Spontaneous Lymphoma Research Articles

Deletion of p37Ing1 in Mice Reveals a p53-Independent Role for Ing1 in the Suppression of Cell Proliferation, Apoptosis, and Tumorigenesis

ING proteins have been proposed to alter chromatin structure and gene transcription to regulate numerous aspects of cell physiology, including cell growth, senescence, stress response, apoptosis, and transformation. ING1, the founding member of the inhibitor of growth family, encodes p37(Ing1), a plant homeodomain (PHD) protein that interacts with the p53 tumor suppressor protein and seems to be a critical cofactor in p53-mediated regulation of cell growth and apoptosis. In this study, we have generated and analyzed p37(Ing1)-deficient mice and primary cells to further explore the role of Ing1 in the regulation of cell growth and p53 activity. The results show that endogenous levels of p37(Ing1) inhibit the proliferation of p53-wild-type and p53-deficient fibroblasts, and that p53 functions are unperturbed in p37(Ing1)-deficient cells. In addition, loss of p37(Ing1) induces Bax expression and increases DNA damage-induced apoptosis in primary cells and mice irrespective of p53 status. Finally, p37(Ing1) suppresses the formation of spontaneous follicular B-cell lymphomas in mice. These results indicate that p53 does not require p37(Ing1) to negatively regulate cell growth and offers genetic proof that Ing1 suppresses cell growth and tumorigenesis. Furthermore, these data reveal that p37(Ing1) can negatively regulate cell growth and apoptosis in a p53-independent manner.

Tumor-Induced Sentinel Lymph Node Lymphangiogenesis and Increased Lymph Flow Precede Melanoma Metastasis

Lymphangiogenesis is associated with human and murine cancer metastasis, suggesting that lymphatic vessels are important for tumor dissemination. Lymphatic vessel alterations were examined using B16-F10 melanoma cells implanted in syngeneic C57Bl/6 mice, which form tumors metastasizing to draining lymph nodes and subsequently to the lungs. Footpad tumors showed no lymphatic or blood vessel growth; however, the tumor-draining popliteal lymph node featured greatly increased lymphatic sinuses. Lymph node lymphangiogenesis began before melanoma cells reached draining lymph nodes, indicating that primary tumors induce these alterations at a distance. Lymph flow imaging revealed that nanoparticle transit was greatly increased through tumor-draining relative to nondraining lymph nodes. Lymph node lymphatic sinuses and lymph flow were increased in mice implanted with unmarked or with foreign antigen-expressing melanomas, indicating that these effects are not due to foreign antigen expression. However, tumor-derived immune signaling could promote lymph node alterations, as macrophages infiltrated footpad tumors, whereas lymphocytes accumulated in tumor-draining lymph nodes. B lymphocytes are required for lymphangiogenesis and increased lymph flow through tumor-draining lymph nodes, as these alterations were not observed in mice deficient for B cells. Lymph node lymphangiogenesis and increased lymph flow through tumor-draining lymph nodes may actively promote metastasis via the lymphatics.

Aneuploidy Acts Both Oncogenically and as a Tumor Suppressor

An abnormal chromosome number, aneuploidy, is a common characteristic of tumor cells. Boveri proposed nearly 100 years ago that aneuploidy causes tumorigenesis, but this has remained untested due to the difficulty of selectively generating aneuploidy. Cells and mice with reduced levels of the mitosis-specific, centromere-linked motor protein CENP-E are now shown to develop aneuploidy and chromosomal instability in vitro and in vivo. An increased rate of aneuploidy does drive an elevated level of spontaneous lymphomas and lung tumors in aged animals. Remarkably, however, in examples of chemically or genetically induced tumor formation, an increased rate of aneuploidy is a more effective inhibitor than initiator of tumorigenesis. These findings reveal a role of aneuploidy and chromosomal instability in preventing tumorigenesis.

Translational Regulation of Autoimmune Inflammation and Lymphoma Genesis by Programmed Cell Death 4

Both inflammatory diseases and cancer are associated with heightened protein translation. However, the mechanisms of translational regulation and the roles of translation factors in these diseases are not clear. Programmed cell death 4 (PDCD4) is a newly described inhibitor of protein translation. To determine the roles of PDCD4 in vivo, we generated PDCD4-deficient mice by gene targeting. We report here that mice deficient in PDCD4 develop spontaneous lymphomas and have a significantly reduced life span. Most tumors are of the B lymphoid origin with frequent metastasis to liver and kidney. However, PDCD4-deficient mice are resistant to inflammatory diseases such as autoimmune encephalomyelitis and diabetes. Mechanistic studies reveal that upon activation, PDCD4-deficient lymphocytes preferentially produce cytokines that promote oncogenesis but inhibit inflammation. These results establish that PDCD4 controls lymphoma genesis and autoimmune inflammation by selectively inhibiting protein translation in the immune system.

Ikaros is a mutational target for lymphomagenesis in Mlh1-deficient mice

Deficiencies in DNA mismatch repair (MMR) result in replication errors within key tumor suppressor genes or oncogenes, and cause hereditary nonpolyposis colorectal cancer (HNPCC). Hematological malignancy with microsatellite instability is also associated with defective MMR, but little is known about the target genes for MMR. Here we identified Ikaros, a master transcription factor of lymphoid lineage commitment and differentiation, as a mutational target in spontaneous and radiation-induced T-cell lymphomas in Mlh1-deficient mice. Three quarters of lymphomas lacked Ikaros protein expression, which resulted from a frameshift mutation that created a stop codon. Mononucleotide repeat sequences at 1029-1034(C)6 and 1567-1572(G)6 in Ikaros were mutational hot spots with a one-base deletion occurring with a frequency of 45 and 50%, respectively. Point mutations and splicing alterations were also observed. In total, 85% of the lymphomas showed aberrations in Ikaros. The characteristic of Mlh1-deficient lymphomas is harboring of multiple mutations simultaneously in the same tumor, displaying a combination of two frameshift mutations at different repeats, frameshift and point mutations, and/or deletion mutations. This is the first report of Ikaros mutations coupled with Mlh1 deficiency in lymphomagenesis.

Paraneoplastic Neurodegeneration in a Murine Host following Progressive Growth of a Spontaneous T-Cell Lymphoma: Role of Proinflammatory Internal Responses

Objective(s): In the present study, the mechanism of paraneoplastic neurodegeneration associated with progressive in vivo growth of a T-cell lymphoma of spontaneous origin has been investigated. Methods: Histologically, the brain was investigated by hematoxylin-eosin staining of brain sections. Western blotting was performed to detect the expression of cytokines and other proteins. Macrophage-derived interleukin-1 (IL-1) and tumor necrosis factor (TNF) was estimated by immunoassays. Induction of apoptosis in brain and tumor cells was determined by percent specific DNA fragmentation. Results: Tumor growth was associated with the development of multiple lesions in various regions of the brain along with alterations in the structure and alignment of Purkinje cells, and an increase in the water content in the brain. Brain extract and serum of tumor-bearing mice showed higher levels of proinflammatory cytokines. Induction of apoptosis is suggested to be the cause underlying the loss of cellularity of tumor-bearing hosts in the brain owing to an augmentation in the induction of the caspase-dependent pathway of programmed cell death. Further, the study presents investigations to show the role of nitric oxide and proinflammatory cytokines IL-1, TNF, interferon-γ and alkaline phosphatase in the manifestation of paraneoplastic neurodegeneration. Conclusions: Growth of a T-cell lymphoma is associated with the manifestation of neurodegeneration caused by soluble proinflammatory factors of tumor and/or host origin.

Bioluminescence Imaging of Spontaneous Lymphomas and Contribution of Distinct NFκB Pathways.

The nuclear factor κB (NFκB) pathways have been implicated in tumorigenesis in several lymphoid malignancies, but the responsible mechanisms remain to be fully defined. EBV and HTLV-1 immortalized lymphoma cell lines with constitutively active NFκB were found to be resistant to inducers of the extrinsic and intrinsic apoptosis pathways. Several NFκB-target genes were over-expressed in these cell lines, including Bcl-xL, Fas-associated death domain-like IL-1β converting enzyme inhibitor protein (FLIP), and inhibitors of apoptosis (CIAP, XIAP, and survivin). Inhibition of the canonical or non-canonical NFκB pathways with small interfering RNAs (siRNA) or adenovirus expressing a stable form of inhibitor of NFκB (IκB) enhanced sensitivity to apoptosis inducers, and resulted in lower levels of expression these NFκB target genes. Repression of XIAP with siRNA was particularly potent in enhancing apoptosis sensitivity. These findings demonstrate an important role of both NFκB pathways in mediating resistance to apoptosis, and distinctive anti-apoptotic downstream target gene profiles responsible for this effect. In order to utilize HTLV-1 Tax activity as an in vivo biomarker for tumorigenesis, we generated transgenic mice with firefly luciferase driven by the HTLV-1 long terminal repeat (LTRLUC) and bred them with the GzBTax animals to produce double transgenic LTRLUC/GzBTax (LLT) mice which develop large granular lymphocytic leukemia, splenomegaly, localized bone destruction, and solid tumors of the ears, legs, nose, and tail. We found that the bioluminescence of the LLT miceserves as a reporter for spontaneous tumorigenesis in vivo,is transferable as a useful tumor marker in cell culture and allograft models derived from primary tumors,is inducible by immunomodulatory agents, andis a sensitive indicator for even the earliest events in tumor development.

Antitumor Effects by Low Dose Total Body Irradiation

Total-body irradiation (TBI) with 0.02-0.25 Gy has been reported to have antitumor effects. In mice, low-dose TBI induces tumor growth delay, antimetastatic effects, suppressive effects on the incidence of spontaneous thymiclymphoma, sensitization of tumor to ionizing radiation, and decrease in TD50 value. In artificial metastasis, 0.20 Gy TBI suppressed lung metastasis when it was conducted between 3 h before and 3 h after tumor cell injection into a tail vein. In spontaneous metastasis, 0.15-0.20 Gy TBI suppressed lung metastasis. Irradiation with 0.15 Gy twice a week from 11 weeks of age for 40 weeks significantly suppressed the incidence of spontaneous thymic lymphoma in AKR/J mice, which caused prolonged life span. Low-dose TBI has been used in the clinical treatment of lymphomatous malignancies including chronic lymphocytic leukaemia (CLL) and non-Hodgkin's lymphoma (NHL). The usual practice was to give 0.1 Gy TBI three times a week or 0.15 Gy TBI two times a week to a total dose of 1.5 Gy. Despite this low total dose, low-dose fractionated TBI could induce long-term remissions and was as effective as the chemotherapy to which it was compared. Experimental data suggest that the antitumor effects of low-dose TBI could be explained by immune enhancement, induction of apoptosis, and intrinsic hypersensitivity to low-dose irradiation. Possible mechanisms of immune enhancement are elimination of the T-suppressor subset of lymphocytes and augmentation of the immune response including alteration of cytokine release and enhanced proliferative activity of lymphocytes to mitogenic stimuli.

Mouse lymphomas caused by an intron-splicing donor site deletion of the FasL gene

A spontaneous lymphoma was detected in mice, which was caused by a recessive autosomal mutation. The genetic basis was revealed to be a 5-bp deletion at the splicing donor site of the first intron of the FasL gene, resulting in aberrant transcripts coding for non-functional proteins. This mutation of the FasL gene caused development of lymphoma in all four mouse genetic backgrounds tested and the lymphoma was characterized by an expansion of leucocytes that were TCR +CD3 +B220 +CD19 −CD4 −CD8 −. Accordingly, severe splenomegaly developed in the mutant mice. Interestingly, thymic hyperplasia was observed in mutant mice at later stages. These results underscore the functional importance of the splicing donor site in the function of the FasL gene and provide an independent evidence for a role of FasL in normal development of lymophocytes. The mutant mice offer another genetically defined mouse model for further studies of the role and mechanism of action of FasL.

Loss of Ubr1 promotes aneuploidy and accelerates B-cell lymphomagenesis in TLX1/HOX11-transgenic mice

The TLX1/HOX11 homeobox gene was originally identified at the recurrent t(10;14)(q24;q11) translocation breakpoint, a chromosomal abnormality observed in 5-7% of T-cell acute lymphoblastic leukemias (T-ALLs). Proviral insertional mutagenesis studies performed on transgenic mice ectopically expressing TLX1/HOX11 in B lymphocytes (IgHmu-HOX11(Tg) mice) revealed the Ubr1 gene locus as a frequent site of proviral insertion, concomitant with accelerated development of diffuse large B-cell lymphoma. Insertion into this genomic region was confirmed by Southern blotting and by the ability to generate a polymerase chain reaction (PCR) amplicon across the viral-genome junction. Western immunoblot and semiquantitative reverse transcriptase-PCR analysis revealed downregulated expression of the Ubr1 gene product subsequent to viral integration. Loss or reduced levels of Ubr1 expression was associated with 5/14 spontaneous B-cell lymphomas in IgHmu-HOX11(Tg) mice and one of nine primary human T-ALLs. To gain mechanistic insight into the cooperativity between TLX1/HOX11 and Ubr1, IgHmu-HOX11(Tg)/Ubr1(-/-) mice were generated. IgHmu-HOX11(Tg)/Ubr1(-/-) mice exhibited a modest but statistically significant acceleration of disease onset relative to IgHmu-HOX11(Tg)/Ubr1(+/-) mice. Moreover, micronucleus assays to detect for chromosome missegregation were conducted and revealed increased presence of micronuclei in IgHmu-HOX11(Tg)/Ubr1(-/-) primary B lymphocyte cultures, and in both TLX1/HOX11-overexpressing T cell lines and fibroblast cultures following transfection with short interfering RNAs (siRNAs) targeting Ubr1. Karyotyping of primary B lymphocyte cultures revealed increased incidences of hypodiploid karyotypes. Finally, mitotic figures analysed from Ubr1 siRNA-transfected fibroblast cultures revealed no defects in chromosome congression to the metaphase plate, but increased incidences of atypical anaphase figures, including the development of anaphase bridges and lagging chromosomes. Based on these findings, we identify a synergistic role between TLX1/HOX11 overexpression and Ubr1 inactivation in promoting chromosome missegregation, permitting the accrual of additional chromosome losses and cytogenic abnormalities en route to malignancy.

Accelerated growth of intestinal tumours after radiation exposure in Mlh1‐knockout mice: evaluation of the late effect of radiation on a mouse model of HNPCC

Mlh1-knockout mice have been developed as a useful model of hereditary non-polyposis colorectal cancer (HNPCC). In this study, we analyzed the pathology of gastrointestinal tumours (GIT) in these mice in detail and examined the possible effects of ionizing radiation on the induction of intestinal tumours to evaluate the late response to radiotherapy in HNPCC. Mlh1-/- mice spontaneously developed GIT and thymic lymphomas by 48 weeks. GIT included not only well differentiated adenocarcinomas but also poorly differentiated and mucinous adenocarcinomas, suggesting that this mouse is a good model for HNPCC. In contrast to colon cancers from HNPCC patients, however, carcinomas of Mlh1-/- mice expressed p53 and showed a lack of transforming growth factor (TGF)-betaRII mutation, which resulted in the expression of TGF-betaRII protein. Irradiation of 10-week-old Mlh1-/- mice accelerated GIT development but had little effect at 2 weeks. Mlh1+/- and Mlh1+/+ mice were not susceptible to spontaneous or radiation-induced thymic lymphomas and GIT until 72 weeks after birth. The development and pathology of GIT in Mlh1-/- mice suggest that this mouse is a good model for HNPCC, although tumour-related responsible genes might be different from HNPCC. As X-ray exposure promoted carcinogenesis of GIT in adult Mlh1-/- mice, an increased risk of secondary cancers after radiotherapy for HNPCC patients should be taken into consideration.

Spontaneous Lymphoma in a Prairie Dog (Cynomys ludovicianus)

A 4-year-old, female, black-tailed prairie dog (Cynomys ludovicianus) was examined for acute dyspnea and two skin masses. Tentative diagnosis of lymphoma was made based on cytology of pleural effusion and the skin masses. Administration of prednisolone was initially effective in improving the condition; however, the clinical signs deteriorated after radiation therapy and administration of cyclophosphamide. Postmortem examination revealed that neoplastic lymphocytes had infiltrated most of the organs, and the histopathological diagnosis was multi-centric lymphoma.

Tumorigenic activity of p21Waf1/Cip1 in thymic lymphoma

The cell cycle inhibitor p21Waf1/Cip1 is among the most important mediators of the tumor suppressor p53. However, there is increasing evidence indicating that p21 could favor tumorigenesis in specific cell types. In particular, the absence of p21 delays the development of thymic lymphomas induced either by ataxia-telangiectasia mutated deficiency or by ionizing irradiation. Here, we extend these observations to the context of p53-deficient mice. The absence of p21 results in a significant extension of the lifespan of p53-null and p53-haploinsufficient mice, and this effect can be attributed exclusively to a decrease in the incidence of spontaneous thymic lymphomas. Specifically, despite the occurrence of a variety of tumor types in the context of p53 deficiency, the only tumors that were significantly impaired by the absence of p21 were thymic lymphomas. Moreover, the absence of p21 also delays the incidence of radiation-induced thymic lymphomas in p53-deficient mice. Interestingly, p21-deficient lymphomas have a higher apoptotic rate than p21-proficient lymphomas, and this could be on the basis of the delayed incidence of thymic lymphomas in the absence of p21. Together, our results indicate that p21 plays an oncogenic role restricted to thymic lymphomas that is mechanistically independent of p53 and associated to a lower tumor apoptotic rate.

Syntheses of Base and Side-Chain Modified Pyrimidine 1-[2-(Phosphonomethoxy)propyl] Derivatives as Potent Inhibitors of Thymidine Phosphorylase (PD-ECGF) from SD-Lymphoma

In this study we synthesized a series of thymine and 5-ethyluracil acyclic nucleoside phosphonates bearing hydroxymethyl, methoxymethyl, azidomethyl, aminomethyl and (trimethylammonio)methyl group in side chain as potent inhibitors of thymidine phosphorylase. In addition, we investigated in particular the novel syntheses of fluorinated derivatives containing fluoromethyl or trifluoromethyl groups in side chain such as 5-ethyl- 1-[(S)-3-fluoro-2-(phosphonomethoxy)propyl]uracil (8) or 5-ethyl-1-[3,3,3-trifluoro-2-(phosphonomethoxy)propyl]uracil and thymine derivatives 27 and 28. Uracil acyclic nucleoside phosphonates 1-{2-[(diisopropoxyphosphoryl)methoxy]ethyl}uracil (12) and 1-{2-[(diisopropoxyphosphoryl)methoxy]-3,3,3-trifluoropropyl}uracil (19) were fluorinated to corresponding 5-fluorouracil derivatives. While the 5-fluorouracil derivatives exhibit a marginal inhibitory effect, thymine and 5-ethyluracil compound with fluorine in side chains possess considerable inhibitory potency toward thymidine phosphorylase from rat spontaneous T-cell lymphoma.

Iron-Radiofrequency Synergism in Lymphomagenesis

The parenteral iron administration effects on the acceleration of lymphomagenesis by radiofrequency exposure were investigated using an animal model that develops spontaneous lymphomas with ageing. Complementary studies of the in vivo uptake of 59Fe-labeled ferric gluconate and ferric-ATP complex showed differences ob absorption and excretion between both iron compounds. In vitro assays of their effects on calcium cellular uptake using a cell model and tissues homogenates showed a molecular structure-dependence. The current results (mortality, clinical and histopathological examinations) demonstrated a synergism between radiofrequency and ferric gluconate, and the increased risk of radiofrequency exposure when it is simultaneous to parenteral iron administration.

A marine fish diet reduces spontaneous lymphoma in outbred Swiss-Webster mice

Diets rich in marine organisms or their oils are known to suppress solid tumor development in humans and rodents, but the potential for marine foods to affect hematopoietic system cancers is not well understood. As part of a toxicology study, we fed groups of mice three different diets for 10 weeks: marine fish, 58% homogenized Atlantic smelt and herring; freshwater fish, 58% smelt and alewife from the North American Great Lakes, and commercial dry rodent chow. Between 1 and 15 weeks following dietary treatment, 20 of 103 (19.4%) mice unexpectedly developed spontaneous lymphoma. Disease incidence peaked when the mice were 7–8 months old, and was not distributed equally across treatment groups. Mice in the control (30%) and fresh water fish (27.5%) groups had significantly higher incidences of lymphoma than those fed Atlantic fish species (5%). Although our experiment was not originally designed for this purpose, our results indicate that consumption of fat-rich Atlantic smelt and herring protected mice against hematopoietic tumor development.

A Phase 2 Study of the Thrombospondin-Mimetic Peptide ABT-510 in Patients with Refractory Lymphoma.

ABT-510 is a potent nonapeptide that mimics the antiangiogenic activity of the endogenous protein, thrombospondin-1. Dogs with spontaneous lymphoma showed a response rate of 17% (4/23). In 2 phase 1 studies in patients with solid tumors, ABT-510 was tolerated at doses up to 260 mg per day. Doses ≥20 mg daily exceeded the pharmacokinetic target of 100 ng/mL for >3 hours. 67 patients with relapsed or refractory lymphoma were randomized to receive ABT-510 10 mg or 100 mg twice daily (BID) by subcutaneous injection. The 10 mg BID arm was discontinued after 15 patients were enrolled to consolidate recruitment to the higher dose. The primary endpoint was tumor response; secondary endpoints included progression-free survival (PFS) and overall survival. Tumor progression was evaluated every 8 weeks by the Cheson criteria; safety was evaluated every 4 weeks. 6 of the 67 patients remain on active therapy. Data are available for 56 patients (32M/24F); the median age is 63 years (range 22–87), and the baseline ECOG Performance Score for all patients ranges from 0–2. All patients were heavily pretreated, with a median of 5 prior treatments (range 1–11). There are 3 partial responses, all in the 100 mg dose group in non-Hodgkins lymphoma (NHL) patients. PFS data are as follows:Patient GroupN6-month PFS % (90 % CI)12 month PFS % (90 % CI)All5641 (28, 53)17 (3, 31)10 mg BID1534 (11, 56)0100 mg BID3848 (33, 64)24 (8, 41)Hodgkins1129 (3, 55)0NHL4544 (30, 58)22 (4, 40)Aggressive1729 (9, 49)0Indolent2751 (33, 70)36 (16, 56)The most frequent adverse events (AEs) were asthenia (39%), injection site reaction (39%), diarrhea (24%), and anorexia (20%). 19% of patients had Grade 3–4 AEs considered related to ABT-510: anemia (4), thrombocytopenia (2), asthenia, chest pain, hemorrhage, gastrointestinal hemorrhage, leukopenia, and hypercalcemia (1 each). Correlative analyses of circulating endothelial cell data are pending. Based on these preliminary data, ABT-510 appears well-tolerated with biological activity in heavily pretreated patients with lymphoma. Study of ABT-510 in combination with immunotherapy or standard chemotherapy is warranted.

Genomic instability in radiation-induced mouse lymphoma from p53 heterozygous mice

Although radiation can directly induce DNA damage and is a known human and animal carcinogen, the number of genetic changes in radiation-induced tumors, and the pathways responsible for generating them, are unknown. We have used high-density BAC arrays covering >95% of the mouse genome for analysis of genomic patterns of aberrations in spontaneous and radiation-induced mouse lymphomas. The majority of radiation-induced tumors exhibit one of three 'signatures' based on gene copy number changes. Some exhibit extensive scrambling of the genome, with very high numbers of recurrent gains and losses. Two other signatures are characterized by excess gains but relatively few losses, or vice versa. Changes in spontaneous tumors often involve whole chromosomes, whereas radiation-induced tumors exhibit a high frequency of localized deletion/amplification events. The number of copy number abnormalities does not correlate with the latency or pathology of the tumors. We propose that specific early events following radiation exposure induce changes in 'caretaker' genes that control specific downstream pathways involved in DNA damage repair. The nature of these early events may determine the overall genomic signature observed in the resulting tumor.

Antitumor Activation of Peritoneal Macrophages by Thymosin Alpha-1

It was been previously reported that thyα1 can be used to activate monocytes, BMDM and TAM. However, the effect of thyα1 on other tissue macrophages has not been investigated. Moreover, there is no report about the use of thyα1-treated macrophages in adoptive immunotherapy of cancer. In view of these observations in the present study, we checked the response of various tissue macrophages to thyα1 for activation. Tissue macrophages showed differential response to thyα1; moreover, adoptive transfer of peritoneal macrophages treated with thyα1 to mice bearing spontaneous T-cell lymphoma designated as Dalton's lymphoma (DL) resulted in the prolongation of the survival time of tumor-bearing mice. The mechanism of macrophage therapy-dependent tumor regression was enhanced antitumor activity of macrophages in response to thyα1 treatment via their production of macrophage-activating cytokines that act in autocrine manner. These results will help in the development of immunotherapy against tumor based on activation of macrophage with thyα1.

Inhibition of thymidine phosphorylase (PD-ECGF) from SD-lymphoma by phosphonomethoxyalkyl thymines

A series of thymine phosphonomethoxyalkyl derivatives were evaluated for their ability to inhibit thymidine phosphorylase (dThdPase) purified from rat spontaneous T-cell lymphoma. A kinetic study of thymidine phosphorolysis catalyzed by dThdPase was performed with thymidine and/or inorganic phosphate as substrates. Data show that the substantial inhibitory effect of these acyclic nucleotide analogues is decreasing in the order of ( R)-FPMPT > ( S)-FPMPT ≥ ( R)-HPMPT > ( S)-PMPT > ( S)-HPMPT > PMET ≥ ( R)-PMPT. The inhibitory potency ( K i/ dThd K m) of the most efficient inhibitors from this series against T-cell lymphoma enzyme is 0.0026 for ( R)-FPMPT and 0.0048 for ( S)-FPMPT. The studied compounds do not inhibit Escherichia coli and human enzyme and possess lower inhibitory potency against rat liver thymidine phosphorylase.