It is important to note that all-trans retinoic acid is standard therapy for some types of myeloid leukemias, most notably acute promyelocytic leukemia (APL) an

It is important to note that all-trans retinoic acid is standard therapy for some types of myeloid leukemias, most notably acute promyelocytic leukemia (APL) and it is also routinely used for treatment of neuroblastoma (a pediatric solid tumor). However, in both cases the cancers show an arrest in differentiation, which ATRA helps overcoming, so I am quite skeptical it will be clinically effective in tumors that develop from fully differentiated cells (like gastric cancer does). https://www.lls.org/treatment-acute-promyelocytic-leukemia https://www.lls.org/treatment-acute-promyelocytic-leukemia