One of the processes that may be occurring is the antagonism of the 5-HT1A and 5-HT1B receptors (Table 1), which, being blocked, may prevent 5-HT from exerting its effects, supporting the anti-tumour mechanism of propranolol, leading to a decrease in the growth/viability of tumour cells by preventing the pro-tumoral action of 5-HT. The gene discussed is HTR1A; the disease is neoplasm.