[Expressions of survivin and the splice variants survivin-2B and survivin-DeltaEx3 in bladder cancer and their clinical significance]

A new semisynthetic cardenolide analog 3β-[2-(1-amantadine)- 1-on-ethylamine]-digitoxigenin (AMANTADIG) affects G2/M cell cycle arrest and miRNA expression profiles and enhances proapoptotic survivin-2B expression in renal cell carcinoma cell lines

Cardiac glycosides are well known in the treatment of cardiovascular diseases; however, their application as treatment option for cancer patients is under discussion. We showed that the cardiac glycoside digitoxin and its analog AMANTADIG can inhibit the growth of renal cell carcinoma (RCC) cell lines and increase G2/M cell cycle arrest. To identify the signaling pathways and molecular basis of this G2/M arrest, microRNAs were profiled using microRNA arrays. Cardiac glycoside treatment significantly deregulated two microRNAs, miR-2278 and miR-670-5p. Pathway enrichment analysis showed that all cardiac glycoside treatments affected the MAPK and the axon guidance pathway. Within these pathways, three genes, MAPK1, NRAS and RAC2, were identified as in silico targets of the deregulated miRNAs. MAPK1 and NRAS are known regulators of G2/M cell cycle arrest. AMANTADIG treatment enhanced the expression of phosphorylated MAPK1 in 786-O cells. Secondly, we studied the expression of survivin known to be affected by cardiac glycosides and to regulate the G2/M cell phase. AMANTADIG treatment upregulated the expression of the pro-apoptotic survivin-2B variant in Caki-1 and 786-O cells. Moreover, treatment with AMANTADIG resulted in significantly lower survivin protein expression compared to 786-O control cells. Summarizing, treatment with all cardiac glycosides induced G2/M cell cycle arrest and downregulated the miR-2278 and miR-670-5p in microarray analysis. All cardiac glycosides affected the MAPK-pathway and survivin expression, both associated with the G2/M phase. Because cells in the G2/M phase are radio- and chemotherapy sensitive, cardiac glycosides like AMANTADIG could potentially improve the efficacy of radio- and/or chemotherapy in RCCs.

Clinico-pathologic relevance of Survivin splice variant expression in cancer

Survivin is a member of the inhibitor of apoptosis (IAP) family and has multifunctional properties that include aspects of proliferation, invasion and cell survival control. Survivin is a promising candidate for targeted cancer therapy as its expression is associated with poor clinical outcome, more aggressive clinico-pathologic features, and resistance to radiation and chemotherapy. In the present review the different properties of the Survivin splice variants are discussed and their activities correlated with different aspects of cancer cell biology, to include subcellular location. Special emphasis is placed on our current understanding of these Survivin splice variants influence on each other and on the phenotypic responses to therapy that they may control.

Survivin splice variants are not essential for mitotic progression or inhibition of apoptosis induced by doxorubicin and radiation

Survivin is a critical regulator of mitosis, and an inhibitor of apoptosis which is overexpressed in almost all cancers. In the current study, cell cycle profiles of normal proliferating human umbilical vein endothelial cells, prostate cancer, and lung cancer cell lines expressing varying levels of survivin and its splice variants were compared using a novel functional complementation assay. Defects in chromosome segregation and cytokinesis that were observed after depletion of endogenous survivin were not complemented by any of the survivin splice variants: survivin-2B, survivin-3B, survivin-ΔEx3, or survivin-2A when expressed exogenously at a level comparable to endogenous full-length survivin. Survivin variants were not detectable at the endogenous protein level. Cancer cells with higher levels of full-length survivin and survivin-2B expression, exhibited reduced caspase-3 activation following doxorubicin treatment and radiation. Whereas earlier studies focused on function and expression levels of survivin specific to cancer cells, the current study brings forward the essential role of survivin in normal dividing cells. Full-length survivin was found to be associated with Aurora-B kinase in the chromosomal passenger complex and depletion of survivin mimics mitotic phenotypes observed after Aurora-B kinase inhibition, in cancer as well as normal proliferating cells. Thus, our study establishes survivin as a marker of proliferation, rather than a cancer specific marker. Therefore, systemic therapeutic interventions targeting survivin will affect cancer as well as normal proliferating cells.

Change in Expression of Survivin Caused by Using Oxaliplatin in HCT116 Colon Cancer Cells

Purpose

Oxaliplatin is a third-generation platinum compound, and it has no nephrotoxicity and has reduced bone marrow toxicity. Cancer cells that are resistant to cisplatin are sensitive to oxaliplatin. Oxaliplatin is used widely for the treatment of colon cancers. Recently, oxaliplatin was reported to inhibit the expression of survivin, which protects cell apoptosis. However, there are no reports on the expressions of survivin variants and the changes in intracellular localization of survivin in cancer cells. We studied the expression of survivin caused by oxaliplatin in HCT116 colon cancer cells, and we observed the localization of survivin in the mitotic phase.

Methods

We treated the HCT116 colon cancer cells with 2.0 µM of oxaliplatin, and we studied the expressions of survivin protein, and survivin mRNA variants, as well as the changes in intracellular localization, by using the Western blot method, RT-PCR, immunocytochemistry, and flowcytometry.

Results

Oxaliplatin inhibits the expression of the survivin protein and survivin mRNA in HCT116 colon cancer cells. The expression of the survivin-2B variants, which have no antiapoptotic activity but control cell mitosis by localization on a microtubule, is reduced continuously 2 days after treatment with oxaliplatin. In immunocytochemistry, expression of survivin in the cytoplasm is reduced and especially is not expressed in microtubules and contractile rings.

Conclusion

One of the mechanisms of oxaliplatin is to inhibit the expression of and to change the localization of survivin. Based on these results, we suggest that changes in the expression of survivin variants and in their localization are two effects of oxaliplatin.