Independent [Ca2+]i increases and cell proliferation induced by the carcinogen safrole in human oral cancer cells

Jong Khing Huang, Chun Jen Huang, Wei Chuan Chen, Shiuh Inn Liu, Shu Shong Hsu, Hong Tai Chang, Li Ling Tseng, Chiang Ting Chou, Chih Hung Chang, Chung Ren Jan*

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

25 Scopus citations


The effect of the carcinogen safrole on intracellular Ca2+ movement and cell proliferation has not been explored previously. The present study examined whether safrole could alter Ca2+ handling and growth in human oral cancer OC2 cells. Cytosolic free Ca2+ levels ([Ca 2+]i) in populations of cells were measured using fura-2 as a fluorescent Ca2+ probe. Safrole at a concentration of 325 μM started to increase [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was reduced by 40% by removing extracellular Ca2+, and was decreased by 39% by nifedipine but not by verapamil or diltiazem. In Ca2+-free medium, after pretreatment with 650 μM safrole, 1 μM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor) barely induced a [Ca2+]i rise; in contrast, addition of safrole after thapsigargin treatment induced a small [Ca 2+]i rise. Neither inhibition of phospholipase C with 2 μM U73122 nor modulation of protein kinase C activity affected safrole-induced Ca2+ release. Overnight incubation with 1 μM safrole did not alter cell proliferation, but incubation with 10-1000 μM safrole increased cell proliferation by 60±10%. This increase was not reversed by pre-chelating Ca2+ with 10 μM of the Ca2+ chelator BAPTA. Collectively, the data suggest that in human oral cancer cells, safrole induced a [Ca2+]i rise by causing release of stored Ca2+ from the endoplasmic reticulum in a phospholipase C- and protein kinase C-independent fashion and by inducing Ca2+ influx via nifedipine-sensitive Ca2+ entry. Furthermore, safrole can enhance cell growth in a Ca2+-independent manner.

Original languageEnglish
Pages (from-to)88-94
Number of pages7
JournalNaunyn-Schmiedeberg's Archives of Pharmacology
Issue number1
StatePublished - 07 2005
Externally publishedYes


  • Ca
  • Fura-2
  • OC2 cells
  • Oral cancer
  • Proliferation
  • Safrole


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