The inhibition of growth by chemical compounds

Abstract

In an extended investigation of the growth-inhibitory activity of carcinogenic compounds and related substances, over two hundred compounds were tested, including various 5-, 10- and 9:10-substituted benzanthracenes, dimethyl derivatives of anthracene, nitrogenous analogues of 1:2 benzanthracene, benzphenothiazines and dibenzphenothiazines, compounds related to 3:4-benzphenanthrene, dibenzfluorenes, dibenzcarbazoles, dibenzpyrenes, azonaphthalenes and related products, naphthylamines and naphthaquinones, arsenonaphthalenes, derivatives of triphenylethylene, and diphenyl derivatives of indene, $\beta $-$\text{naphthindole}$ and $\beta $-$\text{naphthofuran}$. A striking degree of correspondence was often shown by the inhibitory and carcinogenic activity of closely related compounds (e.g. 5-alkyl benzanthracenes; dibenzfluorenes; dibenzphenanthrenes; $2\colon 2^{\prime}$-$\text{azonaphthalene}$, $2\colon 2^{\prime}$-$\text{diamino-1}$: $1^{\prime}$-$\text{dinaphthyl}$ and 3:4:5:6-dibenzcarbazole). However, no inhibitory activity was observed for certain carcinogenic 10- and 9:10-substituted benzanthracenes. On the other hand, inhibitory activity was noted in a few compounds (e.g. $1\colon 2^{\prime}$-$\text{azonaphthalene)}$ which have yielded few or no tumours in exhaustive tests, and in some of a group of synthetic oestrogenic compounds which, although not carcinogenic in the usual sense, are nevertheless associated with the induction of individual types of tumour under special conditions. The relation between molecular structure and inhibitory activity depends in general upon an optimal degree of molecular complexity and upon certain more specific requirements. Nevertheless, the results obtained with derivatives of triphenylethylene suggest that inhibitory activity may still be shown by compounds diverging widely from the polycyclic structure and possessing only a skeletal resemblance. Diminution of inhibitory effect with increased substituent size was shown in the 5-alkyl benzanthracenes tested, although the same relation does not necessarily obtain for other positions. The influence of the nature of the substituent is seen (for example) in the contrast between 10-methyl-, 10-amino- and 10-cyano-1:2-benzanthracene (inhibitory) and 10-isopropyl-1:2-benzanthracene (inactive). Lastly, numerous experiments indicated that solubilization of an active compound usually entails decrease of activity, although certain apparent exceptions were encountered. In addition to the relationship between inhibitory activity and carcinogenicity, and that between both biological properties and chemical structure, consideration is also given to the mode of production of the inhibitory effect.