Knockdown of STAT3 targets a subpopulation of invasive melanoma stem-like cells

Area of Science:

• Oncology
• Cancer Biology
• Molecular Biology

Background:

• Signal transducer and activator of transcription 3 (STAT3) is constitutively activated in various cancers, including melanoma.
• Active STAT3 promotes tumor growth, immune suppression, and cancer stem cell (CSC) self-renewal.
• STAT3's role in melanoma CSCs remains to be fully elucidated.

Purpose of the Study:

• To investigate the expression and function of active STAT3 in melanoma CSCs.
• To determine if STAT3 signaling influences melanoma CSC maintenance and associated invasive properties.

Main Methods:

• Analysis of phosphorylated STAT3 (Y705) levels in melanoma CSC sphere cultures.
• STAT3 knockdown experiments to assess proliferation and sphere-forming capacity.
• Flow cytometry sorting of CSC subpopulations and analysis of STAT3 expression.
• Assessment of focal adhesion kinase (FAK), AKT, and SERPINA3 expression and their correlation with invasion.

Main Results:

• Elevated levels of phosphorylated STAT3 (Y705) were observed in melanoma CSC sphere cultures.
• STAT3 knockdown reduced sphere-forming capacity in human melanoma cell lines but not basal proliferation.
• Active STAT3 was enriched in rhodamine 123 negative CSC subpopulations.
• Upregulation of FAK, AKT, and SERPINA3 pathways was noted in melanoma CSCs, correlating with increased invasion.

Conclusions:

• STAT3 is activated in melanoma CSCs and plays a crucial role in their maintenance.
• Targeting STAT3 may represent a therapeutic strategy to inhibit melanoma progression and recurrence.
• STAT3 signaling in melanoma CSCs is linked to pathways regulating cell invasion.