In the presence of adenine, hypoxanthine, or formate, Ewing sarcoma cells resumed a low level of proliferation despite continuous SHIN1 presence, indicating that within the time frame analyzed, purine availability can only partially reverse the preexisting growth arrest induced by inhibition of one-carbon metabolism at the SHMT level (Fig. 5F). This evidence concerns the gene SHMT1 and Ewing sarcoma.