INS and neoplasm: These data are further supported by meta-analyses of recurrent endocrine-treated tumours, which showed lower levels of IGF1Rβ compared with pretreated tumours.45,46 Our in vitro results show that insulin signalling is important in endocrine-resistant cells but less relevant to parental (i.e. endocrine sensitive) cells (Figs. 2 and 5).