Abstract
Neurofibromatosis type 1 (NF1) is one of the most common hereditary neurocutaneous disorders. In addition to skin pigmentation and cutaneous neurofibroma, some patients developed the plexiform neurofibroma since birth. Plexiform neurofibroma has abundant Schwann cells, fibroblasts, mast cells, blood vessels, and connective tissues, which increases the risk of developing a malignant peripheral nerve sheath tumor (MPNST). MPNST is a highly invasive cancer with no effective therapeutic agent. Cordycepin or 3'-deoxyadenosine is an extract from cordyceps militaris, which has been reported as an anti-inflammation and anti-tumor agent. Herein, we evaluated cordycepin's anti-proliferative effect on MPNST cell lines both in vitro and in vivo. Cordycepin inhibited the MPNST cell growth with an arrest of cell cycle at G2/M and S phases. The administration of naringin and pentostatin, inhibitors for adenosine deaminase (ADA), enzyme responsible for cordycepin degradation, did not show a synergistic effect in MPNST cells treated with cordycepin. However, the combined treatment enhanced the decrease of tumors in xenograft mouse model. Immunoblotting showed a decreased level of p53 protein in all MPNST cell lines, but S462TY cells. After cordycepin treatment, the levels of ERK, survivin, pAKT, and Sp1 proteins also decreased. The level of tubulin, but not actin or GAPDH, decreased in a dose-dependent manner. The microtubule network which is composed of tubulins was markedly decomposed in those treated MPNST cells. To elucidate the epigenetic control of transcription, ChIP-qPCR assay of the Sp1 and tubulin promoter regions revealed decreased Sp1 binding. The incorporation of 3'-doexyadenosine is detrimental for the process of poly(A) tail elongation. The poly(A) tail length assay showed the tail length in Sp1 and tubulin transcripts decreased in the treated cells. Nevertheless, the administration of SP1 protein to the treated cells could not rescue them completely. Furthermore, the p53-knocked-down cells (S462TY) where the expression of both p53 and Sp1 was suppressed, were vulnerable to cordycepin. The p53 protein could ameliorate the effect. In summary, cordycepin is effective to inhibit the growth of MPNST, probably through the pathway of p53/Sp1/tubulin.