HSPA1A and leukemia: MCL1 is often overexpressed in malignant cells, particularly in leukemia where the NOXA/MCL1 ratio determines sensitivity to chemotherapy and BH3-memitic drugs.22 NOXA expression can be increased transcriptionally through p53-dependent and -independent mechanisms and also by regulating protein turnover.6 NOXA has a very short half-life (~30 min) and is degraded by the proteasome; however, its turnover is not entirely dependent upon ubiquitination.8 The rate of NOXA protein turnover could be affected by hyperthermia and influenced by the presence of HSP70.