[Role of 8-allyl Garcinol in the Chemoprevention of Oral Squamous Cell Carcinoma].

Objective To evaluate the chemopreventive effects of 8-allyl garcinol on oral squamous cell carcinoma(OSCC).Methods OSCC cell line CAL27 were cultured and treated with different concentrations of garcinol or 8-allyl garcinol. Their effects on the biological behaviors of OSCC cell line CAL27 were measured by MTT assay,clony formation assay,scratch migration assay,and flow cytometry with Annexin V-FITC/PI staining assay. We established DMBA-induced hamster cheek pouch models of dysplasia. While the negative control group was not treated,the positive group was treated with 0.5% DMBA solution tropically to the left cheek pouch three times per week for three consecutive weeks. The other four groups received 0.5 mmol/L or 1.0 mmol/L garcinol or 8-allyl garcinol respectively three times within the following two weeks after DMBA treatment. Hamsters were sacrificed at the fifth week to obtain tissue samples of the left cheek pouch. The samples were examined by histopathology and BrdU immunohistochemisty.Results MTT assay showed that both garcinol and 8-allyl garcinol inhibited the proliferation of CAL27 cells in a concentration-and time-dependent manner. The half maximal inhibitory concentration(IC)of 8-allyl garcinol[(13.13±2.55)μmol/L] was significantly lower than garcinol[(32.20±3.24)μmol/L;t=8.008,P=0.001]. Comparing the two grougs of medicine in the same concentration,the inhibiting proliferation effects 8-allyl garcinol had significantly stronger effect in inhibiting proliferation than garcinol when the same dose was applied,and the difference was largest at the concentrations of 10(24 h:t=8.012,P=0.001;48 h:t=5.939,P=0.001;72 h:t=12.551,P=0.001)and 20 μmol/L(24 h:t=8.887,P=0.001;48 h:t=9.324,P=0.002;72 h:t=5.361,P=0.002). The clone formation assay showed the clone formation rates after the treatment with 20 μmol/L garcinol and 20 μmol/L 8-allyl garcinol were(44.1±0.4)% and(23.6±0.6)%,respectively,which were significantly lower than those after treatment with 10 μmol/L garcinol[(55.6±2.8)%;t=6.894,P=0.019] and 10 μmol/L 8-allyl garcinol[(31.0±0.6)%;t=15.556,P=0.001]. The inhibiting effects of 8-allyl garcinol at the concentrations of 10 μmol/L(t=14.682,P=0.003)and 20 μmol/L(t=51.514,P=0.001)were significantly stronger than garcinol.Scratch test showed the relative cell migration rates after treatment with 10 and 20 μmol/L garcinol for 12 hours were(16.00±4.55)%(t=3.139,P=0.026)and(3.00±3.16)%(t=6.608,P=0.001),respectively,which were lower than negative control [(30.33±7.64)%]. The relative cell migration rates after treatment with 10 and 20 μmol/L 8-allyl garcinol for 12 hours were(16.25±3.86)%(t=3.245,P=0.023)and(6.00±2.65)%(t=5.214,P=0.006),respectively,which were also lower than negative control[(30.33±7.64)%]. In addition,the relative cell migration rates after treatment with 10 and 20 μmol/L garcinol for 24 hours were(23.75±4.57)%(t=4.718,P=0.005)and(5.75±1.50)%(t=10.432,P=0.001),respectively,which were lower than negative control[(45.33±7.64)%]. The relative cell migration rates after treatment with 10 and 20 μmol/L 8-allyl garcinol for 24 hours were(23.50±2.38)%(t=5.529,P=0.003)and(11.67±2.31)%(t=7.308,P=0.002),respectively,which were also lower than negative control[(45.33±7.64)%]. Furthermore,the relative cell migration rate after treatment with 20 μmol/L garcinol for 24 hours was significantly lower than after treatment with 8-allyl garcinol(t=4.151,P=0.009). The apoptosis experiments showed that the early apoptosis rate of CAL27 cells was(5.00±0.10)% after treatment with 10 μmol/L garcinol,which was significantly higher than negative control[(1.57±0.21)%;F=70.950,P=0.001]. The early and late apoptosis rates of CAL27 cells were(5.90±0.78)%(t=39.384,P=0.001)and(9.73±1.67)%(t=10.101,P=0.001),respectively,after treatment with 20 μmol/L garcinol,which were also significantly higher than negative control. The early apoptosis rate of CAL27 cells was(4.63±1.16)% after treatment with 8-allyl garcinol,which was significantly higher than negative control(t=4.511,P=0.041). The effects of 8-allyl garcinol in promoting cell apoptosis were weaker than garcinol(10 μmol/L:t=5.982,P=0.004;20 μmol/L:t=8.578,P=0.001). The histopathological test also showed that the hyperplastic areas of oral mucosal epithelium in hamsters after treatment with 0.5 mmol/L garcinol(t=2.546,P=0.031),0.5 mmol/L 8-allyl garcinol(t=3.485,P=0.008),1.0 mmol/L garcinol(t=4.556,P=0.001),and 1.0 mmol/L 8-allyl garcinol(t=5.393,P=0.001)were significantly smaller than positive control. The dysplasia areas of oral mucosal epithelium in hamsters after treatment with 0.5 mmol/L 8-allyl garcinol(t=2.130,P=0.046),1.0 mmol/L garcinol(t=3.434,P=0.010),and 1.0 mmol/L 8-allyl garcinol(t=4.518,P=0.004)were also smaller than positive control;1.0 mmol/L garcinol group(t=2.793,P=0.023)and 1.0 mmol/L 8-allyl garcinol group(t=4.997,P=0.001)were smaller than 0.5 mmol/L garcinol treatment group. Immunohistochemical staining of BrdU showed that the BrdU-labeled indicators were significantly lower in negative control group(t=7.563,P=0.001),0.5 mmol/L garcinol(t=2.862,P=0.029),0.5 mmol/L 8-allyl garcinol(t=4.693,P=0.002),1.0 mmol/L garcinol(t=5.071,P=0.002),and 1.0 mmol/L 8-allyl garcinol(t=5.133,P=0.001)when compared with the positive control. The BrdU-labeled indicators in 0.5 mmol/L 8-allyl garcinol(t=3.724,P=0.007),1.0 mmol/L garcinol(t=7.000,P=0.001),and 1.0 mmol/L 8-allyl garcinol(t=4.413,P=0.003)were also significantly lower than in 0.5 mmol/L garcinol group.Conclusions 8-allyl garcinol could inhibit the proliferation and migration of OSCC cell line CAL27 and promotes apoptosis. It also has prominent inhibitory effects on DMBA-induced hamster cheek pouch dysplasia. However,the specific effects are slightly different from garcinol.