Inhibitory effects of a luteinizing hormone-releasing hormone agonist on basal and epidermal growth factor-induced cell proliferation and metastasis-associated properties in human epidermoid carcinoma A431 cells

The effects of CD148 Q276P/R326Q polymorphisms in A431D epidermoid cancer cell proliferation and epidermal growth factor receptor signaling

BACKGROUND

CD148 is a transmembrane protein tyrosine phosphatase that is expressed in multiple cell types. Previous studies have shown that CD148 dephosphorylates growth factor receptors and their signaling molecules, including EGFR and ERK1/2, and negatively regulates cancer cell growth. Furthermore, research of clinical patients has shown that highly linked CD148 gene polymorphisms, Gln276Pro (Q276P) and Arg326Gln (R326Q), are associated with an increased risk of several types of cancer. However, the biological effects of these missense mutations have not been studied.

AIM

We aimed to determine the biological effects of CD148 Q276P/R326Q mutations in cancer cell proliferation and growth factor signaling, with emphasis on EGFR signaling.

METHODS

CD148 forms, wild-type (WT) or Q276P/R326Q, were retrovirally introduced into A431D epidermoid carcinoma cells that lacks CD148 expression. The stable cells that express comparable levels of CD148 were sorted by flow cytometry. A431D cells infected with empty retrovirus was used as a control. CD148 localization, cell proliferation rate, EGFR signaling, and the response to thrombospondin-1 (TSP1), a CD148 ligand, were assessed by immunostaining, cell proliferation assay, enzyme-linked immunosorbent assay, and Western blotting.

RESULTS

Both CD148 forms (WT, Q276P/R326Q) were distributed to cell surface and all three cell lines expressed same level of EGFR. Compared to control cells, the A431D cells that express CD148 forms showed significantly lower cell proliferation rates. EGF-induced EGFR and ERK1/2 phosphorylation as well as cell proliferation were also significantly reduced in these cells. Furthermore, TSP1 inhibited cell proliferation in CD148 (WT, Q276P/R326Q)-expressing A431D cells, while it showed no effects in control cells. However, significant differences were not observed between CD148 WT and Q276P/R326Q cells.

CONCLUSION

Our data demonstrates that Q276P/R326Q mutations do not have major effects on TSP1-CD148 interaction as well as on CD148's cellular localization and activity to inhibit EGFR signaling and cell proliferation.

Antcin K, an Active Triterpenoid from the Fruiting Bodies of Basswood-Cultivated Antrodia cinnamomea, Inhibits Metastasis via Suppression of Integrin-Mediated Adhesion, Migration, and Invasion in Human Hepatoma Cells

Previous research demonstrated that the ethyl acetate extract from Antrodia cinnamomea suppresses the invasive potential of human breast and hepatoma cells, but the effective compounds are not identified. The main bioactive compounds of A. cinnamomea are ergostane-type triterpenoids, and the content of antcin K is the highest. The objective of this study was to evaluate the antimetastatic activity and mechanisms of antcin K purified from the fruiting body of basswood-cultivated A. cinnamomea on human liver cancer Hep 3B cells. The results showed that adhesion, migration, and invasion of Hep 3B cells were effectively inhibited by antcin K within 24 h of treatment. Antcin K not only reduced the protein expression and activity of MMP-2 and MMP-9 but also down-regulated vimentin and up-regulated E-cadherin in Hep 3B cells. In depth investigation for the molecular mechanism revealed that antcin K could reduce the protein expression of integrin β1, β3, α5, and αv and suppress phosphorylation of FAK, Src, PI3K, AKT, MEK, ERK, and JNK. These results suggested that antcin K was able to inhibit the metastasis of human hepatoma cells through suppression of integrin-mediated adhesion, migration, and invasion. Coupled with these findings, antcin K has a good potential to reduce the risk of liver cancer metastasis.

Paris saponin VII inhibits metastasis by modulating matrix metalloproteinases in colorectal cancer cells

Metastasis is the main cause of mortality of patients with cancer-related disease. Targeting the process of metastasis has been proposed as a potential strategy in cancer treatment. Trillium tschonoskii Maxim., a traditional Chinese medicine, is used for the treatment of numerous diseases, including cancer. The current study aimed to determine the anti-metastatic effect of Paris saponin VII (PS VII), which was extracted from T. tschonoskii Maxim., using SW620 and LoVo cells, two human metastatic colorectal cancer (CRC) cell lines. The present study conducted cell attachment, wound healing and migration assays to detect the anti-metastatic effects of PS VII on colorectal cells. In addition, gelatin zymography assay and western blot analysis were used to detect the possible mechanisms involved. The results of this study demonstrated that PS VII significantly suppresses the viability, attachment, migration and invasive abilities of CRC cells in a concentration-dependent manner. In addition, PS Ⅶ reduced the expression levels and activity of matrix metalloproteinase (MMP)-2 and MMP-9. These data indicate that PS VII reduces the metastatic capability of CRC cells, possibly via the downregulation of the expression and activity of MMP-2 and MMP-9. These results demonstrate a novel therapeutic potential for PS VII in anti-metastatic therapy.

Deguelin inhibits the migration and invasion of U-2 OS human osteosarcoma cells via the inhibition of matrix metalloproteinase-2/-9 in vitro

Osteosarcoma is the most common malignant primary bone tumor in children and young adults and lung metastasis is the main cause of death in those patients. Deguelin, a naturally occurring rotenoid, is known to be an Akt inhibitor and to exhibit cytotoxic effects, including antiproliferative and anticarcinogenic activities, in several cancers. In the present study, we determined if deguelin would inhibit migration and invasion in U-2 OS human osteosarcoma cells. Deguelin significantly inhibited migration and invasion of U-2 OS human osteosarcoma cells which was associated with a reduction of activities of matrix metalloproteinases-2 (MMP-2) and matrix metalloproteinases-9 (MMP-9). Furthermore, results from western blotting indicated that deguelin decreased the cell proliferation and cell growth-associated protein levels, such as SOS1, PKC, Ras, PI3K, p-AKT(Ser473), IRE-1α, MEKK3, iNOS, COX2, p-ERK1/2, p-JNK1/2, p-p38; the cell motility and focal adhesion-associated protein levels, such as Rho A, FAK, ROCK-1; the invasion-associated protein levels, such as TIMP1, uPA, MMP-2. MMP-9, MMP-13, MMP-1 and VEGF in U-2 OS cells. Confocal microscopy revealed that deguelin reduced NF-κB p65, Rho A and ROCK-1 protein levels in cytosol. MMP-7, MMP-9 and Rho A mRNA levels were suppressed by deguelin. These in vitro results provide evidence that deguelin may have potential as a novel anti-cancer agent for the treatment of osteosarcoma and provides the rationale for in vivo studies in animal models.

Ableson kinases negatively regulate invadopodia function and invasion in head and neck squamous cell carcinoma by inhibiting an HB-EGF autocrine loop

Head and neck squamous cell carcinoma (HNSCC) has a proclivity for locoregional invasion. HNSCC mediates invasion in part through invadopodia-based proteolysis of the extracellular matrix (ECM). Activation of Src, Erk1/2, Abl and Arg downstream of epidermal growth factor receptor (EGFR) modulates invadopodia activity through phosphorylation of the actin regulatory protein cortactin. In MDA-MB-231 breast cancer cells, Abl and Arg function downstream of Src to phosphorylate cortactin, promoting invadopodia ECM degradation activity and thus assigning a pro-invasive role for Ableson kinases. We report that Abl kinases have an opposite, negative regulatory role in HNSCC where they suppress invadopodia and tumor invasion. Impairment of Abl expression or Abl kinase activity with imatinib mesylate enhanced HNSCC matrix degradation and 3D collagen invasion, functions that were impaired in MDA-MB-231. HNSCC lines with elevated EGFR and Src activation did not contain increased Abl or Arg kinase activity, suggesting that Src could bypass Abl/Arg to phosphorylate cortactin and promote invadopodia ECM degradation. Src-transformed Abl(-/-)/Arg(-/-) fibroblasts produced ECM degrading invadopodia containing pY421 cortactin, indicating that Abl/Arg are dispensable for invadopodia function in this system. Imatinib-treated HNSCC cells had increased EGFR, Erk1/2 and Src activation, enhancing cortactin pY421 and pS405/418 required for invadopodia function. Imatinib stimulated shedding of the EGFR ligand heparin-binding EGF-like growth factor (HB-EGF) from HNSCC cells, where soluble HB-EGF enhanced invadopodia ECM degradation in HNSCC but not in MDA-MB-231. HNSCC cells treated with inhibitors of the EGFR-invadopodia pathway indicated that EGFR and Src are required for invadopodia function. Collectively, our results indicate that Abl kinases negatively regulate HNSCC invasive processes through suppression of an HB-EGF autocrine loop responsible for activating a EGFR-Src-cortactin cascade, in contrast to the invasion promoting functions of Abl kinases in breast and other cancer types. Our results provide mechanistic support for recent failed HNSCC clinical trials utilizing imatinib.

GnRH-(1-5) transactivates EGFR in Ishikawa human endometrial cells via an orphan G protein-coupled receptor

The decapeptide GnRH is known for its central role in the regulation of the hypothalamo-pituitary-gonadal axis. In addition, it is also known to have local effects within peripheral tissues. The zinc metalloendopeptidase, EC 3.4.24.15 (EP24.15), can cleave GnRH at the Tyr(5)-Gly(6) bond to form the pentapeptide, GnRH-(1-5). The central and peripheral effect of GnRH-(1-5) is different from its parent peptide, GnRH. In the current study, we examined the effect of GnRH-(1-5) on epidermal growth factor receptor (EGFR) phosphorylation and cellular migration. Using the Ishikawa cell line as a model of endometrial cancer, we demonstrate that GnRH-(1-5) stimulates epidermal growth factor release, increases the phosphorylation of EGFR (P < .05) at three tyrosine sites (992, 1045, 1068), and promotes cellular migration. In addition, we also demonstrate that these actions of GnRH-(1-5) are mediated by the orphan G protein-coupled receptor 101 (GPR101). Down-regulation of GPR101 expression blocked the GnRH-(1-5)-mediated release of epidermal growth factor and the subsequent phosphorylation of EGFR and cellular migration. These results suggest that GPR101 is a critical requirement for GnRH-(1-5) transactivation of EGFR in Ishikawa cells.

Antitumor effects of the novel quinazolinone MJ-33: inhibition of metastasis through the MAPK, AKT, NF-κB and AP-1 signaling pathways in DU145 human prostate cancer cells

Quinazolinone compounds have been shown to have antitumor activity in many human cancer cell lines. In the present study, we investigated the anti-metastatic activity of MJ-33 (2-(3-ethoxyphenyl)-6-pyrrolidinylquinazolinone), a novel quinazolinone derivate, and the signaling pathway of MJ-33 in human prostate cells. MJ-33 exhibited a growth inhibitory effect on DU145, LNCaP and PC-3 cells by MTT assay. DU145 cells showed greater sensitivity to the growth inhibition of MJ-33 than that of LNCaP and PC-3 cells. MJ-33 also had an inhibitory effect on the invasion, migration and adhesion of DU145 cells using Boyden chamber transwell assays, wound-healing and adhesion assay. In addition, MJ-33 inhibited cell metastasis through the reduction of matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9) and urokinase-type plasminogen activator (u-PA) enzyme activities and protein levels by gelatin zymography assay and western blot analysis, respectively. MJ-33 reduced the protein levels of p-JNK, p-p38, p-ERK, p-AKT and nuclear NF-κB (p65), c-fos and c-Jun protein levels by western blotting. Using electrophoretic mobility-shift assay (EMSA), we demonstrated that MJ-33 blocked the activation of transcription factor AP-1 (activator protein-1) and NF-κB, which led to the inhibition of MMP-2 and MMP-9 expression. Collectively, our data showed that MJ-33 decreased protein levels of MAPKs (mitogen-activated protein kinases), AKT, AP-1 and NF-κB, resulting in the inhibition of matrix metalloproteinases. Downregulation of MMP-2 and MMP-9 reduces the invasion, migration and adhesion activities of DU145 cells. MJ-33 may be a promising agent against prostate cancer metastasis.

Transducer of Cdc42-dependent actin assembly promotes epidermal growth factor-induced cell motility and invasiveness

Toca-1 (transducer of Cdc42-dependent actin assembly) interacts with the Cdc42·N-WASP and Abi1·Rac·WAVE F-actin branching pathways that function in lamellipodia formation and cell motility. However, the potential role of Toca-1 in these processes has not been reported. Here, we show that epidermal growth factor (EGF) induces Toca-1 localization to lamellipodia, where it co-localizes with F-actin and Arp2/3 complex in A431 epidermoid carcinoma cells. EGF also induces tyrosine phosphorylation of Toca-1 and interactions with N-WASP and Abi1. Stable knockdown of Toca-1 expression by RNA interference has no effect on cell growth, EGF receptor expression, or internalization. However, Toca-1 knockdown cells display defects in EGF-induced filopodia and lamellipodial protrusions compared with control cells. Further analyses reveal a role for Toca-1 in localization of Arp2/3 and Abi1 to lamellipodia. Toca-1 knockdown cells also display a significant defect in EGF-induced motility and invasiveness. Taken together, these results implicate Toca-1 in coordinating actin assembly within filopodia and lamellipodia to promote EGF-induced cell migration and invasion.

2-(3-Methoxyphenyl)-6, 7-methylenedioxoquinolin-4-one, a novel synthetic compound, inhibited migration and invasion in TSGH8301 human bladder cancer cells

Matrix metalloproteinases (MMPs) play an important role in the invasion, metastasis and angiogenesis of cancer cells. Many agents have been shown to inhibit the cancer cell migration and invasion by suppression of MMPs. 2-(3-Methoxyphenyl)-6,7-methylenedioxoquinolin-4-one (MMEQ) is a derivative compound synthesized from quinolin and the purpose of this study is to determine whether or not cell migration would be reduced in human bladder cancer TSGH8301 cells after MMEQ treatment. Wound healing assay and boyden chamber assay were used in cell migration and invasion determinations. Cell migration and invasion inhibited by MMEQ exerted an inhibitory effect on the sevenless homolog-1 (SOS-1), protein kinase c (PKC), extracellular signal-regulated kinase (ERK) and Rho A for causing the inhibitions of MMP-2 and -9, and then followed by the inhibitions of invasion and migration. MMEQ also affected FAK, PI3K or inhibited growth factor receptor-bound protein 2 (GRB2), nuclear factor kappaB (NF-κB), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) for cell proliferation inhibition. Therefore, MMEQ may serve as a drug in the prevention of tumor metastasis of bladder cancer in the future.

Benzyl isothiocyanate (BITC) inhibits migration and invasion of human colon cancer HT29 cells by inhibiting matrix metalloproteinase-2/-9 and urokinase plasminogen (uPA) through PKC and MAPK signaling pathway

Benzyl isothiocyanate (BITC), a component of dietary cruciferous vegetables, has antioxidant and anticancer properties. In this study, we show for the first time the antimetastatic effects of BITC in human colon cancer HT29 cells. BITC had an inhibitory effect on cell migration and invasion. Protein levels of matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9), and urokinase-plasminogen activator (u-PA) were reduced by BITC in a concentration-dependent manner. BITC also exerted an inhibitory effect on phosphorylation of c-Jun N-terminal kinase 1 and 2 (JNK1/2), extracellular signal-regulated kinases 1 and 2 (ERK1/2), phosphatidylinositol 3-kinase (PI3K) and protein kinase C (PKC) that are upstream of nuclear factor kappa B (NF-kappaB). BITC inhibited DNA binding activity of NF-kappaB. Moreover, BITC decreased the levels of c-Fos, c-Jun, Ras, FAK, PI3K and GRB2 in HT29 cells. Reductions in the enzyme activity, protein and mRNA (mRNA) levels of MMP-2 were observed in BITC-treated HT29 cells. BITC also inhibited mRNA levels of MMP-2, -7, and -9 in HT29 cells. Results from zymography showed that BITC treatment decreased MMP-2 expression in a concentration-dependent manner. BITC inhibited PKCdelta activity in HT29 cells. Furthermore, inhibitors specific for JNK (SP600125) reduced expression of MMP-2, MMP-9, and u-PA. These results demonstrated that BITC could alter HT29 cell metastasis by reduction of MMP-2, MMP-9, and u-PA expression through the suppression of a PKC, MAPK signaling pathway and inhibition of NF-kappaB levels. These findings suggest that BITC has potential as an antimetastatic agent.

Novel quinolone CHM-1 induces apoptosis and inhibits metastasis in a human osterogenic sarcoma cell line

Novel 2-phenyl-4-quinolone compounds have potent cytotoxic effects on different human cancer cell lines. In this study, we examined anticancer activity and mechanisms of 20-fluoro-6,7-methylenedioxy-2-phenyl-4-quinolone (CHM-1) in human osterogenic sarcoma U-2 OS cells. CHM-1-induced apoptosis was determined by flow cytometric analysis, DAPI staining, Comet assay, and caspase inhibitors. CHM-1-inhibited cell migration and invasion was assessed by a wound healing assay, gelatin zymography, and a Transwell assay. The mechanisms of CHM-1 effects on apoptosis and metastasis signaling pathways were studied using Western blotting and gene expression. CHM-1 induced G2/M arrest and apoptosis at an IC(50) (3 microM) in U-2 OS cells and caspase-3, -8, and -9 were activated. Caspase inhibitors increased cell viability after exposure to CHM-1. CHM-1-induced apoptosis was associated with enhanced ROS generation, DNA damage, decreased DeltaPsi(m) levels, and promotion of mitochondrial cytochrome c release. CHM-1 stimulated mRNA expression of caspase-3, -8, and -9, AIF, and Endo G. In addition, CHM-1 inhibited cell metastasis at a low concentration (<3 microM). CHM-1 inhibited the cell metastasis through the inhibition of MMP-2, -7, and -9. CHM-1 also decreased the levels of MAPK signaling pathways before leading to the inhibition of MMPs. In summary, CHM-1 is a potent inducer of apoptosis, which plays a role in the anticancer activity of CHM-1.

Involvement of matrix metalloproteinases on the inhibition of cells invasion and migration by emodin in human neuroblastoma SH-SY5Y cells

Emodin (1,3,8-trihydroxy-6-methylanthaquinone), an active component present in the root and rhizome of Rheum palmatum L. (Polygonaceae) has anti-bacterial, anti-tumor, diuretic and vasorelaxant effects. However, its mechanism of action on the cell migration and invasion of human neuroblastoma cancer SH-SY5Y cells is not fully understood. In this study, firstly, the effects of emodin on the percentage of viable cells were examined by using MTT assay and it was found that emodin induced dose-and time-dependent inhibition in human neuroblastoma SH-SY5Y cells. Second, the effects of emodin on the migration and invasion of SH-SY5Y cells were examined by using wound assay and matrigel counting and the results showed that emodin suppressed the migration and invasion of SH-SY5Y cells. Third, we examined the effect of emodin on the levels of associated proteins by using Western blotting and the results indicated that emodin inhibited the levels of GRB2, RhoA, HIF-1alpha, VEGF, FAK, iNOS, COX2, p-p38, p-c-jun, MMP2, MMP9 and MMP7 but promoted the levels of PKC, PI3K, MEKK3 and NF-kappaB p65 that led to the inhibition of migration and invasion of SH-SY5Y cells in vitro.

Benzyl isothiocyanate inhibits murine WEHI-3 leukemia cells in vitro and promotes phagocytosis in BALB/c mice in vivo

Many evidences have shown that dietary intake of cruciferous vegetables could protect against the risk of various types of malignancies. Benzyl isothiocyanate (BITC), one of the compounds from cruciferous vegetables, had shown induced cell cycle arrest and apoptosis in cancer cells. However, there is no available information to address that BITC affects murine leukemia cells in vitro and in vivo. Here, we investigated in vitro effects of BITC on murine leukemia WEHI-3 cells. BITC decreased the percentage of viable cells via G0/G1 arrest and apoptosis in WEHI-3 cells. BITC induced apoptosis through the dysfunction of mitochondria (decreased the levels of mitochondria membrane potential) and activation of caspase-3. Then we investigated in vivo effects of BITC on murine leukemia WEHI-3 cells and the results indicated that BITC decreased the weights of liver and spleen and it also decreased the percentage of CD11b and Mac-3 markers, indicating that the differentiation of the precursor of macrophage and B cells was inhibited. BITC promoted the activity of macrophage phagocytosis in cells which are isolated from PBMC and peritoneal (i.p.). Taken together, BITC can affect WEHI-3 cells in vitro and in vivo.

Rhein inhibits invasion and migration of human nasopharyngeal carcinoma cells in vitro by down-regulation of matrix metalloproteinases-9 and vascular endothelial growth factor

Progression of cancer invasion is believed to be dependent on the remodeling of extracellular matrix induced by tumor cells. Rhein has been shown to inhibit the growth and proliferation of human nasopharyngeal carcinoma (NPC) cells. However, the molecular mechanism underlying rhein-induced inhibition of cancer invasion has not been explored. Herein, we show that rhein could inhibit the invasion and migration of NPC cells in vitro. Rhein inhibits invasion by reducing the expression of matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF). Moreover, we demonstrate that the pathway involved in rhein-inhibited invasion is presumably through the growth factor receptor bound protein 2/son of sevenless-Ras-mitogen-activated protein kinase (GRB2/SOS-Ras-MAPK) pathway, as shown by an decrease in the expression levels of GRB2, SOS-1 and Ras as well as led to suppression of the phosphorylation of extracellular signal-regulated kinase (ERK) and p38 MAPK. Further study has shown that rhein also inhibited activation of transcription factor nuclear factor kappaB (NF-kappaB), which is known to implicate the regulation of MMP-9 and VEGF gene expression in cancer invasion. Our findings suggest that rhein inhibits the invasion of NPC cells may be mediated in part through the suppression of MMP-9 and VEGF expression via the modulation of NF-kappaB signaling pathway.

Effect of an LH-RH analogue on adhesion molecules in human prostate cancer cells

Background

The reduction in or the loss of the cell-cell adhesion often characterizes epithelial tumor initiation and progression. In the present study, we investigated the effects of the LH-RH analogue Leuprorelin acetate (LA), alone or associated with Dihydrotestosterone (DHT), on the expression of the adhesion proteins E-cadherin, α-, β- and γ-catenin in androgen-sensitive (LNCaP) and -insensitive (PC-3 and DU-145) prostate cancer cells.

Materials and Methods

Protein expression was evaluated by Western blotting on cells treated for 48 h with LA (10-11or 10-6M) and 10-9M DHT, alone or combined.

Results

In LNCaP cells, all the above mentioned molecules are expressed. PC-3 cells lack α-catenin, while DU-145 cells only express β- and γ-catenin. In both LNCaP and PC-3 cells two truncated forms (97 and 35 kDa) of E-cadherin are present other than the functional protein (120 kDa). In LNCaP cells, no significant changes in E-cadherin (120 and 97 kDa) level were produced by DHT, while the 35 kDa fragment was reduced by 34%. LA increased the full length E-cadherin (26–30%) as well as the two fragments (30–49%). The addition of DHT to LA significantly reduced the analogue-induced E-cadherin raising. In LNCaP cells β- and γ-catenin were up-regulated either by DHT (24% and 20%, respectively) or LA (up to 18% and up to 40%, respectively), while the expression of α-catenin was not modified. The combined DHT/LA treatment results in a less marked increase in β- and γ-catenin levels. In PC-3 cells no changes in adhesion molecule expression were produced by LA treatment, while in DU-145 cells the analogue determined an appreciable reduction in β- (20%) and γ-catenin (up to 35%) levels.

Conclusions

The up-regulation of E-cadherin, β- and γ-catenin in LNCaP cells by LA may be considered as another feature of the direct antitumor LH-RH analogue activity, as it may contribute to the maintenance/restoration of the normal architecture of prostate epithelium. The LA-induced modifications of catenins in DU-145 cells are worth some further investigations.

Molecular biology of gonadotropin-releasing hormone (GnRH)-I, GnRH-II, and their receptors in humans

In human beings, two forms of GnRH, termed GnRH-I and GnRH-II, encoded by separate genes have been identified. Although these hormones share comparable cDNA and genomic structures, their tissue distribution and regulation of gene expression are significantly dissimilar. The actions of GnRH are mediated by the GnRH receptor, which belongs to a member of the rhodopsin-like G protein-coupled receptor superfamily. However, to date, only one conventional GnRH receptor subtype (type I GnRH receptor) uniquely lacking a carboxyl-terminal tail has been found in the human body. Studies on the transcriptional regulation of the human GnRH receptor gene have indicated that tissue-specific gene expression is mediated by differential promoter usage in various cell types. Functionally, there is growing evidence showing that both GnRH-I and GnRH-II are potentially important autocrine and/or paracrine regulators in some extrapituitary compartments. Recent cloning of a second GnRH receptor subtype (type II GnRH receptor) in nonhuman primates revealed that it is structurally and functionally distinct from the mammalian type I receptor. However, the human type II receptor gene homolog carries a frameshift and a premature stop codon, suggesting that a full-length type II receptor does not exist in humans.

Molecular mechanism of epidermal growth factor receptor pathway mediated adhesion and invasion of Caco-2 cell line

AIM: To investigate the effect of epidermal growth factor receptor (EGFR) pathway on proliferation, adhesion and invasion of Caco-2 cell line and its molecular mechanism.

METHODS: Tetrazolium-based colorimetric assay was used to evaluate the effect of EGF, AG1478 or PD98059 on proliferation and growth of cultured human colon carcinoma Caco-2 cells. Matrigel experiment and cell adhesion assay were used to examine the invasiveness of Caco-2 cells. The transcription of MMP-2, MMP-9, TIMP-1 and TIMP-2 of Caco-2 cells was detected by reverse transcription polymerase chain reaction (RT-PCR). The expression of P-EGFR protein in Caco-2 cells was determined by Western-blot.

RESULTS: Exogenous EGF significantly enhanced the growth and proliferation of Caco-2 cells. The growth ratio was increased by 23.4% at 24 h (P<0.01). AG1478 (20 mmol/L, 48 h) and PD98059 (40 mmol/L, 72 h) inhibited the growth and proliferation of Caco-2 cells in a time-independent manner, and the growth rates were decreased by 45.7% and 54.6%, respectively (P<0.01). Matrigel experiment showed that EGF increased the adhesion (P<0.05) and invasion (P = 0.001) ability of Caco-2 cells in vitro at the concentration of 10 mg/L. AG1478 or PD98059 inhibited EGF-induced adhesion and invasion of Caco-2 cells (P<0.01) by blocking the activity of EGFR and ERK1/2. After treatment with EGF the protein of P-EGFR was increased, which was abolished by AG1478. RT-PCR assays revealed that exogenous EGF up-regulated mRNA levels of MMP-2 and MMP-9 and down-regulated mRNA levels of TIMP-1 and TIMP-2. Meanwhile AG1478 and PD98059 reversed the effect of EGF by decreasing the levels of MMP-2, MMP-9 mRNA and increasing the levels of TIMP-1 and TIMP-2 mRNA. The MMP-2 to TIMP-2 ratio and the MMP-9 to TIMP-1 ratio were decreased significantly by AG1478 or PD98059(P <0.001).

CONCLUSION: In human colon carcinoma, EGFR changes MMP-2, MMP-9, TIMP-1 and TIMP-2 transcription via MAPK signal pathway, which may contribute to the invasiveness and metastasis of Caco-2 cells.

Myricetin inhibits matrix metalloproteinase 2 protein expression and enzyme activity in colorectal carcinoma cells

Colorectal carcinoma is a leading cause of human mortality due to its high metastatic ability. Because the activation of matrix metalloproteinases (MMP) is a key factor in the metastatic process, agents with the ability to inhibit MMP activity have potential in the treatment of colorectal carcinoma. In the present study, among 36 flavonoids examined, myricetin was found to be the most potent inhibitor of MMP-2 enzyme activity in COLO 205 cells (IC50 = 7.82 μmol/L). Myricetin inhibition of MMP-2 enzyme activity was also found in the human colorectal carcinoma cell lines COLO 320HSR, COLO 320DM, HT 29, and COLO 205-X (IC50 = 11.18, 11.56, 13.25, and 23.51 μmol/L, respectively). In contrast, no inhibitory effect of MMP-2 protein expression or enzyme activity was observed in myricitrin (myricetin-3-rhamnoside)-treated cells. In 12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated COLO 205 cells, an increase in MMP-2 protein expression and enzyme activity, as well as of protein kinase C (PKC) α protein translocation, extracellular signal-regulated kinase (ERK) 1/2 protein phosphorylation, and c-Jun protein expression was observed. ERK inhibitor (PD98059) and PKC inhibitors (GF-109203X and H-7), but not p38 inhibitor (SB203580) or c-jun-NH2-kinase inhibitor (SP600125), significantly inhibited TPA-induced MMP-2 protein expression, with reduced ERK phosphorylation and c-Jun protein expression. Addition of myricetin but not myricitrin suppressed TPA-induced MMP-2 protein expression in COLO 205 cells by blocking the TPA-induced events, including translocation of PKCα from cytosol to membrane, phosphorylation of ERK1/2 protein, and induction of c-Jun protein expression. Addition of PD98059 or GF-109203X significantly enhanced the inhibitory effect of myricetin on MMP-2 enzyme activity induced by TPA. Furthermore, myricetin, but not myricitrin, suppressed TPA-induced invasion of COLO 205 cells in an in vitro invasion assay using Engelbreth-Holm-Swarm sarcoma tumor extract Matrigel–coated Transwells. Results of the present study indicate that myricetin significantly blocked both endogenous and TPA-induced MMP-2 enzyme activity by inhibiting its protein expression and enzyme activity. The blockade involved suppression of PKC translocation, ERK phosphorylation, and c-Jun protein expression.

Shikonin modulates cell proliferation by inhibiting epidermal growth factor receptor signaling in human epidermoid carcinoma cells

Shikonin isolated from the roots of the Chinese herb Lithospermum erythrorhizon has been associated with anti-inflammatory properties. We evaluated shikonin's chemotherapeutic potential and investigated its possible mechanism of action in a human cutaneous neoplasm in tissue culture. Shikonin preferentially inhibits the growth of human epidermoid carcinoma cells concentration- and time-dependently compared to SV-40 transfected keratinocytes, demonstrating its anti-proliferative effects against this cancer cell line. Additionally, shikonin decreased phosphorylated levels of EGFR, ERK1/2 and protein tyrosine kinases, while increasing phosphorylated JNK1/2 levels. Overall, shikonin treatment was associated with increased intracellular levels of phosphorylated apoptosis-related proteins, and decreased levels of proteins associated with proliferation in human epidermoid carcinoma cells.

The biology of gonadotropin hormone-releasing hormone: role in the control of tumor growth and progression in humans

It is now well known that different forms of GnRH coexist in the same vertebrate species. In humans, two forms of GnRH have been identified so far. The first form corresponds to the hypophysiotropic decapeptide, and is now called GnRH-I. The second form has been initially identified in the chicken brain, and it is referred to as GnRH-II. GnRH-I binds to and activates specific receptors, belonging to the 7 transmembrane (7TM) domain superfamily, present on pituitary gonadotropes. These receptors (type I GnRH receptors) are coupled to the Gq/11/PLC intracellular signalling pathway. A receptor specific for GnRH-II (type II GnRH receptor) has been identified in non-mammalian vertebrates as well as in primates, but not yet in humans. In the last 10-15 years experimental evidence has been accumulated indicating that GnRH-I is expressed, together with its receptors, in tumors of the reproductive tract (prostate, breast, ovary, and endometrium). In these hormone-related tumors, activation of type I GnRH receptors consistently decreases cell proliferation, mainly by interfering with the mitogenic activity of stimulatory growth factors (e.g., EGF, IGF). Recent data seem to suggest that GnRH-I might also reduce the migratory and invasive capacity of cancer cells, possibly by affecting the expression and/or activity of cell adhesion molecules and of enzymes involved in the remodelling of the extracellular matrix. These observations point to GnRH-I as an autocrine negative regulatory factor on tumor growth progression and metastatization. Extensive research has been performed to clarify the molecular mechanisms underlying the peculiar antitumor activity of GnRH-I. Type I GnRH receptors in hormone-related tumors correspond to those present at the pituitary level in terms of cDNA nucleotide sequence and protein molecular weight, but do not share the same pharmacological profile in terms of binding affinity for the different synthetic GnRH-I analogs. Moreover, the classical intracellular signalling pathway mediating the stimulatory activity of the decapeptide on gonadotropin synthesis and secretion is not involved in its inhibitory activity on hormone-related tumor growth. In these tumors, type I GnRH receptors are coupled to the Gi-cAMP, rather than the Gq/11-PLC, signal transduction pathway. Recently, we have reported that GnRH-I and type I GnRH receptors are expressed also in tumors not related to the reproductive system, such as melanoma. Also in melanoma cells, GnRH-I behaves as a negative regulator of tumor growth and progression. Interestingly, the biochemical and pharmacological profiles of type I GnRH receptors in melanoma seem to correspond to those of the receptors at pituitary level. The data so far reported on the expression and on the possible functions of GnRH-II in humans are still scanty. The decapeptide has been identified, together with a 'putative' type II GnRH receptor, both in the central nervous system and in peripheral structures, such as tissues of the reproductive tract (both normal and tumoral). The specific biological functions of GnRH-II in humans are presently under investigation.

3-OH flavone inhibition of epidermal growth factor-induced proliferaton through blocking prostaglandin E2 production

Epidermal growth factor (EGF) has been shown to induce proliferation in cells, however, the role of prostaglandin E(2) (PGE(2)) plays in EGF-induced proliferation in still unclear. EGF and PGE(2) showed proliferation responses in epidermoid carcinoma cell A431 by MTT and [(3)H] thymidine incorporation assay. Activation of the EGF receptor and extracellular signal-regulated protein kinases (ERK1/2), but not p38 and JNK, appeared 10 min after EGF treatment, whereas total amounts of ERK1/2, p38 and JNK remained unchanged in A431 cells, accompanied by induction of COX-2 and PGE(2) production. PD98059, a specific ERK1/2 inhibitor, inhibited EGF-induced proliferation with concomitant decreases in ERK1/2 phosphorylation and COX-2/PGE(2) induction. Non-steroid anti-inflammatory drugs (NSAIDs) such as aspirin and diclofenac, a COX activity inhibitor, inhibited EGF-induced proliferation by blocking PGE(2) production. The addition of PGE(2) reversed the inhibitory effects of PD98059, aspirin, and diclofenac on EGF-induced proliferation. This suggests that COX-2/PGE(2) activation involves in EGF-induced proliferation and locates at the downstream of ERK1/2 activation. Furthermore, the natural product, 3-OH flavone, showed the most-potent inhibitory activity on EGF-induced proliferation among 9 structurally-related compounds, and suppression of EGF receptor phosphorylation, ERK1/2 phosphorylation, and COX-2/PGE(2) production by 3-OH flavone was identified. PGE(2) addition attenuates the inhibitory activity of 3-OH flavone on EGF-induced proliferation by MTT assay and colony formation by soft agar assay. Additionally, 3-OH flavone also showed more-specific inhibition on EGF- than on fetal bovine serum (FBS)-induced proliferation in A431 cells. Results of our present study provide evidence to demonstrate that PGE(2) is an important downstream molecule in EGF-induced proliferation, and 3-OH flavone, which inhibits PGE(2) production by blocking MAPK cascade, might reserve potential for development as an anti-cancer drug.