The present status in all-trans retinoic acid (ATRA) treatment for acute promyelocytic leukemia patients: further understanding and comprehensive strategy are required in the future

A novel all-trans retinoid acid derivative N-(3-trifluoromethyl- phenyl)- retinamide inhibits lung adenocarcinoma A549 cell migration through down-regulating expression of myosin light chain kinase

AIM

To observe the effects of a novel all-trans retinoid acid (ATRA) derivative, N-(3-trifluoromethyl-phenyl)- retinamide (ATPR), on lung adenocarcinoma A549 cells and to explore the potential mechanism of ATPR inhibiting of A549 cell migration.

MATERIALS AND METHODS

The cytotoxicity of ATRA and ATPR on A549 cells was assessed using MTT assay. Wound healing assays were used to analyze the influences of ATRA, ATPR, ML-7 (a highly selective inhibitor of myosin light chain kinase (MLCK)), PMA (an activator of MAPKs) and PD98059 (a selective inhibitor of ERK1/2) on the migration of A549 cells. Expression of MLCK and phosphorylation of myosin light chain (MLC) were assessed by Western blotting.

RESULTS

ATRA and ATPR inhibited the proliferation of A549 cells in a dose- and time-dependent manner, and the effect of ATPR was much more remarkable compared with ATRA. Relative migration rate and migration distance of A549 cells both decreased significantly after treatment with ATPR or ML-7. The effect on cell migration of PD98059 combining ATPR treatment was more notable than that of ATPR alone. Moreover, compared with control groups, the expression levels of MLCK and phosphorylated MLC in A549 cells were both clearly reduced in ATRA and ATPR groups.

CONCLUSIONS

ATPR could suppress the migration and invasion of A549 cells, and the mechanism might be concerned with down- regulating the expression of MLCK in the ERK-MAPK signaling pathway, pointing to therapeutic prospects in lung cancer.

Differentiation induction of human leukemia cells (HL60) by a combination of 1,25-dihydroxyvitamin D3 and retinoic acid (all trans or 9-cis)

1,25(OH)2D3 and two stereoisomers of retinoic acid, all trans and 9-cis retinoic acid, are regulators of cell proliferation and differentiation. The aim of this study was to evaluate the effects of a combination of 1,25(OH)2D3 and retinoic acid (all trans or 9-cis) on proliferation and cell differentiation of the human promyelocytic leukemia cell line HL60, and to test the reversibility of the induced differentiation. Cell proliferation was inhibited as expected by 1,25(OH)2D3 and all trans retinoic acid alone (IC50 of cell survival was 4 x 10(-7) M, 9 x 10(-6) M and 9 x 10(-7) M for 1,25(OH)2D3, all trans and 9-cis retinoic acid, respectively). Combination of 1,25(OH)2D3 and either form of retinoic acid resulted in a partially additive decrease in cell proliferation. 1,25(OH)2D3 induced a monocytic differentiation (100% CD14+ cells with 10(-7) M 1,25(OH)2D3), while retinoic acid led to a predominantly granulocytic differentiation (36 and 42% CD67+ cells with 10(-6) M all trans and 9-cis retinoic acid, respectively). Additive effects on differentiation were observed upon combination of subtherapeutical doses of the drugs, achieving a mainly monocytic population, demonstrating the dominant role of 1,25(OH)2D3 in determining the direction of differentiation. The effects on proliferation and differentiation of the solitary drugs were reversible, while the proliferation arrest and differentiation induced by the combination persisted and even progressed after withdrawal of the drugs. We conclude that 1,25(OH)2D3 and retinoic acid (all trans or 9-cis) exert additive effects on inhibition of proliferation and induction of cell differentiation of HL60 cells, leading to a persistent differentiation, even after drug withdrawal.

Establishment of a retrodifferentiated cell line from a single differentiated rat myelomonocytic leukemia cell: possible roles of retrodifferentiation in relapses of leukemia after differentiation-inducing therapy

In order to demonstrate possible roles of retrodifferentiation in relapses after differentiation therapies, we have established a retrodifferentiated cell line (RD-1) from a single rat myelomonocytic leukemia cell which differentiated into a macrophage-like cell by treatment with lipopolysaccharide (LPS). The established RD-1 cells showed microscopic features slightly maturer than their parent cells. The RD-1 cells had the ability to differentiate into macrophage-like cells by treatment with fewer doses of LPS than those for parent cells. All rats inoculated with the parent cells (more than 10(2)/rat) died within 50 days. Rats inoculated with 10(4) RD-1 cells survived for more than 120 days, whereas two out of four rats inoculated with 10(5) cells and all the rats inoculated with 5 x 10(5) cells died of leukemia. These results suggest that RD-1 cells are retrodifferentiated cells from a single rat myelomonocytic leukemia cell which differentiated into a macrophage-like cell; they have similar phenotypes and lower tumorigenicity than the parent cells and they also suggest that the appearance of retrodifferentiated leukemia cells may be responsible for relapse after differentiation therapy for leukemia in some cases.