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Hypersensitivity of NIH3T3 cells transformed by H‐ RAS gene to DNA‐topoisomerase‐I inhibitors
Author(s) -
Ohira Tatsuo,
Nishio Kazuto,
Kanzawa Fumihiko,
Ishida Tomoyuki,
Ohe Yuichiro,
Arioka Hitoshi,
Funayama Yasunori,
Ogasawara Hayato,
Kato Harubumi,
Saijo Nagahiro
Publication year - 1996
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/(sici)1097-0215(19960904)67:5<702::aid-ijc19>3.0.co;2-6
Subject(s) - biology , camptothecin , cell culture , microbiology and biotechnology , topoisomerase , growth inhibition , oncogene , dna , gene product , cell growth , gene , cell cycle , biochemistry , gene expression , genetics
We examined the effects of the introduction of H‐ ras oncogene into murine cell line NIH3T3 on growth inhibition by topoisomerase‐I (topo‐I) inhibitors. The H‐ ras ‐transformed cells (pT22‐3) showed approximately 12‐fold increased sensitivity to a novel topo‐I inhibitor, NB‐506 [6‐ N ‐formylamino‐12, 13‐dihydro‐I, II‐dihydroxy‐13‐(β‐ D ‐glucopyranosyl)‐5 H ‐indolo(2,3‐ a )pyrrolo(3,4‐ c ) carbazole‐5,7(6 H )‐dione], compared with the parental NIH3T3 cells. pT22‐3 also showed increased sensitivity to other topo‐I inhibitors such as camptothecin (approx. 3.0‐fold) and CPT‐II (irinotecan, approx. 3.0‐fold). Transformation of NIH3T3 by another oncogene (erb82) did not affect their sensitivity to these topo‐I inhibitors. pT22‐3 had approximately 32‐fold higher topo‐I activity than NIH3T3, but the same topo‐I content. In a cell‐free system, topo‐I activity was increased 2‐fold by addition of the H‐ ras protein precipitated from pT22‐3 cells. Topo I in the nuclear extract of pT22‐3 was eluted easily by low concentrations of NaCl compared with that of NIH3T3, suggesting a qualitative change in pT22‐3 topo I. Increased phosphorylation of topo I was observed in pT22‐3. Furthermore, NB‐506 decreased the amount of the GTP‐bound form of the H‐ras product in pT22‐3 cells. These results suggest that the high growth‐inhibitory effect of a topo‐I inhibitor, NB‐506, on H‐ ras ‐transformed NIH3T3 cells is due to the H‐ ras ‐mediated signal‐transduction pathway. © 1996 Wiley‐Liss, Inc.