Despite initial and sometimes dramatic responses of specific NSCLC tumors to EGFR TKIs, nearly all will develop resistance and relapse. Gene expression analysis of NSCLC cell lines treated with the ...EGFR TKI, gefitinib, revealed increased levels of FGFR2 and FGFR3 mRNA. Analysis of gefitinib action on a larger panel of NSCLC cell lines verified that FGFR2 and FGFR3 expression is increased at the mRNA and protein level in NSCLC cell lines in which the EGFR is dominant for growth signaling, but not in cell lines where EGFR signaling is absent. A luciferase reporter containing 2.5 kilobases of fgfr2 5' flanking sequence was activated after gefitinib treatment, indicating transcriptional regulation as a contributing mechanism controlling increased FGFR2 expression. Induction of FGFR2 and FGFR3 protein as well as fgfr2-luc activity was also observed with Erbitux, an EGFR-specific monoclonal antibody. Moreover, inhibitors of c-Src and MEK stimulated fgfr2-luc activity to a similar degree as gefitinib, suggesting that these pathways may mediate EGFR-dependent repression of FGFR2 and FGFR3. Importantly, our studies demonstrate that EGFR TKI-induced FGFR2 and FGFR3 are capable of mediating FGF2 and FGF7 stimulated ERK activation as well as FGF-stimulated transformed growth in the setting of EGFR TKIs. In conclusion, this study highlights EGFR TKI-induced FGFR2 and FGFR3 signaling as a novel and rapid mechanism of acquired resistance to EGFR TKIs and suggests that treatment of NSCLC patients with combinations of EGFR and FGFR specific TKIs may be a strategy to enhance efficacy of single EGFR inhibitors.
The human FGF receptors (FGFRs) play critical roles in various human cancers, and several FGFR inhibitors are currently under clinical investigation. Resistance usually results from selection for ...mutant kinases that are impervious to the action of the drug or from up-regulation of compensatory signaling pathways. Preclinical studies have demonstrated that resistance to FGFR inhibitors can be acquired through mutations in the FGFR gatekeeper residue, as clinically observed for FGFR4 in embryonal rhabdomyosarcoma and neuroendocrine breast carcinomas. Here we report on the use of a structure-based drug design to develop two selective, next-generation covalent FGFR inhibitors, the FGFR irreversible inhibitors 2 (FIIN-2) and 3 (FIIN-3). To our knowledge, FIIN-2 and FIIN-3 are the first inhibitors that can potently inhibit the proliferation of cells dependent upon the gatekeeper mutants of FGFR1 or FGFR2, which confer resistance to first-generation clinical FGFR inhibitors such as NVP-BGJ398 and AZD4547. Because of the conformational flexibility of the reactive acrylamide substituent, FIIN-3 has the unprecedented ability to inhibit both the EGF receptor (EGFR) and FGFR covalently by targeting two distinct cysteine residues. We report the cocrystal structure of FGFR4 with FIIN-2, which unexpectedly exhibits a “DFG-out” covalent binding mode. The structural basis for dual FGFR and EGFR targeting by FIIN3 also is illustrated by crystal structures of FIIN-3 bound with FGFR4 V550L and EGFR L858R. These results have important implications for the design of covalent FGFR inhibitors that can overcome clinical resistance and provide the first example, to our knowledge, of a kinase inhibitor that covalently targets cysteines located in different positions within the ATP-binding pocket.
Significance Inhibitors of the FGF receptors (FGFRs) are currently under clinical investigation for the treatment of various cancers. All currently approved kinase inhibitors eventually are rendered useless by the emergence of drug-resistant tumors. We used structure-based drug design to develop the first, to our knowledge, selective, next-generation covalent FGFR inhibitors that can overcome the most common form of kinase inhibitor resistance, the mutation of the so-called “gatekeeper” residue located in the ATP-binding pocket. We also describe a novel kinase inhibitor design strategy that uses a single electrophile to target covalently cysteines that are located in different positions within the ATP-binding pocket. These results have important implications for the design of covalent FGFR inhibitors that can overcome clinical resistance.
FGF2 is an essential growth factor implicated in osteoarthritis (OA), and deletion of full‐length FGF2 (Fgf2ALLKO) leads to murine OA. However, the FGF2 gene encodes both high‐molecular‐weight (HMW) ...and low‐molecular‐weight (LMW) isoforms, and the effects of selectively ablating individual isoforms, as opposed to total FGF2, has not been investigated in the context of OA. We undertook this study to examine whether mice lacking HMW FGF2 (Fgf2HMWKO) or LMW FGF2 (Fgf2LMWKO) develop OA and to further characterize the observed OA phenotype in Fgf2ALLKO mice. Fgf2HMWKO mice never developed OA, but 6‐ and 9‐month‐old Fgf2LMWKO and Fgf2ALLKO mice displayed signs of OA, including eroded articular cartilage, altered subchondral bone and trabecular architecture, and increased OA marker enzyme levels. Even with mechanical induction of OA, Fgf2HMWKO mice were protected against OA, whereas Fgf2LMWKO and Fgf2ALLKO displayed OA‐like changes of the subchondral bone. Before exhibiting OA symptoms, Fgf2LMWKO or Fgf2ALLKO joints displayed differential expression of genes encoding key regulatory proteins, including interleukin‐1β, insulin‐like growth factor 1, bone morphogenetic protein 4, hypoxia‐inducible factor 1, B‐cell lymphoma 2, Bcl2‐associated X protein, a disintegrin and metalloproteinase with thrombospondin motifs 5, ETS domain‐containing protein, and sex‐determining region Y box 9. Moreover, Fgf2LMWKO OA cartilage exhibited increased FGF2, FGF23, and FGFR1 expression, whereas Fgf2HMWKO cartilage had increased levels of FGFR3, which promotes anabolism in cartilage. These results demonstrate that loss of LMW FGF2 results in catabolic activity in joint cartilage, whereas absence of HMW FGF2 with only the presence of LMW FGF2 offers protection from OA.
FGF2 is an essential growth factor implicated in osteoarthritis (OA), and deletion of full‐length FGF2 leads to murine OA. However, the FGF2 gene encodes both high‐molecular‐weight (HMW) and low‐molecular‐weight (LMW) isoforms, and the effects of selectively ablating individual isoforms, as opposed to total FGF2, has not been investigated in the context of OA. In this study we demonstrated that loss of LMW FGF2 resulted in catabolic activity in joint cartilage, whereas the absence of HMW FGF2 with only the presence of LMW FGF2 offered protection from OA.
CDATAAim: The present study investigated whether melatonin (MEL) and enriched environment (EE) might protect against intrauterine growth retardation (IUGR) in rats.
Sprague-Dawley rats were randomly ...allocated to 3 groups: control (C), model (M) and EE+MEL group. Animals were housed in an enriched environment (EE+MEL group) or remained in a standard environment (C group, M group). IUGR rat model was built by feeding a low protein diet during pregnancy. MEL was administered by gavaging. At day 1 post-birth, the baseline characteristics and serum biochemical parameters, morphology of liver and small intestine, enzyme activities, and mRNA expression levels of fetal rats were determined. The autophagy marker LC3 and Beclin1 were determined by western blot analysis.
EE+MEL markedly improved the baseline characteristics, hepatic and intestinal morphology of IUGR fetuses. In addition, the lactase activities in the fetal intestine were markedly increased by the EE+MEL. The levels of serum somatostatin (SST), Growth hormone (GH), GH releasing hormone (GHRH), Insulin-like Growth Factor 1 (IGF-1), triiodothyronine (T3), and tetraiodothyronine (T4) were found to be recovered by EE+MEL. In addition, the EE+MEL significantly ameliorated the mRNA expression of SST, GHRH, and GHRH receptor (GHRHR), GH, GHR, IGF-1, and IGF-1 receptor (IGF1R), IGF binding protein-1 (IGFBP1), mammalian target of rapamycin (mTOR), S6 kinase 1 (S6K1) and eukaryotic initiation factor 4E (eIF4E)-binding protein 1 (4EBP1) in fetuses. In IUGR fetal livers, LC3 and Beclin1 were found to be increased at birth, while LC3 and Beclin1 were observed to be significantly decreased in the EE+MEL group.
EE+MEL could improve fetal rats' baseline characteristics, serum biochemical parameters, birth weight, intestinal and hepatic morphology and enzyme activities. These effects could be explained by the activation of the IGF-1/IGFBP1 and IGF-1/mTOR/S6K1/4EBP1 signaling pathway and autophagy inhibition.
Fibroblast growth factors (FGF) play an important role during embryo development. To date, the role of FGF and the respective receptors (FGFR) during the preimplantation phase in cattle are not fully ...characterized. We examined FGF1, FGF2, FGFR1, FGFR2, and FGFR3 in cyclic and early pregnant heifers at Days 12, 15, and 18 after insemination (Day 0). Endometrial FGF1 mRNA transcript abundance in heifers varied significantly with respect to the day after insemination, the pregnancy status, and their interaction. The expression was higher in nonpregnant than in pregnant heifers at Day 18. The conceptus transcripts abundance of FGFR2 and FGFR3 were significantly lower at Day 15 than 18. In the endometrium, FGF1 protein abundance significantly decreased from Day 12 onwards and FGF2 protein abundance showed a minor, but a significant increase at Day 15 in comparison to Days 12 and 18. We concluded that the decrease in FGF1 mRNA expression in pregnant heifers at Day 18 points towards a potential contribution of FGF1 in the preimplantation process. Additionally, successful embryo elongation might require a spatiotemporal FGF2 protein increase in the endometrium.
Monitoring cambial phenology and intra-annual growth dynamics is a useful approach for characterizing the tree growth response to climate change. However, there have been few reports concerning ...intra-annual wood formation in lowland temperate forests with high time resolution, especially for the comparison between deciduous and coniferous species. The main objective of this study was to determine how the timing, duration and rate of radial growth change between species as related to leaf phenology and the dynamics of non-structural carbohydrates (NSC) under the same climatic conditions. We studied two deciduous species, Fagus sylvatica L. and Quercus petraea (Matt.) Liebl., and an evergreen conifer, Pinus sylvestris L. During the 2009 growing season, we weekly monitored (i) the stem radial increment using dendrometers, (ii) the xylem growth using microcoring and (iii) the leaf phenology from direct observations of the tree crowns. The NSC content was also measured in the eight last rings of the stem cores in April, June and August 2009. The leaf phenology, NSC storage and intra-annual growth were clearly different between species, highlighting their contrasting carbon allocation. Beech growth began just after budburst, with a maximal growth rate when the leaves were mature and variations in the NSC content were low. Thus, beech radial growth seemed highly dependent on leaf photosynthesis. For oak, earlywood quickly developed before budburst, which probably led to the starch decrease quantified in the stem from April to June. For pine, growth began before the needles unfolding and the lack of NSC decrease during the growing season suggested that the substrates for radial growth were new assimilates of the needles from the previous year. Only for oak, the pattern determined from the intra-annual growth measured using microcoring differed from the pattern determined from dendrometer data. For all species, the ring width was significantly influenced by growth duration and not by growth rate, which differs from previous studies. The observed between-species difference at the intra-annual scale is key information for anticipating suitability of future species in temperate forests.
The Growth Hormone Research Society (GRS) convened a Workshop in March 2019 to evaluate the diagnosis and therapy of short stature in children. Forty-six international experts participated at the ...invitation of GRS including clinicians, basic scientists, and representatives from regulatory agencies and the pharmaceutical industry. Following plenary presentations addressing the current diagnosis and therapy of short stature in children, breakout groups discussed questions produced in advance by the planning committee and reconvened to share the group reports. A writing team assembled one document that was subsequently discussed and revised by participants. Participants from regulatory agencies and pharmaceutical companies were not part of the writing process. Short stature is the most common reason for referral to the pediatric endocrinologist. History, physical examination, and auxology remain the most important methods for understanding the reasons for the short stature. While some long-standing topics of controversy continue to generate debate, including in whom, and how, to perform and interpret growth hormone stimulation tests, new research areas are changing the clinical landscape, such as the genetics of short stature, selection of patients for genetic testing, and interpretation of genetic tests in the clinical setting. What dose of growth hormone to start, how to adjust the dose, and how to identify and manage a suboptimal response are still topics to debate. Additional areas that are expected to transform the growth field include the development of long-acting growth hormone preparations and other new therapeutics and diagnostics that may increase adult height or aid in the diagnosis of growth hormone deficiency.
The insulin and insulin-like signaling (IIS) network regulates cellular processes including pre- and postnatal growth, cellular development, wound healing, reproduction, and longevity. Despite their ...importance in the physiology of vertebrates, the study of the specific functions of the top regulators of the IIS network, insulin-like growth factors (IGFs) and IGF binding proteins (IGFBPs), has been mostly limited to a few model organisms. To expand our understanding of this network, we performed quantitative gene expression of IGF hormones in liver and qualitative expression of IGFBPs across tissues and developmental stages in a model reptile, the brown anole lizard (
). We found that lizards express IGF2 across all life stages (preoviposition embryos to adulthood) and at a higher level than IGF1, which is opposite to patterns seen in laboratory rodents but similar to those seen in humans and other vertebrate models. IGFBP expression was ubiquitous across tissues (brain, gonad, heart, liver, skeletal muscle, tail, and regenerating tail) in adults, apart from IGFBP5, which was variable. These findings provide an essential foundation for further developing the anole lizard as a physiological and biomedical reptile model, as well as expanding our understanding of the function of the IIS network across species.
The pathogenesis of the higher occurrence of peptic ulcer disease in cirrhotic patients is complex. Platelets can stimulate angiogenesis and promote gastric ulcer healing. We compared the expressions ...of proangiogenic growth factors and their receptors in the gastric ulcer margin between cirrhotic patients with thrombocytopenia and those of non-cirrhotic patients to elucidate possible mechanisms.
Eligible cirrhotic patients (n = 55) and non-cirrhotic patients (n = 55) who had gastric ulcers were enrolled. Mucosa from the gastric ulcer margin and non-ulcer areas were sampled and the mRNA expressions of the proangiogenic growth factors (vascular endothelial growth factor VEGF, platelet derived growth factor PDGF, basic fibroblast growth factor bFGF) and their receptors (VEGFR1, VEGFR2, PDGFRA, PDGFRB, FGFR1, FGFR2) were measured and compared. Platelet count and the expressions of these growth factors and their receptors were correlated with each other.
The two groups were comparable in terms of gender, ulcer size and infection rate of Helicobacter pylori. However, the cirrhotic group were younger in age, had a lower platelet count than those in the non-cirrhotic group (p<0.05). The cirrhotic patients had diminished mRNA expressions of PDGFB, VEGFR2, FGFR1, and FGFR2 in gastric ulcer margin when compared with those of the non-cirrhotic patients (p<0.05). Diminished expressions of PDGFB and VEGFR2, FGFR1, and FGFR2 were well correlated with the degree of thrombocytopenia in these cirrhotic patients (ρ>0.5, p<0.001).
Our findings implied that diminished activity of proangiogenic factors and their receptors may contribute to the pathogenesis of gastric ulcers in cirrhotic patients.
Platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) have served as prototypes for growth factor and receptor tyrosine kinase function for more than 25 years. Studies of PDGFs and ...PDGFRs in animal development have revealed roles for PDGFR-alpha signaling in gastrulation and in the development of the cranial and cardiac neural crest, gonads, lung, intestine, skin, CNS, and skeleton. Similarly, roles for PDGFR-beta signaling have been established in blood vessel formation and early hematopoiesis. PDGF signaling is implicated in a range of diseases. Autocrine activation of PDGF signaling pathways is involved in certain gliomas, sarcomas, and leukemias. Paracrine PDGF signaling is commonly observed in epithelial cancers, where it triggers stromal recruitment and may be involved in epithelial-mesenchymal transition, thereby affecting tumor growth, angiogenesis, invasion, and metastasis. PDGFs drive pathological mesenchymal responses in vascular disorders such as atherosclerosis, restenosis, pulmonary hypertension, and retinal diseases, as well as in fibrotic diseases, including pulmonary fibrosis, liver cirrhosis, scleroderma, glomerulosclerosis, and cardiac fibrosis. We review basic aspects of the PDGF ligands and receptors, their developmental and pathological functions, principles of their pharmacological inhibition, and results using PDGF pathway-inhibitory or stimulatory drugs in preclinical and clinical contexts.
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