A Comprehensive Cohort Analysis Comparing Growth and GH Therapy Response in IGF1R Mutation Carriers and SGA Children.

CONTEXT: IGF1 receptor mutations (IGF1RM) are rare; however, patients exhibit pronounced growth retardation without catch-up. Although several case reports exist, a comprehensive statistical analysis investigating growth profile and benefit of recombinant human growth hormone (rhGH) treatment is still missing. OBJECTIVE AND METHODS: Here, we compared IGF1RM carriers (n = 23) retrospectively regarding birth parameters, growth response to rhGH therapy, near final height, and glucose/insulin homeostasis to treated children born small for gestational age (SGA) (n = 34). Additionally, health profiles of adult IGF1RM carriers were surveyed by a questionnaire. RESULTS: IGF1RM carriers were significantly smaller at rhGH initiation and had a diminished first-year response compared to SGA children (Δ height standard deviation score: 0.29 vs. 0.65), resulting in a lower growth response under therapy. Interestingly, the number of poor therapy responders was three times higher for IGF1RM carriers than for SGA patients (53 % vs. 17 %). However, most IGF1RM good responders showed catch-up growth to the levels of SGA patients. Moreover, we observed no differences in homeostasis model assessment of insulin resistance before treatment, but during treatment insulin resistance was significantly increased in IGF1RM carriers compared to SGA children. Analyses in adult mutation carriers indicated no increased occurrence of comorbidities later in life compared to SGA controls. CONCLUSION: In summary, IGF1RM carriers showed a more pronounced growth retardation and lower response to rhGH therapy compared to non-mutation carriers, with high individual variability. Therefore, a critical reevaluation of success should be performed periodically. In adulthood, we could not observe a significant influence of IGF1RM on metabolism and health of carriers.

Acquired Resistance of EGFR-Mutated Lung Cancer to Tyrosine Kinase Inhibitor Treatment Promotes PARP Inhibitor Sensitivity.

Lung cancers with oncogenic mutations in the epidermal growth factor receptor (EGFR) invariably acquire resistance to tyrosine kinase inhibitor (TKI) treatment. Vulnerabilities of EGFR TKI-resistant cancer cells that could be therapeutically exploited are incompletely understood. Here, we describe a poly (ADP-ribose) polymerase 1 (PARP-1) inhibitor-sensitive phenotype that is conferred by TKI treatment in vitro and in vivo and appears independent of any particular TKI resistance mechanism. We find that PARP-1 protects cells against cytotoxic reactive oxygen species (ROS) produced by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX). Compared to TKI-naive cells, TKI-resistant cells exhibit signs of increased RAC1 activity. PARP-1 catalytic function is required for PARylation of RAC1 at evolutionarily conserved sites in TKI-resistant cells, which restricts NOX-mediated ROS production. Our data identify a role of PARP-1 in controlling ROS levels upon EGFR TKI treatment, with potentially broad implications for therapeutic targeting of the mechanisms that govern the survival of oncogene-driven cancer cells.

A new p.(Ile66Serfs*93) IGF2 variant is associated with pre- and postnatal growth retardation.

Objective The IGF/IGF1R axis is involved in the regulation of human growth. Both IGF1 and IGF2 can bind to the IGF1R in order to promote growth via the downstream PI3K/AKT pathway. Pathogenic mutations in IGF1 and IGF1R determine intrauterine growth restriction and affect postnatal body growth. However, to date, there are only few reports of pathogenic IGF2 mutations causing severe prenatal, as well as postnatal growth retardation. Results Here we describe a de novo c.195delC IGF2 variant (NM_000612, p.(Ile66Serfs*93)) in a 4-year-old patient with severe pre- and post-natal growth retardation in combination with dystrophy, facial dimorphism, finger deformities, as well as a patent ductus. Cloning and sequencing of a long-range PCR product harboring the deletion and a SNP informative site chr11:2153634 (rs680, NC_000011.9:g.2153634T>C) demonstrated that the variant resided on the paternal allele. This finding is consistent with the known maternal imprinting of IGF2. 3D protein structure prediction and overexpression studies demonstrated that the p.(Ile66Serfs*93) IGF2 gene variation resulted in an altered protein structure that impaired ligand/receptor binding and thus prevents IGF1R activation. Conclusion The severity of the phenotype in combination with the dominant mode of transmission provides further evidence for the involvement of IGF2 in growth disorders.

IGF1R Gene Alterations in Children Born Small for Gestitional Age (SGA).

BACKGROUND: Small for gestational age (SGA)-born children are a heterogeneous group with few genetic causes reported. Genetic alterations in the IGF1 receptor (IGF1R) are found in some SGA children. AIM: To investigate whether alterations in IGF1R gene are present in SGA born children. PATIENTS AND METHODS: We analysed 64 children born SGA who stayed short (mean -3.25 ± 0.9 SDS) within the first 4 years of age, and 36 SGA children who caught up growth (0.20 ± 1.1 SDS). PCR products of all coding IGF1R exons were screened by dHPLC followed by direct sequencing of conspicuous fragments to identify small nucleotide variants. The presence of IGF1R gene copy number alterations was determined by Multiplex Ligation-dependent Probe Amplification (MLPA). RESULTS: The cohort of short SGA born children revealed a heterozygous, synonymous variant c.3453C > T in one patient and a novel heterozygous 3 bp in-frame deletion (c.3234_3236delCAT) resulting in one amino acid deletion (p.Ile1078del) in another patient. The first patient had normal serum levels of IGF1. The second patient had unusually low IGF1 serum concentrations (-1.57 SD), which contrasts previously published data where IGF1 levels rarely are found below the age-adjusted mean. CONCLUSIONS: IGF1R gene alterations were present in 2 of 64 short SGA children. The patients did not have any dysmorphic features or developmental delay. It is remarkable that one of them had significantly decreased serum concentrations of IGF1. Growth response to GH treatment in one of the patients was favourable, while the second one discontinued the treatment, but with catch-up growth.

Combined pituitary hormone deficiency due to gross deletions in the POU1F1 (PIT-1) and PROP1 genes.

Pituitary development depends on a complex cascade of interacting transcription factors and signaling molecules. Lesions in this cascade lead to isolated or combined pituitary hormone deficiency (CPHD). The aim of this study was to identify copy number variants (CNVs) in genes known to cause CPHD and to determine their structure. We analyzed 70 CPHD patients from 64 families. Deletions were found in three Turkish families and one family from northern Iraq. In one family we identified a 4.96 kb deletion that comprises the first two exons of POU1F1. In three families a homozygous 15.9 kb deletion including complete PROP1 was discovered. Breakpoints map within highly homologous AluY sequences. Haplotype analysis revealed a shared haplotype of 350 kb among PROP1 deletion carriers. For the first time we were able to assign the boundaries of a previously reported PROP1 deletion. This gross deletion shows strong evidence to originate from a common ancestor in patients with Kurdish descent. No CNVs within LHX3, LHX4, HESX1, GH1 and GHRHR were found. Our data prove multiplex ligation-dependent probe amplification to be a valuable tool for the detection of CNVs as cause of pituitary insufficiencies and should be considered as an analytical method particularly in Kurdish patients.

EGFR-activating mutations correlate with a Fanconi anemia-like cellular phenotype that includes PARP inhibitor sensitivity.

In patients with lung cancer whose tumors harbor activating mutations in the EGF receptor (EGFR), increased responses to platinum-based chemotherapies are seen compared with wild-type cancers. However, the mechanisms underlying this association have remained elusive. Here, we describe a cellular phenotype of cross-linker sensitivity in a subset of EGFR-mutant lung cancer cell lines that is reminiscent of the defects seen in cells impaired in the Fanconi anemia pathway, including a pronounced G2-M cell-cycle arrest and chromosomal radial formation. We identified a defect downstream of FANCD2 at the level of recruitment of FAN1 nuclease and DNA interstrand cross-link (ICL) unhooking. The effect of EGFR mutation was epistatic with FANCD2. Consistent with the known role of FANCD2 in promoting RAD51 foci formation and homologous recombination repair (HRR), EGFR-mutant cells also exhibited an impaired RAD51 foci response to ICLs, but not to DNA double-strand breaks. EGFR kinase inhibition affected RAD51 foci formation neither in EGFR-mutant nor wild-type cells. In contrast, EGFR depletion or overexpression of mutant EGFR in wild-type cells suppressed RAD51 foci, suggesting an EGFR kinase-independent regulation of DNA repair. Interestingly, EGFR-mutant cells treated with the PARP inhibitor olaparib also displayed decreased FAN1 foci induction, coupled with a putative block in a late HRR step. As a result, EGFR-mutant lung cancer cells exhibited olaparib sensitivity in vitro and in vivo. Our findings provide insight into the mechanisms of cisplatin and PARP inhibitor sensitivity of EGFR-mutant cells, yielding potential therapeutic opportunities for further treatment individualization in this genetically defined subset of lung cancer.

Detection of impaired homologous recombination repair in NSCLC cells and tissues.

INTRODUCTION: Homologous recombination repair (HRR) is a critical pathway for the repair of DNA damage caused by cisplatin or poly-ADP ribose polymerase (PARP) inhibitors. HRR may be impaired by multiple mechanisms in cancer, which complicates assessing the functional HRR status in cells. Here, we monitored the ability of non-small-cell lung cancer (NSCLC) cells to form subnuclear foci of DNA repair proteins as a surrogate of HRR proficiency. METHODS: We assessed clonogenic survival of 16 NSCLC cell lines in response to cisplatin, mitomycin C (MMC), and the PARP inhibitor olaparib. Thirteen tumor explants from patients with NSCLC were subjected to cisplatin ex vivo. Cells were assayed for foci of repair-associated proteins such as BRCA1, FANCD2, RAD51, and γ-H2AX. RESULTS: Four cell lines (25%) showed an impaired RAD51 foci-forming ability in response to cisplatin. Impaired foci formation correlated with cellular sensitivity to cisplatin, MMC and olaparib. Foci responses complemented or superseded genomic information suggesting alterations in the ATM/ATR and FA/BRCA pathways. Because baseline foci in untreated cells did not predict drug sensitivity, we adapted an ex vivo biomarker assay to monitor damage-induced RAD51 foci in NSCLC explants from patients. Ex vivo cisplatin treatment of explants identified two tumors (15%) exhibiting compromised RAD51 foci induction. CONCLUSIONS: A fraction of NSCLC harbors HRR defects that may sensitize the affected tumors to DNA-damaging agents including PARP inhibitors. We propose that foci-based functional biomarker assays represent a powerful tool for prospective determination of treatment sensitivity, but will require ex vivo techniques for induction of DNA damage to unmask the underlying HRR defect.