MTHFD2 and cancer: One potential explanation for the effective killing with MTHFD2 RNAi but not with CRISPR‐Cas9 could be that cancer cells acutely rely on MTHFD2 to generate thymidine, but easily switch to use the SHMT1 pathway, allowing the clones to survive long term as in the case of CRISPR‐Cas9 KO cells.