H1 and H2 histamine receptors in human mammary carcinomas

We previously reported the presence of H₁ and H₂ histamine receptors in an experimental mammary carcinoma induced in rats. Experiments carried outin vivo andin vitro indicate that by acting on these receptors, histamine and antagonists modulate tumor growth. In the present study, binding experiments were performed with human breast cancer biopsies. All the tumors examined exhibited specific binding sites for histamine. Some of them showed the high and low affinity double site previously characterized in the experimental carcinoma. The high affinity site Kd=18±6 nM, 50±33 fm/mg, exhibits H₂ binding characteristics while the low affinity one, Kd=54±22 nM and 217±173 fm/mg, corresponds to an H₁ receptor, Approximately 30% of the tumors studied were negative for H₂ receptors while all of them showed specific binding for ³H]-mepyramine. These data suggest that histamine may regulate cell growth in a high proportion of human mammary carcinomas, offering possibilities for new therapeutic alternatives.