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Autophagy. 2014 May;10(5):736-49. doi: 10.4161/auto.28034. Epub 2014 Feb 14.

The natural compound oblongifolin C inhibits autophagic flux and enhances antitumor efficacy of nutrient deprivation.

Author information

1
School of Pharmacy; Shanghai University of Traditional Chinese Medicine; Shanghai, China.
2
Key Lab in Healthy Science and Technology; Division of Life Science; Graduate School at Shenzhen; Tsinghua University; Shenzhen,China; School of Life Sciences; Tsinghua University; Beijing, China.
3
Department of Pathology; Ruikang Hospital Affiliated to Guangxi University of Chinese Medicine; Nanning, China.
4
School of Pharmacy; Shanghai University of Traditional Chinese Medicine; Shanghai, China; Department of Discovery Technologies; Roche R&D Center (China) Ltd; Shanghai, China.
5
Key Lab in Healthy Science and Technology; Division of Life Science; Graduate School at Shenzhen; Tsinghua University; Shenzhen,China.

Abstract

Metabolic stress induces autophagy as an alternative source of energy and metabolites. Insufficient autophagy in nutrient-deprived cancer cells would be beneficial for cancer therapy. Here, we performed a functional screen in search of novel autophagy regulators from natural products. We showed that oblongifolin C (OC), a natural small molecule compound extracted from Garcinia yunnanensis Hu, is a potent autophagic flux inhibitor. Exposure to OC results in an increased number of autophagosomes and impaired degradation of SQSTM1/p62. Costaining of GFP-LC3B with LysoTracker Red or LAMP1 antibody demonstrates that autophagosome-lysosome fusion is blocked by OC treatment. Furthermore, OC inhibits lysosomal proteolytic activity by altering lysosomal acidification and downregulating the expression of lysosomal cathepsins. Importantly, OC can eliminate the tolerance of cancer cells to nutrient starvation. Starvation dramatically increases the susceptibility of cancer cells to OC-induced CASP3-dependent apoptosis in vitro. Subsequent studies in xenograft mouse model showed that OC has anticancer potency as revealed by increased staining of cleaved CASP3, LC3 puncta, and SQSTM1, as well as reduced expression of lysosomal cathepsins. Combined treatment with OC and caloric restriction potentiates anticancer efficacy of OC in vivo. Collectively, these data demonstrated that OC is a novel autophagic flux inhibitor and might be useful in anticancer therapy.

KEYWORDS:

apoptosis; autophagy; cancer; lysosome; natural product; oblongifolin C

PMID:
24642486
PMCID:
PMC5119057
DOI:
10.4161/auto.28034
[Indexed for MEDLINE]
Free PMC Article

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