No abstract

No abstract

p16 Ink4a is a protein involved in regulation of the cell cycle. Currently, p16 Ink4a is considered a tumor suppressor protein because of its physiological role and downregulated expression in a large number of tumors. Intriguingly, overexpression of p16 Ink4a has also been described in several tumors. This review attempts to elucidate when and why p16 Ink4a overexpression occurs, and to suggest possible implications of p16 Ink4a in the diagnosis, prognosis and treatment of cancer.

Embryonic stem (ES) cells are immortal and present the ability to self-renew while retaining their ability to differentiate. In contrast, most primary cells possess a limited proliferative potential, and when this is exhausted, undergo an irreversible growth arrest termed senescence. In primary cells, senescence can be also triggered by a variety of stress to which ES cells are highly refractory. Here the authors report that the proliferative capacity of murine ES cells closely correlates with high activity of different glycolytic enzymes, elevated glycolytic flux, and low mitochondrial oxygen consumption. The direct relation between glycolytic flux and the ability of ES cells to proliferate is further remarked in experiments where glycolysis or ES cell self-renewal was specifically inhibited. It was previously reported that the upregulation of glycolysis in primary cells results in life span extension. The authors hypothesize that the naturally high glycolytic flux observed in murine ES cells can be responsible for their unlimited proliferative potential.

No abstract

SummaryLow-dose exposures to common environmental chemicals that are deemed safe individually may be combining to instigate carcinogenesis, thereby contributing to the incidence of cancer. This risk may be overlooked by current regulatory practices and needs to be vigorously investigated.

Overexpression of RasG12V in primary cells induces a permanent growth arrest called oncogene-induced senescence (OIS) that serves as a fail-safe mechanism against malignant transformation. We have performed a genomewide small interfering RNA (siRNA) screen and a microRNA (miRNA) screen to identify mediators of OIS and show that siRNA-mediated knockdown of p21Waf1/Cip1 rescues from Ras G12V-induced senescence in human mammary epithelial cells (HMECs). Moreover, we isolated a total of 28 miRNAs that prevented Ras G12V -induced growth arrest, among which all of the miR-106b family members were present. In addition, we obtained a number of hits, miR-130b, miR-302a, miR-302b, miR302c, miR-302d, miR-512-3p and miR-515-3p with seed sequences very similar to miR-106b family members. We show that overexpression of all these miRNAs rescues HMECs from Ras . Our results establish an important role for the cell cycle inhibitor p21Waf1/Cip1 in growth control of HMECs and extend the repertoire of miRNAs that modulate the activity of this tumour suppressor.

No abstract