FGF9 and brain neoplasm: Several negatively correlated genes, including FGF9, ARMCX1, PMP22, and ZBTB18 are involved in nervous system functions, such as glial cell growth, axon regeneration, myelin development and brain tumour suppression (Li et al., 2013; Cartoni et al., 2016; Deng et al., 2018; Heng et al., 2022).