The induction of ornithine decarboxylase activity and its control in mouse skin epidermis

Peripheral blood leucocytes ornithine decarboxylase activity in chronic myeloid leukemia patients: prognostic and therapeutic implications

Leukocytes ornithine decarboxylase (ODC) activity was measured in normal individuals and in patients with chronic myeloid leukemia (CML) in chronic phase (CML-CP) as well as in accelerated phase (CML-AP), with an aim to examine the role of ODC activity in prognostic evaluation of CML patients. Our results showed that ODC activity was significantly higher in CML-CP (41.02+/-25.57nmol/h per 10(7) cells, P<0.005) and CML-AP (67.71+/-44.42nmol/h per 10(7) cells, P<0.001) patients than in normal subjects (3.12+/-1.34nmol/h per 10(7) cells). Furthermore, patients with CML-AP showed higher ODC activity than CML-CP patients (P<0.005). Patients with CML-CP who converted to accelerated phase within 24 months had higher ODC activity (84.58+/-12.81nmol/h per 10(7) cells) than patients who did not convert to accelerated phase (31.13+/-18.24nmol/h per 10(7) cells). The high value of ODC activity was also associated with less clinico-hematological response. We suggest that ODC activity reflects the neoplastic proliferative activity in CML patients and may serve as an additional prognostic marker.

A definitive role of ornithine decarboxylase in photocarcinogenesis

Excessive exposure of solar ultraviolet (UV) radiation, particularly its UVB component, to human skin is the major cause for more than a million new cases of cutaneous malignancies diagnosed annually in the United States. Photocarcinogenesis, like other cancers, is a multistep process that includes initiation and promotion. A proper understanding of the molecular events occurring during the tumor promotion phase of photocarcinogenesis could lead to the development of novel approaches for the management of skin cancer. Using a transgenic mouse model (K5/ODC mice), which overexpresses the enzyme ornithine decarboxylase (ODC) in hair follicle keratinocytes, we studied the role of this gene in photocarcinogenesis. A single UVB-exposure of 180 mJ/cm(2) to the transgenic mice resulted in a minimal increase in bifold skin thickness and ODC activity. However, in SKH-1 hairless mice, the most common and highly sensitive model for photocarcinogenesis, and in littermate nontransgenic mice, increases in skin thickness and ODC activity were substantial. In long-term experiments, mice were exposed to 180 mJ/cm(2) of UVB radiation three times a week for 2 weeks (tumor-initiating dose). At 30 weeks after this treatment, in two independent experiments, 40% of the K5/ODC transgenic mice exposed to UVB were found to develop epidermal tumors. The tumors were histologically verified as benign papillomas and squamous cell carcinomas. Interestingly, 100% of the transgenic mice also developed >20 pigmented cysts/mouse, which contained keratinocyte material with increased keratinocytic melanization. Under similar UVB-exposure protocol, the nontransgenic littermates or SKH-1 hairless mice did not develop tumors or pigmented cysts for up to 50 weeks. Oral consumption of alpha-difluoromethylornithine, an irreversible specific inhibitor of ODC, in the drinking water (1% w/v) to the transgenic mice resulted in complete prevention of UVB-mediated tumorigenesis and a substantial decrease in the formation of pigmented cysts (<10 per mouse). These data establish a definitive role of ODC in the promotion phase of photocarcinogenesis.

The importance of L-arginine metabolism in melanoma: an hypothesis for the role of nitric oxide and polyamines in tumor angiogenesis

There is a worldwide increase in the incidence of melanoma. Without treatment, melanomas can progress to metastatic disease and result in death. It is now accepted that for a tumor to grow, non-tumorous host tissue must form blood vessels in and around the tumor. Tumor cells and blood vessels must form a highly regulated system whereby endothelial cells can be switched from a resting state to one of rapid growth. Tumor cells have been shown to produce diffusible angiogenic regulatory molecules. Nitric oxide [NO] and polyamines [PA] have been implicated in the angiogenic process. This paper hypothesizes that NO and PA regulate melanoma angiogenesis differently. During early stages of malignant melanoma an increase in PA synthesis is expected to promote endothelial cell proliferation and therefore angiogenesis. NO is expected to be maintained at low levels. During the vascular stage of malignant melanoma, NO synthesis is hypothesized to be elevated which will decrease endothelial cell proliferation and maintain a vasodilator tone in and around the tumor. PA concentrations are expected to be lower. A regulatory link between NO and PA may be involved in the maintenance of tumor homeostasis. The regulation of L-arginine metabolism in tumor angiogenesis requires investigation as it may lead to novel selective therapeutic interventions in cancer therapy.

Metabolism and action of amino acid analog anti-cancer agents

The preclinical pharmacology, antitumor activity and toxicity of seven of the more important amino acid analogs, with antineoplastic activity, is discussed in this review. Three of these compounds are antagonists of L-glutamine: acivicin, DON and azaserine; and two are analogs of L-aspartic acid: PALA and L-alanosine. All five of these antimetabolites interrupt cellular nucleotide synthesis and thereby halt the formation of DNA and/or RNA in the tumor cell. The remaining two compounds, buthionine sulfoximine and difluoromethylornithine, are inhibitors of glutathione and polyamine synthesis, respectively, with limited intrinsic antitumor activity; however, because of their powerful biochemical actions and their low systemic toxicities, they are being evaluated as chemotherapeutic adjuncts to or modulators of other more toxic antineoplastic agents.

Changes in polyamine-oxidizing capacity of peroxisomes under various physiological conditions in rats

Rat liver peroxisomal polyamine oxidase activity was determined under various physiological conditions by using the peroxidase method with phenol and 4-aminoantipyrine. N1-Acetylpolyamines such as N1-acetylspermine and N1-acetylspermidine were better substrates than the free polyamines. The polyamine oxidase activity in rat peroxisomes increased significantly when cell proliferation was high. The activity began to appear in fetal liver at the 16th approximately 18th day of pregnancy and peaked in neonatal liver on the first day (approx. 1.7-times higher than in adult liver). In regenerating rat liver, only polyamine oxidase activity among the peroxisomal enzymes tested was increased considerably 12 h after partial hepatectomy (approx. 2.8-fold over the control liver). Finally, the enzyme activity was significantly increased by administration of clofibrate, a peroxisome proliferator, which also causes hepatomegaly. In all cases, the increase in polyamine oxidase activity was not more than 3-fold. Since the level of polyamine oxidase activity in the normal liver is more than adequate in relation to the level of the substrates, the slight but significant increase under conditions of cell proliferation may have a role in modulating levels of polyamines in the proliferating liver tissue.

Studies of mammalian ornithine decarboxylase using a monoclonal antibody

A monoclonal antibody of the immunoglobulin M class was produced against mouse kidney ornithine decarboxylase. Screening for the antibody was carried out using alpha-difluoromethyl[5-3H]ornithine-labelled ornithine decarboxylase. The antibody reacted with this antigen and with native ornithine decarboxylase. The antibody attached to Sepharose could be used to form an immunoaffinity column that retained mammalian ornithine decarboxylase. The active enzyme could then be eluted in a highly purified form by 1.0M-sodium thiocyanate. The monoclonal antibody could also be used to precipitate labelled ornithine decarboxylase from homogenates of kidneys from androgen-treated mice given [35S]methionine. Only one band, corresponding to Mr of about 55000, was observed. The extensive labelling of this band is consistent with the rapid turnover of ornithine decarboxylase protein, since this enzyme represents only about 1 part in 10000 of the cytosolic protein.

Nonsteroid antiinflammatory drugs and tamoxifen for desmoid tumors and carcinoma of the stomach

The results of treatment of desmoid tumor patients with nonsteroid antiinflammatory drugs alone or in combination with tamoxifen are described. Tumor growth was inhibited in six of seven patients. Nonsteroid antiinflammatory drugs administered along with 5-fluorouracil and cyclophosphamide and other inhibitors of T-suppressor cells were used to treat nine patients with metastatic carcinoma of the stomach. Survival of these patients was extended so that after 12 months minimal follow-up the majority are well. A prospective controlled clinical trial is indicated.

Increase in histidine decarboxylase activity in skin of genetically mast-cell-deficient W/Wv mice after application of phorbol 12-myristate 13-acetate: evidence for the presence of histamine-producing cells without basophilic granules

Histidine decarboxylase (HisDCase, EC 4.1.1.22) activity in mouse skin increased by a factor of more than 10 after a single application of phorbol 12-myristate 13-acetate. The cell type that was responsible for the increase in HisDCase activity was examined by using (WB X C57BL/6)F1-W/Wv mice, which are genetically deficient in tissue mast cells. In contrast to a report that increase of ornithine decarboxylase (EC 4.1.1.17) activity occurs in the epidermis [O'Brien, T. G., Simisiman, R. C. & Boutwell, R. K. (1975) Cancer Res. 35, 2426-2433], the HisDCase activity was found to increase in the dermis. Although most of the histamine in the dermis was present in mast cells, the increase in HisDCase activity in the skin in W/Wv mice was comparable with that in congeneic +/+ mice. This increase of HisDCase activity in the skin of W/Wv mice was abolished by prior x-ray irradiation (800 rads; 1 rad = 0.01 gray) but was restored by subsequent bone marrow transplantation. Because mice, in general, are known to lack basophilic leukocytes, the present results suggest the existence of histamine-producing cells without basophilic granules that are derived from the bone marrow.