SHMT2 inhibition disrupts the TCF3 transcriptional survival program in Burkitt lymphoma.

Burkitt lymphoma (BL) is an aggressive lymphoma type that is currently treated by intensive chemoimmunotherapy. Despite the favorable clinical outcome of the majority of BL patients, chemotherapy-related toxicity and disease relapse remain as major clinical challenges, emphasizing the need for innovative therapies. Using genome-scale CRISPR-Cas9 screens, we identified B-cell receptor (BCR) signaling, specific transcriptional regulators and one-carbon metabolism as vulnerabilities in BL. We focused on serine hydroxymethyltransferase 2 (SHMT2), a key enzyme in one-carbon metabolism. Inhibition of SHMT2 by either knockdown or pharmacological compounds induced anti-BL effects in vitro and in vivo. Mechanistically, SHMT2 inhibition led to a significant reduction of intracellular glycine and formate levels, which inhibited the mTOR pathway and thereby triggered autophagic degradation of the oncogenic transcription factor TCF3. As a consequence, this led to a collapse of tonic B-cell receptor signaling, which is controlled by TCF3 and is essential for BL cell survival. In terms of clinical translation, we furthermore identified drugs such as methotrexate that synergized with SHMT inhibitors (SHMT2i). Overall, our study has uncovered the dependency landscape in BL, identified and validated SHMT2 as a drug target and revealed a mechanistic link between SHMT2 and the transcriptional master regulator TCF3, opening up new perspectives for innovative therapies.