The proteosomal degradation pathway. The pathway in (a) MCF-7 and (b) in ZR75-1 cells. MCF-7 cells had a higher gene usage and selected genes which encode for the ATPase subunit proteins in the 19S regulator (PSMC1, PSMC5, PSMC6), versus no change in ZR75-1 cells. PSMA7 (alpha subunit, 20S catalytic core) was the only common gene with an identical fold change. The histone family member protein encoding gene, H2FZ was up-regulated in ZR75-1 cells.