ABSTRACT
The altered metabolism of cancer cells is a treasure trove to discover new antitumoral strategies. The gene (SLC7A5) encoding system L amino-acid transporter 1 (LAT1) is overexpressed in murine lymphoma cells generated via T-cell deletion of the pten tumor suppressor, and also in human T-cell acute lymphoblastic leukemia (T-ALL)/lymphoma (T-LL) cells. We show here that a potent and LAT1 selective inhibitor (JPH203) decreased leukemic cell viability and proliferation, and induced transient autophagy followed by apoptosis. JPH203 could also alter the in vivo growth of luciferase-expressing-tPTEN-/- cells xenografted into nude mice. In contrast, JPH203 was nontoxic to normal murine thymocytes and human peripheral blood lymphocytes. JPH203 interfered with constitutive activation of mTORC1 and Akt, decreased expression of c-myc and triggered an unfolded protein response mediated by the C/EBP homologous protein (CHOP) transcription factor associated with cell death. A JPH203-resistant tPTEN-/-clone appeared CHOP induction deficient. We also demonstrate that targeting LAT1 may be an efficient broad spectrum adjuvant approach to treat deadly T-cell malignancies as the molecule synergized with rapamycin, dexamethasone, doxorubicin, velcade and l-asparaginase to alter leukemic cell viability.
Subject(s)
Breast Neoplasms/drug therapy , Animals , Apoptosis , Blotting, Western , Breast Neoplasms/enzymology , Breast Neoplasms/pathology , Cell Adhesion , Cell Cycle , Cell Movement , Cell Proliferation , Female , Flow Cytometry , Fluorescent Antibody Technique , Humans , Immunoenzyme Techniques , Mice , Mice, Inbred BALB C , Mice, Nude , RNA, Messenger/genetics , Real-Time Polymerase Chain Reaction , Reverse Transcriptase Polymerase Chain Reaction , Tumor Cells, Cultured , Xenograft Model Antitumor AssaysABSTRACT
Phosphatase and tensin homolog deleted on chromosome 10 (Pten) is a tumor suppressor protein whose loss of lipid phosphatase activity is associated with lymphomagenesis. We made use of the Cre-loxP system to delete Pten expression in Lck- or CD4-expressing T-lineage cells. Mice initially showed modest thymic hyperplasia and subsequently developed expanding and infiltrating T-cell lymphomas, leading to a premature death within 5 to 23 weeks. Frequently, all thymocyte and peripheral T-cell populations displayed phenotypes characteristic for immature developing thymocyte precursors and shared elevated levels of clonally rearranged T-cell receptor (TCR) beta chains. In concert, CD2, CD5, CD3epsilon and CD44, proteins associated with increased expression and signaling capacity of both the immature pre-TCR and the mature alphabetaTCR, were more abundantly expressed, reflecting a constitutive state of activation. Although most T-cell lymphomas had acquired the capability to infiltrate the periphery, not all populations left the thymus and expanded clonally exclusively in the thymus. In line with this, only transplantation of thymocytes with infiltrating capacity gave rise to T-cell lymphoma in immunodeficient recipients. These results indicate that T-cell-specific Pten deletion during various stages of thymocyte development gives rise to clonally expanding T-cell lymphomas that frequently infiltrate the periphery, but originate in the thymus.
Subject(s)
Lymphoma, T-Cell/pathology , PTEN Phosphohydrolase/deficiency , Thymus Neoplasms/pathology , Animals , Antigens, CD/analysis , CD4 Antigens/biosynthesis , CD4 Antigens/genetics , Cell Lineage , Clone Cells/pathology , Gene Deletion , Gene Rearrangement, beta-Chain T-Cell Antigen Receptor , Hyperplasia , Immunophenotyping , Integrases/metabolism , Lymphocyte Specific Protein Tyrosine Kinase p56(lck)/biosynthesis , Lymphocyte Specific Protein Tyrosine Kinase p56(lck)/genetics , Lymphoma, T-Cell/genetics , Lymphoma, T-Cell, Peripheral/genetics , Lymphoma, T-Cell, Peripheral/pathology , Mice , Mice, Transgenic , Neoplasm Proteins/biosynthesis , Neoplasm Proteins/genetics , Neoplasm Transplantation , Organ Specificity , PTEN Phosphohydrolase/genetics , PTEN Phosphohydrolase/physiology , Specific Pathogen-Free Organisms , Thymus Neoplasms/geneticsSubject(s)
Bone Marrow Transplantation , Leukemia, Myeloid, Acute/surgery , Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Clinical Trials as Topic , Combined Modality Therapy , Humans , Leukemia, Myeloid, Acute/drug therapy , Multicenter Studies as Topic , Transplantation, Autologous , Transplantation, HomologousABSTRACT
Typical multi-drug resistance (MDR) in human and animal cell lines is caused by overactivity of a unidirectional drug efflux pump. This pump is composed of a 170-kDa transmembrane glycoprotein (P-glycoprotein) that is encoded by the so-called mdr1 gene. The functionally relevant characteristic of MDR cells is a defect in drug accumulation that can be restored by agents which inhibit the P-glycoprotein pump. The purpose of our study was to find out whether P-glycoprotein inhibitors could increase the daunorubicin (DNR) accumulation in acute myelocytic leukemia (AML) cells, overexpressing the mdr1 gene. Using dot blot analysis with an mdr1-specific cDNA probe, we identified leukemic cell samples, obtained from chemotherapy-resistant AML patients, that had relatively high levels of mdr1 expression. These leukemic cells showed a reduced ability to accumulate DNR in vitro, as quantitated by flow cytometry. Addition of cyclosporin-A (Cy-A), a drug known to inhibit the P-glycoprotein pump, to the incubation medium resulted in an increase (up to 60%) in steady-state drug uptake by the leukemic cells. The degree of Cy-A-induced increase in drug accumulation in the leukemic cells correlated approximately with the level of overexpression of the mdr1 gene. Our data indicate that Cy-A is a good candidate for combination chemotherapy with cytotoxic drugs in clinical trials, aimed at the treatment of drug resistance in AML.
