Immunomodulatory Protein from Ganoderma microsporum Induces Pro-Death Autophagy through Akt-mTOR-p70S6K Pathway Inhibition in Multidrug Resistant Lung Cancer Cells.

Abstract

Chemoresistance in cancer therapy is an unfavorable prognostic factor in non-small cell lung cancer (NSCLC). Elevation of intracellular calcium level in multidrug resistant (MDR) sublines leads to sensitization of MDR sublines to cell death. We demonstrated that a fungal protein from Ganoderma microsporum, GMI, elevates the intracellular calcium level and reduces the growth of MDR subline via autophagy and apoptosis, regardless of p-glycoprotein (P-gp) overexpression, in mice xenograft tumors. In addition, we examined the roles of autophagy in the death of MDR A549 lung cancer sublines by GMI, thapsigargin (TG) and tunicamycin (TM) in vitro. Cytotoxicity of TG was inhibited by overexpressed P-gp. However, TM-induced death of MDR sublines was independent of P-gp level. Combinations of TG and TM with either docetaxel or vincristine showed no additional cytotoxic effects on MDR sublines. TG- and TM-mediated apoptosis of MDR sublines was demonstrated on Annexin-V assay and Western blot and repressed by pan-caspase inhibitor (Z-VAD-FMK). Treatment of MDR sublines with TG and TM also augmented autophagy with accumulation of LC3-II proteins, breakdown of p62 and formation of acidic vesicular organelles (AVOs). Inhibition of ATG5 by shRNA silencing significantly reduced autophagy and cell death but not apoptosis following TG or TM treatment. GMI treatment inhibited the phosphorylation of Akt/S473 and p70S6K/T389. Interestingly, the phosphorylation of ERK was not associated with GMI-induced autophagy. We conclude that autophagy plays a pro-death role in acquired MDR and upregulation of autophagy by GMI via Akt/mTOR inhibition provides a potential strategy for overcoming MDR in the treatment of lung cancers.

• Authors: Ling-Yen Chiu, Ming-E Hu, Tsung-Ying Yang, I-Lun Hsin, Jiunn-Liang Ko, Kan-Jen Tsai, Gwo-Tarng Sheu
• Journal: PloS one (PLoS One) Vol. 10 Issue 5 Pg. e0125774 ( 2015) ISSN: 1932-6203 [Electronic] United States
• PMID: 25946033 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• ATG5 protein, human
• ATP Binding Cassette Transporter, Subfamily B, Member 1
• Amino Acid Chloromethyl Ketones
• Antineoplastic Agents
• Autophagy-Related Protein 5
• Fungal Proteins
• Microtubule-Associated Proteins
• RNA, Small Interfering
• Taxoids
• benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone
• Tunicamycin
• Docetaxel
• Vincristine
• Thapsigargin
• MTOR protein, human
• Proto-Oncogene Proteins c-akt
• Ribosomal Protein S6 Kinases, 70-kDa
• TOR Serine-Threonine Kinases

Topics

• ATP Binding Cassette Transporter, Subfamily B, Member 1 (metabolism)
• Amino Acid Chloromethyl Ketones (pharmacology)
• Animals
• Antineoplastic Agents (therapeutic use)
• Apoptosis (drug effects)
• Autophagy (drug effects)
• Autophagy-Related Protein 5
• Carcinoma, Non-Small-Cell Lung (drug therapy)
• Cell Line, Tumor
• Docetaxel
• Drug Resistance, Multiple
• Drug Resistance, Neoplasm
• Fungal Proteins (therapeutic use)
• Ganoderma
• Humans
• Lung Neoplasms (drug therapy)
• Male
• Medicine, Chinese Traditional
• Mice
• Mice, Inbred NOD
• Microtubule-Associated Proteins (genetics)
• Proto-Oncogene Proteins c-akt (antagonists & inhibitors)
• RNA Interference
• RNA, Small Interfering
• Ribosomal Protein S6 Kinases, 70-kDa (antagonists & inhibitors)
• TOR Serine-Threonine Kinases (antagonists & inhibitors)
• Taxoids (therapeutic use)
• Thapsigargin (therapeutic use)
• Tunicamycin (therapeutic use)
• Vincristine (therapeutic use)
• Xenograft Model Antitumor Assays