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 (ΔNErbB2) common in breast cancer impacts on the Na+/H+-exchanger NHE1 and the Na+,HCO3--cotransporter NBCn1 in MCF-7 human breast cancer cells and address the roles of these transporters in chemotherapy resistance. Upon ΔNErbB2 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 pHi recovery after acid loading increased by 50% upon ΔNErbB2 expression. Knockdown and pharmacological inhibition confirmed the involvement of both NHE1 and NBCn1 in acid extrusion. NHE1 inhibition or knockdown sensitized ΔNErbB2-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 (ΔNErbB2) common in breast cancer impacts on the Na+/H+-exchanger NHE1 and the Na+,HCO3--cotransporter NBCn1 in MCF-7 human breast cancer cells and address the roles of these transporters in chemotherapy resistance. Upon ΔNErbB2 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 pHi recovery after acid loading increased by 50% upon ΔNErbB2 expression. Knockdown and pharmacological inhibition confirmed the involvement of both NHE1 and NBCn1 in acid extrusion. NHE1 inhibition or knockdown sensitized ΔNErbB2-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
SN - 0014-4827
VL - 316
SP - 2538
EP - 2553
JO - Experimental Cell Research
JF - Experimental Cell Research
IS - 15
ER -
