OBJECTIVEThe overexpression of N-methylpurine DNA glycosylase (MPG) may imbalance the DNA base excision repair (BER) to sensitize tumor cells to current DNA damage chemotherapy. In an effort to improve the efficacy of cancer chemotherapy, we have constructed adenoviral vector of MPG, to study its ability to sensitize human osteosarcoma cell HOS to DNA damage agents.

METHODSThe adenoviral infection and MPG expression, as well as enzyme activity were determined by flow cytometry, Western blot, and HEX labeled oligonucleotide-based assay respectively. The cell survival/proliferation was measured using MTS, SRB, and [(3)H] thymidine incorporation assay. Apoptosis cell death was assayed by flow cytometry after treatment using phycoerythin (PE)-conjugated Annexin V and 7-amino-actinomycin (7-AAD).

RESULTSA 10 MOI of recombinant nonreplicating adenovirus was found to infect more than 90% of HOS cells within 24 hours by EGFP fluorescence, in which the MPG overexpression and MPG enzyme activity were also detected. The MPG overexpression HOS cells were significantly more sensitive to the DNA damage agents, including MMS, MNNG, and TMZ, with changes in the IC50 of 6.0, 4.5, and 2.5 fold respectively.

CONCLUSIONSThese data establish transient MPG overexpression as a potential therapeutic approach for increasing HOS cellular sensitivity to DNA damage agent chemotherapy.

Adenoviridae ; enzymology ; Antineoplastic Agents ; metabolism ; pharmacology ; Cell Line, Tumor ; DNA Glycosylases ; genetics ; metabolism ; pharmacology ; Gene Expression Regulation, Neoplastic ; Humans ; Osteosarcoma ; pathology

Osteosarcoma is the most common primary bone tumor, but the pathogenesis is not well understood. While cyclooxygeanse-2 (COX-2) is known to be closely associated with tumor growth and metastasis in several kinds of human tumors, the function of COX-2 in osteosarcoma is unclear. Therefore, to investigate the function of COX-2 in osteosarcoma, we established stable cell lines overexpressing COX-2 in U2OS human osteosarcoma cells. COX-2 overexpression as well as prostaglandin E(2) treatment promoted proliferation of U2OS cells. In addition, COX-2 overexpression enhanced mobility and invasiveness of U2OS cells, which was accompanied by increases of matrix metalloproteinase-2 and -9 (MMP-2 and -9) activities. Selective COX-2 inhibitors, NS-398 and celecoxib, inhibited cell proliferation and abrogated the enhanced mobility, invasiveness and MMP activities induced by COX-2 overexpression. These results suggest that COX-2 is directly associated with cell proliferation, migration and invasion in human osteosarcoma cells, and the therapeutic value of COX-2 inhibitors should be evaluated continuously.
Bone Neoplasms/*enzymology/pathology ; Cell Line, Tumor ; Cell Movement ; Cell Proliferation ; Cyclooxygenase 2/biosynthesis/*physiology ; Cyclooxygenase 2 Inhibitors/pharmacology ; Dinoprostone/pharmacology ; Enzyme Activation ; Humans ; Matrix Metalloproteinase 2/metabolism ; Matrix Metalloproteinase 9/metabolism ; Neoplasm Invasiveness ; Nitrobenzenes/pharmacology ; Osteosarcoma/*enzymology/pathology ; Pyrazoles/pharmacology ; Sulfonamides/pharmacology

The cajanine (longistylin A-2-carboxylic acid) is isolated and identified from extracts of Cajanus cajan L. (ECC) , which structure is similar to diethylstilbestrol. The regulation properties of the cajanine and other four extracts of Cajanus cajan L. (32-1, 35-1, 35-2, and 35-3) were tested in human osteoblast-like (HOS) TE85 cells and marrow-derived osteoclast-like cells. By using MTT assay to test the change of cell proliferation, 3H-proline incorporation to investigate the formation of collagen, and by measuring alkaline phosphatase (ALP) activity, bone formation in HOS TE85 cell was evaluated after pretreated for 48 hours. Bone marrow cells were cultured to examine the derivation of osteoclast cells (OLCs), which were stained with tartrate-resistant acid phosphatase (TRAP). The long term effect (pretreated for 18 days) on promoting mineralized bone-like tissue formation was tested by Alizarin red S staining in HOS TE85 cells. After the treatment with cajanine (1 x 10(-8) g x mL(-1)) for 48 hours, cell number increased significantly (57.7%). 3H-Proline incorporation also statistically increased (98.5%) in those cells. Significant change of ALP activity was also found (P < 0.01) in 35-1 and 35-3 treated cells (they were 66.2% and 82.4% in the concentration of 1 x 10(-8) g x mL(-1), respectively). The long term (18 days) effects of 32-1 and 35-3 on promoting mineralized bone-like tissue formation in HOS TE85 cell were obvious. There were much more red blots over the field of vision compared with that of control group. After the treatment of cajanine, derived-osteoclast cells appeared later and much less compared with control. The inhibition of cajanine was 22.8% while it was 37.9% in 32-1 treated cells in the dose of 1 x 10(-7) g x mL(-1). It is obvious that cajanine and ECCs promoted the osteoblast cells proliferation and mineralized bone-like tissue formation in HOS TE85 cells, while inhibited derivation of osteoclast cells. All of these suggested that cajanine has the estrogen-like action on osteoblast and osteoclast, which could be developed as anti-osteoporosis drugs.
Alkaline Phosphatase ; metabolism ; Animals ; Bone Marrow Cells ; cytology ; Bone Neoplasms ; metabolism ; pathology ; Cajanus ; chemistry ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; Cells, Cultured ; Collagen ; biosynthesis ; Diethylstilbestrol ; analogs & derivatives ; isolation & purification ; pharmacology ; Drugs, Chinese Herbal ; isolation & purification ; pharmacology ; Humans ; Osteoblasts ; drug effects ; Osteoclasts ; cytology ; metabolism ; Osteogenesis ; drug effects ; Osteosarcoma ; enzymology ; pathology ; Phytoestrogens ; isolation & purification ; pharmacology ; Plant Leaves ; chemistry ; Plants, Medicinal ; chemistry ; Rats ; Rats, Wistar