HTR2A and neoplasm: Although knockdown of 5-HT2A had a small effect in reducing the size of otherwise wild-type eye discs (Fig. 4G, quantified in 4Q), the knockdown of these genes did not reduce tumour size and, in fact, knockdown of 5-HT7 slightly increased tumour size (Fig. 4D,F,H,J,L, quantified in 4Q).