author_facet SIDDIQUI, Rafat A.
JENSKI, Laura J.
HARVEY, Kevin A.
WIESEHAN, Jacqueline D.
STILLWELL, William
ZALOGA, Gary P.
SIDDIQUI, Rafat A.
JENSKI, Laura J.
HARVEY, Kevin A.
WIESEHAN, Jacqueline D.
STILLWELL, William
ZALOGA, Gary P.
author SIDDIQUI, Rafat A.
JENSKI, Laura J.
HARVEY, Kevin A.
WIESEHAN, Jacqueline D.
STILLWELL, William
ZALOGA, Gary P.
spellingShingle SIDDIQUI, Rafat A.
JENSKI, Laura J.
HARVEY, Kevin A.
WIESEHAN, Jacqueline D.
STILLWELL, William
ZALOGA, Gary P.
Biochemical Journal
Cell-cycle arrest in Jurkat leukaemic cells: a possible role for docosahexaenoic acid
Cell Biology
Molecular Biology
Biochemistry
author_sort siddiqui, rafat a.
spelling SIDDIQUI, Rafat A. JENSKI, Laura J. HARVEY, Kevin A. WIESEHAN, Jacqueline D. STILLWELL, William ZALOGA, Gary P. 0264-6021 1470-8728 Portland Press Ltd. Cell Biology Molecular Biology Biochemistry http://dx.doi.org/10.1042/bj20021667 <jats:p>Docosahexaenoic acid (DHA) is known to have anti-cancer activities by mechanisms that are not well understood. In the present study, we test one possible pathway for DHA action in Jurkat leukaemic cells. Low doses of DHA (10μM) are shown to induce cell-cycle arrest, whereas higher doses are cytotoxic. However, when cells that were pre-treated with 10μM DHA are given an additional 10μM DHA dose, cell viability rapidly decreases. Immunoblotting reveals that repeated low doses of DHA results in activation of caspase 3, implying induction of apoptosis. DHA (10μM) is shown to increase ceramide levels after 6h of incubation and, after 24h, the cells appear to be arrested in S phase. With DHA, the amount of phosphorylated retinoblastoma protein (pRb) decreases significantly. Western blot analysis also shows that DHA greatly reduces the level of cyclin A, while increasing the level of p21 WAF1, a cellular inhibitor of cyclin A/cyclin-dependent kinase 2 (cdk2) activity. Furthermore, the observed DHA-induced doubling of the ratio of hypophosphorylated pRb (hypo-pRb) to total pRb is inhibited by tautomycin and phosphatidic acid (PA), known inhibitors of protein phosphatase 1 (PP1), and by the PP2 inhibitor okadaic acid. The present study demonstrates one possible connected pathway for DHA action. By this pathway, low doses of DHA increase ceramide levels, which leads to inhibition of cdk2 activity and stimulation of PP1 and PP2A. The net effect of cdk2 inhibition and protein phosphatase activation is an inhibition of pRb phosphorylation, consequently arresting Jurkat cell growth.</jats:p> Cell-cycle arrest in Jurkat leukaemic cells: a possible role for docosahexaenoic acid Biochemical Journal
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title Cell-cycle arrest in Jurkat leukaemic cells: a possible role for docosahexaenoic acid
title_unstemmed Cell-cycle arrest in Jurkat leukaemic cells: a possible role for docosahexaenoic acid
title_full Cell-cycle arrest in Jurkat leukaemic cells: a possible role for docosahexaenoic acid
title_fullStr Cell-cycle arrest in Jurkat leukaemic cells: a possible role for docosahexaenoic acid
title_full_unstemmed Cell-cycle arrest in Jurkat leukaemic cells: a possible role for docosahexaenoic acid
title_short Cell-cycle arrest in Jurkat leukaemic cells: a possible role for docosahexaenoic acid
title_sort cell-cycle arrest in jurkat leukaemic cells: a possible role for docosahexaenoic acid
topic Cell Biology
Molecular Biology
Biochemistry
url http://dx.doi.org/10.1042/bj20021667
publishDate 2003
physical 621-629
description <jats:p>Docosahexaenoic acid (DHA) is known to have anti-cancer activities by mechanisms that are not well understood. In the present study, we test one possible pathway for DHA action in Jurkat leukaemic cells. Low doses of DHA (10μM) are shown to induce cell-cycle arrest, whereas higher doses are cytotoxic. However, when cells that were pre-treated with 10μM DHA are given an additional 10μM DHA dose, cell viability rapidly decreases. Immunoblotting reveals that repeated low doses of DHA results in activation of caspase 3, implying induction of apoptosis. DHA (10μM) is shown to increase ceramide levels after 6h of incubation and, after 24h, the cells appear to be arrested in S phase. With DHA, the amount of phosphorylated retinoblastoma protein (pRb) decreases significantly. Western blot analysis also shows that DHA greatly reduces the level of cyclin A, while increasing the level of p21 WAF1, a cellular inhibitor of cyclin A/cyclin-dependent kinase 2 (cdk2) activity. Furthermore, the observed DHA-induced doubling of the ratio of hypophosphorylated pRb (hypo-pRb) to total pRb is inhibited by tautomycin and phosphatidic acid (PA), known inhibitors of protein phosphatase 1 (PP1), and by the PP2 inhibitor okadaic acid. The present study demonstrates one possible connected pathway for DHA action. By this pathway, low doses of DHA increase ceramide levels, which leads to inhibition of cdk2 activity and stimulation of PP1 and PP2A. The net effect of cdk2 inhibition and protein phosphatase activation is an inhibition of pRb phosphorylation, consequently arresting Jurkat cell growth.</jats:p>
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author SIDDIQUI, Rafat A., JENSKI, Laura J., HARVEY, Kevin A., WIESEHAN, Jacqueline D., STILLWELL, William, ZALOGA, Gary P.
author_facet SIDDIQUI, Rafat A., JENSKI, Laura J., HARVEY, Kevin A., WIESEHAN, Jacqueline D., STILLWELL, William, ZALOGA, Gary P., SIDDIQUI, Rafat A., JENSKI, Laura J., HARVEY, Kevin A., WIESEHAN, Jacqueline D., STILLWELL, William, ZALOGA, Gary P.
author_sort siddiqui, rafat a.
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container_title Biochemical Journal
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description <jats:p>Docosahexaenoic acid (DHA) is known to have anti-cancer activities by mechanisms that are not well understood. In the present study, we test one possible pathway for DHA action in Jurkat leukaemic cells. Low doses of DHA (10μM) are shown to induce cell-cycle arrest, whereas higher doses are cytotoxic. However, when cells that were pre-treated with 10μM DHA are given an additional 10μM DHA dose, cell viability rapidly decreases. Immunoblotting reveals that repeated low doses of DHA results in activation of caspase 3, implying induction of apoptosis. DHA (10μM) is shown to increase ceramide levels after 6h of incubation and, after 24h, the cells appear to be arrested in S phase. With DHA, the amount of phosphorylated retinoblastoma protein (pRb) decreases significantly. Western blot analysis also shows that DHA greatly reduces the level of cyclin A, while increasing the level of p21 WAF1, a cellular inhibitor of cyclin A/cyclin-dependent kinase 2 (cdk2) activity. Furthermore, the observed DHA-induced doubling of the ratio of hypophosphorylated pRb (hypo-pRb) to total pRb is inhibited by tautomycin and phosphatidic acid (PA), known inhibitors of protein phosphatase 1 (PP1), and by the PP2 inhibitor okadaic acid. The present study demonstrates one possible connected pathway for DHA action. By this pathway, low doses of DHA increase ceramide levels, which leads to inhibition of cdk2 activity and stimulation of PP1 and PP2A. The net effect of cdk2 inhibition and protein phosphatase activation is an inhibition of pRb phosphorylation, consequently arresting Jurkat cell growth.</jats:p>
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spelling SIDDIQUI, Rafat A. JENSKI, Laura J. HARVEY, Kevin A. WIESEHAN, Jacqueline D. STILLWELL, William ZALOGA, Gary P. 0264-6021 1470-8728 Portland Press Ltd. Cell Biology Molecular Biology Biochemistry http://dx.doi.org/10.1042/bj20021667 <jats:p>Docosahexaenoic acid (DHA) is known to have anti-cancer activities by mechanisms that are not well understood. In the present study, we test one possible pathway for DHA action in Jurkat leukaemic cells. Low doses of DHA (10μM) are shown to induce cell-cycle arrest, whereas higher doses are cytotoxic. However, when cells that were pre-treated with 10μM DHA are given an additional 10μM DHA dose, cell viability rapidly decreases. Immunoblotting reveals that repeated low doses of DHA results in activation of caspase 3, implying induction of apoptosis. DHA (10μM) is shown to increase ceramide levels after 6h of incubation and, after 24h, the cells appear to be arrested in S phase. With DHA, the amount of phosphorylated retinoblastoma protein (pRb) decreases significantly. Western blot analysis also shows that DHA greatly reduces the level of cyclin A, while increasing the level of p21 WAF1, a cellular inhibitor of cyclin A/cyclin-dependent kinase 2 (cdk2) activity. Furthermore, the observed DHA-induced doubling of the ratio of hypophosphorylated pRb (hypo-pRb) to total pRb is inhibited by tautomycin and phosphatidic acid (PA), known inhibitors of protein phosphatase 1 (PP1), and by the PP2 inhibitor okadaic acid. The present study demonstrates one possible connected pathway for DHA action. By this pathway, low doses of DHA increase ceramide levels, which leads to inhibition of cdk2 activity and stimulation of PP1 and PP2A. The net effect of cdk2 inhibition and protein phosphatase activation is an inhibition of pRb phosphorylation, consequently arresting Jurkat cell growth.</jats:p> Cell-cycle arrest in Jurkat leukaemic cells: a possible role for docosahexaenoic acid Biochemical Journal
spellingShingle SIDDIQUI, Rafat A., JENSKI, Laura J., HARVEY, Kevin A., WIESEHAN, Jacqueline D., STILLWELL, William, ZALOGA, Gary P., Biochemical Journal, Cell-cycle arrest in Jurkat leukaemic cells: a possible role for docosahexaenoic acid, Cell Biology, Molecular Biology, Biochemistry
title Cell-cycle arrest in Jurkat leukaemic cells: a possible role for docosahexaenoic acid
title_full Cell-cycle arrest in Jurkat leukaemic cells: a possible role for docosahexaenoic acid
title_fullStr Cell-cycle arrest in Jurkat leukaemic cells: a possible role for docosahexaenoic acid
title_full_unstemmed Cell-cycle arrest in Jurkat leukaemic cells: a possible role for docosahexaenoic acid
title_short Cell-cycle arrest in Jurkat leukaemic cells: a possible role for docosahexaenoic acid
title_sort cell-cycle arrest in jurkat leukaemic cells: a possible role for docosahexaenoic acid
title_unstemmed Cell-cycle arrest in Jurkat leukaemic cells: a possible role for docosahexaenoic acid
topic Cell Biology, Molecular Biology, Biochemistry
url http://dx.doi.org/10.1042/bj20021667