Cytotoxicity of two new ribosome‐inactivating proteins, cinnamomin and camphorin, to carcinoma cells

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Abstract
Cinnamomin (two-chain) and camphorin (single-chain), two novel ribosome-inactivating proteins (RIPs) purified from the seeds of Cinnamomum camphora, produced inhibitory effects in cultured carcinoma cells. The IC50 of cinnamomin to the human hepatocarcinoma cell-line 7721 and the melanoma cell-line M21 were 18·8 nmol and 11·7 nmol respectively. The IC50 of camphorin to the human hepatocarcinoma cell-line 7721 was 59 nmol, whereas the melanoma cell-line M21 was not susceptible to camphorin. Furthermore, cinnamomin exhibited a remarkable inhibitory effect on the growth of solid melanoma in the skin of the nude mouse. An R-fragment could be isolated from ribosomes of cinnamomin- or camphorin-treated carcinoma cells after incubation with acidic aniline, indicating that the cytotoxicity of these two new RIPs to carcinoma cells might result from modification to the ribosomes.
Funding Information
  • National Science Foundation of China, Academia Sinica