Transcription factors STAT3 and MYC mediate human platelet lysate-induced cell proliferation

Background

Human platelet lysate (HPL) has emerged as an efficient cytokine and growth factor providing medium supplement, replacing fetal bovine serum (FBS) for ex vivo clinical cell expansion. As growth promoting effects of HPL may be based on intracellular mechanisms, we hypothesized a specific influence on cell cycle target gene expression and aimed to identify the main molecular key players.

Methods

Cell cycle target gene expression of bone marrow-, umbilical cord- and white adipose tissue-derived stromal cells cultured in HPL- or FBS-supplemented media was compared using RT-qPCR and a cell cycle specific antibody array. As HPL is rich in growth factors that are ligands of tyrosine kinase receptor (TKR) pathways, we applied TKR inhibitors and analyzed cell proliferation. Additionally, genome profiling, RT-qPCR and Western blotting were used to identify downstream mediators of HPL-derived growth signals.

Results

RT-qPCR as well as cell cycle specific antibody array revealed significant upregulation of cell cycle genes in stromal cells cultured in HPL. Blocking specific TKR pathways lead to significantly reduced cell proliferation. In response to HPL we could detect an enhanced expression of the transcription factors signal transducer and activator of transcription 3 (STAT3) and MYC, both known as TKR downstream effectors and stimulators of cell proliferation. Furthermore, specific inhibition of STAT3 resulted in a significant reduction of HPL-induced cell proliferation and cell cycle gene expression.

Conclusion

Based on our results we suppose that HPL-promoted cell proliferation is induced by enhanced TKR signaling and thus elevated expression of the TKR downstream effectors STAT3 and MYC. The enhanced expression of STAT3 and MYC might in turn stimulate the expression of cell cycle promoting target genes.

Offenlegung Interessenkonflikt:

The authors declare no conflict of interest.