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

• Published in: Cancer research (Chicago, Ill.) Vol. 59; no. 4; pp. 940 - 946
• Main Authors: SUN, X.-L, JAYARAM, H. N, GHAREHBAGHI, K, LI, Q.-J, XIANGLI XIAO, ANTONY, A. C
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 15-02-1999
• Subjects: Antimetabolites, Antineoplastic - pharmacology; Antineoplastic agents; Biological and medical sciences; Carrier Proteins - analysis; Carrier Proteins - genetics; Chemotherapy; Drug Resistance, Neoplasm; Female; Folate Receptors, GPI-Anchored; Gene Transfer Techniques; Humans; Medical sciences; Methotrexate - pharmacology; Pharmacology. Drug treatments; Receptors, Cell Surface; Thymidine - metabolism; Thymidine Kinase - metabolism; Uterine Cervical Neoplasms - drug therapy; Uterine Cervical Neoplasms - metabolism; Zidovudine - pharmacology; Antineoplastic agent; Carcinoma; Gene product; Cytotoxicity; Uterine cervix; Synergism; Folate; Enzymatic activity; Established cell line; Methotrexate; Pyrimidine nucleoside; Tumor cell; Biological receptor; Human; Thymidine kinase; Drug combination; Enzyme; Transferases; Malignant tumor; Gene expression; Thymidylate synthase; In vitro; Female genital diseases; Chemotherapy; Methyltransferases; Dideoxynucleoside; Zidovudine; Uterine cervix diseases
• ISSN: 0008-5472; 1538-7445

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.