New insights into pharmacological tools to TR(i)P cancer up.

The aim of this review is to address the recent advances regarding the use of pharmacological agents to target transient receptor potential (TRP) channels in cancer and their potential application in therapeutics. Physiologically, TRP channels are responsible for cation entry (Ca(2+) , Na(+) , Mg(2+) ) in many mammalian cells and regulate a large number of cellular functions. However, dysfunction in channel expression and/or activity can be linked to human diseases like cancer. Indeed, there is growing evidence that TRP channel expression is altered in cancer tissues in comparison with normal ones. Moreover, these proteins are involved in many cancerous processes, including cell proliferation, apoptosis, migration and invasion, as well as resistance to chemotherapy. Among the TRP superfamily, TRPC, TRPV, TRPM and TRPA1 have been shown to play a role in many cancer types, including breast, digestive, gliomal, head and neck, lung and prostate cancers. Pharmacological modulators are used to characterize the functional implications of TRP channels in whole-cell membrane currents, resting membrane potential regulation and intracellular Ca(2+) signalling. Moreover, pharmacological modulation of TRP activity in cancer cells is systematically linked to the effect on cancerous processes (proliferation, survival, migration, invasion, sensitivity to chemotherapeutic drugs). Here we describe the effects of such TRP modulators on TRP activity and cancer cell phenotype. Furthermore, the potency and specificity of these agents will be discussed, as well as the development of new strategies for targeting TRP channels in cancer.

Transient receptor potential melastatin 7 is involved in oestrogen receptor-negative metastatic breast cancer cells migration through its kinase domain.

Oestrogen receptor negative (ER(-)) invasive ductal carcinoma (IDC) represents a significant clinical challenge and therefore prompts the discovery of novel biomarkers. Transient receptor potential melastatin 7 (TRPM7), a channel protein that also contains a regulatory kinase domain, is overexpressed in IDC and regulates migration. However, the molecular mechanism remains poorly defined. Here, we examined whether TRPM7 regulates migration by its channel function or by its kinase domain. A Magnesium Inhibited Cation current was recorded in two ER(-) highly metastatic breast cancer cell lines. Down-regulation of TRPM7 neither affected Ca(2+)-, nor Mg(2+)-homoeostasis but significantly reduced cell migration via a Ca(2+)-independent pathway. Notably, the overexpression of the truncated kinase domain form of TRPM7 decreased cell migration, while the overexpression of the wild-type form strongly increased it. Concomitantly, TRPM7 silencing reduced the myosin IIA heavy chain phosphorylation. Furthermore, we found higher TRPM7 expression in ER(-) IDC tissues and lymph nodes than in the non-invasive tumoural samples. In conclusion, TRPM7 plays a critical role in breast cancer cell migration through its kinase domain, and our data support the consideration of using TRPM7 as a novel biomarker and a potential therapeutic target in the treatment of human ER(-) IDC.

Lactoferrin upregulates the expression of CD4 antigen through the stimulation of the mitogen-activated protein kinase in the human lymphoblastic T Jurkat cell line.

The main biological properties of lactoferrin are thought to concern inflammation and immunomodulation processes, including maturation of immature B and T cells. Lactoferrin accelerates T-cell maturation by inducing the expression of the CD4 surface marker. In this report, using the Jurkat T-cell line, we have shown that lactoferrin upregulates the expression of CD4 antigen through the activation of a transduction pathway. Using an anti-phosphotyrosine antibody, lactoferrin was demonstrated to induce a cascade of phosphorylation of numerous proteins on their tyrosine residues. This tyrosine-phosphorylation was transient, reaching maxima between 5 and 10 min. We also identified the mitogen-activated protein kinase (MAP kinase) which presented an enhanced catalytic activity, reaching a maximum at 10 min of incubation with lactoferrin. Moreover, the use of inhibitors such as genistein and PD98059, tyrosine kinases and MAP kinase kinase (or MEK) inhibitors respectively, allowed us to correlate the activation of MAP kinase with the upregulation of CD4 expression. Finally, using Lck-defective Jurkat cells, our results showed that the p56(lck) (Lck) kinase is necessary for MAP kinase activity and CD4 expression. This paper demonstrates that lactoferrin activates transduction pathway(s) in lymphoblastic T-cells, and that Lck and the Erk2 isoform of MAP kinase are implicated in the upregulation of CD4, induced by lactoferrin in these cells.

Tumor necrosis factor-alpha increases lactoferrin transcytosis through the blood-brain barrier.

Lactoferrin (Lf) is an iron-binding protein involved in host defense against infection and severe inflammation, which accumulates in the brain during neurodegenerative disorders. Prior to determining Lf function in pathological brain tissues, we investigated its transport through the blood-brain barrier (BBB) in inflammatory conditions. For this purpose, we used a reconstituted BBB model consisting of the coculture of bovine brain capillary endothelial cells (BBCECs) and astrocytes in the presence of tumor necrosis factor-alpha (TNF-alpha). As TNF-alpha can be either synthesized by brain glial cells or present in circulating blood, BBCECs were exposed to this cytokine at their luminal or abluminal side. We have been able to demonstrate that in the presence of TNF-alpha, whatever the type of exposure, BBCECs were activated and Lf transport through the activated BBCECs was markedly increased. Lf was recovered intact at the abluminal side of the cells, suggesting that increased Lf accumulation may occur in immune-mediated pathophysiology. This process was transient as 20 h later, cells were in a resting state and Lf transendothelial traffic was back to normal. The enhancement of Lf transcytosis seems not to involve the up-regulation of the Lf receptor but rather an increase in the rate of transendothelial transport.