CD44 Suppression Improved the Chemosensitivity of HT-29 Colorectal Cancer Cells to 5-Fluorouracil and Inhibited Cell Migration.

Purpose: CD44 plays a pivotal role through tumorigenesis by regulating cancer cell metastasis, stemness, and chemosensitivity and is considered a promising therapeutic target for human cancers, including colorectal cancer (CRC). Therefore, the present research aimed to examine the simultaneous therapeutic effect of CD44 silencing and 5-fluorouracil (5-FU) on in vitro tumorigenesis of CRC cells.

Methods: CD44 expression was initially evaluated in TCGA datasets and CRC tissues. Furthermore, functional analysis was performed on HT-29 CRC cells overexpressing CD44. The cells were transfected with CD44 siRNA and then treated with 5-FU. Consequently, to explore the combination therapy effect on cell viability, migration, apoptosis, and chromatin fragmentation, we performed MTT assay, scratch assay, Annexin V/PI staining and DAPI staining assays, respectively. The spheroid and colony formation assays were further employed to investigate stemness features. The gene expression at protein and mRNA levels were explored using western blotting and qPCR.

Results: Our findings illustrated that CD44 was significantly overexpressed in CRC tissues compared to normal samples. The suppression of CD44 considerably promoted the chemosensitivity of HT-29 cells to 5-FU by apoptosis induction. Also, the combination therapy led to overexpression of apoptotic genes, including P53, caspase-3, and caspase-9, as well as downregulation of AKT1 expression. Furthermore, CD44 suppression, separately or combined with 5-FU, hindered stemness properties in HT-29 cells via downregulation of Sox2 and Nanog expression. Besides, the combination therapy remarkably downregulated MMPs and suppressed CRC cell migration.

Conclusion: Considering its involvement in chemosensitivity to 5-FU, CD44 could be suggested as a potential target for improving the efficiency of CRC chemotherapy.