Diterpene 16-Hydroxycleroda-3,13-dien-15,16-olide Emerges Non-Canonical Autophagic Cell Death in Doxorubicin-Resistant Lung Cancer

Background: The antitumor activity of HCD has been reported in numerous types of cancers. Moreover, the antitumor of HCD could also be applied in non-small-cell lung cancer (NSCLC) cells and further act on doxorubicin-resistant (Dox-R) of NSCLC cells. The underlying anti-cancer mechanism of HCD on Dox-R versus Dox-sensitive (Dox-S) of A549 cells was under this investigation. Methods: Cytotoxicity of HCD against two cell lines (Dox-S and Dox-R) were determined via MTT assay, flow cytometry, and Western blot; and further examination of its anti-cancer efficacy in A549-bearing xenograft mice via orthotopic intratrachea (IT) inoculation. Result: Regardless sensitive and resistant to Dox, HCD could arrest both Dox-S and Dox-R cells at G 2 /M phase without altering the sub-G 1 cycle along with increasing cleaved-PARP. HCD downregulated the mTOR/Akt/PI3K-p85 and PI 3 K-ClassIII/Beclin-1 and upregulated p62/LC3-I/II expressions, further confirmed the cell autophagy after HCD-induced. Morphological observations of the mouse lung sections illustrated that fewer cancer cells accumulated around the trachea while there were less neoplastic activities found in HCD orthotopic treatment mice without liver, kidney and spleen toxicity. Conclusion: HCD exhibited the chemotherapeutic potential for lung cancer in Dox-resistant cells, suggesting natural autophagic inducer HCD provides a promising clue of new drug discovery and development for lung cancer therapy.