Cyclin-Dependent Kinase Inhibitor p21

Publication Title: 
The EMBO journal

Telomere loss has been proposed as a mechanism for counting cell divisions during aging in normal somatic cells. How such a mitotic clock initiates the intracellular signalling events that culminate in G1 cell cycle arrest and senescence to restrict the lifespan of normal human cells is not known. We investigated the possibility that critically short telomere length activates a DNA damage response pathway involving p53 and p21(WAF1) in aging cells.

Author(s): 
Vaziri, H.
West, M. D.
Allsopp, R. C.
Davison, T. S.
Wu, Y. S.
Arrowsmith, C. H.
Poirier, G. G.
Benchimol, S.
Publication Title: 
Oncogene

Replicative senescence is thought to be a significant barrier to human tumorigenesis, which in human fibroblasts, and many other cell types, can be overcome experimentally by combined loss of function of p53 and Rb 'pathways'. To avoid the confounding pleiotropic effects of HPVE7 frequently used in such studies, here we have employed retroviral vectors over-expressing CDK4 or CDK6 as a more representative model of naturally-occurring mutations targeting the Rb pathway.

Author(s): 
Morris, Mark
Hepburn, Peter
Wynford-Thomas, David
Publication Title: 
Experimental Cell Research

Numerous studies have shown that supplementation of the growth medium of human fibroblasts with dexamethasone at physiologic concentrations extends replicative lifespan up to 30%. While this extension of lifespan has been used to probe various aspects of the senescent phenotype, no mechanism for the increased lifespan of human fibroblasts grown in the presence of dexamethasone has ever been identified.

Author(s): 
Mawal-Dewan, Madhu
Frisoni, Lorenza
Cristofalo, Vincent J.
Sell, Christian
Publication Title: 
EMBO reports

Current models envision replicative senescence to be under dual control by the p53 and retinoblastoma (RB) tumour-suppressor pathways. The role of the p16(INK4a)-RB pathway is controversial, and the function of RB in human cells has not been tested directly. We used targeted homologous recombination to knock out one copy of RB in presenescent human fibroblasts. During entry into senescence, RB+/- cells underwent spontaneous loss of heterozygosity and the resultant RB-/- clones bypassed senescence. The extended lifespan phase was eventually terminated by a crisis-like state.

Author(s): 
Wei, Wenyi
Herbig, Utz
Wei, Shan
Dutriaux, Annie
Sedivy, John M.
Publication Title: 
The EMBO journal

Telomere shortening in normal human cells causes replicative senescence, a p53-dependent growth arrest state, which is thought to represent an innate defence against tumour progression. However, although it has been postulated that critical telomere loss generates a 'DNA damage' signal, the signalling pathway(s) that alerts cells to short dysfunctional telomeres remains only partially defined.

Author(s): 
Gire, VÈronique
Roux, Pierre
Wynford-Thomas, David
Brondello, Jean-Marc
Dulic, Vjekoslav
Publication Title: 
PloS One

The present day lifestyle heavily depends on industrial chemicals in the form of agriculture, cosmetics, textiles and medical products. Since the toxicity of the industrial chemicals has been a concern to human health, the need for alternative non-toxic natural products or adjuvants that serve as antidotes are in high demand. We have investigated the effects of Ayurvedic herb Ashwagandha (Withania somnifera) leaf extract on methoxyacetic acid (MAA) induced toxicity.

Author(s): 
Priyandoko, Didik
Ishii, Tetsuro
Kaul, Sunil C.
Wadhwa, Renu
Publication Title: 
PloS One

BACKGROUND AND PURPOSE: Withanolides are naturally occurring chemical compounds. They are secondary metabolites produced via oxidation of steroids and structurally consist of a steroid-backbone bound to a lactone or its derivatives. They are known to protect plants against herbivores and have medicinal value including anti-inflammation, anti-cancer, adaptogenic and anti-oxidant effects. Withaferin A (Wi-A) and Withanone (Wi-N) are two structurally similar withanolides isolated from Withania somnifera, also known as Ashwagandha in Indian Ayurvedic medicine.

Author(s): 
Vaishnavi, Kirti
Saxena, Nishant
Shah, Navjot
Singh, Rumani
Manjunath, Kavyashree
Uthayakumar, M.
Kanaujia, Shankar P.
Kaul, Sunil C.
Sekar, Kanagaraj
Wadhwa, Renu
Publication Title: 
International Journal of Oncology

We previously established a bioassay method to screen for compounds that activate the promoter activity of p21(WAF1/CIP1), a potent inhibitor of cyclin-dependent kinases, in a p53-independent manner. As an activator of p21(WAF1/CIP1) promoter activity, we isolated cryptolepine (CLP: 5-methyl indolo (2,3b)-quiniine), an indoloquinoline alkaloid, from the traditional Ayurvedic medicinal plant Sida cordifolia. We show here that CLP induces the expression of p21(WAF1/CIP1) with growth arrest in p53-mutated human osteosarcoma MG63 cells.

Author(s): 
Matsui, Taka-aki
Sowa, Yoshihiro
Murata, Hiroaki
Takagi, Koichi
Nakanishi, Ryoko
Aoki, Shunji
Yoshikawa, Masayuki
Kobayashi, Motomasa
Sakabe, Tomoya
Kubo, Toshikazu
Sakai, Toshiyuki
Publication Title: 
The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences

Ashwagandha is an Ayurvedic shrub that forms a common ingredient of health supplements, tonics, and Indian home remedies designed to promote health and quality of life. Though sustained through experience and history, there are only a limited laboratory studies and experimental evidence to its effects. In our efforts to characterize Ashwagandha activities and their molecular mechanisms, we initially prepared leaf extract of Ashwagandha (i-Extract) that showed tumor-inhibitory activity.

Author(s): 
Widodo, Nashi
Shah, Navjot
Priyandoko, Didik
Ishii, Tetsuro
Kaul, Sunil C.
Wadhwa, Renu
Publication Title: 
PloS One

The present day lifestyle heavily depends on industrial chemicals in the form of agriculture, cosmetics, textiles and medical products. Since the toxicity of the industrial chemicals has been a concern to human health, the need for alternative non-toxic natural products or adjuvants that serve as antidotes are in high demand. We have investigated the effects of Ayurvedic herb Ashwagandha (Withania somnifera) leaf extract on methoxyacetic acid (MAA) induced toxicity.

Author(s): 
Priyandoko, Didik
Ishii, Tetsuro
Kaul, Sunil C.
Wadhwa, Renu

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