Combining polyamine depletion with radiation therapy for rapidly dividing head and neck tumors: strategies for improved locoregional control

PURPOSE

Locoregional control is adversely affected as clonogens from rapidly proliferating tumors repopulate during a course of radiation therapy. The cytostatic agent alpha-difluoromethylornithine (DFMO) was investigated for its capacity to slow proliferation kinetics in human squamous cell carcinomas (SCC) of the head and neck (H&N), with the ultimate objective of improving locoregional control in rapidly dividing tumors treated with radiation therapy.

METHODS AND MATERIALS

Three human SCC cell lines established from primary H&N tumors were evaluated in vitro (cell culture) and in vivo (SCC tumor xenografts in athymic mice) for the capacity of DFMO to induce growth inhibition. Flow cytometry analysis of SCC tumor growth kinetics and quantitative assessment of polyamine biosynthesis inhibition was performed to verify DFMO activity. DFMO effects on in vitro SCC radiosensitivity using clonogenic survival were also studied.

RESULTS

A noncytotoxic exposure to DFMO (5mM x 72 hours) induced pronounced growth inhibition in all three SCC cell lines (70-90% at 7 days), and induced a 2-3 fold delay in volume doubling time for SCC tumor xenografts when administered orally in the drinking water (1.5%) to athymic mice. Kinetic analysis via flow cytometry confirmed that DFMO produced a lengthening of SCC cell cycle times, but did not alter in vitro radiosensitivity. Inhibition of ornithine decarboxylase (ODC) activity and depletion of endogenous polyamines (putrescine and spermidine), were confirmed in normal tissue (mouse skin) and in human SCC tumor xenografts of athymic mice receiving continuous oral DFMO.

CONCLUSION

These data indicate that antiproliferative agents, such as DFMO, are capable of altering human SCC growth kinetics without altering intrinsic radiosensitivity. Such kinetic modulation may therefore provide a strategy to reduce the adverse impact of tumor cell proliferation during a radiotherapy treatment course for rapidly dividing tumors such as those in the H&N.

Regulatory region of plasma membrane Ca2+ pump. 28 residues suffice to bind calmodulin but more are needed for full auto-inhibition of the activity

The Ca(2+)-pumping activity of constructs containing various portions of the putative 28-residue calmodulin-binding domain (C domain) of hPMCA4b were compared. As the length of the C domain in the pump increased, the pump's activity decreased and the ability of calmodulin to stimulate the activity increased. Study of the calmodulin dependence of activity showed that the construct containing all 28 residues of the C domain had a K1/2 for calmodulin equal to that of the complete molecule; the constructs containing less of the C domain interacted less strongly with calmodulin. On the other hand, incorporation of all 28 residues of the C domain did not decrease the activity of the pump (in the absence of calmodulin) as low as the activity of the complete molecule. This indicates that other segments of the molecule, further toward the COOH terminus, are also required for the degree of inhibition seen in the complete molecule.

The Ca2+ affinity of the plasma membrane Ca2+ pump is controlled by alternative splicing

The plasma membrane Ca2+ pump is a calmodulin-regulated P-type ATPase that is an essential element in controlling intracellular Ca2+ concentration. Studies on the gene structure of this pump have revealed an alternate splice option that changes the structure of the calmodulin-binding domain. This change in the structure of the enzyme results in a reduced calmodulin affinity. Tests of the enzyme's activity in the presence of a high calmodulin concentration, approximating that found inside living cells, show that this reduced calmodulin affinity causes a reduced apparent affinity of the enzyme for Ca2+. This shift in the Ca2+ activation occurs in a Ca2+ concentration range crucial to cellular function and is probably the physiologically important consequence of the alternate splice.

Transrectal fine needle aspiration of prostate

56 patients with prostatic enlargement were subjected to transrectal fine needle aspiration (FNA) of prostate. The cytologic diagnosis was correlated with histology in 55 cases. Benign prostatic hyperplasia (BPH) was diagnosed in 44 cases. In 18 of these, there was associated chronic prostatitis in three cases acute prostatitis and in two cases granulomatous prostatitis. One case of tuberculous prostatitis and 11 cases of prostatic carcinoma could also be diagnosed on cytologic basis. There was only one false negative and no false positive cytodiagnosis was made.

A highly active 120-kDa truncated mutant of the plasma membrane Ca2+ pump

A truncated mutant (hPMCA4b(ct120)) of the plasma membrane Ca2+ pump was expressed in COS-1 cells. The full-length pump (hPMCA4b) consisted of 1205 residues, and the mutant lacked 120 residues (including the 28-residue calmodulin-binding inhibitory domain) at the COOH terminus. To characterize this construct, Ca2+ transport was determined in a microsomal fraction. Phosphate was added to increase Ca2+ uptake, and specificity was enhanced by adding thapsigargin to inhibit the endoplasmic reticulum Ca2+ pump. The mutant showed a similar level of expression as hPMCA4b and a Ca2+ affinity and Ca2+ transport activity about equal to that of hPMCA4b when hPMCA4b was activated. Addition of the synthetic peptide C28R2, corresponding to the calmodulin binding region of the pump, inhibited the mutant and restored the non-activated state of the enzyme. In these respects, the truncated mutant acted like hPMCA4b, when hPMCA4b had been proteolyzed to cleave a bond between the calmodulin binding region and the NH2-terminal portion of the molecule. This indicates that the effects of proteolysis are due to removal of the COOH terminus and not to rearrangement of the two fragments. Since the truncated mutant was fully active and its tryptic digestion resulted in the appearance of the expected 81- and 76-kDa active fragments, we concluded that the COOH-terminal portion which is missing cannot be important in synthesis or proper folding of the enzyme.

Randomized phase I chemoprevention dose-seeking study of alpha-difluoromethylornithine

BACKGROUND

alpha-Difluoromethylornithine (DFMO) is an irreversible inhibitor of ornithine decarboxylase (ODC), the key enzyme in mammalian polyamine biosynthesis. Levels of ODC are closely related to tumor promotion, and inhibition of ODC is associated with suppression of tumor development in laboratory animals. DFMO has shown a dose-response effect in tumor inhibition in mice.

PURPOSE

A randomized phase I study of DFMO was conducted to determine the lowest daily oral dose that can achieve at least 50% inhibition of ODC activity induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in human skin, with minimal clinical toxicity (grade 1 or lower; Eastern Cooperative Oncology Group [ECOG]).

METHODS

Cancer patients entered in steps 1 and 2 of the study had been treated and had no clinical evidence of cancer. In step 1, 13 patients received 0.125, 0.25, 0.5, or 0.75 g/m2 DFMO four times a day. In step 2, 13 patients received 0.125 or 0.25 g/m2 four times a day or 0.5 or 1.0 g/m2 every day. The 26 patients treated in steps 1 and 2 (range, < 1-6 months) had colon, prostate, or bladder cancer. In step 3, six cancer-free subjects at risk for colorectal cancer received 0.5 g/m2 every day for 5-12 months. To evaluate the effectiveness of DFMO in reducing TPA-induced ODC activity, we calculated the percent change from pretreatment ODC levels in skin biopsy specimens and the percentage of subjects with at least a 50% reduction in ODC levels.

RESULTS

In step 1 of the study, treatment-limiting audiotoxicity was observed at the three highest doses. Because the only dose with no major toxic effects in step 2 was 0.5 g/m2 every day, that dose was administered in step 3, with no major toxic effects. Seven subjects treated with 0.5 g/m2 every day had pretreatment ODC levels in the normal range; five averaged a reduction in ODC activity of at least 50%. DFMO had linear pharmacokinetics over the entire dose range. When 0.5 g/m2 was given every day, the peak plasma concentration was 47.1 +/- 5.1 microM at 3-4 hours (monthly mean +/- SE, 14.5 +/- 5.2 microM); half-life was 3.5 hours; and area under the curve for plasma concentration x time for a single dose of DFMO was 311 +/- 39 microM x hour.

CONCLUSIONS

These data support phase II chemoprevention studies with DFMO given at a dose of 0.5 g/m2 every day.

IMPLICATIONS

Studies investigating prevention of cancers with DFMO are under consideration.

Aspiration cytology of maxillary myxoma

Fine-needle aspiration was used to diagnose a case of maxillary myxoma. Abundant mucoid material was obtained. Microscopic examination showed three-dimensional fibrillary myxoid fragments entangling spindle-shaped, stellate, and fusiform cells with round to oval monomorphic nuclei. A striking feature was delicately branching capillaries. The diagnosis was subsequently confirmed on histology and histochemistry.

Testicular cytology in azoospermia

Two hundred-seventy-five azoospermic males were subjected to fine-needle aspiration (FNA) cytologic study of testis with the aim of determining the cause of azoospermia; 534 aspirates from these patients were classified as follows: normal spermatogenesis (162), hypospermatogenesis (mild, moderate, or severe, 226), absence of spermatogenesis (130), maturation arrest (36), Sertoli-cell-only syndrome (14), and Leydig-cell hyperplasia (3). The morphology of cells was excellent in the cytologic preparations and various spermatogenic cells and Sertoli cells were easily recognized. Leydig cells were uncommonly seen, except in cases of Leydig-cell hyperplasia. Degenerative changes, possibly due to obstruction, were seen in 104 cases. The procedure was well tolerated by the patients. We conclude that FNA cytology is a useful investigative modality in the evaluation of azoospermic males.

Expression of retinoic acid nuclear receptors and tissue transglutaminase is altered in various tissues of rats fed a vitamin A-deficient diet

The effects of vitamin A nutritional status on the levels of expression of retinoic acid nuclear receptors (RAR), and the retinoic acid-responsive gene, tissue transglutaminase, were determined in rats. Weanling male Sprague-Dawley rats fed a vitamin A-deficient diet for approximately 7 wk developed vitamin A deficiency, as confirmed by the depletion of liver retinol and retinyl palmitate. Controls were fed the same diet supplemented with 24 mg/kg retinyl acetate. The levels of expression of RAR beta mRNA were approximately 80% lower in bladder, brain, liver, lung and trachea and those of RAR gamma mRNA were approximately 50% lower in bladder, lung and trachea of rats fed the vitamin A-deficient diet than in controls. The levels of expression of RAR alpha mRNA were approximately 90% lower in brain and approximately 30% greater in liver, kidney, intestine and lung of rats fed the vitamin A-deficient diet. Vitamin A deficiency also resulted in reduced expression of tissue transglutaminase in the bladder, lungs and trachea, which paralleled the effects observed for RAR beta and RAR gamma. When vitamin A-deficient rats were subsequently fed a retinol-deficient diet supplemented with retinoic acid for 4 wk, the expression of RAR (beta and gamma) and tissue transglutaminase returned to the control levels. These results indicate that vitamin A nutritional status in rats influences the expression of both RAR and tissue transglutaminase in certain tissues.

Transitional cell carcinoma of the renal pelvis metastatic to the metacarpal. A case report correlating cytologic and histologic findings

This report describes the cytologic, radiologic and histologic findings in a 76-year-old male who presented with a pathologic fracture of the first metacarpal bone as the result of metastatic transitional cell carcinoma. The primary neoplasm was sited in the right renal pelvis. Metastases were also detected in the liver and confirmed cytologically. Problems encountered with the cytologic diagnosis are explained by correlation with the histologic findings. The case also illustrates the importance of clinicopathologic correlation when interpreting fine needle aspiration biopsies.

Overexpression of the erythrocyte plasma membrane Ca2+ pump in COS-1 cells

A full-length cDNA corresponding to the hPMCA4 plasma membrane Ca2+ pump was assembled and expressed in COS-1 cells. The original sequence of hPMCA4 gave a very low expression. The mutation of the initiation translation site of this sequence to the consensus A/G-X-X-AUG-G increased the production of the protein. The Ca2+ pump activity in transfected cells was 1.5-3.5-fold higher than in controls. The Ca(2+)-dependence and the calmodulin stimulation of hPMCA4 expressed in COS-1 cells were comparable with those of the erythrocyte Ca2+ pump. Immunohistochemistry experiments showed that most of the expressed protein remained in intracellular membranes. Possible explanations for this targeting of the pump are discussed.

Levels of colorectal ornithine decarboxylase activity in patients with colon cancer, a family history of nonpolyposis hereditary colorectal cancer, and adenomas

Ornithine decarboxylase (ODC), a key enzyme in mammalian polyamine biosynthesis, has been proposed to be a marker of colonic epithelial cell proliferation and risk for colorectal cancer. We investigated the basal levels of ODC activity in sigmoid and rectal mucosae, and basal and tumor promoter 12-O-tetradecanoylphorbol-13-acetate-induced levels of skin ODC activity in individuals with a personal history of colon cancer (n = 9 colon; n = 58 skin), a family history of nonpolyposis hereditary colorectal cancer (n = 49; n = 42), adenomas (n = 16; n = 40), and healthy, family history-negative control subjects (n = 40; n = 79). Using a fresh tissue assay and samples obtained after a standard colon lavage preparation, colon mucosal ODC levels ranged from 0 to 192 pmol/mg/h (sigmoid, 0-163 pmol/mg/h; mean, 36 +/- 32 pmol/mg/h; rectum, 0-192 pmol/mg/h; mean, 35 +/- 32 pmol/mg/h). No differences among the four groups of subjects were found for either colon or skin ODC levels, and there were no sex differences overall or in any group. These results are not compatible with the suggestion that ODC levels are a useful marker of risk for colorectal cancer.

The housefly (Musca domestica) as a carrier of pathogenic microorganisms in a hospital environment

Houseflies have long been regarded as potential carriers of microorganisms. Since pathogenic microorganisms are widespread in the hospital environment, there is abundant opportunity for flies to become contaminated and, in turn, to contaminate the patient environment. In the present study, an attempt was made to isolate and identify pathogenic bacteria, fungi and parasites from the housefly Musca domestica collected in the surgical ward of the All India Institute of Medical Sciences Hospital and also in a remote residential area located 5 km from the hospital. A total of 113 flies were collected: 65 from a surgical ward (test) and 48 from a residential area for comparison. Ten genera of bacteria were isolated from the test group of flies compared with nine from the control group. In primary isolations, it was observed that the load of bacteria carried by the test group of flies was significantly more (P less than 0.001) than for the control flies. Pseudomonas aeruginosa, Enterococcus faecalis and viridans streptococci were isolated only from the test flies. The isolation rate of Staphylococcus aureus was significantly higher (P less than 0.001) in test houseflies than in the control houseflies. There was no significant difference in isolation of parasitic ova and cysts from test and control houseflies. Candida spp. were isolated in almost equal numbers from both groups of houseflies, yet none of these was Candida albicans. Houseflies therefore may act as vectors of potentially pathogenic bacteria in a hospital environment.

Some effects of vitamin A deficiency on the isolated rat lung alveolar type II cell

Alveolar Type II cells were isolated from control and vitamin A deficient rats and allowed to form a monolayer in plastic dishes for 16-18 hours. The vitamin A content (retinol plus retinyl palmitate) of deficient cells was 50-75% less than in control cells on a per mg protein basis. Isolated Type II cells took up [3H]-retinol, synthesized [3H]-retinyl palmitate, and after 4 hours, 24% of the radioactivity in the Type II cells was [3H]-retinoic acid. Deficiency did not appear to alter retinoic acid synthesis. Phosphatidylcholine (PC) and disaturated phosphatidylcholine (DSPC) synthesis, were slightly less in deficient cells compared to control (95 and 85% respectively). In addition, 10(-6) M and 10(-5) M retinoic acid in the reaction media stimulated both PC and DSPC synthesis by 120-140% in control cells. The stimulating effect of retinoic acid was present in deficient cells as well, but less pronounced (120% with 10(-5) M). Vitamin A deficient Type II cells also had less basal levels of both tissue transglutaminase and epidermal transglutaminase activity than control cells.

Absence of cognitive impairment after more than 100 lifetime ECT treatments

The cognitive function scores and subjective memory complaints of eight patients who had each received more than 100 treatments with bilateral modified since wave ECT were equivalent to those of matched patients who had never received ECT. The results suggest that patients given many ECT treatments over several courses do not manifest measurable cognitive impairment at long-term follow-up.

Human cutaneous myiasis due to mixed infestation in a drug addict

Soft tissue infestation by maggots of flies (myiasis) is a well-recognized complication of neglected wounds. Mixed infestation by larvae of more than one species of fly is a rarity. We report, for the first time in India, one such case of cutaneous myiasis due to mixed infestation--in this instance by Chrysomya bezziana and Sarcophaga sp. in a drug addict.

Involvement of retinoic acid nuclear receptors in retinoic acid-induced tissue transglutaminase gene expression in rat tracheal 2C5 cells

The involvement of retinoic acid nuclear receptors (RARs) in the induction of tissue transglutaminase (TG) by retinoic acid in rat tracheal 2C5 cells was determined. The levels of RAR alpha and RAR beta were altered in 2C5 cells by transfection with RAR expression vectors. Increased expression of RAR alpha increased the induction of tissue TG by retinoic acid. In contrast, decreased RAR alpha expression, using an antisense RAR alpha expression vector, diminished the normal level of tissue TG induction caused by retinoic acid. Transfectants overexpressing RAR beta were also more responsive to retinoic acid for the induction of tissue TG, although the magnitude of TG induction was not as great as resulted from RAR alpha overexpression. These results indicate that the levels of the RAR alpha and RAR beta dictate the magnitude of tissue TG induction by retinoic acid.

Novel heteroarotinoids: synthesis and biological activity

In this study, 13 heteroarotinoids were synthesized. The key step in each preparation was the condensation of the appropriate chroman-, thiochroman-, or benzothienyl-substituted phosphorus ylide, obtained from the independent synthesis of the corresponding phosphonium salts, with selected polyene-substituted aldehyde esters. Nine of these heterocycles contained a thiochroman group, two had a chroman group, and two others had a benzothienyl system. Screening of the compounds was with one of two assays. One assay measured the ability of a retinoid to inhibit the phorbol ester induced increase of mouse epidermal ornithine decarboxylase (ODC) activity. The other assay measured retinoid-induced differentiation of the human myoloid leukemia cell line HL-60. In the ODC assay, all thirteen compounds were screened. The most active heteroarotinoids were ester 10 [methyl (E)-4-[2-(2,2,4,4-tetramethylthiochroman-6-yl)-1- propenyl]benzoate] and acid 11 [(E)-4-[2-(2,2,4,4-tetramethyl-3,4- dihydro-2H-1- benzothiopyran-6-yl)-1-propenyl]benzoic acid]. Both of these retinoids had ID50 values (dose required for half-maximal inhibition of phorbol ester induced ODC activity) of about 0.3 nmol. In comparison, the ID50 value for trans-retinoic acid (1) was 0.12 nmol while the ID50 values for acids 7 and 9, namely (2Z,4E,6E)-3,7-dimethyl-7-(4,4-dimethyl-thiochroman -6-yl)-2,4,6-heptatrienoic acid and (2E,4E,6E)-3,7-dimethyl-7-(2,2,4,4-tetramethylthiochroman -6-yl)-2,4,6- heptatrienoic acid, respectively, were about 3.5 nmol. Heteroarotinoids 8 and 12-17 had ID50 values of 35 nmol or greater. With a thiochroman unit, the most active acids in decreasing order of activity in the ODC assay were 7 greater than 9 greater than 8. Thus, simple replacement of the terminal propenyl system [C(16,17,18)] in 7 with a cyclopropyl group produced acid 8 [(2E,4E,6E)-7-methyl-7-(4,4-dimethylthiochroman-6-yl)- 2,3-methylene-4,6-heptadienoic acid with markedly reduced activity. With a benzoic acid group as part of the structure attached to the thiochroman unit, the ODC activity was enhanced as shown in 10 and 11. The combination of the 2,2,4,4-tetramethylthiochroman group and the benzoic acid (or ester) terminal group seemed to enhance the biological action which resembles that found with (E)-4-[2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)- 1-propenyl]benzoic acid (TTNPB, 6b), a well-known model system.(ABSTRACT TRUNCATED AT 400 WORDS)

90Y.B72.3 against pancreatic cancer: dosimetric and biological analysis

Nude mice xenografted with a human pancreatic carcinoma cell line were injected with yttrium-90 (90Y) conjugated to diethylene triaminepenta acetic acid (DTPA) alone, and DTPA covalently linked to a monoclonal antibody, B72.3. The animals were sacrificed in temporal sequence to evaluate isotope distribution. Dosimetry was carried out using the principles outlined in MIRD and ICRU Report 32. Results are expressed as percent uptake per unit mass in organs and tumor and as relative absorbed dose normalized to 90Y uptake in liver at 7 hr. When conjugated to B72.3, an 8-fold increase in isotope localization in the tumor was noted by 24 hr. When the relative absorbed dose is calculated for 90Y and 90Y.B72.3, a 26-fold increase in tumor dose is noted for the 90Y conjugate. Normal tissues show no to modest (less than 5x) enhanced dose with 90Y.B72.3. B72.3, therefore, deserves further investigation as a potential monoclonal antibody for targeting therapeutic radioisotopes and possibly diagnostic radioisotopes to pancreatic cancer. Radiobiological aspects of the low dose rates from radioimmunotherapy are discussed.

Cellular and segmental distribution of Ca2(+)-pump epitopes in rat intestine

We used a monoclonal antibody (5F10) specific for the human erythrocyte plasma membrane Ca(++)-pump to demonstrate the presence and distribution of Ca(++)-pump epitopes in rat intestine. In paraffin embedded tissue sections, antibody 5F10 binds to epitopes in the basolateral membranes of absorptive cells in rat duodenum and portions of jejunum but not ileum. Western blot analysis of intestinal mucosal proteins with antibody 5F10 shows binding of antibody to major bands of Mr approximately 135,000 and Mr approximately 72,000, and to lesser bands of Mr approximately 125,000 and Mr approximately 27,000. This pattern was seen in mucosal homogenates of rat duodenal and jejunal cells and to a lesser extent in ileal cells. The Mr approximately 135,000 band corresponds to the molecular weight of Ca(++)-pumps in other tissues. The other bands correspond in size to known proteolytic fragments of the Ca(++)-pump. Slot-blot analysis of nitrocellulose immobilized mucosal homogenates shows binding of 5F10 to be greatest in duodenum and least in ileum. Ca(++)-transport studies by the everted gut sac technique show a correlation between vitamin D induction of active Ca(++)-transport and the segmental distribution of Ca(++)-pump epitopes.

Expression of human chromosome 2 ornithine decarboxylase gene in ornithine decarboxylase-deficient Chinese hamster ovary cells

Ornithine decarboxylase (ODC) belongs to a multigene family and some of these may very well be nonfunctional (pseudogenes). We isolated an ODC gene from a human chromosome 2-specific library and transfected the gene into ODC-deficient Chinese hamster ovary cells to directly demonstrate that this ODC gene is functional and ODC is essential for cell proliferation. After screening 2.5 X 10(5) plaques using a human ODC complementary DNA probe, a typical clone with a 5.4-kilobase insert was isolated and then cloned into the HindIII site of the pGem-1 vector. One (phODC 2B1) of these clones containing a 5.4-kilobase ODC gene insert was identified. Restriction enzyme analysis and partial sequencing data revealed that phODC 2B1 contained the full length protein-coding sequences but lacked first exon and 3'-polyadenylation sequences. Primer extension analysis indicated that human ODC mRNA has homologous sequences with the ODC gene from human chromosome 2. To determine that the chromosome 2 ODC gene is functional, ODC-deficient Chinese hamster ovary cells were transfected with the ODC expression vector (phSV2B1-neo) and several G418-resistant transfectants were isolated which expressed 70- to 400-fold more ODC activity than parental or wild-type Chinese hamster ovary cells. Furthermore, these stable transfectants exhibited a higher growth rate than wild-type cells. These results indicate that the ODC gene from human chromosome 2 encodes functional ODC protein, and ODC (and its product putrescine) is required for cell growth.

The calcium-transporting ATPase and the calcium- or magnesium-dependent nucleotide phosphatase activities of human placental trophoblast basal plasma membrane are separate enzyme activities

The properties of calcium-stimulated ATP hydrolysis often differ from those of ATP-dependent calcium transport. We have characterized two components of calcium-stimulated ATP hydrolysis in human placental basal plasma membrane. In the absence of magnesium, component 1 apparently has saturable sites for free calcium in both the nanomolar and low micromolar range. It was stimulated by either calcium or magnesium, was unselective for nucleotide substrate, and its activity was very much greater than that of ATP-dependent calcium transport. Component 1 was inhibited by GTP, permitting measurement of component 2 with activity and magnesium stimulation comparable to ATP-dependent calcium transport. Component 2 was inhibited partially by an antibody against purified erythrocyte calcium transporter and completely by sulfhydryl reagents, whereas component 1 was unaffected. A phosphorylated intermediate of the calcium transporter co-migrated with the erythrocyte transporter on acidic sodium dodecyl sulfate-polyacrylamide electrophoresis gels. Immunostaining after transfer to nitrocellulose revealed a doublet. The band of lower molecular weight co-migrated with that of the human erythrocyte membrane transporter. The addition of GTP permits separate measurement of ATP hydrolysis by the calcium transporter of the placental basal plasma membrane and may be useful in defining its properties in other cell membranes under a variety of conditions.

Absence of effect of supplemental oral calcium on ornithine decarboxylase (ODC) activity in colonic mucosae of healthy individuals with a family history of colorectal cancer

Tissue activity levels of ornithine decarboxylase (ODC) have been suggested to be a marker of colonic epithelial cell proliferation and risk for colorectal cancer. Supplemental dietary calcium has been hypothesized and reported to suppress colonic epithelial-cell proliferation. We measured sigmoid and rectal mucosal ODC activity levels in 45 healthy, disease-free subjects with strong family histories of colorectal cancer before and after 2 months, during which daily dietary supplementation with calcium carbonate (to provide 600 mg calcium base) was taken. Although the mean ODC activity levels decreased in both sigmoid and rectal specimens, these changes were small in relation to the standard deviation and were not statistically significant. These data suggest that the magnitude of dietary calcium intake does not significantly influence sigmoid-rectal mucosal ODC activity levels and that ODC measurements may not be a useful intermediate endpoint for interventions designed to interrupt the colon carcinogenic sequence.

Sinusoidal endothelial hyperplasia in pathogenesis of perilobular fibrosis in rabbit after experimental ligation of common bile duct

Development of perilobular hepatic fibrosis in rabbits after experimental ligation of the common bile duct was studied by microscopy. Twelve hours after the ligation, the lobular boundaries assumed prominence by appearance of row(s) of congested sinusoids around the distended perilobular canals of Hering. Seven days later, the lobular laminae limitans around such canals of Hering revealed myxomatous ballooning degeneration forming well defined inter-lobular bands (ILBs). On day 15 post-ligation, the residual sinusoidal endothelial-lining cells in the ILBs manifested hyper chromasia and occasional mitotic activity. It was followed, on days 25 and 35, by proliferation (hyperplasia) of the sinusoidal endothelium cells forming the portal tract like fibrotic tissue in the perilobular bands. These findings, showed the course of interlobular bridging necrosis along the bile preductules at the lobular circumferences and subsequently indigenous origin of the fibrotic tissue in the ILBs from the residual cells in the affected parenchyma independent of the portal tracts.

Plasma membrane calcium pump and 28-kDa calcium binding protein in cells of rat kidney distal tubules

In an effort to extend our studies on Ca2+ pumps to animal models, we developed a new monoclonal antibody (5F10) prepared against the human erythrocyte Ca2+-Mg2+-adenosinetriphosphatase (ATPase) that recognizes a protein of approximately 140 kDa in rat kidney homogenates. Enzyme-linked immunosorbent assays show that monoclonal antibody 5F10 binds purified Ca2+-Mg2+-ATPase and rat kidney membrane extracts in a concentration-dependent manner. In paraffin-embedded tissue sections, antibody 5F10 binds to an epitope in the basolateral membranes of rat kidney distal convoluted tubule principal cells. The antibody does not bind to intercalated cells. The latter cells were characterized by the presence of large amounts of carbonic anhydrase C. Polyclonal antibodies directed against chick intestinal 28-kDa vitamin D-dependent calcium binding protein (28-kDa CaBP) also bind epitopes in distal convoluted tubule cells, connecting tubules, and portions of collecting duct but not intercalated cells. Western blot and 45Ca blot analysis of renal cytosolic proteins showed that the polyclonal 28-kDa CaBP-directed antibody detects a protein which also binds calcium. Western blot analysis with monoclonal antibody 5F10 shows binding to both the authentic purified erythrocyte Ca2+ pump (approximately 138 kDa) and to tryptic fragments of this pump. Antibody JA3, previously used for staining of human kidney tubules, reacts with a different set of tryptic fragments, showing that the two antibodies are directed against different regions or conformational determinants on the pump molecule. We show that Ca2+-Mg2+-ATPase and 28-kDa CaBP are present in the principal cells of the distal convoluted tubule of the rat and are absent in intercalated cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Colon ornithine decarboxylase activity following standard endoscopy preparation regimens

Ornithine decarboxylase (ODC) catalyzes the formation of putrescine from ornithine, which is the first step in the pathway of mammalian polyamine biosynthesis. Tissue activity levels of ODC have been suggested to be a marker of risk for colorectal cancer in hereditary polyposis and in adenoma formers. We analyzed ODC activity in rectal and sigmoid colon mucosal biopsies obtained at 10 cm and at 30 cm in 40 healthy, colon cancer risk factor-free adults following three endoscopic preparation regimens: 1) no special preparation; 2) two phosphate enemas; and 3) "Colyte" lavage preparation 12 hr previously. Levels of ODC, measured in fresh tissue, were approximately twofold higher for enema preparation vs. no preparation (for log-transformed data: sigmoid, P less than 0.0001; rectum, P = 0.0001) and for enema preparation vs. lavage (sigmoid, P = 0.0002; rectum, P = 0.008). Lavage and no preparation ODC levels were not significantly different. ODC activity levels ranged from 0.00 to 352.96 pmol/mg/hr.

The enzyme-activated irreversible inhibitor of ornithine decarboxylase, DL-alpha-difluoromethylornithine: a chemopreventive agent

DL-alpha-Difluoromethylornithine (DFMO) is an enzyme-activated irreversible inhibitor of mammalian ornithine decarboxylase. DFMO, when administered in drinking water, precludes increases in the levels of intracellular putrescine and spermidine and also inhibits the induction of skin, breast, colon, urinary bladder, and intestinal cancers in experimental animal models. DFMO may be a useful drug for cancer prevention in humans; however, long-term medication with higher doses (9 g/m2/day) of DFMO has resulted in several toxic side effects such as thrombocytopenia and reversible ototoxicity. Smaller doses (less than 1 g/m2/day), selected by our in vitro human skin punch biopsy assay, may be given for a longer period without appreciable toxicity. Further evaluation in human cancer prevention trials is indicated.

Lack of a role of DNA methylation in tumor promoter 12-O-tetradecanoylphorbol-13-acetate-induced synthesis of ornithine decarboxylase messenger RNA in T24 cells

Association of alteration in DNA methylation pattern in triggering 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced transcription of ornithine decarboxylase (ODC) gene in T24 cells was determined. In accord with our previous findings (Archiv. Biochem. Biophys., 262: 326-336, 1988), TPA treatment of T24 cells, cultured in serum-free medium, resulted in a dramatic (approximately 15-fold) increase in ODC activity which was accompanied by a proportional increase in hybridizable amount of ODC mRNA. Data from nuclear run-off transcription assay revealed that TPA-induced accumulation of ODC mRNA is the result of increased transcription initiation. Since DNA hypomethylation has been proposed to be a mechanism involved in the regulation of transcription of some gene(s), we examined the changes in the methylation patterns in the ODC gene isolated from the vehicle (ethanol)- and TPA-treated T24 cells. The autoradiograms resulting from the Southern blot analysis of DNA cleaved with several methylation-sensitive restriction endonucleases [e.g., HpaII, MspI, cfoI (HhaI), SalI, XhoI] exhibited no difference in methylation pattern of ODC gene in T24 cells. Also, a single or chronic application of TPA to either noninitiated or 7,12-dimethylbenz(a)anthracene-initiated mouse skin failed to alter DNA methylation pattern of ODC gene. Furthermore, the hypomethylation agent 5-azacytidine failed to induce ODC mRNA in T24 cells. These results indicate that TPA does not affect the methylation status of ODC gene and hypomethylation may not be sufficient for TPA-increased ODC gene transcription in T24 cells.

Calcium pump epitopes in placental trophoblast basal plasma membranes

The syncytiotrophoblast represents the primary cellular barrier between maternal and fetal circulations in the placenta. Large amounts of Ca2+ are transported across this barrier by mechanisms that are not clearly understood. To further understand this phenomenon, we examined rat and human placenta by immunohistochemical and protein blotting techniques with a monoclonal antibody raised against the human erythrocyte plasma membrane Ca2+ pump. Immunohistochemistry with this antibody showed specific staining in the human placenta of the basal (fetal facing) surface of the syncytiotrophoblast. In the rat placenta, immunohistochemistry also showed specific staining of the innermost (fetal facing) layer of the trophoblast and the basal surface of the endoderm of the intraplacental yolk sac. In Western blots of placental homogenates and membranes, the monoclonal antibody bound to a 140,000-mol wt band, characteristic of Ca2+ pumps in other tissues. Western blots of isolated basal membranes showed more intense staining than isolated microvillous membranes, confirming the results of the immunohistochemistry. In addition, Ca2+ transport in basal membrane vesicles from human placenta was inhibited by polyclonal antibodies prepared against the erythrocyte Ca2+ pump. We conclude that basal (fetal facing) layers of human and rat placentas contain a high-affinity Ca2+ pump situated to transport Ca2+ from the maternal to the fetal circulation.

Ornithine decarboxylase activity as a biochemical marker in individuals predisposed to lung cancer

Ornithine decarboxylase (ODC) is the first enzyme in the pathway of mammalian polyamine biosynthesis. "Tumor promoters" appear to induce ODC. In addition, increased ODC activity has been observed in normal appearing colonic mucosa of patients with familial polyposis, an autosomal dominant disorder associated with a high incidence of colon cancer. Ornithine decarboxylase activity was measured in bronchoscopic mucosal biopsy specimens from the noninvolved lung in patients with unilateral lung masses. No correlation could be determined in ODC levels from "normal" mucosa between patients with lung cancer compared to those with benign disease, despite elevated ODC activity in the tumors themselves.

Inhibition of 7,12-dimethylbenz(a)anthracene- and N-nitrosomethylurea-induced rat mammary cancer by dietary flavonol quercetin

The effects of dietary supplementation of flavonol quercetin on both 7,12-dimethylbenz(a)anthracene (DMBA)- and N-nitrosomethylurea-induced mammary cancer in female Sprague-Dawley rats were determined. Quercetin diet was started 1 wk before intragastric instillation of DMBA (65 mg/kg of body weight) or i.v. injection of N-nitrosomethylurea (50 mg/kg of body weight) and was continued during the entire period (20 wk) of the experiment. Dietary quercetin inhibited both the incidence and the number of palpable rat mammary tumors; rats fed on 2% quercetin had 25% less incidence of mammary cancer, while the average number of mammary tumors per rat was reduced by 39% at 20 wk post-DMBA administration compared to animals on a control diet. In a separate experiment, a 5% quercetin diet elicited a greater inhibitory effect on the induction of rat mammary tumors by DMBA than was observed with a 2% quercetin diet. The inhibitory effect of quercetin on mammary tumor incidence in rats on 2% and 5% diets and on tumor multiplicity in animals on a 5% diet was statistically significant (P less than 0.05). In addition, the risk of the development of a palpable tumor (as determined by the nonparametric estimate of the hazard function) in the quercetin-fed group was lower than the group on control diet throughout the course of the experiment. Furthermore, 5% dietary quercetin significantly inhibited (P less than 0.05), although to a lesser extent than observed in DMBA-induced tumor formation, both the incidence and the number of palpable mammary tumors per rat induced by N-nitrosomethylurea. Dietary quercetin did not elicit any detectable sign of toxicity. The gain in body weight in rats on the quercetin diet and the quantity of diet consumed per rat per week were similar to those for rats on the control diet.

Complete primary structure of a human plasma membrane Ca2+ pump

cDNAs coding for a plasma membrane Ca2+ pump were isolated from a human teratoma library and sequenced. The translated sequence contained 1,220 amino acids with a calculated molecular weight of 134,683. All regions of functional importance known from other ion-transporting ATPases could be identified. The translated sequence also contained, near the carboxyl terminus, the calmodulin-binding domain and two domains which are very rich in glutamic acid and aspartic acid. These two domains resemble calmodulin somewhat and one of them may play a role in the binding of Ca2+. The enzyme also contains domains rich in serine and threonine, one of which has a sequence matching those of good cAMP-dependent protein kinase substrates. The carboxyl-terminal region is important for regulation by calmodulin, proteolysis, and phosphorylation. Near the amino terminus are two domains which are very rich in lysine and glutamic acid, as well as two domains resembling EF hands, one of which also has some resemblance to calmodulin. Comparison of the cloned sequence with peptide sequences from the erythrocyte Ca2+ pump showed that the two proteins have a very high proportion of identical residues but are not 100% identical, indicating that they represent different isozymes.

Co-localization of erythrocyte Ca++-Mg++ ATPase and vitamin D-dependent 28-kDa-calcium binding protein

We have previously shown that the human kidney distal convoluted tubule (DCT) contains epitopes of the human erythrocyte Ca++-Mg++ ATPase pump (J Clin Invest 80: 1225-1231, 1987). To determine whether vitamin D-dependent 28-kilodalton-calcium binding protein (28kDa-CaBP)and Ca++-Mg++ ATPase are present in the same cells of the human kidney, kidney tissue was examined for immunoreactivity with antibodies directed against these proteins. Double-label immunohistochemistry showed that a majority of the distal convoluted tubules contain epitopes to both of these proteins. portions of the distal nephron which were positive for 28kDa-CaBP did not show anti-Ca++-Mg++ ATPase antibody binding. All other portions of the nephron were negative for both proteins. Western blot analysis of kidney homogenates by 7% sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), showed binding of an anti-Ca++-Mg ATPase monoclonal antibody to a major band of Mr = 140,000. Western blots of kidney homogenates by 10% SDS-PAGE also showed binding of an anti-28kDa-CaBP polyclonal antibody to a protein band at Mr = 28,000. Incubation of parallel blots from the same 10% gel with 45CaCl2 demonstrated that the Mr = 28,000 band binds calcium. This work demonstrates, for the first time, that epitopes of vitamin D-inducible 28kDa-CaBp and human erythrocyte Ca++-Mg++ ATPase pump are present in the same cells of the human kidney. Previous work in our laboratory has shown that 28kDa-CaBP binds calcium in a manner analogous to calmodulin, a known regulator of the erythrocyte Ca++-Mg ATPase pump (J Biol Chem, 1987).(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of tumor promoter 12-O-tetradecanoylphorbol-13-acetate-induced synthesis of epidermal ornithine decarboxylase messenger RNA and diacylglycerol-promoted mouse skin tumor formation by retinoic acid

Evidence is presented that inhibition of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced ornithine decarboxylase (ODC; EC 4.1.1.17) by retinoic acid may involve inhibition of protein kinase C-mediated synthesis of ODC mRNA. A single application of 10 nmol of TPA to intact mouse skin led to an increase in the steady state levels of epidermal ODC mRNA; a maximal level of ODC mRNA occurred at about 3.5 h after TPA treatment. TPA-induced increase in ODC mRNA preceded the increase in epidermal ODC activity. Application of 17 nmol of retinoic acid 1 h before application of TPA to mouse skin inhibited the induction of both ODC mRNA and ODC activity. Using the DNA-excess filter hybridization technique, we found that TPA-increased steady state levels of ODC mRNA in primary culture of newborn mouse epidermal cells were the result of enhanced accumulation of newly synthesized ODC mRNA. Furthermore, in a pulse-chase experiment, we could not detect any difference in the half-life of ODC mRNA in epidermal cells after TPA or the vehicle dimethyl sulfoxide treatments; the half-life of ODC mRNA was about 7 h in both cases. Exposure of primary cultures of newborn epidermal cells to retinoic acid, in conjunction with TPA, inhibited the synthesis of ODC mRNA and failed to alter the half-life of ODC mRNA. These results implicate the role of transcription activation in TPA-induced ODC gene expression and indicate that retinoic acid may inhibit TPA-induced ODC gene transcription. We also found that protein kinase C may play a role in the mechanism of inhibition by retinoic acid of ODC gene expression. Supporting evidence is the finding that L-alpha-dioctanoylglycerol, an activator of protein kinase C, is a Stage II mouse skin tumor promoter and the application of retinoic acid 1 h before application of L-alpha-dioctanoylglycerol to mouse skin inhibited the induction of ODC activity and ODC mRNA as well as tumor promotion by L-alpha-dioctanoylglycerol. Taken together, one may conclude that the mechanism of inhibition of TPA-induced ODC by retinoic acid may involve the inhibition of protein kinase C-mediated accumulation of newly synthesized ODC mRNA.

Involvement of protein kinase C in the transcriptional regulation of ornithine decarboxylase gene expression by 12-O-tetradecanoylphorbol-13-acetate in T24 human bladder carcinoma cells

We have analyzed the molecular mechanisms involved in ornithine decarboxylase (ODC) induction by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) in T24 cells, an easily manipulable human epithelial cell line. The addition of as low as 10(-9)M TPA to T24 cells, cultured in a serum-free medium, resulted in ODC induction, with peak ODC activity occurring at about 6 h after TPA treatment. The induction of ODC activity correlates with the steady-state levels of ODC mRNA increased by TPA in T24 cells. TPA treatment did not elicit any change in the size (2.1 kb) of ODC mRNA as determined by Northern blot analysis by hybridization to nick-translated 32P-labeled cDNA prepared from either mouse or human ODC mRNA. Using the DNA-excess filter hybridization technique, we found that increased steady-state levels of ODC mRNA after TPA treatment may be the result of enhanced accumulation of newly synthesized ODC mRNA. The magnitude of the induction of ODC activity was proportional to the amount of ODC mRNA synthesis caused by TPA. In a pulse-chase experiment, we failed to detect any difference in the half-life of ODC mRNA in T24 cells after treatment with either TPA or the vehicle ethanol; the half-life of ODC mRNA was about 6 h in both cases. Furthermore, as determined by the "nuclear runoff transcription assay," the rate of transcription of ODC-gene was increased by treatment of T24 cells with TPA. These results provide direct evidence of the role of transcription-initiation in ODC-gene expression. The examination of the role of protein kinase C in ODC-gene transcription revealed that TPA or diacylglycerol did not induce the synthesis of ODC mRNA in PKC-deficient T24 cells. Taken together these results indicate that the TPA-increased synthesis of steady-state levels of ODC mRNA in T24 cells may be mediated by protein kinase C and is regulated at the transcriptional level.

The protein kinase C activator L-alpha-dioctanoylglycerol: a potent stage II mouse skin tumor promoter

Endogenous diacylglycerol, as produced during ligand-stimulated hydrolysis of phosphatidylinositol, is a physiological activator of protein kinase C, a receptor for the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Diacylglycerol mimics many effects of phorbol ester TPA, but it is not known whether diacylglycerol is a mouse skin tumor promoter. The present studies determined the mouse skin tumor-promoting activity of L-alpha-dioctanoylglycerol (DG), a membrane-permeable diacylglycerol derivative. In two independent experiments with female SENCAR mice, DG at a 2 mumol dose, when applied twice weekly to the initiated mouse skin, failed to promote mouse skin tumor formation. Similarly, DG lacked Stage I tumor-promoting activity; twice weekly applications of DG for 2 wk to the initiated mouse skin followed by twice weekly applications of mezerein (3.3 nmol) for as long as 27 wk elicited only a few papillomas per mouse. DG was found to be a potent Stage II mouse skin tumor promoter. In a typical two-stage tumor promotion experiment, SENCAR mice were initiated by application of 20 nmol of DMBA to their shaved backs. Two wk after initiation, 3.3 nmol of TPA were applied twice weekly for 2 wk (Stage I), and then 2 mumol of DG or 3.3 nmol of mezerein were applied to the skin twice weekly for the entire duration of the experiment (Stage II). Stage II tumor promotion with mezerein and DG resulted in 13.33 +/- 0.88 and 11.13 +/- 1.25 papillomas per mouse, respectively, at 19 wk and the carcinoma incidence, 43% and 33%, respectively, at 27 wk of promotion. The tumor-promoting activity of DG was compared with the parent alcohol glycerol, and it was found that glycerol, at a dose as high as 11 mumol, was not a complete, Stage I or Stage II mouse skin tumor promoter. Both TPA and DG, when applied to mouse skin, induced epidermal ornithine decarboxylase activity. Both TPA and DG activate protein kinase C, but the results presented indicate that TPA and DG differ in their tumor-promoting properties. DG, like mezerein, is a Stage II mouse skin tumor promoter.

Characterization of membrane calcium pumps by simultaneous immunoblotting and 32P radiography

Calcium pumps of various plasma membrane, endoplasmic reticulum and sarcoplasmic reticulum preparations were visualized by simultaneous immunoblotting and autoradiography of the 32P-labelled phosphoenzymes. The pump proteins and their fragments produced by a proteolytic pretreatment of the membranes were selectively phosphorylated by [gamma-32P]ATP, separated on an acidic SDS-polyacrylamide gel, blotted onto nitrocellulose and reacted with polyclonal antibodies raised against the purified human erythrocyte and rat skeletal muscle sarcoplasmic reticulum calcium pumps, respectively. The immuno-reaction was detected by peroxidase staining, while the phosphoproteins were shown by autoradiography of the same blot. An antibody against the erythrocyte calcium pump, reacting on the blot with the 140 kDa erythrocyte calcium pump and its 80 kDa proteolytic fragment, did not show a cross-reaction with the calcium pump of similar molecular mass in rat synaptosome membranes or with any of the endoplasmic- or sarcoplasmic-type calcium pumps. An anti-sarcoplasmic reticulum calcium pump antibody cross reacted with several sarcoplasmic and endoplasmic calcium pump proteins and their proteolytic fragments but with none of the plasma membrane pumps. This sensitive double-labelling method can be applied to study structural relationships and molecular alterations in various ion pump proteins.

Identification and primary structure of a calmodulin binding domain of the Ca2+ pump of human erythrocytes

Exposure of the purified Ca2+ pump of human erythrocytes to chymotrypsin led to the rapid loss of calmodulin activation. A fragment of about 12 kDa was removed from the ATPase in 1-2 min. Blotting experiments with 125I-labeled calmodulin showed that this fragment contains the calmodulin binding region. The remainder of the ATPase molecule was degraded to a number of fragments ranging from 3 to 120 kDa; none of them bound calmodulin. To isolate the calmodulin binding domain, calmodulin which had been coupled to the Denny-Jaffe reagent (a cleavable radioactive photoaffinity cross-linker) was allowed to bind to the Ca2+ pump. After illumination to couple the cross-linker to the pump, the cleavable bond was split and the calmodulin removed, leaving the pump radioactively labeled. This pump was digested with chymotrypsin, and the products were separated by gel permeation chromatography. The only radioactive peak (migrating at about 12 kDa) was further purified on reverse-phase high pressure liquid chromatography (HPLC). Amino acid analysis showed the fragment to have a minimal molecular mass of 12.4 kDa and to contain a single methionine. After attempts to sequence the peptide directly failed. CNBr digestion was carried out on the labeled ATPase, producing both soluble and insoluble labeled material. After reverse-phase HPLC purification of the soluble material, a single radioactive peak was collected. Its sequence was (Formula: see text). A portion of this peak was passed through a microcalmodulin column; it bound in the presence of Ca2+ and was eluted by EDTA, and by a mixture of EDTA and urea. Staphylococcal V8 protease digestion of the eluted peak produced the same sequence as shown above, but starting at Leu-2 and ending at Glu-32. Structural analysis of this peptide showed that it shares features with the calmodulin binding domains of other enzymes which are regulated by calmodulin.

Systemic embolization from thrombus in normal left ventricles

It is extremely rare for a thrombus to form in a normal functioning left ventricle. We present two patients in whom this occurred without any plausable explanation. In both instances the patients presented with systemic emboli and had no heart disease or hypercoagulable state. The diagnosis was made by two-dimensional echocardiography and subsequently confirmed during surgery.

Mechanisms involved in ornithine decarboxylase induction by 12-O-tetradecanoylphorbol-13-acetate, a potent mouse skin tumor promoter and an activator of protein kinase C

ODC, the first enzyme in mammalian polyamine biosynthesis, is rapidly induced in response to a wide variety of growth stimuli. However, there is no single mechanism which may explain the rapid turnover of ODC activity. ODC activity has been shown to be regulated at the level of synthesis and degradation, and also by post-translational modifications and an interaction with macromolecules. Our results indicate that TPA-induced ODC activity is regulated at the transcriptional level. An initial signal in ODC induction by TPA is not clear. We have suggested that TPA-increased accumulation of epidermal prostaglandins is required, but not sufficient, for ODC induction by TPA. Others have suggested the role of lipoxygenase product(s) in ODC induction. The role of the microtubule-containing system in regulation of ODC induction has been shown. The involvement of cyclic nucleotides in ODC induction by TPA is controversial. Also, generation of free radicals appears to be involved in ODC induction by TPA. Data summarized in this chapter indicate that activation of PKC may be an initial step in ODC induction by TPA.

Inhibition of both stage I and stage II mouse skin tumour promotion by retinoic acid and the dependence of inhibition of tumor promotion on the duration of retinoic acid treatment

Retinoic acid is a potent inhibitor of mouse skin tumor promotion by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). We have further evaluated the effect of retinoic acid on the stages of tumor promotion and also analyzed the effect of duration of retinoic acid treatment on mouse skin tumor promotion by TPA. In a number of independent experiments, either with female CD-1 or SENCAR mice, we failed to observe a specificity of inhibition by retinoic acid of either Stage I or Stage II tumor promotion. In a typical experiment with SENCAR mice, application of 34 nmol of retinoic acid concurrently with each application of either TPA (3.2 nmol) or mezerein (3.2 nmol) to initiated (with 10 nmol 7,12-dimethylbenz(a)anthracene) skin equally inhibited promotion of skin papilloma formation. Furthermore, sustained inhibition of tumor promotion by retinoic acid required a continuous application of retinoic acid in conjunction with each promotional treatment with TPA; if retinoic acid treatment was discontinued, TPA treatment elicited tumor formation. These results indicate: (a) retinoic acid inhibits both Stage I and Stage II of tumor promotion; and (b) inhibition of tumor promotion exhibits retinoic acid dependency.

Heteroarotinoids. Synthesis, characterization, and biological activity in terms of an assessment of these systems to inhibit the induction of ornithine decarboxylase activity and to induce terminal differentiation of HL-60 cells

The synthesis of certain heteroarotinoids has been achieved, namely the systems (2E,4E,6E)-3,7-dimethyl-7-(1,2,3,4-tetrahydro-4,4-dimethyl-6 -thiochromanyl)-2,4,6-heptatrienoic acid (1a), ethyl (2E,4E,6E)-3,7-dimethyl-7- (1,2,3,4-teterahydro-4,4-dimethyl-6-thiochromanyl)-2,4,6- heptatrienoate (1b), (2E,4E,6E)-3,7-dimethyl-7-(1,2,3,4-tetrahydro-4,4-dimethyl-6 -chromanyl)-2,4,6-heptatrienoic acid (1c), 2-phthalimidoethyl 3,7-dimethyl-7-(1,2,3,4-tetrahydro-4 4-dimethyl-6-thiochromanyl)-2,4,6-heptatrienoate (1d), methyl (E)-p-[2-(4,4- dimethyl-6-chromanyl)-1-propenyl]benzoate (2a), (E)-p-[2-(4,4-dimethyl-6-chromanyl)-1-propenyl]benzyl alcohol (2b), (E)-p-[2-(4,4-dimethyl-6-chromanyl)-1-propenyl]benzonitrile (2c), (E)-p-[2-(4,4-dimethyl-6-chromanyl)-1-propenyl]benzaldehyde (2d), methyl 4-[2-(2,3-dihydro-3,3-dimethyl-5-benzofuranyl)-1-propenyl] benzoate (3a), and (E)-p-[2-(2,3-dihydro-3,3-dimethyl-5-benzofuranyl)-1- propenyl]benzoic acid (3b). Characterization via elemental, IR, 1H NMR, and 13C NMR analyses was completed for these heterocycles. The biological activity of these heteroarotinoids was assayed by either the suppression of the 12-O-tetradecanoylphorbol 13-acetate (TPA) induced synthesis of ornithine decarboxylase (ODC) in mouse skin or the induction of differentiation of human (HL-60) promyelocytic cells. In the ODC assay, systems 1a-c exhibited strong activity (within 10% of or less than the control) whereas alcohols 2b and 3a showed good activity (within 50% of the control) as compared to either 13-cis-retinoic acid or trans-retinoic acid. Moderate activity was observed with 2a and 2b while 1d and 2c were essentially inactive. With the HL-60 assay, 1a and 1c were approximately 2- and 5-fold less active, respectively, than trans-retinoic acid. In contrast, 2a, 3a, and 3b induced differentiation of only a very small percentage of the cells. Acids 1a and 1c were the most active heteroarotinoids in the two biological assays. Consequently, the presence of the heteroatom does not eradicate the activity of the heteroarotinoids and thus they may have potential as chemotherapeutic agents.

Regulation of ornithine decarboxylase gene expression in mouse epidermis and epidermal tumors during two-stage tumorigenesis

Topical treatment of mouse skin with the potent tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) results in an array of biochemical alterations, one of the earliest being a more than 200-fold transient induction of epidermal ornithine decarboxylase (ODC) activity. There is an excellent correlation between the induction of epidermal ODC activity and changes in the level of immunoreactive ODC protein following a single TPA treatment to skin. Both ODC activity and protein levels peak at 4.5 h after TPA treatment and rapidly fall to basal levels by 24 h. Cycloheximide treatment of mice in which ODC had been previously induced by TPA indicated a similar rapid turnover of both ODC catalytic activity and protein levels. Northern blot analysis of polyadenylated RNA isolated from mouse epidermis after a single TPA treatment revealed the stimulation of one species of ODC mRNA of 2.0 kilobases with a maximum at 3.5 h declining by 16 h. The same-sized species of ODC mRNA was detected 4.5 h after multiple biweekly treatments with TPA as well as in mouse papillomas and carcinomas not treated with TPA for at least 1 week. Southern blot analysis of EcoRI or BamHI digests of DNA derived from mouse liver, papillomas, or carcinomas revealed no ODC gene amplification or rearrangement during neoplastic progression. These observations indicate that the induction of epidermal ODC activity following TPA treatment results in a transient increase in the steady state levels of ODC mRNA and in the rate of synthesis of ODC protein, in contrast to epidermal tumors where the levels of ODC mRNA and protein are constitutively elevated.

Mouse skin tumor promoting activity of orange peel oil and d-limonene: a re-evaluation

Orange peel oil has previously been shown to be a promoter of mouse skin tumors. It has been assumed that this activity is due to its major (95%) constituent, d-limonene. We have tested both orange peel oil and purified d-limonene as skin tumor promoters in a two-stage skin carcinogenesis model in which tumors were initiated with 7,12-dimethylbenz[a]-anthracene. We confirmed that topically applied orange peel oil is a very weak promoter of both skin papillomas and carcinomas. However, this promotional activity could not be accounted for by topically applied d-limonene. We thus feel that one or more minor components of orange peel oil has promotional activity. Neither orange peel oil nor d-limonene had promotional activity when given via the diet.