TY - JOUR

T1 - NBCn1 and NHE1 expression and activity in DeltaNErbB2 receptor-expressing MCF-7 breast cancer cells: contributions to pHi regulation and chemotherapy resistance

AU - Lauritzen, G

AU - Jensen, M B F

AU - Bødtkjer, Ebbe

AU - Dybboe, R

AU - Aalkjær, Christian

AU - Nylandsted, J

AU - Pedersen, Stine Helene Falsig

N1 - Copyright 2010 Elsevier Inc. All rights reserved.

PY - 2010/9/10

Y1 - 2010/9/10

N2 - Altered pH-regulatory ion transport is characteristic of many cancers; however, the mechanisms and consequences are poorly understood. Here, we investigate how a truncated, constitutively active ErbB2 receptor (DeltaNErbB2) common in breast cancer impacts on the Na(+)/H(+)-exchanger NHE1 and the Na(+),HCO(3)(-)-cotransporter NBCn1 in MCF-7 human breast cancer cells and address the roles of these transporters in chemotherapy resistance. Upon DeltaNErbB2 expression, mRNA and protein levels of NBCn1, yet not of NHE1, increased several-fold, and the localization of both transporters was altered paralleling extensive morphological changes. The rate of pH(i) recovery after acid loading increased by 50% upon DeltaNErbB2 expression. Knockdown and pharmacological inhibition confirmed the involvement of both NHE1 and NBCn1 in acid extrusion. NHE1 inhibition or knockdown sensitized DeltaNErbB2-expressing cells to cisplatin-induced programmed cell death (PCD) in a caspase-, cathepsin-, and reactive oxygen species-dependent manner. NHE1 inhibition augmented cisplatin-induced caspase activity and lysosomal membrane permeability followed by cysteine cathepsin release. In contrast, NBCn1 inhibition attenuated cathepsin release and had no net effect on viability. These findings warrant studies of NHE1 as a potential target in breast cancer and demonstrate that in spite of their similar transport functions, NHE1 and NBCn1 serve different functions in MCF-7 cells.

AB - Altered pH-regulatory ion transport is characteristic of many cancers; however, the mechanisms and consequences are poorly understood. Here, we investigate how a truncated, constitutively active ErbB2 receptor (DeltaNErbB2) common in breast cancer impacts on the Na(+)/H(+)-exchanger NHE1 and the Na(+),HCO(3)(-)-cotransporter NBCn1 in MCF-7 human breast cancer cells and address the roles of these transporters in chemotherapy resistance. Upon DeltaNErbB2 expression, mRNA and protein levels of NBCn1, yet not of NHE1, increased several-fold, and the localization of both transporters was altered paralleling extensive morphological changes. The rate of pH(i) recovery after acid loading increased by 50% upon DeltaNErbB2 expression. Knockdown and pharmacological inhibition confirmed the involvement of both NHE1 and NBCn1 in acid extrusion. NHE1 inhibition or knockdown sensitized DeltaNErbB2-expressing cells to cisplatin-induced programmed cell death (PCD) in a caspase-, cathepsin-, and reactive oxygen species-dependent manner. NHE1 inhibition augmented cisplatin-induced caspase activity and lysosomal membrane permeability followed by cysteine cathepsin release. In contrast, NBCn1 inhibition attenuated cathepsin release and had no net effect on viability. These findings warrant studies of NHE1 as a potential target in breast cancer and demonstrate that in spite of their similar transport functions, NHE1 and NBCn1 serve different functions in MCF-7 cells.

KW - Acid-Base Equilibrium

KW - Antineoplastic Agents

KW - Biological Transport

KW - Breast Neoplasms

KW - Cathepsins

KW - Cation Transport Proteins

KW - Cell Line, Tumor

KW - Drug Resistance, Neoplasm

KW - Female

KW - Gene Expression Regulation, Neoplastic

KW - Humans

KW - Hydrogen-Ion Concentration

KW - Intracellular Membranes

KW - Mutant Proteins

KW - Protein Structure, Tertiary

KW - RNA, Small Interfering

KW - Receptor, erbB-2

KW - Sodium-Bicarbonate Symporters

KW - Sodium-Hydrogen Antiporter

U2 - 10.1016/j.yexcr.2010.06.005

DO - 10.1016/j.yexcr.2010.06.005

M3 - Journal article

C2 - 20542029

VL - 316

SP - 2538

EP - 2553

JO - Experimental Cell Research

JF - Experimental Cell Research

SN - 0014-4827

IS - 15

ER -