Upregulation of survivin during immortalization of nontransformed human fibroblasts transduced with telomerase reverse transcriptase

Abstract

These investigations demonstrate that expression of the inhibitor of apoptosis family member, survivin, is dramatically increased during immortalization of nontransformed human fibroblasts that were transduced with telomerase reverse transcriptase (hTERT). Expression of survivin in immortalized fibroblasts peaked during G 2 /M phase of the cell cycle. However, the upregulation of survivin was dissociated from the rate of proliferation and proportion of G 2 /M cells. Depletion of survivin from immortal fibroblasts increased sensitivity to stress-induced apoptosis and resulted in an accumulation of cells with 4N DNA content. Conversely, overexpression of survivin in mortal fibroblasts conferred resistance to apoptosis. In contrast, very low levels of survivin in proliferating parental fibroblasts had no bearing on sensitivity to apoptosis. The upregulation of survivin did not appear to be a direct consequence of hTERT transduction. However, repression of hTERT resulted in the rapid downregulation of survivin in telomerase-immortalized fibroblasts and tumor cell lines, but not in cells immortalized via an Alternative Lengthening of Telomeres mechanism. These results have important therapeutic implications, as telomerase and survivin are both broadly expressed in human cancers. Selection during the immortalization process for cells expressing high levels of survivin may account for the abundance of survivin in diverse tumor types.

RuvBl2 cooperates with Ets2 to transcriptionally regulate hTERT in colon cancer

“…To isolate proteins implicated in the regulation of telomerase, isogenic cell lines, JFCF-6G (6G) and JFCF-1-3C (1-3C) were used which were telomerase-positive and telomerase-negative, respectively [38]. To maintain their telomeres in the absence of telomerase, cells utilise the ALT mechanism of which a standard characteristic is the presence of relatively heterogeneous telomere lengths [39,40].…”

Expression of Human Telomerase Reverse Transcriptase in Vulvar Intraepithelial Neoplasia and Squamous Cell Carcinoma: An Immunohistochemical Study With Survivin and p53

“…The expression levels of survivin were positively related to those of hTERT in non-small cell lung carcinomas. 18 Yuan et al 19 found that repression of hTERT resulted in the rapid down-regulation of survivin in telomerase-immortalized fibroblasts and tumor cell lines, but not in cells immortalized via an alternative lengthening of telomeres mechanism. The authors concluded that these observations have important therapeutic implications, as telomerase and survivin are both broadly expressed in human cancers.…”

Up-regulation of Survivin during Immortalization of Human Myofibroblasts Is Linked to Repression of Tumor Suppressor p16INK4a Protein and Confers Resistance to Oxidative Stress

“…Transductions were performed using Phoenix A packaging cells according to our published method (28). The design and validation of siRNA targeting survivin (S1) and control oligonucleotide (Sc) were also published previously (23). Cells were transfected with 100 nM siRNA using Lipofectamine TM RNAiMAX reagent (Invitrogen) according to the protocol of the manufacturer.…”

“…INK4a and survivin mRNA were as described previously (23,34). ␤2-microglobin mRNA was used as a normalization control.…”

“…, the inhibitor of apoptosis protein family member survivin is up-regulated during immortalization of human MRC5 and WI38 myofibroblasts (23). The up-regulation of survivin during immortalization poses a likely explanation for the abundance of survivin in virtually all cancers (24).…”