Inhibition of Phosphatidylcholine-Specific Phospholipase C Interferes with Proliferation and Survival of Tumor Initiating Cells in Squamous Cell Carcinoma.

Abstract

PURPOSE:

The role of phosphatidylcholine-specific phospholipase C (PC-PLC), the enzyme involved in cell differentiation and proliferation, has not yet been explored in tumor initiating cells (TICs). We investigated PC-PLC expression and effects of PC-PLC inhibition in two adherent (AD) squamous carcinoma cell lines (A431 and CaSki), with different proliferative and stemness potential, and in TIC-enriched floating spheres (SPH) originated from them.

RESULTS:

Compared with immortalized non-tumoral keratinocytes (HaCaT) A431-AD cells showed 2.5-fold higher PC-PLC activity, nuclear localization of a 66-kDa PC-PLC isoform, but a similar distribution of the enzyme on plasma membrane and in cytoplasmic compartments. Compared with A431-AD, A431-SPH cells showed about 2.8-fold lower PC-PLC protein and activity levels, but similar nuclear content. Exposure of adherent cells to the PC-PLC inhibitor D609 (48h) induced a 50% reduction of cell proliferation at doses comprised between 33 and 50 μg/ml, without inducing any relevant cytotoxic effect (cell viability 95±5%). In A431-SPH and CaSki-SPH D609 induced both cytostatic and cytotoxic effects at about 20 to 30-fold lower doses (IC50 ranging between 1.2 and 1.6 μg/ml). Furthermore, D609 treatment of A431-AD and CaSki-AD cells affected the sphere-forming efficiency, which dropped in both cells, and induced down-modulation of stem-related markers mRNA levels (Oct4, Nestin, Nanog and ALDH1 in A431; Nestin and ALDH1 in CaSki cells).

CONCLUSIONS:

These data suggest that the inhibition of PC-PLC activity may represent a new therapeutic approach to selectively target the most aggressive and tumor promoting sub-population of floating spheres originated from squamous cancer cells possessing different proliferative and stemness potential.

• Authors: Serena Cecchetti, Ileana Bortolomai, Renata Ferri, Laura Mercurio, Silvana Canevari, Franca Podo, Silvia Miotti, Egidio Iorio
• Journal: PloS one (PLoS One) Vol. 10 Issue 9 Pg. e0136120 ( 2015) ISSN: 1932-6203 [Electronic] United States
• PMID: 26402860 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Bridged-Ring Compounds
• Norbornanes
• Thiocarbamates
• Thiones
• tricyclodecane-9-yl-xanthogenate
• ErbB Receptors
• Proto-Oncogene Proteins c-akt
• Extracellular Signal-Regulated MAP Kinases
• Type C Phospholipases
• phosphatidylcholine-specific phospholipase C

Topics

• Bridged-Ring Compounds (pharmacology)
• Carcinoma, Squamous Cell (metabolism)
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Cell Self Renewal
• Cell Survival (drug effects)
• ErbB Receptors (metabolism)
• Extracellular Signal-Regulated MAP Kinases (metabolism)
• Humans
• Keratinocytes (drug effects, metabolism)
• Neoplastic Stem Cells (drug effects, metabolism)
• Norbornanes
• Phosphorylation
• Protein Transport
• Proto-Oncogene Proteins c-akt (metabolism)
• Thiocarbamates
• Thiones (pharmacology)
• Type C Phospholipases (antagonists & inhibitors, metabolism)