Figure 2.

Transcriptional upregulation of endogenous GrB in RB-reconstituted MDA-MB-468 breast carcinoma cells. RPA and Northern blotting analyses were performed on RNAs extracted from parental MDA-MB-468 (pRB⁻) and a representative Tc-regulated RB-reconstituted clone at each indicated day. (+Tc) medium containing 0.5 μg ml⁻¹ of Tc; (−Tc) Tc-free medium. An RNA sample from PBL of healthy donors cultured in the presence of 50 U ml⁻¹ of IL-2 was included in the Northern blot as GrB-positive control. Note that Endo-GrB mRNAs are slightly larger than the Lym-GrB mRNA on the Northern blot. The numbers under the blots indicate the fold increases in Endo-GrB transcription. Similar results were obtained with three independent clones of RB-reconstituted MDA-MB-468 breast carcinoma cells (data not shown).