Sphingolipids regulate diverse cellular processes including adhesion, migration, proliferation, senescence, death, and differentiation. Dysregulation of sphingolipid metabolism or signaling is commonly found in malignant cells and can support tumor growth, immune suppression, and drug resistance. Fingolimod is a synthetic analogue of sphingosine used clinically for relapsing-remitting multiple sclerosis and has been explored as an antineoplastic agent because it can modulate sphingolipid-related metabolic and signaling pathways to inhibit cell-cycle progression or promote apoptosis.
The report summarized here evaluated fingolimod in acute myeloid leukemia (AML) models to assess whether it can overcome or act independently of common mechanisms of chemoresistance.
The experiments employed two human AML cell lines, MOLM-13 and SKM-1, together with sublines selected or established to display a multidrug-resistant phenotype mediated by overexpression of P-glycoprotein (the ATP-binding cassette transporter associated with drug efflux and resistance).
Using both drug-sensitive parental lines and their P-glycoprotein–overexpressing derivatives allowed the investigators to compare fingolimod responses across models that differ in a clinically relevant resistance mechanism.
Fingolimod was shown to be a potent inducer of apoptosis-like cell death in both drug-sensitive and P-glycoprotein–overexpressing AML cells. The authors report that the maximal cytotoxic effect occurred at 8 hours after exposure. This rapid onset indicates fingolimod can trigger acute death pathways in these leukemia cells irrespective of P-glycoprotein status.
Apoptosis-like death following fingolimod treatment was accompanied by a decrease in mitochondrial membrane potential, a hallmark of mitochondrial involvement in cell death pathways. In parallel, fingolimod exposure produced generation of reactive oxygen species (ROS), indicating induction of oxidative stress. These findings point to mitochondrial dysfunction and oxidative damage as central features of the fingolimod-induced cytotoxic phenotype in AML models.
In addition to mitochondrial depolarization and ROS, fingolimod-treated AML cells exhibited an increase in intracellular calcium concentration. The drug also increased the activity of stress-activated mitogen-activated protein kinases JNK and p38. Activation of these kinases is consistent with engagement of cellular stress-response signaling that can promote apoptosis-like outcomes.
Taken together, the biochemical pattern reported — mitochondrial depolarization, ROS production, Ca2+ rise, and JNK/p38 activation — reflects a coordinated cytotoxic stress response linked to the observed cell death.
When applied at sublethal concentrations, fingolimod induced accumulation of AML cells in the G0/G1 phase of the cell cycle. However, this cell-cycle arrest was not accompanied by evidence of leukemia cell differentiation. Thus, fingolimod can exert cytostatic effects at lower exposures while failing to trigger maturation of the malignant cells under the conditions reported.
Fingolimod treatment led to a decrease in the expression of P-glycoprotein at the mRNA level. Despite this reduction in transcript expression, the same concentration of fingolimod produced virtually no change in P-glycoprotein functional activity. In other words, fingolimod reduced P-glycoprotein mRNA but did not measurably impair the activity of the efflux transporter at the tested concentration.
This distinction between expression and activity highlights that fingolimod’s cytotoxicity in these models does not rely on immediate inhibition of P-glycoprotein function.
The presented data support that fingolimod exerts direct cytotoxic and stress-signaling effects on AML cells, including those with a P-glycoprotein–driven multidrug-resistant phenotype. The rapid induction of apoptosis-like cell death (maximal at 8 hours) together with mitochondrial depolarization, ROS generation, intracellular calcium elevation, and activation of JNK and p38 suggest multiple converging mechanisms of cellular damage.
Although fingolimod decreased P-glycoprotein mRNA, its lack of effect on transporter activity at the same concentration indicates that the drug’s antileukemic actions in these experiments were not dependent on reversing P-glycoprotein–mediated drug efflux.
The source abstract does not report detailed dose ranges, specific assay conditions, quantitative effect sizes, or in vivo data. Those details were not provided in the abstract and would require consultation of the full text for experimental parameters, statistical analyses, and potential translational considerations.
Overall, these findings position fingolimod as a compound capable of triggering cytotoxic stress and apoptosis-like death in AML cell models regardless of P-glycoprotein–mediated resistance, with distinct biochemical signatures that merit further mechanistic and translational study.