ARHGEF19 and neoplasm: The functional outcomes in vitro argue for a histological subtype‐specific impact of GRHL3, that is, a tumor‐suppressive effect of GRHL3 in sq‐BLCA and, in contrast, a more oncogenic property in urothelial carcinomas with a putative role of the GRHL3‐EIF4E3 expression axis involving integrin and actin‐associated processes and pathways and factors like ARHGEF19.