The SK3/K(Ca)2.3 potassium channel is a new cellular target for edelfosine.
OBJECTIVE
The 1-O-octadecyl-2-O-methyl-sn-glycero-3-phosphocholine (edelfosine) is an ether-linked phospholipid with promising anti-cancer properties but some side effects that preclude its full clinical therapeutic exploitation. We hypothesized that this lipid could interact with plasma membrane ion channels and modulate their function.


METHODS
Using cell migration-proliferation assays, patch clamp, spectrofluorimetry and ¹²⁵I-Apamin binding experiments, we studied the effects of edelfosine on the migration of breast cancer MDA-MB-435s cells, mediated by the small conductance Ca²(+) -activated K(+) channel, SK3/K(Ca)2.3.


RESULTS
Edelfosine (1 µM) caused plasma membrane depolarization by substantially inhibiting activity of SK3/K(Ca)2.3 channels, which we had previously demonstrated to play an important role in cancer cell migration. Edelfosine did not inhibit ¹²⁵I-Apamin binding to this SK(Ca) channel; rather, it reduced the calcium sensitivity of SK3/K(Ca)2.3 channel and dramatically decreased intracellular Ca²(+) concentration, probably by insertion in the plasma membrane, as suggested by proteinase K experiments. Edelfosine reduced cell migration to the same extent as known SK(Ca) channel blockers. In contrast, K+ channel openers prevented edelfosine-induced anti-migratory effects. SK3 protein knockdown decreased cell migration and totally abolished the effect of edelfosine on MDA-MB-435s cell migration. In contrast, transient expression of SK3/K(Ca)2.3 protein in a SK3/K(Ca)2.3-deficient cell line increased cell migration and made these cells responsive to edelfosine.


CONCLUSIONS
Our data clearly establish edelfosine as an inhibitor of cancer cell migration by acting on SK3/K(Ca)2.3 channels and provide insights into the future development of a new class of migration-targeted, anti-cancer agents.
Inserm, U, Université François Rabelais, Tours, France.
M
M
Potier
A
A
Chantome
V
V
Joulin
A
A
Girault
S
S
Roger
P
P
Besson
M-L
ML
Jourdan
J-Y
JY
LeGuennec
P
P
Bougnoux
C
C
Vandier
D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology*; D001030:Apamin / Q000378:metabolism; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects; D054443:Cell Migration Assays; D002465:Cell Movement / Q000187:drug effects*; D019286:Endopeptidase K / Q000378:metabolism; D004847:Epithelial Cells; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D058990:Molecular Targeted Therapy; D010742:Phospholipid Ethers / Q000378:metabolism / Q000494:pharmacology*; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*
D000970:Antineoplastic Agents; C406328:KCNN3 protein, human; D010742:Phospholipid Ethers; D051640:Small-Conductance Calcium-Activated Potassium Channels; C026659:edelfosine; D001030:Apamin; D019286:Endopeptidase K; D002118:Calcium