The c-myc apoptotic response is not intrinsic to blocking terminal myeloid differentiation

It has previously been shown that deregulated c-myc blocks terminal myeloid differentiation and prematurely recruits both the Type I and II CD95/Fas apoptotic pathways, promoting an incompletely penetrant apoptotic response. In this work it is shown that deregulated expression of either mycER or mycER (TM) variants also blocked terminal myeloid differentiation but failed to induce the apoptotic response, demonstrating that c-myc can block differentiation independent of the apoptotic response. The failure of the mycER (TM) transgene to cause the apoptotic response is associated with reduced levels of RIP I expression, increased Mcl-I expression and activation of both NF-kappa B and Akt. In addition, deregulating expression of RIPI in MImycER (TM) cells restored the apoptotic response. Thus altering c-Myc or its downstream effectors can influence the balance between apoptosis and survival, and ultimately the oncogenic potential of the c-myc oncogene. This knowledge can be exploited to manipulate the downstream effectors, such as RIP1, to promote apoptosis and drive the death of cancer cells.