PTEN is a tumor suppressor gene mutated in many human cancers, and its expression is reduced or absent in almost half of hepatoma patients. We used the Cre-loxP system to generate a hepatocyte-specific null mutation of Pten in mice (AlbCrePtenflox/flox mice). AlbCrePtenflox/flox mice showed massive hepatomegaly and steatohepatitis with triglyceride accumulation, a phenotype similar to human nonalcoholic steatohepatitis. Adipocyte-specific genes were induced in mutant hepatocytes, implying adipogenic-like transformation of these cells. Genes involved in lipogenesis and β-oxidation were also induced, possibly as a result of elevated levels of the transactivating factors PPARγ and SREBP1c. Importantly, the loss of Pten function in the liver led to tumorigenesis, with 47% of AlbCrePtenflox/flox livers developing liver cell adenomas by 44 weeks of age. By 74–78 weeks of age, 100% of AlbCrePtenflox/flox livers showed adenomas and 66% had hepatocellular carcinomas. AlbCrePtenflox/flox mice also showed insulin hypersensitivity. In vitro, AlbCrePtenflox/flox hepatocytes were hyperproliferative and showed increased hyperoxidation with abnormal activation of protein kinase B and MAPK. Pten is thus an important regulator of lipogenesis, glucose metabolism, hepatocyte homeostasis, and tumorigenesis in the liver.
Yasuo Horie, Akira Suzuki, Ei Kataoka, Takehiko Sasaki, Koichi Hamada, Junko Sasaki, Katsunori Mizuno, Go Hasegawa, Hiroyuki Kishimoto, Masahiro Iizuka, Makoto Naito, Katsuhiko Enomoto, Sumio Watanabe, Tak Wah Mak, Toru Nakano
The IL-12Rβ2 gene is expressed in human mature B cell subsets but not in transformed B cell lines. Silencing of this gene may be advantageous to neoplastic B cells. Our objective was to investigate the mechanism(s) and the functional consequence(s) of IL-12Rβ2 gene silencing in primary B cell tumors and transformed B cell lines. Purified tumor cells from 41 patients with different chronic B cell lymphoproliferative disorders, representing the counterparts of the major mature human B cell subsets, tested negative for IL-12Rβ2 gene expression. Hypermethylation of a CpG island in the noncoding exon 1 was associated with silencing of this gene in malignant B cells. Treatment with the DNA methyltransferase inhibitor 5-Aza-2′-deoxycytidine restored IL-12Rβ2 mRNA expression in primary neoplastic B cells that underwent apoptosis following exposure to human recombinant IL-12 (hrIL-12). hrIL-12 inhibited proliferation and increased the apoptotic rate of IL-12Rβ2–transfected B cell lines in vitro. Finally, hrIL-12 strongly reduced the tumorigenicity of IL-12Rβ2–transfected Burkitt lymphoma RAJI cells in SCID-NOD mice through antiproliferative and proapoptotic effects, coupled with neoangiogenesis inhibition related to human IFN-γ–independent induction of hMig/CXCL9. The IL-12Rβ2 gene acts as tumor suppressor in chronic B cell malignancies, and IL-12 exerts direct antitumor effects on IL-12Rβ2–expressing neoplastic B cells.
Irma Airoldi, Emma Di Carlo, Barbara Banelli, Lidia Moserle, Claudia Cocco, Annalisa Pezzolo, Carlo Sorrentino, Edoardo Rossi, Massimo Romani, Alberto Amadori, Vito Pistoia
The clonotypic surface Ig receptor expressed by malignant B cells, idiotype, is a tumor-specific antigen and an attractive target for active immunotherapy. While Ab’s specific for tumor idiotype have been well described in patients with B cell malignancies, the precise antigenic epitopes in human idiotype recognized by autologous T cells remain largely unknown. We report here that T cell lines generated from lymphoma patients actively immunized with idiotype protein specifically recognized multiple, unique immunodominant epitopes in autologous tumor idiotype. Synthetic peptides corresponding to hypervariable, but not framework, regions of Ig heavy chain specifically stimulated CD4+ and CD8+ T cells to proliferate and secrete proinflammatory cytokines in an MHC-associated manner. Detailed analysis revealed a minimal determinant of an immunodominant epitope, comprising critical residues at the amino terminus that may be a product of somatic hypermutation. Association of idiotype-specific T cell responses with previously documented molecular remissions in idiotype-vaccinated patients suggests that the newly identified T cell epitopes may be clinically relevant. Such antigenic epitopes may serve as candidates for novel peptide-vaccine strategies, and as tools to selectively expand tumor antigen–specific T cells for adoptive immunotherapy and for monitoring T cell immunity in vaccinated patients.
Sivasubramanian Baskar, Carol B. Kobrin, Larry W. Kwak
Ectopic gene expression in tumors versus normal somatic tissues provides opportunities for the specific immunotargeting of cancer cells. SSX gene products are expressed in tumors of different histological types and can be recognized by tumor-reactive CTLs from cancer patients. Here, we report the identification of an SSX-2–derived immunodominant T cell epitope recognized by CD4+ T cells from melanoma patients in association with HLA-DR. The epitope maps to the 37–58 region of the protein, encompassing the sequence of the previously defined HLA-A2–restricted immunodominant epitope SSX-241–49. SSX-237–58–specific CD4+ T cells were detected among circulating lymphocytes from the majority of melanoma patients analyzed and among tumor-infiltrating lymphocytes, but not in healthy donors. Together, our data suggest a dominant role of the 37–58 sequence in the induction of cellular CD4+ T cell responses against SSX antigens and will be instrumental for both the onset and the monitoring of upcoming cancer-vaccine trials using SSX-derived immunogens.
Maha Ayyoub, Charles S. Hesdorffer, Monica Montes, Andrea Merlo, Daniel Speiser, Donata Rimoldi, Jean-Charles Cerottini, Gerd Ritter, Matthew Scanlan, Lloyd J. Old, Danila Valmori
Accurate diagnosis of thyroid tumors is challenging. A particular problem is distinguishing between follicular thyroid carcinoma (FTC) and benign follicular thyroid adenoma (FTA), where histology of fine-needle aspirates is not conclusive. It is often necessary to remove healthy thyroid to rule out carcinoma. In order to find markers to improve diagnosis, we quantified gene transcript expression from FTC, FTA, and normal thyroid, revealing 73 differentially expressed transcripts (P ≤ 0.0001). Using an independent set of 23 FTCs, FTAs, and matched normal thyroids, 17 genes with large expression differences were tested by real-time RT-PCR. Four genes (DDIT3, ARG2, ITM1, and C1orf24) differed between the two classes FTC and FTA, and a linear combination of expression levels distinguished FTC from FTA with an estimated predictive accuracy of 0.83. Furthermore, immunohistochemistry for DDIT3 and ARG2 showed consistent staining for carcinoma in an independent set 59 follicular tumors (estimated concordance, 0.76; 95% confidence interval, [0.59, 0.93]). A simple test based on a combination of these markers might improve preoperative diagnosis of thyroid nodules, allowing better treatment decisions and reducing long-term health costs.
Janete M. Cerutti, Rosana Delcelo, Marcelo João Amadei, Claudia Nakabashi, Rui M.B. Maciel, Bercedis Peterson, Jennifer Shoemaker, Gregory J. Riggins
Lymphangiogenesis, an important initial step in tumor metastasis and transplant sensitization, is mediated by the action of VEGF-C and -D on VEGFR3. In contrast, VEGF-A binds VEGFR1 and VEGFR2 and is an essential hemangiogenic factor. We re-evaluated the potential role of VEGF-A in lymphangiogenesis using a novel model in which both lymphangiogenesis and hemangiogenesis are induced in the normally avascular cornea. Administration of VEGF Trap, a receptor-based fusion protein that binds and neutralizes VEGF-A but not VEGF-C or -D, completely inhibited both hemangiogenesis and the outgrowth of LYVE-1+ lymphatic vessels following injury. Furthermore, both lymphangiogenesis and hemangiogenesis were significantly reduced in mice transgenic for VEGF-A164/164 or VEGF-A188/188 (each of which expresses only one of the three principle VEGF-A isoforms). Because VEGF-A is chemotactic for macrophages and we demonstrate here that macrophages in inflamed corneas release lymphangiogenic VEGF-C/VEGF-D, we evaluated the possibility that macrophage recruitment plays a role in VEGF-A–mediated lymphangiogenesis. Either systemic depletion of all bone marrow–derived cells (by irradiation) or local depletion of macrophages in the cornea (using clodronate liposomes) prior to injury significantly inhibited both hemangiogenesis and lymphangiogenesis. We conclude that VEGF-A recruitment of monocytes/macrophages plays a crucial role in inducing inflammatory neovascularization by supplying/amplifying signals essential for pathological hemangiogenesis and lymphangiogenesis.
Claus Cursiefen, Lu Chen, Leonardo P. Borges, David Jackson, Jingtai Cao, Czeslaw Radziejewski, Patricia A. D’Amore, M. Reza Dana, Stanley J. Wiegand, J. Wayne Streilein
One of the major problems in management of prostate cancer is the lack of reliable genetic markers predicting the clinical course of the disease. We analyzed expression profiles of 12,625 transcripts in prostate tumors from patients with distinct clinical outcomes after therapy as well as metastatic human prostate cancer xenografts in nude mice. We identified small clusters of genes discriminating recurrent versus nonrecurrent disease with 90% and 75% accuracy in two independent cohorts of patients. We examined one group of samples (21 tumors) to discover the recurrence predictor genes and then validated the predictive power of these genes in a different set (79 tumors). Kaplan-Meier analysis demonstrated that recurrence predictor signatures are highly informative (P < 0.0001) in stratification of patients into subgroups with distinct relapse-free survival after therapy. A gene expression–based recurrence predictor algorithm was informative in predicting the outcome in patients with early-stage disease, with either high or low preoperative prostate-specific antigen levels and provided additional value to the outcome prediction based on Gleason sum or multiparameter nomogram. Overall, 88% of patients with recurrence of prostate cancer within 1 year after therapy were correctly classified into the poor-prognosis group. The identified algorithm provides additional predictive value over conventional markers of outcome and appears suitable for stratification of prostate cancer patients at the time of diagnosis into subgroups with distinct survival probability after therapy.
Gennadi V. Glinsky, Anna B. Glinskii, Andrew J. Stephenson, Robert M. Hoffman, William L. Gerald
Oncogenic ras alleles are among the most common mutations found in patients with acute myeloid leukemia (AML). Previously, the role of oncogenic ras in cancer was assessed in model systems overexpressing oncogenic ras from heterologous promoters. However, there is increasing evidence that subtle differences in gene dosage and regulation of gene expression from endogenous promoters play critical roles in cancer pathogenesis. We characterized the role of oncogenic K-ras expressed from its endogenous promoter in the hematopoietic system using a conditional allele and IFN-inducible, Cre-mediated recombination. Mice developed a completely penetrant myeloproliferative syndrome characterized by leukocytosis with normal maturation of myeloid lineage cells; myeloid hyperplasia in bone marrow; and extramedullary hematopoiesis in the spleen and liver. Flow cytometry confirmed the myeloproliferative phenotype. Genotypic and Western blot analysis demonstrated Cre-mediated excision and expression, respectively, of the oncogenic K-ras allele. Bone marrow cells formed growth factor–independent colonies in methylcellulose cultures, but the myeloproliferative disease was not transplantable into secondary recipients. Thus, oncogenic K-ras induces a myeloproliferative disorder but not AML, indicating that additional mutations are required for AML development. This model system will be useful for assessing the contribution of cooperating mutations in AML and testing ras inhibitors in vivo.
Iris T. Chan, Jeffery L. Kutok, Ifor R. Williams, Sarah Cohen, Lauren Kelly, Hirokazu Shigematsu, Leisa Johnson, Koichi Akashi, David A. Tuveson, Tyler Jacks, D. Gary Gilliland
Avicins are proapoptotic and anti-inflammatory triterpene electrophiles isolated from an Australian desert tree, Acacia victoriae. The presence of two α,β unsaturated carbonyl groups (Michael reaction sites) in the side chain of the avicin molecule prompted us to study its effects on NF-E2–related factor 2 (Nrf2), a redox-regulated transcription factor that controls the expression of a battery of detoxification and antioxidant proteins via its binding to antioxidant response element (ARE). Avicin D–treated Hep G2 cells showed translocation of Nrf2 into the nucleus and a time-dependent increase in ARE activity. These properties were sensitive to DTT, suggesting that avicins affect one or more critical cysteine residues, probably on the Keap1 molecule. Downstream of ARE, an activation of a battery of stress-induced proteins occurred. The implications of these findings were evaluated in vivo in mouse skin exposed to an ancient stressor, UV light. Avicins inhibited epidermal hyperplasia, reduced p53 mutation, enhanced apoptosis, decreased generation of 8-hydroxy-2′-deoxyguanosine, and enhanced expression of NADPH:quinone oxidoreductase 1 and heme oxygenase-1. These data, combined with our earlier published work, demonstrate that avicins represent a new class of plant stress metabolites capable of activating stress adaptation and suppressing proinflammatory components of the innate immune system in human cells by redox regulation. The relevance for treatment of clinical diseases in which stress responses are dysfunctional or deficient is discussed.
Valsala Haridas, Margaret Hanausek, Goshi Nishimura, Holly Soehnge, Amos Gaikwad, Maciej Narog, Erick Spears, Robert Zoltaszek, Zbigniew Walaszek, Jordan U. Gutterman
Malignant cells often display defects in autophagy, an evolutionarily conserved pathway for degrading long-lived proteins and cytoplasmic organelles. However, as yet, there is no genetic evidence for a role of autophagy genes in tumor suppression. The beclin 1 autophagy gene is monoallelically deleted in 40–75% of cases of human sporadic breast, ovarian, and prostate cancer. Therefore, we used a targeted mutant mouse model to test the hypothesis that monoallelic deletion of beclin 1 promotes tumorigenesis. Here we show that heterozygous disruption of beclin 1 increases the frequency of spontaneous malignancies and accelerates the development of hepatitis B virus–induced premalignant lesions. Molecular analyses of tumors in beclin 1 heterozygous mice show that the remaining wild-type allele is neither mutated nor silenced. Furthermore, beclin 1 heterozygous disruption results in increased cellular proliferation and reduced autophagy in vivo. These findings demonstrate that beclin 1 is a haplo-insufficient tumor-suppressor gene and provide genetic evidence that autophagy is a novel mechanism of cell-growth control and tumor suppression. Thus, mutation of beclin 1 or other autophagy genes may contribute to the pathogenesis of human cancers.
Xueping Qu, Jie Yu, Govind Bhagat, Norihiko Furuya, Hanina Hibshoosh, Andrea Troxel, Jeffrey Rosen, Eeva-Liisa Eskelinen, Noboru Mizushima, Yoshinori Ohsumi, Giorgio Cattoretti, Beth Levine