AdoMet triggers apoptosis in head and neck squamous cancer by inducing ER stress and potentiates cell sensitivity to cisplatin

Abstract

S‐Adenosyl‐l‐methionine (AdoMet) is a naturally and widely occurring sulfonium compound that plays a primary role in cell metabolism and acts as the principal methyl donor in many methylation reactions. AdoMet also exhibits antiproliferative and proapoptotic activities in different cancer cells. However, the molecular mechanisms underlying the effects exerted by AdoMet have only been partially studied. In the current study, we evaluated the antiproliferative effect of AdoMet on Cal‐33 oral and JHU‐SCC‐011 laryngeal squamous cancer cells to define the underlying mechanisms. We demonstrated that AdoMet induced apoptosis in Cal‐33 and JHU‐SCC‐011 cells, involving a caspase‐dependent mechanism paralleled by an increased Bax/Bcl‐2 ratio. Moreover, we showed, for the first time, that AdoMet induced ER‐stress in Cal‐33 cells and activated the unfolded protein response, which can be responsible for apoptosis induction through the activation of CHOP and JNK. In addition, AdoMet‐induced ER‐stress was followed by autophagy with a consistent increase in the levels of the autophagic marker LC3B‐II, which was indeed potentiated by the autophago‐lysosome inhibitor chloroquine. As both escape from apoptosis and decreased activation of JNK are mechanisms of resistance to cisplatin (cDPP), an agent usually used in cancer therapy, we have evaluated the effects of AdoMet in combination with cDPP on Cal‐33 cells. Our data showed that the combined treatment resulted in a strong synergism in inhibiting cell proliferation and in enhancing apoptosis via intrinsic mechanism. These results demonstrate that AdoMet has ER‐stress‐mediated antiproliferative activity and synergizes with cDDP on cell growth inhibition, thus providing the basis for its use in new anticancer strategies.

Effects of S‑adenosyl‑L‑methionine on the invasion and migration of head and neck squamous cancer cells and analysis of the underlying mechanisms

“…In a previous study by the authors, to the best of our knowledge, the mechanisms underlying the antitumor effect of AdoMet on HNSCC were reported for the first time, demonstrating that AdoMet was able to induce apoptosis, involving a caspase-dependent mechanism paralleled by an increased Bax/Bcl-2 ratio in Cal-33 and JHU-SCC-011 cells following 48 and 72 h of treatment, respectively (13).…”

“…In a previous study by the authors, the synergistic effect of AdoMet in association with cDDP, an agent commonly used in cancer therapy, in inhibiting Cal-33 cell proliferation and in enhancing cell apoptosis, was demonstrated (13). It was found that the optimal combination of the two drugs, highly synergistic with the CalcuSyn calculation, corresponded to 200 µM AdoMet and 0.18 µM cDDP following 72 h of treatment.…”

“…Reagents. AdoMet was obtained from New England BioLabs, Inc. and prepared as previously described (13). The Annexin V-fluorescein isothiocyanate (V-FITC) Apoptosis Detection kit was purchased from eBioscience; Thermo Fisher Scientific, Inc. Tissue culture dishes were purchased from Corning Inc.…”

“…Flow cytometry for the analysis of apoptosis. Annexin V-FITC was used in conjunction with the vital dye propidium iodide (PI) as previously described (13) to distinguish apoptotic (Annexin V-FITC-positive, PI-positive) from necrotic (Annexin V-FITC-negative, PI-positive) cells (23). The detection of viable cells, early apoptotic cells, late apoptotic cells and necrotic cells was performed using a BD Accuri™ C6 flow cytometer (BD Biosciences).…”

“…compound exerts pleiotropic effects on signal transduction in a variety of cell types and that AdoMet is able to halt the progression of several human tumors (8)(9)(10)(11)(12)(13).…”