科研之友
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摘要
Protective interactions with bystander cells in micro-environmental niches, such as lymph nodes (LNs), contribute to survival and therapy resistance of chronic lymphocytic leukemia (CLL) cells. This is caused by a shift in expression of B-cell lymphoma 2 (BCL-2) family members. Pro-survival proteins B-cell lymphoma-extra large (BCL-XL), BCL-2-related protein A1 (BFL-1) and myeloid leukemia cell differentiation protein 1 (MCL-1) are upregulated by LN-residing T cells through CD40L interaction, presumably via nuclear factor (NF)-kappa B signaling. Macrophages (M phi s) also reside in the LN, and are assumed to provide important supportive functions for CLL cells. However, if and how M phi s are able to induce survival is incompletely known. We first established that M phi s induced survival because of an exclusive upregulation of MCL-1. Next, we investigated the mechanism underlying MCL-1 induction by M phi s in comparison with CD40L. Genome-wide expression profiling of in vitro M phi-and CD40L-stimulated CLL cells indicated activation of the phosphoinositide 3-kinase (PI3K)-V-Akt murine thymoma viral oncogene homolog (AKT)-mammalian target of rapamycin (mTOR) pathway, which was confirmed in ex vivo CLL LN material. Inhibition of PI3K-AKT-mTOR signaling abrogated MCL-1 upregulation and survival by M phi s, as well as CD40 stimulation. MCL-1 can be regulated at multiple levels, and we established that AKT leads to increased MCL-1 translation, but does not affect MCL-1 transcription or protein stabilization. Furthermore, among M phi-secreted factors that could activate AKT, we found that induction of MCL-1 and survival critically depended on C-C motif chemokine receptor-1 (CCR1). In conclusion, this study indicates that two distinct micro-environmental factors, CD40L and M phi s, signal via CCR1 to induce AKT activation resulting in translational stabilization of MCL-1, and hence can contribute to CLL cell survival.
- 出版日期2017-6-29
