Binary combination effects of some pharmacologically active chemicals as promoters of tumorigenesis

Interaction of histamine and other bioamines with cytochromes P450: implications for cell growth modulation and chemopotentiation by drugs

We have characterized microsomal and nuclear histamine sites, designated H(IC), through which this amine acts as an intracellular mediator of platelet aggregation and lymphocyte mitogenesis. A major proportion, at least, of the microsomal H(IC) sites are on cytochromes P450, an important family of microsomal enzymes that are present in all cells, but most abundant in the liver. These enzymes are involved in the metabolism of xenobiotics and natural substrates, including lipid hormones that modulate gene function and cell growth. We have shown that polyamines, hormones (including estrogen, testosterone and progesterone), antihormones (including tamoxifen and flutamide) and various antidepressants and antihistamines, all inhibit histamine binding to P450; we have postulated that, through binding to the heme moiety, intracellular histamine regulates cell function by modulating the catalytic activity of P450 enzymes, an action that may be perturbed by endogenous and exogenous substances. We now demonstrate that, in addition to histamine, melatonin and the biogenic amines dopamine, serotonin and noradrenaline bind to P450 isozymes and to cytochrome C. Thus, heme enzymes in general may represent common targets where multiple bioamines, hormones and drugs interact to influence cell function and growth.

Enhancement of tumor growth by drugs with some common molecular actions

A group of structurally related drugs representing diverse therapeutic classes share, among a number of pharmacological properties, enhancement of tumor growth in several rodent models of malignancy. One common action, the inhibition of histamine binding to and catalytic activity of cytochrome P450 monooxygenases, is highly correlated with potency to enhance tumor growth. Among members of this drug ensemble, the antiestrogen tamoxifen has been shown in controlled clinical studies to increase the incidence of uterine and gastrointestinal cancer and to accelerate the course of gastric cancer, and the tamoxifen analogue clomiphene has been linked to neuroblastoma and the tricyclic group of antidepressants to ovarian cancer. The determination of drug affinities for protein modulators of cell growth, proliferation, and transformation suggests a strategy for identifying at least some classes of chemicals that impart oncologic risks to humans.

Drug-induced immune dysregulation as a cause of atypical cutaneous lymphoid infiltrates: a hypothesis

The authors encountered 22 patients in whom a skin biopsy showed atypical lymphoid hyperplasia and in whom a subsequent drug history showed indigestion of one or more agents before lesional onset. In 13 patients, the biopsy had been performed to rule out a diagnosis of malignant lymphoma, whereas the other nine the clinical impression was that of a drug eruption. Among the more frequently prescribed agents were calcium-channel blockers, angiotensin-converting enzyme (ACE) inhibitors, antidepressants, antihistamines, beta-blockers, benzodiazepines and lipid-lowering agents, all of which are either known to perturb lymphocyte function or have been implicated as a cause of pseudolymphomata. Twelve of the patients were on two or more of these drugs. The effect of drug modulation on the clinical course was assessed. The clinical presentations were as one or more erythematous plaques or multiple infiltrative papules, or as solitary nodules. The patient had been on one or more of the aforementioned drugs from 2 weeks to 5 years before developing the lesions. Resolution of the eruptions occurred in 17 patients within 1 to 32 weeks (mean, 7 weeks) of discontinuing the medication. Five additional patients had complete excision of solitary lesions without recurrence. A history of atopy, autoimmune disease, or previous carcinoma was elicited in five patients. All biopsy specimens showed atypical lymphoid infiltrates, which assumed one or more of the following patterns: mycosis fungoides (MF)-like, a lymphomatoid vascular reaction, lymphocytoma cutis and follicular mucinosis. Based on the histopathology of the biopsied lesions and the clinical course being one of lesional resolution after cessation of drug therapy or excision of a solitary lesion without subsequent recurrence, a diagnosis of drug-associated lymphomatoid hypersensitivity was established in all specimens. A diagnosis of drug-associated pseudolymphoma should be excluded before a diagnosis of cutaneous lymphoma is rendered, and should be considered if the patient is on a drug known to alter lymphocyte function, particularly in the setting of systemic immune dysregulation or multidrug therapy where agent may act synergistically or cumulatively to alter lymphoid function. The authors postulate that the drug may promote an aberrant immune response to an antigen that may be the drug itself or some other stimulus. A skin biopsy may be particularly helpful, as the lesions of drug-associated pseudolymphoma have a morphology distinctive from malignant lymphoma.

Drugs with antihistaminic properties as a cause of atypical cutaneous lymphoid hyperplasia

BACKGROUND

Although an association between antihistaminic drugs and atypical cutaneous lymphoid infiltrates has not been reported previously, in vitro evidence suggests that these agents perturb certain lymphoid functions through binding to histamine receptors, including a novel growth-promoting intracellular histamine receptor, designated HIC.

OBJECTIVE

We studied the clinical findings and histopathologic findings in 14 patients taking antihistaminic drugs in whom atypical cutaneous lymphoid infiltrates developed.

METHODS

We retrospectively reviewed the clinical and histologic features of these patients' skin lesions.

RESULTS

The clinical presentations included solitary or multiple nodules and plaques, and multiple papules. In some patients a temporal association between drug therapy and clinical course was observed, as the lesions improved or resolved after a decrease or discontinuation of the drug. Eleven patients were taking two or more medications that in vitro are associated with alterations in lymphocyte function, including agents without antihistaminic properties. A diagnosis of pseudolymphoma seemed clinically apposite in seven of the 14 patients on the basis of either resolution of the eruption or presentation of a solitary nodule that did not recur after excision. Histologic analysis showed four distinct morphologies: mycosis fungoides-like, nodular dermal infiltrates consistent with either lymphocytoma cutis or lymphoma cutis, lymphomatoid vascular reaction, and follicular mucinosis. Common to cases showing the first pattern were histologic features suggesting a delayed-type hypersensitivity reaction, thus enabling their distinction from mycosis fungoides. The infiltrates were predominantly of T-cell phenotype.

CONCLUSION

Antihistamines are associated with atypical lymphoid hyperplasia in some patients. The antihistaminic drug may not be the provocative agent per se; rather, a drug-induced immunodysregulatory state may render an abnormal immune response to some other exogenous antigen. Multidrug therapy with these and other agents known to exert immunomodulatory effects may increase susceptibility to the development of atypical lymphoid hyperplasia and malignant lymphoma.