Invasion and metastasis

G-quadruplex stabilizer Tetra-Pt(bpy) disrupts telomere maintenance and impairs FAK-mediated migration of telomerase-positive cells

G-quadruplex regulates a wide spectrum of biological processes, including telomere maintenance, DNA replication and transcription. The development of small molecules to selectively target G-quadruplex and their application remain hotspots in cancer therapy. Here, we explored the biological effect of G-quadruplexes stabilizer Tetra-Pt(bpy) in telomerase-positive cancer cells. Telomere maintenance was evaluated by telomerase repeat amplification protocol, chromosome orientation fluorescence in situ hybridization and telomere restriction fragment assays. We found that Tetra-Pt(bpy) accelerates telomere shortening through dual inhibition of telomerase activity and telomere sister chromatin exchanges mediated by telomeric G-quadruplexes. Consequently, Tetra-Pt(bpy)-treated cancer cells became enriched with extremely short telomeres and produced a strong telomeric DNA damage response following long-term treatment, leading to cell proliferation inhibition and senescence. Experimental evidence from RNA seq and cell migration-related assays showed that Tetra-Pt(bpy) decreased cell-matrix adhesion and inhibited the migration of non-senescent tumor cells. Mechanistically, Tetra-Pt(bpy) induced the formation of G-quadruplexes in focal adhesion kinase (FAK)-encoding gene PTK2, resulting in FAK transcription inhibition. Tetra-Pt(bpy) reduced xenograft tumor formation and inhibited tumor cell growth and migration in mice. This study further elucidates the function of G-quadruplexes in the human genome and reveals the potential of Tetra-Pt(bpy) as a novel chemotherapeutic agent for targeting telomerase-positive cancer cells.

C1632 suppresses the migration and proliferation of non-small-cell lung cancer cells involving LIN28 and FGFR1 pathway

Chemoresistance and migration represent major obstacles in the therapy of non‐small‐cell lung cancer (NSCLC), which accounts for approximately 85% of lung cancer patients in clinic. In the present study, we report that the compound C1632 is preferentially distributed in the lung after oral administration in vivo with high bioavailability and limited inhibitory effects on CYP450 isoenzymes. We found that C1632 could simultaneously inhibit the expression of LIN28 and block FGFR1 signalling transduction in NSCLC A549 and A549R cells, resulting in significant decreases in the phosphorylation of focal adhesion kinase and the expression of matrix metalloproteinase‐9. Consequently, C1632 effectively inhibited the migration and invasion of A549 and A549R cells. Meanwhile, C1632 significantly suppressed the cell viability and the colony formation of A549 and A549R cells by inhibiting DNA replication and inducing G0/G1 cell cycle arrest. Interestingly, compared with A549 cells, C1632 possesses the same or even better anti‐migration and anti‐proliferation effects on A549R cells, regardless of drug resistance. In addition, C1632 also displayed the capacity to inhibit the growth of A549R xenograft tumours in mice. Altogether, these findings reveal the potential of C1632 as a promising anti‐NSCLC agent, especially for chemotherapy‐resistant NSCLC treatment.

The different biological effects of TMPyP4 and cisplatin in the inflammatory microenvironment of osteosarcoma are attributed to G-quadruplex

OBJECTIVE

Osteosarcoma (OS) is characterized by high levels of the tumour-associated inflammatory microenvironment. Moreover, in approximately 60% of OS, telomere length is maintained by alternative lengthening of telomeres (ALT) pathway. Whether the ALT pathway can be exploited for OS therapeutic treatment and how the OS inflammatory microenvironment influences the anti-cancer drug effect remains unknown. Here, we examined the biological effects of TMPyP4 and cisplatin in the inflammatory microenvironment of OS cells.

MATERIALS AND METHODS

Immunofluorescence in situ hybridization (IF-FISH) and C-circle experiments were used to detect the G-quadruplex and ALT activity. The redox potential of single guanine, G-quadruplex and G-quadruplex/TMPyP4 was evaluated by the lowest unoccupied molecular orbital energy (LUMO), zeta potential and cyclic voltammetry. Cell viability, flow cytometry and apoptosis, Western blot, comet assay, adhesion, transwell and scratch experiments were performed to compare the anti-tumour proliferation and migration effects of TMPyP4 and cisplatin in the inflammatory microenvironment.

RESULTS

This study indicated that compared with cisplatin, TMPyP4 could induce the formation of human telomeres and FAK G-quadruplex in vitro and in vivo, and TMPyP4-treated OS cells showed fewer extrachromosomal C-circles and fewer ALT-associated promyelocytic leukaemia bodies. Consequently, the ALT activity and FAK-related cell migration were suppressed by TMPyP4. Mechanistically, the formation of G-quadruplex resulted in both lower redox potential than G within the genome and FAK transcription inhibition, and TMPyP4 could enhance this phenomenon, especially in the inflammatory microenvironment.

CONCLUSIONS

Our results reveal that TMPyP4 is more suitable for OS treatment than cisplatin.

Piperlongumine inhibits migration and proliferation of castration-resistant prostate cancer cells via triggering persistent DNA damage

BACKGROUND

Metastatic castration-resistant prostate cancer (CRPC) is the leading cause of death among men diagnosed with prostate cancer. Piperlongumine (PL) is a novel potential anticancer agent that has been demonstrated to exhibit anticancer efficacy against prostate cancer cells. However, the effects of PL on DNA damage and repair against CRPC have remained unclear. The aim of this study was to further explore the anticancer activity and mechanisms of action of PL against CRPC in terms of DNA damage and repair processes.

METHODS

The effect of PL on CRPC was evaluated by MTT assay, long-term cell proliferation, reactive oxygen species assay, western blot assay, flow cytometry assay (annexin V/PI staining), β-gal staining assay and DAPI staining assay. The capacity of PL to inhibit the invasion and migration of CRPC cells was assessed by scratch-wound assay, cell adhesion assay, transwell assay and immunofluorescence (IF) assay. The effect of PL on DNA damage and repair was determined via IF assay and comet assay.

RESULTS

The results showed that PL exhibited stronger anticancer activity against CRPC compared to that of taxol, cisplatin (DDP), doxorubicin (Dox), or 5-Fluorouracil (5-FU), with fewer side effects in normal cells. Importantly, PL treatment significantly decreased cell adhesion to the extracellular matrix and inhibited the migration of CRPC cells through affecting the expression and distribution of focal adhesion kinase (FAK), leading to concentration-dependent inhibition of CRPC cell proliferation and concomitantly increased cell death. Moreover, PL treatment triggered persistent DNA damage and provoked strong DNA damage responses in CRPC cells.

CONCLUSION

Collectively, our findings demonstrate that PL potently inhibited proliferation, migration, and invasion of CRPC cells and that these potent anticancer effects were potentially achieved via triggering persistent DNA damage in CRPC cells.

Effects of Benzoapyrene on migration and invasion of lung cancer cells functioning by TNF-α

In this study, we attempted to find out the underlying mechanism of Benzoapyrene and metastasis of lung cancer cells. We also did experiments to testify the connection between BaP and its potential target, TNF-α. Cell median lethal dose (IC₅₀ ) of both cells was measured by crystal violet method. Quantitative real-time reverse transcription PCR (qRT-PCR) and Western blot were employed to detect the expression of TNF-α. Wound healing assay and transwell assay were utilized to testify the impacts of BaP and TNF-α on the metastasis of lung cancer cells. Cell death rate was elevated with the increase of BaP concentration. BaP increased the number of metastatic cells of lung cancer. The expressions of TNF-α pathway-associated protein (TNF-α, NF-kB [P65], Caspase3, and Caspase8) were enhanced by overexpressed BaP. TNF-α shRNA suppressed the positive effects of BaP on migration and invasion of lung cancer cells. Our study validated the positive effects of BaP on the metastasis of lung cancer cells. We also revealed the instrumental role of TNF-α in helping the development of lung cancer cells induced by BaP.

Expression of Matrix Metalloproteinases and Tissue Inhibitor of Metalloproteinases in Laryngeal and Pharyngeal Squamous Cell Carcinoma: A Quantitative Analysis

Squamous cell carcinomas of the head and neck are known for their aggressive growth and propensity to metastasize. Invasion is facilitated by matrix metalloproteineases (MMPs). Tissue inhibitors of MMPs (TIMPs) negatively regulate MMP activity. MMP and TIMP expression in head and neck squamous cell carcinomas was determined by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). qRT-PCR allows measurement of several mRNAs from as little as 4 μg of total cellular RNA. We measured MMP-1, MMP-2, MMP-9, and TIMP-1 expression in 8 specimens of primary tumors and adjacent normal tissue. MMP-1 was overexpressed in 6 of 8 tumors, and MMP-9 was over-expressed in 4 of 7 tumors. MMP-2 was expressed in 3 of 8 tumors and 3 of 8 normal samples. TIMP-1 was expressed in all specimens. This work demonstrates that qRT-PCR can be used to examine expression of specific mRNAs in clinical specimens. Therefore this method provides another tool for the molecular analysis of tumors.

TMPyP4 promotes cancer cell migration at low doses, but induces cell death at high doses

TMPyP4 is widely considered as a potential photosensitizer in photodynamic therapy and a G-quadruplex stabilizer for telomerase-based cancer therapeutics. However, its biological effects including a possible adverse-effect are poorly understood. In this study, whole genome RNA-seq analysis was used to explore the alteration in gene expression induced by TMPyP4. Unexpectedly, we find that 27.67% of changed genes were functionally related to cell adhesion. Experimental evidences from cell adhesion assay, scratch-wound and transwell assay indicate that TMPyP4 at conventional doses (≤0.5 μM) increases cell-matrix adhesion and promotes the migration of tumor cells. In contrast, a high dose of TMPyP4 (≥2 μM) inhibits cell proliferation and induces cell death. The unintended “side-effect” of TMPyP4 on promoting cell migration suggests that a relative high dose of TMPyP4 is preferred for therapeutic purpose. These findings contribute to better understanding of biological effects induced by TMPyP4 and provide a new insight into the complexity and implication for TMPyP4 based cancer therapy.

Recombinant Erdr1 suppresses the migration and invasion ability of human gastric cancer cells, SNU-216, through the JNK pathway

Erythroid differentiation regulator 1 (Erdr1) suppressed cell motility in vitro and has anti-metastatic effect in vivo on melanoma. The current study investigated the effect of recombinant Erdr1 on the migration and invasion ability of SNU-216 cell, a gastric cancer cell line. The expression of Erdr1 is inversely correlated with IL-18 expression, which has a pro-cancer effect in gastric cancer. Treatment with rErdr1 markedly suppressed the ability of SNU-216 cells to migrate and invade, indicating that recombinant Erdr1 inhibited the motility of gastric cancer cells. E-cadherin expression levels were measured to determine the factor involved in the rErdr1-suppressed motility. E-cadherin is a representative of the cadherin family, known as cell motility enhancement adhesion molecule. Our results revealed that E-cadherin levels were increased by rErdr1 treatment, suggesting the involvement of E-cadherin in rErdr1-reduced cell migration. The cells were treated with specific MAPK inhibitors such as SP600125, SB203580 or PD98059 to identify the signaling mechanism involved with rErdr1 suppressed cell migration. The results indicated that the rErdr1 inhibited migration was primarily reversed by SP600125, a JNK inhibitor. In addition, the level of JNK phosphorylation was markedly increased by recombinant Erdr1. Taken together, these findings suggest that rErdr1 suppressed the ability of gastric cancer cells to metastasis by up regulating E-cadherin through a JNK pathway activation. Furthermore, it can be suggested that the inhibitory effect of recombinant Erdr1 on SNU-216 cell's metastatic potential was through cell motility suppression.

TGF-β1 modulates the homeostasis between MMPs and MMP inhibitors through p38 MAPK and ERK1/2 in highly invasive breast cancer cells

Background

Metastasis is the main factor responsible for death in breast cancer patients. Matrix metalloproteinases (MMPs) and their inhibitors, known as tissue inhibitors of MMPs (TIMPs), and the membrane-associated MMP inhibitor (RECK), are essential for the metastatic process. We have previously shown a positive correlation between MMPs and their inhibitors expression during breast cancer progression; however, the molecular mechanisms underlying this coordinate regulation remain unknown. In this report, we investigated whether TGF-β1 could be a common regulator for MMPs, TIMPs and RECK in human breast cancer cell models.

Methods

The mRNA expression levels of TGF-β isoforms and their receptors were analyzed by qRT-PCR in a panel of five human breast cancer cell lines displaying different degrees of invasiveness and metastatic potential. The highly invasive MDA-MB-231 cell line was treated with different concentrations of recombinant TGF-β1 and also with pharmacological inhibitors of p38 MAPK and ERK1/2. The migratory and invasive potential of these treated cells were examined in vitro by transwell assays.

Results

In general, TGF-β2, TβRI and TβRII are over-expressed in more aggressive cells, except for TβRI, which was also highly expressed in ZR-75-1 cells. In addition, TGF-β1-treated MDA-MB-231 cells presented significantly increased mRNA expression of MMP-2, MMP-9, MMP-14, TIMP-2 and RECK. TGF-β1 also increased TIMP-2, MMP-2 and MMP-9 protein levels but downregulated RECK expression. Furthermore, we analyzed the involvement of p38 MAPK and ERK1/2, representing two well established Smad-independent pathways, in the proposed mechanism. Inhibition of p38MAPK blocked TGF-β1-increased mRNA expression of all MMPs and MMP inhibitors analyzed, and prevented TGF-β1 upregulation of TIMP-2 and MMP-2 proteins. Moreover, ERK1/2 inhibition increased RECK and prevented the TGF-β1 induction of pro-MMP-9 and TIMP-2 proteins. TGF-β1-enhanced migration and invasion capacities were blocked by p38MAPK, ERK1/2 and MMP inhibitors.

Conclusion

Altogether, our results support that TGF-β1 modulates the mRNA and protein levels of MMPs (MMP-2 and MMP-9) as much as their inhibitors (TIMP-2 and RECK). Therefore, this cytokine plays a crucial role in breast cancer progression by modulating key elements of ECM homeostasis control. Thus, although the complexity of this signaling network, TGF-β1 still remains a promising target for breast cancer treatment.

Effects of RNAi-mediated matrix metalloproteinase-2 gene silencing on the invasiveness and adhesion of esophageal carcinoma cells, KYSE150

BACKGROUND

Esophageal carcinoma is one of the main malignancies in China. Previous studies indicated that matrix metalloproteinases (MMPs) play important roles in the process of tumor invasion and metastasis in several types of solid tumors. Among all of the MMPs, MMP-2 is one of the MMPs closely associated with tumor invasion. In this study, we suppressed MMP-2 expression with RNA interference and then observed inhibitory effects on the invasion and migration of the esophageal carcinoma cell line KYSE150.

METHODS

Three target sequences were selected and siRNA against MMP-2 mRNA were synthesized. After being transfected by the transfection complexes, the MMP-2 expression of KYSE150 cells, which overexpresses MMP-2, were examined by Western blot analysis and real-time polymerase chain reaction (PCR). Cell migration and invasion were measured with migration assay and Boyden chamber assays, respectively.

RESULTS

RNAi against MMP-2 successfully inhibited the mRNA and protein expression of MMP-2 in the esophageal carcinoma cell line KYSE150. MMP-2 knockdown inhibited the invasion and migration of esophageal carcinoma cell line KYSE150.

CONCLUSIONS

These findings suggested that the RNAi approach towards MMP-2 may be a potentially effective therapeutic method for the treatment of esophageal carcinoma.

Metastasis suppressor genes at the interface between the environment and tumor cell growth

The molecular mechanisms and genetic programs required for cancer metastasis are sometimes overlapping, but components are clearly distinct from those promoting growth of a primary tumor. Every sequential, rate-limiting step in the sequence of events leading to metastasis requires coordinated expression of multiple genes, necessary signaling events, and favorable environmental conditions or the ability to escape negative selection pressures. Metastasis suppressors are molecules that inhibit the process of metastasis without preventing growth of the primary tumor. The cellular processes regulated by metastasis suppressors are diverse and function at every step in the metastatic cascade. As we gain knowledge into the molecular mechanisms of metastasis suppressors and cofactors with which they interact, we learn more about the process, including appreciation that some are potential targets for therapy of metastasis, the most lethal aspect of cancer. Until now, metastasis suppressors have been described largely by their function. With greater appreciation of their biochemical mechanisms of action, the importance of context is increasingly recognized especially since tumor cells exist in myriad microenvironments. In this chapter, we assemble the evidence that selected molecules are indeed suppressors of metastasis, collate the data defining the biochemical mechanisms of action, and glean insights regarding how metastasis suppressors regulate tumor cell communication to-from microenvironments.

Significance of manipulating tumour hypoxia and radiation dose rate in terms of local tumour response and lung metastatic potential, referring to the response of quiescent cell populations

The purpose of this study was to evaluate the influence of manipulating intratumour oxygenation status and radiation dose rate on local tumour response and lung metastases following radiotherapy, referring to the response of quiescent cell populations within irradiated tumours. B16-BL6 melanoma tumour-bearing C57BL/6 mice were continuously given 5-bromo-2'-deoxyuridine (BrdU) to label all proliferating (P) cells. They received gamma-ray irradiation at high dose rate (HDR) or reduced dose rate (RDR) following treatment with the acute hypoxia-releasing agent nicotinamide or local hyperthermia at mild temperatures (MTH). Immediately after the irradiation, cells from some tumours were isolated and incubated with a cytokinesis blocker. The responses of the quiescent (Q) and total (proliferating + Q) cell populations were assessed based on the frequency of micronuclei using immunofluorescence staining for BrdU. In other tumour-bearing mice, 17 days after irradiation, macroscopic lung metastases were enumerated. Following HDR irradiation, nicotinamide and MTH enhanced the sensitivity of the total and Q-cell populations, respectively. The decrease in sensitivity at RDR irradiation compared with HDR irradiation was slightly inhibited by MTH, especially in Q cells. Without gamma-ray irradiation, nicotinamide treatment tended to reduce the number of lung metastases. With gamma-rays, in combination with nicotinamide or MTH, especially the former, HDR irradiation decreased the number of metastases more remarkably than RDR irradiation. Manipulating both tumour hypoxia and irradiation dose rate have the potential to influence lung metastasis. The combination with the acute hypoxia-releasing agent nicotinamide may be more promising in HDR than RDR irradiation in terms of reducing the number of lung metastases.

A self-propagating matrix metalloprotease-9 (MMP-9) dependent cycle of chronic neutrophilic inflammation

Background

Chronic neutrophilic inflammation is a poorly understood feature in a variety of diseases with notable worldwide morbidity and mortality. We have recently characterized N-acetyl Pro-Gly-Pro (Ac-PGP) as an important neutrophil (PMN) chemoattractant in chronic inflammation generated from the breakdown of collagen by the actions of MMP-9. MMP-9 is present in the granules of PMNs and is differentially released during inflammation but whether Ac-PGP contributes to this ongoing proteolytic activity in chronic neutrophilic inflammation is currently unknown.

Methodology/Principal Findings

Utilizing isolated primary blood PMNs from human donors, we found that Ac-PGP induces significant release of MMP-9 and concurrently activates the ERK1/2 MAPK pathway. This MMP-9 release is attenuated by an inhibitor of ERK1/2 MAPK and upstream blockade of CXCR1 and CXCR2 receptors with repertaxin leads to decreased MMP-9 release and ERK 1/2 MAPK activation. Supernatants obtained from PMNs stimulated by Ac-PGP generate more Ac-PGP when incubated with intact collagen ex vivo; this effect is inhibited by an ERK1/2 pathway inhibitor. Finally, clinical samples from individuals with CF demonstrate a notable correlation between Ac-PGP (as measured by liquid chromatography-tandem mass spectrometry) and MMP-9 levels even when accounting for total PMN burden.

Conclusions/Significance

These data indicate that ECM-derived Ac-PGP could result in a feed-forward cycle by releasing MMP-9 from activated PMNs through the ligation of CXCR1 and CXCR2 and subsequent activation of the ERK1/2 MAPK, highlighting for the first time a matrix-derived chemokine (matrikine) augmenting its generation through a discrete receptor/intracellular signaling pathway. These findings have notable implications to the development unrelenting chronic PMN inflammation in human disease.

Soluble L1CAM promotes breast cancer cell adhesion and migration in vitro, but not invasion

Background

Neural recognition molecule L1CAM, which is a key protein involved in early nervous system development, is known to be abnormally expressed and shed in several types of cancers where it participates in metastasis and progression. The distinction of L1CAM presence in cancerous vs. normal tissues has suggested it to be a new target for cancer treatment. Our current study focused on the potential role of soluble L1CAM in breast cancer cell adhesion to extracellular matrix proteins, migration, and invasion.

Results

We found L1 expression levels were correlated with breast cancer stage of progression in established data sets of clinical samples, and also were high in more metastatic breast cancer cell lines MDA-MB-231 and MDA-MB-435, but low in less migratory MDA-MB-468 cells. Proteolysis of L1 into its soluble form (sL1) was detected in cell culture medium from all three above cell lines, and can be induced by PMA activation. Over-expression of the L1 ectodomain in MDA-MB-468 cells by using a lentiviral vector greatly increased the amount of sL1 released by those cells. Concomitantly, cell adhesion to extracellular matrix and cell transmigration ability were significantly promoted, while cell invasion ability through Matrigel™ remained unaffected. On the other hand, attenuating L1 expression in MDA-MB-231 cells by using a shRNA lentiviral vector resulted in reduced cell-matrix adhesion and transmigration. Similar effects were also shown by monoclonal antibody blocking of the L1 extracellular region. Moreover, sL1 in conditioned cell culture medium induced a directional migration of MDA-MB-468 cells, which could be neutralized by antibody treatment.

Conclusions

Our data provides new evidence for the function of L1CAM and its soluble form in promoting cancer cell adhesion to ECM and cell migration. Thus, L1CAM is validated further to be a potential early diagnostic marker in breast cancer progression and a target for breast cancer therapy.

Abnormal expression of early growth response 1 in gastric cancer: association with tumor invasion, metastasis and heparanase transcription

Given that previous studies indicated that early growth response 1 (EGR1) exerts pro-tumorigenic effects through regulating heparanase (HPA) transcription, it was hypothesized that EGR1 may correlate with the progression of gastric cancer. One hundred and fifteen patients with gastric cancer were evaluated for the protein and transcript expression of EGR1 and HPA on immunohistochemistry and real-time quantitative polymerase chain reaction (PCR). In normal gastric mucosa, EGR1 protein expression was absent or weak, whereas gastric cancer was positive for EGR1. Seventy gastric cancer patients (60.9%) were positive for cytoplasmic EGR1 expression, and 26 (22.6%) had nuclear expression of EGR1. In the gastric cancer examined, the transcripts of EGR1 were enhanced compared to that of normal gastric mucosa, and positively correlated with EGR1 protein expression. The cytoplasmic or nuclear expression of EGR1 and its transcripts in gastric cancer was positively correlated with tumor infiltration (P < 0.05), lymph node and distant metastasis (P < 0.05), tumor node metastasis (TNM) stages (P < 0.05), but not with age, gender, tumor location and size, histological types or differentiation. Moreover, the protein and transcript expression of EGR1 was correlated with that of HPA in gastric cancer. These results indicate that aberrant expression of EGR1 in gastric cancer is associated with tumor invasion and metastasis, and HPA transcription.

Knockdown of Li-cadherin increases metastatic behaviors of LoVo cells

PURPOSE

The aim of this study was to investigate the role of Li-cadherin in invasion and metastasis in LoVo cells.

METHODS

We applied RNA interference mediated downregulation of Li-cadherin expression in LoVo cells. Li-cadherin expression in LoVo cells was examined by semiquantitative polymerase chain reaction, immunofluorescence, western blot, and immunoprecipitation, respectively. Effect of suppression of Li-cadherin expression on cell migration, invasion, and adhesion was detected by wound healing assay, migration assay, invasion assay, and adhesion assay. Expression and activity of MMP-2 and MMP-9 were analyzed by gelatin zymography.

RESULTS

Cell migration, invasion, and adhesion were increased concomitantly with the reduction in Li-cadherin protein expression. Furthermore, downregulation of Li-cadherin expression induced secretion of proMMP-9, active MMP-9 and active MMP-2.

CONCLUSIONS

This study suggests that silencing Li-cadherin has positive actions in the processes of LoVo cells invasion and metastasis, and the interactions among MMP-2, MMP-9, and Li-cadherin participate in the multiple steps of invasion and metastasis in LoVo colorectal cancer cells.

Small RNA interference-mediated gene silencing of heparanase abolishes the invasion, metastasis and angiogenesis of gastric cancer cells

Background

Heparanase facilitates the invasion and metastasis of cancer cells, and is over-expressed in many kinds of malignancies. Our studies indicated that heparanase was frequently expressed in advanced gastric cancers. The aim of this study is to determine whether silencing of heparanase expression can abolish the malignant characteristics of gastric cancer cells.

Methods

Three heparanase-specific small interfering RNA (siRNAs) were designed, synthesized, and transfected into cultured gastric cancer cell line SGC-7901. Heparanase expression was measured by RT-PCR, real-time quantitative PCR and Western blot. Cell proliferation was detected by MTT colorimetry and colony formation assay. The in vitro invasion and metastasis of cancer cells were measured by cell adhesion assay, scratch assay and matrigel invasion assay. The angiogenesis capabilities of cancer cells were measured by tube formation of endothelial cells.

Results

Transfection of siRNA against 1496-1514 bp of encoding regions resulted in reduced expression of heparanase, which started at 24 hrs and lasted for 120 hrs post-transfection. The siRNA-mediated silencing of heparanase suppressed the cellular proliferation of SGC-7901 cells. In addition, the in vitro invasion and metastasis of cancer cells were attenuated after knock-down of heparanase. Moreover, transfection of heparanase-specific siRNA attenuated the in vitro angiogenesis of cancer cells in a dose-dependent manner.

Conclusions

These results demonstrated that gene silencing of heparanase can efficiently abolish the proliferation, invasion, metastasis and angiogenesis of human gastric cancer cells in vitro, suggesting that heparanase-specific siRNA is of potential values as a novel therapeutic agent for human gastric cancer.

Stable knockdown of heparanase expression in gastric cancer cells in vitro

AIM: To develop short hairpin RNA (shRNA) against heparanase, and to determine its effects on heparanase expression and the malignant characteristics of gastric cancer cells.

METHODS: Heparanase-specific shRNA was constructed and transferred into cultured the gastric cancer cell line SGC-7901. Stable subclonal cells were screened by G418 selection. Heparanase expression was measured by reverse transcriptase-polymerase chain reaction (RT-PCR), real-time quantitative PCR and Western blotting. Cell proliferation was detected by 2-(4,5-dimethyltriazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetry and colony formation assay. The in vitro invasiveness and metastasis of cancer cells were measured by cell adhesion assay, wound healing assay and matrigel invasion assay. The angiogenesis capabilities of cancer cells were measured by tube formation of endothelial cells.

RESULTS: Stable transfection of heparanase-specific shRNA, but not of scrambled shRNA and mock vector, resulted in reduced mRNA and protein levels of heparanase. The shRNA-mediated knockdown of heparanase did not affect the cellular proliferation of SGC-7901 cells. However, the in vitro invasiveness and metastasis of cancer cells were decreased after knockdown of heparanase. Moreover, transfection of heparanase-specific shRNA decreased the in vitro angiogenesis capabilities of SGC-7901 cells.

CONCLUSION: Stable knockdown of heparanase can efficiently decrease the invasiveness, metastasis and angiogenesis of human gastric cancer cells. In contrast, stable knockdown of heparanase does not affect the cell proliferation.

The role of the exocyst in matrix metalloproteinase secretion and actin dynamics during tumor cell invadopodia formation

Invadopodia are actin-rich membrane protrusions formed by tumor cells that degrade the extracellular matrix for invasion. Invadopodia formation involves membrane protrusions driven by Arp2/3-mediated actin polymerization and secretion of matrix metalloproteinases (MMPs) at the focal degrading sites. The exocyst mediates the tethering of post-Golgi secretory vesicles at the plasma membrane for exocytosis and has recently been implicated in regulating actin dynamics during cell migration. Here, we report that the exocyst plays a pivotal role in invadopodial activity. With RNAi knockdown of the exocyst component Exo70 or Sec8, MDA-MB-231 cells expressing constitutively active c-Src failed to form invadopodia. On the other hand, overexpression of Exo70 promoted invadopodia formation. Disrupting the exocyst function by siEXO70 or siSEC8 treatment or by expression of a dominant negative fragment of Exo70 inhibited the secretion of MMPs. We have also found that the exocyst interacts with the Arp2/3 complex in cells with high invasion potential; blocking the exocyst-Arp2/3 interaction inhibited Arp2/3-mediated actin polymerization and invadopodia formation. Together, our results suggest that the exocyst plays important roles in cell invasion by mediating the secretion of MMPs at focal degrading sites and regulating Arp2/3-mediated actin dynamics.

The functional interplay between EGFR overexpression, hTERT activation, and p53 mutation in esophageal epithelial cells with activation of stromal fibroblasts induces tumor development, invasion, and differentiation

Esophageal cancer is a prototypic squamous cell cancer that carries a poor prognosis, primarily due to presentation at advanced stages. We used human esophageal epithelial cells as a platform to recapitulate esophageal squamous cell cancer, thereby providing insights into the molecular pathogenesis of squamous cell cancers in general. This was achieved through the retroviral-mediated transduction into normal, primary human esophageal epithelial cells of epidermal growth factor receptor (EGFR), the catalytic subunit of human telomerase (hTERT), and p53(R175H), genes that are frequently altered in human esophageal squamous cell cancer. These cells demonstrated increased migration and invasion when compared with control cells. When these genetically altered cells were placed within the in vivo-like context of an organotypic three-dimensional (3D) culture system, the cells formed a high-grade dysplastic epithelium with malignant cells invading into the stromal extracellular matrix (ECM). The invasive phenotype was in part modulated by the activation of matrix metalloproteinase-9 (MMP-9). Using pharmacological and genetic approaches to decrease MMP-9, invasion into the underlying ECM could be suppressed partially. In addition, tumor differentiation was influenced by the type of fibroblasts within the stromal ECM. To that end, fetal esophageal fibroblasts fostered a microenvironment conducive to poorly differentiated invading tumor cells, whereas fetal skin fibroblasts supported a well-differentiated tumor as illustrated by keratin "pearl" formation, a hallmark feature of well-differentiated squamous cell cancers. When inducible AKT was introduced into fetal skin esophageal fibroblasts, a more invasive, less-differentiated esophageal cancer phenotype was achieved. Invasion into the stromal ECM was attenuated by genetic knockdown of AKT1 as well as AKT2. Taken together, alterations in key oncogenes and tumor suppressor genes in esophageal epithelial cells, the composition and activation of fibroblasts, and the components of the ECM conspire to regulate the physical and biological properties of the stroma.

PRL-3 siRNA inhibits the metastasis of B16-BL6 mouse melanoma cells in vitro and in vivo

Phosphatase of regenerating liver-3 (PRL-3) has been proposed to promote the invasion of tumor cells to metastasis sites. However, the effect of PRL-3 on spontaneous metastasis has not been clearly demonstrated, and whether PRL-3 could become a new therapeutic target in malignant tumor is still unknown. In this study, we used PRL-3 siRNA as a molecular medicine to specifically reduce the expression of PRL-3 in B16-BL6 cells, a highly metastatic melanoma cell line. In vitro, PRL-3 siRNA significantly inhibited cell adhesion and migration, but had no effect on cell proliferation. In the spontaneous metastatic tumor model in vivo, PRL-3 siRNA treatment remarkably inhibited the proliferation of primary tumor, prevented tumor cells from invading the draining lymph nodes, and prolonged the life span of mice. Therefore, our results indicate that PRL-3 plays a critical role in promoting the whole process of spontaneous metastasis and tumor growth initiation, and that inhibiting PRL-3 will improve malignant tumor therapy.

Adenoviral transduction of MRP-1/CD9 and KAI1/CD82 inhibits lymph node metastasis in orthotopic lung cancer model

Conventional therapies still remain less effective for metastasis of lung cancer, thus leading to a poor prognosis for this disorder. Although the processes involved in metastasis have not yet been clearly elucidated, our previous studies have shown that higher expression levels of MRP-1/CD9 and KAI1/CD82 in cancer cells are significantly correlated with less metastatic potency. To determine whether the gene transfer of these tetraspanins into lung tumor cells may be a useful strategy to regulate metastasis, we adopted an orthotopic lung cancer model produced by the intrapulmonary implantation of Lewis lung carcinoma (LLC) cells and evaluated the metastatic growth in the mediastinal lymph nodes using two different methods of gene delivery as follows: (a) the implantation of LLC cells preinfected with adenovirus encoding either MRP-1/CD9 cDNA, KAI1/CD82 cDNA, or LacZ gene into the mouse lung and (b) the intratracheal administration of these adenoviruses into the mice orthotopically preimplanted with LLC cells. In both cases, we found that the delivery of either MRP-1/CD9 or KAI1/CD82 cDNA dramatically reduced the metastases to the mediastinal lymph nodes in comparison with those of LacZ gene delivery, without affecting the primary tumor growth at the implanted site. These results reemphasize the important role of MRP-1/CD9 and KAI1/CD82 in the suppression of the metastatic process and also show the feasibility of gene therapy when using these tetraspanins for lung cancer to prevent metastasis to the regional lymph nodes. This strategy may therefore be clinically applicable as a prophylactic treatment to suppress the occurrence of lymph node metastasis.

Interleukin-1β induces MMP-9 expression via p42/p44 MAPK, p38 MAPK, JNK, and nuclear factor-κB signaling pathways in human tracheal smooth muscle cells

Matrix metalloproteinases (MMPs) are responsible for degradation of extracellular matrix and play important roles in cell migration, proliferation, and tissue remodeling related to airway inflammation. Interleukin-1beta (IL-1beta) has been shown to induce MMP-9 production in many cell types and contribute to airway inflammatory responses. However, the mechanisms underlying MMP-9 expression induced by IL-1beta in human tracheal smooth muscle cells (HTSMCs) remain unclear. Here, we investigated the roles of p42/p44 MAPK, p38 MAPK, JNK, and NF-kappaB pathways for IL-1beta-induced MMP-9 production in HTSMCs. IL-1beta induced production of MMP-9 protein and mRNA in a time- and concentration-dependent manner determined by zymographic, Western blotting, and RT-PCR analyses, which was attenuated by inhibitors of MEK1/2 (U0126), p38 MAPK (SB202190), JNK (SP600125), and NF-kappaB (helenalin), and transfection with dominant negative mutants of MEK1/2, p38 and JNK, respectively. IL-1beta-stimulated phosphorylation of p42/p44 MAPK, p38 MAPK, and JNK was attenuated by pretreatment with U0126, SB202190, SP600125, or transfection with these dominant negative mutants of MEK, ERK, p38 and JNK, respectively. Furthermore, IL-1beta-stimulated translocation of NF-kappaB into the nucleus and degradation of IkappaB-alpha was blocked by helenalin. Finally, the reporter gene assay revealed that MAPKs and NF-kappaB are required for IL-1beta-induced MMP-9 luciferase activity in HTSMCs. MMP-9 promoter activity was enhanced by IL-1beta in HTSMCs transfected with MMP-9-Luc, which was inhibited by helenalin, U0126, SB202190, and SP600125. Taken together, the transcription factor NF-kappaB, p42/p44 MAPK, p38 MAPK, and JNK that are involved in MMP-9 expression in HTSMCs exposed to IL-1beta have now been identified.

Phosphatase of regenerating liver-3 promotes motility and metastasis of mouse melanoma cells

Recent reports suggested that phosphatase of regenerating liver (PRL)-3 might be involved in colorectal carcinoma metastasis with an unknown mechanism. Here we demonstrated that PRL-3 expression was up-regulated in human liver carcinoma compared with normal liver. PRL-3 was also highly expressed in metastatic melanoma B16-BL6 cells but not in its lowly metastatic parental cell line, B16 cells. B16 cells transfected with PRL-3 cDNA displayed morphological transformation from epithelial-like shape to fibroblast-like shape. PRL-3-overexpressed cells showed much higher migratory ability, which could be reversed by specific anti-sense oligodeoxynucleotide and the phosphatase inhibitors sodium orthovanadate or potassium bisperoxo oxovanadate V. Meanwhile, the expression of the catalytically inactive PRL-3 mutations (D72A or C104S) significantly reduced the cell migratory capability. In addition, PRL-3 transfectants demonstrated altered extracellular matrix adhesive property and up-regulated integrin-mediated cell spreading efficiency. Furthermore, we confirmed that PRL-3 could facilitate lung and liver metastasis of B16 cells in an experimental metastasis model in mice, consistent with accelerated proliferation and growth rate both in vitro and in vivo. Together, these observations provide convincing evidence that PRL-3 truly plays a causal role in tumor metastasis.

ARK5 is a tumor invasion-associated factor downstream of Akt signaling

AMP-activated protein kinases (AMPKs) are a class of serine/threonine protein kinases that are activated by an increase in intracellular AMP concentration. They are a sensitive indicator of cellular energy status and have been found to promote tumor cell survival during nutrient starvation. We recently identified a novel AMPK catalytic subunit family member, ARK5, whose activation is directly regulated by Akt, which, in turn, has been reported to be a key player in tumor malignancy. In this study, we attempted to determine whether ARK5 is involved in tumor malignancy under regulation by Akt. Matrigel invasion assays demonstrated that both overexpressed and endogenous ARK5 showed strong activity dependent on Akt. In addition, ARK5 expression induced activation of matrix metalloproteinase 2 (MMP-2) and MMP-9 following new expression of membrane type 1 MMP (MT1-MMP), and the MT1-MMP expression induced by ARK5 was initiated by rapamycin-sensitive signaling. In nude mice, ARK5 expression was associated with a significant increase in tumor growth and significant suppression of necrosis in tumor tissue. Interestingly, only the ARK5-overexpressing PANC-1 cell line (P/ARK) tumor showed invasion and metastasis in nude mice, although Akt was activated in tumors derived from both P/ARK and its parental cell line. We report that a novel AMPK catalytic subunit family member, ARK5, plays a key role in tumor malignancy downstream of Akt.

Natural mechanisms protecting against cancer

Carcinogenesis is a multistage process. At each step of this process, there are natural mechanisms protecting against development of cancer. The majority of cancers in humans is induced by carcinogenic factors present in our environment including our food. However, some natural substances present in our diet or synthesized in our cells are able to block, trap or decompose reactive oxygen species (ROS) participating in carcinogenesis. Carcinogens can also be removed from our cells. If DNA damage occurs, it is repaired in most of the cases. Unrepaired DNA alterations can be fixed as mutations in proliferating cells only and mutations of very few strategic genes can induce tumor formation, the most relevant are those activating proto-oncogenes and inactivating tumor suppressor genes. A series of mutations and/or epigenetic changes is required to drive transformation of a normal cell into malignant tumor. The apparently unrestricted growth has to be accompanied by a mechanism preserving telomeres which otherwise shorten with succeeding cell divisions leading to growth arrest. Tumor can not develop beyond the size of 1-2mm in diameter without the induction of angiogenesis which is regulated by natural inhibitors. To invade the surrounding tissues epithelial tumor cells have to lose some adhesion molecules keeping them attached to each other and to produce enzymes able to dissolve the elements of the basement membrane. On the other hand, acquisition of other adhesion molecules enables interaction of circulating tumor cells with endothelial cells facilitating extravasation and metastasis. One of the last barriers protecting against cancer is the activity of the immune system. Both innate and adaptive immunity participates in anti-tumor effects including the activity of natural killer (NK) cells, natural killer T cells, macrophages, neutrophils and eosinophils, complement, various cytokines, specific antibodies, and specific T cytotoxic cells. Upon activation neutrophils and macrophages are able to kill tumor cells but they can also release ROS, angiogenic and immunosuppressive substances. Many cytokines belonging to different families display anti-tumor activity but their role in natural anti-tumor defense remains largely to be established.

Heparanase: a key enzyme in invasion and metastasis of gastric carcinoma

Previous reports have shown that the biochemical activity of heparanase is significantly correlated with the invasion and metastasis of malignant cells in vitro. Recently, it was found that the human heparanase gene was cloned and highly expressed in malignant cell lines and human solid malignant tumors. In the present study, we investigated the heparanase mRNA expression by using in situ hybridization in 116 paraffin-embedded tissues of primary gastric carcinomas. To explore its clinicopathologic significance, it was detected in the various steps of tumor progression and then compared with prognostic indicators. As a result, the heparanase expression was more prevalent in late-stage rather than early-stage carcinomas (P <.0001) and was more frequent in tumors of large size (P =.0212). Expression also correlated with lymphatic (P =.0086) and venous (P =.0171) invasion and with negative prognostic factors such as lymph nodal (P <.0001) and distant (P =.0221) metastases. However, in a multivariate analysis, messenger RNA expression of heparanase was not an independent prognostic factor. It was concluded that heparanase might play an important role in the development of invasion and metastasis of the gastric cancer. It was indicated that patients with heparanase-positive gastric carcinoma would have a greater chance of metastasis with a poor prognosis.

U0126, a mitogen-activated protein kinase kinase inhibitor, inhibits the invasion of human A375 melanoma cells

The anti-invasive ability of the mitogen-activated protein kinase (MAPK) kinase inhibitor, U0126, was examined in human A375 melanoma cells in vitro. The effect was compared to that of PD98059, another commonly used MEK (MAPK kinase) inhibitor. U0126 or PD98059 showed a dose-dependent inhibition of A375 cell invasion through growth factor-reduced Matrigel. U0126 was more potent than PD98059 in suppressing tumor cell invasion. Both compounds significantly decreased urokinase plasminogen activator (uPA) and matrix metalloproteinases-9 (MMP-9) concentrations in conditioned media. At 5 microM, U0126 inhibited phosphorylation of the MEK 1/2 to a non-detectable level within 24 h. The phosphorylation of extracellular signal-related kinase 1/2 was also dramatically suppressed by the treatment with 10 microM U0126 or 40 microM PD98059. Both compounds suppressed the protein expression of c-Jun, but not c-Fos. The expression of uPA and MMP-9 was also inhibited. Our data suggest that U0126 is an effective agent in inhibiting human A375 melanoma cell invasion and that the effect is partially due to the decreased production of uPA and MMP-9.

CD151 enhances cell motility and metastasis of cancer cells in the presence of focal adhesion kinase

We have examined the role of the protein CD151 in cell motility, invasion and metastasis of cancer cells by using CD151-overexpressing cells prepared by transfection of CD151 cDNA into three cancer cell lines established from different origins; a human colon cancer RPMI4788, a human glioblastoma A172 and a human fibrosarcoma HT1080. Invasion into Matrigel and cell motility of all 3 CD151-overexpressing cancer cells were enhanced significantly when compared to control parental cells. Pulmonary metastasis of 2 metastatic CD151-overexpressing cancer cell lines, RPMI4788/CD151 and HT1080/CD151, was higher than that of control parental cells and was markedly inhibited by anti-CD151 monoclonal antibody (MAb), SFA1.2B4. To examine whether focal adhesion kinase (FAK) is associated with promotion of cell motility and invasion of cancer cells through CD151, we transfected human CD151 cDNA into FAK (+/+) or FAK (-/-) fibroblasts that were isolated from embryos in FAK-deficient mice and compared invasion into Matrigel and cell motility between each CD151-transfected cells and controls. The invasion into Matrigel and cell motility of CD151-transfected FAK (+/+) fibroblasts increased significantly above those of parental cells and were inhibited by anti-CD151 MAb, whereas those of CD151-transfected FAK (-/-) fibroblasts were not enhanced at all and were not blocked by anti-CD151 MAb. These findings indicate that the CD151 molecule enhances cell motility, invasion and metastasis of cancer cells and that FAK is needed for these events through CD151.

Molecular pathogenesis of oral squamous carcinoma

Oral squamous carcinogenesis is a multistep process in which multiple genetic events occur that alter the normal functions of oncogenes and tumour suppressor genes. This can result in increased production of growth factors or numbers of cell surface receptors, enhanced intracellular messenger messenger signalling, and/or increased production of transcription factors. In combination with the loss of tumour suppressor activity, this leads to a cell phenotype capable of increased cell proliferation, with loss of cell cohesion, and the ability to infiltrate local tissue and spread to distant sites. Recent advances in the understanding of the molecular control of these various pathways will allow more accurate diagnosis and assessment of prognosis, and might lead the way for more novel approaches to treatment and prevention.

Expression of matrix metalloproteinases and tissue inhibitor of metalloproteinases in laryngeal and pharyngeal squamous cell carcinoma: A quantitative analysis

Squamous cell carcinomas of the head and neck are known for their aggressive growth and propensity to metastasize. Invasion is facilitated by matrix metalloproteineases (MMPs). Tissue inhibitors of MMPs (TIMPs) negatively regulate MMP activity. MMP and TIMP expression in head and neck squamous cell carcinomas was determined by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). qRT-PCR allows measurement of several mRNAs from as little as 4 microg of total cellular RNA. We measured MMP-1, MMP-2, MMP-9, and TIMP-1 expression in 8 specimens of primary tumors and adjacent normal tissue. MMP-1 was overexpressed in 6 of 8 tumors, and MMP-9 was overexpressed in 4 of 7 tumors. MMP-2 was expressed in 3 of 8 tumors and 3 of 8 normal samples. TIMP-1 was expressed in all specimens. This work demonstrates that qRT-PCR can be used to examine expression of specific mRNAs in clinical specimens. Therefore this method provides another tool for the molecular analysis of tumors.

Interaction between CD44 and the repeat domain of ankyrin promotes hyaluronic acid-mediated ovarian tumor cell migration

The adhesion molecule, CD44, interacts with ankyrin within its cytoplasmic domain and binds to hyaluronic acid (HA) at its extracellular domain. In this study, we focused on the functional domain in ankyrin (in particular, the ankyrin repeat domain [ARD]) responsible for CD44 binding and its role in regulating HA-mediated ovarian tumor cell function. Using recombinant fragments of ankyrin (e.g., ARD and subdomain 1 [S1, aa1-aa217], subdomain 2 [S2, aa218-aa381], subdomain 3 [S3, aa382-aa612], and subdomain 4 [S4, aa613-aa834]) and in vitro binding assays, we determined that the S2 but not S1, S3, or S4 of ARD is the primary ankyrin binding region for CD44. Microinjection of antiglutathione S-transferase (GST)-tagged S2 or GST-tagged ARD fusion protein into CD44-positive ovarian tumor cells (e.g., SKOV3 cell line) promotes ankyrin association with CD44 in plaque-like structures and membrane projections. Additionally, we demonstrated that transfection of SKOV3 cells with S2cDNA or ARD cDNA results in an upregulation of HA-mediated tumor cell migration. Taken together, we believe that the S2 of the ARD plays a pivotal role in the direct binding to CD44 and promotes the cytoskeleton activation required for HA-mediated function such as ovarian tumor cell migration.

Molecular biology of breast cancer metastasis. Genetic regulation of human breast carcinoma metastasis

The present is an overview of recent data that describes the genetic underpinnings of the suppression of cancer metastasis. Despite the explosion of new information about the genetics of cancer, only six human genes have thus far been shown to suppress metastasis functionally. Not all have been shown to be functional in breast carcinoma. Several additional genes inhibit various steps of the metastatic cascade, but do not necessarily block metastasis when tested using in vivo assays. The implications of this are discussed. Two recently discovered metastasis suppressor genes block proliferation of tumor cells at a secondary site, offering a new target for therapeutic intervention.

Promotion of tumor invasion by cooperation of granulocytes and macrophages activated by anti-tumor antibodies

We investigated the potential role of anti-tumor antibodies and tumor antigens in the formation of immune complexes which promote matrix degradation and angiogenesis. B-cell deficient or B-cell depleted mice showed a reduction in tumor invasion and metastasis. In vitro invasion assays and in vivo models of metastasis showed that anti-sTn antibodies and sTn tumor antigens form complexes which induce granulocytes and macrophages together to mediate tumor invasion and metastasis by processes including extracellular matrix degradation and angiogenesis. These results suggest the existence of a tumor promoting role of a B-cell immune response induced by shed tumor associated antigens of solid, nonlymphoid tumors.

RalA requirement for v-Src- and v-Ras-induced tumorigenicity and overproduction of urokinase-type plasminogen activator: involvement of metalloproteases

Overproduction of urokinase-type plasminogen activator (uPA) and metalloproteases (MMPs) is strongly correlated with tumorigenicity and with invasive and metastatic phenotypes of human and experimental tumors. We demonstrated previously that overproduction of uPA in tumor cells is mediated by a phospholipase D (PLD)- and protein kinase C-dependent mechanism. The oncogenic stimulus of v-Src and v-Ras results in the activation of PLD, which is dependent upon the monomeric GTPase RalA. We have therefore investigated whether RalA plays a role in uPA and MMP overproduction that is observed in response to oncogenic signals. We report here that NIH3T3 cells transformed by both v-Src and v-Ras, constitutively overproduce uPA and that expression of a dominant negative RalA mutant (S28N) blocks overproduction of uPA in both the v-Src-and v-Ras-transformed cells. v-Src and v-Ras also induced an upregulation of the activity of MMP-2 and MMP-9 as detected by zymograms, however only the v-Src induction correlated with MMP protein levels detected by Western blot analysis. The dominant negative RalA mutant blocked increased MMP-2 and 9 overproduction induced by v-Src, but not the increased activity of MMP-2 and 9 induced by v-Ras. And, consistent with a role for the RalA/PLD pathway in mitogenesis and tumor development, the dominant negative RalA mutant completely blocked tumor formation by v-Src- and v-Ras-transformed NIH3T3 cells injected subcutaneously in syngeneic mice. The data presented here implicate RalA and PLD as signaling mediators for tumor formation and protease production by transformed cells.

Receptor-mediated and enzyme-dependent targeting of cytotoxic anticancer drugs

This review is a survey of various approaches to targeting cytotoxic anticancer drugs to tumors primarily through biomolecules expressed by cancer cells or associated vasculature and stroma. These include monoclonal antibody immunoconjugates; enzyme prodrug therapies, such as antibody-directed enzyme prodrug therapy, gene-directed enzyme prodrug therapy, and bacterial-directed enzyme prodrug therapy; and metabolism-based therapies that seek to exploit increased tumor expression of, e.g., proteases, low-density lipoprotein receptors, hormones, and adhesion molecules. Following a discussion of factors that positively and negatively affect drug delivery to solid tumors, we concentrate on a mechanistic understanding of selective drug release or generation at the tumor site.

Cisplatin resistant glioblastoma cells may have increased concentration of urokinase plasminogen activator and plasminogen activator inhibitor type 1

Gliomas are the most common form of intrinsic primary brain tumors, that extensively invade the surrounding normal brain tissue. The failure of chemotherapy treatment of these tumors is chiefly attributed to drug-resistance. From human glioblastoma we developed two cell sublines resistant to cisplatin due to acute (AT cells) or continuous (CT cells) treatment with clinically relevant doses of cisplatin. We examined their sensitivity to different cytostatics by colorimetric MTT assay. The concentrations of urokinase plasminogen activator (uPA) and plasminogen activator inhibitor type 1 (PAI-1) were determined by the ELISA assay. The results reveal that both AT and CT cells became resistant to cisplatin and vincristine; AT cells became resistant also to etoposide. Both AT and CT cells did not significantly change their sensitivity to doxorubicin, 5-fluorouracil and chlorambucil. Concentrations of uPA and PAI-1 were increased in CT cells, with no change in AT cells. In the conditioned medium of both, AT and CT cells, the level of uPA were increased. No differences in concentrations of PAI-1 in the conditioned medium of these cells were found. Thus, our results show that drug-resistance of glioblastoma cells may be accompanied with the increased levels of markers for tumor invasion.

Sustained activation of the mitogen-activated protein kinase pathway. A mechanism underlying receptor tyrosine kinase specificity for matrix metalloproteinase-9 induction and cell migration

Activation of the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) pathway is required for ligand-dependent regulation of numerous cellular functions by receptor tyrosine kinases. We have shown previously that although many receptor tyrosine kinase ligands are mitogens for keratinocytes, cell migration and induction of the 92-kilodalton gelatinase/matrix metalloproteinase (MMP)-9 are selectively regulated by the epidermal growth factor and scatter factor/hepatocyte growth factor receptors. In this report we present evidence of an underlying mechanism to account for these observed differences in receptor tyrosine kinase-mediated response. Ligands that are mitogenic, but do not induce MMP-9 or colony dispersion, transiently activate the p42/p44 ERK/MAP kinases. In contrast, ligands that stimulate MMP-9 induction and colony dispersion induced sustained activation of these kinases. The functional significance of sustained MAPK activation was demonstrated by inhibition of the MAP kinase kinase MEK1. Disruption of the prolonged signal by addition of the MEK1 inhibitor PD 98059 up to 4 h after growth factor stimulation substantially impaired ligand-dependent colony dispersion and MMP-9 induction. These findings support the conclusion that duration of MAPK activation is an important determinant for certain growth factor-mediated functions in keratinocytes.

Contributions of the epidermal growth factor receptor to keratinocyte motility

The epidermal growth factor (EGF) receptor plays a central role in numerous aspects of keratinocyte biology. In normal epidermis, the EGF receptor is important for autocrine growth of this renewing tissue, suppression of terminal differentiation, promotion of cell survival, and regulation of cell migration during epidermal morphogenesis and wound healing. In wounded skin, the EGF receptor is transiently up-regulated and is an important contributor to the proliferative and migratory aspects of wound reepithelialization. In keratinocytic carcinomas, aberrant expression or activation of the EGF receptor is common and has been proposed to play a role in tumor progression. Many cellular processes such as altered cell adhesion, expression of matrix degrading proteinases, and cell migration are common to keratinocytes during wound healing and in metastatic tumors. The EGF receptor is able to regulate each of these cellular functions and we propose that transient and dynamic elevation of EGF receptor during wound healing, or constitutive overexpression in tumors, provides an important contribution to the migratory and invasive potential of keratinocytes.

An orthotopic floor-of-mouth cancer model allows quantification of tumor invasion

OBJECTIVES

To establish an orthotopic murine floor-of-mouth cancer model for the analysis of the role of proteases such as urokinase-type plasminogen activator (u-PA) and the matrix metalloprotease MMP-9 (MMP-9) in in vivo invasion.

STUDY DESIGN

Randomized, prospective animal study.

METHODS

Two human squamous cell carcinoma cell lines, UM-SCC-1 and 022, were assayed via zymography for their in vitro secretion levels of u-PA and MMP-9. Both cell lines (5 x 10(6) cells) were injected into the cervical subcutaneous tissues of female athymic nude (nu/nu) mice superficial to the mylohyoid muscle. Mice were sacrificed after 30 days, and tumor invasion characteristics were histologically compared. Additional mice were then inoculated with invasive UM-SCC-1 cells and sacrificed 10, 30, and 40 days after inoculation to identify distinct stages of invasion.

RESULTS

In vitro secretion levels of MMP-9 and activity of u-PA were higher in UM-SCC-1 cells than in 022 cells. In the in vivo studies, tumors formed from 022 cells were found to be noninvasive, whereas tumors derived from UM-SCC-1 cells progressed through distinct and readily identifiable histologic stages of invasion. These stages included invasion of adjacent muscle layers (mylohyoid, geniohyoid, and genioglossus muscles) and of associated structures (blood vessels, bone, nerve, and regional lymph nodes). A staging system was devised accordingly.

CONCLUSION

We developed an in vivo quantitative cancer invasion model that allows determination of the effect of the expression and activity levels of the proteases MMP-9 and u-PA. Tumor invasion occurred in an orderly and stepwise fashion involving muscles and related vascular, nervous, and bony structures of the floor of the mouth and tongue. This orderly invasion allowed the development of a staging system. We anticipate that this model will have wide applicability in the study of in vivo tumor response to a variety of novel therapeutic approaches.

Mechanism of lymph node metastases: current concepts

Advances in head and neck surgical techniques with aggressive adjuvant treatment have reduced the incidence of locoregional failure in many types of head and neck cancer. Failure to control distant disease, however, remains of the most frustrating aspects in the care of these patients. A strong foundation in the biology of invasion and metastasis is necessary to understand more clearly the reasons for the development of distant and locally recurrent disease. This article focuses on basic mechanisms of invasion and metastasis in head and neck squamous cell carcinoma.

CD44v(3,8-10) is involved in cytoskeleton-mediated tumor cell migration and matrix metalloproteinase (MMP-9) association in metastatic breast cancer cells

In the present study, we have employed a unique breast cancer cell line (Met-1, which was derived from a high metastatic potential tumor in transgenic mice expressing polyomavirus middle T oncogene) to study the role of CD44 variant isoform(s) in the regulation of metastatic breast tumor cell behavior. The results of reverse transcriptase-polymerase chain reaction, Southern blot, nucleotide sequencing, immunoprecipitation, and immunoblot analyses indicated that these cells express a major CD44 isoform (molecular weight approximately 260 kDa) containing a v3,8-10 exon insertion (designated as CD44v3,8-10). In addition, we have determined that CD44v3,8-10 binds specifically to the cytoskeletal proteins such as ankyrin. Biochemical analyses, using competition binding assays and a synthetic peptide identical to NGGNGTVEDRKPSEL (a sequence located between aa480 and aa494 of CD44v3,8-10) indicate that this 15-amino acid peptide binds specifically to the cytoskeletal protein ankyrin (but not to fodrin or spectrin). This peptide competes effectively for ankyrin binding to CD44v3,8-10. Therefore, we believe that the sequence 480NGGNGTVEDRKPSE494L, located at the cytoplasmic domain of CD44v3,8-10, is required for the ankyrin binding. We have also detected that CD44v3,8-10-containing Met-1 cells are capable of forming membrane spikes or "invadopodia" structures and undergo active migration processes. Treatments of Met-1 cells with certain agents including anti-CD44v3 antibody, cytochalasin D (a microfilament inhibitor), and W-7 (a calmodulin antagonist), but not colchicine (a microtubule disrupting agent) effectively inhibit "invadopodia" formation and subsequent tumor cell migration. Further analyses using zymography assays and double immunofluorescence staining indicated that CD44v3,8-10 is closely associated with the active form of matrix metalloproteinase, MMP-9, in a complex within "invadopodia" structures. These findings suggest that CD44v3,8-10 plays an important role in linking ankyrin to the membrane-associated actomyosin contractile system required for "invadopodia" formation (coupled with matrix degradation activities) and tumor cell migration during breast cancer progression.

A zinc chelator inhibiting gelatinases exerts potent in vitro anti-invasive effects

Matrix metalloproteinases are zinc metalloenzymes involved in remodelling of the extracellular matrix. We compared the anti-invasive properties of a zinc ejector matrix metalloproteinase inhibitor with those of reference compounds (hydroxamic acid-based BB-94 and Ro-31-9790) which form inactive ternary complexes with the enzymes and the catalytic zinc. We show that the compound undecadenedioic acid bis-[[2-(3 H-imidazol-4-yl)-ethyl]-amide] (S 30372) is active against gelatinases, chelates zinc and exhibits enzymatic features compatible with the potential to extract zinc from gelatinases. We then used five invasive cell lines in the Matrigel invasion chamber assay (NIH-3T3 fibroblasts, Lewis lung carcinoma cells, EJ138 and J82 bladder carcinoma and HT1080 fibrosarcoma cells). With the exception of J82 cells which were unaffected by the three inhibitors, all remaining cells were substantially more sensitive to S 30372 in terms of maximal inhibition of invasion attained. This suggests that matrix metalloproteinase inhibitors with zinc chelating/ejecting properties may be more efficient in preventing tumor progression.

Tumor and endothelial cell invasion of basement membranes. The matrigel chemoinvasion assay as a tool for dissecting molecular mechanisms

The spread of cancer cells from a primary tumor to distant organs is the major cause of death of cancer patients. Metastatic lesions are often resistent to cancer therapy because of the progressive phenotypic changes that they have undergone. Several genetic and epigenetic factors, both in the cell and in the host, contribute to the development of tumor progression towards metastases. In this review we will analyze the steps involved in tumor metastases, which can be potential targets for anti-metastatic therapy. One of the most critical events in cancer metastasis is the invasion of basement membranes. An assay which we developed over ten years ago, the matrigel "chemoinvasion" assay, has been a useful tool for studying the mechanisms involved in tumor and endothelial cell invasion of basement membranes and for the screening of anti-invasive agents. Here we will describe the assay and review some of the major results obtained with it.

Nuclear and non-nuclear targets of genotoxic agents in the induction of gene expression. Shared principles in yeast, rodents, man and plants

The interplay between environmental cues and the genetic response is decisive for the development, health and well-being of an organism. For some environmental factors a narrow margin separates beneficial and toxic impacts. With the increasing exposure to UV-B this dichotomy has reached public attention. This review will be concerned with the mechanisms that mediate a cellular genetic response to noxious agents. The toxic stimuli find access to the regulatory network inside cells by interacting at several points with cellular molecules - a process that converts the 'outside information' into 'cellular language'. As a consequence of such interactions, many adverse agents cause massive signal transduction and changes of gene expression. There is an interesting conservation of the mechanisms from yeast to man. An understanding of the genetic programs and of their phenotypic consequences is lagging behind.