Cancer stem cells are known to be involved in oral carcinogenesis, effective chemo-preventive drug may work through targeting these cells and corresponding signaling pathways. The primary objective was to evaluate the role of cancer stem cells in the chemo-preventive efficacy of Curcumin and Metformin. The animal model was established using 4-6 weeks C57Bl/6 mice (N=60); the mice were divided into two arms; i) Control Arm (N=10) administered with plain drinking water and ii) Treatment Arm (N=50). The treatment arm was administered with 4NQO (4-nitroquinoline-oxide) in drinking water (50ppm) for a period of 17 weeks. The mice were then taken off the carcinogen and administered the drugs in drinking water. The mice (N=45) were divided into four arms; i) Arm I (N=15) with plain water, ii) Arm II (N=15) with Curcumin (64μg/ml), Arm III (N=15) with Metformin (5mg/ml) and iv) Arm IV (N=15) with a combination of both Curcumin and Metformin. The mice were dissected at 17th week (N=5) as well as at the end of the study period and the samples collected for molecular analysis of stem cell related pathways

Histopathology carried out at 17th week, showed dysplastic changes after which the animals were administered with the drugs. The average tumor volume (mm3) was reduced in the combination arm (0.693+0.034) and the individual arms (Curcumin=2.54; Metformin=1.45+0.33) as compared to the 4NQO arm (6.65+2.37). The average number of lesions per mice was also reduced in the combination arm (Avg=0.375+0.17) and the Curcumin arm (Avg=0.25+0.22) as compared to the 4NQO arm (Avg=0.6+0.22). The overall survival of the combination arm was better when compared to individual treatment (p=0.0006). Immunohistochemical studies using NF-κB showed a down-regulated expression in the combination arm as compared to the control arm with a corresponding down-regulation of the stem cell markers, CD44 and Notch1. In vitro treatment of primary cells, generated from the mice tissues, with Curcumin (100µM), Metformin (10µM) and combination treatment confirmed down regulation of CSC markers (CD44, Notch1, Jagged, STAT3) in the treated cells. The effect on the Cancer stem cell is being further confirmed by various functional assays (Migration, colony formation and Colony survival assays) currently been carried out in the lab. The clinical results suggest that the combination arm is more efficient in chemoprevention, while the initial molecular analysis suggest that the stem cell cache might be reduced in parallel. Further studies using the molecular markers for Metformin drug and subsequent functional studies are currently ongoing. Expression profiling studies using molecular markers corresponding to other stem cell related pathways (CD44, Notch1, Jagged1 and STAT3) are also ongoing.