Inhibition of cell growth by cellular differentiation into adipocyte-like cells in dexamethasone sensitive cancer cell lines

Abstract

The stress responses in human body lead to secretion of cortisol hormone. The present study investigated the cellular responses on cell growth and cellular differentiation into adipocytes by exposure of synthetic stress hormone, dexamethasone (DEX) in various human cancer and normal cells. After prolonged exposure of cells with 1 μg/ml DEX for 2 weeks, population doubling time (PDT) was significantly (P < .05) increased by inhibited cell growth in A-549 and MCF-7 cancer cells, and was unchanged in MDA-MB-231 cancer cells, normal MRC-5 fibroblasts, umbilical cord matrix-derived mesenchymal stem cells (UCMSCs) and dental papilla tissue-derived mesenchymal stem cells (DSCs). Whereas, PDT was significantly (P < .05) decreased in U87-MG cancer cells by increased cell growth. Glucose uptake was significantly (P < .05) increased in all the cancer cell lines compared to that in normal cell lines. Further, adiposome-like vesicles were noted in A-549 and MCF-7 cancer cells indicating retarded cell growth by DEX treatment, and the vesicles were stained with Oil-Red O solution. Further, the expression of adipocyte-specific genes such as glucose transporter type 4 (GLUT4), glucocorticoid receptors β (GRβ) and peroxisome proliferator-activated receptor γ (PPARγ) were significantly (P < .05) increased in A-549 and MCF-7 with lipid vesicles. The level of telomerase activity was found to be significantly (P < .05) downregulated in DEX-treated A-549 and MCF-7 cancer cells. Our results have clearly shown that DEX treatment induces inhibition of cell growth by differentiating into adipocyte-like cells in dexamethasone sensitive cancer cells.

Keywords: Human; adipocytes; cancer; cell differentiation; dexamethasone.

Figure 1.

Analysis of PDT in human cancer and normal cell lines of various types exposed to 0 (untreated control, ▪) and 1 μg/ml DEX (▪) for 2 weeks. A and B indicate significant (P < .05) difference between untreated control and DEX treatment, respectively.

Figure 2.

Effect of DEX treatment on glucose uptake in human cancer and normal cell lines of various types. Each cancer and normal cell lines were exposed to A-DMEM 0 (untreated control, ▪) and 1 μg/ml DEX (▪) for 1 week without media change, respectively. Values indicates mean glucose concentration (ng/dl) per 1000 cells consumed during in vitro culture. A and B indicate significant (P < .05) difference between untreated control and DEX treatment, respectively.

Figure 3.

In vitro differentiation into adipocyte-like cells by DEX treatment in human in A-549, MDA-MB-231, MCF-7 and U87-MG cancer cell lines. Mouse 3T3-L1 pre-adipocytes were used as an adipogenic control cells. Morphological alternation was evaluated after DEX treatment for 2 weeks under light microscope (A, B, C, D and E) and adiposomes like-cellular organelles were observed in A-549, MCF-7 cancer cells and 3T3-L1 mouse pre-adipocytes (B, C and E). Further, accumulation of intracellular lipid droplets was stained with oil red O solution (F, G, H, I and J) and adiposomes stained with red spots were also observed in A-549, MCF-7 cancer cells and mouse 3T3-L1 pre-adipocytes (J, H and J). Scale: 50 μm.

Figure 4.

Expression level of GLUT4, GRβ and PPARγ related with adipogenesis by RT-PCR in A-549, MDA-MB-231, MCF-7 and U87-MG cancer cell lines. A and B indicates significant (P<.05) difference between untreated control (▪) and 1 μg/ml DEX treatment (▪), respectively.

Figure 5.

Activity of senescence-associated-β-galactosidase in untreated control (A, B, C and D) and 1 μg/ml DEX-treated (E, F, G and H) A-549, MDA-MB-231, MCF-7 and U87-MG cancer cells. Morphological change with lipid droplets were also observed, but change of senescence-associated-β-galactosidase activity not displayed by DEX treatment.

Figure 6.

Expression level of TERT analyzed by RT-PCR (A) and telomerase activity (B) analyzed by RQ-TRAP (B) in untreated control (▪) and 1 μg/ml DEX-treated (▪) A-549, MDA-MB-231, MCF-7 and U87-MG cancer cells. A and B indicate significant (P<.05) difference between untreated control and DEX treatment, respectively.