CRISPR-Cas9 editing of the arginine-vasopressin V1a receptor produces paradoxical changes in social behavior in Syrian hamsters.

Studies from a variety of species indicate that arginine­vasopressin (AVP) and its V1a receptor (Avpr1a) play a critical role in the regulation of a range of social behaviors by their actions in the social behavior neural network. To further investigate the role of AVPRs in social behavior, we performed CRISPR-Cas9­mediated editing at the Avpr1a gene via pronuclear microinjections in Syrian hamsters (Mesocricetus auratus), a species used extensively in behavioral neuroendocrinology because they produce a rich suite of social behaviors. Using this germ-line gene-editing approach, we generated a stable line of hamsters with a frame-shift mutation in the Avpr1a gene resulting in the null expression of functional Avpr1as. Avpr1a knockout (KO) hamsters exhibited a complete lack of Avpr1a-specific autoradiographic binding throughout the brain, behavioral insensitivity to centrally administered AVP, and no pressor response to a peripherally injected Avpr1a-specific agonist, thus confirming the absence of functional Avpr1as in the brain and periphery. Contradictory to expectations, Avpr1a KO hamsters exhibited substantially higher levels of conspecific social communication (i.e., odor-stimulated flank marking) than their wild-type (WT) littermates. Furthermore, sex differences in aggression were absent, as both male and female KOs exhibited more aggression toward same-sex conspecifics than did their WT littermates. Taken together, these data emphasize the importance of comparative studies employing gene-editing approaches and suggest the startling possibility that Avpr1a-specific modulation of the social behavior neural network may be more inhibitory than permissive.

Type 2 Fibroblast Growth Factor Receptor Signaling Preserves Stemness and Prevents Differentiation of Prostate Stem Cells from the Basal Compartment.

Prostate stem cells (P-SCs) are capable of giving rise to all three lineages of prostate epithelial cells, which include basal, luminal, and neuroendocrine cells. Two types of P-SCs have been identified in both human and mouse adult prostates based on prostasphere or organoid cultures, cell lineage tracing, renal capsule implantation, and expression of luminal- and basal-specific proteins. The sphere-forming P-SCs are from the basal cell compartment that express P63, and are therefore designated as basal P-SCs (P-bSCs). Luminal P-SCs (P-lSCs) express luminal cytokeratins and Nkx3.1. Herein, we report that the type 2 FGF receptor (FGFR2) signaling axis is crucial for preserving stemness and preventing differentiation of P-bSCs. FGFR2 signaling mediated by FGFR substrate 2α (FRS2α) is indispensable for formation and maintenance of prostaspheres derived from P63(+) P-bSCs. Ablation of Fgfr2 in P63(+) cells in vitro causes the disintegration of prostaspheres. Ablation of Fgfr2 in vivo reduces the number of P63-expressing basal cells and enriches luminal cells. This suggests a basal stem cell-to-luminal cell differentiation. In addition, ablation of Fgfr2 in P63(+) cells causes defective postnatal development of the prostate. Therefore, the data indicate that FGFR2 signaling is critical for preserving stemness and preventing differentiation of P-bSCs.

Fibroblast growth factor signaling is essential for self-renewal of dental epithelial stem cells.

A constant supply of epithelial cells from dental epithelial stem cell (DESC) niches in the cervical loop (CL) enables mouse incisors to grow continuously throughout life. Elucidation of the cellular and molecular mechanisms underlying this unlimited growth potential is of broad interest for tooth regenerative therapies. Fibroblast growth factor (FGF) signaling is essential for the development of mouse incisors and for maintenance of the CL during prenatal development. However, how FGF signaling in DESCs controls the self-renewal and differentiation of the cells is not well understood. Herein, we report that FGF signaling is essential for self-renewal and the prevention of cell differentiation of DESCs in the CL as well as in DESC spheres. Inhibiting the FGF signaling pathway decreased proliferation and increased apoptosis of the cells in DESC spheres. Suppressing FGFR or its downstream signal transduction pathways diminished Lgr5-expressing cells in the CL and promoted cell differentiation both in DESC spheres and the CL. Furthermore, disruption of the FGF pathway abrogated Wnt signaling to promote Lgr5 expression in DESCs both in vitro and in vivo. This study sheds new light on understanding the mechanism by which the homeostasis, expansion, and differentiation of DESCs are regulated.

Identification of variables contributing to superovulation efficiency for production of transgenic prairie voles (Microtus ochrogaster).

BACKGROUND: The prairie vole (Microtus ochrogaster) is an emerging animal model for biomedical research because of its rich sociobehavioral repertoire. Recently, lentiviral transgenic technology has been used to introduce the gene encoding the green fluorescent protein (GFP) into the prairie vole germline. However, the efficiency of transgenesis in this species is limited by the inability to reliably produce large numbers of fertilized embryos. Here we examined several factors that may contribute to variability in superovulation success including, age and parentage of the female, and latency to mating after being placed with the male. METHODS: Females produced from 5 genetically distinct breeder lines were treated with 100 IU of pregnant mare serum gonadotrophin (PMSG) and immediately housed with a male separated by a perforated Plexiglas divider. Ovulation was induced 72 hr later with 30 IU of human chorionic gonadotropin (hCG) and 2 hrs later mating was allowed. RESULTS: Superovulation was most efficient in young females. For example, females aged 6-11 weeks produced more embryos (14 +/- 1.4 embryos) as compared to females aged 12-20 weeks (4 +/- 1.6 embryos). Females aged 4-5 weeks did not produce embryos. Further, females that mated within 15 min of male exposure produced significantly more embryos than those that did not. Interestingly, there was a significant effect of parentage. For example, 12 out of 12 females from one breeder pair superovulated (defined as producing 5 or more embryos), while only 2 out of 10 females for other lines superovulated. CONCLUSIONS: The results of this work suggest that age and genetic background of the female are the most important factors contributing to superovulation success and that latency to mating is a good predictor of the number of embryos to be recovered. Surprisingly we found that cohabitation with the male prior to mating is not necessary for the recovery of embryos but is necessary to recover oocytes. This information will dramatically reduce the number of females required to generate embryos for transgenesis in this species.

Epithelial SMYD5 Exaggerates IBD by Down-regulating Mitochondrial Functions via Post-Translational Control of PGC-1α Stability.

BACKGROUND & AIMS: The expression and role of methyltransferase SET and MYND domain-containing protein 5 (SMYD5) in inflammatory bowel disease (IBD) is completely unknown. Here, we investigated the role and underlying mechanism of epithelial SMYD5 in IBD pathogenesis and progression. METHODS: The expression levels of SMYD5 and the mitochondrial transcriptional coactivator peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) were examined by Western blot, immunofluorescence staining, and immunohistochemistry in intestinal epithelial cells (IECs) and in colon tissues from human IBD patients and colitic mice. Mice with Smyd5 conditional knockout in IECs and littermate controls were subjected to dextran sulfate sodium-induced colitis and the disease severity was assessed. SMYD5-regulated mitochondrial biogenesis was examined by quantitative reverse-transcription polymerase chain reaction and transmission electron microscopy, and the mitochondrial oxygen consumption rate was measured in a Seahorse Analyzer system (Agilent, Santa Clara, CA). SMYD5 and PGC-1α interaction was determined by co-immunoprecipitation assay. PGC-1α degradation and turnover (half-life) were analyzed by cycloheximide chase assay. SMYD5-mediated PGC-1α methylation was assessed via in vitro methylation assay followed by mass spectrometry for identification of methylated lysine residues. RESULTS: Up-regulated SMYD5 and down-regulated PGC-1α were observed in intestinal epithelia from IBD patients and colitic mice. Smyd5 depletion in IECs protected mice from dextran sulfate sodium-induced colitis. SMYD5 was critically involved in regulating mitochondrial biology such as mitochondrial biogenesis, respiration, and apoptosis. Mechanistically, SMYD5 regulates mitochondrial functions in a PGC-1α-dependent manner. Furthermore, SMYD5 mediates lysine methylation of PGC-1α and subsequently facilitates its ubiquitination and degradation. CONCLUSIONS: SMYD5 attenuates mitochondrial functions in IECs and promotes IBD progression by enhancing PGC-1α degradation in a methylation-dependent manner. Strategies to decrease SMYD5 expression and/or increase PGC-1α expression in IECs might be a promising therapeutic approach to treat IBD patients.

Metabolic regulator betaKlotho interacts with fibroblast growth factor receptor 4 (FGFR4) to induce apoptosis and inhibit tumor cell proliferation.

In organs involved in metabolic homeostasis, transmembrane α and ßklothos direct FGFR signaling to control of metabolic pathways. Coordinate expression of ßklotho and FGFR4 is a property of mature hepatocytes. Genetic deletion of FGFR4 or ßklotho in mice disrupts hepatic cholesterol/bile acid and lipid metabolism. The deletion of FGFR4 has no effect on the proliferative response of hepatocytes after liver injury. However, its absence results in accelerated progression of dimethynitrosamine-initiated hepatocellular carcinomas, indicating that FGFR4 suppresses hepatoma proliferation. The mechanism underlying the FGFR4-mediated hepatoma suppression has not been addressed. Here we show that ßklotho expression is more consistently down-regulated in human and mouse hepatomas than FGFR4. Co-expression and activation by either endocrine FGF19 or cellular FGF1 of the FGFR4 kinase in a complex with ßklotho restricts cell population growth through induction of apoptotic cell death in both hepatic and nonhepatic cells. The ßklotho-FGFR4 partnership caused a depression of activated AKT and mammalian target of rapamycin while activating ERK1/2 that may underlie the pro-apoptotic effect. Our results show that ßklotho not only interacts with heparan sulfate-FGFR4 to form a complex with high affinity for endocrine FGF19 but also impacts the quality of downstream signaling and biological end points activated by either FGF19 or canonical FGF1. Thus the same ßklotho-heparan sulfate-FGFR4 partnership that mediates endocrine control of hepatic metabolism plays a role in cellular homeostasis and hepatoma suppression through negative control of cell population growth mediated by pro-apoptotic signaling.

FGFR1 abrogates inhibitory effect of androgen receptor concurrent with induction of androgen-receptor variants in androgen receptor-negative prostate tumor epithelial cells.

BACKGROUND: Despite dramatic positive effects, there is evidence that the androgen receptor (AR) may negatively influence prostate tumor progression. Understanding the AR repressor function and how it is subverted is of particular importance in anti-androgen and AR intervention strategies. METHODS: AR, resident FGFR2IIIb, and ectopic FGFR1 were expressed by transfection in the AR-negative epithelial cell line DTE that predominates in cell culture of AR-positive androgen-responsive model Dunning R3327 rat prostate tumors. Androgen-responsiveness at transcription was measured by a luciferase reporter. Cell population growth rates were assessed by cell counts, DNA synthesis, and expression of cell cycle genes. AR variants (ARVs) were assessed by immunochemistry and nuclease protection of mRNA. RESULTS: Expression of AR inhibited cell population growth of AR-negative DTE cells at the G1-S phase of the cell cycle. Ectopic FGFR1, but not resident FGFR2IIIb abrogated the growth inhibitory effects of AR. Appearance of ARVs was coincident with co-expression of FGFR1 and AR and abrogation of the AR-dependent inhibition of cell growth. CONCLUSIONS: DTE cells may represent non-malignant AR-negative progenitors whose population is restricted by activation of AR in vivo. Ectopic expression of epithelial FGFR1, a common observation in tumors, overrides the inhibition of AR and thus may contribute to evolution of androgen and AR independent tumors. These results are consistent with the notion that some tumor cells are negatively restricted by AR and are unleased by androgen-deprivation or ectopic expression of FGFR1. ARV's may play a role in the bypass of the negative restrictions of AR.

Resident hepatocyte fibroblast growth factor receptor 4 limits hepatocarcinogenesis.

Fibroblast growth factor (FGF) family signaling mediates cell-to-cell communication in development and organ homeostasis in adults. Of the FGF receptor (FGFR) isotypes, FGFR4 is the sole resident isotype present in mature parenchymal hepatocytes. FGFR1 that is normally associated with activated nonparenchymal cells appears ectopically in hepatoma cells. Ectopic expression and chronic activity of FGFR1 in hepatocytes accelerates diethylnitrosamine (DEN)-initiated hepatocarcinogenesis by driving unrestrained cell proliferation and tumor angiogenesis. Hepatocyte FGFR4 mediates liver's role in systemic cholesterol/bile acid and lipid metabolism and affects proper hepatolobular restoration after damage without effect on cell proliferation. Here we ask whether FGFR4 plays a role in progression of hepatocellular carcinoma (HCC). We report that although spontaneous HCC was not detected in livers of FGFR4-deficient mice, the ablation of FGFR4 accelerated DEN-induced hepatocarcinogenesis. In contrast to FGFR1 that induced a strong mitogenic response and depressed rate of cell death in hepatoma cells, FGFR4 failed to induce a mitogenic response and increased the rate of cell death. FGFR1 but not FGFR4 induced cyclin D1 and repressed p27 expression. Analysis of activation of Erk, JNK, and PI3K-related AKT signaling pathways indicated that in contrast to FGFR1, FGFR4 failed to sustain Erk activation and did not activate AKT. These differences may underlie the opposing effects of FGFR1 and FGFR4. These results suggest that in contrast to ectopic FGFR1 that is a strong promoter of hepatoma, resident FGFR4 that mediates differentiated hepatocyte metabolic functions also serves to suppress hepatoma progression.

Ectopic activity of fibroblast growth factor receptor 1 in hepatocytes accelerates hepatocarcinogenesis by driving proliferation and vascular endothelial growth factor-induced angiogenesis.

Fibroblast growth factor (FGF) signaling mediates cell-to-cell communication in development and organ homeostasis in adults. Of the four FGF receptor (FGFR) tyrosine kinases, only FGFR4 is expressed in mature hepatocytes. Although FGFR1 is expressed by hepatic cell progenitors and adult nonparenchymal cells, ectopic expression is commonly observed in hepatoma cells. Here, we determined whether ectopic FGFR1 is a cause or consequence of hepatocellular carcinoma by targeting a constitutively active human FGFR1 to mouse hepatocytes. Livers of transgenic mice exhibited accelerated regeneration after partial hepatectomy but no signs of neoplastic or preneoplastic abnormalities for up to 18 months. However, in diethylnitrosamine-treated mice, the chronic FGFR1 activity promoted an incidence of 44% adenomas at 4 months and 38% hepatocellular carcinoma at 8 months. No adenoma or hepatocellular carcinoma was observed in diethylnitrosamine-treated wild-type (WT) livers at 4 or 8 months, respectively. At 10 and 12 months, tumor-bearing livers in transgenic mice were twice the size of those in WT animals. Isolated hepatoma cells from the transgenic tumors exhibited a growth advantage in culture. Advanced hepatocellular carcinoma in the transgenic livers exhibited a reduced rate of necrosis. This was accompanied by a mean microvessel density of 2.7 times that of WT tumors and a markedly higher level of vascular endothelial growth factor. In cooperation with an initiator, the persistent activity of ectopic FGFR1 in hepatocytes is a strong promoter of hepatocellular carcinoma by driving cell proliferation at early stages and promoting neoangiogenesis at late stages of progression.

Stromal cell heterogeneity in fibroblast growth factor-mediated stromal-epithelial cell cross-talk in premalignant prostate tumors.

Homeostasis of normal prostate and two-compartment nonmalignant prostate tumors is dependent on two-way communication between epithelial and stromal compartments. Independence of epithelial cells on controlling instructions from stroma is a hallmark of extremely malignant epithelial cell tumors. To better understand the evolution of stromal independence during malignant progression, we performed a clonal analysis of stromal cells derived from a well-defined model of two-way stromal-epithelial cell communication that loses response to stroma during prostate tumor progression. Directionally specific signaling from stroma to epithelium contributes to homeostasis between the two compartments. Stromal cells were characterized in respect to expression and activity of isotypes of the fibroblast growth factor (FGF) family of ligands and receptors in addition to morphology and cytoskeletal markers. One stromal subtype (DTS1) exhibited a fibroblast-like morphology and did not display smooth muscle cell (SMC) alpha-actin. The other (DTS2) exhibited SMC alpha-actin and an SMC-like morphology in vitro. Both subtypes expressed FGF7 and equally low levels of FGFR2IIIc mRNA, whereas fibroblast growth factor receptor (FGFR) 1 predominated in DTS1 cells. DTS1 cells also expressed FGF10 and no detectable FGFR3, whereas the absence of FGF10 and presence of FGFR3 distinguished DTS2 cells. Epithelial cell-derived FGF9 bound to FGFR and stimulated growth of specifically FGFR3-positive DTS2 cells, not the FGFR3-negative DTS1 cells. These results demonstrate stromal cell heterogeneity in signal reception of FGF from epithelium. This correlated with potential heterogeneity in the response back to epithelial cells. Epithelium-dependent control of a stromal cell phenotype within a tumor may be a determinant of whether tumors remain in nonmalignant homeostasis or progress to malignancy.

Directionally specific paracrine communication mediated by epithelial FGF9 to stromal FGFR3 in two-compartment premalignant prostate tumors.

Tissue homeostasis in normal prostate and two-compartment nonmalignant prostate tumors depends on harmonious two-way communications between epithelial and stromal compartments. Within the fibroblast growth factor (FGF) family, signaling to an epithelial cell-specific FGF receptor (FGFR) 2IIIb-heparan sulfate complex from stromal-specific FGF7 and FGF10 delivers directionally specific instruction from stroma to epithelium without autocrine interference. Using a two-compartment transplantable prostate tumor model in which survival of stromal cells in vivo depends on epithelial cells, we show that signaling from epithelial FGF9 to stromal FGFR3 potentially mediates epithelial-to-stromal communication that also is directionally specific. FGF9 mRNA was expressed exclusively in the epithelial cells derived from well-differentiated, two-compartment Dunning R3327 rat prostate tumors. In contrast, FGFR3 was expressed at functionally significant levels only in the derived stromal cells. Competition binding and immunoprecipitation assays revealed that FGF9 only bound to an FGFR on the stromal cells. FGF9 also failed to covalently cross-link to clonal lines of stromal cells devoid of FGFR3 that expressed FGFR1 and FGFR2IIIc. Furthermore, FGF9 specifically stimulated DNA synthesis in stromal cells expressing FGFR3. These results demonstrate a directionally specific paracrine signaling from epithelial FGF9 and stromal FGFR3. Similar to the FGF7/FGF10 to FGFR2IIIb signaling from the stroma to the epithelium, the directional specificity from epithelium to stroma appears set by a combination of cell-specific expression of isoforms and cell-context specificity of FGFR isotypes for FGF.

Cooperation between ectopic FGFR1 and depression of FGFR2 in induction of prostatic intraepithelial neoplasia in the mouse prostate.

Disruption of the regulatory communication from the stroma to the epithelium mediated by the FGF7/10-FGFR2 signaling axis in the prostate and expression of ectopic FGFR1 in prostatic epithelial cells often correlate with prostate cancer progression both in human and in experimental animals. Ectopic expression of constitutively active FGFR1 mutant (caFGFR1) at low levels in prostate epithelial cells induces low- to intermediate-grade prostatic intraepithelial neoplasia (PIN) within 6-8 months and high-grade PIN in 20-25 months. Depression of the FGFR2 signaling in the prostate also disturbs homeostasis in the prostate and induces prostate hyperplasia. To study whether PIN lesions induced by the caFGFR1 were expression-level dependent, and whether expression of the caFGFR1 and depression of the FGFR2 signaling in the prostate synergistically disturbed prostate homeostasis, we generated two new strains of ARR2PBi-caFGFR1 transgenic mice, which highly expressed caFGFR1 in prostatic epithelial cells. The mice were crossed with KDNR mice to generate ARR2PBi-caFGFR1/KDNR bigenic mice. The ARR2PBi-caFGFR1 mice developed high-grade PIN within 8 months, which was significantly faster than the mice expressing caFGFR1 at low levels. In addition, depression of the FGFR2 signaling clearly promoted perturbation of cellular homeostasis induced by the caFGFR1. The results demonstrated that the PIN development in caFGFR1 transgenic mice was caFGFR1 dosage-dependent, and indicated that the ectopic FGFR1 and the resident FGFR2 in epithelial cells had opposite impacts on intercompartmental homeostasis in the prostate. The bigenic mice provide a model with cooperative aberrations in the fibroblast growth factor signaling axis for evaluation of tumor-initiating events in prostate tumorigenesis.

Preclinical Modeling of KIF5B-RET Fusion Lung Adenocarcinoma.

RET fusions have been found in lung adenocarcinoma, of which KIF5B-RET is the most prevalent. We established inducible KIF5B-RET transgenic mice and KIF5B-RET-dependent cell lines for preclinical modeling of KIF5B-RET-associated lung adenocarcinoma. Doxycycline-induced CCSP-rtTA/tetO-KIF5B-RET transgenic mice developed invasive lung adenocarcinoma with desmoplastic reaction. Tumors regressed upon suppression of KIF5B-RET expression. By culturing KIF5B-RET-dependent BaF3 (B/KR) cells with increasing concentrations of cabozantinib or vandetanib, we identified cabozantinib-resistant RETV804L mutation and vandetanib-resistant-RETG810A mutation. Among cabozantinib, lenvatinib, ponatinib, and vandetanib, ponatinib was identified as the most potent inhibitor against KIF5B-RET and its drug-resistant mutants. Interestingly, the vandetanib-resistant KIF5B-RETG810A mutant displayed gain-of-sensitivity (GOS) to ponatinib and lenvatinib. Treatment of doxycycline-induced CCSP-rtTA/tetO-KIF5B-RET bitransgenic mice with ponatinib effectively induced tumor regression. These results indicate that KIF5B-RET-associated lung tumors are addicted to the fusion oncogene and ponatinib is the most effective inhibitor for targeting KIF5B-RET in lung adenocarcinoma. Moreover, this study finds a novel vandetanib-resistant RETG810A mutation and identifies lenvatinib and ponatinib as the secondary drugs to overcome this vandetanib resistance mechanism. Mol Cancer Ther; 15(10); 2521-9. ©2016 AACR.

Overexpression of FGF9 in prostate epithelial cells augments reactive stroma formation and promotes prostate cancer progression.

Bone metastasis is the major cause of morbidity and mortality of prostate cancer (PCa). Fibroblast growth factor 9 (FGF9) has been reported to promote PCa bone metastasis. However, the mechanism by which overexpression of FGF9 promotes PCa progression and metastasis is still unknown. Herein, we report that transgenic mice forced to express FGF9 in prostate epithelial cells (F9TG) developed high grade prostatic intraepithelial neoplasia (PIN) in an expression level- and time-dependent manner. Moreover, FGF9/TRAMP bigenic mice (F9TRAMP) grew advanced PCa earlier and had higher frequencies of metastasis than TRAMP littermates. We observed tumor microenvironmental changes including hypercellularity and hyperproliferation in the stromal compartment of F9TG and F9TRAMP mice. Expression of TGFß1, a key signaling molecule overexpressed in reactive stroma, was increased in F9TG and F9TRAMP prostates. Both in vivo and in vitro data indicated that FGF9 promoted TGFß1 expression via increasing cJun-mediated signaling. Moreover, in silico analyses showed that the expression level of FGF9 was positively associated with expression of TGFß1 and its downstream signaling molecules in human prostate cancers. Collectively, our data demonstrated that overexpressing FGF9 in PCa cells augmented the formation of reactive stroma and promoted PCa initiation and progression.

Hepatocyte FRS2α is essential for the endocrine fibroblast growth factor to limit the amplitude of bile acid production induced by prandial activity.

In addition to being positively regulated by prandial activity, bile acid production is also negatively controlled by the endocrine fibroblast growth factor 19 (FGF19) or the mouse ortholog FGF15 from the ileum that represses hepatic cholesterol 7 α-hydroxylase (Cyp7a1) expression through activating FGF receptor four (FGFR4). However, how these two regulatory mechanisms interplay to control bile acid homeostasis in the body and the downstream pathways by which FGFR4 regulates Cyp7a1 expression are not fully understood. Here we report that hepatocyte FGFR substrate 2α (FRS2α), a scaffold protein essential for canonical FGFRs to activate the ERK and AKT pathways, was required for the regulation of bile acid production by the FGF15/19-FGFR4 signaling axis. This occurred through limiting the extent of increases in Cyp7a1 expression induced by prandial activity. Excess FGFR4 kinase activity reduced the amplitude of the increase whereas a lack of FGFR4 augmented the increase of Cyp7a1 expression in the liver. Ablation of Frs2α alleles in hepatocytes abrogated the regulation of Cyp7a1 expression by FGFR4. Together, the results demonstrate that FRS2α-mediated pathways are essential for the FGF15/FGF19-FGFR4 signaling axis to control bile acid homeostasis.

Deficiency of metabolic regulator FGFR4 delays breast cancer progression through systemic and microenvironmental metabolic alterations.

BACKGROUND: Endocrine FGF21 and FGF19 target adipocytes and hepatocytes through betaKlotho (KLB) and FGFR tyrosine kinases effecting glucose, lipid and energy metabolism. Both factors alleviate obesity and metabolic abnormalities which are contributing factors to breast tumor progression. Genomic manipulation of hepatic FGFR4 has uncovered roles of endocrine FGF signaling in both metabolic and cellular homeostasis. Here we determined whether systemic and microenvironmental metabolic alterations caused by the FGFR4 deficiency affect tumorigenesis in breast where FGFR4 is negligible. Breast tumors were induced in the bigenic mice with ablation of FGFR4 and overexpression of TGFα that activates Her2 in the ductal and lobular epithelium surrounded by adipocytes. Mammary tumorigenesis and alterations in systemic and breast microenvironmental metabolic parameters and regulatory pathways were analyzed. RESULTS: Ablation of FGFR4 had no effect on cellular homeostasis and Her2 activity of normal breast tissue. However, the absence of FGFR4 reduced TGFα-driven breast tumor incidence and progression and improved host survival. Notable increases in hepatic and serum FGF21, ileal FGF15/19, adiponectin and adipsin, and decreases in systemic Fetuin A, IGF-1, IGFBP-1, RBP4 and TIMP1 were observed. The ablation affected adipogenesis and secretory function of adipocytes as well as lipogenesis, glycolysis and energy homeostasis associated with the functions of mitochondria, ER and peroxisomes in the breast and tumor foci. Treatment with a chemical inhibitor of NAMPT involved in the pathways inhibited the growth and survival of breast tumor cells and tumor-initiating cell-containing spheres. The FGFR4 ablation also caused elevation of inflammatory factors in the breast. CONCLUSIONS: Although the primary role of FGFR4 in metabolism occurs in hepatocytes, its ablation results in a net inhibitory effect on mammary tumor progression. We suggest that the tumor-delaying effect of FGFR4 deficiency may be in large part due to elevated anti-obesogenic FGF21 that triggers tumor-suppressing signals from both peripheral and breast adipocytes. The predominant changes in metabolic pathways suggested roles of metabolic effects from both peripheral and breast adipocytes on metabolic reprogramming in breast epithelial cells that contribute to the suppression of tumor progression. These results provide new insights into the contribution of systemic and microenvironmental metabolic effects controlled by endocrine FGF signaling to breast carcinogenesis.

Self-renewal and multilineage differentiation of mouse dental epithelial stem cells.

Understanding the cellular and molecular mechanisms underlying the self-renewal and differentiation of dental epithelial stem cells (DESCs) that support the unlimited growth potential of mouse incisors is critical for developing novel tooth regenerative therapies and unraveling the pathogenesis of odontogenic tumors. However, analysis of DESC properties and regulation has been limited by the lack of an in vitro assay system and well-documented DESC markers. Here, we describe an in vitro sphere culture system to isolate the DESCs from postnatal mouse incisor cervical loops (CLs) where the DESCs are thought to reside. The dissociated cells from CLs were able to expand and form spheres for multiple generations in the culture system. Lineage tracing indicated that DESC within the spheres were epithelial in origin as evident by lineage tracing. Upon stimulation, the sphere cells differentiated into cytokeratin 14- and amelogenin-expressing and mineral material-producing cells. Compared to the CL tissue, sphere cells expressed high levels of expression of Sca-1, CD49f (also designated as integrin α6), and CD44. Fluorescence-activated cell sorting (FACS) analyses of mouse incisor CL cells further showed that the CD49f(Bright) population was enriched in sphere-forming cells. In addition, the CD49f(Bright) population includes both slow-cycling and Lgr5(+) DESCs. The in vitro sphere culture system and identification of CD49f(Bright) as a DESC marker provide a novel platform for enriching DESCs, interrogating how maintenance, cell fate determination, and differentiation of DESCs are regulated, and developing tooth regenerative therapies.

Differential specificity of endocrine FGF19 and FGF21 to FGFR1 and FGFR4 in complex with KLB.

BACKGROUND: Recent studies suggest that betaKlotho (KLB) and endocrine FGF19 and FGF21 redirect FGFR signaling to regulation of metabolic homeostasis and suppression of obesity and diabetes. However, the identity of the predominant metabolic tissue in which a major FGFR-KLB resides that critically mediates the differential actions and metabolism effects of FGF19 and FGF21 remain unclear. METHODOLOGY/PRINCIPAL FINDINGS: We determined the receptor and tissue specificity of FGF21 in comparison to FGF19 by using direct, sensitive and quantitative binding kinetics, and downstream signal transduction and expression of early response gene upon administration of FGF19 and FGF21 in mice. We found that FGF21 binds FGFR1 with much higher affinity than FGFR4 in presence of KLB; while FGF19 binds both FGFR1 and FGFR4 in presence of KLB with comparable affinity. The interaction of FGF21 with FGFR4-KLB is very weak even at high concentration and could be negligible at physiological concentration. Both FGF19 and FGF21 but not FGF1 exhibit binding affinity to KLB. The binding of FGF1 is dependent on where FGFRs are present. Both FGF19 and FGF21 are unable to displace the FGF1 binding, and conversely FGF1 cannot displace FGF19 and FGF21 binding. These results indicate that KLB is an indispensable mediator for the binding of FGF19 and FGF21 to FGFRs that is not required for FGF1. Although FGF19 can predominantly activate the responses of the liver and to a less extent the adipose tissue, FGF21 can do so significantly only in the adipose tissue and adipocytes. Among several metabolic and endocrine tissues, the response of adipose tissue to FGF21 is predominant, and can be blunted by the ablation of KLB or FGFR1. CONCLUSIONS: Our results indicate that unlike FGF19, FGF21 is unable to bind FGFR4-KLB complex with affinity comparable to FGFR1-KLB, and therefore, at physiological concentration less likely to directly and significantly target the liver where FGFR4-KLB predominantly resides. However, both FGF21 and FGF19 have the potential to activate responses of primarily the adipose tissue where FGFR1-KLB resides.

Control of lipid metabolism by adipocyte FGFR1-mediated adipohepatic communication during hepatic stress.

BACKGROUND: Endocrine FGF19 and FGF21 exert their effects on metabolic homeostasis through fibroblast growth factor receptor (FGFR) and co-factor betaKlotho (KLB). Ileal FGF19 regulates bile acid metabolism through specifically FGFR4-KLB in hepatocytes where FGFR1 is not significant. Both FGF19 and FGF21 activate FGFR1-KLB whose function predominates in adipocytes. Recent studies using administration of FGF19 and FGF21 and genetic ablation of KLB or adipocyte FGFR1 indicate that FGFR1-KLB mediates the response of adipocytes to both FGF21 and FGF19. Here we show that adipose FGFR1 regulates lipid metabolism through direct effect on adipose tissue and indirect effects on liver under starvation conditions that cause hepatic stress. METHODS: We employed adipocyte-specific ablations of FGFR1 and FGFR2 genes in mice, and analyzed metabolic consequences in adipose tissue, liver and systemic parameters under normal, fasting and starvation conditions. RESULTS: Under normal conditions, the ablation of adipose FGFR1 had little effect on adipocytes, but caused shifts in expression of hepatic genes involved in lipid metabolism. Starvation conditions precipitated a concurrent elevation of serum triglycerides and non-esterified fatty acids, and increased hepatic steatosis and adipose lipolysis in the FGFR1-deficient mice. Little effect on glucose or ketone bodies due to the FGFR1 deficiency was observed. CONCLUSIONS: Our results suggest an adipocyte-hepatocyte communication network mediated by adipocyte FGFR1 that concurrently dampens hepatic lipogenesis and adipocyte lipolysis. We propose that this serves overall to mete out and extend lipid reserves for neural fuels (glucose and ketone bodies), while at the same time governing extent of hepatosteatosis during metabolic extremes and other conditions causing hepatic stress.

FGFR3-expressing smooth muscle-like stromal cells differentiate in response to FGFR2IIIb-expressing prostate tumor cells and delay tumor progression.

Evolution of unresponsiveness to homeostasis-promoting signals from the microenvironment is a hallmark of malignant tumor cells. In Dunning R3327 model rat prostate tumors that are comprised of distinct stromal and epithelial compartments, progression from non-malignant, androgen-responsive tumors to malignancy is characterized by loss of compartmentation coincident with a loss of resident epithelial cell FGFR2IIIb that receives instructive signals from stromal FGF7 and FGF10. Restoration of FGFR2IIIb to malignant tumor cells restores responsiveness to stromal cells, restores distinct stromal and epithelial compartments, and retards malignant progression. Cultured stromal cells from two-compartment tumors are comprised of smooth muscle α-actin-positive cells that express predominantly FGFR3 and fibroblast-like cells devoid of α-actin and FGFR3. Here, we show that it is primarily the smooth muscle cell-like α-actin-expressing stromal cells that survive, morphologically differentiate, and delay tumor incidence and size in the presence of malignant cells in which FGFR2IIIb has been restored. Expression of FGFR3 by transfection in the fibroblast-like stromal cells conferred ability to respond similar to the smooth muscle cell-like stromal cells in which FGFR3 is normally resident. These results highlight the importance of the two-way communication back and forth between stroma and epithelium that is mediated by signaling within the FGFR family during progression to malignancy.