CXCR7 receptors facilitate the progression of colon carcinoma within lung not within liver

Background:

Liver and lung metastases are the predominant cause of colorectal cancer (CRC)-related mortality. Chemokine-receptor pairs have a critical role in determining the metastatic progression of tumours. Our hypothesis was that disruption of CXCR7/CXCR7 ligands axis could lead to a decrease in CRC metastases.

Methods:

Primary tumours and metastatic tissues from patients with CRC were tested for the expression of CXCR7 and its ligands. Relevance of CXCR7/CXCR7 ligands for CRC metastasis was then investigated in mice using small pharmacological CXCR7 antagonists and CRC cell lines of human and murine origins, which – injected into mice – enable the development of lung and liver metastases.

Results:

Following injection of CRC cells, mice treated daily with CXCR7 antagonists exhibited a significant reduction in lung metastases. However, CXCR7 antagonists failed to reduce the extent of liver metastasis. Moreover, there were subtle differences in the expression of CXCR7 and its ligands between lung and liver metastases.

Conclusion:

Our study suggests that the activation of CXCR7 on tumour blood vessels by its ligands may facilitate the progression of CRC within lung but not within liver. Moreover, we provide evidence that targeting the CXCR7 axis may be beneficial to limit metastasis from colon cancer within the lungs.

Signal transduction pathways involved in soluble fractalkine-induced monocytic cell adhesion

Fractalkine displays features that distinguishes it from the other chemokines. In particular, besides its chemoattractant action it promotes, under physiologic flow, the rapid capture and the firm adhesion of a subset of leukocytes or intervenes in the neuron/microglia interaction. This study verified that indeed the human monocytic MonoMac6 cell line adheres to fibronectin-coated filters in response to soluble fractalkine (s-FKN). s-FKN stimulates, with distinct time courses, extracellular signal-related kinases (ERK1 and ERK2) and stress-activated protein kinases (SAPK1/JNK1 and SAPK2/p38). Both p60 Src and p72 Syk were activated under s-FKN stimulation with a rapid kinetic profile compatible with a downstream regulation on the mitogen-activated protein kinase (MAPK) congeners. The use of specific tyrosine kinase inhibitors revealed that the ERK pathway is strictly controlled by Syk, whereas c-Src up-regulated the downstream SAPK2/p38. In contrast, the SAPK1/JNK1 pathway was not regulated by any of these nonreceptor tyrosine kinases. The s-FKN-mediated increased adherence of MonoMac6 cells was partially inhibited by SB202190, a broad SAPKs inhibitor, PD98059, an MEK inhibitor, LY294002, a phosphatidyl inositol 3-kinase inhibitor, and a pertussis toxin-sensitive G protein. These data highlight that the integration of a complex array of signal transduction pathways is necessary to complete the full s-FNK-dependent adherence of human monocytic cells to fibronectin. (Blood. 2001;97:2031-2037)

Signal transduction involved in MCP-1-mediated monocytic transendothelial migration

Monocyte chemoattractant protein-1 (MCP-1) is a major chemoattractant for monocytes and T lymphocytes. The MonoMac6 cell line was used to examine MCP-1 receptor-mediated signal transduction events in relation to MCP-1-mediated monocytic transendothelial migration. MCP-1 stimulates, with distinct time courses, extracellular signal-related kinases (ERK1 and ERK2) and stress-activated protein kinases (SAPK1/JNK1 and SAPK2/p38). SAPK1/JNK1 activation was blocked by piceatannol, indicating that it is regulated by Syk kinase, whereas SAPK2/p38 activation was inhibited by PP2, revealing an upstream regulation by Src-like kinases. In contrast, ERK activation was insensitive to PP2 and piceatannol. Pertussis toxin, a blocker of Go/Gi proteins, abrogated MCP-1-induced ERK activation, but was without any effect on SAPK1/JNK1 and SAPK2/p38 activation. These results underscore the major implication of Go/Gi proteins and nonreceptor tyrosine kinases in the early MCP-1 signaling. Furthermore, MCP-1-mediated chemotaxis and transendothelial migration were significantly diminished by a high concentration of SB202190, a broad SAPK inhibitor, or by SB203580, a specific inhibitor of SAPK2/p38, and abolished by pertussis toxin treatment. Altogether, these data suggest that coordinated action of distinct signal pathways is required to produce a full response to MCP-1 in terms of monocytic locomotion.

Src-regulated extracellular signal-related kinase and Syk-regulated c-Jun N-terminal kinase pathways act in conjunction to induce IL-1 synthesis in response to microtubule disruption in HL60 cells

A microtubule reorganization is often observed during cellular contacts that are associated to IL-1 production. Here, we show that in HL60 cells, vincristine, a microtubule-disrupting agent that induces a strong production of IL-1, triggers the activation of both extracellular signal-related kinase (ERK) and c-Jun N-terminal kinase (JNK-1). While ERK activation is rapid and transient, peaking at 10 min, the JNK1 activation is delayed and more sustained reaching a maximum at 2 h. ERK activation was blocked by CP 118556, indicating it is regulated by a Src-like kinase, while JNK1 was inhibited by piceatannol, revealing an upstream regulation by Syk. Each kind of the nonreceptor tyrosine kinase blockers efficiently inhibits the vincristine-induced IL-1 production and diminishes the level of IL-1 transcripts, indicating that the ERK and JNK pathways act coordinately to elicit the transcription of the IL-1 gene. Furthermore, we found that pertussis toxin, a blocker of Go/Gi proteins, abrogated the vincristine-induced activation of both Src and Syk. Our data support a model where the status of microtubule polymerization influences the activity of Go or Gi proteins that control, in turn, two independent Src/ERK and Syk/JNK1 cascades that are both necessary to sustain IL-1 synthesis.

Microtubule integrity regulates src-like and extracellular signal-regulated kinase activities in human pro-monocytic cells. Importance for interleukin-1 production

We have demonstrated previously that microtubule depolymerization by colchicine in human monocytes induces selective production of interleukin-1 (IL-1) (Manié, S., Schmid-Alliana, A., Kubar, J., Ferrua, B., and Rossi, B. (1993) J. Biol. Chem. 268, 13675-13681). Here, we provide evidence that disruption of the microtubule structure rapidly triggers extracellular signal-regulated kinase (ERK) activation, whereas it was without effect on SAPK2 activity, which is commonly acknowledged to control pro-inflammatory cytokine production. This process involves the activation of the entire cascade including Ras, Raf-1, MEK1/2, ERK1, and ERK2. Activation of ERKs is followed by their nuclear translocation. Although other SAPK congeners might be activated upon microtubule depolymerization, the activation of ERK1 and ERK2 is mandatory for IL-1 production as shown by the blocking effect of PD 98059, a specific MEK1/2 inhibitor. Additionally, we provide evidence that microtubule disruption also induces the activation of c-Src and Hck activities. The importance of Src kinases in the mediation of the colchicine effect is underscored by the fact that CP 118556, a specific inhibitor of Src-like kinase, abrogates both the colchicine-induced ERK activation and IL-1 production. This is the first evidence that ERK activation is an absolute prerequisite for induction of this cytokine. Altogether, our data lend support to a model where the status of microtubule integrity controls the level of Src activities that subsequently activate the ERK kinase cascade, thus leading to IL-1 production.

Extracellular ATP and UTP control the generation of reactive oxygen intermediates in human macrophages through the opening of a charybdotoxin-sensitive Ca2+-dependent K+ channel

Human monocyte-derived macrophages possess a NADPH oxidase that catalyzes superoxide formation upon phagocytosis. Extracellular ATP per se does not activate NADPH oxidase but potentiates superoxide generation triggered by opsonized zymosan. UTP can substitute for ATP with the same efficiency, suggesting that ATP mediates its effects specifically through P2U receptors. Extracellular UTP stimulates a rapid increase in cytoplasmic Ca2+ concentration in monocytic cells, which results from a release of intracellular Ca2+ stores. Moreover, UTP-induced calcium increase is sufficient to activate a charybdotoxin-sensitive Ca2+-dependent outward K+ channel (K(Ca)). The activity of this channel develops between 0.1 and 1.0 microM free cytoplasmic Ca2+ concentration; it is half-blocked by 10 nM charybdotoxin but insensitive to iberiotoxin. Under asymmetrical K+ conditions, this K(Ca) channel does not depend on membrane potential and is characterized by a linear single-current voltage relationship in the voltage range of -100 to +50 mV, giving a unitary conductance of 10 pico-Siemens. Interestingly, ATP/UTP-induced oxygen radicals release was inhibited by charybdotoxin in the same range of concentration as the UTP-induced K(Ca) channel. Furthermore, we show that ATP or UTP fail to enhance oxygen radicals production before K(Ca) channel is expressed (3 days). The electrogenic nature of the NADPH oxidase, i.e., its level of activation, being dependent on the plasmic membrane potential, might provide the causal link between the reactive oxygen intermediates generation and the opening of the K(Ca) channel.

Extracellular ATP and UTP control the generation of reactive oxygen intermediates in human macrophages through the opening of a charybdotoxin-sensitive Ca2+-dependent K+ channel

Human monocyte-derived macrophages possess a NADPH oxidase that catalyzes superoxide formation upon phagocytosis. Extracellular ATP per se does not activate NADPH oxidase but potentiates superoxide generation triggered by opsonized zymosan. UTP can substitute for ATP with the same efficiency, suggesting that ATP mediates its effects specifically through P2U receptors. Extracellular UTP stimulates a rapid increase in cytoplasmic Ca2+ concentration in monocytic cells, which results from a release of intracellular Ca2+ stores. Moreover, UTP-induced calcium increase is sufficient to activate a charybdotoxin-sensitive Ca2+-dependent outward K+ channel (K(Ca)). The activity of this channel develops between 0.1 and 1.0 microM free cytoplasmic Ca2+ concentration; it is half-blocked by 10 nM charybdotoxin but insensitive to iberiotoxin. Under asymmetrical K+ conditions, this K(Ca) channel does not depend on membrane potential and is characterized by a linear single-current voltage relationship in the voltage range of -100 to +50 mV, giving a unitary conductance of 10 pico-Siemens. Interestingly, ATP/UTP-induced oxygen radicals release was inhibited by charybdotoxin in the same range of concentration as the UTP-induced K(Ca) channel. Furthermore, we show that ATP or UTP fail to enhance oxygen radicals production before K(Ca) channel is expressed (3 days). The electrogenic nature of the NADPH oxidase, i.e., its level of activation, being dependent on the plasmic membrane potential, might provide the causal link between the reactive oxygen intermediates generation and the opening of the K(Ca) channel.