CCND1 and colorectal carcinoma: Studies have demonstrated that SHMT2 is markedly upregulated in CRC, thereby promoting tumor growth; conversely, SHMT2 knockdown induces G0/G1 phase arrest and reduces the S-phase fraction in CRC cells, accompanied by downregulation of CCND1 and CDK2 expression and upregulation of the inhibitory protein p27 (Cui et al., 2022).