L1TD1 and cancer: Our findings are in contrast to the negative effect of L1TD1 on cell viability and tumor growth observed in the NSCLC xenograft model (Altenberger et al., 2017), but in accordance with the findings that L1TD1 has a positive impact on cell viability in seminoma (Närvä et al., 2012) and medullablastoma (Santos et al., 2015), suggesting a cancer cell type-specific effect of L1TD1 that might be related to the DNA methylation state of the tumors.