Modulation of the cytotoxicity of 3'-azido-3'-deoxythymidine and methotrexate after transduction of folate receptor cDNA into human cervical carcinoma: Identification of a correlation between folate receptor expression and thymidine kinase activity

Xin Lai Sun, Hiremagalur N. Jayaram, Kamran Gharehbaghi, Qing Jun Li, Xiangli Xiao, Asok Antony

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Abstract

Cervical carcinoma is an AIDS-defining illness. The expression of folate receptors (FRs) in cervical carcinoma (HeLa-IU1) cells was modulated by stable transduction of FR cDNA encapsidated in recombinant adeno-associated virus-2 in the sense and antisense orientation (sense and antisense cells, respectively). Although sense cells proliferated slower than antisense or untransduced cells in vivo and in vitro in 2% (but not 10%) FCS, [methyl- 3H]thymidine incorporation into DNA was significantly increased in sense cells in 10% serum; therefore, the basis for this discrepancy was investigated. The activity of thymidine kinase (TK) was subsequently directly correlated with the extent of FR expression in single cell-derived clones of transduced cells. This elevated TK activity was not a result of recruitment of the salvage pathway based on the presence of adequate dTTP pools, normal thymidylate synthase (TS) activity, persistence of increased thymidine incorporation despite the exogenous provision of excess 5,10-methylene- tetrahydrofolate, and documentation of adequate folates in sense cells. The increase in TK activity conferred significant biological properties to sense cells (but not antisense or untransduced cells) as demonstrated by augmented phosphorylation of 3'-azido-3'-deoxythymidine (AZT) and concomitantly greater sensitivity to the cytotoxic effects of AZT. Conversely, sense cells were highly resistant to methotrexate, but this was reversed by the addition of AZT. The direct correlation of FR expression and TK activity indicates a previously unrecognized consequence of FR overexpression.

Original languageEnglish
Pages (from-to)940-946
Number of pages7
JournalCancer Research
Volume59
Issue number4
StatePublished - Feb 15 1999

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Thymidine Kinase
Zidovudine
Folic Acid
Methotrexate
Complementary DNA
Carcinoma
Thymidine
Thymidylate Synthase
Dependovirus
HeLa Cells
Documentation
Acquired Immunodeficiency Syndrome
Clone Cells
Phosphorylation
DNA

ASJC Scopus subject areas

  • Cancer Research
  • Oncology

Cite this

Modulation of the cytotoxicity of 3'-azido-3'-deoxythymidine and methotrexate after transduction of folate receptor cDNA into human cervical carcinoma : Identification of a correlation between folate receptor expression and thymidine kinase activity. / Sun, Xin Lai; Jayaram, Hiremagalur N.; Gharehbaghi, Kamran; Li, Qing Jun; Xiao, Xiangli; Antony, Asok.

In: Cancer Research, Vol. 59, No. 4, 15.02.1999, p. 940-946.

Research output: Contribution to journalArticle

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abstract = "Cervical carcinoma is an AIDS-defining illness. The expression of folate receptors (FRs) in cervical carcinoma (HeLa-IU1) cells was modulated by stable transduction of FR cDNA encapsidated in recombinant adeno-associated virus-2 in the sense and antisense orientation (sense and antisense cells, respectively). Although sense cells proliferated slower than antisense or untransduced cells in vivo and in vitro in 2{\%} (but not 10{\%}) FCS, [methyl- 3H]thymidine incorporation into DNA was significantly increased in sense cells in 10{\%} serum; therefore, the basis for this discrepancy was investigated. The activity of thymidine kinase (TK) was subsequently directly correlated with the extent of FR expression in single cell-derived clones of transduced cells. This elevated TK activity was not a result of recruitment of the salvage pathway based on the presence of adequate dTTP pools, normal thymidylate synthase (TS) activity, persistence of increased thymidine incorporation despite the exogenous provision of excess 5,10-methylene- tetrahydrofolate, and documentation of adequate folates in sense cells. The increase in TK activity conferred significant biological properties to sense cells (but not antisense or untransduced cells) as demonstrated by augmented phosphorylation of 3'-azido-3'-deoxythymidine (AZT) and concomitantly greater sensitivity to the cytotoxic effects of AZT. Conversely, sense cells were highly resistant to methotrexate, but this was reversed by the addition of AZT. The direct correlation of FR expression and TK activity indicates a previously unrecognized consequence of FR overexpression.",
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