Acidic extracellular pH increases calcium influx‐triggered phospholipase D activity along with acidic sphingomyelinase activation to induce matrix metalloproteinase‐9 expression in mouse metastatic melanoma

Abstract

Acidic extracellular pH is a common feature of tumor tissues. We have reported that culturing cells at acidic pH (5.4-6.5) induced matrix metalloproteinase-9 expression through phospholipase D, extracellular signal regulated kinase 1 ⁄ 2 and p38 mitogen-activated protein kinases and nuclear factor-jB. Here, we show that acidic extracellular pH signaling involves both pathways of phospholipase D triggered by Ca 2+ influx and acidic sphingomyelinase in mouse B16 melanoma cells. We found that BAPTA-AM [1,2-bis(2-aminophenoxy)-ethane-N,N,N¢,N¢-tetraacetic acid tetrakis (acetoxymethyl) ester], a chelator of intracellular free calcium, and the voltage dependent Ca 2+ channel blockers, mibefradil (for T-type) and nimodipine (for L-type), dose-dependently inhibited acidic extracellular pH-induced matrix metalloproteinase-9 expression. Intracellular free calcium concentration ( 2+ channel blocker and acidic sphingomyelinase inhibitor, attenuated matrix metalloproteinase-9 induction but did not affect calcium influx. We found that acidic sphingomyelinase activity was induced by acidic extracellular pH and that the specific acidic sphingomyelinase inhibitors (perhexiline and desipramine) and siRNA targeting aSMase ⁄ smpd1 could inhibit acidic extracellular pH-induced matrix metalloproteinase-9 expression. BAPTA-AM reduced acidic extracellular pH-induced phospholipase D but not acidic sphingomyelinase acitivity. The acidic Abbreviations aSMase, acidic sphingomyelinase; BAPTA-AM, 1,2-bis(2-aminophenoxy)-ethane-N,N,N¢,N¢-tetraacetic acid tetrakis (acetoxymethyl) ester; CM, conditioned medium; [Ca 2+ ] i ,

How does cancer cell metabolism affect tumor migration and invasion?

“…7 This leads to normal cell death via caspase-mediated activation of p53-dependent apoptotic pathway, 8,17 whereas cancer cells are well equipped to export lactate by MCTs transporters resulting in the acidification of microenvironment. 18 A low pH created by extracellular acidification provides a favorable microenvironment for the activation of proteases, including MMPs, 19 urokinasetype plasminogen activator, 20 25 Therefore, tumor cells become migratory and invasive because they disturb the environment so that it is optimal for their proliferation and toxic to the normal cells with which they compete for space and substrate.…”

“…108 High lactate concentration could induce the necrosis and apoptosis of normal tissues and release of cathepsin B and other proteolytic enzymes, which results in the degradation of extracellular matrix and initiates cancer cell migration. [19][20][21][22][23][24] It is reported that metastasis of tumors is promoted by lactate-induced secretion of hyaluronan that creates a milieu favorable for migration. 109 Intriguingly, lactate itself has been found to induce the migration of cancer cells.…”

Ion channels and transporters in tumour cell migration and invasion

“…Finally, the activity of matrix metalloproteinases has also been linked to Ca 2þ signalling [105,106]. The upregulation of MMP9 requiring Ca 2þ influx can therefore be inhibited by blocking voltage-gated Ca 2þ channels [107].…”

Exchange Protein Directly Activated by Cyclic AMP Increases Melanoma Cell Migration by a Ca2+-Dependent Mechanism

“…3C, top). Furthermore, because the expression of L-type calcium channels was reported in melanoma cells (20), we examined the effect of inhibition of these calcium channels on Epac-induced Ca 2+ signal. Neither verapamil nor nifedipine, L-type Ca 2+ channel blockers, inhibited Epac-induced Ca 2+ signal (Fig.…”