5-Aminolevulinic acid enhances cell death under thermal stress in certain cancer cell lines.

Taku Chibazakura, Yui Toriyabe, Hiroshi Fujii, Kiwamu Takahashi, Mariko Kawakami, Haruna Kuwamura, Hazuki Haga, Shun-ichiro Ogura, Fuminori Abe, Motowo Nakajima, Hirofumi Yoshikawa, Tohru Tanaka

Index: Biosci. Biotechnol. Biochem. 79(3) , 422-31, (2015)

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Abstract

5-aminolevulinic acid (5-ALA) is contained in all organisms and a starting substrate for heme biosynthesis. Since administration of 5-ALA specifically leads cancer cells to accumulate protoporphyrin IX (PpIX), a potent photosensitizer, we tested if 5-ALA also serves as a thermosensitizer. 5-ALA enhanced heat-induced cell death of cancer cell lines such as HepG2, Caco-2, and Kato III, but not other cancer cell lines including U2-OS and normal cell lines including WI-38. Those 5-ALA-sensitive cancer cells, but neither U2-OS nor WI-38, accumulated intracellular PpIX and exhibited an increased reactive oxygen species (ROS) generation under thermal stress with 5-ALA treatment. In addition, blocking the PpIX-exporting transporter ABCG2 in U2-OS and WI-38 cells enhanced their cell death under thermal stress with 5-ALA. Finally, a ROS scavenger compromised the cell death enhancement by 5-ALA. These suggest that 5-ALA can sensitize certain cancer cells, but not normal cells, to thermal stress via accumulation of PpIX and increase of ROS generation.