Abnormal behavior of protein kinase C in the human myeloma cell line, RPMI 8226

In this study, we show that both all-trans-retinoic acid (atRA) and 9-cis-retinoic acid (9-cis-RA) are potent inducers of tissue transglutaminase (TGase II), an enzyme involved in apoptosis, at the level of both enzyme activity and mRNA in the human myeloma cell line RPMI 8226. RPMI 8226 cells were shown to express mRNAs for all the retinoid receptors subtypes, ie, RARα, RARβ, RARγ, RXRα, RXRβ, and RXRγ. To identify which of these receptors are involved in regulating TGase II expression, several receptor-selective synthetic retinoids were used. Neither CD367, a very potent retinoid that selectively binds and activates receptors of the RAR family, nor CD2425, an RXR-selective agonist, induced TGase II when used alone. However, combination of CD367 and CD2425 resulted in nearly full induction of the enzyme. Moreover, when used in combination with atRA, CD367 partially inhibited the atRA-dependent induction of TGase II, whereas CD2425 enhanced it. The effects of Am 580, CD417, and CD437, three synthetic retinoids selective for the RARs subtypes RARα, RARβ, and RARγ, respectively, were also investigated. None of these compounds was able to induce TGase II when used alone; however, the combination of each of them with CD2425 resulted in strong induction of the enzyme activity, reaching 30% to 50% of the values obtained in the presence of retinoic acid and suggesting functional redundancy between the RAR subtypes. Finally, treatment with atRA or the combination of CD367 and CD2425, but not with CD367 or CD2425 alone, was also shown to trigger apoptosis in RPMI 8226 cells, with prominent accumulation of TGase II immunoreactivity in apoptotic cells. Taken together these data suggest that the induction of TGase II expression and apoptosis in the RPMI 8226 myeloma cell line required ligand-dependent activation of both the RAR and RXR receptors.

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A Photodynamic Pathway to Apoptosis Induced by Hypericin in Human Myeloma ARH-77 Cell Line: Possible Relevance to Photodynamic Therapy.

Blood ◽

10.1182/blood.v106.11.5076.5076 ◽

2005 ◽

Vol 106 (11) ◽

pp. 5076-5076

Author(s):

Ferit Avcu ◽

Ali U. Ural ◽

Yusuf Baran ◽

Gungor Sobaci ◽

Mustafa Deveci ◽

...

Keyword(s):

Cell Death ◽

Protein Kinase C ◽

Protein Kinase ◽

Cell Line ◽

Apoptotic Cell ◽

Flow Cytometric Analysis ◽

Myeloma Cell ◽

Dependent Manner ◽

Myeloma Cell Line ◽

Kinase C

Abstract Hypericin, a photosensitizing plant pigment from Hypericum perforatum, is a protein tyrosine kinase inhibitor that has been exploited in models for anti-tumor and anti-viral activity. In this study, we investigated the effects of hypericin on the human myeloma cell line ARH-77 as a model to determine whether hypericin-induced cell death is available. The cells were incubated with hypericin at concentrations ranging from 0.001 to 10 microg/ml in RPMI at 37°C in 5% CO2 atmosphere for 4 h. Then, the cells were irradiated at 532 nm (fluence=24 J/cm2) using a dye laser pumped by an argon laser (Orion). After 72 h exposure, the IC50 of hypericin was 0.005 microg/ml as determined by the MTT assay. Hypericin exerted phototoxic effect on ARH-77 cells, while it did not produce toxic effect in the absence of irradiation. After 72 h exposure to 0.005 microg/ml photoactive hypericin, apoptosis was assessed by morphological changes, DNA fragmentation and flow cytometric analysis using Annexin V and propidium iodide staining. Most of the cells were accumulated in the late stage of apoptosis and these cells were brightly stained and fragmented nuclei and cytoplasmic blebbing were observed. A decrease in the number of apoptotic cells was detected when protein kinase C was inhibited by addition of staurosporine to photoactive hypericin induced ARH-77 cells. From these results, we demonstrated that exposing myeloma cell line ARH-77 to photoactive hypericin inhibits cell growth in a dose dependent manner, induces apoptotic cell death by protein kinase C activation, and provides a rationale for potential applications in vivo.

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Evidence for the Involvement of Both Retinoic Acid Receptor- and Retinoic X Receptor-Dependent Signaling Pathways in the Induction of Tissue Transglutaminase and Apoptosis in the Human Myeloma Cell Line RPMI 8226

Blood ◽

10.1182/blood.v91.7.2423 ◽

1998 ◽

Vol 91 (7) ◽

pp. 2423-2432 ◽

Cited By ~ 22

Author(s):

Bertrand Joseph ◽

Olga Lefebvre ◽

Claude Méreau-Richard ◽

Pierre-Marie Danzé ◽

Marie-Thérèse Belin-Plancot ◽

...

Keyword(s):

Enzyme Activity ◽

Retinoic Acid ◽

Cell Line ◽

Retinoic Acid Receptor ◽

Tissue Transglutaminase ◽

Myeloma Cell ◽

Myeloma Cell Line ◽

Human Myeloma Cell Line ◽

Rpmi 8226 ◽

Human Myeloma Cell

AbstractIn this study, we show that both all-trans-retinoic acid (atRA) and 9-cis-retinoic acid (9-cis-RA) are potent inducers of tissue transglutaminase (TGase II), an enzyme involved in apoptosis, at the level of both enzyme activity and mRNA in the human myeloma cell line RPMI 8226. RPMI 8226 cells were shown to express mRNAs for all the retinoid receptors subtypes, ie, RARα, RARβ, RARγ, RXRα, RXRβ, and RXRγ. To identify which of these receptors are involved in regulating TGase II expression, several receptor-selective synthetic retinoids were used. Neither CD367, a very potent retinoid that selectively binds and activates receptors of the RAR family, nor CD2425, an RXR-selective agonist, induced TGase II when used alone. However, combination of CD367 and CD2425 resulted in nearly full induction of the enzyme. Moreover, when used in combination with atRA, CD367 partially inhibited the atRA-dependent induction of TGase II, whereas CD2425 enhanced it. The effects of Am 580, CD417, and CD437, three synthetic retinoids selective for the RARs subtypes RARα, RARβ, and RARγ, respectively, were also investigated. None of these compounds was able to induce TGase II when used alone; however, the combination of each of them with CD2425 resulted in strong induction of the enzyme activity, reaching 30% to 50% of the values obtained in the presence of retinoic acid and suggesting functional redundancy between the RAR subtypes. Finally, treatment with atRA or the combination of CD367 and CD2425, but not with CD367 or CD2425 alone, was also shown to trigger apoptosis in RPMI 8226 cells, with prominent accumulation of TGase II immunoreactivity in apoptotic cells. Taken together these data suggest that the induction of TGase II expression and apoptosis in the RPMI 8226 myeloma cell line required ligand-dependent activation of both the RAR and RXR receptors.

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