[A simple bioassay method of urinary indoleacetic acid, a cancer growth factor]

Indoleacetic acid (IAA) is produced in cancer tissue and promotes the growth of cancer cells and of the surrounding cells which become cancerous. It was shown that the urine of cancer patients contains larger amounts of IAA than that of healthy persons (except diabetics). This increased IAA level may be derived from the cancer tissue. The measurement of urinary IAA can thus be used to screen cancer patients. Various assay methods for IAA were tested, but 15 min. are required even with the modified HPLC used in this laboratory directly with unpurified urine. Hence it is unsuitable for measuring large numbers of samples within short period. The present work reports on a simple, easy and rapid method for determining urinary IAA in large numbers of samples by using Avena coleoptile sections. Ten sections are floated for 3 hr. on 1/50 diluted urine with 0.5 ppm gibberellic acid (GA). Up to a certain limit their elongation is proportional to the IAA concentration in the diluted urine. Persons whose urine causes coleptile section to elongate more than 1.3 mm require detailed clinical examination to determine whether or not they suffer from cancer.