Inhibition of phosphatidylcholine-specific phospholipase C interferes with proliferation and survival of tumor initiating cells in squamous cell carcinoma

Serena Cecchetti, Ileana Bortolomai, Renata Ferri, Laura Mercurio, Silvana Canevari, Franca Podo, Silvia Miotti, Egidio Iorio

Research output: Contribution to journalArticle

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.

Original languageEnglish
Article numbere0136120
JournalPLoS One
Volume10
Issue number9
DOIs
Publication statusPublished - Sep 24 2015

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Neoplastic Stem Cells
phospholipase C
squamous cell carcinoma
phosphatidylcholines
Tumors
Squamous Cell Carcinoma
Nestin
cells
cytotoxicity
cell proliferation
Cells
Cell Proliferation
Squamous Cell Neoplasms
neoplasm cells
phosphatidylcholine-specific phospholipase C
Epithelial Cells
keratinocytes
Cell proliferation
Cytostatic Agents
Enzymes

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

Inhibition of phosphatidylcholine-specific phospholipase C interferes with proliferation and survival of tumor initiating cells in squamous cell carcinoma. / Cecchetti, Serena; Bortolomai, Ileana; Ferri, Renata; Mercurio, Laura; Canevari, Silvana; Podo, Franca; Miotti, Silvia; Iorio, Egidio.

In: PLoS One, Vol. 10, No. 9, e0136120, 24.09.2015.

Research output: Contribution to journalArticle

Cecchetti, Serena ; Bortolomai, Ileana ; Ferri, Renata ; Mercurio, Laura ; Canevari, Silvana ; Podo, Franca ; Miotti, Silvia ; Iorio, Egidio. / Inhibition of phosphatidylcholine-specific phospholipase C interferes with proliferation and survival of tumor initiating cells in squamous cell carcinoma. In: PLoS One. 2015 ; Vol. 10, No. 9.
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AU - Cecchetti, Serena

AU - Bortolomai, Ileana

AU - Ferri, Renata

AU - Mercurio, Laura

AU - Canevari, Silvana

AU - Podo, Franca

AU - Miotti, Silvia

AU - Iorio, Egidio

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AB - 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.

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