Involvement of Autophagy in Antitumor Activity of Folate-appended Methyl-β-cyclodextrin

Abstract

Autophagy, the major lysosomal pathway for recycling intracellular components including organelles, is emerging as a key process regulating tumorigenesis and cancer therapy. Most recently, we newly synthesized folate-appended methyl-β-cyclodextrin (FA-M-β-CyD), and demonstrated the potential of FA-M-β-CyD as a new antitumor drug. In this study, we investigated whether anticancer activity of FA-M-β-CyD in folate receptor-α (FR-α)-positive tumor cells is involved in autophagy. In contrast to methyl-β-cyclodextrin (M-β-CyD), FA-M-β-CyD entered KB cells (FR-α (+)) through CLIC/GEEC endocytosis. No significant depression in the DNA content was observed in KB cells after treatment with FA-M-β-CyD. Additionally, the transmembrane potential of mitochondria after treatment with FA-M-β-CyD was drastically elevated. Meanwhile, FA-M-β-CyD induced the formation of autophagic vacuoles, which were partially colocalized with mitochondria, in KB cells. Taken together, these results suggest that FR-α-expressing cell-selective cytotoxic activity of FA-M-β-CyD could be mediated by the regulation of autophagy, rather than the induction of apoptosis.

Induction of mitophagy-mediated antitumor activity with folate-appended methyl-β-cyclodextrin

“…In addition, FA-M-β-CyD elicited the formation of autophagic vacuoles. 16 Taken together, these results indicate that FR-α-expressing cell-selective cytotoxic activity of FA-M-β-CyD could be mediated by the regulation of autophagy, rather than the induction of apoptosis. However, the mechanism of autophagy induction by FA-M-β-CyD remains unclear.…”

“…16 However, in the previous study, the autophagosomes were just detected by Cyto-ID, a LC-3 detector in cells. Meanwhile, in this study, we used Mtphagy Dye, a mitophagy-specific detection kit commercialized most recently by Dojindo Molecular Technologies, Inc., namely, Mtphagy Dye, which accumulates in intact mitochondria, is immobilized …”

“…[14][15][16] FA-M-β-CyD entered KB cells (FR-α (+)) through the clathrin-independent carriers/glycosylphosphatidylinositolenriched endocytic compartments (CLIC/GEEC). 16 Notably, FA-M-β-CyD did not induce depression in DNA content and drastically elevated the transmembrane potential of mitochondria in KB cells (FR-α (+)). In addition, FA-M-β-CyD elicited the formation of autophagic vacuoles.…”

Potential Use of Cyclodextrins as Drug Carriers and Active Pharmaceutical Ingredients

“…Most interestingly, FA-M-β-CyD inducted autophagy-mediated antitumor effect, not apoptosis. 68) These data suggest that FA-M-β-CyD has potential as a unique antitumor API.…”

Evaluation of Antitumor Effects of Folate-Conjugated Methyl-β-cyclodextrin in Melanoma

“…35) Previously, we reported that FA-M-β-CyD induced autophagic cell death in KB cells, rather than apoptotic cell death. 36) However, it is still obscure whether FA-M-β-CyD induces autophagy in melanoma cells. Therefore, we next examined whether autophagosome formation in Ihara cells is elicited by FA-M-β-CyD, using Cyto-ID ® Autophagy Detection Kit, which detects autophagic vacuoles in cells.…”