An alternatively spliced survivin variant is positively regulated by p53 and sensitizes leukemia cells to chemotherapy

Abstract

Survivin is a unique member of the inhibitor of apoptosis protein family, and its expression is regulated by p53. Recent identification of several functionally divergent survivin variants augments the complexity of survivin action as well as its regulation. Here we report that survivin-2B (retaining a part of intron 2 as a cryptic exon) is positively regulated by p53, and its overexpression plays a role in sensitizing leukemia cells to chemotherapeutic drug doxorubicin. Doxorubicin treatment activated p53, downregulated survivin and survivin-DEx3 but upregulated survivin-2B in EU-3, an acute lymphocytic leukemia (ALL) cell line with wild-type (wt)-p53 phenotype. In contrast, doxorubicin treatment failed to induce these alterations in EU-6 cells, a mutant-p53 ALL cell line. To specify the role of wt-p53 in regulating survivin and its variants, a temperature-sensitive p53 mutant plasmid p53-143 was transfected into EU-4, a p53-null ALL cell line, to establish a subline EU-4/p53-143. When EU-4/p53-143 cell culture was shifted from 37.5 C to the wt-p53-permissive temperature (32.5 C), the expression of survivin and survivin-DEx3 was decreased whereas survivin-2B expression was increased, confirming the distinct regulatory effect of p53 on survivin and its variants. To clarify the role of survivin-2B in the process of apoptosis, survivin-2B cDNA was cloned into pcDNA3HA vector and transfected into EU-4 cells. Enforced expression of survivin-2B in EU-4 cells inhibited cell growth and sensitized these cells to doxorubicin-induced apoptosis. These results suggest that survivin-2B variant is a proapoptotic factor and its expression is upregulated by p53.

Association of p53 gene alterations with the expression of antiapoptotic survivin splice variants in breast cancer

“…Our results are consistent with Zhu et al (2004) study, reporting in leukaemia cell lines that antiapoptotic survivin and survivin-DEx3 are downregulated by wt-p53, whereas proapoptotic survivin-2B is upregulated. However, no correlation was found for survivin-2B and survivin-2a with p53 gene status in our study.…”

“…Indeed, experimental studies have shown that survivin-2B reduced cell survival frequencies comparatively to survivin (Mahotka et al, 1999), but survivin-2a seems to strongly attenuate the antiapoptotic activity of survivin even in the absence of an apoptotic stimulus (Caldas et al, 2005). Survivin expression regulation is still unknown, but many studies indicate that p53 might have a major role in this regulation (Hoffman et al, 2002;Mirza et al, 2002;Lohr et al, 2003;Punga and Akusjarvi, 2003;Zhu et al, 2004). It was also shown that p53 has also an effect on different gene expression at the mRNA splicing levels (Maxwell et al, 1999;Moyret-Lalle et al, 2001;Xu and el-Gewely, 2003), including splicing of survivin (Zhu et al, 2004).…”

Role of survivin and its splice variants in tumorigenesis

“…These observations suggest that the expression of these survivin variants could be differentially regulated. Consistent with this notion, recent studies from Zhu et al (2004) showed that one of the mechanisms for p53 to induce apoptosis in ALL cells is through differential modulation of survivin and its variants. Doxorubicinactivated p53 upregulated survivin-2B but downregulated survivin and survivin-DEx3.…”

The survivin -31 snp in human colorectal cancer correlates with survivin splice variant expression and improved overall survival

“…Regarding the better studied −31G/C snp, this finding may suggest that repression through binding to the CDE/CHR element gains importance as a control mechanism of survivin expression in cancer, since other mechanisms involved in the regulation of survivin expression such as APC and P53 are often inactivated in neoplasia due to mutations [37,38]. In agreement with the findings of Gazouli et al we also showed a significantly higher frequency of the C allele in CRC patients compared to healthy controls suggesting a role of the −31G/C snp in colorectal carcinogenesis [8].…”