Abstract
Colorectal cancer (CRC) remains both common and fatal, and its successful treatment is greatly limited by the development of stem cell‐like characteristics (stemness) and chemoresistance. MiR‐30‐5p has been shown to function as a tumor suppressor by targeting the Wnt/β‐catenin signaling pathway, but its activity in CRC has never been assessed. We hypothesized that miR‐30‐5p exerts anti‐oncogenic effects in CRC by regulating the USP22/Wnt/β‐catenin signaling axis. In the present study, we demonstrate that tissues from CRC patients and human CRC cell lines show significantly decreased miR‐30‐5p family expression. After identifying the 3’UTR of USP22 as a potential binding site of miR‐30‐5p, we constructed a luciferase reporter containing the potential miR‐30‐5p binding site and measured the effects on USP22 expression. Western blot assays showed that miR‐30‐5p decreased USP22 protein expression in HEK293 and Caco2 CRC cells. To evaluate the effects of miR‐30‐5p on CRC cell stemness, we isolated CD133 + CRC cells (Caco2 and HCT15). We then determined that, while miR‐30‐5p is normally decreased in CD133 + CRC cells, miR‐30‐5p overexpression significantly reduces expression of stem cell markers CD133 and Sox2, sphere formation, and cell proliferation. Similarly, we found that miR‐30‐5p expression is normally reduced in 5‐fluorouracil (5‐FU) resistant CRC cells, whereas miR‐30‐5p overexpression in 5‐FU resistant cells reduces sphere formation and cell viability. Inhibition of miR‐30‐5p reversed the process. Finally, we determined that miR‐30‐5p attenuates the expression of Wnt/β‐catenin signaling target genes (Axin2 and MYC), Wnt luciferase activity, and β‐catenin protein levels in CRC stem cells.
Highlights
Colorectal cancer (CRC) is the third most commonly diagnosed cancer in the United States for men and woman, and it remains the second leading cause of cancer‐related death.[1]
We explored the role of microRNA 30‐5p in CRC progression and determined that it inhibits CRC stemness and chemoresistance by negatively regulating the ubiquitin‐specific peptidase 22 (USP22)/Wnt/β‐catenin signaling axis
After determining that miR‐30‐5p expression is reduced in CRC tissues and cell lines, we identified the 3’ untranslated regions (3'UTRs) of USP22 as a binding site of miR‐30‐5p
Summary
Colorectal cancer (CRC) is the third most commonly diagnosed cancer in the United States for men and woman, and it remains the second leading cause of cancer‐related death.[1]. The fluoropyrimidine fluorouracil (5‐FU) is a first‐line adjuvant chemotherapeutic often given as part of a regimen with other cytotoxic drugs including irinotecan,[4] oxaliplatin[5] and leucovorin.[6] Understanding the mechanisms of chemotherapeutic resistance to particular agents is crucial to developing treatment strategies that improve responses to first‐line regimens.[7] In the present study, we explored the role of microRNA 30‐5p (miR‐30‐5p) in CRC progression and determined that it inhibits CRC stemness and chemoresistance by negatively regulating the ubiquitin‐specific peptidase 22 (USP22)/Wnt/β‐catenin signaling axis. In CRC, the Wnt/β‐catenin pathway promotes cancer stem cell (CSC) maintenance, tumorigenesisand chemoresistance.[30,31,32] In the present study, we have determined that miR‐30‐5p targets USP22 and attenuates the Wnt/β‐catenin pathway, thereby negatively regulating CRC stemness and chemoresistance
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