Metabolic enzymes and pathways have emerged as important enablers of cellular acquisition of the hallmarks of cancer.4 Two previous studies have shown that SHMT1 is necessary for lung tumor growth.27, 28 Additionally, polymorphisms in the SHMT1 gene have been shown to be associated with a wide variety of cancers, including childhood acute lymphoblastic leukemia, non-Hodgkins lymphoma, head and neck cancers, and colon cancer.29, 30, 31, 32 In this study, we identified SHMT1 as a new regulator of ovarian cancer tumor growth and progression. Here, SHMT1 is linked to head and neck cancer.