scholarly journals Ethanol, Zn2+ and insulin interact as progression factors to enhance DNA synthesis synergistically in the presence of Ca2+ and other cell cycle initiators in fibroblasts

2000 ◽  
Vol 346 (1) ◽  
pp. 241-247 ◽  
Author(s):  
Jin-Sheng HUANG ◽  
Qing-Bai SHE ◽  
Karan S. CRILLY ◽  
Zoltan KISS

In serum-starved NIH 3T3 fibroblasts, ethanol (30-80 mM) promoted the effects of insulin and insulin-like growth factor I (IGF-I) on DNA synthesis in a Zn2+-dependent manner. Ethanol and Zn2+ were most effective when added shortly before or after insulin, indicating that all these agents facilitated cell cycle progression. The synergistic effects of ethanol, Zn2+ and insulin (or IGF-I) on DNA synthesis required 1.1-2.3 mM Ca2+, which seemed to act as the cell cycle initiator. When serum-starved cells were pretreated for 2 h with other cell cycle initiators such as 10% (v/v) serum, 50 ng/ml platelet-derived growth factor or 2 ng/ml fibroblast growth factor, subsequent co-treatments with 60 mM ethanol, Zn2+ and insulin for an 18 h period again synergistically increased DNA synthesis. Of the various signal transducing events examined, ethanol stimulated cellular uptake of 45Ca and it enhanced the stimulatory effects of insulin on p70 S6 kinase activity in a Zn2+-dependent manner. In contrast, ethanol inhibited insulin-induced activating phosphorylation of p42/p44 mitogen-activated protein kinases; these inhibitory ethanol effects were prevented by Zn2+. The results show that, in NIH 3T3 fibroblasts, ethanol can promote cell cycle progression in the presence of a cell cycle initiator as well as Zn2+ and insulin (or IGF-I).

1993 ◽  
Vol 122 (2) ◽  
pp. 461-471 ◽  
Author(s):  
EK Han ◽  
TM Guadagno ◽  
SL Dalton ◽  
RK Assoian

We have examined cell cycle control of anchorage-independent growth in nontransformed fibroblasts. In previous studies using G0-synchronized NRK and NIH-3T3 cells, we showed that anchorage-independent growth is regulated by an attachment-dependent transition at G1/S that resembles the START control point in the cell cycle of Saccharomyces cerevisiae. In the studies reported here, we have synchronized NRK and NIH-3T3 fibroblasts immediately after this attachment-dependent transition to determine if other portions of the fibroblast cell cycle are similarly regulated by adhesion. Our results show that S-, G2-, and M-phase progression proceed in the absence of attachment. Thus, we conclude that the adhesion requirement for proliferation of these cells can be explained in terms of the single START-like transition. In related studies, we show that TGF-beta 1 overrides the attachment-dependent transition in NRK and AKR-2B fibroblasts (lines in which TGF-beta 1 induces anchorage-independent growth), but not in NIH-3T3 or Balb/c 3T3 fibroblasts (lines in which TGF-beta 1 fails to induce anchorage-independent growth). These results show that (a) adhesion and TGF-beta 1 can have similar effects in stimulating cell cycle progression from G1 to S and (b) the differential effects of TGF-beta 1 on anchorage-independent growth of various fibroblast lines are directly reflected in the differential effects of the growth factor at G1/S. Finally, we have randomly mutagenized NRK fibroblasts to generate mutant lines that have lost their attachment/TGF-beta 1 requirement for G1/S transit while retaining their normal mitogen requirements for proliferation. These clones, which readily proliferate in mitogen-supplemented soft agar, appear non-transformed in monolayer: they are well spread, nonrefractile, and contact inhibited. The existence of this new fibroblast phenotype demonstrates (a) that the growth factor and adhesion/TGF-beta 1 requirements for cell cycle progression are genetically separable, (b) that the two major control points in the fibroblast cell cycle (G0/G1 and G1/S) are regulated by distinct extracellular signals, and (c) that the genes regulating anchorage-independent growth need not be involved in regulating contact inhibition, focus formation, or growth factor dependence.


1999 ◽  
Vol 19 (7) ◽  
pp. 4623-4632 ◽  
Author(s):  
Masahiro Hitomi ◽  
Dennis W. Stacey

ABSTRACT Novel techniques were used to determine when in the cell cycle of proliferating NIH 3T3 cells cellular Ras and cyclin D1 are required. For comparison, in quiescent cells, all four of the inhibitors of cell cycle progression tested (anti-Ras, anti-cyclin D1, serum removal, and cycloheximide) became ineffective at essentially the same point in G1 phase, approximately 4 h prior to the beginning of DNA synthesis. To extend these studies to cycling cells, a time-lapse approach was used to determine the approximate cell cycle position of individual cells in an asynchronous culture at the time of inhibitor treatment and then to determine the effects of the inhibitor upon recipient cells. With this approach, anti-Ras antibody efficiently inhibited entry into S phase only when introduced into cells prior to the preceding mitosis, several hours before the beginning of S phase. Anti-cyclin D1, on the other hand, was an efficient inhibitor when introduced up until just before the initiation of DNA synthesis. Cycloheximide treatment, like anti-cyclin D1 microinjection, was inhibitory throughout G1 phase (which lasts a total of 4 to 5 h in these cells). Finally, serum removal blocked entry into S phase only during the first hour following mitosis. Kinetic analysis and a novel dual-labeling technique were used to confirm the differences in cell cycle requirements for Ras, cyclin D1, and cycloheximide. These studies demonstrate a fundamental difference in mitogenic signal transduction between quiescent and cycling NIH 3T3 cells and reveal a sequence of signaling events required for cell cycle progression in proliferating NIH 3T3 cells.


Author(s):  
Takashi Hashimoto ◽  
Maki Kobayashi ◽  
Kazuki Kanazawa

Objective: The effects of 6-MSITC on cell cycle progression were investigated in quiescent mouse epidermal JB6 cells. Background: 6-Methylsulfinylhexyl isothiocyanate (6-MSITC) derived from wasabi (Wasabia japonica) has been reported to prevent tumor development in vivo. Material and methods: Treatment with epidermal growth factor (EGF) to quiescent JB6 cells, which were serum-starved for 36 h, promoted cell cycle progression from the G0/G1 phase to the S phase. Effects of pretreatment with 6-MSITC on cell cycle progression were estimated by flowcytometry and real-time RT-PCR. Results: Pretreatment with 6-MSITC at 0.25-1.0 μg/ml prior to the growth stimulation with EGF significantly inhibited cell cycle progression. Pretreatment with 6-MSITC inhibited the gene expression of DNA synthesis-related proteins cyclin A2, dumbbell former 4, and proliferating cell nuclear antigen. Conclusion: These results showed that 6-MSITC inhibits cell cycle progression in quiescent cells, accompanied by the inhibition of gene expression of DNA synthesis proteins.


1993 ◽  
Vol 137 (1) ◽  
pp. 99-105 ◽  
Author(s):  
I. Kojima ◽  
H. Mogami ◽  
N. Kawamura ◽  
H. Shibata

ABSTRACT The present study was carried out to examine the effect of activin A on cell-cycle progression induced by insulin-like growth factor-I (IGF-I) in Balb/c 3T3 cells. When activin A was added together with IGF-I to competent cells primed with epidermal growth factor (primed competent cells), both [3H]thymidine incorporation and nuclear labelling induced by IGF-I were inhibited. The inhibition was concentration-dependent and the maximum inhibition was obtained with 1 nmol activin A/l. To ascertain the time in which activin A exerted its inhibitory action, we divided 12 h, the time required for primed competent cells to progress towards the S phase, into four periods and activin A was added during each of the four periods. It was effective when added during either the second (3 to 6 h) or the third period (6 to 9 h) but it did not affect cell-cycle progression when added during the first (0 to 3 h) or the last period (9 to 12 h). We then examined whether activin A affected intracellular events elicited by IGF-I. It did not affect either autophosphorylation of the IGF-I receptor or calcium entry induced by IGF-I. Likewise, it did not cause any change in the radioactivity of 1,2-diacylglycerol (DAG) in cells prelabelled with [3H]myristate while the increase in the mass of DAG induced by IGF-I was markedly reduced by activin A. The dose-response relationship for the activin A-mediated reduction of DAG mass correlated well with that for the activin A-mediated reduction of DNA synthesis. Activin A was effective in reducing DAG mass even when added 3 h after the addition of IGF-I. These results indicate that activin A attenuates cell-cycle progression in the middle of the G1 phase. The results also raise the possibility that reduction of DAG mass may account for the inhibitory effect of activin A on cell-cycle progression. Journal of Endocrinology (1993) 137, 99–105


Author(s):  
Chengyu Li ◽  
Zhaojun Liu ◽  
Jiaqi Zhou ◽  
Xueqin Meng ◽  
Shuo Liu ◽  
...  

Abstract As the follicle develops, the thickening of the granulosa compartment leads to progressively deficient supply of oxygen in granulosa cells (GCs) due to the growing distances from the follicular vessels. These conditions are believed to cause hypoxia in GCs during folliculogenesis. Upon hypoxic conditions, several types of mammalian cells have been reported to undergo cell cycle arrest. However, it remains unclear whether hypoxia exerts any impact on cell cycle progression of GCs. On the other hand, although the GCs may live in a hypoxic environment, their mitotic capability appears to be unaffected in growing follicles. It thus raises the question whether there are certain intraovarian factors that might overcome the inhibitory effects of hypoxia. The present study provides the first evidence suggesting that cobalt chloride (CoCl2)-mimicked hypoxia prevented G1-to-S cell cycle progression in porcine GCs. In addition, we demonstrated that the inhibitory effects of CoCl2 on GCs cell cycle are mediated through hypoxia-inducible factor-1 alpha/FOXO1/Cdkn1b pathway. Moreover, we identified insulin-like growth factor-I (IGF-I) as an intrafollicular factor required for cell cycle recovery by binding to IGF-I receptor in GCs suffering CoCl2 stimulation. Further investigations confirmed a role of IGF-I in preserving G1/S progression of CoCl2-treated GCs via activating the cyclin E/cyclin-dependent kinase2 complex through the phoshatidylinositol-3 kinase/protein kinase B (AKT)/FOXO1/Cdkn1b axis. Although the present findings were based on a hypoxia mimicking model by using CoCl2, our study might shed new light on the regulatory mechanism of GCs cell cycle upon hypoxic stimulation.


2008 ◽  
Vol 19 (1) ◽  
pp. 248-261 ◽  
Author(s):  
Peijun Liu ◽  
Jining Lu ◽  
Wellington V. Cardoso ◽  
Cyrus Vaziri

Secreted modular calcium-binding protein-2 (SMOC-2) is a recently-identified SPARC-related protein of unknown function. In mRNA profiling experiments we, found that SMOC-2 expression was elevated in quiescent (G0) mouse fibroblasts and repressed after mitogenic stimulation with serum. The G0-specific expression of SMOC-2 was similar to that of platelet-derived growth factor-β receptor (PDGFβR), a major mitogenic receptor. Therefore, we tested a possible role for SMOC-2 in growth factor-induced cell cycle progression. SMOC-2 overexpression augmented DNA synthesis induced by serum and fibroblast mitogens (including PDGF-BB and basic fibroblast growth factor). Conversely, SMOC-2 ablation by using small interfering RNA attenuated DNA synthesis in response to PDGF-BB and other growth factors. Mitogen-induced expression of cyclin D1 was attenuated in SMOC-2–ablated cells, and cyclin D1-overexpressing cells were resistant to inhibition of mitogenesis after SMOC-2 ablation. Therefore, cyclin D1 is limiting for G1 progression in SMOC-2–deficient cells. SMOC-2 ablation did not inhibit PDGF-induced PDGFβR autophosphorylation or PDGF-BB–dependent activation of mitogen-activated protein kinase and Akt kinases, suggesting that SMOC-2 is dispensable for growth factor receptor activation. However, integrin-linked kinase (ILK) activity was reduced in SMOC-2–ablated cells. Ectopic expression of hyperactive ILK corrected the defective mitogenic response of SMOC-2–deficient cells. Therefore, SMOC-2 contributes to cell cycle progression by maintaining ILK activity during G1. These results identify a novel role for SMOC-2 in cell cycle control.


1997 ◽  
Vol 17 (9) ◽  
pp. 5485-5498 ◽  
Author(s):  
M A Guthridge ◽  
P Bellosta ◽  
N Tavoloni ◽  
C Basilico

We have identified a novel type 2C serine-threonine phosphatase, FIN13, whose expression is induced by fibroblast growth factor 4 and serum in late G1 phase. The protein encoded by FIN13 cDNA includes N- and C-terminal domains with significant homologies to type 2C phosphatases, a domain homologous to collagen, and an acidic domain. FIN13 expression predominates in proliferating tissues. Bacterially expressed FIN13 and FIN13 expressed in mammalian cells exhibit serine-threonine phosphatase activity, which requires Mn2+ and is insensitive to inhibition by okadaic acid. FIN13 is localized in the nuclei of transiently transfected cells. Cotransfection of FIN13-expressing plasmids with a plasmid that expresses the neomycin resistance gene inhibits the growth of drug-resistant colonies in NIH 3T3, HeLa and Rat-1 cells. In transiently transfected cells, FIN13 inhibits DNA synthesis and results in the accumulation of cells in G1 and early S phases. Similarly, the induction of expression of FIN13 under the control of a tetracycline-regulated promoter in NIH 3T3 cells leads to growth inhibition, with accumulation of cells in G1 and early S phases. Thus, overexpression and/or unregulated expression of FIN13 inhibits cell cycle progression, indicating that the physiological role of this phosphatase may be that of regulating the orderly progression of cells through the mitotic cycle by dephosphorylating specific substrates which are important for cell proliferation.


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