The effects of several croton oil constituents on two types of DNA repair and cyclic nucleotide levels in mammalian cells in vitro

The purpose of the present study was to determine the effects of two potent tumor-promoting agents on two DNA repair mechanisms and cyclic nucleotide levels in mammalian cells. Human amnion (AV3) cells were treated with low dose levels of either UV of N-acetoxy-acetylaminofluorene. Subsequently, DNA excision repair as measured by unscheduled DNA synthesis was followed in the absence or presence of non-toxic levels of either 12-O-tetradecanoylphorbol-13-acetate (TPA), phorbol-12,13-dibenzoate (PDB), both potent tumor promoters, or phorbol, a non-promoter. Neither of these compounds inhibited DNA repair synthesis occurring in response to low doses of the carcinogenic agents. In addition, TPA did not inhibit "post-replication repair" in response to UV irradiation of growing Chinese hamster (V79-4) cells. However, both TPA and PDB did cause rapid dramatic increases in cyclic guanosine monophosphate levels in human amnion cells; phorbol had no effect. Neither of these compounds affected cyclic adenosine monophosphate levels. These results are discussed in the light of a possible mechanism of the action of tumor promoters involving "post-replication repair".

Induction of the polyamine-biosynthetic enzymes in mouse epidermis by tumor-promoting agents

A single topical application of 1.0 mg of crotol oil or 17 nmoles of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) resulted in a rapid, transient stimulation of mouse epidermal ornithine decarboxylase activity. The activity reached a peak (230-fold greater than control after TPA) at 4 to 5 hr after croton oil or TPA treatment and returned to control level by 12 hr. The stimulation of S-adenosyl-L-methionine decarboxylase activity was less pronounced, reaching a peak of activity (6- to 7-fold greater than control) at 9 to 12 hr after TPA or croton oil and slowly declining to control level. The stimulation of both enzyme activities was dependent on the dose of TPA applied and correlated well with the promoting ability of these doses on mouse skin. Phorbol, the nonpromoting parent alcohol of TPA, did not affect the enzymes activities. Cycloheximide pretreatment abolished the increase in enzyme activities after TPA application. By measuring the decline of enzyme activity following cycloheximide treatment, enzyme half-lives of 17 and 41 min were obtained for ornithine and S-adenosyl-L-methionine decarboxylase, respectively. 5-Azacytidine pretreatment prevented the stimulation of enzyme activities by TPA, while actinomycin D had no effect. Cordycepin (3'-deoxyadenosine) partially blocked the rise in enzyme activities.

Nonspecific inhibition of DNA repair synthesis by tumor promoters in human diploid fibroblasts damaged with N-acetoxy-2-acetylaminofluorene

The effects of selected tumor-promoting agents and their nonpromoting analogs on DNA repair synthesis were examined in human diploid fibroblasts (WI-38) damaged with N-acetoxy-2-acetylaminofluorene. Over a range of doses, three promoters (croton oil, 12-O-tetradecanoylphorbol-13-acetate, and anthralin) were found to inhibit DNA repair synthesis while their nonpromoting analogs (phorbol and 1,8-dihydroxyanthraquinone) had little effect. Another tumor promoter, phenol, inhibited DNA repair synthesis only at very high concentrations while an analog, 4-nitrophenol, produced inhibition of DNA repair synthesis at molar concentrations at which phenol had no effect. To investigate the specificity of this phenomenon, the effects of these agents on DNA-replicative synthesis, RNA synthesis, protein synthesis, and cell morphology were evaluated. At equimolar concentrations, tumor promoters were found to inhibit DNA-replicative synthesis as effectively as repair synthesis. RNA and protein synthesis were similarly inhibited over the same range of concentrations. Extensive morphological changes, interpreted as evidence of toxicity, were seen at concentrations of promoters that inhibited the macromolecular syntheses studied. The nonpromoting analogs, with the exception of nitrophenol, had little effect on these processes and showed only slight morphological damage. Thus tumor-promoting agents appeared to inhibit a number of macromolecular synthetic events, including DNA repair synthesis. It is suggested that the effect of tumor promoters on DNA repair synthesis is part of a general response to cellular injury rather than a selective response involving a single metabolic pathway. Furthermore, it is unlikely that the inhibition of repair synthesis represents the major mode of action of promoting agents in the carcinogenic process.

Immunologic alterations in patients with prostatic carcinoma

The state of cell-mediated immunity was evaluated in 41 patients with prostatic carcinoma by determining their ability to demonstrate delayed cutaneous hypersensitivity with dinitrochlorobenzene and recall antigens, and to mount an inflammatory response to croton oil, as well as by measuring changes in monocyte chemotactic response. The patients were divided into 2 groups: those with localized disease and those with metastatic carcinoma. Monocyte chemotactic response provides an in vitro quantitative measure of effector cell function and was significantly depressed in the entire group of prostatic cancer patients as compared to non-cancer controls (p less than 0.05). Patients with metastatic carcinoma had a greater defect than those with localized disease (p less than 0.025). After radical prostatectomy a group of patients with localized disease tended to show improvement in monocyte chemotactic response (p less than 0.025). The ability of patients to develop a delayed cutaneous hypersensitivity response was impaired and correlated with the clinical stage of the disease. By using the cutaneous irritant, croton oil, the ability of these cancer patients to mount an inflammatory response was also found to be impaired and showed a close correlation between clinical stage and course of disease. Changes in response to croton oil tended to precede alterations in dinitrochlorobenzene response.

Effects of phorbol myristate acetate on the metabolism and ultrastructure of neutrophils in chronic granulomatous disease

Previous investigations have demonstrated that phorbol myristate acetate (PMA), the active principle of croton oil, stimulates alterations in normal polymorphonuclear leukocytes (PMN) that resemble closely the changes that develop in the cells after phagocytosis of bacteria. The present study has compared the effects of PMA and heat-killed bacteria on the oxygen uptake, glucose oxidation, nitroblue tetrazolium (NBT) reduction, and ultrastructure of normal neutrophils and PMN from six patients with chronic granulomatous disease (CGD). PMA stimulated oxygen consumption, hexose monophosphate shunt activity, and NBT reduction in normal cells but failed to produce similar effects in CGD neutrophils. However, PMA did induce formation of cytoplasmic vacuoles in the CGD cells similar to those observed in normal neutrophils. The results indicate that PMA is a useful nonparticulate agent for distinguishing between normal and CGD neutrophils and for studying basic mechanisms of phagocytosis in normal and abnormal PMN.

Stimulation of cell division by croton oil in blue-green bacteria

The potent tumor-promoting agent croton oil, which has been shown previously to be strongly mitogenic in mammalian cells, stimulates cell division in snake mutants of the blue-green bacterium Agmenellum quadruplicatum.