TGFBR2 and cancer: TRIM21, as an E3 ubiquitin ligase, has been reported to be involved in the proliferation and metastasis of many malignant tumors by promoting polyubiquitin and proteasome degradation pathways.[50, 51] In this study, it was found for the first time that HTR1A interacts with TRIM21 and PSMD7, promotes the ubiquitin‐proteasome degradation pathway of TβRII and inhibits downstream signaling pathways.