Identification of Fangchinoline as a novel autophagy inhibitor with an adjuvant of chemotherapy against lung cancer.

Autophagy is a fundamental recycling pathway that enhances cellular resilience, promoting survival. However, this survival mechanism can impede anti-cancer treatment strategies designed to induce cell death. In this study, we identified a novel autophagy inhibitor, Fangchinoline (Fan) isolated from the traditional Chinese medicine Stephania tetrandra. We speculated that when Fan blocks autophagy, cancer cells lose substantial self-preservation abilities during treatment. Firstly, we examined in detail the mechanism through which Fan inhibits autophagy. Specifically, Fan induced a significant increase in autophagosomes, as indicated by GFP-LC3 labeling, confirmed by the up-regulation of LC3-II. The autophagy receptor protein p62 was also up-regulated, suggesting a potential inhibition of autophagy flux. We further ruled out the possibility of fusion barriers between lysosomes and autophagosomes, as confirmed by their co-localization in double fluorescence staining. However, the lysosomal acid environment might be compromised, as suggested by the diminished fluorescence of acidity-sensitive dyes in the lysosomes and the corresponding decrease in mature forms of lysosomal cathepsin. To test the anti-cancer potential of Fan, we combined it with Cisplatin (Cis) or Paclitaxel (PTX) for lung cancer cell treatment. This combined treatment demonstrated a synergistically enhanced killing effect. These promising anti-tumor results were also replicated in a xenografted tumor model. The significance of this research lies in the identification of Fan as a potent autophagy inhibitor and its potential to enhance the efficacy of existing anti-cancer drugs. By unraveling the mechanisms of Fan's action on autophagy and demonstrating its synergistic effect in combination therapies, our study provides valuable insights for developing novel strategies to overcome autophagy-mediated resistance in cancer treatment.

Tubeimoside I-induced lung cancer cell death and the underlying crosstalk between lysosomes and mitochondria.

Cancer cells have developed chemoresistance and have improved their survival through the upregulation of autophagic mechanisms that protect mitochondrial function. Here, we report that the traditional Chinese anticancer agent tubeimoside I (Tub), which is a potent inhibitor of autophagy, can promote mitochondria-associated apoptosis in lung cancer cells. We found that Tub disrupted both mitochondrial and lysosomal pathways. One of its mechanisms was the induction of DRP1-mediated mitochondrial fragmentation. Another mechanism was the blocking of late-stage autophagic flux via impairment of lysosomal acidification through V-ATPase inhibition; this blocks the removal of dysfunctional mitochondria and results in reactive oxygen species (ROS) accumulation. Excessive ROS accumulation causes damage to lysosomal membranes and increases lysosomal membrane permeability, which leads to the leakage of cathepsin B. Finally, cathepsin B upregulates Bax-mediated mitochondrial outer membrane permeability and, subsequently, cytosolic cytochrome C-mediated caspase-dependent apoptosis. Thus, the cancer cell killing effect of Tub is enhanced through the formation of a positive feedback loop. The killing effect of Tub on lung cancer cells was verified in xenografted mice. In summary, Tub exerts a dual anticancer effect that involves the disruption of mitochondrial and lysosomal pathways and their interaction and, thereby, has a specific and enhanced killing effect on lung cancer cells.

Tanshinone IIA arrests cell cycle and induces apoptosis in 786-O human renal cell carcinoma cells.

Tanshinone IIA (Tan IIA), isolated from the Chinese medicinal herb Danshen, has been reported to have anticancer effects in several tumor models, while its effects on renal cell carcinoma have not been studied. In the present study, we evaluated the effects of Tan IIA on growth inhibition and apoptosis in the renal cancer cell line 786-O and its mechanism of action. Results of the MTT assay indicated that the treatment of 786-O cells with Tan IIA resulted in a concentration-dependent decrease in cell viability. Flow cytometry analysis revealed that Tan IIA treatment caused apoptosis following cell cycle perturbation. Furthermore, we examined the expression of cell cycle and apoptosis-related proteins using immunoblotting, which indicated an upregulation of p53, p21, bax and caspase-3 in Tan IIA-treated cells compared with Tan IIA-untreated cells. These results suggest that the activation of p53 and the upregulation of its target genes, including p21 and bax, may be involved in the mitochondrial apoptosis induced by Tan IIA in 786-O cells.