Prodigiosin-Emerged PI3K/Beclin-1-Independent Pathway Elicits Autophagic Cell Death in Doxorubicin-Sensitive and -Resistant Lung Cancer

Wei-Jun Chiu; Shian-Ren Lin; Yu-Hsin Chen; May-Jwan Tsai; Max K Leong; Ching-Feng Weng

doi:10.3390/jcm7100321

Prodigiosin-Emerged PI3K/Beclin-1-Independent Pathway Elicits Autophagic Cell Death in Doxorubicin-Sensitive and -Resistant Lung Cancer

J Clin Med. 2018 Oct 3;7(10):321. doi: 10.3390/jcm7100321.

Authors

Wei-Jun Chiu¹, Shian-Ren Lin², Yu-Hsin Chen³, May-Jwan Tsai⁴, Max K Leong^{5

6}, Ching-Feng Weng⁷

Affiliations

¹ Department of Life Science and Institute of Biotechnology, National Dong Hwa University, Hualien 97401, Taiwan. zidane538@gmail.com.
² Department of Life Science and Institute of Biotechnology, National Dong Hwa University, Hualien 97401, Taiwan. d9813003@gms.ndhu.edu.tw.
³ Department of Life Science and Institute of Biotechnology, National Dong Hwa University, Hualien 97401, Taiwan. kb5634@yahoo.com.tw.
⁴ Neural Regeneration Laboratory, Neurological Institute, Taipei Veterans General Hospital, Taipei 11217, Taiwan. mjtsai2@vghtpe.gov.tw.
⁵ Department of Life Science and Institute of Biotechnology, National Dong Hwa University, Hualien 97401, Taiwan. leong@gms.ndhu.edu.tw.
⁶ Department of Chemistry, National Dong Hwa University, Hualien 97401, Taiwan. leong@gms.ndhu.edu.tw.
⁷ Department of Life Science and Institute of Biotechnology, National Dong Hwa University, Hualien 97401, Taiwan. cfweng@gms.ndhu.edu.tw.

Abstract

Prodigiosin (PG) belongs to a family of prodiginines isolated from gram-negative bacteria. It is a water insoluble red pigment and a potent proapoptotic compound. This study elucidates the anti-tumor activity and underlying mechanism of PG in doxorubicin-sensitive (Dox-S) and doxorubicin-resistant (Dox-R) lung cancer cells. The cytotoxicity and cell death characteristics of PG in two cells were measured by MTT assay, cell cycle analysis, and apoptosis/autophagic marker analysis. Then, the potential mechanism of PG-induced cell death was evaluated through the phosphatidylinositol-4,5-bisphosphate 3-kinase-p85/Protein kinase B /mammalian target of rapamycin (PI3K-p85/Akt/mTOR) and Beclin-1/phosphatidylinositol-4,5-bisphosphate 3-kinase-Class III (Beclin-1/PI3K-Class III) signaling. Finally, in vivo efficacy was examined by intratracheal inoculation and treatment. There was similar cytotoxicity with PG in both Dox-S and Dox-R cells, where the half maximal inhibitory concentrations (IC₅₀) were all in 10 μM. Based on a non-significant increase in the sub-G₁ phase with an increase of microtubule-associated proteins 1A/1B light chain 3B-phosphatidylethanolamine conjugate (LC3-II), the cell death of both cells was categorized to achieve autophagy. Interestingly, an increase in cleaved-poly ADP ribose polymerase (cleaved-PARP) also showed the existence of an apoptosis-sensitive subpopulation. In both Dox-S and Dox-R cells, PI3K-p85/Akt/mTOR signaling pathways were reduced, which inhibited autophagy initiation. However, Beclin-1/PI3K-Class III downregulation implicated non-canonical autophagy pathways were involved in PG-induced autophagy. At completion of the PG regimen, tumors accumulated in the mice trachea and were attenuated by PG treatment, which indicated the efficacy of PG for both Dox-S and Dox-R lung cancer. All the above results concluded that PG is a potential chemotherapeutic agent for lung cancer regimens regardless of doxorubicin resistance.

Keywords: doxorubicin resistant; intratracheal inoculation; lung cancer; prodigiosin.

Grants and funding

102-2320-B-259-001-3/Ministry of Science and Technology, Taiwan