Effects of MYC Inhibitors on the Growth of Acute Leukaemia Cells

MYC proto-oncogene bHLH transcription factor (MYC) proteins function as transcription factors by binding to MYC-associated factor X (MAX) proteins and are involved in various cancer growth, including leukaemia. This study aimed to examine the effects of synthetic MYC inhibitors, which block the MYC-MAX complex formation, in in vitro human acute leukaemia cell lines.Four cell lines, OCI/AML2 derived from acute myeloid leukaemia, NALM-6 from B-lymphoblastic leukaemia, and KOPT-K1 and Jurkat from notch receptor 1 (NOTCH1)-mutated T-lymphoblastic leukaemia (T-ALL), were treated with the small-molecule MYC inhibitors 10058-F4 and MYCi975. The expression of cell proliferation and signalling proteins was studied.These inhibitors suppressed the growth of leukaemia cell lines. Treatment with the two inhibitors down-regulated the protein expression of c-MYC, MAX, and activating enhancer-binding protein 4 (AP4) in all cell lines. Up-regulation of p27 and p21 was observed only in 10058-F4-treated OCI/AML2 cells and MYCi975-treated KOPT-K1 cells. These two inhibitors down-regulated the expression of NOTCH1, cleaved NOTCH1, and hes family bHLH transcription factor 1 (HES1) in both T-ALL cell lines.MYC inhibitors appear to be novel molecular-targeted drugs against acute leukaemia, including NOTCH1-mutated T-ALL. However, it is necessary to elucidate the precise molecular mechanisms of these effects before clinical use.