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Whereas radioimmunotherapy of hematologic malignancies has evolved into a viable treatment option, the responses of solid tumors to radioimmunotherapy are discouraging. The likely cause of this problem is the interstitial hypertension inherent to all solid tumors. Remarkable improvements in tumor responses to radioimmunotherapy were discovered after the inclusion of STI571 in the therapy regimen. A combination of the tumor stroma-reactive STI571, a potent platelet-derived growth factor receptor-B (PDGFr-B) antagonist, and the tumor-seeking radiolabeled antibody B72.3 yielded long-lasting growth arrest of the human colorectal adenocarcinoma LS174T grown as s.c. xenografts in athymic mice. The interaction of STI571 with the stromal PDGFr-B reduced tumor interstitial fluid pressure (P IF ) by >50% and in so doing improved the uptake of B72.3. The attenuation of P IF also had a positive effect on the homogeneity of antibody distribution. These effects were dose-dependent and under optimized dosing conditions allowed for a 2.45 times increase in the tumor uptake of B72.3 as determined in the biodistribution studies. Single-photon emission computed tomography imaging studies substantiated these results and indicated that the homogeneity of the radioisotope distribution was also much improved when compared with the control mice. The increased uptake of radioimmunotherapy into the tumor resulted in >400% increase in the tumor absorbed radiation doses in STI571 + radioimmunotherapy-treated mice compared with PBS + radioimmunotherapy-treated mice. The improved antibody uptake in response to the attenuation of tumor P IF was identified as the primary reason for the growth arrest of the STI571 + radioimmunotherapy-treated tumors. Two related causes were also identified: (a) the improved homogeneity of monoclonal antibody distribution in tumor and (b) the increased tumor radiosensitivity resulting from the improved tumor oxygenation. (Cancer Res 2005; 65(17): 7824-31)

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To clarify the potential involvement of plasmin(ogen) cascade proteins in the cell dissociation and subsequent invasion of pancreatic cancer cells, Western blot analysis, immunocytochemistry, immunohistochemistry, and in vitro invasion assay were performed in the cell lines or tissue of pancreatic cancer. The strong expression of plasmin(ogen), urokinase type plasminogen activator (uPA) and uPA receptor (uPAR), and apparently weak expression of the relevant proteins were found in the conditioned medium of dissociated (PC-1.0) and non-dissociated (PC-1) pancreatic cancer cells, respectively. Furthermore, uPA-treatment significantly induced the expression of plasmin(ogen) and uPAR in the conditioned medium of non-dissociated (PC-1) pancreatic cancer cells. Moreover, the expression of plasmin(ogen) and uPAR was stronger at the invasive front than at the center of human pancreatic cancer tissue. On the other hand, plasmin-treatment induced the expression of matrix metalloproteinase-2 (MMP-2), MMP-7 and MMP-9 in PC-1 cells. Simultaneously, plasminor uPA-treatments obviously induced the dissociation of cell colonies and in vitro invasiveness in PC-1 cells. The plasmin(ogen) cascade is closely involved in the invasion of pancreatic cancer cells and, especially in its early stage, cell dissociation. Targeting the plasmin(ogen) cascade may provide a new insight into molecular target therapy based on antiinvasion and anti-metastasis for pancreatic cancer.

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Purpose: Thus far, the therapy of pancreatic cancer remains an insurmountable challenge. Not a solitary therapeutic modality in the battery of available therapeutic options is capable to cure or, at the very least, stop the progression of this disease in any meaningful way. The purpose of reported here studies was to implement a multimodality approach to radioimmunotherapy of pancreatic cancer and, ultimately, to develop a course of therapy with the clinical value. Conclusions: The inclusion of imatinib in the radioimmunotherapy regimen is beneficial and it does not produce any overt side effects.The improved responses of pancreatic cancer xenografts to the multimodality treatment comprising radioimmunotherapy and platelet-derived growth factor receptor-h inhibition suggest that this approach to therapy of pancreatic cancer may also be successful in patients.

Background Human liver has an unusual sensitivity to radiation that limits its use in cancer therapy or in preconditioning for hepatocyte transplantation. Since the characteristic venocclusive lesions of radiation-induced liver disease do not occur in rodents, there has been no experimental model to investigate the limits of safe radiation therapy or explore the pathogenesis of hepatic venocclusive disease. Methods We performed a dose escalation study in a primate, the cynomolgus monkey, using hypofractionated stereotactic body radiotherapy in 13 animals. Results At doses ≥40Gy, animals developed a systemic syndrome resembling human radiation-induced liver disease, consisting of decreased albumin, elevated alkaline phosphatase, loss of appetite, ascites, and normal bilirubin. Higher radiation doses were lethal, causing severe disease that required euthanasia approximately 10 weeks after radiation. Even at lower doses where radiation-induced liver disease was mild or non-existent, latent and significant injury to hepatocytes was demonstrated by asialoglycoprotein-mediated functional imaging. These monkeys developed hepatic failure with encephalopathy when they received parenteral nutrition containing high concentrations of glucose. Histologically, livers showed central obstruction via an unusual intimal swelling that progressed to central fibrosis. Conclusions The cynomolgus monkey, as the first animal model of human venocclusive radiation-induced liver disease, provides a resource for characterizing the early changes and pathogenesis of venocclusion, for establishing nonlethal therapeutic dosages, and for examining experimental therapies to minimize radiation injury.

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