The DNA-dependent protein kinase catalytic subunit (DNA-PKcs) plays a major role in DNA damage signaling and repair and is also frequently overexpressed in tumor metastasis. We used isogenic cell lines expressing different levels of DNA-PKcs to investigate the role of DNA-PKcs in metastatic development. We found that DNA-PKcs participates in melanoma primary tumor and metastasis development by stimulating angiogenesis, migration and invasion. Comparison of conditioned medium content from DNA-PKcs-proficient and deficient cells reveals that DNA-PKcs controls secretion of at least 103 proteins (including 44 metastasis-associated with FBLN1, SERPINA3, MMP-8, HSPG2 and the inhibitors of matrix metalloproteinases, such as α-2M and TIMP-2). High throughput analysis of secretomes, proteomes and transcriptomes, indicate that DNA-PKcs regulates the secretion of 85 proteins without affecting their gene expression. Our data demonstrate that DNA-PKcs has a pro-metastatic activity via the modification of the tumor microenvironment. This study shows for the first time a direct link between DNA damage repair and cancer metastasis and highlights the importance of DNA-PKcs as a potential target for anti-metastatic treatment.
Keywords: CM, conditioned media; DNA damage; DNA-PK; DNA-PK, DNA-dependent protein kinase; DNA-PKcs, DNA-PK catalytic subunit; DSB, double-strand break; ECM, extracellular matrix; MMP inhibition; MMP, matrix metalloproteinase; MS, mass spectrometry; NHEJ, non-homologous end joining; SILAC, stable isotope labeling by amino acids in cell culture; TIMP, tissue inhibitor of metalloproteinase.; metastasis; secretion; α-2M, α-2-macroglobulin.