Knockdown of PTK7 Reduces the Oncogenic Potential of Breast Cancer Cells by Impeding Receptor Tyrosine Kinase Signaling.

Protein tyrosine kinase 7 (PTK7), a catalytically defective receptor tyrosine kinase (RTK), is often upregulated in various cancers. This study aimed to validate PTK7 as a target for breast cancer (BC) and investigate its oncogenic signaling mechanism. BC tissue analysis showed significantly elevated PTK7 mRNA levels, especially in refractory triple-negative breast cancer (TNBC) tissues, compared with normal controls. Similarly, BC cell lines exhibited increased PTK7 expression. Knockdown of PTK7 inhibited the proliferation of T-47D and MCF-7 hormone-receptor-positive BC cell-lines and of HCC1187, MDA-MB-231, MDA-MB-436, and MDA-MB-453 TNBC cells. PTK7 knockdown also inhibited the adhesion, migration, and invasion of MDA-MB-231, MDA-MB-436, and MDA-MB-453 cells, and reduced the phosphorylation levels of crucial oncogenic regulators including extracellular signal-regulated kinase (ERK), Akt, and focal adhesion kinase (FAK). Furthermore, PTK7 interacts with fibroblast growth factor receptor 1 (FGFR1) and epidermal growth factor receptor (EGFR) expressed in MDA-MB-231 cells. Knockdown of PTK7 decreased the growth-factor-induced phosphorylation of FGFR1 and EGFR in MDA-MB-231 cells, indicating its association with RTK activation. In conclusion, PTK7 plays a significant role in oncogenic signal transduction by enhancing FGFR1 and EGFR activation, influencing BC tumorigenesis and metastasis. Hence, PTK7 represents a potential candidate for targeted BC therapy, including TNBC.

Anti-PTK7 Monoclonal Antibodies Exhibit Anti-Tumor Activity at the Cellular Level and in Mouse Xenograft Models of Esophageal Squamous Cell Carcinoma.

PTK7 is a catalytically defective receptor protein tyrosine kinase upregulated in various cancers, including esophageal squamous cell carcinoma (ESCC). In previous studies, we observed a positive correlation between PTK7 expression levels and tumorigenicity in various ESCC cell lines and xenograft mice with ESCC KYSE-30 cells. In this study, we analyzed the effects of anti-PTK7 monoclonal antibodies (mAbs) on the tumorigenic activity in KYSE-30 cells and in mouse xenograft models. PTK7 mAb-32 and mAb-43 bind with a high affinity to the extracellular domain of PTK7. PTK7 mAbs significantly reduced three-dimensional cell proliferation, adhesion, wound healing, and migration. PTK7 mAbs also reduce chemotactic invasiveness by decreasing MMP-9 secretion. PTK7 mAbs decreased actin cytoskeleton levels in the cortical region of KYSE-30 cells. PTK7 mAbs reduced the phosphorylation of ERK, SRC, and FAK. In a mouse xenograft model of ESCC using KYSE-30 cells, PTK7 mAbs reduced tumor growth in terms of volume, weight, and the number of Ki-67-positive cells. These results demonstrated that PTK7 mAbs can inhibit the tumorigenicity of ESCC at the cellular level and in vivo by blocking the function of PTK7. Considering the anticancer activities of PTK7 mAbs, we propose that PTK7 mAbs can be used in an effective treatment strategy for PTK7-positive malignancies, such as ESCC.

Anti-PTK7 Monoclonal Antibodies Inhibit Angiogenesis by Suppressing PTK7 Function.

PTK7, a catalytically defective receptor protein tyrosine kinase, promotes angiogenesis by activating KDR through direct interaction and induction of KDR oligomerization. This study developed anti-PTK7 monoclonal antibodies (mAbs) to regulate angiogenesis by inhibiting PTK7 function. The effect of anti-PTK7 mAbs on vascular endothelial growth factor (VEGF)-induced angiogenic phenotypes in human umbilical vascular endothelial cells (HUVECs) was examined. Analysis of mAb binding with PTK7 deletion mutants revealed that mAb-43 and mAb-52 recognize immunoglobulin (Ig) domain 2 of PTK7, whereas mAb-32 and mAb-50 recognize Ig domains 6-7. Anti-PTK7 mAbs inhibited VEGF-induced adhesion and wound healing in HUVECs. mAb-32, mAb-43, and mAb-52 dose-dependently mitigated VEGF-induced migration and invasion in HUVECs without exerting cytotoxic effects. Additionally, mAb-32, mAb-43, and mAb-52 inhibited capillary-like tube formation in HUVECs, and mAb-32 and mAb-43 suppressed angiogenesis ex vivo (aortic ring assay) and in vivo (Matrigel plug assay). Furthermore, mAb-32 and mAb-43 downregulated VEGF-induced KDR activation and downstream signaling and inhibited PTK7-KDR interaction in PTK7-overexpressing and KDR-overexpressing HEK293 cells. Thus, anti-PTK7 mAbs inhibit angiogenic phenotypes by blocking PTK7-KDR interaction. These findings indicate that anti-PTK7 mAbs that neutralize PTK7 function can alleviate impaired angiogenesis-associated pathological conditions, such as cancer metastasis.

Synthetic PPAR Agonist DTMB Alleviates Alzheimer's Disease Pathology by Inhibition of Chronic Microglial Inflammation in 5xFAD Mice.

Abnormal productions of amyloid beta (Aß) plaque and chronic neuroinflammation are commonly observed in the brain of patients with Alzheimer's disease, and both of which induce neuronal cell death, loss of memory, and cognitive dysfunction. However, many of the drugs targeting the production of Aß peptides have been unsuccessful in treating Alzheimer's disease. In this study, we identified synthetic novel peroxisome proliferator-activating receptor (PPAR) agonist, DTMB, which can ameliorate the chronic inflammation and Aß pathological progression of Alzheimer's disease. We discovered that DTMB attenuated the proinflammatory cytokine production of microglia by reducing the protein level of NF-κB. DTMB also improved the learning and memory defects and reduced the amount of Aß plaque in the brain of 5xFAD mice. This reduction in Aß pathology was attributed to the changes in gliosis and chronic inflammation level. Additionally, bulk RNA-sequencing showed that genes related to inflammation and cognitive function were changed in the hippocampus and cortex of DTMB-treated mice. Our findings demonstrate that DTMB has the potential to be a novel therapeutic agent for Alzheimer's disease.

Analysis of Major Bacteria and Diversity of Surface Soil to Discover Biomarkers Related to Soil Health.

The discovery of biomarkers for assessing soil health requires the exploration of organisms that can explain the core functions of soil and identification of species with major roles in these functions. However, identifying specific keystone markers within the soil microbiota is challenging. Next-generation sequencing (NGS)-based molecular-biological methods have revealed information on soil biodiversity; however, whether this biodiversity is related to soil health remains unclear. In this study, we performed NGS on grassland surface soil to compare the prokaryotic and eukaryotic genetic diversity to determine the chemical soil quality and examined markers associated with soil health. Microorganisms associated with the nitrogen cycle, bioremediation, plant pathogenicity, antibiotic production, and material degradation showed potential for use as markers. To propose a framework for soil health assessment, we not only used traditional indicators, such as chemical and physical measures, but also assessed metagenomics data of soil by land use to identify the major factors influencing the microbial structure in soil. Moreover, major keystone species were identified. Furthermore, the microbial genetic diversity of generally healthy surface soil, such as forests, farmland, and parks, was determined. These findings provide basic data for exploring soil health-related biomarkers.

PTK7, a Catalytically Inactive Receptor Tyrosine Kinase, Increases Oncogenic Phenotypes in Xenograft Tumors of Esophageal Squamous Cell Carcinoma KYSE-30 Cells.

Protein tyrosine kinase 7 (PTK7), a catalytically defective receptor protein tyrosine kinase, is upregulated in tumor tissues and cell lines of esophageal squamous cell carcinoma (ESCC). We showed that PTK7 plays an oncogenic role in various ESCC cell lines. However, its role as an oncogene has not been demonstrated in vivo. Here, we examined the influence of PTK7 on the tumorigenic potential of ESCC KYSE-30 cells, which are known to establish xenograft tumors. Overexpression of PTK7 enhanced the proliferation, adhesion, wound healing, and migration of KYSE-30 cells, and these effects were reversed by the knockdown of PTK7. PTK7 overexpression and knockdown, respectively, increased and decreased the tyrosine phosphorylation of cellular proteins and the phosphorylation of ERK, AKT, and FAK, which are important for cell proliferation, survival, adhesion, and migration. Additionally, PTK7 overexpression and silencing, respectively, increased and decreased the weight, volume, and number of Ki-67-positive proliferating cells in xenograft tumors of KYSE-30 cells. Therefore, we propose that PTK7 plays an important role in the tumorigenesis of ESCC cells in vivo and is a potential therapeutic target for ESCC.

The catalytically defective receptor protein tyrosine kinase EphA10 promotes tumorigenesis in pancreatic cancer cells.

EphA10 (erythropoietin-producing hepatocellular carcinoma receptor A10) is a catalytically defective receptor protein tyrosine kinase in the ephrin receptor family. Although EphA10 is involved in the malignancy of some types of cancer, its role as an oncogene has not been extensively studied. Here, we investigated the influence of EphA10 on the tumorigenic potential of pancreatic cancer cells. Analysis of expression profiles from The Cancer Genome Atlas confirmed that EphA10 was elevated and higher in tumor tissues than in normal tissues in some cancer types, including pancreatic cancer. EphA10 silencing reduced the proliferation, migration, and adhesion of MIA PaCa-2 and AsPC-1 pancreatic cancer cells. These effects were reversed by overexpression of EphA10 in MIA PaCa-2 cells. Importantly, overexpression and silencing of EphA10 respectively increased and decreased the weight, volume, and number of Ki-67-positive proliferating cells in MIA PaCa-2 xenograft tumors. Further, EphA10 expression was positively correlated with invasion and gelatin degradation in MIA PaCa-2 cells. Moreover, overexpression of EphA10 enhanced the expression and secretion of MMP-9 in MIA PaCa-2 cells and increased the expression of MMP-9 and the vascular density in xenograft tumors. Finally, expression of EphA10 increased the phosphorylation of ERK, JNK, AKT, FAK, and NF-κB, which are important for cell proliferation, survival, adhesion, migration, and invasion. Therefore, we suggest that EphA10 plays a pivotal role in the tumorigenesis of pancreatic epithelial cells and is a novel therapeutic target for pancreatic cancer.

High-Performance Photocatalytic Cementitious Materials Containing Synthetic Fibers and Shrinkage-Reducing Admixture.

This study aims to examine the mechanical, shrinkage and chemical properties of photocatalytic cementitious materials containing synthetic fibers and a shrinkage-reducing admixture (SRA). Two types of titanium dioxide (TiO2) powders and white Portland cement were considered along with ordinary Portland cement (OPC) as a control. Two types of synthetic fibers, i.e., glass and polyethylene (PE), and an SRA with contents varying from 0% to 3% were also considered. Using the TiO2 powders and the white Portland cement was effective in reducing the nitrogen oxides (NOx) concentration in cement composites. The use of PE fibers was more effective than glass fibers in terms of the mechanical properties, i.e., the compressive strength and tensile performance. With the addition of TiO2 powders and SRA or the replacement of OPC with white cement, the mechanical properties of the cement mortar generally deteriorated. The total shrinkage of the mortar could be reduced by incorporating the fibers at volume fractions greater than 1%, and the glass fiber was more effective than the PE fiber in this regard. The TiO2 powders had no significant impact on the shrinkage reduction of the cement mortar, whereas the SRA and the white Portland cement effectively reduced shrinkage. The addition of 3% SRA decreased the total shrinkage by 43%, while the replacement of the OPC with white cement resulted in a 20% reduction in the shrinkage.

Catalytically inactive receptor tyrosine kinase PTK7 activates FGFR1 independent of FGF.

Protein tyrosine kinase 7 (PTK7), a catalytically defective receptor protein tyrosine kinase (RPTK), plays an oncogenic role by activating an unidentified TKI-258 (dovitinib)-sensitive RPTK in esophageal squamous cell carcinoma (ESCC) cells. Here, we demonstrate that among TKI-258-sensitive RPTKs, fibroblast growth factor receptor (FGFR) 1 is significantly up-regulated in ESCC tissues and cell lines. We show that PTK7 colocalizes with FGFR1 and binds it via its extracellular domain in human embryonic kidney 293 and ESCC TE-10 cells. PTK7 knockdown not only reduced ligand-free and fibroblast growth factor (FGF)-induced phosphorylation of FGFR1 but also the interaction of signaling adaptor proteins with FGFR1 and activation of downstream signaling proteins in TE-10 cells. In addition, PTK7 knockdown reduced FGF-induced oncogenic phenotypes including proliferation, anchorage-independent colony formation, wound healing, and invasion in ESCC cells. Taken together, our data demonstrate that PTK7 binds and activates FGFR1 independent of FGF and thus increases oncogenicity of PTK7- and FGFR1-positive cancers such as ESCC.-Shin, W.-S., Lee, H. W., Lee, S.-T. Catalytically inactive receptor tyrosine kinase PTK7 activates FGFR1 independent of FGF.

Biphasic regulation of tumorigenesis by PTK7 expression level in esophageal squamous cell carcinoma.

Protein tyrosine kinase 7 (PTK7), also known as colon carcinoma kinase 4 (CCK-4), is a member of the catalytically defective receptor protein tyrosine kinase family and is upregulated in various cancers, where it is known to act as either an oncoprotein or a tumor suppressor. To understand the contrasting roles of PTK7 in tumorigenesis, we analyzed the tumorigenic characteristics of esophageal squamous cell carcinoma (ESCC) cells with low levels of endogenous PTK7 expression (TE-5 and TE-14 cells) and high levels of expression (TE-6 and TE-10 cells) after transfections with a PTK7 expression vector. PTK7 overexpression increased the proliferation of TE-5 and TE-14 cells but decreased the proliferation of TE-6 and TE-10 cells. In the ESCC cells, proliferation, migration, and invasion were initially increased and then decreased according to PTK7 expression levels, which were mirrored by initial increases and then decreases in the tyrosine phosphorylation of cellular proteins and phosphorylation of Src, Akt, and ERK. In ESCC patients included in The Cancer Genome Atlas database, those with higher PTK7 mRNA levels had a longer overall survival and lower relative risk than those with lower PTK7 mRNA levels. These results demonstrate that PTK7 biphasically regulates tumorigenesis in ESCC.

PTK6 Localized at the Plasma Membrane Promotes Cell Proliferation and MigratiOn Through Phosphorylation of Eps8.

Protein tyrosine kinase 6 (PTK6; also known as Brk) is closely related to the Src family kinases, but lacks a membrane-targeting myristoylation signal. Sublocalization of PTK6 at the plasma membrane enhances its oncogenic potential. To understand the mechanism(s) underlying the oncogenic property of plasma---membrane-associated PTK6, proteins phosphorylated by membrane-targeted myristoylated PTK6 (Myr-PTK6) were enriched and analyzed using a proteomics approach. Eps8 which was identified by this method is phosphorylated by Myr-PTK6 in HEK293 cells. Mouse Eps8 expressed in HEK293 cells is phosphorylated by Myr-PTK6 at residues Tyr497, Tyr524, and Tyr534. Compared to wild-type Eps8 (Eps8 WT), the phosphorylation-defective 3YF mutant (Eps8 3YF) reverts the increased proliferation, migration, and phosphorylation of ERK and FAK mediated by Eps8 WT in HEK293 cells overexpressing PTK6. PTK6 knockdown in T-47D breast cancer cells decreased EGF-induced phosphorylation of Eps8. Endogenous PTK6 phosphorylates ectopically expressed Eps8 WT, but not Eps8 3YF mutant, in EGF-stimulated T-47D cells. The EGF-induced Eps8 phosphorylation enhances activation of ERK and FAK, cell adhesion, and anchorage-independent colony formation in T-47D cells, but not in the PTK6-knokdown T-47D cells. These results indicate that plasma-membrane-associated PTK6 phosphorylates Eps8, which promotes cell proliferation, adhesion, and migration and, thus, tumorigenesis. J. Cell. Biochem. 118: 2887-2895, 2017. © 2017 Wiley Periodicals, Inc.

Catalytically defective receptor protein tyrosine kinase PTK7 enhances invasive phenotype by inducing MMP-9 through activation of AP-1 and NF-κB in esophageal squamous cell carcinoma cells.

Protein tyrosine kinase 7 (PTK7), a member of the catalytically defective receptor protein tyrosine kinase family, is upregulated in various cancers including esophageal squamous cell carcinoma (ESCC). Here, we have explored the molecular mechanism of PTK7-dependent invasiveness in ESCC cells. PTK7 knockdown reduced gelatin degradation and MMP-9 secretion in cultures of ESCC TE-10 cells, and showed reduced levels of MMP9 mRNA using real-time RT-PCR and luciferase reporter assays. PTK7 knockdown decreased not only phosphorylation of NF-κB, IκB, ERK, and JNK, but also nuclear localization of NF-κB and AP-1 consisting of c-Fos and c-Jun. Activation of AP-1 and NF-κB requires PTK7-mediated activation of tyrosine kinases, including Src. In addition, NF-κB activation by PTK7 involves the PI3K/Akt signaling pathway. PTK7-mediated upregulation of MMP9 was also observed in other ESCC cell lines and in three-dimensional cultures of TE-10 cells. Moreover, MMP-9 expression positively correlated with PTK7 expression in ESCC tumor tissue. These findings demonstrate that PTK7 upregulates MMP9 through activation of AP-1 and NF-κB and, thus increases invasive properties of ESCC cells.

Loop-Mediated Isothermal Amplification Targeting Actin DNA of Trichomonas vaginalis.

Trichomoniasis caused by Trichomonas vaginalis is a common sexually transmitted disease. Its association with several health problems, including preterm birth, pelvic inflammatory disease, cervical cancer, and transmission of human immunodeficiency virus, emphasizes the importance of improved access to early and accurate detection of T. vaginalis. In this study, a rapid and efficient loop-mediated isothermal amplification-based method for the detection of T. vaginalis was developed and validated, using vaginal swab specimens from subjects suspected to have trichomoniasis. The LAMP assay targeting the actin gene was highly sensitive with detection limits of 1 trichomonad and 1 pg of T. vaginalis DNA per reaction, and specifically amplified the target gene only from T. vaginalis. Validation of this assay showed that it had the highest sensitivity and better agreement with PCR (used as the gold standard) compared to microscopy and multiplex PCR. This study showed that the LAMP assay, targeting the actin gene, could be used to diagnose early infections of T. vaginalis. Thus, we have provided an alternative molecular diagnostic tool and a point-of-care test that may help to prevent trichomoniasis transmission and associated complications.

Prevalence of Trichomonas vaginalis in Women Visiting 2 Obstetrics and Gynecology Clinics in Daegu, South Korea.

This study explored epidemiological trends in trichomoniasis in Daegu, South Korea. Wet mount microscopy, PCR, and multiplex PCR were used to test for Trichomonas vaginalis in vaginal swab samples obtained from 621 women visiting 2 clinics in Daegu. Of the 621 women tested, microscopy detected T. vaginalis in 4 (0.6%) patients, PCR detected T. vaginalis in 19 (3.0%) patients, and multiplex PCR detected T. vaginalis in 12 (1.9%) patients. Testing via PCR demonstrated high sensitivity and high negative predictive value for T. vaginalis. Among the 19 women who tested positive for T. vaginalis according to PCR, 94.7% (18/19) reported vaginal signs and symptoms. Notably, more than 50% of T. vaginalis infections occurred in females younger than 30 years old, and 58% were unmarried. Multiplex PCR, which simultaneously detects pathogens from various sexually transmitted infections, revealed that 91.7% (11/12) of patients were infected with 2 or more pathogens. Mycoplasma hominis was the most prevalent co-infection pathogen with T. vaginalis, followed by Ureaplasma urealyticum and Chlamydia trachomatis. Our results indicate that PCR and multiplex PCR are the most sensitive tools for T. vaginalis diagnosis, rather than microscopy which has been routinely used to detect T. vaginalis infections in South Korea. Therefore, clinicians should take note of the high prevalence of T. vaginalis infections among adolescent and young women in order to prevent persistent infection and transmission of this disease.

Biosorption of Cu(II) by immobilized microalgae using silica: kinetic, equilibrium, and thermodynamic study.

Immobilized microalgae using silica (IMS) from Micractinium reisseri KGE33 was synthesized through a sol-gel reaction. Green algal waste biomass, the residue of M. reisseri KGE33 after oil extraction, was used as the biomaterial. The adsorption of Cu(II) on IMS was tested in batch experiments with varying algal doses, pH, contact times, initial Cu(II) concentrations, and temperatures. Three types of IMSs (IMS 14, 70, and 100) were synthesized according to different algal doses. The removal efficiency of Cu(II) in the aqueous phase was in the following order: IMS 14 (77.0%) < IMS 70 (83.3%) < IMS 100 (87.1%) at pH 5. The point of zero charge (PZC) value of IMS100 was 4.5, and the optimum pH for Cu(II) adsorption was 5. Equilibrium data were described using a Langmuir isotherm model. The Langmuir model maximum Cu(II) adsorption capacity (q m) increased with the algal dose in the following order: IMS 100 (1.710 mg g(-1)) > IMS 70 (1.548 mg g(-1)) > IMS 14 (1.282 mg g(-1)). The pseudo-second-order equation fitted the kinetics data well, and the value of the second-order rate constant increased with increasing algal dose. Gibbs free energies (ΔG°) were negative within the temperature range studied, which indicates that the adsorption process was spontaneous. The negative value of enthalpy (ΔH°) again indicates the exothermic nature of the adsorption process. In addition, SEM-energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS) analyses of the IMS surface reveal that the algal biomass on IMS is the main site for Cu(II) binding. This study shows that immobilized microalgae using silica, a synthesized biosorbent, can be used as a cost-effective sorbent for Cu(II) removal from the aqueous phase.

Biphasic effect of PTK7 on KDR activity in endothelial cells and angiogenesis.

Protein tyrosine kinase 7 (PTK7) is a member of the defective receptor protein tyrosine kinase family which lacks catalytic activity. Expression of PTK7 is increased in various cancers but its role in carcinogenesis is not well understood. We previously showed that disruption of PTK7 function suppresses VEGF-induced angiogenic phenotypes in HUVECs and mice. Here, we investigated molecular mechanisms for modulating VEGF-induced physiological effects by PTK7. Treatment with a high concentration of extracellular domain of PTK7 (soluble PTK7; sPTK7) or knockdown of PTK7 inhibited VEGF-induced phosphorylation of kinase insert domain receptor (KDR) but did not inhibit phosphorylation of fms-related tyrosine kinase 1 (FLT-1) in HUVECs. PTK7, more specifically sPTK7, interacted with KDR but not with FLT-1 in HUVECs and HEK293 cells. In vitro binding assay showed that sPTK7 formed oligomers with the extracellular domain of KDR (sKDR) up to an approximately 1:3 molar ratio, and vice versa. sPTK7 at lower molar ratios than sKDR enhanced the binding of VEGF to sKDR. At the same or higher molar ratios, it reduced the binding of VEGF to sKDR. Increasing concentrations of sPTK7 or increasing levels of PTK7 expression first increased and then decreased VEGF-induced KDR phosphorylation, migration, and capillary-like tube formation of HUVECs, as well as in vivo angiogenesis. Taken together, our data demonstrates that PTK7 regulates the activity of KDR biphasically by inducing oligomerization of KDR molecules at lower concentrations and by surrounding KDR molecules at higher concentrations.

Oncogenic role of protein tyrosine kinase 7 in esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC) is a common subtype of esophageal cancer that is particularly prevalent in East Asian countries. Our previous expression profile analysis showed that the gene encoding protein tyrosine kinase 7 (PTK7) is upregulated in ESCC tissues. Here, we aimed to validate PTK7 as a prognostic factor and a candidate target for molecular treatment of ESCC. Both RT-PCR and Western blot analysis of tissues from ESCC patients revealed that PTK7 was significantly upregulated in tumor tissue samples of ESCC. Immunohistochemical staining of PTK7 showed that increased expression of PTK7 was inversely correlated with overall survival (P = 0.021). In vitro knockdown of PTK7 inhibited proliferation, survival, wound healing, and invasion of ESCC cells. In addition, PTK7 knockdown decreased phosphorylation of Akt, Erk, and focal adhesion kinase (FAK), important determinants of cell proliferation, survival, and migration. Therefore, our findings suggest that PTK7 has potential as a prognostic marker for ESCC and might also be a candidate for targeted therapy in the treatment of ESCC.

The cytosolic domain of protein-tyrosine kinase 7 (PTK7), generated from sequential cleavage by a disintegrin and metalloprotease 17 (ADAM17) and γ-secretase, enhances cell proliferation and migration in colon cancer cells.

Protein-tyrosine kinase 7 (PTK7) is a member of the defective receptor protein-tyrosine kinases and is known to function as a regulator of planar cell polarity during development. Its expression is up-regulated in some cancers including colon carcinomas. A 100-kDa fragment of PTK7 was detected in the culture media from colon cancer cells and HEK293 cells. The shed fragment was named sPTK7-Ig1-7 because its molecular mass was very similar to that of the entire extracellular domain of PTK7 that contains immunoglobulin-like loops 1 to 7 (Ig1-7). The shedding of sPTK7-Ig1-7 was enhanced by treatment with phorbol 12-myristate 13-acetate. In addition to the sPTK7-Ig1-7 found in the culture medium, two C-terminal fragments of PTK7 were detected in the cell lysates: PTK7-CTF1, which includes a transmembrane segment and a cytoplasmic domain, and PTK7-CTF2, which lacks most of the transmembrane segment from PTK7-CTF1. Analysis of PTK7 processing in the presence of various protease inhibitors or after knockdown of potential proteases suggests that shedding of PTK7 into sPTK7-Ig1-7 and PTK7-CTF1 is catalyzed by ADAM17, and further cleavage of PTK7-CTF1 into PTK7-CTF2 is mediated by the γ-secretase complex. PTK7-CTF2 localizes to the nucleus and enhances proliferation, migration, and anchorage-independent colony formation. Our findings demonstrate a novel role for PTK7 in the tumorigenesis via generation of PTK7-CTF2 by sequential cleavage of ADAM17 and γ-secretase.

Protein tyrosine kinase 7 has a conserved role in Wnt/ß-catenin canonical signalling.

The receptor protein tyrosine kinase 7 (PTK7) was recently shown to participate in noncanonical Wnt/planar cell polarity signalling during mouse and frog embryonic development. In this study, we report that PTK7 interacts with ß-catenin in a yeast two-hybrid assay and mammalian cells. PTK7-deficient cells exhibit weakened ß-catenin/T-cell factor transcriptional activity on Wnt3a stimulation. Furthermore, Xenopus PTK7 is required for the formation of Spemann's organizer and for Siamois promoter activation, events that require ß-catenin transcriptional activity. Using epistatic assays, we demonstrate that PTK7 functions upstream from glycogen synthase kinase 3. Taken together, our data reveal a new and conserved role for PTK7 in the Wnt canonical signalling pathway.

The cell polarity PTK7 receptor acts as a modulator of the chemotherapeutic response in acute myeloid leukemia and impairs clinical outcome.

The pseudo tyrosine kinase receptor 7 (PTK7) is an orphan tyrosine kinase receptor assigned to the planar cell polarity pathway. It plays a major role during embryogenesis and epithelial tissue organization. Here we found that PTK7 is also expressed in normal myeloid progenitors and CD34(+) CD38(-) bone marrow cells in humans. We performed an immunophenotyping screen on more than 300 patients treated for hematologic malignancies. We demonstrated that PTK7 is expressed in acute myeloid leukemia (AML) and is mostly assigned to granulocytic lineage differentiation. Patients with PTK7-positive AML are more resistant to anthracycline-based frontline therapy with a significantly reduced leukemia-free survival in a multivariate analysis model. In vitro, expression of PTK7 in cultured leukemia cells promotes cell migration, cell survival, and resistance to anthracycline-induced apoptosis. The intracellular region of PTK7 is required for these effects. Furthermore, we efficiently sensitized primary AML blasts to anthracycline-mediated cell death using a recombinant soluble PTK7-Fc protein. We conclude that PTK7 is a planar cell polarity component expressed in the myeloid progenitor compartment that conveys promigratory and antiapoptotic signals into the cell and that represents an independent prognosis factor of survival in patients treated with induction chemotherapy.