Phospholipase C δ-4 overexpression upregulates ErbB1/2 expression, Erk signaling pathway, and proliferation in MCF-7 cells

Leung, Tompkins Chris, Brewer Jim, Ball Alexey, Coon Mike, Morris Valerie, Waggoner David, Singer

Description

The expression of the rodent phosphoinositide-specific phospholipase C δ-4 (PLCδ4) has been found to be elevated upon mitogenic stimulation and expression analysis have linked the upregulation of PLCδ4 expression with rapid proliferation in certain rat transformed cell lines. The human homologue of PLCδ4 has not been extensively characterized. Accordingly, we investigate the effects of overexpression of human PLCδ4 on cell signaling and proliferation in this study. Results The cDNA for human PLCδ4 has been isolated and expressed ectopically in breast cancer MCF-7 cells. Overexpression of PLCδ4 selectively activates protein kinase C-φ and upregulates the expression of epidermal growth factor receptors EGFR/erbB1 and HER2/erbB2, leading to constitutive activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) pathway in MCF-7 cells. MCF-7 cells stably expressing PLCδ4 demonstrates several phenotypes of transformation, such as rapid proliferation in low serum, formation of colonies in soft agar, and capacity to form densely packed spheroids in low-attachment plates. The growth signaling responses induced by PLCδ4 are not reversible by siRNA. Conclusion Overexpression or dysregulated expression of PLCδ4 may initiate oncogenesis in certain tissues through upregulation of ErbB expression and activation of ERK pathway. Since the growth responses induced by PLCδ4 are not reversible, PLCδ4 itself is not a suitable drug target, but enzymes in pathways activated by PLCδ4 are potential therapeutic targets for oncogenic intervention.

Informations

• Publié par: biomed
• Publié le: 01 janvier 2004
• Nombre de lectures: 403
• Langue: English
• Poids de l'ouvrage: 2 Mo

Extrait

Pga e 1fo1  ( 5 apegum nr bet nor foaticnoitrup esops)

Molecular Cancer

Published: 13 May 2004 Received: 31 December 2003 Molecular Cancer 2004, 3 :15 Accepted: 13 May 2004 This article is available from: http:/ /www.molecular-cancer.com/content/3/1/15 © 2004 Leung et al; licensee BioMed Central Lt d. This is an Open Access article: verbat im copying and redistribution of this ar ticle are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL.

Research Open Access Phospholipase C δ -4 overexpression upregulates ErbB1/2 expression, Erk signaling pathway, and proliferation in MCF-7 cells David W Leung*, Chris Tompkins, Jim Brewer, Alexey Ball, Mike Coon, Valerie Morris, David Waggoner and Jack W Singer

Address: Cell Therapeutics, Inc., 201 El liott Ave., W., Seattle, WA 98119, U.S.A Email: David W Leung* - [e-mail]; Chris Tompkins - ctompk [e-mail]; Jim B rewer - [e-mail]; Alexey Ball - [e-mail]; Mike Coon - mcoon@ctisea ttle.com; Valerie Morri s - [e-mail]; David Waggoner - [e-mail]; Jack W Singer - [e-mail] * Corresponding author

Abstract Background: The expression of the rodent phospho inositide-specific phospholipase C δ -4 (PLC δ 4) has been found to be elevated upon mitoge nic stimulation and expression analysis have linked the upregulation of PLC δ 4 expression with rapid proliferat ion in certain rat transformed cell lines. The human homologue of PLC δ 4 has not been extensively ch aracterized. Accordingly, we investigate the effects of overexpression of human PLC δ 4 on cell signaling and proliferation in this study. Results: The cDNA for human PLC δ 4 has been isolated and expresse d ectopically in breast cancer MCF-7 cells. Overexpression of PLC δ 4 selectively activates protein kinase C-φ and upregulates the expression of epidermal grow th factor receptors EGFR/erbB1 and HER2/erbB2, leading to constitutive activation of extrac ellular signal-regulated kinases 1 and 2 (ERK1/2) pathway in MCF- 7 cells. MCF-7 cells stably expressing PLC δ 4 demonstrates several pheno types of transformation, such as rapid proliferation in low serum, formatio n of colonies in soft agar, and capacity to form densely packed spheroids in low-attachment pl ates. The growth signaling responses induced by PLC δ 4 are not reversible by siRNA. Conclusion: Overexpression or dysregul ated expression of PLC δ 4 may initiate oncogenesis in certain tissues through upregulatio n of ErbB expression and activa tion of ERK pathway. Since the growth responses induced by PLC δ 4 are not reversible, PLC δ 4 itself is not a suitable drug target, but enzymes in pathways activated by PLC δ 4 are potential therapeuti c targets for oncogenic intervention.

Bio Med  Central

Background cylglycerol (DAG), which cause the increase of intracellu- Phosphoinositide-specific phospholipase C (PI-PLC) lar calcium concentration and the activation of protein plays a role in the inositol phospholipid signaling by kinase C (PKC), respectively [1-3]. In addition to hydro- hydrolyzing phosphatidylinositol-4,5-bisphosphate lyzing PIP 2 , PI-PLC can also utilize phosphatidylinositol (PIP 2 ). This reaction produces two intracellular second (PI) or PI-4-phosphate as substrates. messengers, inositol 1,4,5-trisphosphate (IP 3 ) and dia-