Rapid tyrosine phosphorylation of focal adhesion kinase, paxillin, and p130Cas by gastrin in human colon cancer cells

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.

Gastrin stimulates pancreatic cancer cell directional migration by activating the Gα12/13-RhoA-ROCK signaling pathway

The mechanism by which gastrin promotes pancreatic cancer cell metastasis is unclear. The process of directing polarized cancer cells toward the extracellular matrix is principally required for invasion and distant metastasis; however, whether gastrin can induce this process and its underlying mechanism remain to be elucidated. In this study, we found that gastrin-induced phosphorylation of paxillin at tyrosine 31/118 and RhoA activation as well as promoted the metastasis of PANC-1 cancer cells. Depletion of Gα12 and Gα13 inhibited the phosphorylation of paxillin and downstream activation of GTP-RhoA, blocked the formation and aggregation of focal adhesions and facilitated polarization of actin filaments induced by gastrin. Suppression of RhoA and ROCK also exhibited identical results. Selective inhibition of the CCKBR-Gα12/13-RhoA-ROCK signaling pathway blocked the reoriented localization of the Golgi apparatus at the leading edge of migrated cancer cells. YM022 and Y-27632 significantly suppressed hepatic metastasis of orthotic pancreatic tumors induced by gastrin in vivo. Collectively, we demonstrate that gastrin promotes Golgi reorientation and directional polarization of pancreatic cancer cells by activation of paxillin via the CCKBR-Gα12/13-RhoA-ROCK signal pathway.

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.

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.

PTEN inhibits the invasion and metastasis of gastric cancer via downregulation of FAK expression

The tumor suppressor gene phosphatase and tensin homolog (PTEN) is essential in inhibiting tumor growth and metastasis. However, the mechanism by which PTEN restricts gastric cancer progression and metastasis remains largely elusive. Here we demonstrated that PTEN overexpression or knockdown in gastric cancer cells led to the downregulation or upregulation of focal adhesion kinase (FAK), and decreased or increased cell invasion, respectively. Moreover, FAK overexpression could rescue the inhibition of cell invasion by PTEN. These results were further confirmed in orthotropic gastric cancer nude mice model. In addition, in human gastric cancer tissues, PTEN protein level was conversely correlated with FAK protein level. Mechanistically, we found that PTEN inhibited PI3K/NF-κB pathway and inhibited the DNA binding of NF-κB on FAK promoter. Taken together, our data reveal a novel mechanism that PTEN inhibits the growth and invasion of gastric cancer via the downregulation of FAK expression and suggest that exploiting PTEN/PI3K/NF-κB/FAK axis is a promising approach to treat gastric cancer metastasis.

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.

Hydrogen peroxide activates focal adhesion kinase and c-Src by a phosphatidylinositol 3 kinase-dependent mechanism and promotes cell migration in Caco-2 cell monolayers

Recent studies showed that c-Src and phosphatidylinositol 3 (PI3) kinase mediate the oxidative stress-induced disruption of tight junctions in Caco-2 cell monolayers. The present study evaluated the roles of PI3 kinase and Src kinase in the oxidative stress-induced activation of focal adhesion kinase (FAK) and acceleration of cell migration. Oxidative stress, induced by xanthine and xanthine oxidase system, rapidly increased phosphorylation of FAK on Y397, Y925, and Y577 in the detergent-insoluble and soluble fractions and increased its tyrosine kinase activity. The PI3 kinase inhibitors, wortmannin and LY294002, and the Src kinase inhibitor, 4-amino-5[chlorophyll]-7-[t-butyl]pyrazolo[3-4-d]pyrimidine, attenuated tyrosine phosphorylation of FAK. Oxidative stress induced phosphorylation of c-Src on Y418 by a PI3 kinase-dependent mechanism, whereas oxidative stress-induced activation of PI3 kinase was independent of Src kinase activity. Hydrogen peroxide accelerated Caco-2 cell migration in a concentration-dependent manner. Promotion of cell migration by hydrogen peroxide was attenuated by LY294002 and PP2. Reduced expression of FAK by siRNA attenuated hydrogen peroxide-induced acceleration of cell migration. The expression of constitutively active c-Src(Y527F) enhanced cell migration, whereas the expression of dominant negative c-Src(K296R/Y528F) attenuated hydrogen peroxide-induced stimulation of cell migration. Oxidative stress-induced activation of c-Src and FAK was associated with a rapid increase in the tyrosine phosphorylation and the levels of paxillin and p130(CAS) in actin-rich, detergent-insoluble fractions. This study shows that oxidative stress activates FAK and accelerates cell migration in an intestinal epithelium by a PI3 kinase- and Src kinase-dependent mechanism.

CAS proteins in normal and pathological cell growth control

Proteins of the CAS (Crk-associated substrate) family (BCAR1/p130Cas, NEDD9/HEF1/Cas-L, EFS/SIN and CASS4/HEPL) are integral players in normal and pathological cell biology. CAS proteins act as scaffolds to regulate protein complexes controlling migration and chemotaxis, apoptosis, cell cycle, and differentiation, and have more recently been linked to a role in progenitor cell function. Reflecting these complex functions, over-expression of CAS proteins has now been strongly linked to poor prognosis and increased metastasis in cancer, as well as resistance to first-line chemotherapeutics in multiple tumor types including breast and lung cancers, glioblastoma, and melanoma. Further, CAS proteins have also been linked to additional pathological conditions including inflammatory disorders, Alzheimer's and Parkinson's disease, as well as developmental defects. This review will explore the roles of the CAS proteins in normal and pathological states in the context of the many mechanistic insights into CAS protein function that have emerged in the past decade.

A combinatorial approach for the design of complementarity-determining region-derived peptidomimetics with in vitro anti-tumoral activity

The great success of therapeutic monoclonal antibodies has fueled research toward mimicry of their binding sites and the development of new strategies for peptide-based mimetics production. Here, we describe a new combinatorial approach for the production of peptidomimetics using the complementarity-determining regions (CDRs) from gastrin17 (pyroEGPWLEEEEEAYGWMDF-NH(2)) antibodies as starting material for cyclic peptide synthesis in a microarray format. Gastrin17 is a trophic factor in gastrointestinal tumors, including pancreatic cancer, which makes it an interesting target for development of therapeutic antibodies. Screening of microarrays containing bicyclic peptidomimetics identified a high number of gastrin binders. A strong correlation was observed between gastrin binding and overall charge of the peptidomimetic. Most of the best gastrin binders proceeded from CDRs containing charged residues. In contrast, CDRs from high affinity antibodies containing mostly neutral residues failed to yield good binders. Our experiments revealed essential differences in the mode of antigen binding between CDR-derived peptidomimetics (K(d) values in micromolar range) and the parental monoclonal antibodies (K(d) values in nanomolar range). However, chemically derived peptidomimetics from gastrin binders were very effective in gastrin neutralization studies using cell-based assays, yielding a neutralizing activity in pancreatic tumoral cell lines comparable with that of gastrin-specific monoclonal antibodies. These data support the use of combinatorial CDR-peptide microarrays as a tool for the development of a new generation of chemically synthesized cyclic peptidomimetics with functional activity.

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.

Designing antibodies for the inhibition of gastrin activity in tumoral cell lines

Gastrin and its derivatives are becoming important targets for immunotherapy of pancreatic, gastric and colorectal tumors. This study was conducted to design antibodies able to block gastrin binding to the gastrin/cholecystokinin-2 (CCK-2) receptor in order to delay tumor growth. The authors have used different gastrin molecules, combined with the diphtheria toxoid, to generate and select human single chain variable fragments (scFvs) as well as mouse monoclonal antibodies and scFvs against different regions of gastrin. There was a remarkable conservation in the antibody repertoire against gastrin, independently of the approach and the species. The germlines most frequently used in gastrin antibody formation were identified. Three different epitopes were identified in the gastrin molecule. The resulting mouse monoclonal antibodies and scFvs were analyzed for gastrin neutralization using Colo 320 WT cells, which overexpress the CCK-2 receptor. The gastrin neutralizing activity assay showed that N-terminal specific mouse monoclonal antibodies were more efficient to inhibit proliferation of Colo 320 WT cells than the anti-C terminal antibodies. Moreover, the human antigastrin scFvs obtained in this study inhibited significantly the proliferation of Colo 320 tumoral cells. These findings should contribute to a more rational design of antibody-based antigastrin therapies in cancer, including passive administration of human antibodies with blocking activity.

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.

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

Focal adhesion kinase (FAK) is suggested to be intimately involved in the progression of malignancies. Our previous research has demonstrated that activation of cholecystokinin-2 receptor (CCK2R) by gastrin stimulates a rapid activation of FAK pathway in human colon cancer cells. The purpose of this study is to determine the role of CCK2R and FAK in the progression of colon cancer. In this study, matched tissue samples of primary colon cancer and adjacent normal colon mucosa from the same patient were collected from 45 patients with colon cancer undergoing surgical resection. The gastrin expression was detected using reverse transcription polymerase chain reaction (RT-PCR). The CCK2R expression was examined by in situ hybridization and RT-PCR. The expression of FAK and phosphorylated FAK at tyrosine 397 (phospho-FAK) were detected using immunohistochemistry and immunoblotting. Colo320 and SW787, 2 colon cancer cell lines with or without CCK2R expression, were recruited in this study. Antisense oligonucleotide of FAK was used to block the expression of FAK. Invasiveness and motility of colon cancer cells were detected by Boyden chamber. In this series, enhanced expression of gastrin, CCK2R, FAK and phospho-FAK were observed in colon cancer tissues. CCK2R expression correlated with expression of phospho-FAK. Coexpression of CCK2R and phospho-FAK associated with invasion and lymph node metastasis. Increased invasion and motility was induced by gastrin in Colo320 cells. Overexpression of CCK2R by stable transfection of CCK2R plasmid amplified this increase and incubation with 1 microM L-365,260, a specific CCK2R antagonist, completely inhibited the effect of gastrin. FAK antisense largely blocked the increase of invasion and motility in Colo320 cells. Our data represent the evidence for the CCK2R regulating invasion and motility of colon cancer cells, and support a role of CCK2R in the progression of colon cancer. FAK play a critical role in this CCK2R-mediated effect.

Effects of gastrin 17 on beta-catenin/Tcf-4 pathway in Colo320WT colon cancer cells

AIM

To explore the effect of gastrin 17 (G17) on beta-catenin/T cell factor-4 (Tcf-4) signaling in colonic cancer cell line Colo320WT.

METHODS

The pCR3.1/GR plasmid, which expresses gastrin receptor, cholecystokinin-2 receptor (CCK-2R), was transfected into a colonic cancer cell line Colo320 by Lipofectamine (TM)2000 and the stably expressing CCK-2R clones were screened by G418. The expression levels of gastrin receptor in the Colo320 and the transfected Colo320WT cell line were assayed by RT-PCR. Colo320WT cells were treated with G17 in a time-dependent manner (0, 1, 6, 12, 24 and 48 h), then with L365,260 (Gastrin(17) receptor blocker) for 30 min, and with G17 again for 12 h or L365,260 for 12 h. Expression levels of beta-catenin in a TX-100 soluble fraction and TX-100 insoluble fraction of Colo320WT cells treated with G17 were detected by co-immuniprecipation and Western blot. Immunocytochemistry was used to examine the distribution of beta-catenin in CoLoWT320 cells. Expression levels of c-myc and cyclin D1 in Colo320WT cells treated with G17 were assayed by Western blot.

RESULTS

Expression levels of beta-catenin in the TX-100 solution fraction decreased apparently in a time-dependent fashion and reached the highest level after G17 treatment for 12 h, while expression levels of beta-catenin in the TX-100 insoluble fraction were just on the contrary. Immunocytochemistry showed that beta-catenin was translocated from the cell membranes into the cytoplasm and nucleus under G17 treatment. Expression levels of c-myc and cyclin D1 in the G17-treated Colo320WT cells were markedly higher compared to the untreated Colo320WT cells. In addition, the aforementioned G17-stimulated responses were blocked by L365,260.

CONCLUSION

Gastrin17 activates beta-catenin/Tcf-4 signaling in Colo320WT cells, thereby leading to over-expression of c-myc and cyclin D1.

Cholecystokinin and gastrin receptors

Cholecystokinin and gastrin receptors (CCK1R and CCK2R) are G protein-coupled receptors that have been the subject of intensive research in the last 10 years with corresponding advances in the understanding of their functioning and physiology. In this review, we first describe general properties of the receptors, such as the different signaling pathways used to exert short- and long-term effects and the structural data that explain their binding properties, activation, and regulation. We then focus on peripheral cholecystokinin receptors by describing their tissue distribution and physiological actions. Finally, pathophysiological peripheral actions of cholecystokinin receptors and their relevance in clinical disorders are reviewed.

Correlation between the expressions of gastrin, somatostatin and cyclin and cyclin-depend kinase in colorectal cancer

AIM

To explore the correlation between the expressions of gastrin (GAS), somatostatin (SS) and cyclin, cyclin-dependent kinase (CDK) in colorectal cancer, and to detect the specific regulatory sites where gastrointestinal hormone regulates cell proliferation.

METHODS

Seventy-nine resected large intestine carcinomatous specimens were randomly selected. Immunohistochemical staining for GAS, SS, cyclin D1, cyclin E, cyclin A, cyclin B1, CDK2 and CDK4 was performed according to the standard streptavidin-biotin-peroxidase (S-P) method. According to the semi-quantitative integral evaluation, SS and GAS were divided into high, middle and low groups. Cyclin D1, cyclin E, cyclin A, cyclin B1, CDK2, CDK4 expressions in the three GAS and SS groups were assessed.

RESULTS

The positive expression rate of cyclin D1 was significantly higher in high (78.6%, 11/14) and middle GAS groups (73.9%, 17/23) than in low GAS group (45.2%, 19/42) (P<0.05, c2(high vs low) = 4.691; P<0.05, c2(middle vs low) = 4.945). The positive expression rate of cyclin A was significantly higher in high (100%, 14/14) and middle GAS groups (82.6%, 19/23) than in low GAS group (54.8%, 23/42) (P<0.01, c2(high vs low) = 9.586; P<0.05, c2(middle vs low) = 5.040). The positive expression rate of CDK2 was significantly higher in high (92.9%, 13/14) and middle GAS groups (87.0%, 20/23) than in low GAS group (50.0%, 21/42) (P<0.01, c2(high vs low) = 8.086; P<0.01, c2(middle vs low) = 8.715). The positive expression rate of CDK4 was significantly higher in high (78.6%, 11/14) and middle GAS groups (78.3%, 18/23) than in low GAS group (42.9%, 18/42) (P<0.05, c2(high vs low) = 5.364; P<0.01, c2(middle vs low) = 7.539). The positive expression rate of cyclin E was prominently higher in low SS group (53.3%, 24/45) than in high (9.1%, 1/11) and middle (21.7%, 5/23) SS groups (P<0.05, c2(high vs low) = 5.325; P<0.05, c2(middle vs low) = 6.212). The positive expression rate of CDK2 was significantly higher in low SS group (77.8%, 35/45) than in high SS group (27.3%, 3/11) (P<0.01, c2(high vs low) = 8.151). There was a significant positive correlation between the integral ratio of GAS to SS and the semi-quantitative integral of cyclin D1, cyclin E, cyclin A, CDK2, CDK4 (P<0.05, (D1)r(s) = 0.252; P<0.01, (E)r(s) = 0.387; P<0.01, (A)r(s) = 0.466; P<0.01, (K2)r(s) = 0.519; P<0.01, (K4)r(s) = 0.434).

CONCLUSION

The regulation and control of gastrin, SS in colorectal cancer cell growth may be directly related to the abnormal expressions of cyclins D1, A, E, and CDK2, CDK4. The regulatory site of GAS in the cell cycle of colorectal carcinoma may be at the G(1), S and G(2) phases. The regulatory site of SS may be at the entrance of S phase.

Phosphoproteomic analysis of the effect of cyclo-[His-Pro] dipeptide on PC12 cells

The effects of dipeptide cyclo-[His-Pro] (CHP), known to participate in the appetite behavior and food intake control, have been investigated using PC12 cells in culture as model system. We found that only in the presence of experimental conditions that cause cellular stress the cyclic dipeptide affect cellular proliferation and protects from apoptosis. It greatly enhances the phosphorylation of hsp27, alpha-B-crystallin, Cdc2, and p-38 MAPK, whereas it decreases the phosphorylation of MEK1, Cav 2, GSK3a, PKB/Akt, PKCdelta, PKCgamma, and Erk2. PKA and PKG are involved in ERK1/2 deactivation via a receptor that appears to be dually coupled to Gs and Gq protein subfamilies.

Relationship between expression of gastrin, somatostatin mRNA and cell apoptosis and Bcl-2, Bax in large intestinal carcinoma

AIM: To explore the correlations the between expression of somatostatin (SS), gastrin (GAS) mRNA and cell apoptosis index (AI) and Bcl-2, Bax in large intestinal cancer.

METHODS: The expression of GAS and SS genes were detected in 62 colorectal cancer patients by nested reverse transcription polymerase chain reaction (RT-PCR), and the apoptosis of the cells was detected by TUNEL method. The protein expression of,Bcl-2, Bax, GAS, and SS were detected using immunohistochemical staining (S-P method).

RESULTS: The expression of GAS and SS mRNA and protein were basically consistent. The AI in SS high and moderate expression patients with large intestinal cancer was remarkably higher than that in SS low expression ones (q = 5.06, 3.95, both P < 0.01), while it was just opposite in GAS positive patients (q = 6.66, 6.33, P < 0.01). The positive rates of Bax and Bcl-2 expression had significant difference between SS (or GAS) high, moderate and low expression patients with large intestinal cancer (Bax: χ² = 9.24, 6.91, P < 0.05; Bcl-2: χ² = 7.17, 13.83, P < 0.05). The positive rate of Bax expression in SS high (80%, 8/10) and moderate (76.5%, 13/17) expression patients was notably higher than that in the low expression ones (40.0%, 14/35) (χ² = 5.24, 6.09, P < 0.05), but the rate of Bcl-2 expression was just opposite (χ² = 4.71, 4.70, P < 0.05). The positive rate of Bcl-2 expression in GAS high (90.9%,10/11) and moderate expression patients (86.7%,13/15) was markedly higher than that in the low expression ones (44.4%, 16/36) (χ² = 5.60, 7.69, P < 0.05), but the positive rate of Bax expression in GAS high expression patients (27.3%, 3/8) was obviously lower than that in the low expression ones (69.4%, 25/36) (χ² = 4.59, P < 0.05). Bax expression was not significantly different between moderate and low GAS positive patients. The value of GAS/SS was positively correlated with Bcl-2 expression (r = 0.34, P < 0.01), but negatively with the AI value and Bax expression (r = －0.546, P < 0.01; r = －0.299, P < 0.05).

CONCLUSION: GAS and SS play important roles in the regulation and control of cell apoptosis in large intestinal carcinoma, and the mechanism may be related to the aberrant expression of Bcl-2 and Bax.

Valine-286 residue in the third intracellular loop of the cholecystokinin 2 receptor exerts a pivotal role in cholecystokinin 2 receptor mediated intracellular signal transduction in human colon cancer cells

Although expression of the gastrin/cholecystokinin-2 receptor (CCK2R) is widely reported in human colorectal cancer, little is known on its role in mediating mature amidated gastrin (gastrin-17 amide, G-17) induced intracellular signal transduction in colon cancer cells. The purpose of this study was to explore the intracellular events of colorectal cancer cells after gastrin binding to CCK2R. Meanwhile, the influence of a natural point mutation 286V-->F in the third intracellular loop of CCK2R on gastrin-envoked intracellular signal transduction was also investigated. Firstly, Colo320 cells were stably transfected with wild type (Colo320 WT) and mutant CCK2R (Colo320 M), respectively. The intracellular signal transduction events in response to gastrin were investigated in both Colo320 WT and Colo320 M cells. In Colo320 WT cells, G-17 induced formation of intracellular cyclic AMP and inositol 1,4,5-trisphosphate, and stimulated intracellular calcium mobilization. G-17 also stimulated tyrosine phosphorylation of ERKl/2, p38, FAK, and paxillin, and up-regulated the mRNA expression of early response gene c-Jun and c-Fos. However, G-17 inhibited proliferation and induced apoptosis in Colo320 WT cells. Mutation 286V-->F in the third intracellular loop of CCK2R blocked G-17 induced biological without affecting binding affinity of CCK2R to G-17. Our results suggest that activation of CCK2R by gastrin stimulates heterotrimeric G-protein Gq and G(12/13) mediated intracellular signal transduction pathway in colon cancer cells. The valine-287 residue in third intracellular loop of CCK2R plays a pivotal role in CCK2R mediated intracellular signal transduction.

Expression and significance of phosphorylated focal adhesion kinase in colon carcinoma

AIM: To investigate the expression of phosphorylated focal adhesion kinase (phospho-FAK) and its signific-ance in human colon carcinoma.

METHODS: The phospho-FAK (including FAK) expre-ssion was detected by Western bloting in 20 cases of colon carcinoma and their corresponding para-cancer tissues.

RESULTS: The positive rate of FAK expression in the cancer tissues was significantly higher than that in the corresponding normal tissues (95% vs 60%, χ² = 5.16, P <0.05). The mean level of FAK expression in the cancer tissues was 0.482±0.150, while the mean level of expression in the normal tissue was 0.269±0.015 (t = 6.39, P <0.01). The positive rate of Tyr-397 FAK protein expression in the cancer tissues was 90%, while the positive rate in the corresponding normal tissues was only 20% (χ² = 17.1, P <0.01). The mean level of Tyr-397 FAK protein expression in the cancer tissue was notably higher than that in the corresponding para-cancer tissues (0.385±0.021 vs 0.110±0.005, t = 54.23, P <0.01).

CONCLUSION: The up-regulation of FAK expression, especially Tyr-397 FAK protein expression, may play an important role in the tumorigenesis and progression of colon carcinoma.

Myotubularin phosphoinositide phosphatases, protein phosphatases, and kinases: their roles in junction dynamics and spermatogenesis

Spermatogenesis in the seminiferous epithelium of the mammalian testis is a dynamic cellular event. It involves extensive restructuring at the Sertoli-germ cell interface, permitting germ cells to traverse the epithelium from basal to adluminal compartment. As such, Sertoli-germ cell actin-based adherens junctions (AJ), such as ectoplasmic specializations (ES), must disassemble and reassemble to facilitate this event. Recent studies have shown that AJ dynamics are regulated by intricate interactions between AJ integral membrane proteins (e.g., cadherins, alpha6beta1 integrins and nectins), phosphatases, kinases, adaptors, and the underlying cytoskeleton network. For instance, the myotubularin (MTM) phosphoinositide (PI) phosphatases, such as MTM related protein 2 (MTMR2), can form a functional complex with c-Src (a non-receptor protein tyrosine kinase). In turn, this phosphatase/kinase complex associates with beta-catenin, a constituent of the N-cadherin/beta-catenin functional unit at the AJ site. This MTMR2-c-Src-beta-catenin complex apparently regulates the phosphorylation status of beta-catenin, which determines cell adhesive function conferred by the cadherin-catenin protein complex in the seminiferous epithelium. In this review, we discuss the current status of research on selected phosphatases and kinases, and how these proteins potentially interact with adaptors at AJ in the seminiferous epithelium to regulate cell adhesion in the testis. Specific research areas that are open for further investigation are also highlighted.

Mechanisms for the apoptosis of small cell lung cancer cells induced by anti-GD2 monoclonal antibodies: roles of anoikis

Anti-GD2 ganglioside antibodies could be a promising, novel therapeutic approach to the eradication of human small cell lung cancers, as anti-GD2 monoclonal antibodies (mAbs) induced apoptosis of small cell lung cancer cells in culture. In this study, we analyzed the mechanisms for the apoptosis of these cells by anti-GD2 mAbs and elucidated the mechanisms by which apoptosis signals were transduced via reduction in the phosphorylation levels of focal adhesion kinase (FAK) and the activation of a MAPK family member, p38, upon the antibody binding. Knock down of FAK resulted in apoptosis and p38 activation. The inhibition of p38 activity blocked antibody-induced apoptosis, indicating that p38 is involved in this process. Immunoprecipitation-immunoblotting analysis of immune precipitates with anti-FAK or anti-integrin antibodies using an anti-GD2 mAb revealed that GD2 could be precipitated with integrin and/or FAK. These results suggested that GD2, integrin, and FAK form a huge molecular complex across the plasma membrane. Taken together with the fact that GD2+ cells showed marked detachment from the plate during apoptosis, GD2+ small cell lung cancer cells seemed to undergo anoikis through the conformational changes of integrin molecules and subsequent FAK dephosphorylation.

Correlation between expression of gastrin, somatostatin and cell apoptosis regulation gene bcl-2/bax in large intestine carcinoma

AIM: To explore the correlation between expression of somatostatin (SS), gastrin (GAS) and cell apoptosis regulation gene bcl-2/bax in large intestine carcinoma.

METHODS: Sixty-two large intestine cancer tissue samples were randomly and retrospectively selected from patients with large intestine carcinoma. Immunohistochemical staining for bcl-2, bax, GAS, SS was performed according to the standard streptavidin-biotin-peroxidase (S-P) method. According to the semi-quantitative integral evaluation, SS and GAS were divided into three groups as follows. Scores 1-3 were defined as the low expression group, 4-8 as the intermediate expression group, 9-16 as the high expression group. Bax and bcl-2 protein expressions in different GAS and SS expression groups of large intestine carcinoma were assessed.

RESULTS: The positive expression rate of bax had a prominent difference between SS and GAS high, intermediate and low expression groups (P<0.05, χ²_SS = 9.246; P<0.05, χ²_GAS = 6.981). The positive expression rate of bax in SS high (80.0%, 8/10) and intermediate (76.5%, 13/17) expression groups was higher than that in low expression group (40.0%, 14/35) (P<0.05, χ²_{high vs low} = 5.242; P<0.05,χ²_{middle vs low} = 6.097). The positive expression rate of bax in GAS high expression group (27.3%, 3/8) was lower than that in low expression group (69.4%, 25/36) (P<0.05, χ² = 4.594). However, bax expression in GAS intermediate expression group (46.7%, 7/15) was lower than that in low expression group, but not statistically significant. The positive expression rate of bcl-2 had a prominent difference between SS and GAS high, intermediate and low expression groups (P<0.05, χ²_SS = 7.178; P<0.05, χ²_GAS = 13.831). The positive expression rate of bcl-2 in GAS high (90.9%, 10/11) and intermediate (86.7%, 13/15) expression groups was higher than that in low expression group (44.4%, 16/36) (P<0.05, χ²_{high vs low} = 5.600; P<0.05, χ²_{middle vs low} = 7.695). However, the positive expression rate of bcl-2 in SS high (40.0%, 4/10) and intermediate (47.1%, 8/9) expression groups was lower than that in low expression group (77.1%, 27/35) (P<0.05, χ²_{high vs low} = 4.710; P<0.05, χ²_{middle vs low} = 4.706). There was a significant positive correlation between the integral ratio of GAS to SS and the integral of bcl-2 (P<0.01, r = 0.340). However, there was a negative correlation between the integral ratio of GAS to the SS and bax the integral of (P<0.05, r = -0.299).

CONCLUSION: The regulation and control of gastrin, somatostatin in cell apoptosis of large intestine carcinoma may be directly related to the abnormal expression of bcl-2, bax.

Paxillin: adapting to change

Molecular scaffold or adaptor proteins facilitate precise spatiotemporal regulation and integration of multiple signaling pathways to effect the optimal cellular response to changes in the immediate environment. Paxillin is a multidomain adaptor that recruits both structural and signaling molecules to focal adhesions, sites of integrin engagement with the extracellular matrix, where it performs a critical role in transducing adhesion and growth factor signals to elicit changes in cell migration and gene expression.