The PI3K/AKT signaling pathway controls the quiescence of the low-Rhodamine123-retention cell compartment enriched for melanoma stem cell activity.
Melanoma is one of the most aggressive and extremely resistant to conventional therapies neoplasms. Recently, cellular resistance was linked to the cancer stem cell phenotype, still controversial and not well-defined. In this study, we used a Rhodamine 123 (Rh123) exclusion assay to functionally identify stem-like cells in metastatic human melanomas and melanoma cell lines. We demonstrate that a small subset of Rh123-low-retention (Rh123(low)) cells is enriched for stem cell-like activities, including the ability to self-renew and produce nonstem Rh123(high) progeny and to form melanospheres, recapitulating the phenotypic profile of the parental tumor. Rh123(low) cells are relatively quiescent and chemoresistant. At the molecular level, we show that melanoma Rh123(low) cells overexpress HIF1α, pluripotency factor OCT4, and the ABCB5 marker of melanoma stem cells and downregulate the expression of Cyclin D1 and CDK4. Interestingly, a short treatment with LY294002, an inhibitor of the PI3K/AKT pathway, specifically reverts a subset of Rh123(high) cells to the Rh123(low) phenotype, whereas treatment with inhibitors of mammalian target of rapamycin, phosphatase and tensin homolog or mitogen-activated protein kinase signaling does not. This phenotypic switching was associated with reduced levels of the HIF1α transcript and an increase in the level of phosphorylated nuclear FOXO3a preferentially in Rh123(low) cells. Moreover, the Rh123(low) cells became less quiescent and displayed a significant increase in their melanosphere-forming ability. All the above indicates that the Rh123(low) melanoma stem cell pool is composed of cycling and quiescent cells and that the PI3K/AKT signaling while maintaining the quiescence of Rh123(low) G0 cells promotes the exit of cycling cells from the stem cell compartment.
Inserm U837 Jean-Pierre Aubert Research Center, Institut pour la Recherche sur le Cancer de Lille (IRCL), 1 Place de Verdun, 59045 Lille, France.
Yasmine
Y
Touil
Thomas
T
Zuliani
Isabelle
I
Wolowczuk
Klaudia
K
Kuranda
Jirina
J
Prochazkova
Joris
J
Andrieux
Helene
H
Le Roy
Laurent
L
Mortier
Jerome
J
Vandomme
Nathalie
N
Jouy
Bernadette
B
Masselot
Pascaline
P
Ségard
Bruno
B
Quesnel
Pierre
P
Formstecher
Renata
R
Polakowska
D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002867:Chromones / Q000494:pharmacology; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D007150:Immunohistochemistry; D008545:Melanoma / Q000378:metabolism*; D009025:Morpholines / Q000494:pharmacology; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000378:metabolism*; D050814:Octamer Transcription Factor-3 / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020112:Rhodamine 123 / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D014407:Tumor Cells, Cultured
D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002867:Chromones; D019938:Cyclin D1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009025:Morpholines; D050814:Octamer Transcription Factor-3; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D020112:Rhodamine 123; C480744:ABCB5 protein, human; C497442:HIF1A protein, human; C494173:POU5F1 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one