tetrahydrouridine and Lung-Neoplasms

Tetrahydrouridine (THU) is a well characterized and potent inhibitor of cytidine deaminase (CDA). Highly expressed CDA catalyzes and inactivates cytidine analogues, ultimately contributing to increased gemcitabine resistance. Therefore, a combination therapy of THU and gemcitabine is considered to be a potential and promising treatment for tumors with highly expressed CDA. In this study, we found that THU has an alternative mechanism for inhibiting cell growth which is independent of CDA expression. Three different carcinoma cell lines (MIAPaCa-2, H441, and H1299) exhibited decreased cell proliferation after sole administration of THU, while being unaffected by knocking down CDA. To investigate the mechanism of THU-induced cell growth inhibition, cell cycle analysis using flow cytometry was performed. This analysis revealed that THU caused an increased rate of G1-phase occurrence while S-phase occurrence was diminished. Similarly, Ki-67 staining further supported that THU reduces cell proliferation. We also found that THU regulates cell cycle progression at the G1/S checkpoint by suppressing E2F1. As a result, a combination regimen of THU and gemcitabine might be a more effective therapy than previously believed for pancreatic carcinoma since THU works as a CDA inhibitor, as well as an inhibitor of cell growth in some types of pancreatic carcinoma cells.

Topics: Cell Cycle Checkpoints; Cell Line, Tumor; Cell Proliferation; Cytidine Deaminase; Deoxycytidine; Enzyme Inhibitors; Gemcitabine; Humans; Lung Neoplasms; Pancreatic Neoplasms; Tetrahydrouridine

The study's goals were as follows: (1) to extend our past findings with rodent tumors to human tumors in nude mice, (2) to determine if the drug protocol could be simplified so that only CldC and one modulator, tetrahydrouridine (H4U), would be sufficient to obtain efficacy, (3) to determine the levels of deoxycytidine kinase and dCMP deaminase in human tumors, compared to adjacent normal tissue, and (4) to determine the effect of CldC on normal tissue radiation damage to the cervical spinal cord of nude mice.. The five human tumors used were as follows: prostate tumors, PC-3 and H-1579; glioblastoma, SF-295; breast tumor, GI-101; and lung tumor, H-165. The duration of treatment was 3-5 weeks, with drugs administered on Days 1-4 and radiation on Days 3-5 of each week. The biomodulators of CldC were N-(Phosphonacetyl)-L-aspartate (PALA), an inhibitor of aspartyl transcarbamoylase, 5-fluorodeoxycytidine (FdC), resulting in tumor-directed inhibition of thymidylate synthetase, and H4U, an inhibitor of cytidine deaminase. The total dose of focused irradiation of the tumors was usually 45 Gy in 12 fractions.. Marked radiosensitization was obtained with CldC and the three modulators. The average days in tumor regrowth delay for X-ray compared to drugs plus X-ray, respectively, were: PC-3 prostate, 42-97; H-1579 prostate, 29-115; glioblastoma, 5-51; breast, 50-80; lung, 32-123. Comparative studies with PC-3 and H-1579 using CldC coadministered with H4U, showed that both PALA and FdC are dispensable, and the protocol can be simplified with equal and possibly heightened efficacy. For example, PC-3 with X-ray and (1) no drugs, (2) CldC plus the three modulators, (3) a high dose of CldC, and (4) escalating doses of CldC resulted in 0/10, 3/9, 5/10, and 6/9 cures, respectively. The tumor regrowth delay data followed a similar pattern. After treating mice only 11/2 weeks with CldC + H4U, 92% of the PC-3 tumor cells were found to possess CldU in their DNA. The great majority of head-and-neck tumors from patient material had markedly higher levels of dC kinase and dCMP deaminase than found in adjacent normal tissue. Physiologic and histologic studies showed that CldC + H4U combined with X-ray, focused on the cervical spinal cord, did not result in damage to that tissue.. 5-CldC coadministered with only H4U is an effective radiosensitizer of human tumors. Ninety-two percent of PC-3 tumor cells have been shown to take up ClUra derived from CldC in their DNA after only 11/2 weeks and 2 weeks of bolus i.p. injections. Enzymatic alterations that make tumors successful have been exploited for a therapeutic advantage. The great electronegativity, coupled with the relatively small Van der Waal radius of the Cl atom, may result in CldC's possessing the dual advantageous properties of FdC on one hand and BrdU and IdU on the other hand. These advantages include autoenhancing the incorporation of CldUTP into DNA by not only overrunning but also inhibiting the formation of competing TTP pools in tumors. A clinical trial is about to begin, with head-and-neck tumors as a first target of CldC radiosensitization.

Topics: Animals; Breast Neoplasms; Carcinoma, Squamous Cell; Combined Modality Therapy; DCMP Deaminase; Deoxycytidine; Deoxycytidine Kinase; Female; Glioblastoma; Humans; Lung Neoplasms; Male; Mice; Mice, Nude; Neoplasm Proteins; Neoplasms; Prostatic Neoplasms; Radiation-Sensitizing Agents; Radiotherapy Dosage; Spinal Cord; Tetrahydrouridine

The metabolic products formed and incorporated into the nucleic acids (RNA and DNA) of mice bearing Lewis lung carcinoma (LLC) following optimal doses of 5-fluorouracil (FUra), 5-fluoro-2'-deoxyuridine (FdUrd), and 5-fluoro-2'-deoxycytidine (FdCyd) coadministered with tetrahydrouridine (H4Urd), a potent inhibitor of cytidine deaminase, were examined. Treatment with FdCyd plus H4Urd resulted in a tumor-selective incorporation and formation of antimetabolites compared to either FUra or FdUrd treatments. Between 45- and greater than 5400-fold higher levels of the potent thymidylate synthetase inhibitor, 5-fluoro-2'-deoxyuridylate (FdUMP), were formed in tumor than in any of the normal tissues analyzed. RNA-level antimetabolites (FUra, 5-fluorouridine, and 5-fluorouridylate) were also between 3 and greater than 990-fold higher in tumor compared to normal tissue following FdCyd plus H4Urd administration. DNA-level antimetabolites (FdCyd, 5-fluorodeoxycytidylate, FdUrd, and FdUMP) were from 2- to 6-fold higher in tumor compared to normal tissue. FUra and FdUrd treatments resulted in between 3 and greater than 1300-fold higher RNA-level antimetabolites and from 4 to greater than 1020-fold higher FdUMP pools in normal tissues than FdCyd plus H4Urd treatment. DNA-level antimetabolites were also from 4- to 32-fold higher in normal tissues following optimal doses of FUra or FdUrd. In tumor tissue, optimal doses of FUra or FdUrd resulted in lower (a) FdUMP levels (5- to 2-fold), (b) RNA-level antimetabolites (6- to 3-fold), and (c) DNA-level antimetabolites (10- to 4-fold) compared to an optimal dosage of FdCyd plus H4Urd. In serum, the administration of H4Urd resulted in the protection of FdCyd from systemic catabolism, unlike that found with FUra or FdUrd. Substantial levels of FdUMP, FUrd, and FUMP were noted in serum following FUra or FdUrd treatment. The formation of di- and triphosphate antimetabolite pools and the incorporation of antimetabolites into the RNA and DNA of normal and tumor tissues demonstrated trends similar to those mentioned above with nucleoside, mononucleotide, and free base pools. H4Urd treatment of 25 mg/kg did not affect the elevated levels of deoxycytidine kinase or deoxycytidylate deaminase in LLC tumor tissue or the low levels found in normal tissue. A critical feature of this chemotherapeutic strategy using FdCyd plus H4Urd was that the elevated level of cytidine deaminase in LLC tumor tissue was inhibited less than 10% by the administ

Topics: Animals; Antimetabolites; Deoxycytidine; Female; Floxuridine; Fluorouracil; Lung Neoplasms; Mice; Tetrahydrouridine; Uridine

In view of the 20- to 80-fold elevation of deoxycytidine-5'-phosphate (dCMP) deaminase in many human malignant tumors, we have utilized 5-fluorodeoxycytidine ( FdCyd ) coadministered with tetrahydrouridine ( H4Urd ) as a combination of antitumor agents against two murine solid tumors which possess high levels of dCMP deaminase. This approach is based on our past studies in which we demonstrated that FdCyd is an excellent substrate for mammalian 2'-deoxycytidine kinase, and that H4Urd increases the toxicity of FdCyd in the mouse. Cell culture studies utilizing 2'- deoxytetrahydrouridine which inhibits cytidine deaminase and as 2'- deoxytetrahydrouridine -5'-monophosphate inhibits dCMP deaminase, provide indirect evidence for the pathway that we had proposed in the past, 2'- Deoxytetrahydrouridine antagonized the toxicity of FdCyd to a greater extent than did H4Urd and showed marked antagonism in cytidine deaminase-deficient cells. Cell lines lacking both cytidine and 2'-deoxycytidine-5'-monophosphate deaminase were markedly resistant to FdCyd . Thymidine and deoxyuridine antagonized toxicity in a manner consistent with the proposed pathway of anabolism of FdCyd and consistent with its resulting in the inhibition of thymidylate synthetase. We have established the efficacy of FdCyd + H4Urd chemotherapy utilizing adenocarcinoma 755 and Lewis lung carcinoma in C57BL X DBA/2 F1 mice. An example of an optimum schedule versus Lewis lung carcinoma is FdCyd , 10 to 12 mg/kg, plus H4Urd , 25 mg/kg, coadministered simultaneously, once per day on Days 1 to 7 after tumor implantation. Tumor inhibitions on Days 12, 14, and 16 were 95, 90, and 80%, respectively, with 8% maximum weight loss. Comparative studies were undertaken only with Lewis lung carcinoma and it was established that FdCyd + H4Urd surpasses the efficacies of 5-fluorouracil and 5-fluorodeoxyuridine as well as FdCyd when administered without H4Urd . We propose that the administration of FdCyd with H4Urd can result in preferential, tumor-directed conversion of a nontoxic nucleoside analogue to a toxic antimetabolite by an enzyme that is markedly elevated in human tumor tissue. The analogues of deoxycytidine are resistant to catabolism and are anabolized by a different subset of enzymes than are 5-fluorouracil or 5-fluorodeoxyuridine; therefore, it is a novel approach. Not only are there intrinsic selectivity, metabolic stability, and the advantages that accrue from prodrug therapy in this strategy, but in a

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Carcinoma, Ehrlich Tumor; Carcinoma, Squamous Cell; Cell Line; Cell Survival; Cricetinae; Cricetulus; DCMP Deaminase; Deoxycytidine; DNA Replication; Drug Evaluation, Preclinical; Female; Humans; Leukemia L1210; Leukemia, Experimental; Lung Neoplasms; Mammary Neoplasms, Experimental; Mice; Nucleotide Deaminases; Ovary; Tetrahydrouridine; Uridine

Thirteen experimental mouse neoplasms were tested by cytidine (CR)-deaminase and deoxycytidine (dCR)-kinase levels. Four neoplasms, Sarcoma T241, Adenocarcinoma E0771, Lewis lung carcinoma (LL), and Sarcoma 180 Japan (S180J), considered to have high deaminase and sufficient dCR-kinase activities, were tested in vivo for combination chemotherapy with cytosine arabinoside (ara-C) and the CR-deaminase inhibitor, tetrahydrouridine (THU). THU did not significantly improve the growth inhibition of ara-C in a wide range of combinations in T241, E0771, LL, and the solid form of S180J, but more than doubled the survival time of the S180J ascites-bearing animals. Toxicity in the form of weight loss and toxic deaths was observed in some but not all groups, especially at high dosages of ara-C and THU. Tissue distribution of [3H]-ara-C and [14C]-THU in T241-bearing mice revealed an accelerated clearance of ara-C-derived radioactivity under the influence of THU in the tumor and five host tissues, but not in the small intestines. With the exception of the small intestines, clearance of THU-derived radioactivity was faster in all tissues studied compared to the clearance of [3H]-ara-C-derived radioactivity. Intracellular CR-deaminase levels were inhibited significantly, ie, dose dependent, in tumor and host kidney after a single ip injection of THU to E0771--bearing mice. In the solid S180J, with or without simultaneous ip administration of THU, [3H]-ara-C was not converted to 5'-di- and tri-phosphates at all. In mice bearing the ascites form of S180J, [3H]-ara-C was extensively converted to ara-C 5'-di- and tri-phosphates. THU increased both overall ara-C-derived radioactivity and the relative amounts of ara-C 5'-di- and tri-phosphates.

Topics: Adenocarcinoma; Animals; Cytarabine; Cytidine Deaminase; Deamination; Drug Evaluation; Drug Therapy, Combination; Female; Lung Neoplasms; Mice; Neoplasms, Experimental; Phosphotransferases; Sarcoma, Experimental; Tetrahydrouridine; Tritium; Uridine

Extracts of solid mouse tumors were examined for deoxycytidine kinase and deaminase activities. 1beta-D-Arabinofuranosylcytosine nucleotide was formed at a rate of 45 nmoles/hr by Glioma 26/57 and only 14 nmoles/hr by Ridgway osteogenic sarcoma. Deaminase activity was highest in Lewis lung (114 nmoles of 1-Beta-D-arabinofurano-syluridine formed per hr) and in CaD2 (104 nmoles of u-beta-D-arabinofuranosyluridine formed per hr). Deaminase activity in tumor extracts is sensitive to freezing, while deaminase activity in monkey serum is not. It was observed that kinase activity varies by as much as 50% in different cell lines of the same tumor. In the presence of tetrahydrouridine, kinase activity was significantly increased in most of the tumors studied.

Topics: Adenocarcinoma; Aminohydrolases; Animals; Cell Line; Chick Embryo; Cytarabine; Freezing; Glioma; Lung Neoplasms; Mammary Neoplasms, Experimental; Melanoma; Mice; Mice, Inbred AKR; Mice, Inbred C3H; Mice, Inbred C57BL; Mice, Inbred DBA; Neoplasms, Experimental; Osteosarcoma; Phosphotransferases; Pyrimidine Nucleotides; Sarcoma 180; Tetrahydrouridine; Uridine

The phosphorylation of 1-beta-D-arabinofuranosylcytosine (ara-C) was studied in cell-free extracts from a variety of solid mouse tumors, L1210 ascites and in normal liver and spleen. Two apparent Michaelis constants were observed for kinase activity in Lewis lung (Km1, 4.15 muM; Km2 58.1 muM), sarcoma 180 (Km1 6.66 muM; Km2 56.18 muM), adenocarcinoma 755 (Km1 4.34 muM; Km2 50.0 muM) and l1210 (Km1 29.41 muM; Km2 41.67 muM). The Km1 values generally ranged from 5 to 20 muM 3H-ara-C while the Km2 values ranged from 20 to 60 muM 3H-ara-C. Normal spleen (Km 47.6 muM), normal liver (Km 10.0 muM) and Ridgway osteogenic sarcoma (Km 31.2 muM) had single Km values. In the presence of tetrahydrouridine (H4U), the in vitro phosphorylation of ara-C was increased as much as 91% in cell-free extracts from adenocarcinoma 755; lesser increases were observed in other tumor extracts. At low substrate concentrations, the apparent Km decreased or did not change in the presence of H4U, while at higher substrate concentrations the apparent Km was increased or did not change in the presence of H4U. In the presence of H4U, Vmax for kinase activity increased most in those tumors possessing deaminase activity.

Topics: Adenocarcinoma; Animals; Bone Neoplasms; Cytarabine; Cytidine Deaminase; Deoxycytidine; Female; In Vitro Techniques; Kinetics; L Cells; Liver; Lung Neoplasms; Male; Mice; Neoplasm Transplantation; Neoplasms, Experimental; Osteosarcoma; Phosphorus; Phosphotransferases; Sarcoma 180; Spleen; Tetrahydrouridine; Uridine