Tubeimoside 1 Acts as a Chemotherapeutic Synergist via Stimulating Macropinocytosis
Authors: Linlin Jing
Xuegang Sun
Ruibo Sun
Liang Zhao
Weili Han
Zhuowei Gao
Xianling Gong
Xueqing Yao
Yawei Liu
Journal: Frontiers in Pharmacology (2018)
Discipline: PHARMACOLOGY & TOXICOLOGY
Keywords: chemotherapeutic synergist; endocytosis; macropinocytosis; methuosis; tubeimoside 1.
Affiliations: The Key Laboratory of Molecular Biology, State Administration of Traditional Chinese Medicine, School of Traditional Chinese Medicine, Southern Medical University, Guangzhou, China., School of Pharmacy, Guangdong Medical University, Dongguan, China., Shunde Hospital, Southern Medical University, Foshan, China., School of Public Health, Guangzhou, China., Nanfang Hospital, Southern Medical University, Guangzhou, China., School of Basic Medical Sciences, Southern Medical University, Guangzhou, China., Traditional Chinese Medicine Integrated Hospital, Southern Medical University, Guangzhou, China.

Abstract:  Macropinocytosis is a highly conserved endocytic process which characterizes the engulfment of extracellular fluid and its contents into cells via large, heterogeneous vacuoles known as macropinosomes. Tubeimoside-1 (TBM1) is a low toxic triterpenoid saponin extracted from a traditional Chinese herb Bolbostemma paniculatum (Maxim.). TBM1 stimulates a quick accumulation of numerous phase-lucent cytoplasmic vacuoles in multiple colorectal cancer (CRC) cell lines. These vacuoles can be termed as macropinosomes that efficiently engulf lucifer yellow. These vesicles are not overlaps with endocytic organelle tracers, such as ERTracker, LysoTracker and mitoTracker. These vacuoles induced by TBM1 partially incorporate into lysosomes. Transmission electron microscope indicates membrane ruffling to form lamellipodia. Protrusions collapse onto and then fuse back with the plasma membrane to generate these large endocytic vacuoles. Notably, TBM1 efficiently trafficks dextrans into heterotopic xenografts in vivo, thus provide consolidated evidence that the vacuolization can be mainly defined as macropinocytosis. TBM1 downregulates cell viability and increases PI-positive, but not highlighted Hoechst 33342-positive cells. TBM1 induced cell death can be ascribed as methuosis by hyperstimulation of macropinocytosis which can be compromised by amiloride derivative 5-(Nethyl-N-isopropyl). Light chain 3 II is recruited to these vesicles to stimulate macropinocytosis. The cell death and vacuoles can be significantly neutralized by chloroquine, but can not be the inhibited by 3-methyladenine. TBM1 can coordinate with 5-FU to exert toxicity reducing and efficacy enhancing effects in vivo by increasing the uptake of the latter without hepatic injury. In conclusion, TBM1 effectively induces in vitro and in vivo macropinocytosis which can traffick small molecules into CRC cells. It is an attractive drug transporter and can be harnessed as a chemotherapeutic synergist with translational potential. 

Retracted: No

PubPeer comments:
 Figure 6D. Image duplication. ![file] , 
 We have checked the original Data. We should honestly acknowledge that the image was misused for our negligence. We make an mistake in selecting the image to prepare the FIgure. We will contact the Journal to correct it if possible. I have no motive to make these errors intentionally. I will regret for my carelessness. Thank you for your help. ,