RESUMO
Lymphoma is a malignant neoplasm arising from B or T lymphocytes. In dogs, one-third of lymphomas are highly aggressive multicentric T-cell lymphomas that are often associated with humoral hypercalcaemia of malignancy (HHM). There are no cell lines or animal models to investigate the pathogenesis of T-cell lymphoma and HHM in dogs. We developed the first xenograft model by injecting lymphoma cells from an Irish Wolfhound intraperitoneally into NOD/SCID mice. The mice developed multicentric lymphoma along with HHM and increased parathyroid hormone-related protein (PTHrP) as occurs in dogs with T-cell lymphoma. Using cytokine complementary DNA arrays, we identified genes that have potential implications in the pathogenesis of T-cell lymphoma. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) of T-cell lymphoma samples from hypercalcaemic canine patients showed that PTHrP likely plays a central role in the pathogenesis of HHM and that hypercalcaemia is the result of a combinatorial effect of different hypercalcaemic factors. Finally, we monitored in vivo tumour progression and metastases in the mouse model by transducing the lymphoma cells with a lentiviral vector that encodes a luciferase-yellow fluorescent protein reporter and showed that in vivo trafficking patterns in this model were similar to those seen in dogs. This unique mouse model will be useful for translational research in lymphoma and for investigating the pathogenesis of T-cell lymphoma and HHM in the dog.
Assuntos
Modelos Animais de Doenças , Doenças do Cão/patologia , Hipercalcemia/etiologia , Linfoma de Células T/veterinária , Proteína Relacionada ao Hormônio Paratireóideo/genética , Animais , Cálcio/sangue , Citocinas/biossíntese , Cães , Feminino , Imuno-Histoquímica/veterinária , Luciferases , Medições Luminescentes/veterinária , Linfoma de Células T/complicações , Linfoma de Células T/patologia , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Transplante de Neoplasias/veterinária , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transplante Heterólogo/veterináriaRESUMO
Parathyroid hormone-related protein (PTHrP) plays a primary role in the development of humoral hypercalcemia of malignancy (HHM) that occurs in the majority of patients with adult T-cell leukemia/lymphoma (ATLL) due to human T-cell lymphotropic virus type-1 (HTLV-1) infection. We previously showed that ATLL cells constitutively express high levels of PTHrP via activation of promoters P2 and P3, resulting in HHM. In this study, we characterized a nuclear factor-kappaB (NF-kappaB) binding site in the P2 promoter of human PTHrP. Using electrophoretic mobility shift assays, we detected a specific complex in Tax-expressing human T cells composed of p50/c-Rel, and two distinct complexes in ATLL cells consisting of p50/p50 homodimers and a second unidentified protein(s). Chromatin immunoprecipitation assays confirmed in vivo binding of p50 and c-Rel on the PTHrP P2 promoter. Using transient co-transfection with NF-kappaB expression plasmids and PTHrP P2 luciferase reporter-plasmid, we showed that NF-kappaB p50/p50 alone and p50/c-Rel or p50/Bcl-3 cooperatively upregulated the PTHrP P2 promoter. Furthermore, inhibition of NF-kappaB activity by Bay 11-7082 reduced PTHrP P2 promoter-initiated transcripts in HTLV-1-infected T cells. In summary, the data demonstrated that transcriptional regulation of PTHrP in ATLL cells can be controlled by NF-kappaB activation and also suggest a Tax-independent mechanism of activation of PTHrP in ATLL.
Assuntos
Regulação Neoplásica da Expressão Gênica , Leucemia-Linfoma de Células T do Adulto/genética , NF-kappa B/fisiologia , Proteína Relacionada ao Hormônio Paratireóideo/genética , Regiões Promotoras Genéticas , Adulto , Animais , Western Blotting , Linhagem Celular Tumoral , Cloranfenicol O-Acetiltransferase , Imunoprecipitação da Cromatina , Ensaio de Desvio de Mobilidade Eletroforética , Infecções por HTLV-I/metabolismo , Infecções por HTLV-I/virologia , Humanos , Leucemia-Linfoma de Células T do Adulto/metabolismo , Leucemia-Linfoma de Células T do Adulto/patologia , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Mutagênese Sítio-Dirigida , Proteína Relacionada ao Hormônio Paratireóideo/metabolismo , Plasmídeos , Reação em Cadeia da Polimerase , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Ativação Transcricional , TransfecçãoRESUMO
The purpose of this study was to evaluate the role of the epidermal growth factor receptor (EGFR) in parathyroid hormone-related protein (PTHrP) expression and humoral hypercalcaemia of malignancy (HHM), using two different human squamous-cell carcinoma (SCC) xenograft models. A randomised controlled study in which nude mice with RWGT2 and HARA xenografts received either placebo or gefitinib 200 mg kg(-1) for 3 days after developing HHM. Effectiveness of therapy was evaluated by measuring plasma calcium and PTHrP, urine cyclic AMP/creatinine ratios, and tumour volumes. The study end point was at 78 h. The lung SCC lines, RWGT2 and HARA, expressed high levels of PTHrP mRNA as well as abundant EGFR protein, but very little erbB2 or erbB3. Both lines expressed high transcript levels for the EGFR ligand, amphiregulin (AREG), as well as, substantially lower levels of transforming growth factor-alpha (TGF-alpha), and heparin binding-epidermal growth factor (HB-EGF) mRNA. Parathyroid hormone-related protein gene expression in both lines was reduced 40-80% after treatment with 1 muM of EGFR tyrosine kinase inhibitor PD153035 and precipitating antibodies to AREG. Gefitinib treatment of hypercalcaemic mice with RWGT2 and HARA xenografts resulted in a significant reduction of plasma total calcium concentrations by 78 h. Autocrine AREG stimulated the EGFR and increased PTHrP gene expression in the RWGT2 and HARA lung SCC lines. Inhibition of the EGFR pathway in two human SCC models of HHM by an anilinoquinazoline demonstrated that the EGFR tyrosine kinase is a potential target for antihypercalcaemic therapy.
