Impacts of autophagy-inducing ingredient of areca nut on tumor cells

PLoS One. 2015 May 27;10(5):e0128011. doi: 10.1371/journal.pone.0128011. eCollection 2015.

Abstract

Areca nut (AN) is a popular carcinogen used by about 0.6-1.2 billion people worldwide. Although AN contains apoptosis-inducing ingredients, we previously demonstrated that both AN extract (ANE) and its 30-100 kDa fraction (ANE 30-100K) predominantly induce autophagic cell death in both normal and malignant cells. In this study, we further explored the action mechanism of ANE 30-100K-induced autophagy (AIA) in Jurkat T lymphocytes and carcinoma cell lines including OECM-1 (mouth), CE81T/VGH (esophagus), SCC25 (tongue), and SCC-15 (tongue). The results showed that chemical- and small hairpin RNA (shRNA)-mediated inhibition of AMP-activated protein kinase (AMPK) resulted in the attenuation of AIA in Jurkat T but not in OECM-1 cells. Knockdown of Atg5 and Beclin 1 expressions ameliorated AIA in OECM-1/CE81T/VGH/Jurkat T and OECM-1/SCC25/SCC-15, respectively. Furthermore, ANE 30-100K could activate caspase-3 after inhibition of Beclin 1 expression in OECM-1/SCC25/SCC15 cells. Meanwhile, AMPK was demonstrated to be the upstream activator of the extracellular-regulated kinase (ERK) in Jurkat T cells, and inhibition of MEK attenuated AIA in Jurkat T/OECM-1/CE81T/VGH cells. Finally, we also found that multiple myeloma RPMI8226, lymphoma U937, and SCC15 cells survived from long-term non-cytotoxic ANE 30-100K treatment exhibited stronger resistance against serum deprivation through upregulated autophagy. Collectively, our studies indicate that Beclin-1 and Atg5 but not AMPK are commonly required for AIA, and MEK/ERK pathway is involved in AIA. Meanwhile, it is also suggested that long-term AN usage might increase the resistance of survived tumor cells against serum-limited conditions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • AMP-Activated Protein Kinases / metabolism
  • Apoptosis / drug effects
  • Apoptosis Regulatory Proteins / metabolism
  • Areca / chemistry*
  • Autophagy / drug effects*
  • Autophagy-Related Protein 5
  • Beclin-1
  • Caspase 3 / metabolism
  • Cell Line, Tumor
  • Humans
  • Jurkat Cells
  • MAP Kinase Signaling System / drug effects
  • Membrane Proteins / metabolism
  • Microtubule-Associated Proteins / metabolism
  • Mouth / drug effects
  • Mouth / metabolism
  • Mouth Neoplasms / drug therapy*
  • Mouth Neoplasms / metabolism
  • Nuts / chemistry*
  • Plant Extracts / chemistry*
  • Plant Extracts / pharmacology*
  • U937 Cells
  • Up-Regulation / drug effects

Substances

  • ATG5 protein, human
  • Apoptosis Regulatory Proteins
  • Autophagy-Related Protein 5
  • BECN1 protein, human
  • Beclin-1
  • Membrane Proteins
  • Microtubule-Associated Proteins
  • Plant Extracts
  • AMP-Activated Protein Kinases
  • Caspase 3

Grants and funding

This study is supported by grants from Ministry of Science and Technology (previously named: National Science Council) (NSC98-2314-B384-002-MY3, NSC98-2314-B041-002, NSC99-2314-B-041-002, NSC101-2320-B-366-001, and NSC102-2314-B-041-001-MY3), Chi Mei Medical Center (CMFHR9903, CMFHR9936, CMFHR9948, CMFHR10051, CMFHR10055, CMFHR10159, CMFHR10203, CMFHR10209, CMFHR10307, and CMFHR10301), and Chi Mei Hospital (CLFHR10107 and CLFHR10223). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.