Hemostatic gelatin sponge is a superior matrix to matrigel for establishment of LNCaP human prostate cancer in nude mice

Polyethylenimine-alginate nanocomposites based bone morphogenetic protein 2 gene-activated matrix for alveolar bone regeneration

The repair and treatment of lost or damaged alveolar bone is of great significance in dentistry. Gene-activated matrix (GAM) technology provides a new way for bone regeneration. It is a local gene delivery system, which can not only recruit cells, but also influence their fate. For this purpose, we fabricated a bone morphogenetic protein 2 (BMP-2) gene-loaded absorbable gelatin sponge (AGS) and studied its effect on promoting alveolar bone formation and preventing resorption following tooth extraction in rats. In order to obtain better transfection efficiency, polyethylenimine-alginate (PEI-al) nanocomposites were synthesized and used as gene vectors to deliver BMP-2 cDNA plasmids (PEI-al/pBMP-2). The transfection efficiency, BMP-2 protein expression and osteogenic differentiation of the cells were investigated in vitro. In vivo, we established an alveolar bone regeneration model by extracting the rats' left mandibular incisors. The rats were randomly assigned into 3 groups: control group, unfilled sockets; AGS group, sockets filled with PEI-al solution-loaded gelatin sponges; AGS/BMP group, sockets filled with PEI-al/pBMP-2 solution-loaded gelatin sponge. Radiological and histological assays were performed at 4 and 8 weeks later. In vitro transfection assays indicated that PEI-al/pBMP-2 complexes could effectively transfect MC3T3-E1 cells, promoting the secretion of BMP-2 protein for at least 14 days, as well as increasing the expression of osteogenesis-related gene, ALP activity and calcium deposition. In vivo, western blot analysis showed BMP-2 protein was expressed in bone tissues of AGS/BMP group. The relative height of the residual alveolar ridge and bone mineral density (BMD) of the AGS/BMP group were significantly greater than those in the AGS and control groups at 4 and 8 weeks, respectively. Histological examination showed that, at 4 weeks, osteoblasts had grown in a cubic shape around the new bone in the AGS/BMP group, suggesting new bone formation. In conclusion, the combination of PEI-al/pBMP-2 complexes and gelatin sponge could promote alveolar bone regeneration, which may provide an easy and valuable method for alveolar ridge preservation and augmentation.

Polyethylenimine-alginate nanocomposites based bone morphogenetic protein 2 gene-activated matrix may provide an easy and valuable method for alveolar ridge regeneration.

Construction of orthotopic xenograft mouse models for human pancreatic cancer

Animal models are indispensable for the study of tumorigenesis and the development of anti-cancer drugs for human pancreatic cancer. In the present study, two orthotopic xenograft mouse models were developed. AsPC-1 human pancreatic cancer cells were stably labeled with red fluorescent protein (RFP) and injected subcutaneously into nude mice. For the orthotopic tumor mass model, the formed subcutaneous tumors were cut into blocks and implanted into the pancreas of nude mice via laparotomy. For the Matrigel™ tumor block model, solidified Matrigel containing RFP-labeled AsPC-1 cells was cut into blocks and implanted into the pancreas of nude mice. A subcutaneous tumor xenograft model was used as a control. Tumor growth and metastasis were assessed using an in vivo fluorescence imaging system. Thirty-six days after implantation, all mice from the two orthotopic xenograft models (n=20 per group) and 55% of the subcutaneous xenograft mice (n=20) developed tumors. The tumor growth rate was significantly higher in the orthotopic models than that in the subcutaneous model (P<0.01). Metastasis to organs such as the liver was observed in the orthotopic tumor models. Histological examination showed that the tumors were poorly differentiated adenocarcinomas. In conclusion, two orthotopic xenograft mouse models of human pancreatic cancer were established; these exhibited greater tumor growth and metastasis than the subcutaneous xenograft mouse model.

Antitumor effects of a novel small molecule targeting PCNA chromatin association in prostate cancer

Proliferating cell nuclear antigen (PCNA) plays an essential role in DNA replication and repair. Tumor cells express high levels of PCNA, identifying it as a potentially ideal target for cancer therapy. Previously, we identified nine compounds termed PCNA inhibitors (PCNA-Is) that bind directly to PCNA, stabilize PCNA trimer structure, reduce chromatin-associated PCNA, and selectively inhibit tumor cell growth. Of these compounds, PCNA-I1 is most potent. The purposes of this study were to further investigate the effects of targeting PCNA chromatin association on DNA damage and cytotoxicity and to evaluate the therapeutic potential of PCNA-I1 against tumors in mice. Given the important roles of tumor suppressor p53 in regulating sensitivity of tumor cells to chemotherapeutics, we performed studies in two human prostate cancer cell lines differing in p53 expression: LNCaP cells (wild-type p53) and PC-3 cells (p53-null). PCNA-I1 induced DNA damage and apoptosis in both LNCaP and PC-3 cells and enhanced DNA damage and apoptosis triggered by cisplatin. PCNA-I1 also induced autophagy in PC-3 cells. A short-term pretreatment with PCNA-I1 reduced colony formation by 50% in both cell lines. These data suggest that, unlike many other cytotoxic drugs, the effects of PCNA-I1 on tumor cells do not depend on expression of p53. Intravenous administrations of PCNA-I1 significantly retarded growth of LNCaP tumors of in nude mice without causing detectable effects on mouse body weight and hematology profiles. These data provide proof of concept that targeting PCNA chromatin association could be a novel and effective therapeutic approach for treatment of cancer.