SP1 and plasma cell myeloma: The results of TF silencing herein obtained differ from those previously reported for HeLa cervical cancer cells, where YY1 regulates the basal UBC expression [15] and HSF1 drives the transcriptional induction of the UBC gene after proteotoxic and oxidative stress [16,21], while SP1 plays a role in the basal UBC expression [14,17], besides being involved in the glucocorticoid-mediated transcriptional induction of the UBC gene, in muscle and multiple myeloma cells [17,18].