Enhanced expression of cholecystokinin-2 receptor promotes the progression of colon cancer through activation of focal adhesion kinase

Functional and clinical characteristics of focal adhesion kinases in cancer progression

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase and an adaptor protein that primarily regulates adhesion signaling and cell migration. FAK promotes cell survival in response to stress. Increasing evidence has shown that at the pathological level, FAK is highly expressed in multiple tumors in several systems (including lung, liver, gastric, and colorectal cancers) and correlates with tumor aggressiveness and patient prognosis. At the molecular level, FAK promotes tumor progression mainly by altering survival signals, invasive capacity, epithelial-mesenchymal transition, the tumor microenvironment, the Warburg effect, and stemness of tumor cells. Many effective drugs have been developed based on the comprehensive role of FAK in tumor cells. In addition, its potential as a tumor marker cannot be ignored. Here, we discuss the pathological and pre-clinical evidence of the role of FAK in cancer development; we hope that these findings will assist in FAK-based clinical studies.

High expression of phosphorylated focal adhesion kinase predicts a poor prognosis in human colorectal cancer

Background: Phosphorylated Focal adhesion kinase (FAK) has been reported to be intimately involved in various malignant tumors. The effect of p-FAK on colorectal cancer (CRC) is still disputable. The purpose of this study is to investigate the role of p-FAK in the prognosis of colorectal cancer.

Methods: The clinical significance of p-FAK expression in CRC was evaluated by immunohistochemistry in a large cohort, including carcinoma and para-carcinoma tissues from 908 patients, and normal tissues, adenoma, and metastasis tissues. The correlation between p-FAK expression and CRC occurrence was investigated in tumor and other tissues. Factors contributing to prognosis were evaluated using Kaplan-Meier survival analysis and Cox regression model.

Results: p-FAK is apparently overexpressed in CRC and metastasis tissues. Compared with low p-FAK expression, patients with high p-FAK expression had shorter overall survival [hazard ratio (HR), 2.200; 95% confidence interval (CI), 1.265–3.452; p < 0.01] and disease-free survival (HR, 2.004; 95% CI 1.262–3.382; p < 0.01) in multivariate Cox analysis after adjusting other prognostic factors. High p-FAK expression was also related to a worse chemotherapeutic response in patients who achieved adjuvant chemotherapy (p < 0.01).

Conclusion: Expression level of p-FAK is an independent risk factor and can serve as a prognostic biomarker for CRC. High p-FAK expression predicts an unfavorable prognosis of CRC as well as poor chemotherapeutic response.

Cholecystokinin type 2 receptor in colorectal cancer: diagnostic and therapeutic target

INTRODUCTION

Cholecystokinin type 2 receptor (CCK2R), which mediates the action of gastrin and cholecystokinin (CCK), has been demonstrated to promote the proliferation of colorectal cancer (CRC). A number of studies showed that CCK2R overexpressed in gastric cancer and pancreatic cancer but few in CRC. The correlation between CCK2R expression and clinicopathological characteristics is also not clear.

METHODS

This study investigated CCK2R expression in a wide range of cell lines and clinical CRC samples, and explored expression pattern and prognostic value of CCK2R in relation to clinicopathological parameters. The location and expression levels of CCK2R were measured by immunocytochemical (ICC), qRT-PCR and Western blot. The druggability and antineoplastic effects of CCK2R as a therapeutic target were investigated using an anti-CCK2R targeting recombinant toxin named rCCK8PE38 by CCK-8 assay.

RESULTS

Compared with paracarcinoma tissues, tumor samples showed overexpression of CCK2R (p = 0.028) including both CRC tissue and plasma samples, with plasma detection showing a significant indication for CCK2R evaluation. Aberrant expression correlated significantly with histological type (p = 0.032) and p53 status (p < 0.01), and patients with CCK2R overexpression had significantly lower disease-free survival. Application of rCCK8PE38 demonstrated the specificity and druggability of CCK2R as a therapeutic target, providing a strategy for clinical case screening of drugs targeting CCK2R.

CONCLUSION

This study highlighted the aberrant expression and clinical correlation of CCK2R and reveals its diagnostic, prognostic and treatment value in CRC. We hypothesize that CCK2R serve as a target for the diagnosis and treatment of this cancer.

The Neuropeptide System and Colorectal Cancer Liver Metastases: Mechanisms and Management

Colorectal cancer (CRC), classified as the third most prevalent cancer worldwide, remains to be a clinical and research challenge. It is estimated that ~50% of CRC patients die from distant metastases, with treatment of this complication still posing significant difficulties. While liver metastasis (LM) cascade is known in the literature, its mechanisms are still unclear and remain studied in different research models. A connection is suggested between nervous system dysfunctions and a range of Neurotransmitters (Nts) (including Neuropeptides, NPs), Neurotrophins (Ntt) and their receptors (Rs) in CRC liver metastasis development. Studies on the role of NP/NP-Rs in the progression and metastasis of CRC, show the complexity of brain–tumor interactions, caused by their different forms of release to the extracellular environment (endocrine, autocrine, paracrine and neurocrine). Many stages of LM are connected to the activity of pro-inflammatory, e.g., Corticotropin-releasing Hormone Receptor 1 (CRHR1), Neuropeptide Y (NPY) and Neurotensin (NT), anti-inflammatory, e.g., Calcitonin Gene-related Peptide (CGRP), CRHR2 and Vasoactive Intestinal Polypeptide (VIP) or dual role neuropeptides, e.g., Substance P (SP). The regulation of the local immunological profile (e.g., CRH/CRHRs), dysfunctions of enteroprotective role of NPs on epithelial cells (e.g., NT/NT-R), as well as structural-functional changes in enteric nervous system innervation of the tumor are also important. More research is needed to understand the exact mechanisms of communication between the neurons and tumor cells. The knowledge on the mechanisms regulating tumor growth and different stages of metastasis, as well as effects of the action of a numerous group of Nts/NPs/Ntt as growth factors, have implications for future therapeutic strategies. To obtain the best treatment outcomes, it is important to use signaling pathways common for many NPs, as well to develop a range of broad-spectrum antagonists. This review aims to summarize the current knowledge on the importance of neuroactive molecules in the promotion of the invasion-metastasis cascade in CRC, as well as the improvements of clinical management of CRC liver metastasis.

The Neuropeptide System and Colorectal Cancer Liver Metastases: Mechanisms and Management

Colorectal cancer (CRC), classified as the third most prevalent cancer worldwide, remains to be a clinical and research challenge. It is estimated that ~50% of CRC patients die from distant metastases, with treatment of this complication still posing significant difficulties. While liver metastasis (LM) cascade is known in the literature, its mechanisms are still unclear and remain studied in different research models. A connection is suggested between nervous system dysfunctions and a range of Neurotransmitters (Nts) (including Neuropeptides, NPs), Neurotrophins (Ntt) and their receptors (Rs) in CRC liver metastasis development. Studies on the role of NP/NP-Rs in the progression and metastasis of CRC, show the complexity of brain–tumor interactions, caused by their different forms of release to the extracellular environment (endocrine, autocrine, paracrine and neurocrine). Many stages of LM are connected to the activity of pro-inflammatory, e.g., Corticotropin-releasing Hormone Receptor 1 (CRHR1), Neuropeptide Y (NPY) and Neurotensin (NT), anti-inflammatory, e.g., Calcitonin Gene-related Peptide (CGRP), CRHR2 and Vasoactive Intestinal Polypeptide (VIP) or dual role neuropeptides, e.g., Substance P (SP). The regulation of the local immunological profile (e.g., CRH/CRHRs), dysfunctions of enteroprotective role of NPs on epithelial cells (e.g., NT/NT-R), as well as structural-functional changes in enteric nervous system innervation of the tumor are also important. More research is needed to understand the exact mechanisms of communication between the neurons and tumor cells. The knowledge on the mechanisms regulating tumor growth and different stages of metastasis, as well as effects of the action of a numerous group of Nts/NPs/Ntt as growth factors, have implications for future therapeutic strategies. To obtain the best treatment outcomes, it is important to use signaling pathways common for many NPs, as well to develop a range of broad-spectrum antagonists. This review aims to summarize the current knowledge on the importance of neuroactive molecules in the promotion of the invasion-metastasis cascade in CRC, as well as the improvements of clinical management of CRC liver metastasis.

Changes in plasma levels of cholecystokinin, neurotensin, VIP and PYY in gastric and colorectal cancer - Preliminary results

Physiological roles of enterohormones such as secretion, absorption and digestion were supported by clinical data. Overexpression of cholecystokinin (CCK), neurotensin (NT) and vasoactive intestinal peptide (VIP) receptors occur in gastrointestinal (GI) malignancies. The aim of the paper was to compare plasma levels of CCK, peptide YY (PYY), VIP and NT in patients with gastrointestinal malignancies and healthy controls. The study included 80 patients (37 men and 43 women) with GI malignancies (20 with gastric and 60 with colorectal cancers). Median age of the patients was 62.9 years (range: 40-85 years). Control group was comprised of 30 healthy persons with median age 59.8 years (range: 40-82 years). Fasting plasma concentrations of CKK, PYY, NT, and VIP were determined at rest, using ELISA kits for automated systems. Comparative analysis of enterohormone levels in patients with various types of gastrointestinal malignancies demonstrated presence of some cancer-specific alterations. Patients with gastric cancers presented with lower plasma concentrations of CCK than healthy controls and individuals from colorectal cancers (p = 0.02). The highest plasma concentrations of neurotensin was found in colorectal cancer patients in comparison to gastric (p = 0.02). The plasma levels of VIP observed in gastric cancer group were lower than in colorectal cancer patients (p = 0.01). Patients with GI malignancies may present with tumor-specific alterations in plasma enterohormone levels.

The role of Gαq/Gα11 signaling in intestinal epithelial cells

Intestinal homeostasis and the coordinated actions of digestion, absorption and excretion are tightly regulated by a number of gastrointestinal hormones. Most of them exert their actions through G-protein-coupled receptors. Recently, we showed that the absence of Gαq/Gα11 signaling impaired the maturation of Paneth cells, induced their differentiation toward goblet cells, and affected the regeneration of the colonic mucosa in an experimental model of colitis. Although an immunohistochemical study showed that Gαq/Gα11 were highly expressed in enterocytes, it seemed that enterocytes were not affected in Int-Gq/G11 double knock-out intestine. Thus, we used an intestinal epithelial cell line to examine the role of signaling through Gαq/Gα11 in enterocytes and manipulated the expression level of Gαq and/or Gα11. The proliferation was inhibited in IEC-6 cells that overexpressed Gαq/Gα11 and enhanced in IEC-6 cells in which Gαq/Gα11 was downregulated. The expression of T-cell factor 1 was increased according to the overexpression of Gαq/Gα11. The expression of Notch1 intracellular cytoplasmic domain was decreased by the overexpression of Gαq/Gα11 and increased by the downregulation of Gαq/Gα11. The relative mRNA expression of Muc2, a goblet cell marker, was elevated in a Gαq/Gα11 knock-down experiment. Our findings suggest that Gαq/Gα11-mediated signaling inhibits proliferation and may support a physiological function, such as absorption or secretion, in terminally differentiated enterocytes.

Daurinol blocks breast and lung cancer metastasis and development by inhibition of focal adhesion kinase (FAK)

FAK overexpression has been reported in diverse primary and metastatic tumor tissues, supporting its pro-tumorigenic and pro-metastatic roles. Therefore, we have developed a neo-treatment strategy using daurinol to effectively treat cancer metastasis. Daurinol blocked cancer cell migration and invasion in vitro and exhibited anti-metastatic activity in an experimental metastasis model of breast and lung cancer. Daurinol selectively inhibited phosphorylation of FAK at Tyr925, Tyr576/577, and Tyr397 sites in a dose- and time-dependent manner. Daurinol effectively suppressed migration and invasion of MDA-MB-231 and A549 cancer cells. These data were associated with inhibition of expression and secretion of invasion factors, including matrix metalloproteinase (MMP) 2, MMP9, and urokinase plasminogen activator (uPA). Consistent with these in vitro results, daurinol (10 mg/kg; Oral gavage) effectively inhibited breast and lung cancer metastasis in a mouse model. In addition, daurinol showed strong suppressive activity of cell survival as revealed by colony formation assays. Analysis of cellular phenotypes revealed that inhibition of FAK phosphorylation in cancer cells limited colony formation, cell migration, and invasion, thereby reducing the cell proliferation rate. Furthermore, daurinol significantly reduced tumor development in 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone (NNK)/benzo(a)pyrene (BaP)-treated A/J mice. Our results suggest that daurinol suppresses lung metastasis through inhibition of migration and survival via blockade of FAK activity.

Activation of focal adhesion kinase through an interaction with β4 integrin contributes to tumorigenicity of colon cancer

High expression of either β4 integrin or focal adhesion kinase (FAK) has been reported in human colon cancer. However, it remains unclear how β4 integrin together with FAK contributes to the tumorigenicity of colon cancer. Here, we demonstrate that the co-overexpression of β4 integrin and FAK positively correlates with advanced stages of human colon cancer. Activated β4 integrin interacts with FAK and subsequently induces FAK phosphorylation at Tyr397. Furthermore, ablation of the β4 integrin/FAK complex and/or FAK activation impair colon cancer cell proliferation, anchorage-independent growth, and tumorigenicity. Our data indicate that the β4 integrin/FAK complex and subsequent FAK activation are essential regulators during the tumorigenicity of colon cancer, and we suggest an alternative strategy for colon cancer therapy.

Assessment of cholecystokinin 2 receptor (CCK2R) in neoplastic tissue

The expression of cholecystokinin 2 receptor (CCK2R, CCKBR or gastrin receptor) has been reported on a diverse range of cancers such as colorectal, liver, lung, pancreatic, ovarian, stomach, thyroid and numerous neuroendocrine/carcinoid tumors. Some cancers of the colorectum, lung, pancreas and thyroid have been shown to overexpress CCK2R in relation to normal matched tissues of the same organ. This reported overexpression has led to the development of a number of CCK2R-ligand targeted imaging and therapeutic agents. However, no comprehensive study comparing the expression of CCK2R in multiple cancers to multiple normal tissues has been performed. Herein, we report the immunohistochemical analysis of cancer samples from gastrointestinal stromal tumor (GIST), hepatocellular carcinoma (HCC), non-small cell lung cancer (NSCLC), pancreatic adenocarcinoma, and thyroid cancer against multiple normal tissue samples from esophagus, liver, lung, pancreas, stomach, spleen and thyroid. These results show that CCK2R expression is present in nearly all cancer and normal samples tested and that none of the cancer samples had expression that was statistically greater than that of all of the normal samples.

FAK signaling in human cancer as a target for therapeutics

Focal adhesion kinase (FAK) is a key regulator of growth factor receptor- and integrin-mediated signals, governing fundamental processes in normal and cancer cells through its kinase activity and scaffolding function. Increased FAK expression and activity occurs in primary and metastatic cancers of many tissue origins, and is often associated with poor clinical outcome, highlighting FAK as a potential determinant of tumor development and metastasis. Indeed, data from cell culture and animal models of cancer provide strong lines of evidence that FAK promotes malignancy by regulating tumorigenic and metastatic potential through highly-coordinated signaling networks that orchestrate a diverse range of cellular processes, such as cell survival, proliferation, migration, invasion, epithelial-mesenchymal transition, angiogenesis and regulation of cancer stem cell activities. Such an integral role in governing malignant characteristics indicates that FAK represents a potential target for cancer therapeutics. While pharmacologic targeting of FAK scaffold function is still at an early stage of development, a number of small molecule-based FAK tyrosine kinase inhibitors are currently undergoing pre-clinical and clinical testing. In particular, PF-00562271, VS-4718 and VS-6063 show promising clinical activities in patients with selected solid cancers. Clinical testing of rationally designed FAK-targeting agents with implementation of predictive response biomarkers, such as merlin deficiency for VS-4718 in mesothelioma, may help improve clinical outcome for cancer patients. In this article, we have reviewed the current knowledge regarding FAK signaling in human cancer, and recent developments in the generation and clinical application of FAK-targeting pharmacologic agents.

Focal adhesion kinase inhibitors in the treatment of metastatic cancer: a patent review

INTRODUCTION

Focal adhesion kinase (FAK) plays a prominent role in integrin signaling. FAK activation increases phosphorylation of Tyr397 and other sites of the protein. FAK-dependent activation of signaling pathways implicated in controlling essential cellular functions including growth, proliferation, survival and migration. FERM (F for the 4.1 protein, ezrin, radixin and moesin) domain-enhanced p53 degradation plays a critical role in proliferation and survival. FAK, overexpressed in metastatic tumors, has emerged as an important therapeutic target for the development of selective inhibitors. FAK inhibitors achieved tumor growth inhibition and induced apoptosis. Strategies targeting FAK inhibition using novel compounds have created an exciting opportunity for anticancer therapy.

AREAS COVERED

This review summarizes the current research with available data from early phase clinical trials and discusses the available small-molecule inhibitors of FAK from patents. The importance of inhibiting FAK activity in cancer patients is discussed.

EXPERT OPINION

Emerging data from clinical trials with orally available small-molecule inhibitors of FAK are promising. Although this approach is appropriate as a targeted therapeutic approach against several metastatic cancer types, several compounds in research are yet to prove their preclinical efficacy. This report lays special emphasis on the available patent data of FAK inhibitors for such targeted molecular therapies. This review summarizes current knowledge about FAK inhibition in cancer therapy.

MiR-148a regulates the growth and apoptosis in pancreatic cancer by targeting CCKBR and Bcl-2

Our previous studies have revealed that miR-148a is downregulated in pancreatic cancer. Bioinformatics analysis has shown cholecystokinin-B receptor (CCKBR) and B cell lymphoma (Bcl-2) to be potential targets of miR-148a. But the pathophysiologic role of miR-148a and its relevance to the growth and development of pancreatic cancer are yet to be investigated. The purpose of this study is to elucidate the molecular mechanisms where miR-148a acts as a tumor suppressor in pancreatic cancer. Our results showed significant downregulation of miR-148a in 28 pancreatic cancer tissue samples and five pancreatic cancer cell lines, compared with their non-tumor counterparts by qRT-PCR. MiR-148a was found to not only inhibit the proliferation of pancreatic cancer cells (PANC-1 and AsPC-1) in vitro by MTT assay and colony formation assay, but also to promote cells apoptosis in vitro by Annexin V-FITC apoptosis detection and caspase activity assay. Using western blot and luciferase activity assay, CCKBR and Bcl-2 were identified as targets of miR-148a. Moreover, we also found that the expression of Bcl-2 lacking in 3'UTR could abrogate the pro-apoptosis function of miR-148a. These findings suggest the importance of miR-148a's targeting of CCKBR and Bcl-2 in the regulation of pancreatic cancer growth and apoptosis.

Multifactorial diagnostic NIR imaging of CCK2R expressing tumors

Optical imaging-based diagnostics identify malignancies based on molecular changes instead of morphological criteria in a non-invasive, irradiation free process. The aim of this study was to improve imaging efficiency by the development of a new Cholecystokinin-2-receptor targeted fluorescent peptide that matches the clinical needs regarding biodistribution and pharmacokinetics while displaying superior target specificity. Furthermore we performed multifactorial imaging of Cholecystokinin-2-receptor and tumor metabolism, since simultaneous targeting of various tumor biomarkers could intensely increase tumor identification and characterization. Affinity and specificity of the fluorescent Cholecystokinin-2-receptor targeted minigastrin (dQ-MG-754) were tested in vitro. We conducted in vivo imaging of the dQ-MG-754 probe alone and in a multifactorial approach with a GLUT-1 targeted probe (IR800 2-DG) on subcutaneous xenograft bearing athymic nude mice up to 24 h after intravenous injection (n = 5/group), followed by ex vivo biodistribution analysis and histological examination. We found specific, high affinity binding (Kd = 1.77 nM ± 0.6 nM) of dQ-MG-754 to Cholecystokinin-2-receptor expressing cells and xenografts as well as favorable pharmacokinetics for fluorescence-guided endoscopy. We successfully performed multifactorial imaging for the simultaneous detection of the Cholecystokinin-2-receptor and GLUT-1 targeted probe. Prominent differences in uptake patterns of the two contrast agents could be detected. The results were validated by histological examinations. The multifactorial imaging approach presented in this study could facilitate cancer detection in diagnostic imaging and intraoperative and endoscopic applications. Especially the dQ-MG-754 probe bears great potential for translation to clinical endoscopy imaging, because it combines specific high affinity binding with renal elimination and a favorable biodistribution.

Heterogeneous nuclear ribonucleoprotein K (hnRNP-K) promotes tumor metastasis by induction of genes involved in extracellular matrix, cell movement, and angiogenesis

Cancer is a leading cause of death and still awaits effective therapies. Rapid industrialization has contributed to increase in incidence of cancer. One of the reasons why most of the cancers fail therapy is due to their metastatic property. Hence identification of factors leading to metastasis is highly important to design effective and novel anti-cancer therapeutics. In our earlier study (Inoue, A., Sawata, S. Y., Taira, K., and Wadhwa, R. (2007) Loss-of-function screening by randomized intracellular antibodies: identification of hnRNP-K as a potential target for metastasis. Proc. Natl. Acad. Sci. U.S.A. 104, 8983-8988), we had reported that the involvement of heterogeneous nuclear ribonucleoprotein K (hnRNP-K) in metastasis. Here, we established hnRNP-K-overexpressing and -underexpressing derivative cell lines and examined their proliferation and metastatic properties in vitro and in vivo. Whereas hnRNP-K compromised cells showed delayed tumor growth, its overexpression resulted in enhanced malignancy and metastasis. Molecular basis of the hnRNP-K induced malignant and metastatic phenotypes was dissected by cDNA microarray and pathway analyses. We found that the hnRNP-K regulates extracellular matrix, cell motility, and angiogenesis pathways. Involvement of the selected genes (Cck, Mmp-3, Ptgs2, and Ctgf) and pathways was validated by gene-specific expression analysis. Our results demonstrated that the hnRNP-K is a potential target for metastasis therapy.

FAK, CD44v6, c-Met and EGFR in colorectal cancer parameters: tumour progression, metastasis, patient survival and receptor crosstalk

PURPOSE

Research for reliable and patient-specific markers in colorectal cancer (CRC) is based on solid evidence that staging alone is not informative enough. Employing four cellular receptors, we embarked to identify aggressive tumour behaviour and impact of surrogate marker expression on patient prognosis.

METHODS

One-hundred eighty-three CRC patients were enrolled in our investigation that focused on an array of biological markers, namely epidermal growth factor receptor (EGFR), c-Met, focal adhesion kinase (FAK) and CD44v6. Tissue samples, clinicopathological data and patient's follow-up information were collected, and immunohistochemical assays evaluated the levels of the aforementioned molecules. All available data were correlated with tumour grade, stage, patient age, gender and survival.

RESULTS

Expression of all receptors correlated closely with tumour stage (P < 0.01) exhibiting a connection with cancer's invasiveness and progress. Survival also proved to depend significantly on molecular expression (log-rank test for Kaplan-Meier; EGFR P = 0.030, c-Met P = 0.050, FAK P < 0.001, CD44v6 P < 0.001). Stage, FAK and CD44v6 emerged as independent predictors of survival in a stepwise regression analysis (FAK P = 0.001 Exp(B) = 2.517, 95 % confidence interval (CI) = 1.704-5.831 and CD44v6 P = 0.005, Exp(B) = 2.299, 95 % CI = 1.287-4.110). T-stage, nodal metastasis, all metastatic types (N/M) and size correlated with at least one of the receptors or their co-expression. Notably, increased staining for each receptor was followed by statistically significant expression elevation of at least one of the other markers.

CONCLUSIONS

Our results suggest that the selected cellular receptors are suitable for use as biomarkers of survival and tumour progression in CRC. Furthermore, we provide additional evidence for receptor interaction, properly clarifying their importance, which could potentially lead to more effective anti-CRC regimens.

Sphingosine kinase 1 promotes tumor progression and confers malignancy phenotypes of colon cancer by regulating the focal adhesion kinase pathway and adhesion molecules

Studies suggest a tumor-promoting function of sphingosine kinase 1 (SphK1) in some types of human tumors, however, its effect on colon cancer is still unclear. The aims of this study were to investigate the roles of SphK1 in the progression and tumor cell phenotypic changes in colon cancer. Moreover, the focal adhesion kinase (FAK) pathway and the expression of intercellular adhesion molecule‑1 (ICAM‑1) and vascular cell adhesion molecule‑1 (VCAM‑1) were detected to explore the mechanisms of SphK1 action. In this study, the expression of SphK1, FAK and phospho-FAK (p-FAK) was analyzed in 66 surgical specimens of primary colon cancer and matched adjacent normal tissues by immunohistochemistry and western blotting. In addition, N,N-dimethylsphingosine (DMS), SphK1 DNA and shRNA transfection were used to regulate the expression and activity of SphK1 in the LOVO colon cancer cell line. Tumor cell phenotypic changes were analyzed by cell viability, invasion and apoptosis assays. Results showed that the expression of SphK1, FAK and p-FAK in colon cancer tissues were significantly stronger compared to those in matched normal tissues. There was a close correlation between the expression of SphK1 and FAK or p-FAK and the co-expression of SphK1, FAK and p-FAK significantly associated with histological grade, Dukes' stage, lymph node metastasis and distant metastasis. Overexpression of SphK1 after DNA transfection enhanced tumor cell viability and invasiveness, but suppressed cell apoptosis. In contrast, suppression of SphK1 by DMS and shRNA reduced tumor cell viability and invasiveness, but promoted cell apoptosis. The expression of FAK, p-FAK, ICAM-1 and VCAM-1 in LOVO cells were increased with the overexpression of SphK1 but decreased with the suppression of SphK1. These findings indicate that SphK1 regulates tumor cell proliferation, apoptosis and invasion, which ultimately contributes to tumor progression and malignancy phenotype in colon cancer. FAK pathway, ICAM-1 and VCAM-1 may play critical roles in this SphK1‑mediated effect.

Single-cell exome sequencing reveals single-nucleotide mutation characteristics of a kidney tumor

Clear cell renal cell carcinoma (ccRCC) is the most common kidney cancer and has very few mutations that are shared between different patients. To better understand the intratumoral genetics underlying mutations of ccRCC, we carried out single-cell exome sequencing on a ccRCC tumor and its adjacent kidney tissue. Our data indicate that this tumor was unlikely to have resulted from mutations in VHL and PBRM1. Quantitative population genetic analysis indicates that the tumor did not contain any significant clonal subpopulations and also showed that mutations that had different allele frequencies within the population also had different mutation spectrums. Analyses of these data allowed us to delineate a detailed intratumoral genetic landscape at a single-cell level. Our pilot study demonstrates that ccRCC may be more genetically complex than previously thought and provides information that can lead to new ways to investigate individual tumors, with the aim of developing more effective cellular targeted therapies.

Focal adhesion kinase as a cancer therapy target

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that resides at the sites of focal adhesions. The 125 kDa FAK protein is encoded by the FAK gene located on human chromosome 8q24. Structurally, FAK consists of an amino-terminal regulatory FERM domain, a central catalytic kinase domain, and a carboxy-terminal focal adhesion targeting domain. FAK has been shown to be an important mediator of cell adhesion, growth, proliferation, survival, angiogenesis and migration, all of which are often disrupted in cancer cells. Normal tissues have low expression of FAK, while primary and metastatic tumors significantly overexpress this protein. This review summarizes expression of FAK by immunohistochemical staining in different tumor types and presents several FAK inhibition therapy approaches.

p190RhoGEF (Rgnef) promotes colon carcinoma tumor progression via interaction with focal adhesion kinase

Focal adhesion kinase (FAK) functions downstream of integrins and growth factor receptors to promote tumor cell motility and invasion. In colorectal cancer, FAK is activated by amidated gastrin, a protumorigenic hormone. However, it is unclear how FAK receives signals from the gastrin receptor or other G-protein-coupled receptors that can promote cell motility and invasion. The Rho guanine-nucleotide exchange factor p190RhoGEF (Rgnef) binds FAK and facilitates fibroblast focal adhesion formation on fibronectin. Here we report that Rgnef mRNA and protein expression are significantly increased during colorectal tumor progression. In human colon carcinoma cells, Rgnef forms a complex with FAK and upon gastrin stimulation, FAK translocates to newly-forming focal adhesions where it facilitates tyrosine phosphorylation of paxillin. short hairpin (shRNA)-mediated knockdown of Rgnef or FAK, or pharmacological inhibition of FAK activity, is sufficient to block gastrin-stimulated paxillin phosphorylation, cell motility, and invadopodia formation in a manner dependent upon upstream cholecystokinin-2 receptor expression. Overexpression of the C-terminal region of Rgnef (Rgnef-C, amino acid 1,279-1,582) but not Rgnef-CΔFAK (amino acid 1,302-1,582 lacking the FAK binding site) disrupted endogenous Rgnef-FAK interaction and prevented paxillin phosphorylation and cell motility stimulated by gastrin. Rgnef-C-expressing cells formed smaller, less invasive tumors with reduced tyrosine phosphorylation of paxillin upon orthotopic implantation, compared with Rgnef-CΔFAK-expressing cells. Our studies identify Rgnef as a novel regulator of colon carcinoma motility and invasion, and they show that a Rgnef-FAK linkage promotes colon carcinoma progression in vivo.

Phosphorylation of focal adhesion kinase at Tyr397 in gastric carcinomas and its clinical significance

Focal adhesion kinase (FAK) has been implicated in tumorigenesis in various cancers; however, it remains unclear how FAK participates in tumor malignancy in vivo. This study seeks to understand the role of FAK activation in gastric cancer progression. Using immunohistochemical staining and Western blotting, we found that pY397 FAK, an autophosphorylation site on FAK activation, was abundant in the cancerous tissues of 21 of 59 patients with gastric carcinomas. We attempted to correlate clinicopathological parameters, including histological types, TNM staging, and cancer recurrence, with the expression of FAK and pY397 FAK in cancerous tissues. Intriguingly, patients with higher levels of pY397 FAK displayed higher incidences of gastric cancer recurrence after surgery and poor 5-year recurrence-free survival. Furthermore, multivariate analyses showed that pY397 FAK was an independent predictor of gastric cancer recurrence. As a result, expression of pY397 FAK is a significant prognostic factor for the recurrence of gastric cancer. Additionally, in vitro studies showed that overexpression of Y397F, a dominant-negative mutant of FAK, in AGS human gastric carcinoma cells impaired cell migration, invasion, and proliferation compared with cells overexpressing wild-type FAK. Thus, activation of FAK through autophosphorylation at Tyr397 leads to the progression of gastric carcinomas by promoting cell migration, invasion, and proliferation. Collectively, our results have provided valuable insights for the development of novel diagnoses and therapeutic targets for gastric cancer treatments.

Gastrin stimulates the VEGF-A promotor in a human colon cancer cell line

INTRODUCTION

Hypergastrinemia has been observed in patients suffering from colorectal cancer. Vascular endothelial growth factor (VEGF) is known to play a pivotal role in tumour growth. Therefore, we addressed whether gastrin-17-gly and gastrin-17-amide regulate VEGF-A-gene and protein expression.

MATERIALS AND METHODS

Colo-320-cells were stably transfected with a VEGF-Luciferase-reporter gene. Luciferase activity was assessed after stimulation with various gastrin concentrations. Relevant promotor elements were identified by deletion analyses. VEGF protein levels in culture supernatants were quantified by ELISA.

RESULTS

VEGF-A stimulation with gastrin induced a dose- and time-dependent stimulation of luciferase activity. The greatest activities were found 6h after stimulation at concentrations of 10(-)(6)mmol/l. VEGF-promotor expression resulted in significantly (p<0.05) increased VEGF-A protein secretion. These effects were restricted to gastrin-17-amide.

CONCLUSION

Gastrin-17-amide enhances VEGF-A gene and protein expression in Colo320 cells stably transfected with a wild-type CCK-B/gastrin receptor. The induction of VEGF-A transcription and translation may contribute to the carcinogenic effects of gastrin observed in clinical studies. Therefore, CCK-B receptor antagonists may represent a treatment strategy in patients with colorectal cancer.

Evaluation of FAK and Src Expression in Human Benign and Malignant Thyroid Lesions

Focal Adhesion Kinase (FAK) and Src have been reported to regulate tumor growth, invasion, metastasis and angiogenesis. The present study aimed to evaluate by immunohistochemistry the clinical significance of FAK and Src expression in 108 patients with benign and malignant thyroid lesions. Total FAK expression provided a distinct discrimination between malignant and benign (p = 0.00001), as well as between papillary carcinoma and hyperplastic nodules thyroid lesions (p = 0.00005), being also associated with follicular cells' proliferative capacity (p = 0.0003). In malignant thyroid lesions, total FAK expression was associated with tumor size (p = 0.0455), and presence of capsular (p = 0.0102) and lymphatic (p = 0.0173) invasion. Total Src expression was borderline increased in cases of papillary carcinoma compared to hyperplastic nodules (p = 0.0993), being also correlated with tumor size (p = 0.0169). FAK and Src expression was ascribed to a significant extent to the phosphorylated forms of the enzymes, which provided a better discrimination between malignant and benign thyroid lesions. The current data revealed that FAK and to a lesser extent Src expression could be considered of clinical utility in thyroid neoplasia with potential use as therapeutic targets.

Progress in researches about focal adhesion kinase in gastrointestinal tract

Focal adhesion kinase (FAK) is a 125-kDa non-receptor protein tyrosine. Growth factors or the clustering of integrins facilitate the rapid phosphorylation of FAK at Tyr-397 and this in turn recruits Src-family protein tyrosine kinases, resulting in the phosphorylation of Tyr-576 and Tyr-577 in the FAK activation loop and full catalytic FAK activation. FAK plays a critical role in the biological processes of normal and cancer cells including the gastrointestinal tract. FAK also plays an important role in the restitution, cell survival and apoptosis and carcinogenesis of the gastrointestinal tract. FAK is over-expressed in cancer cells and its over-expression and elevated activities are associated with motility and invasion of cancer cells. FAK has been proposed as a potential target in cancer therapy. Small molecule inhibitors effectively inhibit the kinase activity of FAK and show a potent inhibitory effect for the proliferation and migration of tumor cells, indicating a high potential for application in cancer therapy.

Signal transduction by focal adhesion kinase in cancer

Cellular interactions with extracellular matrix play essential roles in tumor initiation, progression and metastasis. Focal adhesion kinase (FAK) is a cytoplasmic tyrosine kinase identified as a key mediator of signaling by integrins, a major family of cell surface receptors for extracellular matrix, as well as other receptors in both normal and cancer cells. FAK is activated by integrins through disruption of an auto-inhibitory intra-molecular interaction between its kinase domain and the amino terminal FERM domain. The activated FAK forms a binary complex with Src family kinases which can phosphorylate other substrates and trigger multiple intracellular signaling pathways to regulate various cellular functions. Subcellular localization of FAK in focal adhesions is essential for FAK signaling, which is another distinguishing feature of the kinase. Integrin-FAK signaling has been shown to activate a number of signaling pathways through phosphorylation and protein-protein interactions to promote tumorigenesis. FAK also plays a prominent role in tumor progression and metastasis through its regulation of both cancer cells and their microenvironments including cancer cell migration, invasion, epithelial to mesenchymal transition, and angiogenesis. More recently, a role for FAK in tumor initiation and progression has been demonstrated directly using xenograft as well as conditional knockout mouse models. In agreement with these experimental data, overexpression and activation of FAK have been found in a variety of human cancers. A number of small molecule inhibitors for FAK have been developed and in various phases of testing for cancer treatments. Overall, the intensive research on FAK signaling in cancer have yielded a wealth of information on this pivotal kinase and these and future studies are leading to potentially novel therapies for cancer.

Inactivating cholecystokinin-2 receptor inhibits progastrin-dependent colonic crypt fission, proliferation, and colorectal cancer in mice

Hyperproliferation of the colonic epithelium, leading to expansion of colonic crypt progenitors, is a recognized risk factor for colorectal cancer. Overexpression of progastrin, a nonamidated and incompletely processed product of the gastrin gene, has been shown to induce colonic hyperproliferation and promote colorectal cancer in mice, but the mechanism of pathogenesis has not been defined. Cholecystokinin-2 receptor (CCK2R) is the primary receptor for cholecystokinin (CCK) and amidated gastrin. Here, we show that Cck2r was expressed in murine colonic crypts and upregulated in the transgenic mice that overexpress human progastrin. Murine deletion of Cck2r abrogated progastrin-dependent increases in colonic proliferation, mucosal thickness, and beta-catenin and CD44 expression in the colon tumor. In addition, either deletion or antagonism of Cck2r resulted in the inhibition of progastrin-dependent increases in progenitors expressing doublecortin and CaM kinase-like-1 (DCAMKL1), stem cells expressing leucine rich repeat-containing G protein-coupled receptor 5 (LgR5), and colonic crypt fission. Furthermore, in the azoxymethane mouse model of colorectal carcinogenesis, Cck2r deletion in human progastrin-overexpressing mice resulted in markedly decreased aberrant crypt foci formation and substantially reduced tumor size and multiplicity. Taken together, these observations indicate that progastrin induces proliferative effects, primarily in colonic progenitor cells, through a CCK2R-dependent pathway. Moreover, our data suggest that CCK2R may be a potential target in the treatment or prevention of colorectal cancer.

Expression and clinical significance of focal adhesion kinase in the two distinct histological types, intestinal and diffuse, of human gastric adenocarcinoma

Focal adhesion kinase (FAK), a non-receptor tyrosine kinase protein, acts as an early modulator of integrin signaling cascade, regulating basic cellular functions. In transformed cells, unopposed FAK signaling has been considered to promote tumor growth, progression and metastasis. The aim of this study was to assess the clinical significance of FAK expression in the two distinct histological types of human gastric neoplasia. FAK expression was assessed immunohistochemically in tumoral samples of 66 gastric adenocarcinoma cases, 30 intestinal and 36 diffuse type, and was statistically analyzed in relation to various clinicopathological characteristics, tumor proliferative capacity and patients' survival. In intestinal type carcinomas, enhanced FAK expression was significantly associated with increased tumor proliferative capacity (P = 0.012). In diffuse type carcinomas, FAK staining intensity was significantly correlated with tumor size (P = 0.026) and disease stage (P = 0.024), presenting also a borderline association with nodal status (P = 0.053). In diffuse type carcinomas, enhanced FAK expression was significantly associated with longer overall survival times (log-rank test, P = 0.014), being also identified as an independent prognostic factor in multivariate analysis (Cox regression, P = 0.016). In contrast, patients with intestinal type tumors and enhanced FAK expression were characterized by shorter overall survival times, without though reaching statistical significance (log-rank test, P = 0.092). The current data support evidence that FAK protein may be considered as a diagnostic and prognostic marker in gastric neoplasia. Further studies conducted on larger clinical samples and highlighting on the distinct impact of the two histological types are warranted to delineate the clinical significance of FAK protein in gastric neoplasia.

Phosphorylation of focal adhesion kinase at Tyrosine 407 negatively regulates Ras transformation of fibroblasts

Focal adhesion kinase (FAK) mediates signal transduction in response to multiple extracellular inputs, via tyrosine phosphorylation at specific residues. We recently reported that FAK Tyr-407 phosphorylation negatively regulates the enzymatic and biological activities of FAK, unlike phosphorylation of other tyrosine residues. In this study, we further investigated the effect of FAK Tyr-407 phosphorylation on cell transformation. We found that FAK Tyr-407 phosphorylation was lower in H-Ras transformed NIH3T3 and K-Ras transformed rat-2 fibroblasts than in the respective untransformed control cells. Consistently, FAK Tyr-407 phosphorylation was decreased in parallel with cell transformation in H-Ras-inducible NIH3T3 cells and increased during trichostatin A-induced detransformation of both K-Ras transformed rat-2 fibroblasts and H-Ras transformed NIH3T3 cells. In addition, overexpression of a phosphorylation-mimicking FAK Tyr-407 mutant inhibited morphological transformation of H-Ras-inducible NIH3T3 cells and inhibited invasion activity and anchorage-independent growth of H-Ras-transformed NIH3T3 cells. Taken together, these data strongly suggest that FAK Tyr-407 phosphorylation negatively regulates transformation of fibroblasts.

Focal adhesion kinase: a promising target for anticancer therapy

Focal adhesion kinase (FAK) is a protein tyrosine kinase acting as an early modulator of the integrin signalling cascade, thus regulating various basic cellular functions. In transformed cells, upregulation of FAK protein expression and uncontroled signalling were held responsible for the promotion of malignant phenotypic characteristics, as well as resistance to chemotherapy and radiotherapy. Direct FAK targeting resulted in the inhibition of the malignant phenotype of cancer cells, whereas increased apoptotic rates of cancer cells, either used alone or in combination with conventional chemotherapeutic agents, radiotherapy or hormonal therapy. Furthermore, drugs used in cancer chemotherapy, besides their basic mode of action, were also shown to act through altering FAK signalling. Finally, positive results were noted by the transfection of cancer cells with fak mutants or genes that suppress FAK expression or activity, such as phosphatase and tensin homolog deleted on chromosome Ten (PTEN), ribonucleotide reductase M1 polypeptide (RRM1) and melanoma differentiation-associated gene-7 (mda-7). The purpose of this article is a comprehensive review of the existing data on the possible use of FAK targeting in anticancer therapy.

Focal adhesion kinase and p53 signaling in cancer cells

The progression of human cancer is characterized by a process of tumor cell motility, invasion, and metastasis to distant sites, requiring the cancer cells to be able to survive the apoptotic pressures of anchorage-independent conditions. One of the critical tyrosine kinases linked to these processes of tumor invasion and survival is the focal adhesion kinase (FAK). FAK was first isolated from human tumors, and FAK mRNA was found to be upregulated in invasive and metastatic human breast and colon cancer samples. Recently, the FAK promoter was cloned, and it has been found to contain p53-binding sites. p53 inhibits FAK transcription, and recent data show direct binding of FAK and p53 proteins in vitro and in vivo. The structure of FAK and p53, proteins interacting with FAK, and the role of FAK in tumorigenesis and FAK-p53-related therapy are reviewed. This review focuses on FAK signal transduction pathways, particularly on FAK and p53 signaling, revealing a new paradigm in cell biology, linking signaling from the extracellular matrix to the nucleus.