5-FdUrd-araC heterodinucleoside re-establishes sensitivity in 5-FdUrd- and AraC-resistant MCF-7 breast cancer cells overexpressing ErbB2.
ErbB2 overexpressing breast tumors have a poor prognosis and a high risk to develop chemoresistance to therapeutic treatment. "Chemoresistance" is a response of cells to toxic stress, and, although it is a common phenomenon, it is still poorly defined. However, a detailed understanding is required to target desensitized pathways and mechanisms for successful reactivation as part of a tailored therapy. To gain insight, which malfunctions contribute to chemoresistance, two mechanisms relevant for tissue homeostasis, the regulation of the cell cycle and of apoptosis, were investigated. Maternal MCF-7- and ErbB2-overexpressing MCF-7(erbB2) breast cancer cells were long term pretreated with 2'-deoxy-5-fluorodeoxyuridine (5-FdUrd) or 1-beta-d-arabinofuranosylcytosine (AraC) and the acquisition of drug-insensitivity was analyzed. A phosphate-conjugated heterodinucleoside consisting of one 5-FdUrd- and one AraC-moiety (5-fluoro-2'-desoxyuridylyl-(3'-->5')-Arabinocytidine) was utilized as a tool to assess the type of acquired resistances. ErbB2-overexpression disrupted proper cell cycle regulation and furthermore facilitated the development of an apoptosis-refractory phenotype upon exposure to 5-FdUrd. Experiments with dimer 5-FdUrd-araC in ErbB2-overexpressing MCF-7(erbB2) cells, and also with nucleoside 5-FdUrd in maternal MCF-7 cells, evidenced that the phenotypes of resistance to cell cycle inhibition and to apoptosis induction were differently affected. The expression profile of cyclin D1 (but not that of p53, p21, or p27) correlated with the proliferative phenotypes and nuclear accumulation of apoptosis inducing factor (but not activation of caspase 7) with apoptotic phenotypes. Dimer 5-FdUrd-araC overrode acquired chemoresistances, whereas combined application of 5-FdUrd and AraC exhibited significantly less activity. Dimer 5-FdUrd-araC remained active in MCF-7 clones most likely by circumventing the prerequisite of first-step phosphorylation. The acquisition of chemoresistance encompassed the affection of apoptosis- and cell-cycle regulation to, respectively, different extents. Thus, drug-induced cell cycle arrest and apoptosis induction are independent of each other.
Strasser
Stephen
S
Institute of Clinical Pathology, Medical University of Vienna, A-1090 Vienna, Austria.
Maier
Susanne
S
Leisser
Christina
C
Saiko
Philipp
P
Madlener
Sibylle
S
Bader
Yvonne
Y
Bernhaus
Astrid
A
Gueorguieva
Marieta
M
Richter
Susanne
S
Mader
Robert M
RM
Wesierska-Gadek
Jozefa
J
Schott
Herbert
H
Szekeres
Thomas
T
Fritzer-Szekeres
Monika
M
Krupitza
Georg
G
D000964:Antimetabolites, Antineoplastic / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D019938:Cyclin D1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D003561:Cytarabine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D019281:Dimerization; D019008:Drug Resistance, Neoplasm; D005260:Female; D005467:Floxuridine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D000964:Antimetabolites, Antineoplastic; D053179:Caspase 7; D019938:Cyclin D1; D003561:Cytarabine; D005467:Floxuridine; D018719:Erb-b2 Receptor Tyrosine Kinases; C517379:5-fluoro-2'-deoxyuridylyl-(3'-5')-arabinocytidine