Point Mutation at Single Tyrosine Residue of Novel Oncogene NOK Abrogates Tumorigenesis in Nude Mice

Therapeutic advances of targeting receptor tyrosine kinases in cancer

Receptor tyrosine kinases (RTKs), a category of transmembrane receptors, have gained significant clinical attention in oncology due to their central role in cancer pathogenesis. Genetic alterations, including mutations, amplifications, and overexpression of certain RTKs, are critical in creating environments conducive to tumor development. Following their discovery, extensive research has revealed how RTK dysregulation contributes to oncogenesis, with many cancer subtypes showing dependency on aberrant RTK signaling for their proliferation, survival and progression. These findings paved the way for targeted therapies that aim to inhibit crucial biological pathways in cancer. As a result, RTKs have emerged as primary targets in anticancer therapeutic development. Over the past two decades, this has led to the synthesis and clinical validation of numerous small molecule tyrosine kinase inhibitors (TKIs), now effectively utilized in treating various cancer types. In this manuscript we aim to provide a comprehensive understanding of the RTKs in the context of cancer. We explored the various alterations and overexpression of specific receptors across different malignancies, with special attention dedicated to the examination of current RTK inhibitors, highlighting their role as potential targeted therapies. By integrating the latest research findings and clinical evidence, we seek to elucidate the pivotal role of RTKs in cancer biology and the therapeutic efficacy of RTK inhibition with promising treatment outcomes.

The malignant transformation potential of the oncogene STYK1/NOK at early lymphocyte development in transgenic mice

B-cell Chronic Lymphocytic Leukemia (B-CLL) is a malignancy caused by the clonal expansion of mature B lymphocytes bearing a CD5+CD19+ (B1) phenotype. However, the origin of B-CLL remains controversial. We showed previously that STYK1/NOK transgenic mice develop a CLL-like disease. Using this model system in this study, we attempt to define the stage of CLL initiation. Here, we show that the phenotype of STYK1/NOK-induced B-CLL is heterogeneous. The expanded B1 lymphocyte pool was detected within peripheral lymphoid organs and was frequently associated with the expansions of memory B cells. Despite this immunophenotypic heterogeneity, suppression of B cell development at an early stage consistently occurred within the bone marrow (BM) of STYK1/NOK-tg mice. Overall, we suggest that enforced expression of STYK1/NOK in transgenic mice might significantly predispose BM hematopoietic stem cells (HSCs) towards the development of B-CLL.

STYK1/NOK affects cell cycle late mitosis and directly interacts with anaphase-promoting complex activator CDH1

The novel oncogene STYK1/NOK plays critical roles in cancer development. However, its regulation during cell division is less defined. In this paper, we show that over-expression of STYK1/NOK caused mitotic arrest and cytokinesis defects. The protein level of STYK/NOK fluctuated during the cell cycle, with a peak at mitosis and a quick reduction upon mitotic exit. The cell cycle-related expression pattern of STYK1/NOK resembled the one of aurora kinases and polo-like kinase 1. Depletion of APC3 led to accumulation of STYK1/NOK and to the G2/M arrest. Co-immunoprecipitation experiment demonstrated the direct interaction of STYK1/NOK with CDH1. Overexpression of CDH1 shortened the half-life of STYK1/NOK. The kinase domain, but not the five D boxes, of STYK1/NOK was responsible for the interaction with CDH1. Altogether, our data demonstrated for the first time that STYK1/NOK could affect cell division, probably by directly targeting key components of APC/C such as CDH1 at late mitosis. Current study may provide a vital mechanistic clue for understanding the roles of STYK1/NOK in mitosis and cytokinesis during STYK1NOK mediated genomic instability and oncogenesis.

Induction of chronic lymphocytic leukemia-like disease in STYK1/NOK transgenic mice

STYK1/NOK functions in a ligand independent and constitutive fashion to provoke tumor formation and to be up-regulated in many types of cancer cells. However, how STYK1/NOK functions at the whole animal level is completely unknown. Here, we found that STYK1/NOK-transgenic (tg) mice spontaneously developed immunosuppressive B-CLL-like disease with generally shorter life spans. The phenotype of STYK1/NOK-induced B-CLL was typically heterogeneous, and most often, presented lymphadenectasis accompanied with hepatomegaly and/or splenomegaly. STYK1/NOK-tg mice also suffered reduced immune responses. The expanded CD5⁺CD19⁺ (B1) lymphocyte pool was detected within peripheral lymphoid organs. Analysis on GEO profile revealed that expression of STYK1/NOK were significantly up-regulated in primary human B-CLL. Inoculation of blood cells from sick STYK1/NOK-tg mice into immune-deficient recipients recaptured the B1 malignant phenotype. Our study demonstrated that STYK1/NOK transgenic mouse may serve as a useful model system for the developments of novel diagnosis and treatment of B-CLL.

STYK1/NOK Promotes Metastasis and Epithelial-Mesenchymal Transition in Non-small Cell Lung Cancer by Suppressing FoxO1 Signaling

Aims

Serine/threonine/tyrosine kinase 1 (STYK1) has been previously shown to have oncogenic properties, and emerging evidence suggests that STYK1 expression correlates with epithelial-mesenchymal transition (EMT). However, the mechanism of STYK1 involvement in oncogenesis remains unknown. The present study aimed to elucidate how STYK1 expression level relates to the metastasis, migration, invasion, and EMT in non-small cell lung cancer (NSCLC) and to determine the molecular mechanism of STYK1 effects.

Methods

Serine/threonine/tyrosine kinase 1 (STYK1) expression level and its relationship with the prognosis of NSCLC were determined using the ONCOMINE database and clinical cases. Non-small cell lung cancer cell lines with the overexpression or knockdown of STYK1 were established to determine whether STYK1 promotes cell migration, invasion, and EMT in vitro and in vivo. In addition, a constitutively active FoxO1 mutant (FoxO1AAA) was used to examine the role of FoxO1 in the STYK1-mediated upregulation of metastasis and EMT in NSCLC.

Results

Serine/threonine/tyrosine kinase 1 (STYK1) was upregulated in NSCLC tissues and cell lines, and its overexpression correlated with poor prognosis in patients with NSCLC after surgery. Enhanced expression of STYK1 potentiated the migration, invasion, and EMT in SW900 cells, thereby promoting metastasis, whereas knockdown of STYK1 inhibited these cellular phenomena in Calu-1 cells. Furthermore, STYK1 expression was positively related to the level of phosphorylated-FoxO1, whereas the constitutively active FoxO1 mutant protected against the positive effect of STYK1 overexpression on cell migration, invasion, and EMT.

Conclusion

Serine/threonine/tyrosine kinase 1 (STYK1) was upregulated in NSCLC and correlated with poor clinical outcomes. In addition, STYK1 suppressed FoxO1 functions, thereby promoting metastasis and EMT in NSCLC.

NOK associates with c-Src and promotes c-Src-induced STAT3 activation and cell proliferation

Signal transducers and activators of transcription 3 (STAT3) is reported to regulate cell proliferation, survival, and differentiation, and thus plays a central role in development and carcinogenesis. Accumulating evidence demonstrated the involvement of cellular Src (c-Src) tyrosine kinase in the activation of STAT3. Additionally, novel oncogene with kinase-domain (NOK), a receptor protein tyrosine kinase that involves in cell transformation and tumorigenesis, was found to activate STAT3 signaling by a JAK2-dependent mechanism. However, whether the existence of the interaction between c-Src/STAT3 and NOK/STAT3 signals is still unknown. In this study, we showed that NOK formed a complex with c-Src and facilitated the interaction between c-Src and STAT3. In the complex, NOK greatly elevated the c-Src-mediated STAT3 activation by increasing the phosphorylation level of STAT3 on Tyr705. Truncated and mutation experiments further demonstrated that the kinase activity was responsible for the synergistic effect of NOK and c-Src on STAT3 activation. In addition, NOK and c-Src synergistically promoted cell proliferation and tumor growth in nude mice. Taken together, our results indicate that NOK associates with c-Src and promotes c-Src-induced STAT3 activation in a kinase-dependent manner. We proposed that the axis that NOK promoted c-Src-induced STAT3 activation is critical in cell proliferation and tumorigenesis.

STYK1 promotes autophagy through enhancing the assembly of autophagy-specific class III phosphatidylinositol 3-kinase complex I

Macroautophagy/autophagy plays key roles in development, oncogenesis, and cardiovascular and metabolic diseases. Autophagy-specific class III phosphatidylinositol 3-kinase complex I (PtdIns3K-C1) is essential for autophagosome formation. However, the regulation of this complex formation requires further investigation. Here, we discovered that STYK1 (serine/threonine/tyrosine kinase 1), a member of the receptor tyrosine kinases (RTKs) family, is a new upstream regulator of autophagy. We discovered that STYK1 facilitated autophagosome formation in human cells and zebrafish, which was characterized by elevated LC3-II and lowered SQSTM1/p62 levels and increased puncta formation by several marker proteins, such as ATG14, WIPI1, and ZFYVE1. Moreover, we observed that STYK1 directly binds to the PtdIns3K-C1 complex as a homodimer. The binding with this complex was promoted by Tyr191 phosphorylation, by means of which the kinase activity of STYK1 was elevated. We also demonstrated that STYK1 elevated the serine phosphorylation of BECN1, thereby decreasing the interaction between BECN1 and BCL2. Furthermore, we found that STYK1 preferentially facilitated the assembly of the PtdIns3K-C1 complex and was required for PtdIns3K-C1 complex kinase activity. Taken together, our findings provide new insights into autophagy induction and reveal evidence of novel crosstalk between the components of RTK signaling and autophagy. Abbreviations: AICAR: 5-aminoimidazole-4-carboxamide ribonucleotide; AMPK: adenosine 5'-monophosphate (AMP)-activated protein kinase; ATG: autophagy related; ATP: adenosine triphosphate; BCL2: BCL2 apoptosis regulator; BECN1: beclin 1; Bre A: brefeldin A; Co-IP: co-immunoprecipitation; CRISPR: clustered regularly interspaced short palindromic repeats; DAPI: 4',6-diamidino-2-phenylindole; EBSS: Earle's balanced salt solution; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescent protein; GSEA: gene set enrichment analysis; MAP1LC3/LC3, microtubule associated protein 1 light chain 3; MAPK8/JNK1: mitogen-activated protein kinase 8; mRFP: monomeric red fluorescent protein; MTOR: mechanistic target of rapamycin kinase; MTT: 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide; PIK3C3: phosphatidylinositol 3-kinase catalytic subunit type 3; PIK3R4: phosphoinositide-3-kinase regulatory subunit 4; qRT-PCR: quantitative reverse transcription PCR; RACK1: receptor for activated C kinase 1; RUBCN: rubicon autophagy regulator; siRNA: small interfering RNA; SQSTM1: sequestosome 1; STYK1/NOK: serine/threonine/tyrosine kinase 1; TCGA: The Cancer Genome Atlas; Ub: ubiquitin; ULK1: unc-51 like autophagy activating kinase 1; UVRAG: UV radiation resistance associated; WIPI1: WD repeat domain, phosphoinositide interacting 1; ZFYVE1: zinc finger FYVE-type containing 1.

STYK1 promotes tumor growth and metastasis by reducing SPINT2/HAI-2 expression in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the leading cause of cancer deaths worldwide. However, the molecular mechanisms underlying NSCLC progression remains not fully understood. In this study, 347 patients with complete clinicopathologic characteristics who underwent NSCLC surgery were recruited for the investigation. We verified that elevated serine threonine tyrosine kinase 1 (STYK1) or decreased serine peptidase inhibitor Kunitz type 2 (SPINT2/HAI-2) expression significantly correlated with poor prognosis, tumor invasion, and metastasis of NSCLC patients. STYK1 overexpression promoted NSCLC cells proliferation, migration, and invasion. STYK1 also induced epithelial–mesenchymal transition by E-cadherin downregulation and Snail upregulation. Moreover, RNA-seq, quantitative polymerase chain reaction (qRT-PCR), and western blot analyses confirmed that STYK1 overexpression significantly decreased the SPINT2 level in NSCLC cells, and SPINT2 overexpression obviously reversed STYK1-mediated NSCLC progression both in vitro and in vivo. Further survival analyses showed that NSCLC patients with high STYK1 level and low SPINT2 level had the worst prognosis and survival. These results indicated that STYK1 facilitated NSCLC progression via reducing SPINT2 expression. Therefore, targeting STYK1 and SPINT2 may be a novel therapeutic strategy for NSCLC.

SMAD3 inducing the transcription of STYK1 to promote the EMT process and improve the tolerance of ovarian carcinoma cells to paclitaxel

OBJECTIVE

To figure out the relationship between SMAD3 and serine-threonine tyrosine kinase (STYK1) in ovarian carcinoma cell's paclitaxel resistance.

METHODS

The quantitative reverse transcription-polymerase chain reactpostion and Western blot analysis were used to analyze RNA and protein content of SMAD3 and STYK1, respectively. The chromatin immunoprecipitation assay was used to confirm the binding site of SMAD3 to the STYK1 promoter region. Transwell assay was used to detect cell invasion and migration, and Western Blot was used to detect the marker proteins (vimentin and E-cadherin) of epithelial-mesenchymal transition (EMT) process. MTT and apoptosis assay were used to, respectively, measure cell vitality and apoptosis. In vivo experiments, rats were subcutaneously implanted with A2780 cells to establish an animal model of ovarian cancer and the survival curve was drawn.

RESULTS

Upregulating SMAD3 induced the expression of STYK1 in ovarian cancer cell lines. STYK1 is a direct transcriptional target of SMAD3. Upregulating STYK1 improved the paclitaxel resistance of ovarian carcinoma cells. Upregulating STYK1 promoted cell invasion, migration, and the EMT process, and SMAD3 had the same effect with STYK1 on cell invasion, cell migration, and the EMT process. The animal assay showed that downregulating STYK1 inhibited the EMT process and the paclitaxel resistance, further promoting the treatment of cervical cancer.

CONCLUSION

SMAD3 combined with the promoter region of STYK1 to promote the transcription process of STYK1, thereby promoting the EMT process and paclitaxel resistance of ovarian cancer cells.

STYK1 promotes cancer cell proliferation and malignant transformation by activating PI3K-AKT pathway in gallbladder carcinoma

Gallbladder carcinoma (GBC) is the most common malignancy of the biliary tract with extremely poor prognosis. The malignant transformation of GBC is associated with cell proliferation, invasion, and epithelial-mesenchymal transition (EMT). However, the molecular mechanisms underlying GBC progression are poorly understood. We found that serine threonine tyrosine kinase 1 (STYK1) was elevated in GBC and was negatively correlated with clinical outcomes and prognosis. Overexpression of STYK1 in GBC cell lines gave rise to increased cell proliferation, colony formation, migration and invasion, thus committing cells to undergoing EMT. In contrast, silence of STYK1 led to opposite effects on cell transformation. Consistent with STYK1 gene knockdown, AKT specific inhibitor MK2206 abrogated tumor promoting action induced by STYK1, suggesting that PI3K/AKT pathway is essential for the oncogenic role of STYK1 in GBC. STYK1 shRNA in GBC cells inhibited development of xenografted tumors compared with control cells. Collectively, our findings suggest that STYK1 is a critical regulator of tumor growth and metastasis, and may serve as a potential target for GBC therapy.

Depletion of STYK1 inhibits intrahepatic cholangiocarcinoma development both in vitro and in vivo

Intrahepatic cholangiocarcinoma (ICC) has been reported to be the second most common primary hepatic carcinoma worldwide, and very limited therapies are currently available. Serine threonine tyrosine kinase (STYK1), a member of the receptor tyrosine kinase family, exhibits tumorigenicity in many types of cancers and is a potential therapeutic target for ICC. In this study, STYK1 was knocked down in the ICC cell lines HCCC-9810 and RBE via a lentivirus-mediated system using short hairpin RNA (shRNA). Next, cell proliferation, colony formation, cell cycle progression, tumor formation in nude mice, migration and invasion, and the expression levels of cell cycle proteins in Lv-sh STYK1- or Lv-sh Con-infected cells were analyzed by CCK-8 assay, colony formation evaluation, flow cytometry, tumor formation evaluation, wound scratch assay, transwell assay, and western blotting. The results indicated that depletion of STYK1 inhibits ICC development both in vitro and in vivo.

Diagnostic relevance of overexpressed serine threonine tyrosine kinase/novel oncogene with kinase domain (STYK1/ NOK) mRNA in colorectal cancer

BACKGROUND

Alterations in gene expression levels or mutations of tyrosine kinases are detected in some human cancers. In this study, we examined whether serine threonine tyrosine kinase 1 (STYK1)/novel oncogene with kinase domain (NOK) is overexpressed in patients with colorectal cancer. We also examined the clinical relevance of STYK1/NOK expression in cancer tissues.

MATERIALS AND METHODS

In tumor samples of patients with colorectal cancer and their matched non-cancerous samples, STYK1/NOK messenger RNA (mRNA) expression was analyzed by quantitative reverse transcriptase polymerase chain reaction. Associations between the expression levels of STYK1/NOK and clinicopathological characteristics of colorectal cancer were also assessed using Mann-Whitney U and Kruskal-Wallis tests.

RESULTS

Upregulation of STYK1/NOK was found in cancer tissues even at early stage of colorectal cancer compared to normal adjacent tissues. The optimal cutoff point of 0.198 the STYK1/NOK expression showed 0.78 sensitivity and 0.75 specificity for diagnosis. Overexpressed STYK1/NOK was correlated with tumor size but had no association with other clinicopathological characteristics of colorectal cancer.

CONCLUSIONS

These results indicate that STYK1/NOK mRNA is widely expressed in the patients with colorectal cancer and suggest that inhibition of this molecule could potentially serve as a novel therapeutic target.

Serine threonine tyrosine kinase 1 is a potential prognostic marker in colorectal cancer

BACKGROUND

Aberrant expression of serine threonine tyrosine kinase 1 (STYK1) has been reported in several human malignancies including colorectal cancer (CRC). However, the prognostic significance of STYK1 expression in CRC remains unknown.

METHODS

STYK1 protein expression in paraffin-embedded CRC specimens was determined immunohistochemically. The correlation of STYK1 expression with clinicopathologic features was assessed in a cohort containing 353 patients with primary CRC. Kaplan-Meier and Cox proportional regression analyses were used to evaluate the association between STYK1 expression and patients' survival.

RESULTS

STYK1 expression was frequently up-regulated in CRC clinical samples at the protein levels and was significantly associated with tumor differentiation grade (p = 0.030), lymph node metastasis (p = 0.004), TNM stage (p = 0.007) and patient death (p < 0.001). Kaplan-Meier analysis indicated that patients with high intratumoral STYK1 expression had a significantly shorter disease-specific survival (DSS) than those with low expression (p < 0.001). Importantly, high levels of STYK1 protein predicted poor DSS for both stage II (p < 0.001) and stage III (p = 0.004) patients. Furthermore, multivariate analyses revealed that STYK1 protein expression was an independent prognostic indicator for both stage II (hazard ratio [HR], 2.472; p = 0.001) and stage III (HR, 2.001; p = 0.004) patients.

CONCLUSIONS

Our results suggest that increased STYK1 protein expression correlates with disease progression and metastasis and may serve as a predictor of poor survival in CRC.

Going for broke: targeting the human cancer pseudokinome

Protein phosphorylation lies at the heart of cell signalling, and somatic mutation(s) in kinases drives and sustains a multitude of human diseases, including cancer. The human protein kinase superfamily (the kinome) encodes approximately 50 'pseudokinases', which were initially predicted to be incapable of dynamic cell signalling when compared with canonical enzymatically active kinases. This assumption was supported by bioinformatics, which showed that amino acid changes at one or more key loci, making up the nucleotide-binding site or phosphotransferase machinery, were conserved in multiple vertebrate and non-vertebrate pseudokinase homologues. Protein kinases are highly attractive targets for drug discovery, as evidenced by the approval of almost 30 kinase inhibitors in oncology, and the successful development of the dual JAK1/2 (Janus kinase 1/2) inhibitor ruxolitinib for inflammatory indications. However, for such a large (>550) protein family, a remarkable number have still not been analysed at the molecular level, and only a surprisingly small percentage of kinases have been successfully targeted clinically. This is despite evidence that many are potential candidates for the development of new therapeutics. Indeed, several recent reports confirm that disease-associated pseudokinases can bind to nucleotide co-factors at concentrations achievable in the cell. Together, these findings suggest that drug targeting using either ATP-site or unbiased ligand-discovery approaches should now be attempted using the validation technology currently employed to evaluate their classic protein kinase counterparts. In the present review, we discuss members of the human pseudokinome repertoire, and catalogue somatic amino acid pseudokinase mutations that are emerging as the depth and clinical coverage of the human cancer pseudokinome expand.

Clinicopathologic features and prognostic implications of NOK/STYK1 protein expression in non-small cell lung cancer

Background

The expression of novel oncogenic kinase (NOK), a member of the protein tyrosine kinase (PTK) family, has been observed in several human malignancies including non-small cell lung cancer (NSCLC). However, the clinic relevance of NOK expression in NSCLC remains unclear.

Methods

In this study, NOK expression in tumor cells was assessed using immunohistochemical methods in 191 patients with resected NSCLC. The association of NOK expression with clinicopathological parameters, including the Ki-67 labeling index (LI), was also evaluated. Kaplan-Meier survival analysis and Cox proportional hazards models were used to estimate the effect of NOK expression on survival.

Results

Data showed that NOK was expressed in 75.4% and 14.1% of cancer lesions and corresponding adjacent non-cancerous tissue, respectively. Out of all the clinicopathological factors analyzed, NOK expression was significantly correlated with the grade of tumor differentiation (P = 0.035), pTNM stage (P = 0.020), lymphatic metastasis (P = 0.005) and high Ki-67 LI (P < 0.001). NOK positive NSCLC patients had a significantly shorter survival time (P = 0.004, Log-rank test) and the prognostic significance of NOK expression was apparent in squamous cell carcinoma patients (P = 0.022). Multivariate analysis indicated that NOK expression may be an independent prognostic factor in NSCLC (hazard ratio [HR], 1.731; P = 0.043).

Conclusions

Our results indicate that NOK expression is of clinical significance and can serve as a prognostic biomarker in NSCLC.

Receptor tyrosine kinases with intracellular pseudokinase domains

As with other groups of protein kinases, approximately 10% of the RTKs (receptor tyrosine kinases) in the human proteome contain intracellular pseudokinases that lack one or more conserved catalytically important residues. These include ErbB3, a member of the EGFR (epidermal growth factor receptor) family, and a series of unconventional Wnt receptors. We showed previously that, despite its reputation as a pseudokinase, the ErbB3 TKD (tyrosine kinase domain) does retain significant, albeit weak, kinase activity. This led us to suggest that a subgroup of RTKs may be able to signal even with very inefficient kinases. Recent work suggests that this is not the case, however. Other pseudokinase RTKs have not revealed significant kinase activity, and mutations that impair ErbB3's weak kinase activity have not so far been found to exhibit signalling defects. These findings therefore point to models in which the TKDs of pseudokinase RTKs participate in receptor signalling by allosterically regulating associated kinases (such as ErbB3 regulation of ErbB2) and/or function as regulated 'scaffolds' for other intermolecular interactions central to signal propagation. Further structural and functional studies, particularly of the pseudokinase RTKs involved in Wnt signalling, are required to shed new light on these intriguing signalling mechanisms.

NOK/STYK1 has a strong tendency towards forming aggregates and colocalises with epidermal growth factor receptor in endosomes

Our previous studies showed that the overexpression of Novel Oncogene with Kinase-domain (NOK)/STYK1 led to cellular transformation, tumorigenesis and metastasis. This report characterises the subcellular distribution of NOK in HeLa cells and its localisation in early endosomes. Confocal immunolocalisation studies indicated that NOK had structural subtypes and was distributed into two distinct expression patterns: a dot pattern (DP) and an aggregation pattern (AP). The results of an immunohistochemistry (IHC) analysis of pathological tissues also showed that high expression level of endogenous NOK was expressed in an aggregate-like structure in vivo. Importantly, we found that NOK was localised in endosomes and colocalised with epidermal growth factor receptor (EGFR) in activated endosomal vesicles. However, as the stimulation time increased, NOK and EGFR began to progress through different pathways. EGFR was gradually degraded after treatment with EGF for approximately 20 min, whereas NOK levels were not reduced. This result suggests that NOK mainly plays a role in facilitating the trafficking of EGFR from early endosomes to later endosomes/lysosomes. Taken together, NOK has a strong tendency towards forming aggregates, which may have physiological implications and provide the first evidence that this novel receptor kinase is colocalised with EGFR in endosomes to participate in a post-internalisation step of EGFR.

Altered LKB1/CREB-regulated transcription co-activator (CRTC) signaling axis promotes esophageal cancer cell migration and invasion

LKB1 is a tumor susceptibility gene for the Peutz-Jeghers cancer syndrome and is a target for mutational inactivation in sporadic human malignancies. LKB1 encodes a serine/threonine kinase that has critical roles in cell growth, polarity and metabolism. A novel and important function of LKB1 is its ability to regulate the phosphorylation of CREB-regulated transcription co-activators (CRTCs) whose aberrant activation is linked with oncogenic activities. However, the roles and mechanisms of LKB1 and CRTC in the pathogenesis of esophageal cancer have not been previously investigated. In this study, we observed altered LKB1-CRTC signaling in a subset of human esophageal cancer cell lines and patient samples. LKB1 negatively regulates esophageal cancer cell migration and invasion in vitro. Mechanistically, we determined that CRTC signaling becomes activated because of LKB1 loss, which results in the transcriptional activation of specific downstream targets including LYPD3, a critical mediator for LKB1 loss-of-function. Our data indicate that de-regulated LKB1-CRTC signaling might represent a crucial mechanism for esophageal cancer progression.

Aberrant STYK1 expression in ovarian cancer tissues and cell lines

Background

Overexpression of STYK1, a putative serine/threonine and tyrosine receptor protein kinase has been shown to confer tumorigenicity and metastatic potential to normal cells injected into nude mice. Mutation of a tyrosine residue in the catalytic STYK1 domain attenuates the tumorigenic potential of tumor cells in vivo, collectively, suggesting an oncogenic role for STYK1.

Methods

To investigate the role of STYK1 expression in ovarian cancer, a panel of normal, benign, and ovarian cancer tissues was evaluated for STYK1 immunoreactivity using STYK1 antibodies. In addition, mRNA levels were measured by reverse transcription PCR and real-time PCR of estrogen receptors, GPR30 and STYK1 following treatment of ovarian cell lines with estrogen or G1, a GPR30 agonist, as well as western analysis.

Results

Our data showed higher expression of STYK1 in cancer tissues versus normal or benign. Only normal or benign, and one cancer tissue were STYK1-negative. Moreover, benign and ovarian cancer cell lines expressed STYK1 as determined by RT-PCR. Estradiol treatment of these cells resulted in up- and down-regulation of STYK1 despite estrogen receptor status; whereas G-1, a GPR30-specific agonist, increased STYK1 mRNA levels higher than that of estradiol.

Conclusion

We conclude that STYK1 is expressed in ovarian cancer and is regulated by estrogen through a GPR30 hormone-signaling pathway, to the exclusion of estrogen receptor-alpha.

Overexpression of serine threonine tyrosine kinase 1/novel oncogene with kinase domain mRNA in patients with acute leukemia

OBJECTIVE

Alterations in gene expression levels or mutations of previously reported tyrosine kinases are detected in only limited numbers of patients with acute leukemia. In this study, we examined whether serine threonine tyrosine kinase 1 (STYK1)/novel oncogene with kinase domain (NOK) is overexpressed in patients with acute leukemia.

MATERIALS AND METHODS

In peripheral blood cells from nonleukemic group and acute leukemic patients, STYK1/NOK messenger RNA (mRNA) expression was analyzed by quantitaive reverse transcriptase polymerase chain reaction. The effect of inhibition of STYK1/NOK mRNA on the leukemic cells was also examined.

RESULTS

When appropriate, cutoff was set using the values in nonleukemic individuals, positive STYK1/NOK expression was detected in 80.0% of leukemic patients. STYK1/NOK mRNA was highly expressed in the patients with trisomy/tetrasomy 21. mRNA expression began to decrease after chemotherapy with various drugs; this resulted in a decrease in the number of leukemic blasts in the patients' peripheral blood samples. Such changes in the gene expression were also noted in promyelocytic leukemia (M3) patients treated with all-trans retinoic acid. In addition, transfection of small inhibitory RNA against the STYK1/NOK gene into K562 cells inhibited their growth in proportion to the decrease in the mRNA expression.

CONCLUSION

These results indicate that STYK1/NOK mRNA is widely expressed in the patients with acute leukemia and suggest that inhibition of this molecule could potentially serve as a novel therapeutic target.

Transmembrane helix of novel oncogene with kinase-domain (NOK) influences its oligomerization and limits the activation of RAS/MAPK signaling

Ligand-dependent or independent oligomerization of receptor protein tyrosine kinase (RPTK) is often an essential step for receptor activation and intracellular signaling. The novel oncogene with kinase-domain (NOK) is a unique RPTK that almost completely lacks an ectodomain, expresses intracellularly and activates constitutively. However, it is unknown whether NOK can form oligomer or what function oligomerization would have. In this study, two NOK deletion mutants were generated by either removing the ectodomain (NOKDeltaECD) or including the endodomain (NOK-ICD). Co-immunoprecipitation demonstrated that the transmembrane (TM) domain of NOK was essential for its intermolecular interaction. The results further showed that NOK aggregated more closely as lower order oligomers (the dimer- and trimer-sized) than either deletion mutant did since NOK could be cross-linked by both Sulfo-EGS and formaldehyde, whereas either deletion mutant was only sensitive to Sulfo-EGS. Removing the NOK TM domain (NOK-ICD) not only markedly promoted higher order oligomerization, but also altered the subcellular localization of NOK and dramatically elevated the NOK-mediated constitutive activation of extracellular signal-regulated kinase (ERK). Moreover, NOK-ICD but not NOK or NOKDeltaECD was co-localized with the upstream signaling molecule RAS on cell membrane. Thus, TM-mediated intermolecular contacting may be mainly responsible for the constitutive activation of NOK and contribute to the autoinhibitory effect on RAS/MAPK signaling.

A novel gene STYK1/NOK is upregulated in estrogen receptor-alpha negative estrogen receptor-beta positive breast cancer cells following estrogen treatment

The human STYK1/NOK protein is approximately 30-35% similar to mouse fibroblast growth factor receptor 3 and a kinase homologue in D. melanogaster in the tyrosine protein kinase region. STYK1/NOK was identified as being up regulated in MDA-MB-231, an estrogen receptor-alpha negative breast cancer cell line, following 12 h of estrogen treatment at 1x10(-9) M. On further investigation of STYK1/NOK in estrogen treated cell line MDA-MB-231, STYK1/NOK was up regulated at 6 h post treatment when compared to untreated cells. We also investigated the expression levels of STYK1/NOK in other breast cancer cell lines MCF-7, MDA-MB-231, BT-549, and MDA-MB-435S using QRT-PCR. In addition, the analysis of message accumulation was increased with other synthetic estrogen response modifiers. We propose that the regulation of STYK1/NOK is achieved independent of ERalpha and suggests further investigation to the relevance of this kinase in breast cancer progression.

The carboxyl terminal tyrosine 417 residue of NOK has an autoinhibitory effect on NOK-mediated signaling transductions

Receptor protein tyrosine kinases (RPTKs) are essential mediators of cell growth, differentiation, migration, and metabolism. Recently, a novel RPTK named NOK has been cloned and characterized. In current study, we investigated the role of the carboxyl terminal tyrosine 417 residue of NOK in the activations of different signaling pathways. A single tyrosine to phenylalanine point mutation at Y417 site (Y417F) not only dramatically enhanced the NOK-induced activation of extracellular signal-regulated kinase (ERK), but also markedly promoted the NOK-mediated activation of both signal transducer and activator of transcription 1 and 3 (STAT1 and 3). Moreover, the proliferation potential of NIH3T3-NOK (Y417F) stable cells were significantly elevated as compared with that of NIH3T3-NOK. Overall, our results demonstrate that the tyrosine Y417 residue at the carboxyl tail of NOK exhibits an autoinhibitory role in NOK-mediated signaling transductions.

Diagnostic relevance of overexpressed mRNA of novel oncogene with kinase-domain (NOK) in lung cancers

There have been no target molecules that have enabled us to diagnose lung cancer with high sensitivity and specificity even in its early clinical stages. A molecule termed novel oncogene with kinase-domain (NOK) was recently reported as a receptor protein tyrosine kinase that is expressed in some cancer cell lines and causes the transformation and progressive proliferation of normal cells. Therefore, NOK could be a possible candidate for a diagnostic marker for human cancers. We examined here, the degree of NOK mRNA expression in lung cancer tissues and compared it to that in non-cancerous tissues. More than 60% of non-cancerous samples (8/13) showed undetectable levels of mRNA. In contrast, NOK mRNA was detected in 97.6% (40/41) of lung cancer tissues, resulting in a sensitivity of 80.5% and a specificity of 92.3% that was estimated using the cutoff obtained from receiver operating characteristic curve analysis. Further, NOK mRNA expression was found to be elevated in 92.3% (12/13) of cancerous tissues when paired cancerous and non-cancerous tissues from identical patients were compared. There were no obvious correlations between clinicopathological factors and NOK mRNA expression; however, NOK mRNA was highly expressed even at the early clinical stages of the cancer. These results suggest that NOK mRNA might be a new tool to support the diagnosis of lung cancers, irrespective of the clinical stages.