Anti-Tumor Effect of Controlled Drug Delivery Figure 3. Antitumor activity of SAHA-DDP/PECE in vivo. In the mice model of oral squamous cell carcinoma xenografts, the female nude mice received 2 6 106 HSC-3 cells via subcutaneously into the right flank regions. (A) The mice were then treated with NS, PECE, SAHA, DDP, SAHA-DDP and SAHA-DDP/PECE every two weeks for a total of two doses starting on day 7 (n = 6 mice per group). Tumor volumes of mice from different groups of HSC-3 tumor model. (B) Representative tumors of OSCC mice model from NS, PECE, SAHA, DDP and SAHA-DDP control group and SAHA-DDP/PECE treated mice. Data are representative of at least two separate experiments. Bars, means 6 SD (*P,0.05).(C) When tumors were palpable, the mice were randomly assigned to two independent treatment groups( n = 12 mice per group): mice treated with 100 ml combine SAHA with DDP (SAHA- DDP), or treated with 100 ml SAHA and DDP in thermosensitive hydrogel (SAHA-DDP/PECE). At the date of 1, 3, 7, 14 and 21 three mice were sacrificed separately. The ribonucleoprotein of the tumor tissues was extracted and the expression of acetyl-Histone H3 and Histone H3 was detected by western blot. doi:10.1371/journal.pone.0033860.g003 differentiation, and apoptosis [33]. It did this by silencing some tumor suppressor genes, as well as other genes that are responsible for cell cycle progression, cell proliferation, programmed cell death, and differentiation. Thus, blocking histone deacetylation may allow the body to block this tumor growth and prevent progression. We have reported that low concentrations of SAHA synergized with DDP in combination therapy to induce a level of cytotoxicity and apoptosis in both Tca8113 and KB cell lines greater than that mediated by either agent alone, or that predicted by an additive model [32]. Previously, some researchers also have reported that the combination of SAHA with DDP possessed synergistic cytotoxicity against the other human cancer cells [34–38]. SAHA mediated the cleavage and activation of the pro-apoptotic Bcl-2 family member Bid. Furthermore, diverse apoptosis-associated proteins, including p53, cytochrome C and caspase-3 were involved in the induction of apoptosis. Their results suggest that concurrent treatment with SAHA enhances tumor cell sensitivity to subtoxic doses of DDP. Though this may be regarded as a novel strategy for treatment of cancer, it has not been detected in vivo. Nevertheless, further studies including generating OSCC xeno- graft mouse model should be conducted to confirm the in vitro results. To design a better combinative chemotherapeutic regimen in vivo, there should be a better focus on cell killing and lower systemic toxicity. The selection of vectors always played an important role in the succession of chemotherapy protocol. And strategies such as sustained and localized therapy may have the potential to improve the efficacy of medical treatment. A kind of biodegradable and injectable poly (ethylene glycol)-poly (‘‘-caprolactone)-poly (ethylene glycol) (PEG-PCL-PEG, PECE) triblock copolymer, can be used as a delivery vector to load chemotherapeutic drugs for intratumoral infusion chemotherapy. PECE hydrogel we have prepared in this study would be an ideal controlled drug delivery system for SAHA and DDP. As our previously study, a hydrogel solution (30 wt%, 0.5 mL) was subcutaneously injected into KunMing mice. After day 1, day 3, day 7, and day 14 following subcutaneous injection, and the opaque gel maintained its integrity in the period of observation. The size of gel decreased during degradation, and at day 14, the gel almost disappeared.Therefore, PECE hydrogel we have prepared in this study could sustain more than 14 days in situ [39,40]. It was a free-flowing sol at room temperature or below critical gelation temperature became gel at body temperature. This sol-gel transition behavior of PECE hydrogel gives the advantage of simply mixing it with pharmaceutical agents at low temperature in which it then becomes an in situ gel-forming controlled drug delivery system in PLoS ONE | www.plosone.org 5 April 2012 | Volume 7 | Issue 4 | e33860