Development of the ABEEMσπ Polarization Force Field for Base Pairs with Amino Acid Residue Complexes.

DNA damage caused by oxidized bases can lead to aging and cancer in living beings. Luckily, a repair enzyme is able to repair the oxidized bases. The key step is to accurately recognize the oxidized bases, which mainly rely on complex hydrogen bond interactions. We have calibrated the charge parameters and torsional parameters of the ABEEMσπ polarization force field (ABEEMσπ PFF) to accurately describe the intermolecular and intramolecular interactions. Taking the experiment and quantum chemical method as the benchmark, a series of properties of base pair-amino acid residue systems, DNA and DNA-protein interaction systems were calculated and compared with those of other force fields. We have done a tremendous amount of tasks in testing, calibrations, and analyses. The ABEEMσπ PFF not only explicitly gives the position and the partial charge of lone-pair electrons but also introduces a function kHB to fit special electrostatic interactions in hydrogen bond interaction regions. Therefore, it can accurately simulate the polarization effect and charge transfer of hydrogen bond interactions, especially for charged systems and sulfur-containing systems, such as the binding energy between amino acid and base pairs (24-28 kcal/mol), which is induced by charge transfer. The RMSD of ABEEMσπ PFF is 1.18 kcal/mol, whereas the RMSD of Amber OL15 is 8.21 kcal/mol. The relative positions of the amino acid residue have significantly changed, and the hydrogen bonds were broken when simulated by fixed charge force fields. In addition, owing to refitting the reasonable torsional parameters, the geometric structures optimized by ABEEMσπ PFF were well consistent with those of the M06-2X/6-311++G** method, but the simulations by fixed force fields have a large rotation of methyl and distortion of the plane of the base pair. After extensive MD simulation with four test DNAs and a DNA-protein system, we conclude that ABEEMσπ PFF shows better agreement when compared to experimental structures, which illustrates the reliability of our model and the transferability of the parameters.

Antitumor effect of recombinant human endostatin combined with cisplatin on rats with transplanted Lewis lung cancer

OBJECTIVE@#To observe the antitumor effect and mechanism of recombinant human endostatin (Endostar) injection in tumor combined with intraperitoneal injection of cisplatin on subcutaneous transplanted Lewis lung cancer in rats.@*METHODS@#A total of 30 C57 rats were selected, and the monoplast suspension of Lewis lung cancer was injected into the left axilla to prepare the subcutaneous transplanted tumor models in the axilla of right upper limb. The models were randomly divided into Groups A, B, and C. Medication was conducted when the tumor grew to 400 mm(3). Group A was the control group without any interventional treatment. Group B was injected with Endostar 5 mg kg(-1) d(-1) for 10 d. Group C was given the injection of Endostar 5 mg kg(-1) d(-1) combined with intraperitoneal injection of cisplatin 5 mg kg(-1) d(-1) for 10 d. All the rats in three groups were executed the day after the 10 d medication and the tumor was taken off for measurement of volume and mass changes and calculation of antitumor rate, after which the vascular endothelial growth factor (VEGF) concentration in rats' plasma was determined by ELISA. The tumor tissues were cut for the preparation of conventional biopsies. After hematoxylin-eosin staining, the pathologic histology was examined to observe the structures of tumor tissues, VEGF score and microvessel density (MVD) in each group.@*RESULTS@#The volume and mass of tumor in Groups B and C were significantly lower than Group A (P < 0.05) while the tumor volume and mass in Group C were significantly lower than Group B (P < 0.05). The antitumor rate in Group C was significantly higher than Group B (P < 0.05), but the tumor VEGF score, MVD and plasma VEGF level in Group C were significantly lower than Groups A and B (P < 0.05). In Group B, the tumor VEGF score, MVD and plasma VEGF level were significantly lower than Group A (P < 0.05). The microscopic image of Group C showed that its number of active tumor cells and the blood capillary around tumor was significantly smaller than that of Groups A and B, and meanwhile atrophy and liquefactive necrosis were seen in local tumor.@*CONCLUSIONS@#Endostar injection combined with intraperitoneal injection of cisplatin is effective in reducing tumor VEGF score and MVD of transplanted tumor tissues in rats with Lewis lung cancer to obstruct the nutrient supply of tumor cells and kill tumor cells, so that the inhibition of tumor cell proliferation and metastasis can be achieved with a remarkable effect.

Antitumor effect of recombinant human endostatin combined with cisplatin on rats with transplanted Lewis lung cancer

Objective: To observe the antitumor effect and mechanism of recombinant human endostatin (Endostar) injection in tumor combined with intraperitoneal injection of cisplatin on subcutaneous transplanted Lewis lung cancer in rats. Methods: A total of 30 C57 rats were selected, and the monoplast suspension of Lewis lung cancer was injected into the left axilla to prepare the subcutaneous transplanted tumor models in the axilla of right upper limb. The models were randomly divided into Groups A, B, and C. Medication was conducted when the tumor grew to 400 mm3. Group A was the control group without any interventional treatment. Group B was injected with Endostar 5 mg kg-1 d-1 for 10 d. Group C was given the injection of Endostar 5 mg kg-1 d-1 combined with intraperitoneal injection of cisplatin 5 mg kg-1 d-1 for 10 d. All the rats in three groups were executed the day after the 10 d medication and the tumor was taken off for measurement of volume and mass changes and calculation of antitumor rate, after which the vascular endothelial growth factor (VEGF) concentration in rats' plasma was determined by ELISA. The tumor tissues were cut for the preparation of conventional biopsies. After hematoxylin-eosin staining, the pathologic histology was examined to observe the structures of tumor tissues, VEGF score and microvessel density (MVD) in each group. Results: The volume and mass of tumor in Groups B and C were significantly lower than Group A (P < 0.05) while the tumor volume and mass in Group C were significantly lower than Group B (P < 0.05). The antitumor rate in Group C was significantly higher than Group B (P < 0.05), but the tumor VEGF score, MVD and plasma VEGF level in Group C were significantly lower than Groups A and B (P < 0.05). In Group B, the tumor VEGF score, MVD and plasma VEGF level were significantly lower than Group A (P < 0.05). The microscopic image of Group C showed that its number of active tumor cells and the blood capillary around tumor was significantly smaller than that of Groups A and B, and meanwhile atrophy and liquefactive necrosis were seen in local tumor. Conclusions: Endostar injection combined with intraperitoneal injection of cisplatin is effective in reducing tumor VEGF score and MVD of transplanted tumor tissues in rats with Lewis lung cancer to obstruct the nutrient supply of tumor cells and kill tumor cells, so that the inhibition of tumor cell proliferation and metastasis can be achieved with a remarkable effect.