Expression of Bcl-XS alters cytokinetics and decreases clonogenic survival in K12 rat colon carcinoma cells.
bcl-XS, a member of the bcl-2 family, has been shown to induce and/or sensitize some cells to undergo programmed cell death, and to negate the anti-apoptotic activity of bcl-XL and bcl-2 by mechanisms which are still uncertain. To help understand these mechanisms we have established stable derivatives of the K12 rat colon carcinoma cell line that express bcl-XS in a tetracycline-regulated manner, using an autoregulatory retroviral cassette. When bcl-XS expression is induced, we observe two phenotypic responses. A small fraction of cells appear to undergo spontaneous apoptosis while the majority of cells undergo a form of cytostasis. In the latter case, the cells stop dividing (or divide a limited number of times at a retarded rate) and swell to many times their original size. These cells can take on a ghostlike appearance and subsequently detach from the culture plates and die or they may remain intact in a hindered state of proliferation. Doubling times were calculated to be 31.4 h in the presence of tetracycline and 50.4 h without tetracycline, bcl-XS expression also causes dramatic alterations in the cell cycle distribution of K12 cells manifesting as a substantial decrease (approximately 50%) in the fraction of S phase cells with a concomitant increase in the G1 population. Continuous expression of bcl-XS, at levels approximately equal to that of bcl-XL, decreased the viability of K12 cells as demonstrated by a log decline in clonogenic survival. This decrease occurred without considerable apoptosis or a compensatory increase in the level of bcl-XL. None of these phenotypes were present in control cells expressing beta-galactosidase in a similar retroviral cassette. These observations demonstrate that bcl-XS can have substantial cytokinetic effects under circumstances that produce relatively little apoptosis.
Fridman
J S
JS
Department of Pharmacology, University of Michigan Medical School, Ann Arbor 48109, USA.
Rehemtulla
A
A
Hofmann
A
A
Blau
H M
HM
Maybaum
J
J
D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival; D003110:Colonic Neoplasms; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects; D007763:Lac Operon; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis* / Q000235:genetics; D051381:Rats; D013752:Tetracycline / Q000494:pharmacology; D013997:Time Factors; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein
C494813:Bcl2l1 protein, rat; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D013752:Tetracycline