cystic structure on radiographic imaging. In this overview, we not only explore the normal development of the bony labyrinth in mice but also present our observations on otolith mineralization. Furthermore, we investigated the specifics of bony labyrinth and otolith mineralization in Slc26a4-deficient mice, which served as an animal model for IP-II. We ensured that these findings promise to provide valuable insights for the establishment of therapeutic interventions, optimal timing, targeted sites, and preventive measures when considering the management of this condition.

Unraveling the molecular landscape of kAE1: a narrative review.

Kidney anion exchanger 1 (kAE1) is an isoform of the AE1 protein encoded by the SLC4A1 gene. It is a basolateral membrane protein expressed by α-intercalated cells in the connecting tubules and collecting duct of the kidney. Its main function is to exchange bicarbonate and chloride ions between the blood and urine to maintain blood pH at physiological threshold. The kAE1 protein undergoes multiple post-translational modifications such as phosphorylation and ubiquitination and interacts with many different proteins such as claudin-4 and carbonic anhydrase II. Mutations in the gene may lead to the development of distal renal tubular acidosis, characterized by the failure to acidify the urine, which may result in nephrocalcinosis and in more severe cases, renal failure. In this review, we discuss the structure and function of kAE1, its post-translational modifications, and protein-protein interactions. Finally, we discuss insights gained from the study of kAE1 mutations in humans and in mice.

Phenotypic Variability Related to Mutations in Riboflavin Transporter in Brazilian Children: Pediatric Case Series

AbstractBrown–Vialetto–Van Laere syndrome or riboflavin transporter deficiency is a rare and genetically determined condition that results in a spectrum of neurological signs and symptoms from generalized muscle weakness to cranial nerve involvement with medullary symptoms and respiratory failure. Most patients have SLC52A3 gene biallelic variants, but some of them may have impairment of SLC52A2 gene, both related to the cell transport of riboflavin. We report the case of three unrelated Brazilian patients under 18 years of age with this diagnosis confirmed by molecular genetic sequencing. We observed that the clinical manifestations found were compatible with those already described in the literature by age group. Unusual findings of retinitis pigmentosa and immunodeficiency were identified related to pathogenic variants in the SLC52A2 gene. All patients received riboflavin replacement at a therapeutic dose without gastrointestinal intolerance and with clinical improvement after starting treatment.

Spatiotemporal expression of thyroid hormone transporter MCT8 and THRA mRNA in human cerebral organoids recapitulating first trimester cortex development

Thyroid hormones (TH) play critical roles during nervous system development and patients carrying coding variants of MCT8 (monocarboxylate transporter 8) or THRA (thyroid hormone receptor alpha) present a spectrum of neurological phenotypes resulting from perturbed local TH action during early brain development. Recently, human cerebral organoids (hCOs) emerged as powerful in vitro tools for disease modelling recapitulating key aspects of early human cortex development. To begin exploring prospects of this model for thyroid research, we performed a detailed characterization of the spatiotemporal expression of MCT8 and THRA in developing hCOs. Immunostaining showed MCT8 membrane expression in neuronal progenitor cell types including early neuroepithelial cells, radial glia cells (RGCs), intermediate progenitors and outer RGCs. In addition, we detected robust MCT8 protein expression in deep layer and upper layer neurons. Spatiotemporal SLC16A2 mRNA expression, detected by fluorescent in situ hybridization (FISH), was highly concordant with MCT8 protein expression across cortical cell layers. FISH detected THRA mRNA expression already in neuroepithelium before the onset of neurogenesis. THRA mRNA expression remained low in the ventricular zone, increased in the subventricular zone whereas strong THRA expression was observed in excitatory neurons. In combination with a robust up-regulation of known T3 response genes following T3 treatment, these observations show that hCOs provide a promising and experimentally tractable model to probe local TH action during human cortical neurogenesis and eventually to model the consequences of impaired TH function for early cortex development.

Improvement of neutropenia in 2 adolescent cases treated with empagliflozin for glycogen storage disease type Ib

Neutropenia and elevated concentrations of hepatic transaminases often lead to referrals from emergency or outpatient departments to relevant specialists to diagnose underlying inborn errors of metabolism. Glycogen storage disease type (GSD) Ib, a rare congenital disorder of glucose metabolism caused by the SLC37A4 gene mutations, shows various manifestations, including persistent neutropenia and elevated hepatic transaminases. Empagliflozin has demonstrated its efficacy in treating GSD Ib-associated neutropenia by reducing the entry of 1,5-anhydroglucitol-6-phosphate into the neutrophils. This article reports successful empagliflozin therapy for GSD Ib-related neutropenia in 2 Korean adolescents. Diagnosing GSD Ib is complex and usually initiated by a referral from emergency or outpatient departments when there is a high index of suspicion. Once diagnosed, empagliflozin shows promising outcomes in restoring counts and function of the neutrophils without severe adverse effects in children with GSD Ib, supporting it as a safe and effective therapeutic option for GSD Ib-associated neutropenia.

Clinical spectrum, over 12-year follow-up and experience of SGLT2 inhibitors treatment on patients with glycogen storage disease type Ib: a single-center retrospective study

BackgroundGlycogen storage disease type Ib (GSD Ib) is a rare disorder characterized by impaired glucose homeostasis caused by mutations in the SLC37A4 gene. It is a severe inherited metabolic disease associated with hypoglycemia, hyperlipidemia, lactic acidosis, hepatomegaly, and neutropenia. Traditional treatment consists of feeding raw cornstarch which can help to adjust energy metabolism but has no positive effect on neutropenia, which is fatal for these patients. Recently, the pathophysiologic mechanism of the neutrophil dysfunction and neutropenia in GSD Ib has been found, and the treatment with the SGLT2 inhibitor empaglifozin is now well established. In 2020, SGLT2 inhibitor empagliflozin started to be used as a promising efficient remover of 1,5AG6P in neutrophil of GSD Ib patients worldwide. However, it is necessary to consider long-term utility and safety of a novel treatment.ResultsIn this study, we retrospectively examined the clinical manifestations, biochemical examination results, genotypes, long-term outcomes and follow-up of thirty-five GSD Ib children who visited our department since 2009. Fourteen patients among them underwent empagliflozin treatment since 2020. This study is the largest cohort of pediatric GSD Ib patients in China as well as the largest cohort of pediatric GSD Ib patients treated with empagliflozin in a single center to date. The study also discussed the experience of long-term management on pediatric GSD Ib patients.ConclusionEmpagliflozin treatment for pediatric GSD Ib patients is efficient and safe. Increase of urine glucose is a signal for pharmaceutical effect, however attention to urinary infection and hypoglycemia is suggested.

Newborn screening, clinical features and genetic analysis for Citrin deficiency in Henan province

To explore the prevalence, clinical features, genetic characteristics and prognosis of Citrin deficiency in Henan province of China. A total of 986 565 neonates screened by tandem mass spectrometry at the Third Affiliated Hospital of Zhengzhou University from January 2013 to December 2021 were retrospectively analyzed. Analysis of SLC25A13 gene variants and parental verification were carried out for neonates suspected for Citrin deficiency by next-generation sequencing. The clinical, biochemical and genetic characteristics of Citrin deficiency patients were integrated to guide the diet treatment and follow up the growth and development. Paired-t test was used to compare the amino acid levels in the peripheral blood samples before and after the treatment. Nine cases of Citrin deficiency were diagnosed among the 986 565 neonates. Specific elevation of citrulline was observed in all of the 9 cases. Six variants were detected by genetic sequencing, among which c.852_855delTATG, c.615+5G>A, c.550C>T and IVS16ins3kb were known pathogenic variants, whilst c.1111_1112delAT and c.837T>A were unreported previously. The detection rate for c. 852_855delTATG was the highest (61.6%, 11/18), followed by IVS16ins3kb (16.7%, 3/18). The clinical symptoms of all patients were relieved after the treatment, and the blood amino acid profile and biochemical parameters were significantly improved by gradually falling within the normal range. By June 2022, all patients had shown a good prognosis. The prevalence of Citrin deficiency among neonates from Henan Province by tandem mass spectrometry is 1/109 618, and the carrier rate for the pathogenic variants of the SLC25A13 gene was 1/166. The c.852_855delTATG may be a hot spot variant among the patients. Discovery of the novel variants has enriched the mutational spectrum of the SLC25A13 gene. Above results have provided a basis for the early diagnosis, treatment, prognosis and genetic counseling for the affected families.

Clinical and genetic analysis of two pedigrees affected with Carnitine-acylcarnitine translocase deficiency due to variant of SLC25A20 gene

To analyze the clinical phenotype and genotypes of two children with Carnitine-acylcarnitine translocase deficiency (CACTD). Two children diagnosed with CACTD at the Gansu Provincial Maternal and Child Health Care Hospital respectively on January 3 and November 19, 2018 were selected as the study subjects. Trio-whole exome sequencing (trio-WES) was carried out, and candidate variants were validated through Sanger sequencing and pathogenicity analysis. Both children were males and had manifested mainly with hypoglycemia. Trio-WES and Sanger sequencing showed that child 1 had harbored compound heterozygous variants of the SLC25A20 gene, namely c.49G>C (p.Gly17Arg) and c.106-2A>G, which were inherited from his father and mother, respectively. Child 2 had harbored homozygous c.199-10T>G variants of the SLC25A20 gene, which were inherited from both of his parents. Among these, the c.106-2A>G and c.49G>C variants were unreported previously. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the c.49G>C (p.Gly17Arg), c.106-2A>G, and c.199-10T>G variants were classified as likely pathogenic (PM2_supporting+PP3+PM3_strong+PP4), pathogenic (PVS1+PM2_supporting+PM5+PP3), and pathogenic (PVS1+PM2_supporting+PP3+PP5), respectively. Combined with their clinical phenotype and genetic analysis, both children were diagnosed with CACTD. Above finding has provided a basis for their treatment as well as genetic counseling and prenatal diagnosis for their families.

Sodium-glucose cotransporter 2 inhibitors, inflammation, and heart failure: a two-sample Mendelian randomization study

BackgroundSodium-glucose cotransporter 2 (SGLT-2) inhibitors are increasingly recognized for their role in reducing the risk and improving the prognosis of heart failure (HF). However, the precise mechanisms involved remain to be fully delineated. Evidence points to their potential anti-inflammatory pathway in mitigating the risk of HF.MethodsA two-sample, two-step Mendelian Randomization (MR) approach was employed to assess the correlation between SGLT-2 inhibition and HF, along with the mediating effects of inflammatory biomarkers in this relationship. MR is an analytical methodology that leverages single nucleotide polymorphisms as instrumental variables to infer potential causal inferences between exposures and outcomes within observational data frameworks. Genetic variants correlated with the expression of the SLC5A2 gene and glycated hemoglobin levels (HbA1c) were selected using datasets from the Genotype-Tissue Expression project and the eQTLGen consortium. The Genome-wide association study (GWAS) data for 92 inflammatory biomarkers were obtained from two datasets, which included 14,824 and 575,531 individuals of European ancestry, respectively. GWAS data for HF was derived from a meta-analysis that combined 26 cohorts, including 47,309 HF cases and 930,014 controls. Odds ratios (ORs) and 95% confidence interval (CI) for HF were calculated per 1 unit change of HbA1c.ResultsGenetically predicted SGLT-2 inhibition was associated with a reduced risk of HF (OR 0.42 [95% CI 0.30–0.59], P < 0.0001). Of the 92 inflammatory biomarkers studied, two inflammatory biomarkers (C-X-C motif chemokine ligand 10 [CXCL10] and leukemia inhibitory factor) were associated with both SGLT-2 inhibition and HF. Multivariable MR analysis revealed that CXCL10 was the primary inflammatory cytokine related to HF (MIP = 0.861, MACE = 0.224, FDR-adjusted P = 0.0844). The effect of SGLT-2 inhibition on HF was mediated by CXCL10 by 17.85% of the total effect (95% CI [3.03%–32.68%], P = 0.0183).ConclusionsThis study provides genetic evidence supporting the anti-inflammatory effects of SGLT-2 inhibitors and their beneficial impact in reducing the risk of HF. CXCL10 emerged as a potential mediator, offering a novel intervention pathway for HF treatment.Graphical

Mutation spectrum analysis of 23-site chip neonatal deafness genetic screening

Objective:To analyze the mutation spectrum of 23-site chip newborn deafness genetic screening in Beijing, and to provide basis for genetic counseling and clinical diagnosis and treatment. Methods:The study included 21 006 babies born in Beijing from December 2022 to June 2023. All subjects underwent newborn deafness genetic screening in Beijing Tongren Hospital, covering 23 variants in 4 genes, the GJB2 gene（c.35delG, c.176_191del16, c.235delC, c.299_300delAT, c.109G>A, c.257C>G, c.512insAACG, c.427C>T, c.35insG）, SLC26A4 gene（c.919-2A>G, c.2168A>G, c.1174A>T, c.1226G>A, c.1229C>T, c.1975G>C, c.2027T>A, c.589G>A, c.1707+5G>A, c.917insG, c.281C>T）, Mt12SrRNA（m.1555A>G, m.1494C>T） and GJB3 gene（c.538C>T）. The mutation detection rate and allele frequency were analyzed. Results:The overall mutation detection rate was 11.516%（2 419/21 006）, with the GJB2 gene being the most frequently involved at 9.097%（1 911/21 006）, followed by the SLC26A4 gene at 2.123%（446/21 006）, the GJB3 gene at 0.362%（76/21 006） and Mt12SrRNA at 0.176%（37/21 006）. Among the GJB2 genes, c.109G>A and c.235delC mutation detection rates were the highest, with 6.579%（1 382/21 006） and 1.795%（377/21 006）, respectively. Of the SLC26A4 genes, c.919-2A>G and c.2168A>G had the highest mutation rates of 1.423%（299/21 006） and 0.233%（49/21 106）, respectively. Regarding the allele frequency, GJB2 c.109G>A was the most common variant with an allele frequency of 3.359%（1 411/42 012）, followed by the GJB2 c.235delC at 0.897%（377/42 012） and the SLC26A4 c.919-2A>G at 0.719%（302/42 012）. Conclusion:23-site chip newborn deafness genetic screening in Beijing showed that GJB2 c.109G>A mutation detection rate and allele frequency were the highest. This study has enriched the epidemiological data of 23-site chip genetic screening mutation profiles for neonatal deafness, which can provide evidence for clinical practice.

Mutational Analysis of the SLC4A11 Gene in a (Filipino) Family with Congenital Hereditary Endothelial Dystrophy

Aim: The study aims to identify if mutations in the SLC4A11 gene are present in Filipino families affected with congenital hereditary endothelial dystrophy (CHED). Methods: This is a family cohort study that investigated the genetic profile of a selected family in northern Luzon, Philippines, whose members were diagnosed with congenital hereditary endothelial dystrophy (CHED). A patient who was diagnosed with CHED prior to this study served as the proband for this family. A detailed family history was obtained and a complete ophthalmologic examination was performed on each of the family members. A total of six affected members and three unaffected members were included in this study. DNA was isolated from peripheral blood samples of the family members, polymerase chain reaction (PCR) was used to amplify the gene’s entire coding region (19 exons and 2 putative promoter regions), and finally, the amplified regions were analyzed using DNA sequencing. Results: Consanguinity was not present in the family. Corneal haze was reported to have been present since birth or shortly thereafter in all the affected patients. Slit-lamp examination showed edematous corneas. Molecular studies of the SLC4A11 gene revealed four novel homozygous point mutations variably presenting in the six affected members, as well as the three unaffected members. One unaffected family member (I-1) had a novel sense mutation absent in the other family members. All affected siblings showed little phenotypic variability. Conclusions: This is the first report that gives us a genetic profile of a northern Luzon family with members affected by CHED. This study supports earlier findings that mutations in the SLC4A11 gene are not consistently the same among different ethnic groups worldwide, probably due to the disease’s genetic heterogeneity. Our study documented five novel mutations, adding to the growing list of mutations probably responsible for acquiring the CHED phenotype. It is possible that there are more novel mutations waiting to be discovered in this hereditary disease. Screening for these specific mutations in other families may prove useful for genetic counseling, prenatal diagnosis, and the future development of gene therapy.

The effect of preanalytical phase on the stability of the osmotic fragility and morphological changes in erythrocytes in cattle (Bos taurus)

Hereditary spherocytosis in cattle is a disorder that results from a nonsense mutation in SLC4A1 gene that encodes band 3 membrane protein. This membranopathy leads to a production of spherically-shaped RBCs with reduced deformability and shorter lifespan in circulation. The laboratory diagnosis of hereditary spherocytosis commonly rely on erytrocyte osmotic fragility test (OFT), which is time and work consuming and can be influenced by the preanalytical factors. The aim of the study was to determine the effect of the preanalytical phase on the stability of the osmotic fragility and morphological changes of bovine erythrocytes. The blood was collected from the tail vein from Holstein-Friesian cows (n = 20) into tubes with EDTA or lithium heparin. The erythrocyte resistance to hemolysis was measured by osmotic fragility test immediately after blood collection and 24, 48 and 72 hours after storage at 4oC or room temperature. The thin blood smears were also prepared, stained and examined for cell morphology.The results showed that bovine erythrocyte osmotic fragility remains stable during 24 hours storage at 4oC regardless of the anticoagulant used. It suggests the possibility of performing OFT the day after blood collection when storing blood at 4oC. It was also found that bovine erythrocytes stored at room temperature have reduced osmotic resistance. However, heparin better preserves osmotic resistance of bovine erythrocytes at room temperature. Erythrocytes that are stored undergo changes during the storage period. The microscopic examination of cell morphology revealed the transformation of bovine discocytes into different stages of echinocytes, which rapidly occurs during the first three days of storage.

Abstract 5684: The role of the lncRNA Slamon and Slc25a13 neighbor gene in melanoma aggressiveness

Abstract Melanomas are responsible for about 80% of all deaths related to skin cancers. This is due to its high potential of metastasizing and developing resistance to treatments. Novel therapeutic modalities and the identification of biomarkers able to predict the prognosis are necessary. Studies have revealed the central role of long non-coding RNAs (lncRNAs) in regulatory networks controlling cell behavior. The disruption of these regulatory networks as a consequence of altered expression of lncRNAs can contribute to cancer development and progression. Our laboratory has developed a linear cellular model of melanoma progression consisting of distinct cell lines: melan-a (melanocytes), 4C (pre-malignant melanocytes), 4C11- (undifferentiated, slow-growing and non-metastatic melanoma cells) and 4C11+ (differentiated, highly proliferative and metastatic melanoma cells), which were analyzed for their lncRNA expression profile. Differentially expressed lncRNAs identified by RNAseq were selected by in silico analyses based on their proximity to differentially expressed coding-genes in the same melanoma model. Correlation analyses were performed between the expression of differentially expressed lncRNA neighboring genes and their melanoma patient survival, using two independent melanoma cohorts (TCGA and Leeds). Among those lncRNA located near genes presenting prognostic value is the lncRNA Gm20619, here named Slamon, neighbor to Slc25a13 gene (mitochondrial aspartate/glutamate carrier gene), which high expression correlates with poor prognosis. Both Slamon lncRNA and Slc25a13 are highly expressed in the metastatic melanoma cells 4C11+ compared to melan-a, 4C and 4C11- cell lines. The knocking down of Slamon or Slc25a13 were performed in 4C11+ melanoma cells, followed by analyses of collective migration, clonogenicity, proliferation, anoikis resistance, and dacarbazine and MEK inhibitor treatment. By knocking down Slamon lead 4C11+ cells significantly less migratory and less resistant to dacarbazine, and resulted in increased expression of Slc25a13 gene. 4C11+ melanoma cells knocked down for Slc25a13 also presented reduced migratory, clonogenicity, proliferation and anoikis resistance capability, diminished sensitivity to dacarbazine and MEK inhibitor treatment, and increased expression of Slamon lncRNA. The analysis of genes coexpressed with Slc25a13 revealed genes related to tumor progression, as Cdk15, Lsp1 and Pdgfrb. Our results suggest a crucial role of the lncRNA Slamon and Slc25a13 coding gene in melanoma progression which has never been described before. Slamon regulates tumor aggressiveness associated with Slc25a13, forming a regulatory network. These findings reveal the importance of lncRNAs in melanoma biology, potentially indicating transcripts that can serve as prognostic biomarkers and therapeutic targets in melanoma. Citation Format: Beatriz C. Tonin, Ana L. Ayub, André H. Lengert, Sang W. Han, Eduardo M. Reis, Frank J. Slack, Miriam G. Jasiulionis. The role of the lncRNA Slamon and Slc25a13 neighbor gene in melanoma aggressiveness [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5684.

Abstract 1894: Preclinical development of YL205, a novel NaPi2b-targeting antibody-drug conjugate (ADC) with novel topoisomerase I inhibitor-based linker-payload for treatment of solid tumors

Abstract MediLink’s TMALIN (Tumor Microenvironment Activable LINker-payload) platform incorporates the proprietary protease-cleavable tripeptide linker and novel DNA topoisomerase I inhibitor, enables the release payload both in the tumor cell intracellularly and in the tumor microenvironment extracellularly. YL205 is built on the TMALIN platform, which is comprised of an anti-NaPi2b humanized monoclonal antibody and conjugated in a site-specific manner to yield a uniform DAR 8 product. NaPi2b, encoded by the SLC34A2 gene, is a cell surface sodium-dependent phosphate transporter that is highly expressed in certain cancers, including ovarian, lung, thyroid, and breast cancers, with limited expression in normal tissues. This study evaluated the drug properties, efficacy, safety and pharmacokinetic profiles of YL205 in nonclinical studies. YL205 achieved a high drug-to-antibody ratio through homogeneous conjugation with hydrophilic TMALIN linker-payload, which showed limited impact on the hydrophilicity of the antibody, prolonged the retention time in vivo and eventually enhanced the in vivo potency of ADC. Additionally, YL205 exhibited strong potency, high internalization, potent cytotoxicity and bystander-mediated cell killing toward tumor cells. Significant dose-dependent antitumor activities, including complete tumor regressions with no observable toxicity, were noted in NaPi2b low to high expression ovarian and NSCLC tumor xenograft mouse models. YL205 showed a favorable PK profile evidenced by the overlapping ADC and TAb curves in SD rat and cynomolgus monkey studies. Despite high levels of expression in normal lungs of non-human primates, YL205 exhibited a good safety profile with toxic findings unrelated to normal tissue target expression. Toxicity studies using cynomolgus monkeys showed that YL205 is well tolerated with calculated therapeutic index (TI, HNSTD versus MED) of ﹥80 for repeat dosing. No drug-related adverse findings were found in the lungs, liver or kidneys when tested in all doses. The highly stable nature of TMALIN linker, together with the high potency of the payload, likely mitigates the potential liability of this normal tissue expression. Based on these results, it demonstrates that YL205’s advanced ADC design results in an increased therapeutic margin, and YL205 may help address unmet medical need in patients with NaPi2b-expressing tumors. Citation Format: Liang Xiao, Wei Lian, Qigang Liu, Qing Zong, Shuai Song, Sasha Stann, Jiaqiang Cai, Tongtong Xue. Preclinical development of YL205, a novel NaPi2b-targeting antibody-drug conjugate (ADC) with novel topoisomerase I inhibitor-based linker-payload for treatment of solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1894.

Abstract 5085: Preclinical development of NaPi2b-PL2202, a novel camptothecin-based antibody-drug conjugate targeting solid tumors expressing NaPi2b

Abstract NaPi2b, encoded by the SLC34A2 gene, is a multi-transmembrane, sodium-dependent phosphate transporter expressed at high levels in tumors and low levels in normal tissues. Functionally, it is involved in trans-cellular flux of phosphate in the small intestine and in the synthesis of surfactant in lung alveoli. NaPi2b is reported to be expressed at a high frequency in ovarian carcinoma as well as in NSCLC, bladder, endometrial and papillary thyroid carcinoma1, and its expression is associated with poor prognosis 2, 3. The purpose of this study was to characterize the in vitro and in vivo anti-tumor activity and tolerability of NaPi2b-PL2202, an antibody-drug conjugate (ADC) composed of a humanized, Fc-silenced IgG1 antibody directed against human NaPi2b, to which PL2202, a novel payload containing a valine-alanine cleavable linker and a camptothecin warhead, has been site-specifically conjugated with a drug to antibody ratio of 6. In addition, the level of NaPi2b expression in selected human tumor specimens was evaluated by immunohistochemistry (IHC). In vitro, NaPi2b-PL2202 showed good binding affinity for mouse, rat, cynomolgus monkey and human NaPi2b, and displayed highly potent, targeted cytotoxicity against various NaPi2b-expressing tumor cell lines. NaPi2b-PL2202 also exhibited strong in vitro bystander activity. In vivo, intravenous (IV) administration of a single dose of NaPi2b-PL2202 at 6.6 mg/kg resulted in substantial tumor regression in the OVCAR-3 ovarian carcinoma xenograft model, with 3/10 partial responders (PR) and 7/10 complete responders (CR), and all CRs being tumor-free at the end of the study (Day 44). In the G-402 renal leiomyoblastoma xenograft model, administration of a single IV dose of NaPi2b-PL2202 at 3.3 mg/kg was associated with durable antitumor activity and resulted in 1/10 CR, with this animal remaining tumor-free by the end of the study (Day 42). With respect to toxicity, in single dose studies in male rats, NaPi2b-PL2202 was tolerated up to 300 mg/kg IV. Furthermore, in a dose-range finding study in male cynomolgus monkeys, NaPi2b-PL2202 was well tolerated up to 40 mg/kg IV given on Day 1 and 22. Finally, cell membranous NaPi2b expression was confirmed by IHC in a panel of tissue microarrays including ovarian, lung, bladder and endometrial cancers. In conclusion, NaPi2b-PL2202 demonstrated specific and potent in vitro and in vivo anti-tumor activity, and was tolerated at high doses in toxicity studies in rats and cynomolgus monkeys, indicating a good therapeutic index. Together, these observations support future clinical development of NaPi2b-PL2202 for the treatment of NaPi2b-expressing cancers. 1- Bodyak N. D. et al., 2021 2- Valsenkova R. et al., 2021 3- Hakim S. A. et al., 2021 Citation Format: Elizabeth Horsley, Asma Jabeen, Nicolas Veillard, Karin Havenith, Narinder Janghra, Pedro Alves, Cecile Oblette, Ian Kirby, Paul W. Hogg, Francesca Zammarchi, Lolke de Haan, Patrick van Berkel. Preclinical development of NaPi2b-PL2202, a novel camptothecin-based antibody-drug conjugate targeting solid tumors expressing NaPi2b [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5085.

Biallelic and monoallelic pathogenic variants in CYP24A1 and SLC34A1 genes cause idiopathic infantile hypercalcemia

ObjectiveIdiopathic infantile hypercalcemia (IIH) is a rare disorder of PTH-independent hypercalcemia. CYP24A1 and SLC34A1 gene mutations cause two forms of hereditary IIH. In this study, the clinical manifestations and molecular aspects of six new Chinese patients were investigated.MethodsThe clinical manifestations and laboratory study of six patients with idiopathic infantile hypercalcemia were analyzed retrospectively.ResultsFive of the patients were diagnosed with hypercalcemia, hypercalciuria, and bilateral medullary nephrocalcinosis. Their clinical symptoms and biochemical abnormalities improved after treatment. One patient presented at age 11 years old with arterial hypertension, hypercalciuria and nephrocalcinosis, but normal serum calcium. Gene analysis showed that two patients had compound heterozygous mutations of CYP24A1, one patient had a monoallelic CYP24A1 variant, and three patients had a monoallelic SLC34A1 variant. Four novel CYP24A1 variants (c.116G > C, c.287T > A, c.476G > A and c.1349T > C) and three novel SLC34A1 variants (c.1322 A > G, c.1697_1698insT and c.1726T > C) were found in these patients.ConclusionsA monoallelic variant of CYP24A1 or SLC34A1 gene contributes to symptomatic hypercalcemia, hypercalciuria and nephrocalcinosis. Manifestations of IIH vary with onset age. Hypercalcemia may not necessarily present after infancy and IIH should be considered in patients with nephrolithiasis either in older children or adults.

Glycerol Phenylbutyrate Treatment of 2 Patients With Monocarboxylate Transporter 8 Deficiency.

Monocarboxylate transporter 8 (MCT8) deficiency is a rare genetic disease that leads to severe global developmental delay. MCT8 facilitates thyroid hormone (TH) transport across the cell membrane, and the serum TH profile is characterized by high T3 and low T4 levels. Recent studies have shown that the chemical chaperone sodium phenylbutyrate (NaPB) restored mutant MCT8 function and increased TH content in patient-derived induced pluripotent stem cells, making it a potential treatment for MCT8 deficiency. We aimed to assess the efficacy and safety of glycerol phenylbutyrate (GPB) in MCT8 deficiency. We treated 2 monozygotic twins aged 14.5 years with MCT8 deficiency due to P321L mutation with escalating doses of GPB over 13 months. We recorded TH, vital signs, anthropometric measurements, and neurocognitive functions. Resting metabolic rate (RMR) was measured by indirect calorimetry. Serum metabolites of GPB were monitored as a safety measure. In vitro effects of NaPB were evaluated in MDCK1 cells stably expressing the MCT8P321L mutation. The effects of GPB were compared to the effects of DITPA and TRIAC, thyromimetic medications that the patients had received in the past. NaPB restored mutant MCT8 expression in MDCK1 cells and increased T3 transport into cells carrying the P321L mutation. GPB treatment reduced high T3 and increased low T4 levels. The patients showed a significant weight gain simultaneously with a reduction in RMR. Only minor neurocognitive improvement was observed, in hyperreflexia score and in cognitive functions. Serum metabolites did not exceed the toxic range, but elevated liver transaminases were observed. In the first report of GPB treatment in MCT8 deficiency we found an improvement in TH profile and body mass index, with minor neurodevelopmental changes.

Importance about use of high-throughput sequencing in pediatric: case report of a patient with Fanconi-Bickel syndrome

BackgroundFanconi-Bickel syndrome is characterized by hepatorenal disease caused by anomalous glycogen storage. It occurs due to variants in the SLC2A2 gene. We present a male patient of 2 years 7 months old, with failure to thrive, hepatomegaly, metabolic acidosis, hypophosphatemia, hypokalemia, hyperlactatemia.ResultsExome sequencing identified the homozygous pathogenic variant NM_000340.2(SLC2A2):c.1093 C > T (p.Arg365Ter), related with Fanconi-Bickel syndrome. He received treatment with bicarbonate, amlodipine, sodium citrate and citric acid solution, enalapril, alendronate and zolendronate, and nutritional management with uncooked cornstarch, resulting in an improvement of one standard deviation in weight and height.ConclusionsThe importance of knowing the etiology in rare genetic disease is essential, not only to determine individual and familial recurrence risk, but also to establish the treatment and prognosis; in this sense, access to a new genomic technology in low- and middle-income countries is essential to shorten the diagnostic odyssey.

Identification of novel mutations in TPK1 and SLC19A3 genes in families exhibiting thiamine metabolism dysfunction syndrome

Background and aimsThe occurrence of thiamine metabolism dysfunction syndrome (THMD), a rare autosomal recessive condition, may be linked to various mutations found in the TPK1 and SLC19A3 genes. The disease chiefly manifests through ataxia, muscle hypotonia, abrupt or subacute onset encephalopathy, and a decline in developmental milestones achieved during the early stages of infancy. We present findings from an investigation that involved two individuals from Iran, both of whom experienced seizures along with ataxia and hypotonia. The underlying genetic causes were found with the use of next-generation sequencing (NGS) technology, which has facilitated the detection of causal changes in a variety of genetic disorders. Material and methodsThe selection of cases for this study was based on the phenotypic and genetic information that was obtainable from the Center for Comprehensive Genetic Services. The genetic basis for the problems observed among the participants was determined through the application of whole-exome sequencing (WES). Subsequently, sanger sequencing was employed as a means of validating any identified variations suspected to be causative. ResultsThe first patient exhibited a homozygous mutation in the TPK1 gene, NM_022445.4:c.224 T > A:p.I75 N, resulting in the substitution of isoleucine for asparagine at position 75 (p.I75 N). In our investigation, patient 2 exhibited a homozygous variant, NM_025243.4:c.1385dupA:pY462X, within the SLC19A3 gene. ConclusionsCollectively, when presented with patients showcasing ataxia, encephalopathy, and basal ganglia necrosis, it is essential to account for thiamine deficiency in light of the potential advantages of prompt intervention. At times, it may be feasible to rectify this deficiency through the timely administration of thiamine dosages. Accordingly, based on the results of the current investigation, these variations may be useful for the diagnosis and management of patients with THMD.

Clinical, biochemical, and genotypical characteristics in urea cycle mitochondrial transporter disorders.

This study aimed to evaluate clinical, biochemical, and genotypic findings of patients diagnosed with urea cycle mitochondrial transporter disorders. In this study, patients followed up with the diagnosis of urea cycle mitochondrial transporter disorders in the pediatric metabolism outpatient clinic of Diyarbakir Children's Hospital were retrospectively examined. Height, weight, head circumference, gender, age at diagnosis, follow-up period, consanguinity history between parents, and treatments of the patients included in the study were evaluated. Eight patients suffering from urea cycle mitochondrial transporter disorders were enrolled in the study. Five patients were found to have biallelic variants of the SLC25A15 gene. Two patients were found to have biallelic variants of the SLC25A13 gene. Two of our patients presented with gait disturbances and were diagnosed with HHH syndrome. One patient presented with liver failure and was diagnosed with HHH syndrome. The other three patients were identified by family screening. Citrin deficiency was detected in two patients with cholestasis and hepatomegaly in the infantile period. Ornithine levels increased in three of our patients with HHH syndrome during the first month of treatment despite a protein-restricted diet and adequate caloric intake. Increasing patients' caloric intake with HHH syndrome improves their ornithine levels. Our patients with citrin deficiency recovered clinically and biochemically before seven months.