SHMT1 and cancer: To better correlate the oxidative stress and the reduced activity of SHMT with tumors induced by PLP deficiency and to shed light on their relative contributes, we fed flies with AA and dTMP alone or in combination, finding a complete rescue of both CABs and primary tumors, which further confirmed the role of CABs in 4DP-induced cancers (Fig. 6A-C and S6).