Increased histidine decarboxylase (HDC) activity in human colorectal cancer: results of a study on ten patients.

Following numerous reports of high histidine decarboxylase (HDC) activity in tumour-bearing animals, the present work was designed to determine the activity of this enzyme in normal and tumour tissues in a series of ten surgical patients with colorectal carcinoma. Significantly increased HDC activity, almost double that of normal tissues, was found in specimens from extirpated human tumours. These results, obtained under reliable sampling and measurement conditions indicated that changes in the enzymic activity of HDC may have a significant role in the development of colorectal tumour cells. Inhibition of the enzyme activity in human cancer subjects may retard or impede tumour growth and perhaps limit the spread of metastases.