Expression of survivin and its splice variants survivin-2B and survivin-ΔEx3 in breast cancer

Alternative splicing of survivin mRNA gives rise to multiple isoforms, that is, survivin and 3 splice variants, survivin-2B, survivin-3B and survivin-ΔEx3. The aim of this study was to compare the expression of survivin, survivin-2B and survivin-ΔEx3 in normal breast tissue, fibroadenomas, primary breast cancer and axillary nodal metastases. Survivin, survivin-2B and survivin-ΔEx3 mRNA were measured using semiquantitative RT–PCR. In the primary carcinomas, we related mRNA for each form of survivin to both survivin protein and apoptosis. For each type of breast tissue, survivin was the predominant form detected, being present in 146 out of 156 (93.6%) primary breast carcinomas, 11 out of 11 (100%) axillary nodal metastases, 21 out of 31 (67.7%) fibroadenomas and five out of 22 (22.7%) specimens of normal breast tissue. Levels of the three forms of survivin were significantly higher in the carcinomas compared to normal breast tissue (P<0.0001). Levels of both survivin-2B and survivin-ΔEx3 but not survivin were significantly higher in nodal metastases than primary carcinomas. Survivin mRNA levels correlated significantly with survivin protein. Finally, both survivin and survivin-ΔEx3 but not survivin-2B correlated positively with apoptosis. Although survivin, survivin-2B and survivin-ΔEx3 were all detected in both malignant and nonmalignant breast tissue, the predominant form was survivin. Our results suggest that the different forms of survivin may have different roles in apoptosis in breast cancer.