Cdt1 overexpression drives colorectal carcinogenesis through origin overlicensing and DNA damage

Abstract

Chromatin licensing and DNA replication factor 1 (CDT1), a protein of the pre-replicative complex, is essential for loading the minichromosome maintenance complex (MCM) helicases onto the origins of DNA replication. While several studies have shown that dysregulation of CDT1 expression causes re-replication and DNA damage in cell lines, and CDT1 is highly expressed in several human cancers, whether CDT1 deregulation is sufficient to enhance tumorigenesis in vivo is currently unclear. To delineate its role in vivo, we overexpressed Cdt1 in the mouse colon and induced carcinogenesis using azoxymethane/dextran sodium sulfate (AOM/DSS). Here, we show that mice overexpressing Cdt1 develop a significantly higher number of tumors with increased tumor size, and more severe dysplastic changes (high-grade dysplasia), compared with control mice under the same treatment. These tumors exhibited an increased growth rate, while cells overexpressing Cdt1 loaded greater amounts of Mcm2 onto chromatin, demonstrating origin overlicensing. Adenomas overexpressing Cdt1 showed activation of the DNA damage response (DDR), apoptosis, formation of micronuclei, and chromosome segregation errors, indicating that aberrant expression of Cdt1 results in increased genomic and chromosomal instability in vivo, favoring cancer development. In line with these results, high-level expression of CDT1 in human colorectal cancer tissue specimens and colorectal cancer cell lines correlated significantly with increased origin licensing, activation of the DDR, and microsatellite instability (MSI).

CDT1 drives replication overlicensing and enhances tumorigenesis in the gut†

“…Adenomas overexpressing CDT1 demonstrated activation of the DNA damage response, apoptosis, formation of micronuclei, and chromosome segregation errors, indicating that aberrant CDT1 expression resulted in increased genomic and chromosomal instability in vivo. Conditional mice did not exhibit overt metastases in the liver or lungs, consistent with observations that AOM/DSS-driven tumorigenesis is not metastatic [7].…”

“…In conclusion, the elegant study by Petropoulos and colleagues [7] demonstrates the pathogenic significance of CDT1 in intestinal tumorigenesis and suggests the potential prognostic value of CDT1 in this neoplasia.…”

“…In a recent paper published in the Journal of Pathology , Petropoulos and colleagues assessed whether CDT1 hyperactivity enhanced intestinal tumorigenesis [7] (Figure 1). The authors generated mice overexpressing CDT1 and/or lacking Geminin selectively in the intestinal epithelium.…”

“…The paper contained no information on the spontaneous tumoral phenotype in those animals, even though it is conceivable that compensatory pathways attenuate the consequences of CDT1 hyperactivity in normal conditions, thereby preventing the development of tumors. However, following exposure to various cycles of azoxymethane (AOM), a carcinogen and gene mutation agent, and dextran sodium sulfate (DSS), a polymer of sulfated polysaccharide that causes acute colonic injury by hyperosmotic damage to epithelial cells [8], mice overexpressing CDT1 and/or lacking Geminin exhibited increased tumorigenesis, substantiated by the higher number of adenomas with increased size, more severe dysplastic changes, and reduced survival as compared to wild‐type mice receiving the same treatment [7]. The severity of pathology in CDT1‐overexpressing mice was not exacerbated by concomitant Geminin deficiency, indicating that the CDT1 overexpression‐mediated pro‐tumorigenic effect could not be adequately controlled by the constitutive levels of Geminin.…”

RAD51 restricts DNA over-replication from re-activated origins

“…In mice, overexpression of CDC6 and CDT1 causes over-replication in precursor stem cells, leading to lethal tissue dysplasia (Muñoz et al, 2017 ). DNA over-replication has also been linked to aggressive behavior in cancer cells (Galanos et al, 2016 ; Petropoulos et al, 2023 ).…”