CST1 and breast carcinoma: In SW480 colon cancer and MDA-MB-231 breast cancer cells, CST1 knockdown using the pLenti expression system containing a short hairpin RNA (shRNA) for CST1 (shCST1; Figure 1a) induced striking morphologic changes, including an enlarged nucleus and flattened cytoplasm, and increased SA-β-gal activity compared with pLenti-mock control cells (Figure 1b, upper panels).