DNA-dependent protein kinase plays a central role in transformation of breast epithelial cells following alkylation damage

Abstract

DNA alkylating agents form the first line of cancer chemotherapy. They not only kill cells but also behave as potential carcinogens. MNU, a DNA methylating agent, is well known to induce mammary tumours in rodents. However, the mechanism of tumorigenesis is not well understood. Our study reports a novel role played by DNA-dependent protein kinase (DNA-PK) in methylation damage-induced transformation using three-dimensional breast acinar cultures. Here, we report that exposure of breast epithelial cells to MNU inhibited polarisation at the basolateral domain, increased dispersal of the Golgi at the apical domain and induced an epithelial-to-mesenchymal transition (EMT)-like phenotype as well as invasion. This altered Golgi phenotype correlated with impaired intracellular trafficking. Inhibition of DNA-PK resulted in almost complete reversal of the altered Golgi phenotype and partial rescue of the polarity defect and EMT-like phenotype. The results confirm that methylation damage-induced activation of DNA-PK is a major mechanism in mediating cellular transformation.This article has an associated First Person interview with the first author of the paper.

<p>DNA-PKcs Mediates An Epithelial-Mesenchymal Transition Process Promoting Cutaneous Squamous Cell Carcinoma Invasion And Metastasis By Targeting The TGF-β1/Smad Signaling Pathway</p>

“…Our findings suggested that DNA-PKcs played an important role in cSCC progression because DNA-PKcs promoted cSCC cell migration and invasion. Moreover, similar to the findings of L. Anandi,26 DNA-PKcs expression in the human cSCC SCL-1 cell line was correlated with EMT, indicating that DNA-PKcs facilitates EMT and participates in the processes of cSCC progression and metastasis. This finding is supported by the observation that DNA-PKcs deficiency decreased SCL-1 cell migration and invasion in vitro.…”

DNA-PK: A Perpetrator in Disguise

“…This result was in concordance with the data collected by van de Vijver et al [32] and Sotiriou et al [33]. Our study illustrates for the first time the role of DNA-PK in breast tumorigenesis [15]. In our study, MNU was used to induce DNA-damage, which in turn resulted in activation of DNA-PKcs which eventually resulted in transformation of non-tumorigenic breast epithelial cells.…”

“…This report also claimed that tumor formation was independent of the H-ras mutation initially identified by Zarbl et al [7] Given the extent of exposure to DNA damaging agents in everyday life, and lack of knowledge about the precise mechanism of tumorigenesis following DNA damage; the study of the mechanism of DNA damage induced transformation becomes imperative. In a recent study, using the 3-dimensional breast acinar model, we demonstrated that alkylation damage induced cellular transformation, which was mediated via the activation of DNA-PK, a protein involved in the DNA repair process [15]. DNA-PK has been demonstrated in various studies to have diverse functions [16].…”

Development of Animal Models for Lens and Corneal Diseases Using N-Methyl-N-Nitrosourea

“…Previous studies have shown that MNU induces epithelial-mesenchymal transition (EMT)-like phenotype changes in ocular and breast epithelial cells. 97,98 These changes are mediated by methylation damage-induced activation of DNA-dependent protein kinase (DNA-PK). 99 EMT is central to fibrotic posterior capsule opacification in cases of anterior subcapsular cataract and posterior polar cataract.…”