Targeted Agents in Esophagogastric Cancer Beyond Human Epidermal Growth Factor Receptor-2

Gastroesophageal cancers are highly diverse tumors in terms of their anatomic and molecular characteristics, making drug development challenging. Recent advancements in understanding the molecular profiles of these cancers have led to the identification of several new biomarkers. Ongoing clinical trials are investigating new targeted agents with promising results. CLDN18.2 has emerged as a biomarker with established activity of associated targeted therapies. Other targeted agents, such as bemarituzumab and DKN-01, are under active investigation. As new agents are incorporated into the treatment continuum, the questions of biomarker overlap, tumor heterogeneity, and toxicity management will need to be addressed.

Bemarituzumab as first-line treatment for locally advanced or metastatic gastric/gastroesophageal junction adenocarcinoma: final analysis of the randomized phase 2 FIGHT trial

BACKGROUND

We report the final results of the randomized phase 2 FIGHT trial that evaluated bemarituzumab, a humanized monoclonal antibody selective for fibroblast growth factor receptor 2b (FGFR2b), plus mFOLFOX6 in patients with FGFR2b-positive (2 + /3 + membranous staining by immunohistochemistry), HER-2-negative gastric or gastroesophageal junction cancer (GC).

METHODS

Patients received bemarituzumab (15 mg/kg) or placebo once every 2 weeks with an additional bemarituzumab (7.5 mg/kg) or placebo dose on cycle 1 day 8. All patients received mFOLFOX6. The primary endpoint was investigator-assessed progression-free survival (PFS). Secondary endpoints included overall survival (OS), objective response rate, and safety. Efficacy was evaluated after a minimum follow-up of 24 months.

RESULTS

In the bemarituzumab-mFOLFOX6 (N = 77) and placebo-mFOLFOX6 (N = 78) arms, respectively, 59.7% and 66.7% of patients were FGFR2b-positive in ≥ 10% of tumor cells. The median PFS (95% confidence interval [CI]) was 9.5 months (7.3-13.7) with bemarituzumab-mFOLFOX6 and 7.4 months (5.7-8.4) with placebo-mFOLFOX6 (hazard ratio [HR], 0.72; 95% CI 0.49-1.08); median OS (95% CI) was 19.2 (13.6-24.2) and 13.5 (9.3-15.9) months, respectively (HR 0.77; 95% CI 0.52-1.14). Observed efficacy in FGFR2b-positive GC in ≥ 10% of tumor cells was: PFS: HR 0.43 (95% CI 0.26-0.73); OS: HR 0.52 (95% CI 0.31-0.85). No new safety findings were reported.

CONCLUSIONS

In FGFR2b-positive advanced GC, the combination of bemarituzumab-mFOLFOX6 led to numerically longer median PFS and OS compared with mFOLFOX6 alone. Efficacy was more pronounced with FGFR2b overexpression in ≥ 10% of tumor cells. Confirmatory phase 3 trials are ongoing (NCT05052801, NCT05111626).

CLINICAL TRIAL REGISTRATION

NCT03694522.

Current and Future Biomarkers in Esophagogastric Adenocarcinoma

PURPOSE

Biomarker-based therapies have shown improved patient outcomes across various cancer types. The purpose of this review to summarize our knowledge of current and future biomarkers in esophagogastric adenocarcinoma (EGA).

METHODS

In this publication, we will review current standard biomarkers in patients with upper GI cancers. We will also discuss novel biomarkers that are under investigations and their associated therapies that are currently in clinical trials.

RESULTS

EGAa are a group of heterogeneous diseases, both anatomically and molecularly. There are several established biomarkers (HER2, PD-L1, microsattelite instability or mismatch repair protein expression) that allow for individualized treatments for patients with these cancers. There are also several emerging biomarkers for EGA, some of which have clinically relevant associated therapies. Claudin 18.2 is the furthest along among these. Anti-claudin antibody, zolbetuximab, improved overall survival in biomarker select patients with advanced GEA in two phase 3 studies. Other novel biomarkers, such as FGFR2b and DKN01, are also in the process of validation, and treatments based on the presence of these biomarkers are currently in clinical studies.

CONCLUSION

Ongoing efforts to identify novel biomarkers in EGA have led to enhanced subclassification of upper GI cancers. These advances, coupled with the strategic application of targeted therapies and immunotherapy when appropriate, hold promise to further improve patients outcomes.

Hepatocyte survival and proliferation by fibroblast growth factor 7 attenuates liver inflammation, and fibrogenesis during acute liver injury via paracrine mechanisms

Hepatocyte damage during liver injury instigates activation of macrophages and hepatic stellate cells (HSCs) resulting in liver inflammation and fibrosis respectively. Improving hepatocyte survival and proliferation thereby ameliorating inflammation and fibrosis represents a promising approach for the treatment of liver injury. In the liver, fibroblast growth factors (FGFs) play a crucial role in promoting hepatocyte proliferation and tissue regeneration. Among 22 FGFs, FGF7 induces hepatocyte survival and liver regeneration as shown previously in mouse models of cholestatic liver injury and partial hepatectomy. We hypothesized that FGF7 promotes hepatocyte survival and proliferation by interacting with FGFR2b, expressed on hepatocytes, and ameliorates liver injury (inflammation and early fibrogenesis) via paracrine mechanisms. To prove this hypothesis and to study the effect of FGF7 on hepatocytes and liver injury, we administered FGF7 exogenously to mice with acute carbon tetrachloride (CCl4)-induced liver injury. We thereafter studied the underlying mechanisms and the effect of exogenous FGF7 on hepatocyte survival and proliferation, and the consequent paracrine effects on macrophage-induced inflammation, and HSCs activation in vitro and in vivo. We observed that the expression of FGF7 as well as FGFR2 is upregulated during acute liver injury. Co-immunostaining of FGF7 and collagen-I confirmed that FGF7 is expressed by HSCs and is possibly captured by the secreted ECM. Immunohistochemical analysis of liver sections showed increased hepatocyte proliferation upon exogenous FGF7 treatment as determined by Ki67 expression. Mechanistically, exogenous FGF7 improved hepatocyte survival (and increased drug detoxification) via AKT and ERK pathways while maintaining hepatocyte quiescence restricting hepatocarcinogenesis via P27 pathways. Flow cytometry analysis revealed that improved hepatocyte survival and proliferation leads to a decrease in infiltrated monocytes-derived macrophages, as a result of reduced CCL2 (and CXCL8) expression by hepatocytes. Moreover, conditioned medium studies showed reduced collagen-I secretion by HSCs (indicative of HSCs activation) upon treatment with FGF7-treated hepatocytes conditioned medium. Altogether, we show that exogenous administration of FGF7 induces hepatocyte survival and proliferation and leads to amelioration of inflammatory response and fibrosis in acute liver injury via paracrine mechanisms. Our study further demonstrates that FGF7, FGF7 derivatives, or nano-engineered FGF7 may benefit patients with hepatic dysfunction.

FGF10 mitigates doxorubicin-induced myocardial toxicity in mice via activation of FGFR2b/PHLDA1/AKT axis

Doxorubicin is a common chemotherapeutic agent in clinic, but myocardial toxicity limits its use. Fibroblast growth factor (FGF) 10, a multifunctional paracrine growth factor, plays diverse roles in embryonic and postnatal heart development as well as in cardiac regeneration and repair. In this study we investigated the role of FGF10 as a potential modulator of doxorubicin-induced cardiac cytotoxicity and the underlying molecular mechanisms. Fgf10+/- mice and an inducible dominant negative FGFR2b transgenic mouse model (Rosa26rtTA; tet(O)sFgfr2b) were used to determine the effect of Fgf10 hypomorph or blocking of endogenous FGFR2b ligands activity on doxorubicin-induced myocardial injury. Acute myocardial injury was induced by a single injection of doxorubicin (25 mg/kg, i.p.). Then cardiac function was evaluated using echocardiography, and DNA damage, oxidative stress and apoptosis in cardiac tissue were assessed. We showed that doxorubicin treatment markedly decreased the expression of FGFR2b ligands including FGF10 in cardiac tissue of wild type mice, whereas Fgf10+/- mice exhibited a greater degree of oxidative stress, DNA damage and apoptosis as compared with the Fgf10+/+ control. Pre-treatment with recombinant FGF10 protein significantly attenuated doxorubicin-induced oxidative stress, DNA damage and apoptosis both in doxorubicin-treated mice and in doxorubicin-treated HL-1 cells and NRCMs. We demonstrated that FGF10 protected against doxorubicin-induced myocardial toxicity via activation of FGFR2/Pleckstrin homology-like domain family A member 1 (PHLDA1)/Akt axis. Overall, our results unveil a potent protective effect of FGF10 against doxorubicin-induced myocardial injury and identify FGFR2b/PHLDA1/Akt axis as a potential therapeutic target for patients receiving doxorubicin treatment.

FGFR2b is essential for salivary gland duct homeostasis and MAPK-dependent seromucous acinar cell differentiation

Exocrine secretory acinar cells in salivary glands (SG) are critical for oral health and loss of functional acinar cells is a major clinical challenge. Fibroblast growth factor receptors (FGFR) are essential for early development of multiple organs, including SG. However, the role of FGFR signaling in specific epithelial SG populations later in development and during acinar differentiation are unknown. Here, we predicted FGFR dependence in specific populations using scRNAseq data and conditional mouse models to delete FGFRs in vivo. We identifed essential roles for FGFRs in craniofacial and early SG development, as well as progenitor function during duct homeostasis. Importantly, we discovered that FGFR2b was critical for seromucous and serous acinar cell differentiation and secretory gene expression (Bpifa2 and Lpo) via MAPK signaling, while FGFR1b was dispensable. We show that FGF7, expressed by myoepithelial cells (MEC), activated the FGFR2b-dependent seromucous transcriptional program. We propose a model where MEC-derived FGF7 drives seromucous acinar differentiaton, providing a rationale for targeting FGFR2b signaling in regenerative therapies to restore acinar function.

Fibroblast Growth Factor Receptor 2 Isoforms Detected via Novel RNA ISH as Predictive Biomarkers for Progestin Therapy in Atypical Hyperplasia and Low-Grade Endometrial Cancer

Simple Summary

Women diagnosed with low-grade endometrioid cancer (EEC) and its precursor lesion, atypical hyperplasia (AH) are frequently treated with hormonal therapy including levonorgestrel releasing intrauterine device (LNG-IUD) as an alternative to surgery. Biomarkers that inform which group of patients are more likely to respond to LNG-IUD are not available. The aim of this study was to document the response rate to LNG-IUD therapy in women with AH and EEC and identify potential biomarkers to guide treatment response. The overall response rate (ORR) for the whole cohort was 30/69 (~44%) with a higher ORR seen in AH (64%) compared to EEC (23%). Fibroblast Growth Factor Receptor (FGFR2) isoforms were detected using RNA in situ hybridization. The FGFR2c isoform was expressed in 16.7% of the samples, with those expressing FGFR2c 5-times more likely to have treatment failure. FGFR2 isoform expression could be used to guide treatment decisions following confirmation of this finding in an independent study.

Abstract

Women with atypical hyperplasia (AH) or well-differentiated early-stage endometrioid endometrial carcinoma (EEC) who wish to retain fertility and/or with comorbidities precluding surgery, are treated with progestin. Clinically approved predictive biomarkers for progestin therapy remain an unmet need. The objectives of this study were to document the overall response rate (ORR) of levonorgestrel intrauterine device (LNG-IUD) treatment, and determine the association of FGFR2b and FGFR2c expression with treatment outcome. BaseScope RNA ISH assay was utilized to detect expression of FGFR2b and FGFR2c mRNA in the diagnostic biopsies of 89 women (40 AH and 49 EEC) treated with LNG-IUD. Detailed clinical follow-up was available for 69 women which revealed an overall response rate (ORR) of 44% (30/69) with a higher ORR seen in AH (64%) compared to EEC (23%). The recurrence rate in women who initially responded to LNG-IUD was 10/30 (33.3%). RNA ISH was successful in 72 patients and showed FGFR2c expression in 12/72 (16.7%) samples. In the 59 women with detailed clinical follow-up and RNA-ISH data, women with tumours expressing FGFR2c were 5-times more likely to have treatment failure in both univariable (HR 5.08, p < 0.0001) and multivariable (HR 4.5, p < 0.002) Cox regression analyses. In conclusion, FGFR2c expression appears to be strongly associated with progestin treatment failure, albeit the ORR is lower in this cohort than previously reported. Future work to validate these findings in an independent multi-institutional cohort is needed.

A Comprehensive Analysis of Fibroblast Growth Factor Receptor 2b Signaling on Epithelial Tip Progenitor Cells During Early Mouse Lung Branching Morphogenesis

This study demonstrates that FGF10/FGFR2b signaling on distal epithelial progenitor cells, via ß-catenin/EP300, controls, through a comprehensive set of developmental genes, morphogenesis, and differentiation. Fibroblast growth factor (FGF) 10 signaling through FGF receptor 2b (FGFR2b) is mandatory during early lung development as the deletion of either the ligand or the receptor leads to lung agenesis. However, this drastic phenotype previously hampered characterization of the primary biological activities, immediate downstream targets and mechanisms of action. Through the use of a dominant negative transgenic mouse model (Rosa26rtTA; tet(o)sFgfr2b), we conditionally inhibited FGF10 signaling in vivo in E12.5 embryonic lungs via doxycycline IP injection to pregnant females, and in vitro by culturing control and experimental lungs with doxycycline. The impact on branching morphogenesis 9 h after doxycycline administration was analyzed by morphometry, fluorescence and electron microscopy. Gene arrays at 6 and 9 h following doxycycline administration were carried out. The relationship between FGF10 and ß-catenin signaling was also analyzed through in vitro experiments using IQ1, a pharmacological inhibitor of ß-catenin/EP300 transcriptional activity. Loss of FGF10 signaling did not impact proliferation or survival, but affected both adherens junctions (up-regulation of E-cadherin), and basement membrane organization (increased laminin). Gene arrays identified multiple direct targets of FGF10, including main transcription factors. Immunofluorescence showed a down-regulation of the distal epithelial marker SOX9 and mis-expression distally of the proximal marker SOX2. Staining for the transcriptionally-active form of ß-catenin showed a reduction in experimental vs. control lungs. In vitro experiments using IQ1 phenocopied the impacts of blocking FGF10. This study demonstrates that FGF10/FGFR2b signaling on distal epithelial progenitor cells via ß-catenin/EP300 controls, through a comprehensive set of developmental genes, cell adhesion, and differentiation.

Emerging Roles of Fibroblast Growth Factor 10 in Cancer

Whilst cross-talk between stroma and epithelium is critical for tissue development and homeostasis, aberrant paracrine stimulation can result in neoplastic transformation. Chronic stimulation of epithelial cells with paracrine Fibroblast Growth Factor 10 (FGF10) has been implicated in multiple cancers, including breast, prostate and pancreatic ductal adenocarcinoma. Here, we examine the mechanisms underlying FGF10-induced tumourigenesis and explore novel approaches to target FGF10 signaling in cancer.

Role of Fibroblast Growth Factor Receptor 2b in the Cross Talk between Autophagy and Differentiation: Involvement of Jun N-Terminal Protein Kinase Signaling

Fibroblast growth factor receptor 2b (FGFR2b) is a receptor tyrosine kinase expressed exclusively in epithelial cells. We previously demonstrated that FGFR2b induces autophagy and that this process is required for the triggering of FGFR2b-mediated early differentiation of keratinocytes. However, the molecular mechanisms regulating this interplay remain to be elucidated. Since we have also recently shown that Jun N-terminal protein kinase 1 (JNK1) signaling is involved in FGFR2b-induced autophagy and a possible role of the JNK pathway in epidermal differentiation has been suggested (though it is still debated), we investigated here the cross talk between FGFR2b-mediated autophagy and differentiation, focusing on the downstream JNK signaling. Biochemical, molecular, and immunofluorescence approaches in 2-dimensional (2-D) keratinocyte cultures and three-dimensional (3-D) organotypic skin equivalents confirmed that FGFR2b overexpression increased both autophagy and early differentiation. The use of FGFR2b substrate inhibitors and the silencing of JNK1 highlighted that this signaling is required not only for autophagy but also for the triggering of early differentiation. In contrast, the extracellular signal-regulated kinase 1 and 2 (ERK1/2) pathway did not appear to be involved in the two processes, and AKT signaling, whose activation contributes to the FGFR2b-mediated onset of keratinocyte differentiation, was not required for the triggering of autophagy. Overall, our results point to JNK1 as a signaling hub that regulates the interplay between FGFR2b-induced autophagy and differentiation.

Fibroblast Growth Factor 10 in Pancreas Development and Pancreatic Cancer

The tenacious prevalence of human pancreatic diseases such as diabetes mellitus and adenocarcinoma has prompted huge research interest in better understanding of pancreatic organogenesis. The plethora of signaling pathways involved in pancreas development is activated in a highly coordinated manner to assure unmitigated development and morphogenesis in vertebrates. Therefore, a complex mesenchymal-epithelial signaling network has been implicated to play a pivotal role in organogenesis through its interactions with other germ layers, specifically the endoderm. The Fibroblast Growth Factor Receptor FGFR2-IIIb splicing isoform (FGFR2b) and its high affinity ligand Fibroblast Growth Factor 10 (FGF10) are expressed in the epithelium and mesenchyme, respectively, and therefore are well positioned to transmit mesenchymal to epithelial signaling. FGF10 is a typical paracrine FGF and chiefly mediates biological responses by activating FGFR2b with heparin/heparan sulfate (HS) as cofactor. A substantial number of studies using genetically engineered mouse models have demonstrated an essential role of FGF10 in the development of many organs and tissues including the pancreas. During mouse embryonic development, FGF10 signaling is crucial for epithelial cell proliferation, maintenance of progenitor cell fate and branching morphogenesis in the pancreas. FGF10 is also implicated in pancreatic cancer, and that overexpression of FGFR2b is associated with metastatic invasion. A thorough understanding of FGF10 signaling machinery and its crosstalk with other pathways in development and pathological states may provide novel opportunities for pancreatic cancer targeted therapy and regenerative medicine.

Interplay between FGFR2b-induced autophagy and phagocytosis: role of PLCγ-mediated signalling

Signalling of the epithelial splicing variant of the fibroblast growth factor receptor 2 (FGFR2b) induces both autophagy and phagocytosis in human keratinocytes. Here, we investigated, in the cell model of HaCaT keratinocytes, whether the two processes might be related and the possible involvement of PLCγ signalling. Using fluorescence and electron microscopy, we demonstrated that the FGFR2b-induced phagocytosis and autophagy involve converging autophagosomal and phagosomal compartments. Moreover, the forced expression of FGFR2b signalling mutants and the use of specific inhibitors of FGFR2b substrates showed that the receptor-triggered autophagy requires PLCγ signalling, which in turn activates JNK1 via PKCδ. Finally, we found that in primary human keratinocytes derived from light or dark pigmented skin and expressing different levels of FGFR2b, the rate of phagocytosis and autophagy and the convergence of the two intracellular pathways are dependent on the level of receptor expression, suggesting that FGFR2b signalling would control in vivo the number of melanosomes in keratinocytes, determining skin pigmentation.

The function of heparan sulfate during branching morphogenesis

Branching morphogenesis is a fundamental process in the development of diverse epithelial organs such as the lung, kidney, liver, pancreas, prostate, salivary, lacrimal and mammary glands. A unifying theme during organogenesis is the importance of epithelial cell interactions with the extracellular matrix (ECM) and growth factors (GFs). The diverse developmental mechanisms giving rise to these epithelial organs involve many organ-specific GFs, but a unifying paradigm during organogenesis is the regulation of GF activity by heparan sulfates (HS) on the cell surface and in the ECM. This primarily involves the interactions of GFs with the sulfated side-chains of HS proteoglycans. HS is one of the most diverse biopolymers and modulates GF binding and signaling at the cell surface and in the ECM of all tissues. Here, we review what is known about how HS regulates branching morphogenesis of epithelial organs with emphasis on the developing salivary gland, which is a classic model to investigate epithelial-ECM interactions. We also address the structure, biosynthesis, turnover and function of HS during organogenesis. Understanding the regulatory mechanisms that control HS dynamics may aid in the development of therapeutic interventions for diseases and novel strategies for tissue engineering and regenerative medicine.

Efficient regulation of branching morphogenesis via fibroblast growth factor receptor 2c in early-stage embryonic mouse salivary glands

Salivary gland (SG) defects have a wide range of health implications, including xerostomia, bacterial infections, and oral health issues. Branching morphogenesis is critical for SG development. A clear understanding of the mechanisms underlying this process will accelerate SG regeneration studies. Fibroblast growth factor receptor 2 (FGFR2) interacts with multiple fibroblast growth factors (FGFs), which promote development. FGFR2 consists of two isoforms, FGFR2b and FGFR2c. FGFR2b is critical for SG development, but little is known about the expression and function of FGFR2c. We investigated the expression of all FGFR family members in fetal SGs between embryonic day 12.5 (E12.5) and E18.5. Based on RT-PCR, we observed an increase in the expression of not only Fgfr2b, but also Fgfr2c in early-stage embryonic mouse SGs, suggesting that FGFR2c is related to SG development. The branch number decreased in response to exogenous FGF2 stimulation, and this effect was suppressed by a mouse anti-FGFR2c neutralizing antibody (NA) and siRNA targeting FGFR2c, whereas FGFR2b signaling was not inhibited. Moreover, the expression of marker genes related to EMT was induced by FGF2, and this expression was suppressed by the NA. These results suggested that branching morphogenesis in SGs is regulated by FGFR2c, in addition to FGFR2b. Interestingly, FGFR2c signaling also led to increased fgf10 expression, and this increase was suppressed by the NA. FGFR2c signaling regulates branching morphogenesis through the activation of FGFR2b signaling via increased FGF10 autocrine. These results provide new insight into the mechanisms by which crosstalk between FGFR2b and FGFR2c results in efficient branching morphogenesis.

Buttressing a balanced brain: Target-derived FGF signaling regulates excitatory/inhibitory tone and adult neurogenesis within the maturating hippocampal network

Brain development involves multiple levels of molecular coordination in forming a functional nervous system. The hippocampus is a brain area that is important for memory formation and spatial reasoning. During early postnatal development of the hippocampal circuit, Fibroblast growth factor 22 (FGF22) and FGF7 act to establish a balance of excitatory and inhibitory tone. Both FGFs are secreted from CA3 dendrites, acting on excitatory or inhibitory axon terminals formed onto CA3 dendrites, respectively. Mechanistically, FGF22 utilizes FGFR2b and FGFR1b to induce synaptic vesicle recruitment within axons of dentate granule cells (DGCs), and FGF7 utilizes FGFR2b to induce synaptic vesicle recruitment within interneuron axons. FGF signaling eventually induces gene expression in the presynaptic neurons; however, the effects of FGF22-induced gene expression within DGCs and FGF7-induced gene expression within interneurons in the context of a developing hippocampal circuit have yet to be explored. Here, we propose one hypothetical mechanism of FGF22-induced gene expression in controlling adult neurogenesis.

HPV16 E5 deregulates the autophagic process in human keratinocytes

Autophagy plays key roles during host defense against pathogens, but viruses have evolved strategies to block the process or to exploit it for replication and successful infection. The E5 oncoprotein of human papillomavirus type 16 (HPV16 E5) perturbs epithelial homeostasis down-regulating the expression of the keratinocyte growth factor receptor (KGFR/FGFR2b), whose signaling induces autophagy. Here we investigated the possible effects of 16E5 on autophagy in human keratinocytes expressing the viral protein. The 16E5 presence strongly inhibited the autophagic process, while forced expression and activation of KGFR counteracted this effect, demonstrating that the viral protein and the receptor exert opposite and interplaying roles not only on epithelial differentiation, but also in the control of autophagy. In W12 cells, silencing of the 16E5 gene in the context of the viral full length genome confirmed its role on autophagy inhibition. Finally, molecular approaches showed that the viral protein interferes with the transcriptional regulation of autophagy also through the impairment of p53 function, indicating that 16E5 uses parallel mechanisms for autophagy impairment. Overall our results further support the hypothesis that a transcriptional crosstalk among 16E5 and KGFR might be the crucial molecular driver of epithelial deregulation during early steps of HPV infection and transformation.

FGF10: A multifunctional mesenchymal-epithelial signaling growth factor in development, health, and disease

The FGF family comprises 22 members with diverse functions in development and health. FGF10 specifically activates FGFR2b in a paracrine manner with heparan sulfate as a co-factor. FGF10and FGFR2b are preferentially expressed in the mesenchyme and epithelium, respectively. FGF10 is a mesenchymal signaling molecule in the epithelium. FGF10 knockout mice die shortly after birth due to the complete absence of lungs as well as fore- and hindlimbs. FGF10 is also essential for the development of multiple organs. The phenotypes of Fgf10 knockout mice are very similar to those of FGFR2b knockout mice, indicating that FGF10 acts as a ligand that is specific to FGFR2b in mouse multi-organ development. FGF10 also plays roles in epithelial-mesenchymal transition, the repair of tissue injury, and embryonic stem cell differentiation. In humans, FGF10 loss-of-function mutations result in inherited diseases including aplasia of lacrimal and salivary gland, lacrimo-auriculo-dento-digital syndrome, and chronic obstructive pulmonary disease. FGF10 is also involved in the oncogenicity of pancreatic and breast cancers. Single nucleotide polymorphisms in FGF10 are also potential risk factors for limb deficiencies, cleft lip and palate, and extreme myopia. These findings indicate that FGF10 is a crucial paracrine signal from the mesenchyme to epithelium for development, health, and disease.

Palifermin for the protection and regeneration of epithelial tissues following injury: new findings in basic research and pre-clinical models

Keratinocyte growth factor (KGF) is a paracrine-acting epithelial mitogen produced by cells of mesenchymal origin, that plays an important role in protecting and repairing epithelial tissues. Pre-clinical data initially demonstrated that a recombinant truncated KGF (palifermin) could reduce gastrointestinal injury and mortality resulting from a variety of toxic exposures. Furthermore, the use of palifermin in patients with hematological malignancies reduced the incidence and duration of severe oral mucositis experienced after intensive chemoradiotherapy. Based upon these findings, as well as the observation that KGF receptors are expressed in many, if not all, epithelial tissues, pre-clinical studies have been conducted to determine the efficacy of palifermin in protecting different epithelial tissues from toxic injury in an attempt to model various clinical situations in which it might prove to be of benefit in limiting tissue damage. In this article, we review these studies to provide the pre-clinical background for clinical trials that are described in the accompanying article and the rationale for additional clinical applications of palifermin.

FGF7/KGF regulates autophagy in keratinocytes: A novel dual role in the induction of both assembly and turnover of autophagosomes

Autophagy is a degradative pathway through which cells overcome stressful conditions and rapidly change their phenotype during differentiation. Despite its protective role, when exacerbated, autophagy may lead to cell death. Several growth factors involved in cell survival and in preventing differentiation are able to inhibit autophagy. Here we investigated the autophagic role of FGF7/KGF, an important player in epithelial cell protection and differentiation. Biochemical and quantitative fluorescence approaches showed that FGF7 and its signaling induce autophagy in human keratinocytes and the use of specific inhibitors indicated that this effect is independent of the PI3K-AKT-MTOR pathway. The selective block of autophagosome-to-lysosome fusion clarified that FGF7 induces autophagy stimulating autophagosome formation. However, quantitative fluorescence approaches also indicated that, upon a prolonged autophagic stimulus, FGF7 is able to accelerate autophagosome turnover. Moreover, in differentiating keratinocytes, the use of the autophagic inhibitor 3-MA as well as the depletion of BECN1 and ATG5, 2 essential regulators of the process, counteracted the FGF7-induced increase of the differentiation marker KRT1/K1, suggesting that autophagy is required for the FGF7-mediated early differentiation. These results provide the first evidence of a role of FGF7 in the regulation of sequential steps of the autophagic process and strengthen the hypothesis of a direct interplay between autophagy and differentiation. On the other hand, the ability of FGF7 to accelerate autophagosome turnover, preventing their dangerous accumulation, is consistent with the well-established protective role played by the growth factor in epithelial cells.