Mitosis-independent survivin gene expression in vivo and regulation by p53

Survivin is an essential mitotic gene, and this has been speculated to reflect its primary function in development and cancer. Here, we generated a knock-in transgenic mouse (SVVp-GFP) in which a green fluorescent protein (GFP) reporter gene was placed under the control of the survivin promoter that regulates transcription at mitosis. The expression of endogenous survivin was widespread in mouse tissues during development and shortly after birth. In contrast, GFP reactivity was undetectable in transgenic mouse embryos, and was largely limited postnatally to mitotic cells in the testes. Double transgenic mice generated in the tumor-prone Min/+ background exhibited intestinal adenomas that strongly expressed endogenous survivin, but only isolated GFP-positive cells. Conversely, dysplastic adenomas (16%) stained intensely for GFP, and revealed focal reactivity for mutant, but not wild-type, p53. The expression of GFP was increased by approximately 10-fold in p53(-/-) as opposed to p53(+/+) HCT116 colorectal cancer cells, and reintroduction of p53 in p53(-/-) cells abolished GFP expression. Therefore, the mitotic transcription of the survivin gene is highly restricted in vivo, and unexpectedly negatively regulated by p53. Contrary to a commonly held view, the dominant function(s) of survivin in development and tumor ontogeny are largely cell cycle-independent

Survivin as a global target of intrinsic tumor suppression networks

Despite the constant exposure to genomic insults that may lead to malignancy, cancer is surprisingly a relatively rare occurrence, and this is largely credited to an elaborate network of endogenous tumor suppression. Many effectors of tumor suppression have been identified, and their functions when activated in damaged cells have in large part been elucidated. What is less clear is whether there are common target gene(s) of tumor suppression, whose expression must be ablated in order to block transformation and preserve cellular homeostasis. Fresh experimental evidence suggests that silencing of the mitotic regulator and cell death inhibitor, survivin, is a universal requirement for successful tumor suppression in humans

A CERTain Role for Ceramide in Taxane-Induced Cell Death

An unexpected benefit of functional genomic screens is that at times they answer questions that they were not designed to ask. A siRNA screen reported by Swanton et al. in this issue of Cancer Cell reveals that silencing of spindle assembly checkpoint genes facilitates mitotic slippage, resulting in escape from taxane-induced cell death, aneuploidy, and chromosomal instability, hallmarks of taxane resistance. Unexpectedly, the screen disclosed that the sphingolipid ceramide is a key regulator of the taxane-mediated spindle assembly checkpoint and taxane-induced cell death. Ceramide metabolism thus serves as a legitimate target for modulation of taxane effect on tumors

Survivin at a glance

Survivin (also known as BIRC5) is an evolutionarily conserved eukaryotic protein that is essential for cell division and can inhibit cell death. Normally it is only expressed in actively proliferating cells, but is upregulated in most, if not all cancers; consequently, it has received significant attention as a potential oncotherapeutic target. In this Cell Science at a Glance article and accompanying poster, we summarise our knowledge of survivin 21 years on from its initial discovery. We describe the structure, expression and function of survivin, highlight its interactome and conclude by describing anti-survivin strategies being trialled

A p34cdc2 survival checkpoint in cancer

AbstractA checkpoint surveying the entry into mitosis responds to defects in spindle microtubule assembly/stability. This has been used to trigger apoptosis in cancer cells, but how the spindle checkpoint couples to the cell survival machinery has remained elusive. Here, we report that microtubule stabilization engenders a survival pathway that depends on elevated activity of p34cdc2 kinase and increased expression of the apoptosis inhibitor and mitotic regulator, survivin. Pharmacologic, genetic, or molecular ablation of p34cdc2 kinase after microtubule stabilization resulted in massive apoptosis independent of p53, suppression of tumor growth, and indefinite survival without toxicity in mice. By ablating this survival checkpoint, inhibitors of p34cdc2 kinase could safely improve the efficacy of microtubule-stabilizing agents used to treat common cancers

Activated checkpoint kinase 2 provides a survival signal for tumor cells

Tumor cells often become resistant to DNA damage-based therapy; however, the underlying mechanisms are not yet understood. Here, we show that tumor cells exposed to DNA damage counteract cell death by releasing the antiapoptotic protein, survivin, from mitochondria. This is independent of p53, and requires activated checkpoint kinase 2 (Chk2), a putative tumor suppressor. Molecular or genetic targeting of Chk2 prevents the release of survivin from mitochondria, enhances DNA damage-induced tumor cell apoptosis, and inhibits the growth of resistant in vivo tumors. Therefore, activated Chk2 circumvents its own tumor-suppressive functions by promoting tumor cell survival. Inhibiting Chk2 in combination with DNA-damaging agents may provide a rational approach for treating resistant tumors

Suppression of survivin phosphorylation on Thr34 by flavopiridol enhances tumor cell apoptosis

Survivin is a member of the inhibitor of apoptosis gene family that is expressed in most human cancers and may facilitate evasion from apoptosis and aberrant mitotic progression. Here, exposure of breast carcinoma MCF-7 or cervical carcinoma HeLa cells to anticancer agents, including Adriamycin, Taxol, or UVB resulted in a 4-5-fold increased survivin expression. Changes in survivin levels after anticancer treatment did not involve modulation of survivin mRNA expression and were independent of de novo gene transcription. Conversely, inhibition of survivin phosphorylation on Thr(34) by the cyclin-dependent kinase inhibitor flavopiridol resulted in loss of survivin expression, and nonphosphorylatable survivin Thr(34)--\u3eAla exhibited accelerated clearance as compared with wild-type survivin. Sequential ablation of survivin phosphorylation on Thr(34) enhanced tumor cell apoptosis induced by anticancer agents independently of p53 and suppressed tumor growth without toxicity in a breast cancer xenograft model in vivo. These data suggest that Thr(34) phosphorylation critically regulates survivin levels in tumor cells and that sequential ablation of p34(cdc2) kinase activity may remove the survivin viability checkpoint and enhance apoptosis in tumor cells

Endocarditis: Cardiac Surgery Treatment/A Thrilling Challenge in Cardiac Surgery

Infective endocarditis is a rare but life-threatening disease that has a major impact on healthcare resources. It is heterogeneous in etiology, clinical manifestations, and course. The timing of surgery remains a topic of debate. Some authors promote an early surgical approach to improve the outcomes. There are different points of view between American and European guidelines regarding the relative priority of surgery over medical treatment. Anyway, multidisciplinary teams and multimodality strategies are advocated in order to optimize the treatment according to the individual needs of the patients. The early surgical approach may represent a valuable treatment option for high-risk patients. In this chapter, we discuss the latest evidence on surgical approaches, potential pitfalls, and the controversial issues in the contemporary practice of infective endocarditis