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Platelets are thought to play an important role in metastasis formation, although the mechanisms involved remain incompletely understood. Here we studied the influence of platelet numbers on organ-specific metastasis to the lungs and lymph nodes using Tpo deficient mice that have low platelet counts. After tail vein injection of 4T1 breast cancer cells, the number of lung metastases was significantly lower in Tpo−/− mice compared to Tpo+/+ mice. The same was true for the bone-tropic 4T1.2 derivative. In spontaneous orthotopic metastasis assays, 4T1 and 4T1.2 primary tumor growth was not affected by the genotype of the mice. However, the number of 4T1.2 lung metastases was significantly lower in Tpo−/− mice compared to Tpo+/+ mice, whereas the number of 4T1 lung metastases was unaffected. Moreover, in mice bearing 4T1 tumors, lymph node metastases were larger in the Tpo−/− background, and lymph node metastasis frequency was higher in Tpo−/− mice bearing 4T1.2 tumors compared to that in wild-type mice. Enhanced lymph node metastasis in Tpo−/− mice was not associated with changes in peritumoral lymphatic vessel density in the primary tumors. Together, our data indicate that platelets do not affect primary tumor growth in this breast cancer model, but can differentially influence site-specific metastasis to lymph nodes and lungs. [ABSTRACT FROM AUTHOR]

We have recently demonstrated that the anthocyanidin delphinidin (DEL), one of the most abundant dietary flavonoids, inhibits activation of ErbB and vascular endothelial growth factor receptor family members. These receptors play crucial roles in the context of tumor progression and the outgrowth of blood and lymphatic vessels. Here, we have developed an improved chemical synthesis for DEL in order to study the effects of the aglycon and its degradation product gallic acid (GA) on endothelial and tumor cells in vitro and in vivo. We found that DEL blocked the proliferation in vitro of primary human blood and lymphatic endothelial cells as well as human HT29 colon and rat MT-450 mammary carcinoma cells in a dose-dependent manner. In contrast, its degradation product GA had little effect. At higher concentrations, DEL induced apoptosis of endothelial and tumor cells. Furthermore, DEL potently blocked the outgrowth of lymphatic capillaries in ex vivo lymphangiogenesis assays. In the MT-450 rat syngeneic breast tumor model, it also significantly reduced angiogenesis and tumor-induced lymphangiogenesis when administered in vivo. These data reveal DEL to be a novel antilymphangiogenesis reagent. Surprisingly, however, the application of DEL unexpectedly promoted tumor growth and metastasis in the MT-450 tumor model, suggesting that the antiproliferative effect of DEL on cultured cells does not necessarily reflect the response of tumors to this anthocyanidin in vivo. Furthermore, while DEL may have utility as a cancer chemopreventative agent, its ability to promote tumor growth once a neoplasm develops also needs to be taken into consideration. [ABSTRACT FROM AUTHOR]

Purpose: This study examined the effect of insulin on sex cord stromal tumors in the rat. Methods: Sex cord stromal tumors were induced by transplantation of ovaries under the splenic capsule of ovariectomized rats (Lewis-inbred). These tumors were then transplanted into new inbred rats. Hyperglycemic conditions were induced by treatment with streptozotocin (STZ, which selectively destroyed pancreatic islet cells) and hypoglycemic conditions by treatment with a subcutaneously implanted insulin pump (Alzet). The animals were killed 28, 56, and 84 days later. Tumor growth, animal weight, food and water consumption, and serum concentrations of glucose, FSH, LH, and estradiol were measured. Results: Treatment with STZ and insulin with osmotic Alzet pumps induced continuous hypoglycemic and hyperglycemic conditions, respectively. No significant influence of the hypoglycemic or hyperglycemic status on tumor growth was measured during the first 28 and 56 days. Eighty-four days after transplantation and substitution of 1 or 2 IU/100 g body weight/d insulin, there was a significant stimulation of tumor growth (2.2-fold and 2.7-fold, respectively). In hyperglycemic animals (treated with STZ), no influence on tumor growth was found in comparison with the controls. Conclusion: This study confirms that hyperinsulinemic conditions contribute to the progression of tumors. [ABSTRACT FROM AUTHOR]

Background: The aim of this experimental study was to determine the effect of mild hyperthermia on tumor response and angioneogenesis in an isolated limb perfusion model with a human melanoma xenograft. Methods: A human melanoma xenograft was implanted into the hindlimbs of 30 athymic nude rats. The animals were randomized into five groups: group I: control, group II: sham group, group III: external hyperthermia with a tissue temperature of 41.5°C for 30 minutes without ILP, group IV: normothermic ILP (tissue temperature 37°C for 30 minutes, group V: hyperthermic ILP (tissue temperature 41.5°C for 30 minutes). Tumor response was evaluated by tumor size determination and immunohistochemical analysis 6 weeks postoperatively. Tissue sections were investigated for expression of CD34 and basic fibroblast growth factor (bFGF). Results: Average tumor volumes of the controls (I) increased from 105 mm³ to 1388 mm³. In the sham operated group (II) tumor volumes were significantly larger than in group I. Tumor volumes in group IV were significantly smaller than in group I and lowest in group V. There were no significant differences in size between group I and group III after six weeks. In group III and IV each, 5 animals showed tumor progression and one had a partial tumor response. In group V only 2 animals showed tumor progression. Immunhistochemical analysis of the tissue sections demonstrated that angioneogenesis was more pronounced in group II than in group I and less pronounced in group IV and V compared with group I. Conclusions: Our results suggest that even a surgical manipulation such as a skin incision promotes tumor growth, probably by induction of growth factors like bFGF. External hyperthermia of 41.5°C tissue temperature for 30 minutes only has no impact on tumor growth and angioneogenesis in vivo. [ABSTRACT FROM AUTHOR]

ASAP1 is a multi-domain adaptor protein that regulates cytoskeletal dynamics, receptor recycling and intracellular vesicle trafficking. Its expression is associated with poor prognosis in a variety of cancers, and can promote cell migration, invasion and metastasis. Although amplification and expression of ASAP1 has been associated with poor survival in breast cancer, we found that in the autochthonous MMTV-PyMT model of luminal breast cancer, ablation of ASAP1 resulted in an earlier onset of tumor initiation and increased metastasis. This was due to tumor cell-intrinsic effects of ASAP1 deletion, as ASAP1 deficiency in tumor, but not in stromal cells was sufficient to replicate the enhanced tumorigenicity and metastasis observed in the ASAP1-null MMTV-PyMT mice. Loss of ASAP1 in MMTV-PyMT mice had no effect on proliferation, apoptosis, angiogenesis or immune cell infiltration, but enhanced mammary gland hyperplasia and tumor cell invasion, indicating that ASAP1 can accelerate tumor initiation and promote dissemination. Mechanistically, these effects were associated with a potent activation of AKT. Importantly, lower ASAP1 levels correlated with poor prognosis and enhanced AKT activation in human ER+/luminal breast tumors, validating our findings in the MMTV-PyMT mouse model for this subtype of breast cancer. Taken together, our findings reveal that ASAP1 can have distinct functions in different tumor types and demonstrate a tumor suppressive activity for ASAP1 in luminal breast cancer. [ABSTRACT FROM AUTHOR]