High risk of lung cancer in surfactant-related gene variant carriers.

BACKGROUND: Several rare surfactant-related gene (SRG) variants associated with interstitial lung disease are suspected to be associated with lung cancer, but data are missing. We aimed to study the epidemiology and phenotype of lung cancer in an international cohort of SRG variant carriers. METHODS: We conducted a cross-sectional study of all adults with SRG variants in the OrphaLung network and compared lung cancer risk with telomere-related gene (TRG) variant carriers. RESULTS: We identified 99 SRG adult variant carriers (SFTPA1 (n=18), SFTPA2 (n=31), SFTPC (n=24), ABCA3 (n=14) and NKX2-1 (n=12)), including 20 (20.2%) with lung cancer (SFTPA1 (n=7), SFTPA2 (n=8), SFTPC (n=3), NKX2-1 (n=2) and ABCA3 (n=0)). Among SRG variant carriers, the odds of lung cancer was associated with age (OR 1.04, 95% CI 1.01-1.08), smoking (OR 20.7, 95% CI 6.60-76.2) and SFTPA1/SFTPA2 variants (OR 3.97, 95% CI 1.39-13.2). Adenocarcinoma was the only histological type reported, with programmed death ligand-1 expression ≥1% in tumour cells in three samples. Cancer staging was localised (I/II) in eight (40%) individuals, locally advanced (III) in two (10%) and metastatic (IV) in 10 (50%). We found no somatic variant eligible for targeted therapy. Seven cancers were surgically removed, 10 received systemic therapy, and three received the best supportive care according to their stage and performance status. The median overall survival was 24 months, with stage I/II cancers showing better survival. We identified 233 TRG variant carriers. The comparative risk (subdistribution hazard ratio) for lung cancer in SRG patients versus TRG patients was 18.1 (95% CI 7.1-44.7). CONCLUSIONS: The high risk of lung cancer among SRG variant carriers suggests specific screening and diagnostic and therapeutic challenges. The benefit of regular computed tomography scan follow-up should be evaluated.

Association analysis of the surfactant protein-C gene to childhood asthma.

OBJECTIVES: This study aims to describe the molecular variability in the SFTPC gene in a childhood chronic respiratory disease, asthma, in the Tunisian population and to identify the implications based on a case-control study of p.Thr138Asn (T138N) and p.Ser186Asn (S186N) variants. METHODS: We used direct sequencing for the genotyping of the SFTPC gene within 101 asthmatic children. The study of T138N and S186N variants in 110 controls is conducted by the PCR-RFLP technique. RESULTS: The molecular study revealed 26 variants including 24 intronic variations and 2 exonic variations (T138N and S186N) with respective frequencies of 16.8% and 18.3%. We conducted a case-control study of the two identified exonic variations. A different genotypic and allelic distribution between the two groups was noted. Only the T138N polymorphism showed a significant association with asthma disease (p < 1 0 -3). Statistical analysis elaborated four haplotypes with the following frequencies in patients vs controls: 138Thr-186Ser (79.5% vs 57.6%), 138Thr-186Asn (3.7% vs 7.8%), 138Asn-186Thr (2.2% vs 20.2%) and 138Asn-186Asn (14.6% vs 14.4%). A significant difference (p < 1 0 -3) was highlighted in haplotype distribution. The 138Asn-186Ser (OR [95%CI] = 0.14[0.04-0.54], p = 0.004, R2=0.93) and 138Thr-186Asn (OR [95%CI] = 0.35[0.12-0.54], p = 0.047, R2=0.88) haplotypes showed a negative association with asthma which may constitute a protective factor against the disease. CONCLUSION: In Tunisia, this work constitutes the first report interested in the SFTPC gene and highlights the genetic variability of the SFTPC gene in asthma. Therefore, the case-controls analysis may be useful in the study of surfactant proteins dysfunction in chronic respiratory disease at an early age.

Methylprednisolone pulse treatment improves ProSP-C trafficking in twins with SFTPC mutation: An isoform story?

Mutations in the gene encoding surfactant protein C (SP-C) cause interstitial lung disease (ILD), and glucocorticosteroid (GC) treatment is the most recognized therapy in children. We aimed to decipher the mechanisms behind successful GC treatment in twins carrying a BRICHOS c.566G > A (p.Cys189Tyr) mutation in the SP-C gene (SFTPC). METHODS: The twins underwent bronchoscopy before and after GC treatment and immunoblotting analysis of SP-C proprotein (proSP-C) and SP-C mature in bronchoalveolar fluid (BALF). Total RNA was extracted and analysed using quantitative real-time PCR assays. In A549 cells, the processing of mutated protein C189Y was studied by immunofluorescence and immunoblotting after heterologous expression of eukaryotic vectors containing wild type or C189Y mutant cDNA. RESULTS: Before treatment, BALF analysis identified an alteration of the proSP-C maturation process. Functional study of C189Y mutation in alveolar A549 cells showed that pro-SP-CC189Y was retained within the endoplasmic reticulum together with ABCA3. After 5 months of GC treatment with clinical benefit, the BALF analysis showed an improvement of proSP-C processing. SFTPC mRNA analysis in twins revealed a decrease in the expression of total SFTPC mRNA and a change in its splicing, leading to the expression of a second shorter proSP-C isoform. In A549 cells, the processing and the stability of this shorter wild-type proSP-C isoform was similar to that of the longer isoform, but the half-life of the mutated shorter isoform was decreased. These results suggest a direct effect of GC on proSP-C metabolism through reducing the SFTPC mRNA level and favouring the expression of a less stable protein isoform.

Structure-Based Understanding of ABCA3 Variants.

ABCA3 is a crucial protein of pulmonary surfactant biosynthesis, associated with recessive pulmonary disorders such as neonatal respiratory distress and interstitial lung disease. Mutations are mostly private, and accurate interpretation of variants is mandatory for genetic counseling and patient care. We used 3D structure information to complete the set of available bioinformatics tools dedicated to medical decision. Using the experimental structure of human ABCA4, we modeled at atomic resolution the human ABCA3 3D structure including transmembrane domains (TMDs), nucleotide-binding domains (NBDs), and regulatory domains (RDs) in an ATP-bound conformation. We focused and mapped known pathogenic missense variants on this model. We pinpointed amino-acids within the NBDs, the RDs and within the interfaces between the NBDs and TMDs intracellular helices (IHs), which are predicted to play key roles in the structure and/or the function of the ABCA3 transporter. This theoretical study also highlighted the possible impact of ABCA3 variants in the cytosolic part of the protein, such as the well-known p.Glu292Val and p.Arg288Lys variants.

Small Hsps as Therapeutic Targets of Cystic Fibrosis Transmembrane Conductance Regulator Protein.

Human small heat shock proteins are molecular chaperones that regulate fundamental cellular processes in normal and pathological cells. Here, we have reviewed the role played by HspB1, HspB4 and HspB5 in the context of Cystic Fibrosis (CF), a severe monogenic autosomal recessive disease linked to mutations in Cystic Fibrosis Transmembrane conductance Regulator protein (CFTR) some of which trigger its misfolding and rapid degradation, particularly the most frequent one, F508del-CFTR. While HspB1 and HspB4 favor the degradation of CFTR mutants, HspB5 and particularly one of its phosphorylated forms positively enhance the transport at the plasma membrane, stability and function of the CFTR mutant. Moreover, HspB5 molecules stimulate the cellular efficiency of currently used CF therapeutic molecules. Different strategies are suggested to modulate the level of expression or the activity of these small heat shock proteins in view of potential in vivo therapeutic approaches. We then conclude with other small heat shock proteins that should be tested or further studied to improve our knowledge of CFTR processing.

Extracardiac soft tissue uptake, evidenced on early 99mTc-HMDP SPECT/CT, helps typing cardiac amyloidosis and demonstrates high prognostic value.

PURPOSE: Increased cardiac uptake (CU) on early-phase 99mTc-HMDP scintigraphy has demonstrated diagnostic and prognostic values in amyloid transthyretin (ATTR) cardiac amyloidosis (CA). Extracardiac uptake (ECU) has been poorly studied. We assessed the clinical value of ECU, in combination with CU, on 99mTc-HMDP scintigraphy using a novel Methodological Amyloidosis Diagnostic Index (MADI). METHODS: We reviewed all patients referred for suspicion of CA, who underwent 99mTc-HMDP scintigraphy over an 8-year period. ECU, CU, and MADI were determined: MADI0 = neither ECU or CU, MADI1 = ECU alone, MADI2 = CU alone, and MADI3 = ECU + CU. RESULTS: Of 308 eligible patients, 247 had CA, including 75 ATTRv, 107 ATTRwt, and 65 light-chain (AL), while 61 had another cardiopathy (controls). ECU was observed in 29% of CA and 3% of controls. Most frequent sites of ECU were pleuropulmonary (16% of CA, 3% of controls) followed by the digestive tract and subcutaneous tissues. The liver and spleen ECU was only observed in AL-CA (n = 8). CU was only observed in CA patients (n = 187), of whom 182 had ATTR-CA vs. 5 AL-CA, P < 0.001. MADI0 was only observed in controls (97%) and in AL-CA (60%). MADI1 was mainly observed in AL-CA (positive predictive value, PPV = 91%) while MADI2/3 were more frequent in ATTR-CA (PPV = 97%), P < 0.0001. MADI > 0 vs. MADI0 in AL and MADI3 vs. MADI2 in ATTR were associated with a worse prognosis (P = 0.03 and P = 0.002, respectively). CONCLUSIONS: ECU combined with CU demonstrates high diagnostic and prognostic values in CA patients. MADI seems an easy and reliable score in clinical practice.

Phosphorylation of the Chaperone-Like HspB5 Rescues Trafficking and Function of F508del-CFTR.

Cystic Fibrosis is a lethal monogenic autosomal recessive disease linked to mutations in Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein. The most frequent mutation is the deletion of phenylalanine at position 508 of the protein. This F508del-CFTR mutation leads to misfolded protein that is detected by the quality control machinery within the endoplasmic reticulum and targeted for destruction by the proteasome. Modulating quality control proteins as molecular chaperones is a promising strategy for attenuating the degradation and stabilizing the mutant CFTR at the plasma membrane. Among the molecular chaperones, the small heat shock protein HspB1 and HspB4 were shown to promote degradation of F508del-CFTR. Here, we investigated the impact of HspB5 expression and phosphorylation on transport to the plasma membrane, function and stability of F508del-CFTR. We show that a phosphomimetic form of HspB5 increases the transport to the plasma membrane, function and stability of F508del-CFTR. These activities are further enhanced in presence of therapeutic drugs currently used for the treatment of cystic fibrosis (VX-770/Ivacaftor, VX-770+VX-809/Orkambi). Overall, this study highlights the beneficial effects of a phosphorylated form of HspB5 on F508del-CFTR rescue and its therapeutic potential in cystic fibrosis.

Cis variants identified in F508del complex alleles modulate CFTR channel rescue by small molecules.

Molecules correcting the trafficking (correctors) and gating defects (potentiators) of the cystic fibrosis causing mutation c.1521_1523delCTT (p.Phe508del) begin to be a useful treatment for CF patients bearing p.Phe508del. This mutation has been identified in different genetic contexts, alone or in combination with variants in cis. Until now, 21 exonic variants in cis of p.Phe508del have been identified, albeit at a low frequency. The aim of this study was to evaluate their impact on the efficacy of CFTR-directed corrector/potentiator therapy (Orkambi). The analysis by minigene showed that two out of 15 cis variants tested increased exon skipping (c.609C > T and c.2770G > A). Four cis variants were studied functionally in the absence of p.Phe508del, one of which was found to be deleterious for protein maturation c.1399C > T (p.Leu467Phe). In the presence of p.Phe508del, this variant was the only to prevent the response to Orkambi treatment. This study showed that some patients carrying p.Phe508del complex alleles are predicted to poorly respond to corrector/potentiator treatments. Our results underline the importance to validate treatment efficacy in the context of complex alleles.

CFTR-France, a national relational patient database for sharing genetic and phenotypic data associated with rare CFTR variants.

Most of the 2,000 variants identified in the CFTR (cystic fibrosis transmembrane regulator) gene are rare or private. Their interpretation is hampered by the lack of available data and resources, making patient care and genetic counseling challenging. We developed a patient-based database dedicated to the annotations of rare CFTR variants in the context of their cis- and trans-allelic combinations. Based on almost 30 years of experience of CFTR testing, CFTR-France (https://cftr.iurc.montp.inserm.fr/cftr) currently compiles 16,819 variant records from 4,615 individuals with cystic fibrosis (CF) or CFTR-RD (related disorders), fetuses with ultrasound bowel anomalies, newborns awaiting clinical diagnosis, and asymptomatic compound heterozygotes. For each of the 736 different variants reported in the database, patient characteristics and genetic information (other variations in cis or in trans) have been thoroughly checked by a dedicated curator. Combining updated clinical, epidemiological, in silico, or in vitro functional data helps to the interpretation of unclassified and the reassessment of misclassified variants. This comprehensive CFTR database is now an invaluable tool for diagnostic laboratories gathering information on rare variants, especially in the context of genetic counseling, prenatal and preimplantation genetic diagnosis. CFTR-France is thus highly complementary to the international database CFTR2 focused so far on the most common CF-causing alleles.

Identification of a novel 5' alternative CFTR mRNA isoform in a patient with nasal polyposis and CFTR mutations.

Cystic fibrosis may be revealed by nasal polyposis (NP) starting early in life. We performed cystic fibrosis transmembrane conductance regulator (CFTR) DNA and mRNA analyses in the family of a 12-year-old boy presenting with NP and a normal sweat test. Routine DNA analysis only showed the heterozygous c.2551C>T (p.Arg851*) mutation in the child and the father. mRNA analysis showed partial exon skipping due to c.2551C>T and a significant increase in total CFTR mRNA in the patient and the mother, which was attributable to the heterozygous c. -2954G>A variant in the distant promoter region, as demonstrated by in vitro luciferase assays. The 5' rapid amplification of cDNA ends analysis showed the presence of a novel transcript, where the canonical exon 1 was replaced by an alternative exon called 1a-Long. This case report could represent the first description of a CFTR-related disorder associated with the presence of a 5' alternative, probably nonfunctional transcript, similar to those of fetal origin.

ABC transporters involved in respiratory and cholestatic diseases: From rare to very rare monogenic diseases.

ATP-binding cassette (ABC) transporters constitute a 49-member superfamily in humans. These proteins, most of them being transmembrane, allow the active transport of an important variety of substrates across biological membranes, using ATP hydrolysis as an energy source. For an important proportion of these ABC transporters, genetic variations of the loci encoding them have been correlated with rare genetic diseases, including cystic fibrosis and interstitial lung disease (variations in CFTR/ABCC7 and ABCA3) as well as cholestatic liver diseases (variations in ABCB4 and ABCB11). In this review, we first describe these ABC transporters and how their molecular dysfunction may lead to human diseases. Then, we propose a classification of the genetic variants according to their molecular defect (expression, traffic, function and/or stability), which may be considered as a general guideline for all ABC transporters' variants. Finally, we discuss recent progress in the field of targeted pharmacotherapy, which aim to correct specific molecular defects using small molecules. In conclusion, we are opening the path to treatment repurposing for diseases involving similar deficiencies in other ABC transporters.

Prevalence, Characteristics, and Impact on Prognosis of Aortic Stenosis in Patients With Cardiac Amyloidosis.

BACKGROUND: Cardiac amyloidosis (CA) is frequently found in older patients with aortic stenosis (AS). However, the prevalence of AS among patients with CA is unknown. The objective was to study the prevalence and prognostic impact of AS among patients with CA. METHODS AND RESULTS: We conducted a retrospective analysis of a prospective registry comprising 976 patients with native aortic valves who were confirmed with wild type transthyretin amyloid (ATTRwt), hereditary variant transthyretin amyloid (ATTRv), or immunoglobulin light-chain (AL) CA. CA patients' echocardiograms were re-analyzed focusing on the aortic valve. Multivariable Cox regression analysis was performed to assess the mortality risk associated with moderate or greater AS in ATTRwt CA. The crude prevalence of AS among patients with CA was 26% in ATTRwt, 8% in ATTRv, and 5% in AL. Compared with population-based controls, all types of CA had higher age- and sex-standardized rate ratios (SRRs) of having any degree of AS (AL: SRR, 2.62; 95% Confidence Interval (CI) [1.09-3.64]; ATTRv: SRR, 3.41; 95%CI [1.64-4.60]; ATTRwt: SRR, 10.8; 95%CI [5.25-14.53]). Compared with hospital controls, only ATTRwt had a higher SRR of having any degree of AS (AL: SRR, 0.97, 95%CI [0.56-1.14]; ATTRv: SRR, 1.27; 95%CI [0.85-1.44]; ATTRwt: SRR, 4.01; 95%CI [2.71-4.54]). Among patients with ATTRwt, moderate or greater AS was not associated with increased all-cause death after multivariable adjustment (hazard ratio, 0.71; 95%CI [0.42-1.19]; P=0.19). CONCLUSIONS: Among patients with CA, ATTRwt but not ATTRv or AL is associated with a higher prevalence of patients with AS compared with hospital controls without CA, even after adjusting for age and sex. In our population, having moderate or greater AS was not associated with a worse outcome in patients with ATTRwt.

Phenotype and prognostic factors in geriatric and non-geriatric patients with transthyretin cardiomyopathy.

AIMS: Transthyretin cardiac amyloidosis (ATTR-CM) may be an underestimated cause of heart failure among geriatric patients and represent a unique phenotype and prognostic profile. METHODS AND RESULTS: This retrospective, observational, cohort study characterizes cardiac and extracardiac disorders at diagnosis and assesses prognosis among ATTR-CM patients based on age (geriatric vs. non-geriatric) and amyloidosis subtype (wild type, ATTRwt and hereditary, ATTRv). In total, 943 patients with ATTR-CM were included, of which 306 had ATTRv and 637 had ATTRwt. Among these, 331 (35.1%) were non-geriatric (<75 years), and 612 (64.9%) were geriatric (≥75 years). The population exhibited conduction abnormalities, atrial fibrillation and ischaemic heart disease that progressively deteriorated with age. Among ATTRwt patients, peripheral neuropathy, neurovegetative symptoms, and hearing loss were present across all age groups, but reports of carpal tunnel symptoms or surgery decreased with age. Conversely, among ATTRv patients, reports of extracardiac symptoms increased with age and Val122ILe mutation was highly prevalent among geriatric patients. The 3-year survival was higher among non-geriatric ATTR-CM patients (76%) than geriatric patients (55%) and predictors of 3-year mortality differed. Notably, predictors identified among geriatric patients were alkaline phosphatase (ALP) (HR = 1.004, 95% CI: [0.001-1.100)], troponin T hs (HR = 1.005, 95% CI: [1.001-1.120)] and tricuspid insufficiency (HR = 1.194, 95% CI: [1.02-1.230)]. Whereas, among non-geriatric patients, NT-proBNP (HR = 1.002, 95% CI: [1.02-1.04], global longitudinal strain (HR = 0.95, 95% CI: [0.922-0.989], and glomerular filtration rate (HR = 0.984, 95% CI: [0.968-1.00) were identified. We propose a 3-stage prognostic staging system combining troponin T hs (≥44 ng/L) and ALP levels (≥119 UI/L). In the geriatric population, this model discriminated survival more precisely than the National Amyloidosis Centre staging, particularly for classifying between stage 1 (82%), stage 2 (50%) and stage 3 (32%) for ATTRv and ATTRwt. CONCLUSIONS: These diagnostic and prognostic indicators, along with ATTR subtype, highlight the distinct characteristics of this important, geriatric ATTR-CM patient group. Recognizing these mortality markers can be valuable for geriatricians to improve the prognostic quality management of geriatric patients with ATTR-CM.

Alternative splicing of in-frame exon associated with premature termination codons: implications for readthrough therapies.

The correction of premature termination codons (PTCs) by agents that promote readthrough represents a promising emerging tool for the treatment of many genetic diseases. The efficiency of the treatment, however, varies depending on the stop codon itself and the amount of correctible transcripts related to the efficiency of nonsense-mediated decay. In the current study, a screen by in vitro minigene assay of all six PTCs described in exon 15 of the CFTR gene demonstrated alternative splicing to differing degrees for five of them. Of the five, PTC mutations c.2537G>A (p.Trp846*(UAG) ) and c.2551C>T (p.Arg851*) cause the greatest proportion of transcripts lacking exon 15; both mutations altering exonic splicing regulatory elements. In order to increase the amount of full-length transcripts, different pharmacological treatments were performed showing both negative and positive effects on exon inclusion for the same mutation. Therefore, the total amount of transcripts together with the splicing profile should be assessed to anticipate and improve efficacy of readthrough therapy.