Scriptaid effects on breast cancer cell lines.

In breast cancer tumor expression of estrogen receptors (ERs) is important as a marker of prognosis and mostly as a predictor of response to endocrine therapy. In fact, the loss of α-ER expression leads to unresponsiveness to anti-hormone treatment. In a significant fraction of breast cancers, this loss of expression is a result of epigenetic mechanisms, such as DNA methylation and histone deacetylation, within the α-ER promoter. Previous studies have shown that pharmacologic inhibition of these mechanisms using the DNA methyltransferase inhibitor, 5-aza-2-deoxycytidine (AZA), and the histone deacetylase (HDAC) inhibitor, Trichostatin A (TSA), results in expression of functional α-ER mRNA and protein. Moreover, the activity of a novel HDAC inhibitor, Scriptaid, has been shown to induce inhibition of tumor growth in breast cancer and to cause re-expression of functional α-ER in α-ER negative breast cancer cells. We sought to better characterize the effects of Scriptaid on cell growth, apoptosis, and α-ER expression in α-ER-positive (MCF-7), α-ER-negative (MDA-MB-231), and α-ER-negative/Her-2 over-expressing (SKBr-3) human breast cancer cell lines. In all of these cell lines Scriptaid treatment resulted in significant growth inhibition and apoptosis, and RT-PCR confirmed an increase of α-ER mRNA transcript in MDA-MB-231 after 48 h of Scriptaid treatment. Furthermore, following treatment with Scriptaid, the formerly unresponsive MDA-MB-231 and SKBr-3 breast cancer cells became responsive to tamoxifen. These results show that the HDAC inhibitor Scriptaid is able to sensitize tamoxifen hormone-resistant breast cancer cells, and that Scriptaid or related HDAC inhibitors are candidates for further study in breast cancer.

Stem cell-mediated muscle regeneration and repair in aging and neuromuscular diseases.

One of the most exciting aspirations of current medical science is the regeneration of damaged body parts. The capacity of adult tissues to regenerate in response to injury stimuli represents an important homeostatic process that until recently was thought to be limited in mammals to tissues with high turnover such as blood and skin. However, it is now generally accepted that each tissue type, even those considered post-mitotic, such as nerve or muscle, contains a reserve of undifferentiated progenitor cells, loosely termed stem cells, participating in tissue regeneration and repair. Skeletal muscle regeneration is a coordinate process in which several factors are sequentially activated to maintain and preserve muscle structure and function upon injury stimuli. In this review, we will discuss the role of stem cells in muscle regeneration and repair and the critical role of specific factors, such as IGF-1, vasopressin and TNF-alpha, in the modulation of the myogenic program and in the regulation of muscle regeneration and homeostasis.

RB and cell cycle progression.

The Rb protein is a tumor suppressor, which plays a pivotal role in the negative control of the cell cycle and in tumor progression. It has been shown that Rb protein (pRb) is responsible for a major G1 checkpoint, blocking S-phase entry and cell growth. The retinoblastoma family includes three members, Rb/p105, p107 and Rb2/p130, collectively referred to as 'pocket proteins'. The pRb protein represses gene transcription, required for transition from G1 to S phase, by directly binding to the transactivation domain of E2F and by binding to the promoter of these genes as a complex with E2F. pRb represses transcription also by remodeling chromatin structure through interaction with proteins such as hBRM, BRG1, HDAC1 and SUV39H1, which are involved in nucleosome remodeling, histone acetylation/deacetylation and methylation, respectively. Loss of pRb functions may induce cell cycle deregulation and so lead to a malignant phenotype. Gene inactivation of pRB through chromosomal mutations is one of the principal reasons for retinoblastoma tumor development. Functional inactivation of pRb by viral oncoprotein binding is also shown in many neoplasias such as cervical cancer, mesothelioma and AIDS-related Burkitt's lymphoma.