AFF4 Predicts the Prognosis of Colorectal Cancer Patients and Suppresses Colorectal Cancer Metastasis Promoting CDH1 Expression.

Introduction: AF4/FMR2 family member 4 (AFF4) is a core component of super elongation complex (SEC) and regulates the transcription elongation of many genes. AFF4 depletion or amplification is associated with multiple cancers, but its role in colorectal cancer (CRC) has not been investigated so far.

Methods: qRT-PCR and Western blot analyzed AFF4 expression in the paired clinical CRC tissues. The patients' overall survival curve was determined using the Kaplan-Meier plotter. experiments, such as cell proliferation, migration, and invasion, were used to preliminarily ascertain the role of AFF4 in CRC. A CRC cell liver metastasis animal model was well established. Livers were harvested and examined histologically by a series of indicators, such as tumor nodules, liver weight, ALT/AST activity, and tumor cell identification by hematoxylin-eosin (HE) staining.

Results: We firstly examined the expression of AFF4 in colorectal cancer and normal tissues by collecting paired CRC tissues and adjacent normal tissues, revealing that AFF4 was significantly downregulated in CRC patients and lower expression of AFF4 was correlated with poor prognosis. Next, we observed that presence or absence of AFF4 in CRC cells had no effect on cancer cell proliferation, while AFF4 depletion significantly promoted the migration or invasion of CRC cells . Furthermore, we confirmed that AFF4 deficiency enhanced the metastatic capacity of CRC cells . Mechanistically, we found that AFF4 upregulated the transcription of gene, which encodes E-cadherin and suppresses the epithelial-mesenchymal transition (EMT). Knockdown of AFF4 interfered with transcription, resulting in downregulation of E-cadherin expression and the progression of CRC. Moreover, restored expression could rescue the phenotype of CRC cells without AFF4.

Conclusions: Collectively, our data demonstrated that AFF4 served as a significant novel regulator of CRC transcriptional regulation and a potential effective therapy target for patients with CRC.