Andrographolide sensitizes cisplatin-induced apoptosis via suppression of autophagosome-lysosome fusion in human cancer cells

Abstract

Suppression of autophagy has been increasingly recognized as a novel cancer therapeutic approach. Andrographolide (Andro), a diterpenoid lactone isolated from an herbal plant Andrographis paniculata, is known to possess anti-inflammatory and anticancer activity. In this study, we sought to examine the effect of Andro on autophagy, and to evaluate whether such effect is relevant to the sensitization effect of Andro on apoptosis induced by DNA damage agents in cancer cells. First, we found that Andro is able to significantly enhance autophagic markers in various cancer cell lines, including GFP-LC3 puncta and LC3-II level. Interestingly, Andro treatment also led to marked increase of p62 protein level and addition of chloroquine (CQ) failed to further enhance either LC3-II or p62 level, indicating that Andro is likely to suppress autophagic flux at the maturation and degradation stage. Next, we provided evidence that Andro inhibits autophagosome maturation not by affecting the lysosomal function, but by impairing autophagosome-lysosome fusion. Lastly, we demonstrated that treatment with cisplatin, a DNA damage agent, induces autophagy in cancer cells. Importantly, Andro is capable of sensitizing cisplatin-induced cell killing determined with both short-term apoptosis assays and long-term clonogenic test, via suppression of autophagy, a process independent of p53. In summary, these observations collectively suggest that Andro could be a promising anti-cancer agent in combination therapy via its potent inhibitory effect on autophagy by disrupting autophagosome-lysosome fusion.

Autophagy activated by tuberin/mTOR/p70S6K suppression is a protective mechanism against local anaesthetics neurotoxicity

“…Similarly, the percentages of autolysosomes in total formed autophagosomes (autophagosome + autolysosomes) were increased by LAs administration. Consistently, the levels of p62, a marker of autophagosome clearance 8, 31, were significantly decreased by treatment with LAs, respectively, compared with untreated controls ( P < 0.01) (Fig. 2B).…”

“…Autophagy is an evolutionarily conserved process which sequesters cytoplasmic materials for lysosome‐dependent degradation 7, 8, 9. Under normal conditions, autophagy is important for maintaining cellular homeostasis by turning over damaged materials 10.…”

Activation of lysosomal function in the course of autophagy via mTORC1 suppression and autophagosome-lysosome fusion

“…Fluorescence intensities of 10 000 cells per sample were measured by flow cytometry using the FACS cytometer (BD Biosciences). Second, we used a cell lysate-based assay that has already been established in our laboratory [57,58]. Briefly, cells were lysed in M2 buffer and the lysate and then incubated with 50 μM of the fluorogenic cathepsin B/L substrate (Z-RR-AMC or Ac-HRYR-ACC, respectively) in 100 μl …”

Inhibition of autophagosome-lysosome fusion by ginsenoside Ro via the ESR2-NCF1-ROS pathway sensitizes esophageal cancer cells to 5-fluorouracil-induced cell death via the CHEK1-mediated DNA damage checkpoint

“…[39][40][41][42] Besides, esophageal cancer patients exhibit a higher level of autophagy. 43 Therefore, we tested the role of autophagy in 5-Fu-mediated cell death.…”

“…Consequently, suppression of autophagy has been increasingly recognized as a novel cancer therapeutic approach to induce autophagy-associated cell death or sensitize tumor cells to clinical drug-mediated cell death 40,[62][63][64]. However, very limited information is currently available regarding the detailed mechanisms linking autophagic flux inhibition to cell death.…”