pki-166 and Bone-Neoplasms

Once prostate cancer metastasizes to bone, conventional chemotherapy is largely ineffective. We hypothesized that inhibition of phosphorylation of the epidermal growth factor receptor (EGF-R) and platelet-derived growth factor receptor (PDGF-R) expressed on tumor cells and tumor-associated endothelial cells, which is associated with tumor progression, in combination with paclitaxel would inhibit experimental prostate cancer bone metastasis and preserve bone structure. We tested this hypothesis in nude mice, using human PC-3MM2 prostate cancer cells. PC-3MM2 cells growing adjacent to bone tissue and endothelial cells within these lesions expressed phosphorylated EGF-R and PDGF-R alpha and -beta on their surfaces. The percentage of positive endothelial cells and the intensity of receptor expression directly correlated with proximity to bone tissue. Oral administration of PKI166 inhibited the phosphorylation of EGF-R but not PDGF-R, whereas oral administration of STI571 inhibited the phosphorylation of PDGF-R but not EGF-R. Combination therapy using oral PKI166 and STI571 with i.p. injections of paclitaxel induced a high level of apoptosis in tumor vascular endothelial cells and tumor cells in parallel with inhibition of tumor growth in the bone, preservation of bone structure, and reduction of lymph node metastasis. Collectively, these data demonstrate that blockade of phosphorylation of EGF-R and PDGF-R coupled with administration of paclitaxel significantly suppresses experimental human prostate cancer bone metastasis.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Benzamides; Bone Neoplasms; Cell Division; Enzyme Inhibitors; ErbB Receptors; Humans; Imatinib Mesylate; In Situ Nick-End Labeling; Male; Mice; Mice, Nude; Paclitaxel; Phosphorylation; Piperazines; Platelet Endothelial Cell Adhesion Molecule-1; Prostatic Neoplasms; Pyrimidines; Pyrroles; Receptors, Platelet-Derived Growth Factor; Substrate Specificity; Xenograft Model Antitumor Assays

We determined whether blockade of the epidermal growth factor receptor (EGF-R) signaling pathway by oral administration of the EGF-R tyrosine kinase inhibitor (PKI 166) alone or in combination with injectable Taxol inhibits the growth of PC-3MM2 human prostate cancer cells in the bone of nude mice.. Male nude mice implanted with PC-3MM2 cells in the tibia were treated with oral administrations of PKI 166 or PKI 166 plus injectable Taxol beginning 3 days after implantation. The incidence and size of bone tumors and destruction of bone were determined by digitalized radiography. Expression of epidermal growth factor (EGF), EGF-R, and activated EGF-R in tumor cells and tumor-associated endothelial cells was determined by immunohistochemistry.. Oral administration of PKI 166 or PKI 166 plus injectable Taxol reduced the incidence and size of bone tumors and destruction of bone. Immunohistochemical analysis revealed that PC-3MM2 cells growing adjacent to the bone expressed high levels of EGF and activated EGF-R, whereas tumor cells in the adjacent musculature did not. Moreover, endothelial cells within the bone tumor lesions, but not in uninvolved bone or tumors in the muscle, expressed high levels of activated EGF-R. Treatment with PKI 166 and more so with PKI 166 plus Taxol significantly inhibited phosphorylation of EGF-R on tumor and endothelial cells and induced significant apoptosis and endothelial cells within tumor lesions.. These data indicate that endothelial cells exposed to EGF produced by tumor cells express activated EGF-R and that targeting EGF-R can produce significant therapeutic effects against prostate cancer bone metastasis.

Topics: Administration, Oral; Animals; Antineoplastic Agents, Phytogenic; Blotting, Western; Bone and Bones; Bone Neoplasms; Dose-Response Relationship, Drug; Endothelial Growth Factors; Endothelium, Vascular; ErbB Receptors; Fibroblast Growth Factor 2; Immunohistochemistry; In Situ Nick-End Labeling; Intercellular Signaling Peptides and Proteins; Interleukin-8; Lymphokines; Male; Mice; Mice, Nude; Microscopy, Fluorescence; Neoplasm Metastasis; Neoplasm Transplantation; Paclitaxel; Phosphorylation; Platelet Endothelial Cell Adhesion Molecule-1; Proliferating Cell Nuclear Antigen; Prostatic Neoplasms; Pyrimidines; Pyrroles; Signal Transduction; Tumor Cells, Cultured; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

Renal cell carcinoma (RCC) frequently produces metastases to the musculoskeletal system that are a major source of morbidity in the form of pain, immobilization, fractures, neurological compromise, and a decreased ability to perform activities of daily living. Patients with metastatic RCC therefore have a dismal prognosis because there is no effective adjuvant treatment for this disease. Because the epidermal growth factor receptor (EGF-R) signaling cascade is important in the growth and metastasis of RCC, its blockade has been hypothesized to inhibit tumor growth and hence prevent resultant bone destruction. We determined whether blockade of EGF-R by the tyrosine kinase inhibitor PKI 166 inhibited the growth of RCC in bone. We use a novel cell line, RBM1-IT4, established from a human RCC bone metastasis. Protein and mRNA expression of the ligands and receptors was assessed by Western and Northern blots. The stimulation of RBM1-IT4 cells with epidermal growth factor or transforming growth factor alpha resulted in increased cellular proliferation and tyrosine kinase autophosphorylation. PKI 166 prevented these effects. First, RBM1-IT4 cells were implanted into the tibia of nude mice, where they established lytic, progressively growing lesions, after which the mice were treated with PKI 166 alone or in combination with paclitaxel (Taxol). Immunohistochemical analysis revealed that tumor cells and tumor-associated endothelial cells in control mice expressed activated EGF-R. Treatment of mice with PKI 166 alone or in combination with Taxol produced a significant decrease in the incidence and size of bone lesions as compared with the results in control or Taxol-treated mice (P < 0.001). Treatment with PKI 166 also decreased the expression of phosphorylated EGF-R by tumor cells and tumor-associated endothelial cells, and this was even more pronounced with PKI 166 plus Taxol treatment. The PKI 166 plus Taxol combination produced apoptosis of tumor cells and tumor-associated endothelial cells. Tumor cell proliferation, shown by proliferating cell nuclear antigen positivity, was decreased in all treatment groups. In addition, the integrity of the bone was maintained in mice treated with PKI 166 or PKI 166 plus Taxol, whereas massive bone destruction was seen in control and Taxol-treated mice. These results suggest that blockade of EGF-R signaling inhibits growth of RCC in the bone by its effect on tumor cells and tumor-associated endothelial cells.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Bone Neoplasms; Carcinoma, Renal Cell; Cell Division; Epidermal Growth Factor; ErbB Receptors; Humans; Kidney Neoplasms; Male; Mice; Mice, Nude; Paclitaxel; Phosphorylation; Pyrimidines; Pyrroles; Recombinant Proteins; Signal Transduction; Transforming Growth Factor alpha; Tumor Cells, Cultured; Xenograft Model Antitumor Assays

Renal cell carcinoma frequently metastasizes to the skeleton in the later stages of the disease. Patients with bone metastasis from renal cell carcinoma experience severe pain, neurologic compromise, and frequent pathologic fractures. These tumors are relatively resistant to chemotherapy and radiation, and the 5-year survival of patients is less than 10%. The epidermal growth factor receptor is overexpressed in human renal cell carcinoma and hypothesized to be a potential target in the treatment of bone metastasis. Using in vitro studies, it was shown that blockade of the epidermal growth factor receptor was effective in decreasing proliferation and receptor autophosphorylation of a human bone-derived renal cell carcinoma cell line. In an experimental nude mouse model, treatment with Taxol and protein tyrosine kinase inhibitor 166, a small molecule receptor tyrosine kinase inhibitor, blocked the growth of renal cell carcinoma in the tibia and resulted in decreased bone destruction. The use of protein tyrosine kinase inhibitor 166 and Taxol was cytostatic and nontoxic in long-term animal experiments. Epidermal growth factor receptor blockade is an exciting potential therapy for renal cell carcinoma bone metastasis in humans, but because it is cytostatic rather than cytotoxic, its optimal role may be as a supplement to cytotoxic chemotherapy. It ultimate role and its relationship to other therapeutic interventions remains to be elucidated and validated.

Topics: Animals; Antineoplastic Agents, Phytogenic; Bone Neoplasms; Carcinoma, Renal Cell; ErbB Receptors; Kidney Neoplasms; Mice; Mice, Nude; Paclitaxel; Phosphorylation; Pyrimidines; Pyrroles; Tumor Cells, Cultured