Abstract. Pancreatic cancer is now one of the most common causes of cancer death worldwide. K-ras mutations are present in up to 90% of pancreatic cancer cases. The expression of mutant K-ras activates the Akt/protein kinase B pathway, resulting in the activation of the nuclear factor-κB (NF-κB) transcriptional factor. Constitutive NF-κB activity plays a key role in pancreatic carcinoma. NF-κB has been shown to inhibit apoptosis in response to chemotherapeutic agents. In the present study, the effects of lidamycin (LDM), a member of the enediyne antibiotic family, were investigated on two established pancreatic cell lines, PANC-1 and SW1990. A dose-dependent inhibition of phospho-Akt and NF-κB activation was found in the cells treated with LDM as determined by Western blot analysis. Moreover, a downregulation of K-ras mRNA and a protein expression by LDM were observed in both cell lines as determined by reverse transcription-PCR and Western blot analysis. By MTT assay, a remarkable difference in chemosensitivity to LDM, mitomycin, adriamycin, taxol, and gemcitabine was found in both cell lines. The IC 50 values of LDM for the PANC-1 or SW1990 cells were 0.955±0.414 or 0.426±0.212 nM, respectively, lower than those of the other drugs. Growth inhibition, apoptosis induction and cell cycle arrest were observed in the LDMtreated cells. LDM decreased the invasive potential of pancreatic cancer cells by reducing matrix metalloproteinase-9 activity. Furthermore, LDM was found to suppress the growth of SW1990 xenografts in nude mice. Treatment with an i.v. injection of LDM at the dose of 0.02 and 0.04 mg/kg (once a week for two weeks) inhibited the growth of xenografts by 66 and 72%, respectively. By contrast, an i.p. injection of gemcitabine at the dose of 80 mg/kg inhibited the growth of xenografts by 38%. Our findings suggest that LDM is active in the down-regulation of NF-κB and could play a positive role in relevant targeted chemotherapy for pancreatic carcinoma.

The present work evaluated the synergistic efficacy of an enediyne antibiotic lidamycin (LDM) plus temozolomide (TMZ) against glioma in vitro and in vivo. LDM plus TMZ inhibited the proliferations of rat glioma C6 cells and human glioma U87 cells more efficiently than the single usage of LDM or TMZ. In addition, LDM also potentiated the apoptosis inductions by TMZ in rat C6 cells and human U87 cells. Meanwhile, the results of TdT-mediated dUTP Nick End Labeling assay for subcutaneous U87 tumor sections indicated an enhanced apoptosis induction in vivo by LDM plus TMZ, which confirmed the high potency of the combination for glioma therapy. As determined by Western blot, apoptosis signal pathways in C6 cells and U87 cells were markedly affected by the synergistic alteration of P53, bax, procaspase 3, and bcd-2 expression. In both subcutaneous U87 xenograft and C6 intracerebral orthotopic implant model, TMZ-induced glioma growth suppression was dramatically potentiated by LDM. As shown, the combination therapy efficiently reduced the tumor volumes and tumor weights of the human glioma U87 xenograft. Kaplan-Meier assay revealed that LDM plus TMZ dramatically prolonged the life span of C6 intracerebral tumor-bearing rats with decreased tumor size. This study indicates that the combination of LDM with TMZ might be a promising strategy for glioma therapy.

Type IV collagenase plays a pivotal role in invasion, metastasis and angiogenesis of tumor. Single domain antibodies are attractive as tumor-targeting vehicle because of their much smaller size compared with antibody molecules produced by conventional methods. Lidamycin (LDM) is a potent enediyne-containing antitumor antibiotic. In this study an engineered and energized fusion protein VL-LDP-AE composed of lidamycin and VL domain of mAb 3G11 directed against type IV collagenase was prepared using a novel two-step method. First a VL-LDP fusion protein was constructed by DNA recombination. Secondly VL-LDP-AE was obtained by molecular reconstitution. In MTT assay, VL-LDP-AE showed potent cytotoxicity to HT-1080 cells and KB cells with IC(50) values of 8.55 x 10(-12) and 1.70 x 10(-11) mol/L, respectively. VL-LDP-AE showed antiangiogenic activity in chick chrorioallantoic membrane (CAM) assay and tube formation assay. In in vivo experiments, VL-LDP-AE was proved to be more effective than free LDM against the growth of subcutaneously transplanted hepatoma 22 in mice. Drugs were given intravenously on day 3 and 10 after tumor transplantation. Compared in terms of maximal tolerated doses, VL-LDP-AE at 0.25 mg/kg suppressed the tumor growth by 89.5%, LDM at 0.05 mg/kg by 69.9%, and mitomycin at 1 mg/kg by 35%. Having a molecular weight of 25.2 kDa, VL-LDP-AE was much smaller than other reported antibody-based drugs. The results suggested that VL-LDP-AE would be a promising candidate for tumor targeting therapy. And the 2-step approach could serve as a new technology platform for making a series of highly potent engineered antibody-based drugs for a variety of cancers.

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The spreading out of microvessel endothelial cells plays a key role in angiogenesis and the post-injury healing of endothelial cells. In our study, a physical force applied with an atomic force microscopic (AFM) cantilever tip in contact mode partly broke the peripheral adhesion that just-confluent cultured rat cerebral microvessel endothelial cells had formed with basal structures and resulted in the cells actively withdrawing from the stimulated area. Time-series changes in cell extension were imaged using tapping mode AFM, in conjunction with total internal reflection fluorescence microscopy, intensified charge-coupled device and field emission scanning electron microscopy. We also interpreted phase images of living endothelial cells. The results showed that formation of a fibronectin molecule monolayer is key to the spreading out of the cells. Lamellipods as well as filopods would spread out in temporal and spatial distribution following the formation of fibronectin layer. In addition, a lattice-like meshwork of filopods formed in the regions leading lamellipods, which would possibly provide a fulcrum for the filaments of the cytoskeleton within the leading cell body periphery.