S‐Adenosylmethionine Affects ERK1/2 and Stat3 Pathways and Induces Apotosis in Osteosarcoma Cells

Abstract

Osteosarcoma is a very aggressive bone tumor. Its clinical outcome remains discouraging despite intensive surgery, radiotherapy, and chemotherapy. Thus, novel therapeutic approaches are demanded. S-Adenosylmethionine (AdoMet) is a naturally occurring molecule that is synthesized in our body by methionine adenosyltransferase isoenzymes and is also available as a nutritional supplement. AdoMet is the principal methyl donor in numerous methylation reactions and is involved in many biological functions. Interestingly, AdoMet has been shown to exert antiproliferative action in various cancer cells. However, the underlying molecular mechanisms are just starting to be studied. Here, we investigated the effects of AdoMet on the proliferation of osteosarcoma U2OS cells and the underlying mechanisms. We carried out direct cell number counting, MTT and flow cytometry-based assays, and immunoblotting experiments in response to AdoMet treatment. We found that AdoMet strongly inhibits proliferation of U2OS cells by slowing-down cell cycle progression and by inducing apoptosis. We also report that AdoMet consistently causes an increase of p53 and p21 cell-cycle inhibitor, a decrease of cyclin A and cyclin E protein levels, and a marked increase of pro-apoptotic Bax/Bcl-2 ratio, with caspase-3 activation and PARP cleavage. Moreover, the AdoMet-induced antiproliferative effects were dynamically accompanied by profound changes in ERK1/2 and STAT3 protein and phosphorylation levels. Altogether, our data enforce the evidence of AdoMet acting as a biomolecule with antiproliferative action in osteosarcoma cells, capable of down-regulating ERK1/2 and STAT3 pathways leading to cell cycle inhibition and apoptosis, and provide a rationale for the possible use of AdoMet in osteosarcoma therapy.

S‐Adenosylmethionine‐mediated apoptosis is potentiated by autophagy inhibition induced by chloroquine in human breast cancer cells

“…In our experimental model, AdoMet induced cell cycle arrest at the G 2 /M transition by down‐regulating the expression of cyclin B and by increasing the expression of p53 and cell cycle‐inhibitors p21 and p27. Interestingly we have recently demonstrated that AdoMet induced cell‐cycle arrest at G 2 /M phase and activation of apoptosis in U2OS osteosarcoma cells (Ilisso et al, ). Moreover, our research group has also reported that AdoMet potentiates the antitumor effect of doxorubicin by inducing the extrinsic pathway of apoptosis through the activation of the death receptor FAS in breast cancer cell line CG5 (Ilisso et al, ).…”

“…Moreover, because of its peculiar biological and pharmacological properties, AdoMet is an approved nutritional supplement. Recent in vitro and in vivo studies highlighted the effects of AdoMet on cancer progression by regulating key cellular processes, such as proliferation, differentiation, cell cycle, and apoptosis (Ilisso et al, ; Li et al, ; Lu & Mato, , ; Luo et al, ; Martínez‐López et al, ; Parashar et al, ; Pakneshan et al, ). The interest on AdoMet was recently focused on its epigenetic regulating activity of genes involved in the regulation of cancer cell growth.…”

“…In fact, AdoMet is able to reverse the DNA hypomethylation status of both c‐Myc and H‐ras promoters, thus down regulating their expression in human gastric and colon cancer (Luo et al, ). Despite in recent years growing evidence has accumulated in the literature on the anti‐proliferative, anti‐metastatic, and proapoptotic effects of AdoMet in cancer cells (Ilisso et al, ; Li et al, ; Lu & Mato, , ; Martínez‐López et al, ; Pakneshan et al, ; Parashar et al, ; Shukeir et al, ), a clear understanding of the complex biological mechanisms exerted by AdoMet as well as their possible clinical applications are far to be defined.…”

“…We found that AdoMet strongly inhibits proliferation of U2OS cells by both reducing cell cycle progression and inducing apoptosis via caspase‐3 activation and poly (ADP ribose) polymerase (PARP) cleavage. Moreover, the AdoMet‐induced antiproliferative effects were dynamically paralleled by down‐regulation of ERK and STAT3 pathways (Ilisso et al, ).…”

GADD45β induction by S-adenosylmethionine inhibits hepatocellular carcinoma cell proliferation during acute ischemia-hypoxia

“…S-adenosylmethionine (SAMe) is an essential compound in many metabolic pathways, serving as a methyl donor and a precursor for polyamines and glutathione (GSH) [10]. Most patients with liver injury or a chronic liver disease, like cirrhosis, have impaired SAMe biosynthesis due to reduced MAT1A expression and MAT I/III inactivation, which are respectively the enzyme and isoenzyme involved in SAMe synthesis in normal hepatocytes [11, 12].…”