Genome-wide expression profiling analysis of Hoxa1-null mouse embryos identified a number of Hoxa1 downstream targets involved in developmental processes [26]; three of the genes downregulated in Hoxa1 null embryos, Met, Smo (smoothened) and Sema3c (semaphorin 3c), are positive regulators of tumor cell migration, invasion and/or growth. Here, SMO is linked to neoplasm.