Development of RAFT derived polymer coatings to prevent medical device related infections

The use of medical devices can be associated with serious clinical complications due to device-related infections. Over the past few decades, the chemical modification of device surfaces with thin polymeric coatings has been demonstrated to be a promising strategy to prevent these infections. This project developed multifunctional antibacterial coatings featuring low surface adherence against Escherichia coli and Staphylococcus aureus as well as the release of antibacterial agencies such as antibiotics to inhibit the proliferation of planktonic bacteria both on the surface and in the vicinity of the coatings. This approach is expected to be translated into biomedical device applications.</p

B02 inhibits the RAD51 foci formation in tumor tissue.

<p>NCR nude mice burdening with MDA-MB-231 xenograft tumors were treated by I.P. with either B02 (50 mg/kg), cisplatin (6 mg/kg), both or left untreated. The mice were sacrificed 3 h after administration, and tumor tissues were dissected and fixed in 10% formalin. Nuclei were counterstained with DAPI. After immunostaining with RAD51 antibodies, RAD51 foci were visualized using a ZEISS LSM5 confocal microscope with a 63× oil objective. Bars indicate 20 µm. The low panel shows the number of foci per nucleus in foci positive cells; it was determined by counting at least 20 nuclei in each experiment. Error bars represent SD.</p

A Small Molecule Inhibitor of Human RAD51 Potentiates Breast Cancer Cell Killing by Therapeutic Agents in Mouse Xenografts

<div><p>The homologous recombination pathway is responsible for the repair of DNA double strand breaks. RAD51, a key homologous recombination protein, promotes the search for homology and DNA strand exchange between homologous DNA molecules. RAD51 is overexpressed in a variety of cancer cells. Downregulation of RAD51 by siRNA increases radio- or chemo-sensitivity of cancer cells. We recently developed a specific RAD51 small molecule inhibitor, B02, which inhibits DNA strand exchange activity of RAD51 <i>in</i><i>vitro</i>. In this study, we used human breast cancer cells MDA-MB-231 to investigate the ability of B02 to inhibit RAD51 and to potentiate an anti-cancer effect of chemotherapeutic agents including doxorubicin, etoposide, topotecan, and cisplatin. We found that the combination of B02 with cisplatin has the strongest killing effect on the cancer cells. We then tested the effect of B02 and cisplatin on the MDA-MB-231 cell proliferation in mouse xenografts. Our results showed that B02 significantly enhances the therapeutic effect of cisplatin on tumor cells <i>in</i><i>vivo</i>. Our current data demonstrate that use of RAD51-specific small molecule inhibitor represents a feasible strategy of a combination anti-cancer therapy.</p></div

B02 increases sensitivity of 3D-growing MDA-MB-231 cells to cisplatin.

<p>A. MDA-MB-231 cells were exposed to cisplatin (in indicated concentrations) in the absence or presence of B02 (5 µM), the colonies were formed in 6-well plates coated with soft agar and stained with 0.005% crystal violet. B. The effect of B02 on survival of MDA-MB-231 cells plotted as a graph. C. The data from panel A plotted as a graph. Error bars represent SD.</p

B02 increases sensitivity of MDA-MB-231 cells to DNA damaging agents.

<p>A. The structures of B02, doxorubicin, etoposide, topotecan and cisplatin. B. Survival of MDA-MB-231 cells treated with B02 (○) or with indicated agents in the absence (▴) or presence (▾) of B02 (5 µM). Experiments were repeated at least three times. Error bars represent the standard deviation (SD).</p

B02 inhibits RAD51 foci formation in MDA-MB-231 cells.

<p>A. MDA-MB-231 cells were treated with cisplatin (32 µM) either alone or in the presence of B02 (in indicated concentrations). RAD51 foci were visualized by immunostaining with RAD51 antibodies. Nuclei were counterstained with DAPI. RAD51 foci were visualized by an Olympus IX70 inverted microscope with a 100× oil objective. Bars indicate 20 µm. B. The mean of RAD51 foci number per nucleus was determined by counting at least 50 cells in each experiment. Experiments were repeated three times. Error bars represent SD.</p

B02 in a combination with cisplatin causes a significant inhibition in tumor growth.

<p>A. The tumor images obtained 6(day 0) (top panel) and 32 days after the first treatment (day 32) (bottom panel). Mice were injected with 100 µl of D-luciferin K⁺ (GoldBio) (150 mg/kg) by I.P. and tumor cells were visualized using IVIS Lumina XR (Caliper Life Science). B. The bioluminescent intensities of tumors at day 0 and day 32 after indicated treatments were plotted as a graph. C. The ratios of bioluminescent signals observed at day 0 and day 32. Error bars represent SD.</p

The effect of cisplatin and B02 on the time course of tumor growth, A.

<p>After 11 days of tumor inoculation, tumors were touchable. Then mice were randomly regrouped (n = 5) and treated on day 11, 13, 15, 17 with either B02 (50 mg/kg), cisplatin (4 mg/kg), or a combination of both. Mice untreated or treated with vehicle (20% DMSO, 20% cremophor, 60% NS) were shown as controls. The tumor volumes were monitored by caliper measurement in each group. The time course of tumor growth presented as a graph. Error bars represent SD. Direct measurement of the weight of tumors tissues dissected from the mice after indicated treatment, B. Mice were sacrificed 43 days after tumor inoculation and the tumors were dissected. The weight of tumors shown in panel B presented as a graph, C. Error bars represent SD.</p