Histamine formation and tumor growth

Repurposing drugs in oncology (ReDO)-cimetidine as an anti-cancer agent

Cimetidine, the first H₂ receptor antagonist in widespread clinical use, has anti-cancer properties that have been elucidated in a broad range of pre-clinical and clinical studies for a number of different cancer types. These data are summarised and discussed in relation to a number of distinct mechanisms of action. Based on the evidence presented, it is proposed that cimetidine would synergise with a range of other drugs, including existing chemotherapeutics, and that further exploration of the potential of cimetidine as an anti-cancer therapeutic is warranted. Furthermore, there is compelling evidence that cimetidine administration during the peri-operative period may provide a survival benefit in some cancers. A number of possible combinations with other drugs are discussed in the supplementary material accompanying this paper.

Histamine synthesis and content in benign and malignant breast tumours. Its effects on other host tissues

We studied 100 patients: 40 with breast cancer, 41 with benign breast tumours and 19 non-cancer-bearing cholecystectomy patients, in order to measure the histidine decarboxylase activity and histamine content in benign and malignant breast tumours, and to determine whether the histamine metabolism affected skin and muscle tissue distant from the tumour. The HDC-activity of cancerous tissue was significantly higher (P < 0.01) than that registered in the healthy mammary gland tissue of the same patient, being even more pronounced in benign tumour tissue (P < 0.001). However, the histamine content was found to be significantly lower (P < 0.01) in malignant tumours, but higher in benign tumoural tissue as compared with the healthy tissue of the same patient. We also found that the histamine content in muscle tissue was significantly higher in cancer patients than in non-cancer patients. These findings highlight the fact that intracellular histamine metabolism varies in benign and malignant tumours, and that high histamine synthesis of malignant tumours affects other host tissue.

Identification and measurement of acid (specific) histidine decarboxylase activity in rabbit gastric mucosa: ending an old controversy?

One of the main obstacles in assigning any distinct function to histamine in health and disease was the longlasting controversy on the existence of any physiological, endogenous histamine formation in man and most of the other mammals except the rat. Using a modification of Schayer's isotope dilution method, a renewed attempt was made to identify the very low activities of an acid (specific) histidine decarboxylase in rabbit gastric mucosa capable of producing endogenous histamine in physiological conditions, to develop tests for its identification in crude enzyme extracts and to demonstrate the specificity of the enzymatic assay by excluding any relevant Dopa decarboxylase activity and also nonenzymatic decarboxylation interfering with the determination of acid (specific) histidine decarboxylase. To achieve this aim five tests were developed: In the pH profile (test 1), a pH optimum was found at 7.0 in the presence of a low substrate concentration (1.6 X 10(-6)M L-[ring-2-14C]-histidine). The apparent Michaelis concentration at the pH optimum (test 2) was 1.8 X 10(-4)M, the maximum rate 12.5pmol [14C]histamine formed X min-1. To increase the specificity of inhibition experiments with alpha-methylhistidine and alpha-methyl-L-Dopa a pH profile was determined in the presence of these two enzymatic inhibitors (test 3 and 4). alpha-Methylhistidine was used for a reliable diagnostic confirmation test, alpha-methyl-L-Dopa for a reliable exclusion test. Benzene showed no influence on either blanks or recovery rates, but inhibited the enzymic activity at pH 7.0, not however that of unspecific histidine decarboxylase and hence was very valuable as an additional diagnostic exclusion test (test 5). Although these new tests identifying acid (specific) histidine decarboxylase and demonstrating the specificity of its determination were tedious, despite the use of the modified isotope dilution method, they excluded the presence of any Dopa decarboxylase activity in mixtures with crude enzyme preparations as well as of any kind of nonspecific and nonenzymatic histidine decarboxylation. An endogenous histidine decarboxylase in rabbit gastric mucosa is postulated, capable of forming histamine in vivo.

Selective increased tissue histamine levels in tumour-bearing rodents

Histamine levels increased in the fundus of mice bearing a primary 3-methylcholanthrene-induced fibrosarcoma, and in the ventral skin, skeletal muscle and rumen of rats bearing a D.M.B.A. induced mammary adenocarcinoma; they did not increase in the tissues of mice bearing a McC3-1 fibrosarcoma (38th passage) or a Lewis lung carcinoma before the appearance of metastasis, but an increase in histamine levels was observed in dorsal skin, ventral skin and fundus, after the appearance of metastasis.